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The defects such as cracks, pores, shrinkage cavities and inclusions inside the forging can be detected by nondestructive testing. The macro structure inside the forging needs to be observed and analyzed by dissecting the typical cross section of the forging randomly selected. The low-power inspection of forgings refers to the inspection of the structure of the forged part with the naked eye or with the help of 10-30 times magnifying glass, so it is also called macro structure inspection. The main methods are: acid etching, sulfur printing and fracture. Let's take a look with the small braid of the rear axle half shaft sleeve!

1. Acid corrosion inspection: cut the sample on the cross section of the forging to be inspected. After acid corrosion, the macro structure and defects of the cross section can be clearly displayed.

2. Sulfur trace inspection: sample cutting and inspection surface treatment are basically the same as acid etching inspection. It uses the functions of photographic paper and sulfide to check the distribution of sulfide in steel, and can also indirectly judge the distribution of other elements in steel.

3. Fracture inspection: defects in raw materials of the forging itself, or defects caused by heating, forging and heat treatment can be found. Or fatigue cracks caused by parts in use.

4. Microstructure inspection of Forgings: microstructure inspection is to inspect the internal structure and micro defects of forgings under optical microscope. Therefore, the sample is representative.

5. Ultrasonic wave has strong penetration ability, which can penetrate several meters or even ten meters thick metal. Compared with other nondestructive testing methods, ultrasonic inspection of internal defects of forgings is simpler and faster, and the shape, position and size of defects can be found. However, it is not easy to judge the nature of defects. It needs to cooperate with other methods or accumulate rich experience for reasoning and comparison to draw a conclusion.