How can we prevent the defects that occur when cold rolling work rolls are quenched using ultrasonic induction quenching equipment?

Cold rolling work rolls require quenching heat treatment to improve their hardness, wear resistance and service life. However, since the cold rolling work roll is affected by the limitations of the equipment itself, natural factors such as weather and temperature, and some human factors during quenching, some defects will inevitably occur. So, what defects will the ultrasonic induction quenching power supply produce when quenching heat treatment of cold rolling work rolls?

1. The soft belt at the upper end of the rolling body is too wide, which is caused by the premature power outage of the sensor and the stop position of the sensor being too low. We just need to raise the sensor power-off position and stop position.

2. The soft spot at the lower end of the rolling body is too wide, mainly because the starting position of the sensor is too high or the water supply is too late. Therefore, we should lower the position of the sensor or provide water in advance.

3. Reasons for uneven hardness after quenching:

(1) The sensor, water sprayer and roller are not concentric. We need to adjust the positions of the sensor and water sprayer.

(2) The sprinkler returns water or is clogged. For this reason, we should reduce the water pressure or change the angle of the water spray.

4. The upper edge of the rolling body falls off (the edge falls off). The reason for this defect is that the sensor power-off is too late or the sensor stop position is too high. Therefore, we should lower the sensor power-off position and stop position.

5. Quenching deformation and cracking. This is a common defect of the workpiece during the quenching process. The main reasons for this defect are:

(1) Improper forging process, forging must be carried out strictly in accordance with process parameters.

(2) During quenching, the temperature difference between the surface and the core is too large, resulting in internal stress. We should choose materials correctly and try to use materials with less tendency to deform and crack.

(3) The quality of raw materials is poor and the hydrogen content exceeds the standard. When selecting materials, we should select materials that meet the requirements and perform sufficient dehydrogenation treatment to avoid excessive hydrogen content.

(4) Oxidative decarburization occurs during the heating process and tempering is not timely. Tempering should be performed immediately after quenching.

(5) The quenching temperature is too high, the heating speed is too fast, the holding time is too long, and the cooling is too intense. Therefore, when quenching the workpiece, the quenching process parameters should be optimized, and the cooling medium should be fully preheated and selected.

6. The hardness after quenching is low. The purpose of quenching is to improve the hardness of the workpiece itself. The reasons for the low hardness are as follows:

(1) Steel has poor hardenability. When selecting materials, materials with good hardenability should be used.

(2) There is too much retained austenite. We should choose a medium with good cooling performance to reduce the retained austenite or increase the tempering temperature.

(3) The quenching temperature is low. We can avoid low hardness after quenching by adjusting the voltage or mechanical parameters to increase the quenching heating temperature.

(4) The quenching water pressure is low, the water volume is not enough, and the cooling speed is not enough. We should increase the water pressure or water temperature to increase the cooling speed.

(5) Surface decarburization. In view of the low hardness defect caused by surface decarburization, we should choose materials that meet the requirements.    

I would like to share with you the defects that occur when the cold press work roll is quenched and heat treated with ultrasonic induction quenching equipment. If you want to know more information, please call our hotline for more detailed information.