Cr12MoV heat treatment knowledge
Cr12MoV steel is a high-carbon high-chromium austenitic steel, commonly used in cold work die, carbon content lower than Cr12 steel. The steel has high hardenability, cross-section can be completely hardened 300mm below the quenching volume change than Cr12 steel to be small. The heat treatment system: steel bars and forgings 960 ℃ air + 700 ~ 720 ℃ tempering, air cooling. The final heat treatment process: 1, quenching:
The first preheating: 300 ~ 500 ℃, the second preheating 840 ~ 860 ℃; Quenching temperature: 1020 ~ 1040 ℃;
Cooling medium: oil, medium temperature: 20 ~ 60 ℃, cooled to oil temperature; followed by air cooling, HRC = 60 ~ 63. 2, tempering:
After the following quenching process, you can achieve the role of reducing the hardness, the specific tempering process is as follows: Heating temperature 400 ~ 425 ℃, get HRC = 57 ~ 59.
Description: tempering between 480 - 520 degrees is just the brittle tempering of steel such areas, tempering in this area prone to chipping die. The best tempering interval 380 - 400 ℃, tempering this range, the best toughness, and have good wear resistance. If quenched, cryogenic treatment (ideal temperature is minus 120) in combination with tempered tempering, will get good results and high life expectancy. Cr12MoV temper brittleness temperature range of 325 ~ 375 ℃. CR12MoV380-400 after tempering the hardness of 56-58HRC do punch punching toughness good material has the advantage of not easy to crack, especially in the case of raw material quality is not very good, with this method is affordable. Cr12MoV classification quenching process:
850 degrees preheat -1050 degrees heat -620 degrees grading, the time is generally 2-3 minutes - oil cooling to about 200 degrees - (also 260 degrees bainite isothermal) -520 tempering 2-3 times, each time 2 hours. Hardness of about 56-61HRC.
Cr12Mov heat treatment HRC60 split open solution: analysis process
1 material composition
2 material original organization
3 workpiece flow
4 heat treatment process
5 cracked photo
6 workpiece size
Can not say hardness 60HRC will crack. Cracking a lot of reasons, you can refer to the instructions of Geng workers one by one check. If it is quenched on the direct cracking may have the following reasons:
1) wrong material heat treatment process is not appropriate.
2) Improper cooling, rapid cooling below the Ms temperature, excessive stress.
3) the workpiece cross-sectional size difference is too large, or a lot of holes, or there is stress concentration.
4) quenching heating temperature is too high, coarse grains, large brittleness. Over-burning grain boundary oxidation or melting.
5) The workpiece is not preheated, the heating rate is too large caused by heating cracking.
6) poor original organization, the existence of raw materials, mesh eutectic carbide or spheroidizing annealing, or raw materials have micro-cracks, quenching cracks crack.
7) No intermediate annealing before repeated quenching.
8) Not quenched after tempering.
1050 quenching, with an isothermal 260-280 bainite, die toughness will be greatly improved, and will not crack.
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