The quality of the quenched and tempered workpiece is mainly caused by the level of the operator, and there are many reasons for equipment, materials and pre-quenched and tempered processing. The approximate steps should be:
1. The speed at which the workpiece is transferred from the heating furnace to the cooling tank is slow. The temperature of the workpiece's water has dropped below the critical point of Ar3, resulting in partial decomposition, and the workpiece has an incomplete quenched structure, which can not meet the hardness requirements. So small parts need to pay attention to the speed of the coolant, and large parts need to master the time to cool.
2. The quantity of workpiece loading should be reasonable. It is advisable to use 1 ~ 2 layers. The overlapping of workpieces causes uneven heating and uneven hardness.
3. The workpiece should be arranged in a certain distance in the water. Too dense will cause the vapor film near the workpiece to rupture and block, which will cause the hardness of the workpiece approach surface to be low.
4. Opening and quenching, can not be quenched in one breath, depending on the degree of furnace temperature drop, the furnace should be closed and reheated in the middle, so that the hardness of the workpiece before and after quenching is consistent.
5. Pay attention to the temperature of the cooling liquid. If the temperature of 10% brine is higher than 60 ℃, it cannot be used. The coolant must be free of impurities such as oil, mud, etc. Otherwise, there will be insufficient hardness or unevenness.
6. The raw material is hardened and tempered, and the hardness will not be uniform. To obtain good hardened and tempered quality, the blank should be rough turned, and the bar should be forged.
7. The quality is strictly controlled. The hardness after quenching is lower by 1 ~ 3 units. The tempering temperature can be adjusted to meet the hardness requirements. However, the hardness of the workpiece after quenching is too low, and some even only 25 ~ 35HRC. It must be re-quenched. It must not be tempered only at medium or low temperature to achieve the requirements of the drawing. Otherwise, it will lose the significance of tempering and may cause serious problems. s consequence.