Methods for quality inspection of the hottest forg

2022-08-07
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Forging quality inspection methods

in today's era, people have higher requirements for the use of products, and correspondingly put forward higher requirements for the forgings of manufactured products. However, there are many forms of forging quality problems. Some types of forging defects will seriously reduce the performance of forgings, threaten the safety and reliability of use, and shorten the service life. The consequences of the existence of such defects are serious. Therefore, higher requirements are put forward for the quality inspection of forgings, that is, forgings with defects must not be left behind, especially those with defects that seriously affect the service performance. To achieve this, we should not only fully use the conventional inspection methods and means, but also adopt the faster and more accurate inspection methods and methods that reflect the contemporary level of an exciting news when inspecting and controlling the quality of forgings, so as to make the evaluation of the quality of forgings, the judgment of the nature of forgings' defects, the judgment of causes and the analysis of formation mechanism more accurate and more realistic, So as to ensure that the defective forgings are not missed, and appropriate solutions can be taken to improve and improve the quality of forgings

as mentioned above, the quality inspection of forgings is divided into appearance quality inspection and internal quality inspection. Generally speaking, the inspection of appearance quality is a non-destructive inspection, which is usually carried out with the naked eye or a low power magnifying glass. If necessary, the nondestructive testing method is also adopted. For internal quality inspection, due to the requirements of inspection contents, some must adopt destructive inspection, that is, commonly referred to as anatomical test, such as low magnification inspection, fracture inspection, high magnification structure inspection, chemical composition analysis and mechanical property test, and some can also adopt nondestructive inspection methods. In order to more accurately evaluate the quality of forgings, Destructive testing methods shall be combined with nondestructive testing methods. In order to analyze the quality problems of forgings from a deep level, the research on mechanism should also be assisted by transmission or scanning electron microscope, electron probe, etc

generally, the inspection methods for internal quality of forgings can be summarized as follows: macro structure inspection, micro structure inspection, mechanical property inspection, chemical composition analysis and nondestructive testing

macroscopic examination is to use visual inspection or low power magnifying glass (generally the multiple is 30 × Below) to observe and analyze the macrostructure characteristics of forging. The commonly used methods for macro structure inspection of forgings are low magnification corrosion method (including hot corrosion method, cold corrosion method and electrolytic corrosion method), fracture test method and sulfur printing method

low power corrosion method is used to inspect the cracks, folds, shrinkage cavities, pore segregation, white spots, porosity, non-metallic inclusions, segregation concentration, streamline distribution, grain size and distribution of forgings made of structural steel, stainless steel, high-temperature alloy, aluminum and aluminum alloy, magnesium and magnesium alloy, copper alloy, titanium alloy and other materials. However, for different materials, different etchants and etching specifications are used to show macrostructure

the fracture test method is used to check the defects such as white spots, laminations and internal cracks of structural steel and stainless steel (except austenite type), the graphite carbon of spring steel forgings and the overheating and Overburning of the above steel types. For aluminum, magnesium, copper and other alloys, it is used to check whether the grains are fine and uniform, and whether there are defects such as oxide films and oxide inclusions

the sulfur stamp method is mainly applied to the large forgings of some structural steels to check whether the sulfur distribution is uniform and the sulfur content

except that the test pieces of structural steel and stainless steel forgings used for low magnification inspection are not subject to final heat treatment, forgings of other materials are generally subject to low magnification inspection after final heat treatment

fracture specimens are generally subject to specified heat treatment

the principle of microstructure inspection is to use optical microscope to inspect the microstructure of forgings of various material grades. The inspection items generally include the essential grain size, or the grain size at the specified temperature, that is, the actual grain size, non-metallic inclusions, microstructure such as decarburization layer, eutectic carbide non-uniformity, overheating, overburning structure and other required microstructure

the inspection of mechanical properties and process properties is to use tensile testing machine, impact testing machine, endurance testing machine, fatigue testing machine, hardness tester and other instruments to measure the mechanical properties and process properties of forgings and test pieces that have undergone the specified final heat treatment into specified samples

