Defects and preventive measures of mold heat treatment
First, quenching The causes and precautions for quenching are as follows: 1, the shape effect, mainly caused by design factors, such as the rounded corner R is too small, the hole position is not properly set, the section transition is not good. 2, overheating (overheating), mainly caused by temperature control is not allowed or running temperature, process setting temperature is too high, furnace temperature is uneven and other factors, preventive measures include maintenance, proofreading temperature control system, correction process temperature, in the workpiece and furnace Add horns between the bottom plates. 3, decarburization, mainly caused by overheating (or over-burning), unheated heating of air furnace, small machine allowance, forging or pre-heat treatment residual decarburization layer and other factors, preventive measures for controlled atmosphere heating, salt bath heating, The vacuum furnace and box furnace adopt packing protection or use anti-oxidation coating; the machining allowance is increased by 2~3mm. 4, improper cooling, mainly due to improper choice of coolant or too cold, should master the quenching medium cooling characteristics or tempering treatment. 5, poor raw material organization, such as serious segregation of carbides, poor forging quality, improper preparation of heat treatment, etc., preventive measures are to use the correct forging process and reasonable preparation of heat treatment system. Second, the hardness is insufficient The reasons for the lack of hardness and preventive measures are as follows: 1. The quenching temperature is too low, mainly due to improper process setting temperature, temperature control system error, improper furnace installation or improper cooling tank method, etc. The process temperature should be corrected, the calibration temperature control system should be repaired, and the workpiece interval should be installed. Place it evenly and evenly into the trough. Do not stack or bundle into the trough to cool. 2. The quenching temperature is too high. This is caused by improper process setting temperature or temperature control system error. The process temperature should be corrected and the temperature control system should be overhauled. 3, over-tempering, this is caused by the tempering temperature setting is too high, the temperature control system fault error or the furnace temperature is too high, the furnace temperature should be corrected, the inspection and temperature control system should be repaired, not higher than the setting furnace temperature In. 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 getting higher and the cooling performance is lower, the stirring is poor or the troughing temperature is too high, etc. Measures: tapping, entering the trough, etc.; grasping the quenching medium Cooling characteristics; oil temperature 60 ~ 80 ° C, water temperature below 30 ° C, when the amount of quenching is large to heat the cooling medium, should be added cooling quenching medium or use other cooling tank cooling; strengthen the stirring of the coolant; at Ms + 50 ° C Take it out. 5, decarburization, which is caused by residual decarburization layer of raw materials or quenching heating, preventive measures for controlled atmosphere heating, salt bath heating, vacuum furnace, box furnace with box protection or use of anti-oxidation coating; The amount is increased by 2 to 3 mm. Next page
The heat treatment of the mold includes preliminary heat treatment, final heat treatment, and surface strengthening treatment. Generally, the heat treatment defect refers to various defects that occur in the final heat treatment process or in the subsequent process, such as quenching, deformation, poor hardness, electric machining cracking, grinding crack, early damage of the mold. Wait. The following is a more detailed analysis.