time：2020-04-01 source：小编 Views：248
The inspection of forging quality is divided into the inspection of appearance quality and the inspection of internal quality. The inspection of appearance quality is generally a non-destructive inspection, which can be inspected through the naked eye or a low magnifying glass, and if necessary, non-destructive testing is also used. Due to the requirements of the inspection content, some of the internal quality inspections must use destructive inspections, which are commonly referred to as anatomical tests, such as low-magnification inspection, fracture inspection, high-magnification tissue inspection, chemical composition analysis, and mechanical property testing. Some can also use non-destructive testing methods, and in order to evaluate the quality of forgings more accurately, 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 at a deep level, the mechanism of research work must also be aided by transmission or scanning electron microscopes and electron probes.
Generally, the inspection methods of internal quality of forgings can be summarized as: macrostructure inspection method, microstructure inspection method, mechanical property inspection, chemical composition analysis method and nondestructive testing method.
Macrostructure inspection is a kind of inspection that uses visual inspection or low magnification magnifier (generally multiple is below 30×) to observe and analyze the characteristics of low magnification structure of forging. The commonly used methods for macrostructure inspection of forgings are low-power corrosion method (including thermal corrosion method, cold corrosion method and electrolytic corrosion method), fracture test method and sulfur printing method.
The low-magnification corrosion method is used to inspect forgings such as structural steel, stainless steel, high-temperature alloys, aluminum and aluminum alloys, magnesium and magnesium alloys, copper alloys, titanium alloys and other forgings, folding, shrinkage, pore segregation, white spots, looseness, non- Metal inclusions, segregation and aggregation, streamline distribution, grain size and distribution, etc. It's just that the etchant and etching specifications used for different materials to show low-magnification structures are different.
The fracture test method is used to check the white spots, layering, internal cracks and other defects of structural steel and stainless steel (except austenitic type), check the graphite carbon of spring steel forgings and the overheating and overburning of the above steel types. For aluminum , Magnesium, copper and other alloys are used to check whether the grains are fine and uniform, whether there are defects such as oxide film and oxide inclusions.
The sulfur printing method is mainly used for large forgings of certain structural steels to check whether the sulfur distribution is uniform and how much sulfur content.
Except that the test pieces for structural steel and stainless steel forgings used for low magnification inspection do not undergo final heat treatment, the forgings of other materials generally undergo low magnification inspection after final heat treatment.
Fractured specimens are generally subjected to prescribed heat treatment.
The microstructure inspection rule is to use an optical microscope to check the microstructure of various materials and forgings. The inspection items generally have intrinsic grain size, or grain size at a specified temperature, that is, actual grain size, non-metallic inclusions, microstructures such as decarburized layer, eutectic carbide unevenness, overheating, Burnt tissues and other required microstructures.