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| Hard Metal Facing |
| The coating of a metal surface with hard metal alloy powders in order to increase the wear resistance of the surface. |
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| Hardenability |
| A term applied to steels to describe the relative ease with which martensite can be formed in the steel. The lower the cooling rate at which a fully martensitic microstructure can be formed in the steel when it is cooled from austenitic condition the higher is the hardenability. Hardenability is commonly assessed by the Jominy end quench test. |
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| Hardening |
| Increasing the hardness of metals by mechanical, thermo-mechanical, thermal or thermo-chemical treatments. |
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| Hardness |
| A measure of the resistance of a metal to indentation by a loaded indenter. The common tests used to determine hardness are the Vickers, Brinell or Rockwell tests. |
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| Heat |
| In steel making this is often used to describe the steel produced from a single melting operation. |
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| Heat Resisting Steel |
| Low and high alloy steels required to operate at very high temperatures and therefore they may require one or more of the following characteristics: creep resistance, resistance to oxidation, or other forms of gaseous attack, and freedom from microstructural changes that would lead to their embrittlement. Because service conditions can vary greatly a wide range of steel compositions come under the category of heat resisting with C-Mn, or low alloy steels of the Cr- Mo-V type being used to 500-525C and austenitic stainless grades, containing for example 25% Cr, 20% Ni, being used at higher temperatures. |
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| Heat Treatment |
| Heating and cooling a solid metal or alloy in such a way as to obtain desired microstructure and properties. Heating for the purpose of hot-working is excluded from this definition. |
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| High Speed Tool Steel |
| High alloy steels that can be used as a cutting tool material to machine other metals at high speeds, and still retain its cutting ability, even though the tool tip is at a low red heat. The various grades of this steel all contain 0.6% or more of carbon, a combined content of 7%, or more, of the elements tungsten, molybdenum and vanadium, 3-6% of chromium and in those required to operate at the highest temperatures additions of 4-13% of cobalt. |
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| High Yield Strength Steel |
| Other terms used to describe this type of steel are High Strength Low Alloy (HSLA) steel or Microalloyed steel. It is a steel that with a combination of small amounts of niobium (Nb), vanadium (V) or titanium (Ti), or a controlled combination, and a controlled hot rolling practice has a yield strength greater than that obtainable in a mild steel, (ie greater than ~250 Mpa). |
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| Hooke's Law |
| A law which states that when a material is behaving elastically, the strain in the material is directly proportional to the stress producing it. |
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| Hot Quenching |
| An imprecise term for describing the cooling of a material by quenching it into a medium, the temperature of which is above that of ambient. |
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| Hot Work |
| The plastic deformation of a metal by processes such as rolling, forging, or extrusion, carried out at a temperature and strain rate such that substantial strain hardening does not occur but instead the metal continues to yield relatively easily because the metal is recrystallising continuously. |
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| Hydrogen (H) |
| A gas which, when present in steel, can cause embrittlement, hair-line cracking, or even complete fracture, especially of high strength steels. Is an option as a controlled atmosphere medium for annealing, eg Ebher annealing, and also in high temperature annealing of grain oriented electrical steels. |
