Inspection method for quality of forgings

Inspection is divided into appearance quality inspection and quality inspection. The inspection of appearance quality is generally a non-destructive inspection, which can be inspected by the naked eye or a low-magnification magnifying glass, and the method of flaw detection is adopted. As for the internal quality inspection, due to the requirements of its inspection content, some must use destructive inspection, which is commonly referred to as anatomical tests, such as low magnification inspection, fracture inspection, high magnification tissue inspection, chemical composition analysis and mechanical performance testing, etc. Some can also use non-destructive testing methods, and in order to more accurately evaluate the quality of aluminum forgings, destructive testing methods and non-destructive testing methods should be used in combination with each other. In order to analyze the quality problems of forgings from a deep level, the mechanism research work should rely on transmission or scanning electron microscopes, electron probes, etc.

Usually, the inspection methods for the internal quality of aluminum forgings can be summarized as follows: macrostructure inspection method, microstructure inspection method, mechanical property inspection method, chemical composition analysis method and non-destructive testing method.

Macrostructure inspection is a kind of inspection that uses visual or low magnification magnifying glass (generally the magnification is below 30×) to observe and analyze the low magnification structure characteristics of forging. The commonly used methods for macrostructure inspection of forgings are low magnification corrosion method (including hot etching method, cold etching method and electrolytic corrosion method), fracture test method and sulfur printing method.

Low magnification corrosion method is used to check cracks, folds, shrinkage cavities, porosity segregation, white spots, porosity, non-corrosion of forgings of structural steel, stainless steel, superalloy, aluminum and aluminum alloy, magnesium and magnesium alloy, copper alloy, titanium alloy and other materials. Metal inclusions, segregation agglomeration, distribution of streamlines, grain size and distribution, etc. It's just that the etchants and etching specifications used to visualize low-magnification structures are different for different materials.

The fracture test method is used to check the defects such as white spot, lamination and internal crack of structural steel and stainless steel (except austenitic type), to check the graphitic carbon of spring steel forgings and the overheating and overburning of the above-mentioned steels. , magnesium, copper and other alloys are used to check whether the grains are fine and uniform, and whether there are defects such as oxide films and oxide inclusions.

The sulfur printing method is mainly used in large forgings of some structural steels to check whether the distribution of sulfur is uniform and the amount of sulfur content.

Except for the test pieces of structural steel and stainless steel forgings that are used for low magnification inspection, final heat treatment is not carried out, and the forgings of other materials are generally subjected to low magnification inspection after final heat treatment.

Fracture specimens are generally subjected to specified heat treatment.

The microstructure inspection rule is to use an optical microscope to inspect the microstructure of forgings of various material grades. The items to be inspected generally include the essential grain size, or the grain size at a specified temperature, that is, the actual grain size, non-metallic inclusions, microstructures such as decarburized layer, eutectic carbide inhomogeneity, overheating, Overburned structure and other required microstructures, etc.