Detection of stainless steel macrostructure, microstructure and defect assessment of steel, low alloy steel structure detection, detection of low carbon steel structure, spring steel macrostructure and defect evaluation
Tianjin Rong Da Testing Co., Ltd. contact: Wang Jingfu
Cell phone: 13102238283 QQ:3144667033
Telephone: 022-23892103
Macrostructure and defect assessment of steel suitable for carbon steel, alloy structural steel, spring steel and other steel (billet). The morphology of different steel (Billet) low double structure and defects on the surface of the specimen is not exactly the same, so the analysis of the defects should be made in the judgment of the nature of the defect. Macrostructure and defect should be visible to the naked eye, to clarify the nature of defects, can also use a magnifying glass. According to the size and defect properties of steel, the three sets of standard rating chart can be evaluated according to the standard of low power.
If used to assess the diameter length of 40 ~ 150m circle, Fang Gang, the macrostructure and defect morphology is divided into the following five categories: General osteoporosis grade 1-4; 1 central porosity - level 4 - 4 1; general spot segregation; edge spot segregation - level 4 1; 1 - 4 ingot segregation. If used to assess the diameter or length of more than 150 ~ 250mm circle, Fang Gang, the macrostructure and defect morphology are divided into five types as follows. General in 1 - level 4 - 4 - 1; porosity; ingot segregation 1 - 4; 1 General spot segregation level 4; 1 - 4 edge spot segregation; if used to assess the length of 40 250mm diameter fly round the macrostructure and defect morphology are divided into eight types as follows. Subcutaneous bubble; bubble; non metallic inclusions; non-metallic inclusion; residual shrinkage 1 - 3; 1 - 3 spot formation; 1 - 3; 1 - axis intergranular crack 3.
The macrostructure of round, square and flat diameter or length of less than 40m and more than 250mm and defects, according to the agreement of both parties can also supply reference to the evaluation level assessment. In the evaluation of the macrostructure and defect, when the severity between adjacent level two, up to half of the class, when the defect on the surface of the sample area percentage over the existing standard level, the level will float upward. For defects that do not require an assessment level, only the defect category.
The characteristics of microstructure and defect of steel is generally loose, loose center, subcutaneous bubble, bubble, ingot segregation, spot segregation, segregation, axial carbon segregation, gravity segregation, residual shrinkage, flanging, flaking, Zhou Xinjing crack between dissimilar metal, non-metallic inclusions, slag, coarse grain. Folding, streamline, roughly eighteen. In this paper, the general characteristics of loose, the principle of assessment, the causes of defects and to solve or improve the defects of the method to do a deep discussion.
The general characteristics of osteoporosis in etching on the sample surface is tissue not dense, scattered dark spots and pore shape, dark spots were round or oval. The pores are observed under the magnifying glass, which are irregular holes or circular holes. These dark spots and pore generally appear in the dendritic shaft and the secondary shaft between the thick, dark and loose zone axis shine. When the difference between the corrosion degree of the bright area and the dark area is not large, the pit can not be produced. The reason is: the liquid steel during solidification, dendrite crystal core to form up in the dendrite of the main shaft and the secondary shaft exists due to solidification of liquid steel produced by small shrinkage and analysis in some low melting point elements, gas and non metallic inclusions; the slight shrinkage and analysis set the material after acid etching showed loose tissue. Harm of general loose material is one of the internal wide distribution area, and the pore and hole and segregation, will significantly weaken the fatigue strength of steel and other mechanical properties, while increasing the cracking tendency of steel in the forging process. The evaluation principle is based on the number, scattered throughout the cross section of the dark shape and pore size and their distribution, and considering the thickness of the dendrite and. We can use the rapid crystallization method to improve or eliminate the general loose defects, so that the dendritic crystals are not fully developed and reduce the inclusion and gas in the steel.