Common defects and preventive measures of spindle induction heating surface quenching

1. The reasons for uneven heating are:

① The gap between the sensor and the workpiece is uneven. ② The coaxiality of the quenching machine tool core axis is poor, and the deviation is large during rotation.

Solutions: ① Adjust the gap and make it even on all sides ② Improve the coaxiality of the mandrel, straighten or replace it.

2. Reasons for insufficient hardness after quenching: ① Low heating temperature ② Thick original tissue ③ Low cooling rate, insufficient water volume, large distance between sensor and water distributor ④ Slow cooling operation, failure to cool in time after heating.

Solutions: ① Heating at normal temperature ② Increase preparatory heat treatment to refine the structure ③ Increase water volume, increase cooling speed, adjust the distance between sensor and water sprayer. ④ Increase operating speed

3. Cracks after induction annealing and quenching: ① It may be that the carbon content of the material is too high. ② The heating temperature is too high. The material contains continuously distributed inclusions. Heating causes internal stress, which mostly occurs at sharp corners, keyways, and round hole edges. The cooling rate is too high and secondary quenching is required.

Solution: ① Selected steel should be used for No. 45 steel, and high carbon steel should be spheroidized annealed. ②Choose a lower annealing temperature, high-temperature normalizing or change materials, retain 2-8mm non-hardened area, reduce water pressure, increase water temperature, shorten water spray time, alloy steel can use water spray time instead, alloy steel can use water spray time instead. Spray emulsion, polyvinyl alcohol, 903 or oil cooling. Before secondary quenching, induction heating is used to heat to 750-700 degrees Celsius, and then quenched according to specifications after air cooling.

4. Reasons for deformation after induction annealing and quenching: ① uneven distribution of hardened layer of shaft parts ② tooth shape deformation and inner hole shrinkage of gear parts

Countermeasures: ① Rotate the workpiece during heating, and the deflection of the quenching machine tool spindle should be small. ② Use larger specific power, shorten heating time, select appropriate cooling method and cooling medium, and rationally design and process routes.