Nephrology

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Nephrology

Nephrology

A human kidney
System	Urinary
Significant diseases	Hypertension, Kidney cancer
Significant tests	Kidney biopsy, Urinalysis
Specialist	Nephrologist
Glossary	Glossary of medicine

Nephrologist

Occupation
Names	Physician
Occupation type	Specialty
Activity sectors	Medicine
Description
Education required	Doctor of Medicine (M.D.) Doctor of Osteopathic medicine (D.O.) Bachelor of Medicine, Bachelor of Surgery (M.B.B.S.) Bachelor of Medicine, Bachelor of Surgery (MBChB)
Fields of employment	Hospitals, Clinics

Nephrology (from Greek nephros "kidney", combined with the suffix -logy, "the study of") is a specialty of adult internal medicine and pediatric medicine that concerns the study of the kidneys, specifically normal kidney function (renal physiology) and kidney disease (renal pathophysiology), the preservation of kidney health, and the treatment of kidney disease, from diet and medication to renal replacement therapy (dialysis and kidney transplantation). The word "renal" is an adjective meaning "relating to the kidneys", and its roots are French or late Latin. Whereas according to some opinions, "renal" and "nephro" should be replaced with "kidney" in scientific writings such as "kidney medicine" (instead of nephrology) or "kidney replacement therapy", other experts have advocated preserving the use of renal and nephro as appropriate including in "nephrology" and "renal replacement therapy", respectively.

Nephrology also studies systemic conditions that affect the kidneys, such as diabetes and autoimmune disease; and systemic diseases that occur as a result of kidney disease, such as renal osteodystrophy and hypertension. A physician who has undertaken additional training and become certified in nephrology is called a nephrologist.

The term "nephrology" was first used in about 1960, according to the French "néphrologie" proposed by Pr. Jean Hamburger in 1953, from the Greek νεφρός / nephrós (kidney). Before then, the specialty was usually referred to as "kidney medicine".

Scope

Nephrology concerns the diagnosis and treatment of kidney diseases, including electrolyte disturbances and hypertension, and the care of those requiring renal replacement therapy, including dialysis and renal transplant patients. The word 'dialysis' is from the mid-19th century: via Latin from the Greek word 'dialusis'; from 'dialuein' (split, separate), from 'dia' (apart) and 'luein' (set free). In other words, dialysis replaces the primary (excretory) function of the kidney, which separates (and removes) excess toxins and water from the blood, placing them in the urine.

Many diseases affecting the kidney are systemic disorders not limited to the organ itself, and may require special treatment. Examples include acquired conditions such as systemic vasculitides (e.g. ANCA vasculitis) and autoimmune diseases (e.g. lupus), as well as congenital or genetic conditions such as polycystic kidney disease.

Patients are referred to nephrology specialists after a urinalysis, for various reasons, such as acute kidney injury, chronic kidney disease, hematuria, proteinuria, kidney stones, hypertension, and disorders of acid/base or electrolytes.

Nephrologist

A nephrologist is a physician who specializes in the care and treatment of kidney disease. Nephrology requires additional training to become an expert with advanced skills. Nephrologists may provide care to people without kidney problems and may work in general/internal medicine, transplant medicine, immunosuppression management, intensive care medicine, clinical pharmacology, perioperative medicine, or pediatric nephrology.

Nephrologists may further sub-specialise in dialysis, kidney transplantation, home therapies (home dialysis), cancer-related kidney diseases (onco-nephrology), structural kidney diseases (uro-nephrology), procedural nephrology or other non-nephrology areas as described above.

Procedures a nephrologist may perform include native kidney and transplant kidney biopsy, dialysis access insertion (temporary vascular access lines, tunnelled vascular access lines, peritoneal dialysis access lines), fistula management (angiographic or surgical fistulogram and plasty), and bone biopsy. Bone biopsies are now unusual.

Training

India

To become a nephrologist in India, one has to complete an MBBS (5 and 1/2 years) degree, followed by an MD/DNB (3 years) either in medicine or paediatrics, followed by a DM/DNB (3 years) course in either nephrology or paediatric nephrology.

Australia and New Zealand

Nephrology training in Australia and New Zealand typically includes completion of a medical degree (Bachelor of Medicine, Bachelor of Surgery: 4–6 years), internship (1 year), Basic Physician Training (3 years minimum), successful completion of the Royal Australasian College of Physicians written and clinical examinations, and Advanced Physician Training in Nephrology (3 years). The training pathway is overseen and accredited by the Royal Australasian College of Physicians, though the application process varies across states. Completion of a post-graduate degree (usually a PhD) in a nephrology research interest (3–4 years) is optional but increasingly common. Finally, many Australian and New Zealand nephrologists participate in career-long professional and personal development through bodies such as the Australian and New Zealand Society of Nephrology and the Transplant Society of Australia and New Zealand.

United Kingdom

In the United Kingdom, nephrology (often called renal medicine) is a subspecialty of general medicine. A nephrologist has completed medical school, foundation year posts (FY1 and FY2) and core medical training (CMT), specialist training (ST) and passed the Membership of the Royal College of Physicians (MRCP) exam before competing for a National Training Number (NTN) in renal medicine. The typical Specialty Training (when they are called a registrar, or an ST) is five years and leads to a Certificate of Completion of Training (CCT) in both renal medicine and general (internal) medicine. In those five years, they usually rotate yearly between hospitals in a region (known as a deanery). They are then accepted on to the Specialist Register of the General Medical Council (GMC). Specialty trainees often interrupt their clinical training to obtain research degrees (MD/PhD). After achieving CCT, the registrar (ST) may apply for a permanent post as Consultant in Renal Medicine. Subsequently, some Consultants practice nephrology alone. Others work in this area, and in Intensive Care (ICU), or General (Internal) or Acute Medicine.

United States

Nephrology training can be accomplished through one of two routes. The first path way is through an internal medicine pathway leading to an Internal Medicine/Nephrology specialty, and sometimes known as "adult nephrology". The second pathway is through Pediatrics leading to a speciality in Pediatric Nephrology. In the United States, after medical school adult nephrologists complete a three-year residency in internal medicine followed by a two-year (or longer) fellowship in nephrology. Complementary to an adult nephrologist, a pediatric nephrologist will complete a three-year pediatric residency after medical school or a four-year Combined Internal Medicine and Pediatrics residency. This is followed by a three-year fellowship in Pediatric Nephrology. Once training is satisfactorily completed, the physician is eligible to take the American Board of Internal Medicine (ABIM) or American Osteopathic Board of Internal Medicine (AOBIM) nephrology examination. Nephrologists must be approved by one of these boards. To be approved, the physician must fulfill the requirements for education and training in nephrology in order to qualify to take the board's examination. If a physician passes the examination, then he or she can become a nephrology specialist. Typically, nephrologists also need two to three years of training in an ACGME or AOA accredited fellowship in nephrology. Nearly all programs train nephrologists in continuous renal replacement therapy; fewer than half in the United States train in the provision of plasmapheresis. Only pediatric trained physicians are able to train in pediatric nephrology, and internal medicine (adult) trained physicians may enter general (adult) nephrology fellowships.

Diagnosis

History and physical examination are central to the diagnostic workup in nephrology. The history typically includes the present illness, family history, general medical history, diet, medication use, drug use and occupation. The physical examination typically includes an assessment of volume state, blood pressure, heart, lungs, peripheral arteries, joints, abdomen and flank. A rash may be relevant too, especially as an indicator of autoimmune disease.

