Conventional martensite quenching and organization and performance Conventional martensite quenching and organization and performance. Over the past 20 years, the conventional high carbon chromium martensitic of bearing steel quenching and development process of the main points two aspects: one is on quenching and process parameters on the organization and performance effects, such as quenching and organization transformation, in the process of austenite decomposition, after quenching and the toughness of the fatigue performance and etc; On the other hand is the quenching and process performance, such as quenching condition to the size and influence of the deformation of the dimension stability, etc. Conventional martensite after quenching the organization as the martensite, austenite and not dissolve (residues) of carbide. Among them, the martensite form of organization and can be divided into two categories: in metallurgical microscope (magnification under 1000 times the average), martensite can be divided into board strips martensite and flake martensite two typical organization, general hardened martensitic for attrib wattle and drop the hybrid organization, or call between the intermediate form between them-ZaoHe shape martensite (bearing on the industry of the so-called hidden crystal martensite, crystal martensite); At high magnification in by electron microscopy, its structure and can be divided into a wrong tangles non-infarct-related and crystal. The specific form of organization mainly depends on the carbon content of matrix, austenitic the higher the temperature is, the more unstable original organization, the austenitic matrix of the carbon content is higher, after quenching organization austenite more, flake martensite, the more size is larger, the structure of the greater proportion of crystal nervine, and easy form quenching microscopic cracks. In general, the matrix carbon content below 0.3%, martensite main is a wrong and structure of the martensite mainly slatted; The carbon content is higher than 0.6% matrix, martensite is a wrong and had mixed and structure of sheets of crystal martensite; Matrix carbon content was 0.75%, with visible ridge in the appear a large patch of martensite, and flake martensite growth impact with each other in microscopic cracks. At the same time, along with the austenitic transition temperature rise, quenching hardness improve, toughness drop, but austenitic change the temperature too high, because after quenching austenite too much to drop hardness. Conventional martensite after quenching the organization of austenite content general for 6 to 15%, austenite for soft and stability phase, in certain conditions (such as tempering, natural aging or the use of parts in the process), its instability happened into martensite or bainite. The consequences of decomposition is part of hardness improve, toughness drop, size change and influence the dimension precision parts even normal work. The size of the higher accuracy bearing parts, general hope austenite as little as possible, such as quenching complement water or cryogenic after treatment, and a high temperature of tempering etc. But austenite can improve toughness and crack resistance, certain conditions, in the surface of workpiece austenite still can reduce the contact stress concentration, and improve the bearing contact fatigue life, this case in the process and the composition of the material on the take certain steps to keep certain amount of austenite and improve the stability, such as join austenitic stabilization element Si, Mn,; For stabilizing treatment, etc.
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