The heat treatment of wear-resistant plate includes preliminary heat treatment, final heat treatment and surface strengthening treatment. Generally, heat treatment defects refer to various defects of wear-resistant plates in the final heat treatment process or in later processes and in the use process, such as quenching cracking, deformation aberration, insufficient hardness, electric machining cracking, grinding cracks, early damage of wear-resistant plates, etc. The following is a detailed explanation of the quenching and hardness deficiency.
The causes and preventive measures of quenching cracking are as follows:
(1) The shape effect is mainly caused by design factors, such as too small rounded corner R, improper hole position setting, and poor cross section transition.
(2) overheating (overburning), mainly caused by temperature control is not allowed or running temperature, process setting temperature is too high, furnace temperature inequality factors, preventive measures include maintenance, proofreading temperature control system, correction of process temperature, between the workpiece and the furnace bottom plate pad iron, etc.
(3) Decarbonization, mainly caused by overheating (or overburning), air furnace without protection heating, small machine allowance, forging or preparation of heat treatment residual decarbonization layer and other factors, preventive measures for controlled atmosphere heating, salt bath heating, vacuum furnace, box furnace protection or use of anti-oxidation paint; Machining allowance increased by 2~3mm.
(4) Improper cooling, mainly caused by improper coolant selection or supercooling, should master the cooling characteristics of the quenching medium or tempering treatment.
(5) wear-resistant plates are poorly organized, such as serious carbide segregation, poor forging quality, improper preparation heat treatment methods, etc. Preventive measures are to use the correct forging process and reasonable preparation heat treatment system.
The causes and preventive measures of insufficient hardness are as follows:
1) The quenching temperature is too low, mainly due to improper process setting temperature, temperature control system error, furnace loading or entering the cooling tank method is improper, should be corrected process temperature, overhaul and check the temperature control system, when loading the furnace, the workpiece spacing is reasonably placed evenly, dispersed into the tank, prohibit stacking or bundle into the tank cooling.
2) The quenching temperature is too high, which is caused by improper process setting temperature or temperature control system error, the process temperature should be corrected, overhaul and check the temperature control system.
3) Over-tempering, which is caused by the tempering temperature setting is too high, the temperature control system fault error or the furnace temperature is too high into the furnace, should be corrected process temperature, overhaul and check the temperature control system, not higher than the set furnace temperature loading.
4) Improper cooling, the reason is that the pre-cooling time is too long, the cooling medium is improperly selected, the quenching medium temperature is gradually higher and the cooling performance is decreased, the mixing is poor or the temperature of the tank is too high, measures: the oven, into the tank, etc., should be fast; Master the cooling characteristics of quenching medium; Oil temperature 60~80℃, water temperature below 30℃, when the quenching amount is large and the cooling medium heats up, the cooling quenching medium should be added or other cooling tank cooling; Strengthen the mixing of coolant; Remove at Ms+50℃.
5) Decarbonization, which is caused by the residual decarbonization layer of raw materials or quenching heating, preventive measures for controlled atmosphere heating, salt bath heating, vacuum furnace, box furnace protection or use of anti-oxidation paint; Machining allowance increased by 2~3mm.