Examination of the urine (urinalysis) allows a direct assessment for possible kidney problems, which may be suggested by appearance of blood in the urine (hematuria), protein in the urine (proteinuria), pus cells in the urine (pyuria) or cancer cells in the urine. A 24-hour urine collection used to be used to quantify daily protein loss (see proteinuria), urine output, creatinine clearance or electrolyte handling by the renal tubules. It is now more common to measure protein loss from a small random sample of urine.

Basic blood tests can be used to check the concentration of hemoglobin, white count, platelets, sodium, potassium, chloride, bicarbonate, urea, creatinine, albumin, calcium, magnesium, phosphate, alkaline phosphatase and parathyroid hormone (PTH) in the blood. All of these may be affected by kidney problems. The serum creatinine concentration is the most important blood test as it is used to estimate the function of the kidney, called the creatinine clearance or estimated glomerular filtration rate (GFR).

It is a good idea for patients with longterm kidney disease to know an up-to-date list of medications, and their latest blood tests, especially the blood creatinine level. In the United Kingdom, blood tests can monitored online by the patient, through a website called RenalPatientView.

More specialized tests can be ordered to discover or link certain systemic diseases to kidney failure such as infections (hepatitis B, hepatitis C), autoimmune conditions (systemic lupus erythematosus, ANCA vasculitis), paraproteinemias (amyloidosis, multiple myeloma) and metabolic diseases (diabetes, cystinosis).

Structural abnormalities of the kidneys are identified with imaging tests. These may include Medical ultrasonography/ultrasound, computed axial tomography (CT), scintigraphy (nuclear medicine), angiography or magnetic resonance imaging (MRI).

In certain circumstances, less invasive testing may not provide a certain diagnosis. Where definitive diagnosis is required, a biopsy of the kidney (renal biopsy) may be performed. This typically involves the insertion, under local anaesthetic and ultrasound or CT guidance, of a core biopsy needle into the kidney to obtain a small sample of kidney tissue. The kidney tissue is then examined under a microscope, allowing direct visualization of the changes occurring within the kidney. Additionally, the pathology may also stage a problem affecting the kidney, allowing some degree of prognostication. In some circumstances, kidney biopsy will also be used to monitor response to treatment and identify early relapse. A transplant kidney biopsy may also be performed to look for rejection of the kidney.

Treatment

Treatments in nephrology can include medications, blood products, surgical interventions (urology, vascular or surgical procedures), renal replacement therapy (dialysis or kidney transplantation) and plasma exchange. Kidney problems can have significant impact on quality and length of life, and so psychological support, health education and advanced care planning play key roles in nephrology.

Chronic kidney disease is typically managed with treatment of causative conditions (such as diabetes), avoidance of substances toxic to the kidneys (nephrotoxins like radiologic contrast and non-steroidal anti-inflammatory drugs), antihypertensives, diet and weight modification and planning for end-stage kidney failure. Impaired kidney function has systemic effects on the body. An erythropoetin stimulating agent (ESA) may be required to ensure adequate production of red blood cells, activated vitamin D supplements and phosphate binders may be required to counteract the effects of kidney failure on bone metabolism, and blood volume and electrolyte disturbance may need correction. Diuretics (such as furosemide) may be used to correct fluid overload, and alkalis (such as sodium bicarbonate) can be used to treat metabolic acidosis.

Auto-immune and inflammatory kidney disease, such as vasculitis or transplant rejection, may be treated with immunosuppression. Commonly used agents are prednisone, mycophenolate, cyclophosphamide, ciclosporin, tacrolimus, everolimus, thymoglobulin and sirolimus. Newer, so-called "biologic drugs" or monoclonal antibodies, are also used in these conditions and include rituximab, basiliximab and eculizumab. Blood products including intravenous immunoglobulin and a process known as plasma exchange can also be employed.

When the kidneys are no longer able to sustain the demands of the body, end-stage kidney failure is said to have occurred. Without renal replacement therapy, death from kidney failure will eventually result. Dialysis is an artificial method of replacing some kidney function to prolong life. Renal transplantation replaces kidney function by inserting into the body a healthier kidney from an organ donor and inducing immunologic tolerance of that organ with immunosuppression. At present, renal transplantation is the most effective treatment for end-stage kidney failure although its worldwide availability is limited by lack of availability of donor organs. Generally speaking, kidneys from living donors are 'better' than those from deceased donors, as they last longer.

Most kidney conditions are chronic conditions and so long term followup with a nephrologist is usually necessary. In the United Kingdom, care may be shared with the patient's primary care physician, called a General Practitioner (GP).

Organizations

The world's first society of nephrology was the French 'Societe de Pathologie Renale'. Its first president was Jean Hamburger, and its first meeting was in Paris in February 1949. In 1959, Hamburger also founded the 'Société de Néphrologie', as a continuation of the older society. The UK's Renal Association was founded in 1950; the second society of nephrologists. Its first president was Arthur Osman and met for the first time, in London, on the 30th of March 1950. The Società di Nefrologia Italiana was founded in 1957 and was the first national society to incorporate the phrase nephrologia (or nephrology) into its name.

The word 'nephrology' appeared for the first time in a conference, on 1–4 September 1960 at the "Premier Congrès International de Néphrologie" in Evian and Geneva, the first meeting of the International Society of Nephrology (ISN, International Society of Nephrology). The first day (1.9.60) was in Geneva and the next three (2–4.9.60) were in Evian, France. The early history of the ISN is described by Robinson and Richet in 2005 and the later history by Barsoum in 2011. The ISN is the largest global society representing medical professionals engaged in advancing kidney care worldwide.

In the US, founded in 1964, the National Kidney Foundation is a national organization representing patients and professionals who treat kidney diseases. Founded in 1966, the American Society of Nephrology (ASN) is the world's largest professional society devoted to the study of kidney disease. The American Nephrology Nurses' Association (ANNA), founded in 1969, promotes excellence in and appreciation of nephrology nursing to make a positive difference for patients with kidney disease. The American Association of Kidney Patients (AAKP) is a non-profit, patient-centric group focused on improving the health and well-being of CKD and dialysis patients. The National Renal Administrators Association (NRAA), founded in 1977, is a national organization that represents and supports the independent and community-based dialysis providers. The American Kidney Fund directly provides financial support to patients in need, as well as participating in health education and prevention efforts. ASDIN (American Society of Diagnostic and Interventional Nephrology) is the main organization of interventional nephrologists. Other organizations include CIDA, VASA etc. which deal with dialysis vascular access. The Renal Support Network (RSN) is a nonprofit, patient-focused, patient-run organization that provides non-medical services to those affected by chronic kidney disease (CKD).

In the United Kingdom, UK National Kidney Federation and Kidney Care UK (previously known as British Kidney Patient Association, BKPA) represent patients, and the Renal Association represents renal physicians and works closely with the National Service Framework for kidney disease.

There is an international office in Brussels, Belgium.

