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What is a quench crack? What are the categories? What is the original cause?

by:Kehua     2022-07-18
Quenching is a steel heat treatment process and a process. In the casting process, different situations will occur, and defective products will appear. such as quenching. So what are quenching cracks? What are the quenching cracks and why are they formed? Quenching cracks What are quenching cracks? They are cracks generated during the quenching process or at room temperature after quenching. The latter is also called aging crack. There are many reasons for quenching cracks. When analyzing quenching cracks, Kehua Induction Heating Equipment should distinguish them according to the characteristics of cracks. Quenching cracks Classification of quenching cracks: Common quenching cracks are: longitudinal cracks, transverse cracks, arc cracks, peeling cracks, network cracks, cold treatment cracks, grinding cracks, wire cutting cracks, fatigue cracks, stress corrosion cracks, etc. Kehua Induction Heating Equipment for example: Longitudinal cracks The cracks are axial, thin and long in shape. When the mold is completely quenched, that is, centerless quenching, the core is transformed into quenched martensite with the largest specific volume, resulting in tangential tensile stress. The higher the carbon content of the die steel, the greater the tangential tensile stress. Above the strength limit of the steel results in the formation of longitudinal cracks. The following factors aggravate the generation of longitudinal cracks: (1) There are many harmful impurities with low melting point such as S, P, Sb, Bi, Pb, Sn, As, etc. in the steel, and the ingot is longitudinally segregated along the rolling direction during rolling. , It is easy to generate stress concentration to form longitudinal quenching cracks or longitudinal cracks formed by rapid cooling of raw materials after rolling, which are not processed and remain in the product, resulting in the expansion of final quenching cracks to form longitudinal cracks; (2) The size of the die is within the quenching crack-sensitive size range of the steel. (The quenching and cracking risk size of carbon tool steel is 8-15mm, and the dangerous size of medium and low alloy steel is 25-40mm) or when the selected quenching cooling medium greatly exceeds the critical quenching cooling rate of the steel, longitudinal cracks are easily formed. Preventive measures: (1) Strict inspection of raw materials in storage, and do not put into production the steel with excess harmful impurities; (2) Use vacuum smelting, out-of-furnace refining or electroslag remelting mold steel as much as possible; (3) Improve the heat treatment process and use vacuum processing Heat, protective atmosphere heating and fully deoxidized salt bath furnace heating and analysis quenching, isothermal quenching; (4) Change from centerless quenching to core quenching, that is, incomplete quenching, and obtain lower bainite structure with high strength and toughness. The tensile stress can effectively avoid the longitudinal cracking of the mold and the quenching distortion. Forging cracks, quenching cracks, grinding cracks, what is the difference between these three? Forging cracks are caused by material inhomogeneity caused by impurities such as carbon mixed in during forging. Quenching cracks are caused by uneven internal force caused by sudden cooling or too fast cooling. Grinding cracks are caused by errors in the machining process. Quenching cracks How to control the formation of quenching cracks? There are many reasons, whether the forgings are defective, whether the annealing meets the requirements, whether there are problems in the quenching and annealing operations, etc., all of which may cause quenching cracks. During the quenching process, when the huge stress generated by quenching is greater than the strength of the material itself, cracks will occur. Quenching cracks tend to occur shortly after the martensitic transformation begins, the distribution of cracks. The above are the relevant answers about quenching cracks. If the quenching process is skilled, a lot of defects will be reduced, but once quenching cracks appear, it is necessary to find the cause and prevent the production of defective products.
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