Several common forms of quenching cracks after the workpiece is quenched using medium frequency induction heating equipment

After the workpiece is quenched using medium frequency induction heating equipment, common quenching cracks come in many forms, examples of which are as follows:

1) The automobile brake shoe is made of ferrite malleable cast iron. Its 40mm*50mm plane will produce quenching cracks after being induction quenched by medium frequency heating equipment. When cracks occur on this surface, it will also be distorted into a convex surface. Use a flat surface to grind the surface. , the original crack is near the bright area at the highest point of the convex surface.

2) The automobile kingpin was originally quenched by a one-time heating method. It did not rotate during heating, and the cracks in the hardened area also bulged in the shape of small dots. Later, this piece was changed to rotational heating and quenching. Due to uniform cooling, the cracks were eliminated.

3) Circumferential cracks occur in the boundary transition zone of the crankshaft journal quenching zone. When the opening and closing inductor does not rotate to heat the crankshaft journal, circumferential cracks will sometimes occur in the boundary transition zone. The reason is related to the tensile stress at the boundary and the intense cooling. The quenching cooling medium squeezes out at the steps at both ends of the effective ring, and the flow rate Accelerate, resulting in increased cooling rate.

4) When using medium frequency induction heating equipment for quenching, cracks are likely to occur on the tooth top and tooth surface. The reason is that when the current frequency is higher than the optimal value, the tooth top temperature is too high, and when cooling with liquid spray, the tooth top and two tooth sides When three sides are cold, that part will cool faster, so that part is most susceptible to quenching and cracking. When scanning single tooth quenching, the tooth end that is heated last is also the most susceptible to cracking.

5) After scanning quenching of the shaft, there is residual tensile stress at the edge of the quenching area. When measured with a dial indicator, the diameter there is slightly expanded. After the spline shaft is scanned and quenched, the edge transition section also expands, which sometimes affects the insertion of the inspection ring gauge.