Polycystic kidney disease

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Polycystic_kidney_disease

Polycystic kidney disease
Other names	Kidney - polycystic
Severely affected polycystic kidneys removed at time of transplantation
Specialty	Nephrology
Symptoms	Abdominal pain
Types	ADPKD and ARPKD
Diagnostic method	MRI, CT scan, Ultrasound
Treatment	Antihypertensives, Life style management

Polycystic kidney disease (PKD or PCKD, also known as polycystic kidney syndrome) is a genetic disorder in which the renal tubules become structurally abnormal, resulting in the development and growth of multiple cysts within the kidney. These cysts may begin to develop in utero, in infancy, in childhood, or in adulthood. Cysts are non-functioning tubules filled with fluid pumped into them, which range in size from microscopic to enormous, crushing adjacent normal tubules and eventually rendering them non-functional as well.

PKD is caused by abnormal genes that produce a specific abnormal protein; this protein has an adverse effect on tubule development. PKD is a general term for two types, each having their own pathology and genetic cause: autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD). The abnormal gene exists in all cells in the body; as a result, cysts may occur in the liver, seminal vesicles, and pancreas. This genetic defect can also cause aortic root aneurysms, and aneurysms in the circle of Willis cerebral arteries, which if they rupture, can cause a subarachnoid hemorrhage.

Diagnosis may be suspected from one, some, or all of the following: new onset flank pain or red urine; a positive family history; palpation of enlarged kidneys on physical exam; an incidental finding on abdominal sonogram; or an incidental finding of abnormal kidney function on routine lab work (BUN, serum creatinine, or eGFR). Definitive diagnosis is made by abdominal CT exam.

Complications include hypertension due to the activation of the renin–angiotensin–aldosterone system (RAAS), frequent cyst infections, urinary bleeding, and declining renal function. Hypertension is treated with angiotensin converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs). Infections are treated with antibiotics. Declining renal function is treated with renal replacement therapy (RRT): dialysis and/or transplantation. Management from the time of the suspected or definitive diagnosis is by an appropriately trained doctor.

Signs and symptoms

Signs and symptoms include high blood pressure, headaches, abdominal pain, blood in the urine, and excessive urination. Other symptoms include pain in the back, and cyst formation (renal and other organs).

Cause

PKD is caused by abnormal genes which produce a specific abnormal protein which has an adverse effect on tubule development. PKD is a general term for two types, each having their own pathology and genetic cause: autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD).

Autosomal dominant

Main article: Autosomal dominant polycystic kidney disease

CT scan showing autosomal dominant polycystic kidney disease

Cartoon of autosomal dominant polycystic kidney disease with normal kidney inset to right of diagram

Cartoon of autosomal recessive polycystic kidney disease with normal kidney inset to right of diagram

Autosomal dominant polycystic kidney disease (ADPKD) is the most common of all the inherited cystic kidney diseases with an incidence of 1:500 live births. Studies show that 10% of end-stage kidney disease (ESKD) patients being treated with dialysis in Europe and the U.S. were initially diagnosed and treated for ADPKD.

Genetic mutations in any of the three genes PKD1, PKD2, and PKD3 have similar phenotypical presentations.

• Gene PKD1 is located on chromosome 16 and codes for a protein involved in regulation of cell cycle and intracellular calcium transport in epithelial cells, and is responsible for 85% of the cases of ADPKD.
• Gene PKD2 is identified, using genetic linkage study, on chromosome 4. A group of voltage-linked cation channels, with inward selectivity for K>Na>>Ca and outward selectivity for Ca2+ ≈ Ba2+ > Na+ ≈ K+, are coded for by PKD2 on chromosome 4.
• PKD3 recently appeared in research papers as a postulated third gene. Fewer than 10% of cases of ADPKD appear in non-ADPKD families. Cyst formation begins in utero from any point along the nephron, although fewer than 5% of nephrons are thought to be involved. As the cysts accumulate fluid, they enlarge, separate entirely from the nephron, compress the neighboring kidney parenchyma, and progressively compromise kidney function.

Autosomal recessive

Autosomal recessive polycystic kidney disease (ARPKD) (OMIM #263200) is the less common of the two types of PKD, with an incidence of 1:20,000 live births and is typically identified in the first few weeks after birth. Unfortunately, the kidneys are often underdeveloped resulting in a 30% death rate in newborns with ARPKD. PKHD1 is involved.

Mechanism

PKD1 and PKD2

Both autosomal dominant and autosomal recessive polycystic kidney disease cyst formation are tied to abnormal cilia-mediated signaling. The polycystin-1 and polycystin-2 proteins appear to be involved in both autosomal dominant and recessive polycystic kidney disease due to defects in both proteins. Both proteins have communication with calcium channel proteins, and causes reduction in resting (intracellular) calcium and endoplasmic reticulum storage of calcium.

The disease is characterized by a ‘second hit’ phenomenon, in which a mutated dominant allele is inherited from a parent, with cyst formation occurring only after the normal, wild-type gene sustains a subsequent second genetic ‘hit’, resulting in renal tubular cyst formation and disease progression.

PKD results from defects in the primary cilium, an immotile, hair-like cellular organelle present on the surface of most cells in the body, anchored in the cell body by the basal body. In the kidney, primary cilia have been found to be present on most cells of the nephron, projecting from the apical surface of the renal epithelium into the tubule lumen. The cilia were believed to bend in the urine flow, leading to changes in signalling, however this has since been shown to be an experimental error (the bending of cilia was an artifact of focal plane compensation, and also the actual effect on micturition by severe hypertension and cardiac arrest) and that bending of cilia does not contribute to alterations in Ca flux. While it is not known how defects in the primary cilium lead to cyst development, it is thought to possibly be related to disruption of one of the many signaling pathways regulated by the primary cilium, including intracellular calcium, Wnt/β-catenin, cyclic adenosine monophosphate (cAMP), or planar cell polarity (PCP). Function of the primary cilium is impaired, resulting in disruption of a number of intracellular signaling cascades which produce differentiation of cystic epithelium, increased cell division, increased apoptosis, and loss of resorptive capacity.

Diagnosis

Polycystic kidney disease can be ascertained via a CT scan of abdomen, as well as, an MRI and ultrasound of the same area. A physical exam/test can reveal enlarged liver, heart murmurs and elevated blood pressure

Natural history

Most cases progress to bilateral disease in adulthood.

Treatment

Chr 11 FISH-mapped BACs from CGAP

In 2018, Jynarque (Tolvaptan) was introduced  as the first FDA-approved treatment for PKD. In a recent long-term study, patients using Tolvaptan had a 6.4% higher kidney function after 5 years compared to standard of care. In 2019, a team of researchers at UCSB found that a ketogenic diet might be able to halt, or even reverse progression in mice, and the results of a first human case series study are showing potential benefit. The results of a 3-month randomized, prospective dietary intervention clinical trial are pending. In addition, recent research indicates that mild to moderate calorie restriction or time-restricted feeding  slow the progression of autosomal dominant polycystic kidney disease (ADPKD) in mice.  Patient communities have been combining both ketogenic diets and time-restricted feeding with a low-oxalate diet to prevent the formation of stones and early reports show an average of 17% increase in kidney function after approximately one year on a ketogenic, time-restricted dietary regimen. If and when the disease progresses enough in a given case, the nephrologist or other practitioner and the patient will have to decide what form of renal replacement therapy will be used to treat end-stage kidney disease (kidney failure, typically stage 4 or 5 of chronic kidney disease).

