38Cr2MoAl stamping die steel primary purpose of this steel is easy turning, and should be made sharp knife, scissors, saw, metal stamping dies, forming rolls, cold mold generally cold or hot trimming die, roller edge, screw pattern, line mode, milling knife, red Lang mold, round cylinder, the system of power transformers heart dies, cutting leather rolled steel knife, pipe forming rollers, special molding rollers, precision gauges, shape complexity of the cold tools, metallurgy, tin for mold, plastic, screw Heading molds. With high hardness, strength, wear resistance, sufficient toughness, and high hardenability, hardened and other process performance. Alloy tool used for such purposes are generally high-carbon steel, alloy steel, carbon mass fraction above 0.80%, chromium is an important alloying elements such steel, and its mass fraction is usually not more than 5%. But for some high wear resistance, mold steel after quenching deformation is small, the highest chromium content up to 13%, and for the formation of large carbides, mass fraction of carbon steel is also high, up 2.0% twenty three%. Cold die steel high carbon content, which organized the majority were eutectoid steel or ledeburite. Commonly used class of high-carbon steel low alloy steel, high carbon high chromium steel, chromium molybdenum steel, carbon steel, chromium tungsten Kushiro. Chemical Composition C 5 carbon ≤1.5Si ≤0.3Cr chrome silicon manganese ≤0.5Mo ≤12.0Mn molybdenum vanadium ≤1.0V use ≤0.4 7 1. 2. "cold treatment quenching and tempering of" quenching and tempering "state "Under the state use (suitable for high precision and dimensional stability requirements) 3." quenching and tempering + nitriding process "state use (suitable for high surface hardness) 4. cryogenic treatment in order to obtain maximum hardness and dimensional stability under die immediately after quenching cryogenic to -80 degrees -70 degrees Celsius, for 3-4 hours, then come back to deal with the fire, the cryogenic treatment of tool or mold hardness than conventional heat treatment hardness 1-3HRC. Changes in the shape and size of a large complex parts, cryogenic treatment in danger of cracking. 5. After nitriding mold or workpiece nitriding, the surface layer has a high hardness and corrosion resistance of certain hardening organization. 6. In the nitriding treatment, the surface hardness of about 525 ℃ 1250HV, nitriding time on the diffusion layer as shown in the following table. Nitriding time (hours) 203 060 nitriding depth mm 0.25 0.30 0.35 7. soft nitriding at 570 ℃, the workpiece surface hardness of about 950HV. Typically soft nitriding two hours, hardened layer depth can reach 10-20um. Grinding die blanks or working in low-temperature tempering state, grinding grinding prone to cracking. In order to prevent the occurrence of cracks should take a small amount of feed grinding grinding times, but it add a good water-cooled conditions. Line cutting complex shapes or large size molds, the final trip when using wire cutting, often encounter cracking phenomenon. To prevent cracking, the proposed gas quenching and tempering treatment to reduce heat stress, or pre-processing of the mold cavity embryos. 8 heat treatment and quenching: preheat 700 ~ 750 ℃, and then heated to 1000 ~ 1050 ℃ cooling in still air, such as steel with thickness of 6 inches or more is heated to 980 ~ 1030 ℃ in oil hardened better. Tempering: heating to 150 ~ 200 ℃, stay at this temperature and then cooled in still air. Hardness: HRC 61 or more. Annealing: heating to 800 ~ 850 ℃, in this temperature stays from 1 to 3 hours in the oven to cool gradually. Forged: 1050 ~ 950 ℃. 9 Typical be? A? 79? 1? 72, for example 1)? 1? 79? 1? 72 in the production of? A? 79? 1? 79? 1? 79? 1? 71 die cut? 1? 79? 1? 79, circular saw? a? 79? 1? 72, five? a? 79? 1? 78 stamping dies, forming rolls 2) making cold or hot trimming die, roller edge, silk pattern, line mode, transformer core die cutting steel? a? 79? 1? 78 mill? a? 79? 1? 79, pipe forming rollers, special shaped tube, nail starts molds. 3) steel sheet thickness ≤6mm? A? 79? A? 70-efficient blanking die, stamping die, pressure die 4) all kinds of scissors? A? 79? 1? 79, mosaic? 1? 79? 1? 79? 1? 79? 1? 72, thread rolling die. 5) resistant slider cold heading dies, deep drawing mold, cold extrusion dies. 6) thermosetting resin-type feel,? A? 79? A? 72-like plastic mold.