Forged steel parts defect type, name

(1) Class A defects Class A defects are tiny non-metallic inclusions that can be found after machining. The defects are granular and have a size of about 0.2 mm or less. If these particles are not all concentrated, they will have no effect on the strength. However, for bearings and cold-rolled products, such defects are considered to be harmful and should be strictly controlled.
Class A defects are presented in the F waveform during ultrasonic testing; in the dyeing test, they appear as dot marks.
(2) Class B Defects Class B defects are large-size defects, which are generally classified into sand holes, sand inclusions, foreign matter mixed in, etc., which can be seen by the naked eye during rough machining.
1 The blisters are sometimes referred to as cast non-metallic inclusions, and have the same size and shape as the Class A defects, and are distributed along the metal streamline in a single or several forms together.
The sand is also called slag inclusion, and its shape is the same as that of the sand hole, but the size is large, which is a defect that is hardly mixed from the outside when the ingot is ingot.
3 The foreign matter mixed in is a foreign matter that is inadvertently cast into the ingot when the ingot is cast, and the foreign matter can be found by color when machining. However, in the ultrasonic inspection, a waveform indicating a defect is often not seen, and if detected by a dye flaw detection method, the foreign matter is present in a stain shape.
If there is a difference in hardness in the hardness test, it can be discriminated by sulphur print inspection and microscopic observation.
(3) Class C defects
Class C defects are cracks and cracks. Effective means of detecting such defects are ultrasonic flaw detection and stain detection.
1 Shrinkage: A hole-like defect that remains in the center of the ingot without being compacted, usually at the center of the ingot, sometimes at the top of the ingot or at 1/3 of the top. In the ultrasonic flaw detection, it is presented in the form of internal defect waves. However, it should be noted that sometimes the size of the surface is too large, and there is no reflection of the bottom surface.
2 Looseness: When the compaction of the steel ingot is insufficient, it is easy to leave a porous defect in the core. In the ultrasonic flaw detection, it is present in the form of a defect wave.
3 Heterotypic segregation: Heterogeneous segregation can usually be found in the segregation area or inside of steel ingots. With ultrasonic flaw detection, it is easier to detect such defects.
4 Wrinkle: It is a defect caused by overlapping materials in forging, also called interlayer, lamination, and lap joint. Oxide is sometimes mixed in the wrinkles, and it is easier to find such defects by dyeing test or by the naked eye.
5 crack: refers to the defect in the shape of the shell on the surface of the product. This type of crack is shallow and will not have any effect after turning off. This defect is sometimes trapped with scale, which can be seen with the naked eye.
6Over-burning: refers to the phenomenon of grain boundary oxidation caused by overheating. The superfibrated microstructure is coarse and the appearance is crack-like, which can be seen with the naked eye. 7 Quenching crack: refers to cracks generated on the surface or inside due to excessive heating speed during forging heating or heat treatment heating. Such cracks sometimes occur in quenching after heat treatment. The hot cracks are very sharp and can be found by the naked eye.
8 Grinding crack: refers to the micro surface crack that occurs when the quenching part is ground, and its direction is perpendicular to the grinding direction. It is not easy to find with the naked eye, but it can be detected by magnetic particle inspection test and dyeing test.