That will either be some form of dialysis, which can be done at least two different ways at varying frequencies and durations (whether it is done at home or in the clinic depends on the method used and the patient's stability and training) and eventually, if they are eligible because of the nature and severity of their condition and if a suitable match can be found, unilateral or bilateral kidney transplantation.

A Cochrane Review study of autosomal dominant polycystic kidney disease made note of the fact that it is important at all times, while avoiding antibiotic resistance, to control infections of the cysts in the kidneys, and if affected, the liver, when needed for a certain duration to combat infection, by using, "bacteriostatic and bacteriocidal drugs".

Prognosis

ADPKD individuals might have a normal life; conversely, ARPKD can cause kidney dysfunction and can lead to kidney failure by the age of 40–60. ADPKD1 and ADPKD2 are very different, in that ADPKD2 is much milder.

Currently, there are no therapies proven effective to prevent the progression of ADPKD.

Epidemiology

PKD is one of the most common hereditary diseases in the United States, affecting more than 600,000 people. It is the cause of nearly 10% of all end-stage renal disease. It equally affects men, women, and all races. PKD occurs in some animals as well as humans.

Forging

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Forging

Hot metal ingot being loaded into a hammer forge

A billet in an open-die forging press

Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die. Forging is often classified according to the temperature at which it is performed: cold forging (a type of cold working), warm forging, or hot forging (a type of hot working). For the latter two, the metal is heated, usually in a forge. Forged parts can range in weight from less than a kilogram to hundreds of metric tons. Forging has been done by smiths for millennia; the traditional products were kitchenware, hardware, hand tools, edged weapons, cymbals, and jewellery.

Since the Industrial Revolution, forged parts are widely used in mechanisms and machines wherever a component requires high strength; such forgings usually require further processing (such as machining) to achieve a finished part. Today, forging is a major worldwide industry.

History

Forging is one of the oldest known metalworking processes. Traditionally, forging was performed by a smith using hammer and anvil, though introducing water power to the production and working of iron in the 12th century allowed the use of large trip hammers or power hammers that increased the amount and size of iron that could be produced and forged. The smithy or forge has evolved over centuries to become a facility with engineered processes, production equipment, tooling, raw materials and products to meet the demands of modern industry.

In modern times, industrial forging is done either with presses or with hammers powered by compressed air, electricity, hydraulics or steam. These hammers may have reciprocating weights in the thousands of pounds. Smaller power hammers, 500 lb (230 kg) or less reciprocating weight, and hydraulic presses are common in art smithies as well. Some steam hammers remain in use, but they became obsolete with the availability of the other, more convenient, power sources.

Advantages and disadvantages

Forging can produce a piece that is stronger than an equivalent cast or machined part. As the metal is shaped during the forging process, its internal grain texture deforms to follow the general shape of the part. As a result, the texture variation is continuous throughout the part, giving rise to a piece with improved strength characteristics. Additionally, forgings can achieve a lower total cost than casting or fabrication. Considering all the costs that are incurred in a product's life cycle from procurement to lead time to rework, and factoring in the costs of scrap, and downtime and other quality considerations, the long-term benefits of forgings can outweigh the short-term cost savings that castings or fabrications might offer.

Some metals may be forged cold, but iron and steel are almost always hot forged. Hot forging prevents the work hardening that would result from cold forming, which would increase the difficulty of performing secondary machining operations on the piece. Also, while work hardening may be desirable in some circumstances, other methods of hardening the piece, such as heat treating, are generally more economical and more controllable. Alloys that are amenable to precipitation hardening, such as most aluminium alloys and titanium, can be hot forged, followed by hardening.

Production forging involves significant capital expenditure for machinery, tooling, facilities and personnel. In the case of hot forging, a high-temperature furnace (sometimes referred to as the forge) is required to heat ingots or billets. Owing to the size of the massive forging hammers and presses and the parts they can produce, as well as the dangers inherent in working with hot metal, a special building is frequently required to house the operation. In the case of drop forging operations, provisions must be made to absorb the shock and vibration generated by the hammer. Most forging operations use metal-forming dies, which must be precisely machined and carefully heat-treated to correctly shape the workpiece, as well as to withstand the tremendous forces involved.

Processes

A cross-section of a forged connecting rod that has been etched to show the grain flow

There are many different kinds of forging processes available; however, they can be grouped into three main classes:

• Drawn out: length increases, cross-section decreases
• Upset: length decreases, cross-section increases
• Squeezed in closed compression dies: produces multidirectional flow

Common forging processes include: roll forging, swaging, cogging, open-die forging, impression-die forging (closed die forging), press forging, cold forging, automatic hot forging and upsetting.

Temperature

Main article: Forging temperature

See also: Hot working and Cold working

All of the following forging processes can be performed at various temperatures; however, they are generally classified by whether the metal temperature is above or below the recrystallization temperature. If the temperature is above the material's recrystallization temperature it is deemed hot forging; if the temperature is below the material's recrystallization temperature but above 30% of the recrystallization temperature (on an absolute scale) it is deemed warm forging; if below 30% of the recrystallization temperature (usually room temperature) then it is deemed cold forging. The main advantage of hot forging is that it can be done more quickly and precisely, and as the metal is deformed work hardening effects are negated by the recrystallization process. Cold forging typically results in work hardening of the piece.

Drop forging

Drop forging is a forging process where a hammer is raised and then "dropped" into the workpiece to deform it according to the shape of the die. There are two types of drop forging: open-die drop forging and impression-die (or closed-die) drop forging. As the names imply, the difference is in the shape of the die, with the former not fully enclosing the workpiece, while the latter does.

Open-die drop forging

Open-die drop forging (with two dies) of an ingot to be further processed into a wheel

A large 80 ton cylinder of hot steel in an open-die forging press, ready for the upsetting phase of forging

Open-die forging is also known as smith forging. In open-die forging, a hammer strikes and deforms the workpiece, which is placed on a stationary anvil. Open-die forging gets its name from the fact that the dies (the surfaces that are in contact with the workpiece) do not enclose the workpiece, allowing it to flow except where contacted by the dies. The operator therefore needs to orient and position the workpiece to get the desired shape. The dies are usually flat in shape, but some have a specially shaped surface for specialized operations. For example, a die may have a round, concave, or convex surface or be a tool to form holes or be a cut-off tool. Open-die forgings can be worked into shapes which include discs, hubs, blocks, shafts (including step shafts or with flanges), sleeves, cylinders, flats, hexes, rounds, plate, and some custom shapes. Open-die forging lends itself to short runs and is appropriate for art smithing and custom work. In some cases, open-die forging may be employed to rough-shape ingots to prepare them for subsequent operations. Open-die forging may also orient the grain to increase strength in the required direction.

Advantages of open-die forging

• Reduced chance of voids
• Better fatigue resistance
• Improved microstructure
• Continuous grain flow
• Finer grain size
• Greater strength
• Better response to thermal treatment
• Improvement of internal quality
• Greater reliability of mechanical properties, ductility and impact resistance

"Cogging" is the successive deformation of a bar along its length using an open-die drop forge. It is commonly used to work a piece of raw material to the proper thickness. Once the proper thickness is achieved the proper width is achieved via "edging". "Edging" is the process of concentrating material using a concave shaped open-die. The process is called "edging" because it is usually carried out on the ends of the workpiece. "Fullering" is a similar process that thins out sections of the forging using a convex shaped die. These processes prepare the workpieces for further forging processes.

