Quenching network crack of the hottest die steel a

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Quenching crack of die steel and preventive measures

the crack depth is shallow, generally about 0 5mm, radial, alias cracking. The original foreign made products also have many deficiencies, mainly due to: (1) the raw materials have a deep decarburization layer, the cold cutting processing is not removed, or the finished mold is heated in an oxidizing atmosphere furnace, resulting in oxidative decarburization; (2) The metal structure of the decarburized surface layer of the die is different from that of the martensite of the steel matrix in terms of carbon content and specific volume. When the decarburized surface layer of the steel is quenched, it produces large tensile stress. Therefore, the surface metal is often pulled and cracked along the grain boundary; (3) The raw material is coarse-grained steel, the original structure is coarse, and the experimental ferrite can be started when there are large blocks. Conventional quenching cannot be eliminated, and it remains in the quenched structure, or the temperature control is not accurate, the instrument fails, the structure overheats, even burns, the grain coarsens, and the grain boundary adhesion is lost, When the mold is quenched and cooled, the carbides of the steel are precipitated along the austenite crystal. This native of Guangzhou believes that life needs to find its own world before it can form a meaningful boundary. The strength of the grain boundary is greatly reduced, the toughness is poor, and the brittleness is large. Under the action of tensile stress, the carbides crack along the grain boundary in shape

preventive measures: (1) strictly inspect the chemical composition, metallographic structure and flaw detection of raw materials. Unqualified raw materials and coarse grain steel should not be used as mold materials; (2) Select fine grain steel and vacuum electric furnace steel, recheck the decarburization layer depth of raw materials before production, and the cold cutting allowance must be greater than the decarburization layer depth; (3) Formulate advanced and reasonable heat treatment 2. Supporting equipment: manage the process, select microcomputer temperature control instruments, and the control accuracy reaches ± 1.5 ℃, and regularly calibrate the instruments on site; (4) The final treatment of mold products adopts measures such as vacuum electric furnace, protective atmosphere furnace and fully deoxidized salt bath furnace to heat mold products, so as to effectively prevent and avoid the formation of cracks

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