Authors:
Yilong Zhang
1
;
Wei Wu
1
;
Bingbing Li
1
;
Dezhi Yuan
2
;
Kejian Li
3
;
Kessam Shin
4
and
Pengjun Cao
1
Affiliations:
1
School of Metallurgy and Materials Engineering and Chongqing University of Science and Technology, China
;
2
Steel Tube Co., Ltd. and Chongqing Iron & Steel Group, China
;
3
School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, The center of Material Analysis and Testing, Chongqing University of Science and Technology, Chongqing and China, China
;
4
School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, School of Nano & Advanced Materials Engineering, Changwon National University, Changwon and Korea), China
Keyword(s):
Heat treatment, Martensitic stainless steel, Microstructure, Precipitation.
Abstract:
L80-13Cr martensitic stainless steel (MSS) is a kind of oil casing steel. It has good resistance to carbon dioxide corrosion and seawater corrosion, which makes it common oil casing steel in marine oil and gas exploration. The effect of heat treatment on mechanical properties and microstructure of L80-13Cr MSS has been studied. The specimens were analyzed using the micro-hardness test, optical microscope (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The hardness test showed that the steel was secondarily hardened when tempering at 300 ~ 500C. But continuous softening occurred when the temperature was above 500C. The martensite was recovered at temperatures around 300 ~ 500C, and higher temperature tempering (600C) caused grain growth and even recrystallization. It has been found that the precipitates in the steels that were tempered at 300C, 500C and 700C, were need-like Fe3C carbides, coarsed needle-like Fe3C carbides and rod-like or sph
ere-like Cr23C6 carbides. Especially when tempered at 700C, the Cr23C6carbidesprecipitation along the marten site lath was rod-like and precipitation along grain boundaries was sphere-like. Secondary hardening between 300 ~ 500C tempering of 13Cr is attributed to the precipitation of needle-like Fe3C. The recovery and recrystallization of the matrix and the coarsening of carbides resulted in the continuous softening of 13Cr MSS during tempering.
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