• 

  Edging

• 

  Fullering

Impression-die forging

Impression-die forging is also called "closed-die forging". In impression-die forging, the metal is placed in a die resembling a mold, which is attached to an anvil. Usually, the hammer die is shaped as well. The hammer is then dropped on the workpiece, causing the metal to flow and fill the die cavities. The hammer is generally in contact with the workpiece on the scale of milliseconds. Depending on the size and complexity of the part, the hammer may be dropped multiple times in quick succession. Excess metal is squeezed out of the die cavities, forming what is referred to as "flash". The flash cools more rapidly than the rest of the material; this cool metal is stronger than the metal in the die, so it helps prevent more flash from forming. This also forces the metal to completely fill the die cavity. After forging, the flash is removed.

In commercial impression-die forging, the workpiece is usually moved through a series of cavities in a die to get from an ingot to the final form. The first impression is used to distribute the metal into the rough shape in accordance to the needs of later cavities; this impression is called an "edging", "fullering", or "bending" impression. The following cavities are called "blocking" cavities, in which the piece is working into a shape that more closely resembles the final product. These stages usually impart the workpiece with generous bends and large fillets. The final shape is forged in a "final" or "finisher" impression cavity. If there is only a short run of parts to be done, then it may be more economical for the die to lack a final impression cavity and instead machine the final features.

Impression-die forging has been improved in recent years through increased automation which includes induction heating, mechanical feeding, positioning and manipulation, and the direct heat treatment of parts after forging. One variation of impression-die forging is called "flashless forging", or "true closed-die forging". In this type of forging, the die cavities are completely closed, which keeps the workpiece from forming flash. The major advantage to this process is that less metal is lost to flash. Flash can account for 20 to 45% of the starting material. The disadvantages of this process include additional cost due to a more complex die design and the need for better lubrication and workpiece placement.

There are other variations of part formation that integrate impression-die forging. One method incorporates casting a forging preform from liquid metal. The casting is removed after it has solidified, but while still hot. It is then finished in a single cavity die. The flash is trimmed, then the part is quench hardened. Another variation follows the same process as outlined above, except the preform is produced by the spraying deposition of metal droplets into shaped collectors (similar to the Osprey process).

Closed-die forging has a high initial cost due to the creation of dies and required design work to make working die cavities. However, it has low recurring costs for each part, thus forgings become more economical with greater production volume. This is one of the major reasons closed-die forgings are often used in the automotive and tool industries. Another reason forgings are common in these industrial sectors is that forgings generally have about a 20 percent higher strength-to-weight ratio compared to cast or machined parts of the same material.

Design of impression-die forgings and tooling

Forging dies are usually made of high-alloy or tool steel. Dies must be impact- and wear-resistant, maintain strength at high temperatures, and have the ability to withstand cycles of rapid heating and cooling. In order to produce a better, more economical die the following standards are maintained:

• The dies part along a single, flat plane whenever possible. If not, the parting plane follows the contour of the part.
• The parting surface is a plane through the center of the forging and not near an upper or lower edge.
• Adequate draft is provided; usually at least 3° for aluminium and 5° to 7° for steel.
• Generous fillets and radii are used.
• Ribs are low and wide.
• The various sections are balanced to avoid extreme difference in metal flow.
• Full advantage is taken of fiber flow lines.
• Dimensional tolerances are not closer than necessary.

Barrelling occurs when, due to friction between the work piece and the die or punch, the work piece bulges at its centre in such a way as to resemble a barrel. This leads to the central part of the work piece to come in contact with the sides of the die sooner than if there were no friction present, creating a much greater increase in the pressure required for the punch to finish the forging.

The dimensional tolerances of a steel part produced using the impression-die forging method are outlined in the table below. The dimensions across the parting plane are affected by the closure of the dies, and are therefore dependent on die wear and the thickness of the final flash. Dimensions that are completely contained within a single die segment or half can be maintained at a significantly greater level of accuracy.

Dimensional tolerances for impression-die forgings

Mass [kg (lb)]	Minus tolerance [mm (in)]	Plus tolerance [mm (in)]
0.45 (1)	0.15 (0.006)	0.46 (0.018)
0.91 (2)	0.20 (0.008)	0.61 (0.024)
2.27 (5)	0.25 (0.010)	0.76 (0.030)
4.54 (10)	0.28 (0.011)	0.84 (0.033)
9.07 (20)	0.33 (0.013)	0.99 (0.039)
22.68 (50)	0.48 (0.019)	1.45 (0.057)
45.36 (100)	0.74 (0.029)	2.21 (0.087)

A lubricant is used when forging to reduce friction and wear. It is also used as a thermal barrier to restrict heat transfer from the workpiece to the die. Finally, the lubricant acts as a parting compound to prevent the part from sticking in the dies.

Press forging

Press forging works by slowly applying a continuous pressure or force, which differs from the near-instantaneous impact of drop-hammer forging. The amount of time the dies are in contact with the workpiece is measured in seconds (as compared to the milliseconds of drop-hammer forges). The press forging operation can be done either cold or hot.

The main advantage of press forging, as compared to drop-hammer forging, is its ability to deform the complete workpiece. Drop-hammer forging usually only deforms the surfaces of the work piece in contact with the hammer and anvil; the interior of the workpiece will stay relatively undeformed. Another advantage to the process includes the knowledge of the new part's strain rate. By controlling the compression rate of the press forging operation, the internal strain can be controlled.

There are a few disadvantages to this process, most stemming from the workpiece being in contact with the dies for such an extended period of time. The operation is a time-consuming process due to the amount and length of steps. The workpiece will cool faster because the dies are in contact with workpiece; the dies facilitate drastically more heat transfer than the surrounding atmosphere. As the workpiece cools it becomes stronger and less ductile, which may induce cracking if deformation continues. Therefore, heated dies are usually used to reduce heat loss, promote surface flow, and enable the production of finer details and closer tolerances. The workpiece may also need to be reheated.

When done in high productivity, press forging is more economical than hammer forging. The operation also creates closer tolerances. In hammer forging a lot of the work is absorbed by the machinery; when in press forging, the greater percentage of work is used in the work piece. Another advantage is that the operation can be used to create any size part because there is no limit to the size of the press forging machine. New press forging techniques have been able to create a higher degree of mechanical and orientation integrity. By the constraint of oxidation to the outer layers of the part, reduced levels of microcracking occur in the finished part.

Press forging can be used to perform all types of forging, including open-die and impression-die forging. Impression-die press forging usually requires less draft than drop forging and has better dimensional accuracy. Also, press forgings can often be done in one closing of the dies, allowing for easy automation.

Upset forging

"Upsetting" redirects here. For other uses, see upset (disambiguation).

Upset forging increases the diameter of the workpiece by compressing its length. Based on number of pieces produced, this is the most widely used forging process. A few examples of common parts produced using the upset forging process are engine valves, couplings, bolts, screws, and other fasteners.

Upset forging is usually done in special high-speed machines called crank presses. The machines are usually set up to work in the horizontal plane, to facilitate the quick exchange of workpieces from one station to the next, but upsetting can also be done in a vertical crank press or a hydraulic press. The initial workpiece is usually wire or rod, but some machines can accept bars up to 25 cm (9.8 in) in diameter and a capacity of over 1000 tons. The standard upsetting machine employs split dies that contain multiple cavities. The dies open enough to allow the workpiece to move from one cavity to the next; the dies then close and the heading tool, or ram, then moves longitudinally against the bar, upsetting it into the cavity. If all of the cavities are utilized on every cycle, then a finished part will be produced with every cycle, which makes this process advantageous for mass production.

