The reasons for the hardness of the induction quenching tandem fail to meet the technical requirements are many aspects.
1. The quenching temperature is insufficient, which is insufficient, and does not reach the austenite temperature requirements. For the medium-carbon structure steel, there is an unlenerated ferritic body in the austenite, and there is a unlearable iron body in the quenching tissue, and the quenching surface of the workpiece is often blue. As can be seen from the appearance of induction quenching, normal quenching surface is beige, and the superheated surface is white.
2. The cooling speed is below the critical cooling rate. In addition to some martensite in the quenching tissue, there is also a hit, the greater the amount of the hit, the lower the hardness. It often occurs when the quench cooling medium concentration, temperature, pressure fluctuation and spray liquid blocker are often occurred.
3. The self-tempering temperature is too high in the shaft scanning quenching, which is generally the horizontal axis quenching or step-shaped axis vertical quenching. When the spray is large, the heating surface quickly passes through the spray segment, and the water flow is blocked due to the step (large diameter segment, the small diameter segment is below), and cannot continue to cool the quenched section. Therefore, the quenching surface is often observed and the obvious self-recovery temperature is too high.
4. Soft point or spiral black tape quenching surface, you often have black, typical spiral black belt is a common defect in the quenching quenching. This black belt is also a soft belt, often a hit organization. The method solution is that the spray is to be uniform, and the workpiece speed can also reduce the pitch of the black strap, but the substantially the structure of the spray is uniform to cool the heating surface. The spray hole clog is one of the reasons for the soft spot.
5. The impact of material components, especially carbon content, and is one of the hardness reduction factors. It is necessary to use a selected carbon content to be used to reduce the upper and lower limits of W (c) to 0.05% when necessary.
6. Preparatory heat treatment condition regulation process change, the black skin of the rolling material is also the reason for the hardness of the induction quenching tandem.
7. Surface decarburization, lean carbon often occurs on the surface of the cold taking, so the detection hardness of these bar is quenched, and the external layer can be removed first 0.5 mm to detect the hardness. If the surface hardness is low, the inner layer is higher than the surface, indicating that the poor carbon layer is present (special geometric shape such as a tonar tip, the top of the gear)
8. Stripped tissue in the original tissue of the ribbon raw tissue causes the hardness of the quenching. There is an unleverated iron body in the belt tissue, and it is not possible to dissolve during the austenite process. The hardness is not enough after quenching. Even if the belt tissue is also difficult to eliminate even if heating temperatures increase.