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Effect of alloying elements on mechanical properties of Chongqing stainless steel tube after tempering transformation

Release time: September 30, 2020 Views: 54 come from: Chengdu Zhengshang Stainless Steel Co., Ltd

Chongqing stainless steel pipe :

The effects of alloying elements on mechanical properties of stainless steel tube during tempering transformation can be summarized as follows: martensite decomposition in the structure of stainless steel pipe; transformation of retained austenite; recrystallization of ferrite and formation, transformation and aggregation of carbides. These four processes are in the stage of increasing tempering temperature one In the temperature range. Generally speaking, the existence of alloying elements in stainless steel tubes does not change the general rules and basic characteristics of the four processes, but it shows different effects in different stages.

 Chongqing stainless steel pipe

The main effect is to improve the tempering stability of steel in different degrees, that is to say, the tempering resistance of quenched steel is enhanced in different degrees. This is very important for the formulation of heat treatment process, because if the tempering stability of stainless steel pipe is improved, the tempering temperature can be increased and the residual stress can be fully eliminated under the condition of maintaining high strength and hardness, which is very beneficial to improve the impact toughness of steel and the dimensional stability of parts.

 Chongqing stainless steel pipe

In order to understand how alloy elements can improve the tempering stability of stainless steel tubes and why they have such effects, it is necessary to analyze and discuss the influence of alloy elements in various stages of tempering, which are described as follows. When the quenched stainless steel tube is tempered below 200 ℃, it decomposes from martensite and remains with phase a one The content of alloying elements is equal to the average content of alloying elements in martensite. This shows that the carbon atoms can only be diffused in a short range due to the low tempering temperature, and the atoms of alloy elements can not be diffused yet, and they still keep average concentration and distribute evenly in a phase and carbide. Therefore, the alloy elements have no obvious effect on the rate of martensitic two-phase decomposition.

 Chongqing stainless steel pipe

When tempered above 200 ℃, the martensite in the structure of stainless steel tube decomposes in a single phase. At this time, the carbon atoms can be diffused remotely, but the alloy element atoms still can not diffuse. In this way, the existence of alloy element atoms will hinder the diffusion of carbon atoms, thus delaying the decomposition of martensite, but different elements have different effects. The experimental results show that the non carbide elements Ni, Al and Mn have little effect on the single-phase decomposition of martensite, while the carbide element has a strong affinity with carbon, which reduces the diffusion rate of carbon in phase a, thus strongly hinders the single-phase decomposition of martensite.

 Chongqing stainless steel pipe

Although cobalt and silicon are not carbide forming elements, they can strongly delay the formation and growth of carbide nuclei, so they also significantly hinder the single-phase decomposition of martensite. Therefore, compared with carbon steel, the quenching alloy steel containing this element has a lower degree of martensite decomposition after tempering at the same temperature (e.g., 300 ℃), and the carbon concentration and squareness in a phase are higher than those in carbon steel, thus retaining the mechanical properties of high hardness and strength of stainless steel pipe

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