In the martensitic stainless steel, 3Cr13 high carbon stainless steel, quenching, especially in the oil will have a greater cold stress hardening, the martensite transition temperature and low, easy to produce quenching cracks. Therefore, 3Cr13 steel quenching should be taken to avoid cracks. Adopt the following measures can be limited.
⒈ rough as far as after quenching.
As forging or rolling surface of blank lines may exist, scratches, etc., will be the point of stress concentration quenching and quenching crack incentives. If rough indeed difficult, the available tools such as worn wheel surface defects.
⒉ control quenching speed.
3Cr13 steel plastic poor, poor thermal conductivity. Too fast quenching, the surface temperature and heart Ministry of increase has occurred in the austenite surface layer, the inner layer is still in the low-low temperature plastic state, so that changes in the surface layer became smaller due to contraction of austenite, constrained by the inner layer, resulting in tensile stress, when the pull should be more than material breaking strength of service, that crack. Therefore, can be warm (500 ~ 700 ℃) or in low-temperature control of heating rate is not greater than 80 ℃ / h, 800 ℃ and then improve the heating rate and other methods.
⒊ control the quenching oil cooling oil temperature of the workpiece.
3Cr13 steel alloying elements due to high and low temperature martensitic transformation, if quenching a long time, will increase the quenching quenching cracks resulting from stress, especially in large cross-section parts, and sometimes heart defects in the Ministry of the original surface area of serious organizations, plus the possibility of quenching cracks larger. May be appropriate to slow the cooling rate of the workpiece. Such as control of the workpiece surface when the oil temperature, the general control of transition temperature in the martensite start 150 ~ 200 ℃, or surface temperature is not higher than 50 ~ 80 ℃. For large parts, the center temperature is higher, the heat will transfer to the surface, can use oil - air - oil - air cooled alternate way to slow the hardening stress.
In the high-carbon martensitic steel oil quenching, you should also pay attention to a problem is the proper control of the oil and stir speed. In ensuring the oil temperature is not greater than 80 ℃ and non-fire conditions, do not blindly pursue and increase the cooling effect of the oil, experimental studies have shown that mechanical churning of oil in particular when the quenching capacity will be close to the water quench cooling capacity martensitic stainless steel which is very dangerous. This situation also has been learned.
⒋ tempering after quenching in a timely manner.
Martensitic stainless steel after quenching, the center will continue to martensite transformation occurs, increasing the stress hardening, the workpiece in place during quenching stress distribution will change its ways, the formation of new stress concentration points, which are may quench the workpiece in place during the cracking, so in time after such hardening tempering steel. The workpiece can be cooled to room temperature, or by hand can be a long reach of tempering temperature. Up to no more than 8h after quenching should be tempered, especially in the northern winter, should pay attention to this issue. Such incidents have occurred, in the group of hardened martensitic stainless steel shaft, due to insufficient equipment, failed to temper, but also coincides with the winter, low temperatures, after quenching placed 15h, the results of all the cracking of these axes scrapped.
Please contact with our company service (hotline :0510 -83,632,628) to get more information on stainless steel selection, application, heat treatment and inventory and other related information.
HanChao(Wuxi)Special Steel Co.,Ltd.
Address:Zhongyuan Road,Wuxi,Jiangsu Province,Department of Kennedy International Hardware & Electrical City No.4-4019.