Tips on mold hardness defects and preventive measures!

Tips on mold hardness defects and preventive measures!

The use of molds is very extensive now. In order to improve the performance of mold manufacturing process, the mold is usually heat treated. Common defects in heat treatment molds include: quenching cracks, deformation tolerance, insufficient hardness, electrical machining cracking, grinding cracks, early damage to molds, etc. It can be seen that insufficient mold hardness is one of the common defect types.

What are the causes and preventive measures for mold defects?

There are mainly five aspects:

1. The quenching temperature is too low, which is mainly caused by improper process setting temperature, temperature control system error, improper furnace loading or cooling tank method, etc. The process temperature should be corrected, the temperature control system should be inspected and checked, and the workpieces should be reasonably placed and evenly spaced when loading the furnace. They should be dispersed into the tank. It is forbidden to stack or bundle into the tank for 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, and the temperature control system photoelectric tooth axis should be inspected and checked.

3. Over-tempering: This is caused by too high a tempering temperature, a temperature control system fault error, or the furnace temperature being too high. The process temperature should be corrected, the temperature control system should be inspected and checked, and the temperature should not be higher than the set furnace temperature.

4. Improper cooling: The reasons are too long pre-cooling time, improper selection of cooling medium, gradually increasing quenching medium temperature and decreased cooling performance, poor stirring, or too high out-of-tank temperature. Measures: fast out-of-tank, tank entry, etc.; master the cooling characteristics of the quenching medium; oil temperature 60~80℃, water temperature below 30℃. When the quenching amount is large and the cooling medium heats up, add cooling quenching medium or use other cooling tanks for cooling; strengthen the stirring of the coolant; remove the threaded grinding insert at Ms+50℃.

5. Decarburization: This is caused by the residual decarburization layer of the raw material or quenching heating. The preventive measures are controlled atmosphere heating, salt bath heating, vacuum furnace and box furnace use box protection or use anti-oxidation coating; increase the machining allowance by 2~3mm.