The existence of forging defects, some of which will affect the processing quality or processing quality of subsequent processes, some of which will seriously affect the performance and use of forgings, and even greatly reduce the service life of finished products, endangering safety. Therefore, in order to ensure or improve the quality of forgings, in addition to strengthening the process quality control and taking corresponding measures to eliminate the defects of forgings, necessary quality inspection should also be carried out to prevent the defects of subsequent processes (such as heat treatment, surface treatment and cold treatment) and service performance from entering the subsequent process. After quality inspection, remedial measures can also be taken according to the nature and use degree of defects to meet the technical standards or use requirements.
Therefore, in a sense, the quality inspection of forgings is to check the quality of forgings on the one hand, and to point out the improvement direction of forging process on the other hand, so as to ensure that the quality of forgings meets the requirements of forging technical standards and meet the requirements of design, processing and use.
Forging quality inspection includes appearance quality and internal quality inspection. Appearance quality inspection mainly refers to the geometric dimension, shape, surface condition and other items of forgings; Internal quality inspection mainly refers to the inspection of chemical composition, macrostructure, microstructure and mechanical properties of forgings.
Specifically, the appearance quality inspection of forgings is to check whether the shape and geometric dimensions of forgings conform to the pattern requirements, whether there are defects on the surface of forgings, property defects and their morphological characteristics. The inspection content of surface condition is generally to check whether there are surface cracks, folds, wrinkles, pits, orange peel, blisters, scars, corrosion pits, bumps, foreign objects, unfilled, pits, missing meat, scratches and other defects on the surface of forgings. 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 forgings, but also checking the mechanical properties of forgings, and also analyzing the chemical composition of important parts, key parts or large forgings. For internal defects, we will check whether the forgings have internal cracks, shrinkage holes, looseness, coarse grains, white spots, dendrite crystallization, streamline non-conformity with the appearance, coarse grain ring, streamline oxide film, coarse grain ring, streamline and other defects through low magnification inspection, fracture inspection, high magnification inspection and other methods. Mechanical properties mainly include tensile strength, plasticity, toughness, hardness, fatigue strength, high-temperature instantaneous fracture strength, high-temperature durability strength, plastic resistance and high-temperature creep strength.
Due to the stress, importance, working conditions and conditions, different materials and metallurgical processes of the forged parts after they are made into parts, different departments and different forging classification standards are also different according to the above conditions and department requirements. However, the quality inspection of forgings is inseparable from the appearance quality and internal quality inspection, but the specific inspection items, inspection quantity and inspection requirements are different due to different types of forgings. For example, some industrial departments divide structural steel, stainless steel and heat-resistant steel forgings into four categories, some departments divide aluminum alloy forgings and die forgings into three categories according to their use, and some departments divide aluminum alloy and copper alloy forgings into four categories.