The reason of insufficient hardness in quenching process and the preventive measures

In the process of production, can appear sometimes strain, insufficient hardness after fire. This is in the process of heat treatment quenching 'common defects. 'Insufficient hardness' sometimes for the whole workpiece hardness value is low, sometimes is not enough local hardness or producing soft point. Quenching hardness is insufficient for many reasons, and raw materials, heating process, cooling medium, the cooling method, and tempering temperature and so on have close relationship. Once appeared in the production of this kind of situation, must be specifically analyzed, and then on to the topic, properly handled. Just below the factory often, talk about my opinion. 1, furnace, or enter the causes such as improper cooling slot method, should be temperature correction technology, maintenance check temperature control system, furnace charging, interval put evenly, reasonable scattered into the slot, accumulation or bundles into the groove cooling is prohibited. 2, quenching temperature is too high, which is set by process temperature improper or system error caused by temperature control, temperature shall be revised process, maintenance check temperature control system. 3, tempering, and this is set by the tempering temperature is too high, the temperature control system fault errors or high temperature when charging, shall be temperature correction technology, maintenance check temperature control system, not higher than the set temperature loading. 4, cooling, the reason is the precooling time is too long, incorrect cooling medium, quenching medium temperature increasing and cooling performance degradation, stir adverse or out of the tank temperature too high, measures: come, into the trough, etc; Master the quenching cooling medium characteristics; Oil temperature 60 ~ 80 ℃, the water temperature below 30 ℃, when large amount of quenching and cooling medium heat up, should add cooling quenching medium or switch to other cooling groove cooling; Strengthen the coolant mixing; When Ms + 50 ℃. 5, decarburization, this is caused by raw material residual decarburization layer or quenching heating, the preventive measures for the controlled atmosphere heat, salt bath heating, vacuum furnace, box-type furnace adopts packing protection or use the anti-oxidation coatings; Machining allowance increase 2 ~ 3 mm.