Method of differentiating martensite in cast ferrite stainless steel and calculating martensite -phase contents

Abstract

The invention discloses a method of differentiating martensite in a cast ferrite stainless steel and calculating a martensite phase content thereof, which can accurately, quickly and quantitatively calculate a content of martensite in the annealed-state ferrite stainless steel by the steps of cutting a sample, grinding, electrolyzing, polishing, cleaning, drying, EBSD analyzing, selecting crystal grains, collecting an image quality diaphragm by an analyzing software, adding a grid line by a gold-phase microscope, repeatedly selecting a region, calculating the martensite content and calculating the average value; the method solves the technical problem that the ferrite and martensite two phases in an annealed-state ferrite stainless steel are difficult to be differentiated and are difficult to calculate the quantity. Simultaneously, the technology can be further widely applied to the two-phase proportion quantitative calculation with a similar crystal structure and different internal stresses, thereby having a good popularization and application prospect.

Description

technical field [0001] The invention belongs to the field of material analysis, in particular to a method for distinguishing martensite in cast ferritic stainless steel and calculating the content of martensite phase. Background technique [0002] There have always been problems in the identification of martensite in ferritic stainless steel and the calculation of the two-phase ratio. The reasons are as follows: ① Due to the small difference in the corrosion resistance of ferrite and martensite in ferritic stainless steel, resulting in Conventional ferritic stainless steel metallographic etchant (FeCl 3 Corrosion agent / HCl alcohol etchant) can only faintly display phase boundaries, and these phase boundaries are also easy to be confused with ferrite grain boundaries, which has a great impact on the subsequent resolution of the two phases and the quantitative calculation of the ratio of the two phases using the conventional coloring method. ② In order to confirm that the col...

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Problems solved by technology

[0002] There have always been problems in the identification of martensite in ferritic stainless steel and the calculation of the two-phase ratio. The reasons are as follows: ① Due to the small difference in the corrosion resistance of ferrite and martensite in ferritic stainless steel, resulting in Conventional ferritic stainless steel metallographic etchant (FeCl 3 etchant / HCl alcohol etchant) can only faintly display phase boundaries, and these phase boundaries are also easily confused with ferrite grain boundaries, which has a great impact on the subsequent resolution of the two phases and the quantitative calculation of the ratio of the two phases using the conventional coloring method

② In order to confirm that the coloring phase is a martensitic phase, microhardness analysis is required to determine whether it has high hardness. However, this method also has its limitations, because for ferritic stainless steel, especially as-cast Ferritic stainless steel, in which the martensite phase is mostly low-carbon martensite phase, its hardness is very different from that of the ferrite matrix, and it is difficult to distinguish it by hardness

This is not only cumbersome and labor-intensive, but also because the film is easy to move, resulting in inaccurate data, and the original data is not easy to retain, lacking reproducibility

[0007] So far, there has not been any patent literature on the application of electron backscatter diffraction combined with grid method to quantitatively calculate the martensite content in as-cast and as-cast ferritic stainless steel

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