These rules must be followed when designing parts to be upset forged:

• The length of unsupported metal that can be upset in one blow without injurious buckling should be limited to three times the diameter of the bar.
• Lengths of stock greater than three times the diameter may be upset successfully, provided that the diameter of the upset is not more than 1.5 times the diameter of the stock.
• In an upset requiring stock length greater than three times the diameter of the stock, and where the diameter of the cavity is not more than 1.5 times the diameter of the stock, the length of unsupported metal beyond the face of the die must not exceed the diameter of the bar.

Automatic hot forging

The automatic hot forging process involves feeding mill-length steel bars (typically 7 m (23 ft) long) into one end of the machine at room temperature and hot forged products emerge from the other end. This all occurs rapidly; small parts can be made at a rate of 180 parts per minute (ppm) and larger can be made at a rate of 90 ppm. The parts can be solid or hollow, round or symmetrical, up to 6 kg (13 lb), and up to 18 cm (7.1 in) in diameter. The main advantages to this process are its high output rate and ability to accept low-cost materials. Little labor is required to operate the machinery.

There is no flash produced so material savings are between 20 and 30% over conventional forging. The final product is a consistent 1,050 °C (1,920 °F) so air cooling will result in a part that is still easily machinable (the advantage being the lack of annealing required after forging). Tolerances are usually ±0.3 mm (0.012 in), surfaces are clean, and draft angles are 0.5 to 1°. Tool life is nearly double that of conventional forging because contact times are on the order of 0.06-second. The downside is that this process is only feasible on smaller symmetric parts and cost; the initial investment can be over $10 million, so large quantities are required to justify this process.

The process starts by heating the bar to 1,200 to 1,300 °C (2,190 to 2,370 °F) in less than 60 seconds using high-power induction coils. It is then descaled with rollers, sheared into blanks, and transferred through several successive forming stages, during which it is upset, preformed, final forged, and pierced (if necessary). This process can also be coupled with high-speed cold-forming operations. Generally, the cold forming operation will do the finishing stage so that the advantages of cold-working can be obtained, while maintaining the high speed of automatic hot forging.

Examples of parts made by this process are: wheel hub unit bearings, transmission gears, tapered roller bearing races, stainless steel coupling flanges, and neck rings for liquid propane (LP) gas cylinders.^[22] Manual transmission gears are an example of automatic hot forging used in conjunction with cold working.

Roll forging

Roll forging is a process where round or flat bar stock is reduced in thickness and increased in length. Roll forging is performed using two cylindrical or semi-cylindrical rolls, each containing one or more shaped grooves. A heated bar is inserted into the rolls and when it hits a spot the rolls rotate and the bar is progressively shaped as it is rolled through the machine. The piece is then transferred to the next set of grooves or turned around and reinserted into the same grooves. This continues until the desired shape and size is achieved. The advantage of this process is there is no flash and it imparts a favorable grain structure into the workpiece.

Examples of products produced using this method include axles, tapered levers and leaf springs.

Net-shape and near-net-shape forging

See also: Near-net-shape

This process is also known as precision forging. It was developed to minimize cost and waste associated with post-forging operations. Therefore, the final product from a precision forging needs little or no final machining. Cost savings are gained from the use of less material, and thus less scrap, the overall decrease in energy used, and the reduction or elimination of machining. Precision forging also requires less of a draft, 1° to 0°. The downside of this process is its cost, therefore it is only implemented if significant cost reduction can be achieved.

Cold forging

Near net shape forging is most common when parts are forged without heating the slug, bar or billet. Aluminum is a common material that can be cold forged depending on final shape. Lubrication of the parts being formed is critical to increase the life of the mating dies.

Induction forging

Main article: Induction forging

Unlike the above processes, induction forging is based on the type of heating style used. Many of the above processes can be used in conjunction with this heating method.

Multidirectional forging

Multidirectional forging is forming of a work piece in a single step in several directions. The multidirectional forming takes place through constructive measures of the tool. The vertical movement of the press ram is redirected using wedges which distributes and redirects the force of the forging press in horizontal directions.

Isothermal forging

Isothermal forging is a process by which the materials and the die are heated to the same temperature (iso- meaning "equal"). Adiabatic heating is used to assist in the deformation of the material, meaning the strain rates are highly controlled. This technique is commonly used for forging aluminium, which has a lower forging temperature than steels. Forging temperatures for aluminum are around 430 °C (806 °F), while steels and super alloys can be 930 to 1,260 °C (1,710 to 2,300 °F).

Benefits:

• Near net shapes which lead to lower machining requirements and therefore lower scrap rates
• Reproducibility of the part
• Due to the lower heat loss smaller machines can be used to make the forging

Disadvantages:

• Higher die material costs to handle temperatures and pressures
• Uniform heating systems are required
• Protective atmospheres or vacuum to reduce oxidation of the dies and material
• Low production rates

Materials and applications

Solid forged billets of steel (glowing incandescently) being loaded in a large industrial chamber furnace, for re-heating

Forging of steel

Depending on the forming temperature steel forging can be divided into:

• Hot forging of steel
  • Forging temperatures above the recrystallization temperature between 950–1250 °C
  • Good formability
  • Low forming forces
  • Constant tensile strength of the workpieces
• Warm forging of steel
  • Forging temperatures between 750–950 °C
  • Less or no scaling at the workpiece surface
  • Narrower tolerances achievable than in hot forging
  • Limited formability and higher forming forces than for hot forging
  • Lower forming forces than in cold forming
• Cold forging of steel
  • Forging temperatures at room conditions, self-heating up to 150 °C due to the forming energy
  • Narrowest tolerances achievable
  • No scaling at workpiece surface
  • Increase of strength and decrease of ductility due to strain hardening
  • Low formability and high forming forces are necessary

For industrial processes steel alloys are primarily forged in hot condition. Brass, bronze, copper, precious metals and their alloys are manufactured by cold forging processes; each metal requires a different forging temperature.

Forging of aluminium

• Aluminium forging is performed at a temperature range between 350–550 °C
• Forging temperatures above 550 °C are too close to the solidus temperature of the alloys and lead in conjunction with varying effective strains to unfavorable workpiece surfaces and potentially to a partial melting as well as fold formation.
• Forging temperatures below 350 °C reduce formability by increasing the yield stress, which can lead to unfilled dies, cracking at the workpiece surface and increased die forces

Due to the narrow temperature range and high thermal conductivity, aluminium forging can only be realized in a particular process window. To provide good forming conditions a homogeneous temperature distribution in the entire workpiece is necessary. Therefore, the control of the tool temperature has a major influence to the process. For example, by optimizing the preform geometries the local effective strains can be influenced to reduce local overheating for a more homogeneous temperature distribution.

Application of aluminium forged parts

High-strength aluminium alloys have the tensile strength of medium strong steel alloys while providing significant weight advantages. Therefore, aluminium forged parts are mainly used in aerospace, automotive industry and many other fields of engineering especially in those fields, where highest safety standards against failure by abuse, by shock or vibratory stresses are needed. Such parts are for example pistons, chassis parts, steering components and brake parts. Commonly used alloys are AlSi1MgMn (EN AW-6082) and AlZnMgCu1,5 (EN AW-7075). About 80% of all aluminium forged parts are made of AlSi1MgMn. The high-strength alloy AlZnMgCu1,5 is mainly used for aerospace applications.

