Standard: GB/T 1229-2000 1. Characteristic description 7CrSiMnMoV is referred to as CH-1. It is a flame-quenched cold-work die steel developed by Shougang Special Steel Company. It is a new type of die steel developed and used in industrialized countries in recent years.
The characteristics are as follows:
(1) Good strength and toughness. Flame quenching has hardness and various properties similar to that of overall quenching. There is a high-toughness matrix under the hardened layer as a liner, and the cutting edge is not prone to cracking and chipping when working. After adopting the surface strengthening process, the hardened layer retains a certain compressive stress (304MPa), which can improve the fatigue strength and enable the mold to obtain a higher service life.
(2) Convenient repair and good weldability. When there is a deviation in manufacturing, the corresponding welding rod can be used for repair welding, and the desired effect can be achieved by grinding and trimming.
(3) The quenching deformation is small. After the mold is fully processed and formed, the cutting edge is heated to the quenching temperature with an oxygen-acetylene flame, and then air-cooled to achieve the purpose of quenching. No other processing is required, so the deformation is small.
(4) Cost saving. Cost reduction is because only oxygen-acetylene gas source is needed, which is not restricted by site and equipment, and the operation is convenient. The cumbersome process of multiple heating and tempering of the whole quenching is omitted, and the productivity is improved. Preliminary statistics show that compared with Cr12 steel molds, 7CrSiMnMoV steel molds manufactured by flame quenching process save about 80% of electricity, increase labor productivity by about 20%, reduce total heat treatment costs by about 70%, and increase mold life by more than 1.5 times.
2. Application: This kind of steel is especially suitable for making large-scale insert molds with large size, thick section and small quenching deformation, as well as stamping molds, blanking molds, paper cutters, ceramic molds, etc.
3. Processing specifications Firstly, the 7CrSiMnMoV round steel is forged into shapes according to requirements, or forged into various three-dimensional shapes (real shapes) according to the requirements of parts. After annealing, rough machining and smoothing, the shape of the cutting edge is processed in the machining center, and flame quenching after fitter repair and installation and debugging. The quenching preheating temperature is generally controlled at 180～200℃, and the preheating is 1～1.5h. For a single large, integral, closed cavity mold, the spray gun can be directly preheated. The quenching heating flame is a neutral flame, the flame length is 10-15mm, the oxygen pressure is controlled at 49-69MPa, and the acetylene pressure is controlled at 4.9-6.9MPa. When heating, the flame is 1～3mm away from the heating surface, 4～6mm from the edge of the cutting edge, the heating zone is controlled at 2～3mm, and the distance from the edge of the cutting edge is 4～6mm, and the heating speed is controlled at 160～200mm/min. The final hardness of the mold can be basically controlled at 52～62HRC, and the quenching depth is 1.5mm. After flame quenching, the material size change is much smaller than the overall quenching. For the insert structure mold with a length of less than 300mm, the gap between the joints is less than 0.12 mm, which fully meets the requirements for the life and accuracy of the blanking die. The above is some empirical technical data in the use of 7CrSiMnMoV steel to make motorcycle fuel tank molds and motorcycle helmet molds. Practice has proved that it can also be used as a reference in the production of other blanking molds. The quality and life of the mold are significantly improved, which is greatly convenient and convenient. Meet the needs of production. Therefore, using 7CrSiMnMoV steel flame quenching process instead of CrWMn and Cr12 steel to make large-scale three-dimensional curve molds is a method worthy of popularization.
4. Chemical composition (mass fraction%) C: 0.65~0.75 Si: 0.85~1.15 Mn: 0.65~1.05 P: ≤0.03 S: ≤0.03 Cr: 0.90~1.20 Mo: 0.20~0.50 V: 0.15~0.30
Post time: Oct-13-2021