Do you know how to conduct quality inspection after quenching the nickel-chromium-molybdenum alloy cast iron tappet? How to prevent defects?

Heat treatment is an important way to make workpieces meet process requirements. The purpose of heat treatment is to improve the hardness, toughness and other performance requirements of the workpiece. When the workpiece is heat treated, just like when we do our homework, errors will occur and defects will occur. This requires us to conduct quality inspections on the heat treatment of the workpiece. When defects are discovered, we must quickly find ways to prevent them.

Heat treatment quality inspection items and methods for nickel-chromium-molybdenum alloy cast iron tappets:

1. Microstructure. The way to check the microstructure is to take at least one sample from each furnace for metallographic structure inspection. During metallographic inspection, grade 6 carbides are allowed to appear within the range of 2.6-8.5mm from the end face. There are many other requirements, such as no decarburization or oxidation allowed on the surface of heat-treated parts, and the body structure should be martensite, etc.

2. Hardness. We often use HRC to express hardness. To check the hardness, we need to measure it on the end face, select at least three points, and measure it after quenching at 58-65.

The purpose of quality inspection is to detect and fill deficiencies. Common defects include:

1. Overheating is caused by the heating temperature being too high. This defect cannot be remedied. When we perform heat treatment of workpieces, we should strictly control the quenching heating temperature to avoid overheating.

2. Low hardness. This is a relatively common defect. The cause is low heating temperature or insufficient holding time. To address this defect, we can only reheat and quench.

3. Quenching soft spots are caused by dirty quenched parts or too high quenching oil temperature. Therefore, before heat treatment, we should clean the parts to ensure that the parts are clean and ensure that the oil temperature is appropriate during quenching.

4. Surface decarburization. Surface decarburization is mainly caused by the heating temperature of the workpiece being too high or the carbon potential of the furnace gas being too low. Our quenching heating should be carried out in a protective atmosphere or the heating temperature should be appropriately reduced.

Heat treatment quality inspection of nickel-chromium-molybdenum alloy cast iron tappets and some knowledge about common defects. These are just some of our own insights. We hope it will be helpful to your work. If you have any questions in this regard, you can call our hotline.