Forging of magnesium

• Magnesium forging occurs at a temperature range between 290–450 °C 

Magnesium alloys are more difficult to forge due to their low plasticity, low sensitivity to strain rates and narrow forming temperature. Using semi-open die hot forging with a three-slide forging press (TSFP) has become a newly developed forging method for Mg-Al alloy AZ31, commonly used in forming aircraft brackets. This forging method has shown to improve tensile properties but lacks uniform grain size. Even though the application of magnesium alloys increases by 15–20% each year in the aerospace and automotive industry, forging magnesium alloys with specialized dies is expensive and an unfeasible method to produce parts for a mass market. Instead, most magnesium alloy parts for industry are produced by casting methods.

Equipment

Hydraulic drop-hammer

(a) Material flow of a conventionally forged disc; (b) Material flow of an impactor forged disc

The most common type of forging equipment is the hammer and anvil. Principles behind the hammer and anvil are still used today in drop-hammer equipment. The principle behind the machine is simple: raise the hammer and drop it or propel it into the workpiece, which rests on the anvil. The main variations between drop-hammers are in the way the hammer is powered; the most common being air and steam hammers. Drop-hammers usually operate in a vertical position. The main reason for this is excess energy (energy that is not used to deform the workpiece) that is not released as heat or sound needs to be transmitted to the foundation. Moreover, a large machine base is needed to absorb the impacts.

To overcome some shortcomings of the drop-hammer, the counterblow machine or impactor is used. In a counterblow machine both the hammer and anvil move and the workpiece is held between them. Here excess energy becomes recoil. This allows the machine to work horizontally and have a smaller base. Other advantages include less noise, heat and vibration. It also produces a distinctly different flow pattern. Both of these machines can be used for open-die or closed-die forging.

Forging presses

A forging press, often just called a press, is used for press forging. There are two main types: mechanical and hydraulic presses. Mechanical presses function by using cams, cranks and/or toggles to produce a preset (a predetermined force at a certain location in the stroke) and reproducible stroke. Due to the nature of this type of system, different forces are available at different stroke positions. Mechanical presses are faster than their hydraulic counterparts (up to 50 strokes per minute). Their capacities range from 3 to 160 MN (300 to 18,000 short tons-force). Hydraulic presses use fluid pressure and a piston to generate force. The advantages of a hydraulic press over a mechanical press are its flexibility and greater capacity. The disadvantages include a slower, larger, and costlier machine to operate.

The roll forging, upsetting, and automatic hot forging processes all use specialized machinery.

List of large forging presses, by ingot size

Force (tonnes)	Ingot size (tonnes)	Company	Location
16,500	600	Shanghai Electric Group	Shanghai, China
16,000	600	China National Erzhong Group	Deyang, China
14,000	600	Japan Steel Works	Japan
15,000	580	China First Heavy Industries Group	Heilongjiang, China
13,000		Doosan	South Korea

List of large forging presses, by force

Force (tonnes)	Force (tons)	Ingot size (tonnes)	Company	Location
80,000	(88,200)	>150	China Erzhong	Deyang, China
75,000	(82,690)		VSMPO-AVISMA	Russia
65,000	(71,660)		Aubert & Duval	Issoire, France
53,500	(60,000)		Weber Metals, Inc.	California, United States
(45,350)	50,000	20	Alcoa 50,000 ton forging press Alcoa, Wyman Gordon	USA
40,000	(44,100)		Aubert & Duval	Pamiers, France
30,000	(33,080)	8	Wyman Gordon	Livingston, Scotland
30,000	(33,070)		Weber Metals, Inc.	California, United States
30,000	(33,070)		Howmet Aerospace	Georgia, United States

10th millennium BC

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/10th_millennium_BC

The 10th millennium BC spanned the years 10,000 BC to 9001 BC (c. 12 ka to c. 11 ka). It marks the beginning of the transition from the Palaeolithic to the Neolithic via the interim Mesolithic (Northern Europe and Western Europe) and Epipaleolithic (Levant and Near East) periods, which together form the first part of the Holocene epoch that is generally believed to have begun c. 9700 BC (c. 11.7 ka) and is the current geological epoch. It is impossible to precisely date events that happened around the time of this millennium, and all dates mentioned here are estimates mostly based on geological analysis, anthropological analysis, and radiometric dating.

Holocene epoch

The main characteristic of the Holocene has been the worldwide abundance of Homo sapiens sapiens (humankind). The epoch began in the wake of the Würm glaciation, generally known as the Last Ice Age, which began 109 ka and ended 14 ka when Homo sapiens sapiens was in the Palaeolithic (Old Stone) Age. Following the Late Glacial Interstadial from 14 ka to 12.9 ka, during which global temperatures rose significantly, the Younger Dryas began. This was a temporary reversal of climatic warming to glacial conditions in the Northern Hemisphere and coincided with the end of the Upper Palaeolithic. The Younger Dryas ceased c. 9700 BC, marking the cutover from Pleistocene to Holocene.

In the geologic time scale, there are three (tentatively four) stratigraphic stages of the Holocene beginning c. 9700 BC with the "Greenlandian" (to c. 6236 BC). The starting point for the Greenlandian is the Global Boundary Stratotype Section and Point (GSSP) sample from the North Greenland Ice Core Project, which has been correlated with the Younger Dryas. The Greenlandian was succeeded by the "Northgrippian" (to c. 2250 BC) and the "Meghalayan". All three stages were officially ratified by the International Commission on Stratigraphy in July 2018. It has been proposed that the Meghalayan should be terminated c. 1950 and succeeded by a new stage provisionally called "Anthropocene".

In the Holocene's first millennium, the Palaeolithic began to be superseded by the Neolithic (New Stone) Age which lasted about 6,000 years, depending on location. The gradual transition period is sometimes termed Mesolithic (northern and western Europe) or Epipalaeolithic (Levant and Near East). The glaciers retreated as the world climate became warmer and that inspired an agricultural revolution, though at first, the dog was probably the only domesticated animal. This was accompanied by a social revolution in that humans gained from agriculture the impetus to settle. Settlement is the key precursor to civilisation, which cannot be achieved by a nomadic lifestyle.

The world population, c. 10,000 BC, is believed to have been more or less stable. It has been estimated that there were some five million people at the time of the Last Glacial Maximum, growing to forty million by 5000 BC and 100 million by 1600 BC, which is an average growth rate of 0.027% p.a. from the Neolithic to the Middle Bronze Age. Around 10,000 BC, most people lived in hunter-gatherer communities scattered across all continents except Antarctica and Zealandia. As the Würm/Wisconsin ended, settlement of northern regions was again possible.

Beginnings of agriculture

Agriculture developed in different parts of the world at different times. In many places, people learned how to cultivate without outside help; elsewhere, as in western Europe, the skills were imported. A decrease in human height accompanied the rise of agriculture near the start of the Holocene period (10,000 BC) and was later correlated with urban population density.

