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ASM International said:
http://asm.asminternational.org/ht-echarts/3046_OMM120707_figure.pdf
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ASM International said:Cold treatment of steel consists of exposing the ferrous material to subzero temperatures to either impart or enhance specific conditions or properties of the material.
Unlike heat treating, which requires that temperature be precisely controlled to avoid reversal, successful transformation through cold treating depends only on the attainment of the minimum low temperature (-84°C, or -120°F) and is not affected by lower temperatures. Typical cryogenic treatment consists of a slow cool-down (~2.5°C/min, or 4.5°F/min) from ambient temperature to liquid nitrogen temperature. When the material reaches approximately 80K (-315°F), it is soaked for an appropriate time (generally 24 h). At the end of the soak period, the material is removed from the liquid nitrogen and allowed to warm to room temperature in ambient air. Temperature can be controlled accurately and thermal shock to the material is avoided by conducting the cool-down cycle in gaseous nitrogen.
ASM International said:The absence of a clear-cut understanding of the mechanism(s) by which cryogenic treatment improves performance has hindered its widespread acceptance in the industry.
Nevertheless, studies have been conducted to determine the effects of cryogenic treatment. Theories about the reasons for the effects of cryogenic treatment include a more nearly complete transformation of retained austenite into martensite; precipitation of submicroscopic carbides; and a reduction in internal stresses in martensite that occurs when the submicroscopic carbide precipitation occurs.
A reduction in microcracking tendencies resulting from reduced internal stresses is suggested as a reason for improved properties.
Cold and cryogenic treating of steel is a process that involves subjecting steel to extremely low temperatures (below -100°C) in order to improve its physical and mechanical properties. This process is often used in the manufacturing of tools, knives, and other metal components to increase their durability and wear resistance.
The process involves two main steps: cold treating and cryogenic treating. In cold treating, the steel is cooled to around -80°C using liquid nitrogen or other cryogenic gases. This causes the steel's molecular structure to rearrange, making it more dense and increasing its strength. In cryogenic treating, the steel is then further cooled to around -196°C, which helps to transform any remaining austenite into martensite, a harder and more wear-resistant form of steel.
Cold and cryogenic treating can significantly improve the strength, durability, and wear resistance of steel. It also helps to reduce the risk of cracking, warping, and other forms of damage that can occur during the manufacturing process. Additionally, this process can enhance the steel's ability to retain its sharpness and edge, making it ideal for use in cutting tools and knives.
No, this process is not suitable for all types of steel. It is most commonly used on high-carbon and tool steels, as well as some stainless steels. The success of the treatment also depends on the quality and composition of the steel, as well as the specific temperature and duration of the treatment.
The main drawback of this process is the cost. The equipment and materials required for cold and cryogenic treating can be expensive, making it a more costly option compared to other types of heat treatment. Additionally, if not done properly, the treatment can cause brittleness in the steel, reducing its toughness and impact resistance.