Hub shaft induction heating and heat treatment process part 3: hub shaft induction heat treatment result detection
1. Quenching macroscopic morphology
After non-destructive testing by magnetic powder, the parts after induction heat treatment were dissected and sampled after no quenching defects were found. The macroscopic quenching morphology was shown in Figure 5, and the axial quenching length was 118mm. The circumferential quenching diameter is 111mm, which meets the requirement of the quenching area in the technical requirements of the hub and shaft pipe.
2. Hardness test
Hardness value test directly on the wheel shaft, macro inspection, due to quenching area is large, in order to guarantee the real full of hardness value detection, thus to determine the hardness testing area A, B, C, D, E, F, A total of six points (see figure 5), hardness value test results as shown in table 3, hardness value meets the technical requirements of surface hardness 50 ~ 64 HRC.
FIG. 5 Macroscopic morphology sample of hub shaft quenching region
3. Depth of hardening layer
Induction heat treatment hardening layer depth can use a metallographic method or the hardness method, the test the hardness method (critical hardness 45 HRC), due to the wheel shaft belongs to the variable cross-section shaft, its position by the depth of hardening layer is also different, choose a, b, c, d, e, f, g, h layer depth, a total of eight points of testing (see figure 5), the depth of hardening layer test results as shown in table 4, meet the effective hardening layer depth of hardening layer 4 ~ 7 mm technical requirements.
4. Metallographic microstructure and grading
The metallographic structure was tested according to standard JB/T 9204-2008. The metallographic microstructure was tempered martensite, as shown in FIG. 6. The grade was 4 ~ 6, meeting the technical requirements.
FIG. 6 Metallographic microstructure of hub shaft by induction heat treatment
Conclusion
(1) The testing results of quenching morphology, hardness, depth of hardening layer, metallographic microstructure, and microstructure grading of the hub shaft meet the technical requirements.
(2) The qualified test results show that the inductor design in the early stage is reasonable, and the induction heat treatment process debugging and process parameter selection is correct.
(3) The induction heat treatment process of the hub shaft has been pushed into mass production, and so far no quenching quality problems have occurred. Similar products in the development process of induction heat treatment can refer to the design principles of inductors in this paper and the selection of process parameters.