the chemical composition test generally uses the chemical analysis method or spectral analysis method to analyze and test the composition of forgings. With the development of science and technology, both the mechanical analysis and spectral analysis of various tension experiments that control the situation have been developed before and after abroad, and their analysis methods have made progress. As for the spectral analysis method, the spectroscopic method and spectroscopic method are no longer simply used for component analysis. The emerging photoelectric spectrometer not only has a fast analysis speed, but also greatly improves the accuracy. The emergence of the plasma photoelectric spectrometer has greatly improved the analysis accuracy, and its analysis accuracy can reach grade, which is very important for the analysis of trace harmful impurities in high-temperature alloy forgings, such as Pb, as, Sn, Sb Bi is a very effective method

the above-mentioned methods, whether macro structure inspection method, micro structure inspection method or performance and composition determination method, are destructive test methods. For some important and large forgings, destructive methods can no longer fully meet the requirements of quality inspection. On the one hand, they are too uneconomical, on the other hand, they are mainly to avoid one sidedness of destructive inspection. The development of nondestructive testing technology provides a more advanced and perfect means for forging quality inspection

generally, the non-destructive testing methods used for quality inspection of forgings include magnetic particle inspection, penetrant inspection, eddy current inspection, ultrasonic inspection, etc

magnetic particle inspection is widely used to inspect the surface or near surface defects of ferromagnetic metal or alloy forgings, such as cracks, hairlines, white spots, non-metallic inclusions, delamination, folding, carbides or ferrite bands

this method is only applicable to the inspection of ferromagnetic material forgings, and is not applicable to forgings made of austenitic steel

in addition to magnetic material forgings, the penetrant inspection method can also inspect the surface defects of non ferromagnetic material forgings, such as cracks, looseness, folding, etc. generally, it is only used to inspect the surface defects of non ferromagnetic material forgings, and cannot find the defects hidden below the surface

eddy current inspection is used to inspect the surface or near surface defects of conductive materials

ultrasonic inspection method is used to inspect internal defects of forgings, such as shrinkage cavity, white spot, center crack, slag inclusion, etc. Although this method is convenient, fast and economical, it is difficult to accurately determine the nature of defects

with the development of non-destructive testing technology, new non-destructive testing methods such as acoustic vibration method, acoustic emission method, laser holography method and CT method have emerged. The emergence of these new methods and their application in forging inspection will greatly improve the level of forging quality inspection

it is worth mentioning that the accuracy of forging quality inspection results depends on correct test methods and techniques, but also on correct analysis and judgment. Only the correct test method, without accurate analysis and judgment, will not draw appropriate conclusions, but the scrap market still has a strong wait-and-see atmosphere. Therefore, the analysis of forging quality is actually the comprehensive application of various test methods and the comprehensive analysis of various test results, For the problems of large and complex forgings, Liu Zhongfan said: "I have no doubt that there are two methods for the industrialization of graphene. From this point of view, it can be said that various test methods complement each other in the analysis process. Only through the organic cooperation of various test methods and the comprehensive analysis of their test results can we draw a correct conclusion. At the same time, for the purpose of forging quality analysis, in addition to the correct inspection, necessary process tests should also be carried out to find out the real causes of quality problems And put forward satisfactory improvement measures and prevention countermeasures

of course, which test methods should be used in actual work and which test methods should be used should be based on the type of forgings and the specified test items. When selecting test methods and means, we should consider not only progressiveness, but also practicality and economy. We should not simply pursue progressiveness. If we can use one means to solve problems, we should not use two or more. The selection of test means should be based on accurately judging the nature of defects and accurately finding out the causes of defects, Sometimes, too advanced test methods will lead to unnecessary consequences and cause undue losses

it should also be pointed out that for inspection, no matter what kind of inspection or test, there are standard test methods that should be specified, and we must carry out the test or inspection according to the specified test methods. (end)

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