"Gun quality" in the context of alloy steel like 8620H refers to a specific designation of steel that is intended for use in firearms. This designation implies that the steel has been manufactured and tested to meet certain stringent criteria that are essential for the performance and safety of firearm components. These criteria may include, but are not limited to, the following:
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Controlled Chemistry: The composition of the steel is tightly controlled to ensure consistent performance and to meet the mechanical properties required for gun components.
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Mechanical Properties: The steel must have the appropriate hardness, strength, and toughness to withstand the pressures and stresses encountered during the firing of the weapon.
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Surface Quality: The steel should have a high-quality surface finish to minimize the risk of fatigue and stress corrosion cracking, which are critical for parts such as barrels and receivers.
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Magnetic Particle Testing: For certain applications, the steel may undergo non-destructive testing such as magnetic particle inspection to detect surface and near-surface discontinuities that could lead to failure during use.
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Macroetch Testing: This test may be used to reveal the macrostructure and to check for homogeneity and absence of harmful defects in the steel.
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Amount of Discard: This refers to the practice of discarding a certain portion of the steel (usually the end pieces of a bar or billet) to ensure that the remaining material is free from potential defects that could affect its performance.
The "H" suffix in the steel grade 8620H indicates that the steel is of "hardenability" grade, meaning it is guaranteed to meet the hardenability requirements set by AISI-SAE standards. Hardenability is a measure of the depth and distribution of hardness induced by quenching, which is critical for steel parts that must have a hard, wear-resistant surface and a tough core, such as those found in firearms.
In summary, "gun quality" steel is engineered to meet the rigorous demands of firearm manufacturing, ensuring reliability, safety, and performance of the firearm components made from it.