The causes and preventive measures of spring crack are as follows
1. The shape effect is mainly caused by design factors, such as too small fillet R, improper hole position setting and poor section transition. 2. Overheat (over burning) is mainly caused by inaccurate or running temperature control, too high process setting temperature and uneven furnace temperature. Preventive measures include maintenance and calibration of temperature control system, correction of process temperature, and iron pad between workpiece and furnace bottom plate. 3. Decarburization is mainly caused by overheating (or over burning), unprotected heating of air furnace, small machining allowance, residual decarburization layer in forging or preparation heat treatment. The preventive measures are controlled atmosphere heating, salt bath heating, and packing protection for vacuum furnace and box furnace
1. The shape effect is mainly caused by design factors, such as too small fillet R, improper hole position setting and poor section transition.
2. Overheat (over burning) is mainly caused by inaccurate or running temperature control, too high process setting temperature and uneven furnace temperature. Preventive measures include maintenance and calibration of temperature control system, correction of process temperature, and iron pad between workpiece and furnace bottom plate.
3. Decarburization is mainly caused by overheating (or over burning), unprotected heating of air furnace, small machining allowance, residual decarburization layer in forging or preparation heat treatment. The preventive measures are controlled atmosphere heating, salt bath heating, packing protection or anti-oxidation coating for vacuum furnace and box furnace, and increase machining allowance by 2-3mm.
4. Improper cooling is mainly caused by improper selection of coolant or supercooling. Therefore, the cooling characteristics of quenching medium or tempering treatment should be mastered.
5. Raw materials with poor microstructure, such as serious carbide segregation, poor forging quality, improper preparation heat treatment method, etc., the preventive measures are to adopt correct forging process and reasonable preparation heat treatment system.