From the perspective of metallography, because stainless steel precision steel pipes contain a high content of chromium, chromium forms a very thin chromium film on the surface. This film isolates the oxygen that invades the steel, thus playing a role in corrosion resistance. For stainless steel pipes, the most important thing is undoubtedly the anti-corrosion performance of the material and the chemical composition analysis. The composition, heat treatment process, and hot and cold processing process of the steel pipe directly affect the changes in its internal organization and structure, thereby changing the mechanical properties.
Therefore, using metallographic analysis to observe and inspect the internal organization structure of the pipe is an important means of industrial production. The commonly used metallographic observation and inspection of stainless steel precision steel pipes can be mainly divided into the following four aspects:
1. Raw material inspection: Check the metallurgical quality of the raw materials, such as component segregation, distribution type, and level of non-metallic inclusions; casting looseness, pores, and uniformity of slag inclusions in casting materials; surface decarburization, overheating, overburning, cracks, and deformation of forged parts.
2. Quality control in the production process: Metallographic analysis can provide a basis for adjusting the process and modifying the process parameters, and guide production, such as whether the heat treatment quenching heating temperature, insulation time, cooling rate, etc. are appropriate; control of chemical surface heat treatment process parameters; whether the starting and final forging temperatures of forging are appropriate, etc.
3. Product quality inspection: Some precision stainless steel pipes require not only mechanical properties and physical performance indicators but also microstructure parameters, which are used as one of the technical indicators for quality assessment.
4. Failure analysis: Metallographic structure analysis methods are widely used in mechanical failure analysis, and are very convenient for identifying some common defects. Such as decarburization on the surface of stainless steel welded pipes; morphology and distribution characteristics of microcracks; chemical heat treatment defects; abnormal structure after heat treatment; precipitation of brittle phases at grain boundaries, etc. The results of these metallographic analyses are often used as the basis for fault analysis.
In addition, the following two aspects of preparation are required before metallographic testing: First, a large number of tests and studies are conducted on the composition structure and performance of the materials, and the understanding of the materials is completed through theoretical data; second, the comparison and regularity of the materials are conducted according to the characteristics of the materials, to know the common characteristics and special properties between the materials, which has extremely important guiding significance for metallographic inspection.
The above is why metallographic inspection is required for stainless steel precision steel pipes. The diversity of steel pipe performance is closely related to the organizational structure. Secondly, it is necessary to have a deep understanding of the materials and the common characteristics and special properties between the materials before metallographic inspection. Therefore, it has become increasingly important to judge whether the process performance, mechanical properties, corrosion resistance, etc. of stainless steel precision steel pipes can meet the application requirements through metallographic inspection.
Post time: Jun-19-2024