Method of inspecting steel inclusions
Inclusions in steel have an important impact on the performance of steel. Inclusion qualification inspection is an important part of ensuring the quality of steel. There are three current inspection methods:
1. Metallographic sample method
At present, steel companies generally use the metallographic sample method to inspect the inclusions in the steel, that is, after grinding and polishing the sample to be tested into a metallographic sample, it is exposed to the surface of the metallographic sample under an optical microscope or a scanning electron microscope. The inclusions are tested and studied. The advantages of the metallographic specimen method are simple, intuitive and fast. However, since the content of inclusions in steel is very small, their distribution is irregular. However, it is easy to use this method for single or multiple metallographic surfaces to replace the entire surface with a single point, which has serious unreliability.
2. Aqueous electrolysis
In order to avoid the randomness of the metallographic sample method, many researchers use electrolysis to extract the inclusions in the steel from the matrix. The electrolysis method is that after the sample is energized, the steel matrix enters the solution and dissolves in the form of ions, and the non-metallic inclusions are not electrolyzed and remain in the state of solid ions, and then the inclusions are collected for a comprehensive study. However, most of the electrolytes currently used are acidic aqueous solutions with PH<3, and most of the inclusions in steel are composite inclusions. The composite inclusions are unstable in acidic aqueous solutions, and acidic aqueous solutions can easily destroy many inclusions in steel. . It is difficult to make a rigorous argument as to which inclusions are destroyed and the rate of destruction. Therefore, the electrolysis method also needs to be improved.
3. Non-aqueous electrolysis method
The pH value of the non-aqueous solution is 8, and the radioisotope tracer method proves that the non-aqueous electrolysis method does not damage the inclusions during the separation process, and can completely preserve the various inclusions in the sample, including nano-inclusions. Then use scanning electron microscope and energy spectrum or transmission electron microscope, high resolution electron microscope and energy spectrum to analyze the inclusions. This is a highly accurate and efficient method for detecting inclusions in steel.