In order to solve the problem of quench cracking caused by the thin and thick section of the wheel body working face, improvement is mainly achieved through the following three aspects.
(1) Cooling at the thin-walled part of the wheel adopts water cooling to the R-arc in the cooling process at the thin-walled part, ie, during the heating process, so that the cooling rate in the thin part and thick part is consistent as much as possible, and the edge of the thin part is not burned through. The surface from the edge of the face to the warm interior surface maintains the effect of low temperature. The effect of the implementation is that although there is no cracking, the quenching occurs due to insufficient edge temperature.
(2) Change the design dimension of the rough wheel body Thicken the edge thickness of the working surface and increase the transition radius. After the heat treatment, the increased portion was reprocessed as shown in FIG. Figure 7 shows the effect of the rough wheel body size improvement, heat treatment process and cutting results. From the cutting results, it can be seen that the improved rough wheel body blank is heat treated and then cut, its outer surface is hardened, and its surface hardness is 53-55HRC. The hardness of the inner surface is 22 to 35HRC, which does not affect the processing. However, only some of the samples pass the MT test, but the crack rate is significantly reduced to 36%. If the thickening of the thin wall is continued, although the crack can be reduced, the corresponding cost and internal processing efficiency are reduced.
(3) Changing the sensor design Although changing the size of the rough wheel body can reduce the crack rate, it is not completely eliminated, and it also increases the billet cost and affects the processing efficiency. Therefore, it is hoped that the purpose of eliminating such cracks can be achieved by redesigning the sensor. .
After analysis, it can be known that the original wall sensor has the same gap between the wall thickness and the wall thickness of the working surface. When the induction heating is applied, the thin wall will be overheated. However, the wall thickness will not be heated enough to make the transition area resistant to cooling. The R-arc portion of the R-arc due to the large time difference in martensitic transformation forms a large amount of tissue stress, resulting in cracks. Since the larger the gap, the more the leakage flux and the smaller the bulk density of the magnetic field energy, in order to solve this crack problem caused by the uneven thickness of the working surface, the most commonly used method is to increase the wall appropriately according to experience. The thin space gap is made larger than the gap at the wall thickness, thereby suppressing the overheating of the thin wall. We empirically used a trapezoidal inductor (two copper tubes staggered) instead of the original straight wall (single copper tube) inductor. Using a trapezoidal inductor can increase the distance from the weak point, thereby reducing the heat input and balancing the phase transition time. , Reduce tissue stress and solve this crack problem. After several test cuts, the results are satisfactory. As shown in Figure 9 and Table 2, the heat treatment requirements are met and the crack rate is successfully reduced to zero.
