1. Analysis of the causes of cracks:

1) Uneven temperature: For single-piece production, when the material end enters or leaves the sensor, the temperature of the material end is higher than the middle part due to the strong magnetic field of the inductor. For continuous production, the temperature of the first end of the first material and the end of the last material may also be too high.     

2) Large cooling surface: Three sides of the material end (cylindrical surface, end surface, inner hole) are involved in spray quenching, while only the outer surface of the middle part participates in spray quenching.     

Due to the above reasons, the quenching crack is easily generated at the material end.

1. Measures to prevent cracks

Measure 1 : Add a guide tube at the head of the material and at the end of the material to balance the magnetic field and achieve the purpose of uniform temperature.

Measure 2 : The material end is provided with a detachable protection plate. The protection plate is close to the end surface and is fixed in the inner hole of the steel pipe through the elastic inner expansion type chuck. This protection disk can be used multiple times. Material heat resistant steel.

Measure 3 : The spray device is segmented, and the spray flow and pressure are adjusted in each section to ensure the required cooling rate at the material end.

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