The existence of forging defects will affect the processing quality or processing quality of the subsequent process, and some will seriously affect the performance and use of the forgings, and even greatly reduce the service life of the finished products and endanger the safety. Therefore, in order to ensure or improve the quality of forgings, in addition to strengthening quality control in the process and taking corresponding measures to eliminate the occurrence of forging defects, necessary quality inspections should also be carried out to prevent subsequent processes (such as heat treatment, surface treatment, cold working) And the defective forgings that have a bad influence on the performance will flow into the subsequent process.
After the quality inspection, remedial measures can also be taken for the forgings according to the nature of the defects and the degree of influence on the use, so that they meet the technical standards or the requirements of use. Therefore, in a sense, the quality inspection of forgings is to check the quality of the forgings on the one hand, and to point out the direction of improvement for the forging process on the other hand, so as to ensure that the quality of the forgings meets the requirements of the technical standards for forgings and meets the requirements of design, Processing and use requirements.
The inspection of forging quality includes the inspection of appearance quality and internal quality. The appearance quality inspection mainly refers to the inspection of the geometric dimensions, shape, and surface condition of the forgings; the internal quality inspection mainly refers to the inspection of the chemical composition, microscopic structure, microstructure, and mechanical properties of the forgings.
Specifically, the appearance quality inspection of forgings is to check whether the shape and geometric dimensions of the forgings meet the requirements of the drawings, whether the surface of the forgings is defective, what kind of defects are, and what are their morphological characteristics. The inspection content of the surface condition is generally to check whether the surface of the forging has surface cracks, folds, wrinkles, pressure pits, orange peel, blisters, scars, corrosion pits, bumps, foreign objects, underfill, pits, lack of meat, etc.
Defects such as scratches. The internal quality inspection is to check the internal quality of the forging itself, which is a quality condition that cannot be found by the appearance quality inspection. It includes not only checking the internal defects of the forging but also checking the mechanical properties of the forging. Pieces or large forgings should also be analyzed for chemical composition.
For internal defects, we will use low magnification inspection, fracture inspection, and high magnification inspection to check whether there are internal cracks, shrinkage holes, porosity, coarse grains, white spots, dendrites, streamlines that do not conform to the shape, Streamline disorder, flow-through, coarse grain ring, oxide film, delamination, overheating, overburning structure and other defects. For mechanical properties, it is mainly to check the tensile strength at room temperature, plasticity, toughness, hardness, fatigue strength, high-temperature instantaneous rupture strength, high-temperature permanent strength, permanent plasticity, and high temperature creep strength.
After the forgings are made into parts, their stress, importance, and working conditions are different during use, and the materials and metallurgical processes used are also different. Therefore, different departments classify the forgings according to the above conditions and the requirements of the department. , Different departments and different standards classify forgings differently.