The Natufian culture prevailed in the Levant through the 10th millennium and was unusual in that it supported a sedentary or semi-sedentary population even before the introduction of agriculture. An early example is 'Ain Mallaha, which may have been the first village in which people were wholly sedentary. The Natufian people are believed to have founded another early settlement on the site of Jericho (Tell es-Sultan) where there is evidence of building between 9600 BC and 8200 BC. Dates for the Natufian are indeterminate and range broadly from c. 13,050 BC to c. 7550 BC. It is possible that the early cultivation of figs began in the Jordan River valley sometime after the middle of the 10th millennium. Besides the fig trees, the people may have begun cultivation of wild plants such as barley and pistachio; and they possibly began herding goats, pigs and cattle.

Agriculture began to be developed by the various communities of the Fertile Crescent, which included the Levant, but it would not be widely practised for another 2,000 years by which time Neolithic culture was becoming well established in many parts of the Near East. Among the earliest cultivated plants were forms of millet and rice grown in the Middle East, possibly in this millennium but more likely after 9000 BC. By about 9500 BC, people in south-eastern Anatolia were harvesting wild grasses and grains. The earliest evidence of sheep herding has been found in northern Iraq, dated before 9000 BC.

Pottery

Prehistoric chronology is almost entirely reliant upon the dating of material objects of which pottery is by far the most widespread and the most resistant to decay. All locations and generations developed their own shapes, sizes and styles of pottery, including methods and styles of decoration, but there was consistency among stratified deposits and even shards can be classified by time and place. Pottery is believed to have been discovered independently in various places, beginning with China c. 18,000 BC, and was probably created accidentally by fires lit on clay soil. The main discovery of pottery dated to the 10th millennium has been at Bosumpra Cave (early tenth-millennium cal. BC) on the Kwahu Plateau in southeastern Ghana and Ounjougou (c.9400 BC) in Central Mali, providing evidence of an independent invention of pottery in Sub-Saharan Africa in different climatic zones.

The first chronological pottery system was the Early, Middle and Late Minoan framework devised in the early 20th century by Sir Arthur Evans for his findings at Knossos. This covered the Bronze Age in twelve phases from c. 2800 BC to c. 1050 BC and the principle was later extended to mainland Greece (Helladic) and the Aegean islands (Cycladic). Dame Kathleen Kenyon was the principal archaeologist at Tell es-Sultan (ancient Jericho) and she discovered that there was no pottery there. The potter's wheel had not yet been invented and, where pottery as such was made, it was still hand-built, often by means of coiling, and pit fired.

Kenyon discovered vessels such as bowls, cups, and plates at Jericho which were made from stone. She reasonably surmised that others made from wood or vegetable fibres would have long since decayed. Using Evans' system as a benchmark, Kenyon divided the Near East Neolithic into phases called Pre-Pottery Neolithic A (PPNA), from c. 10,000 BC to c. 8800 BC; Pre-Pottery Neolithic B (PPNB), from c. 8800 BC to c. 6500 BC; and then Pottery Neolithic (PN), which had varied start-points from c. 6500 BC until the beginnings of the Bronze Age towards the end of the 4th millennium. In the 10th millennium, the Natufian culture co-existed with the PPNA which prevailed in the Levantine and upper Mesopotamian areas of the Fertile Crescent.

Other cultural developments

Africa

Example of Saharan rock art depicting giraffes from Anakom, Niger.

In North Africa, Saharan rock art engravings in what is known as the Bubalus (Large Wild Fauna) period have been dated to between 10,000 BC and 7000 BC. Wall paintings found in Ethiopia and Eritrea depict human activity; some of the older paintings are thought to date back to around 10,000 BC. In Prehistoric Egypt, a culture of hunter-gatherers replaced a grain grinding culture in 10,000 BC. The Abu Madi tel mounds in the Sinai Peninsula have been dated c. 9660 to c. 9180 BC.

Americas

The Clovis culture was widely distributed throughout North America. The people were hunter-gatherers and the culture's duration is believed to have been from c.9050 BC to c.8800 BC. There is evidence of increasing use of Clovis point tool technology for hunting.

Elsewhere in North America, the Petroglyphs at Winnemucca Lake, in what is today northwest Nevada, were carved by this time, possibly as early as 12.8 ka or as late as 10 ka.

Eurasia

The sites at Göbekli Tepe, which is home to megalithic structures, Hallan Çemi Tepesi, both in south-eastern Anatolia, and at Tell Qaramel, in north-west Syria, may have been occupied during this millennium. It was found out that gastronomy first emerged in Göbekli Tepe in this millennium. This most important discovery shedding light on the beginning of gastronomy in Anatolia consists of religious places in which feasts were held in this millennium that were found in the archaeological excavations conducted in Göbekli Tepe in Urfa province which is called the zero point of time. As a result of the investigations carried out in Göbekli Tepe which is dated to this millennium, it was determined that the people created cult structures and had a culture for religious purposes during the early Neolithic period and that they held feasts in which they offered foods while performing these cultures. The Sassi di Matera in southern Italy is believed to have been the site of human settlement since the Paleolithic period in this millennium, making it one of the oldest continuously inhabited settlements in history. At the Hasankeyf Mound in Turkey, Europe, almost all archaeological data date to this millennium. In Great Britain, which was not then an island, the Star Carr site in North Yorkshire is believed to have been inhabited by Maglemosian peoples for about 800 years from c. 9335 BC to c. 8525 BC.

Environmental changes

In the southern hemisphere, rising sea levels had gradually formed Bass Strait, separating Tasmania from mainland Australia. This process is believed to have been complete by about the beginning of the 10th millennium. Bass Strait had been a plain populated by indigenous people who are thought to have first arrived around 40,000 years ago.

The Wisconsin glaciation had sheeted much of North America and, as it retreated, its meltwaters created an immense proglacial lake now known as Lake Agassiz. Sometime after 10,000 BC, the retreating glaciers created the rock formation on Cannon Mountain in present-day New Hampshire that was known as the Old Man of the Mountain until its collapse in 2003.

Chronological method

The ongoing Quaternary System/Period represents the last 2.58 million years since the end of the Neogene and is officially divided into the Pleistocene and Holocene Series/Epochs. The Holocene has been assigned an age of 11,700 calendar years before 2000 CE which means it began c. 9700 BC in the 10th millennium. It is preceded in the geological time scale by the Late Pleistocene sub-epoch, also known as the Tarantian Stage/Age, which awaits formal ratification by the International Union of Geological Sciences (IUGS) and tentatively spans the time from c. 126,000 BC to c. 9700 BC. Preceding the Late Pleistocene is the Middle Pleistocene sub-epoch, or Chibanian Stage/Age, which also awaits ratification and tentatively spans the time from c. 773,000 BC to c. 126,000 BC. The Early Pleistocene from c. 2,580,000 BC until c. 773,000 is sub-divided into two Stages/Ages which have been officially defined: the Gelasian (until c. 1,800,000 BC) and the Calabrian.

The Holocene calendar, devised by Cesare Emiliani in 1993, places its epoch at 10,000 BC (with the year 2023 being rendered as 12023 HE). The Human Era calendar attempts to simplify the calculation of time spans across the BC-CE divide by designating a more universally relevant epoch date: the start of human settlements (instead of the birth of Jesus Christ). CE dates can be converted by adding 10,000 years; converting BC dates requires subtraction from 10,001 (since the Gregorian calendar lacks a year zero).