Simulation Study on the Austenisation and Cooling Behaviors of the Medium-Mn Steel

2014 ◽  
Vol 1063 ◽  
pp. 3-6 ◽  
Author(s):  
Si Lian Chen ◽  
Yao Zong Bao ◽  
Han Dong ◽  
Wen Quan Cao

The austenisation and quenching behaviors of a medium-Mn steel with a chemical composition of C 0.14% and Mn 5.0% were presented in this paper. The heating and holding temperature varied from 500OC to 950OC was applied to find the austenization temperature. The holding time varied from 1-5minutes was used to choose the suitable austenisation time. Air cooling were applied to check the hardening capacity of the studied steel. It was found that the tensile strength is lower than 900Mpa and total elongation varied from 20-30% when the austenisation temperature is lower than 700OC. However, the tensile strength could be high up to 1600MPa and the total elongation about 12% when the austenisation temperature is higher than 700OC with air cooling. Based on the low austenisation temperature and the air hardening capacity, it was proposed that the studied medium-Mn steel could be used as the hot stamping steel in the car industry.

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1888
Author(s):  
Zigan Xu ◽  
Jiyao Li ◽  
Xiao Shen ◽  
Tarek Allam ◽  
Silvia Richter ◽  
...  

Developing medium-Mn steels (MMnS) demands a better understanding of the microstructure evolution during thermo-mechanical treatments (TMTs). This study demonstrates the relationship among processing, microstructure, and mechanical properties of a warm-rolled medium-Mn steel (MMnS) containing 1.5 wt. % Cu and 1.5 wt. % Ni. After short-time warm rolling (WR) in an intercritical temperature range, a significant quantity (40.6 vol.%) of austenite was reverted and retained after air cooling. The microstructure and tensile properties of the WR specimens were compared with two typical process routes, namely hot rolling+ cold rolling+ annealing+ tempering (CRAT) and warm rolling+ annealing+ tempering (WRAT). The WR specimen exhibited comparable tensile properties with the CRAT specimens (967 MPa yield strength, 1155 MPa tensile strength, 23% total elongation), with a remarkably shortened process route, which was derived from the dislocation accumulation and austenite reversion during rolling. The WR route stands out among the traditional CRAT and the extended WRAT routes for its excellent tensile properties and compact processing route.


Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1090 ◽  
Author(s):  
Chunquan Liu ◽  
Qichun Peng ◽  
Zhengliang Xue ◽  
Chengwei Yang

In the context of obtaining an excellent elongation and tensile-strength combination in the third generation of advanced high strength steel, we emphasized the practical significance of adjusting the retained austenite fraction and stability in medium-Mn steel to obtain better mechanical properties. A novel cyclic quenching and austenite reverse transformation (CQ-ART) was used to obtain a large retained austenite content in Fe-0.25C-3.98Mn-1.22Al-0.20Si-0.19Mo-0.03Nb (wt.%) Nb–Mo micro-alloyed medium-Mn steel. The results show that after twice cyclic quenching and ART, the alloy exhibited optimum comprehensive properties, characterized by an ultimate tensile strength of 838 MPa, a total elongation of 90.8%, a product of strength and elongation of 76.1 GPa%, and the volume fraction of austenite of approximately 62 vol.%. The stability of retained austenite was significantly improved with the increasing of the number of cyclic quenching. Moreover, the effects of CQ-ART on the microstructure evolution, mechanical properties, C/Mn partitioning behavior, and austenite stability were investigated. Further, the strengthening effect of microalloying elements Nb–Mo was also discussed.


2019 ◽  
Vol 944 ◽  
pp. 337-343
Author(s):  
Rui Dong ◽  
Ke Lv ◽  
Hui Guo ◽  
Ai Min Zhao

Two annealing processes have been designed to process a medium Mn steel, namely, the traditional direct two-phase annealing process and the pre-quenching treatment before two-phase annealing process, called two stage annealing process. The experimental results indicated that different annealing processes resulted in completely different microstructures, and a significant difference in mechanical properties. The microstructures of the steel after direct two-phase annealing process were coarse tempered martensite matrix and retained austenite. In this case, the optimum mechanical properties with total elongation of 29.87 %, tensile strength of 932 MPa and UTS*TE of 27.84 GPa•% were achieved after annealing at 625 °C for 18 h. The annealing process with pre-quenching treatment could realize two kinds of retained austenite, including acicular austenite and blocky austenite. The process with pre-quenching treatment could improve mechanical properties as well as shorten the optimal annealing time. The steel with two stage annealing process achieved optimal mechanical properties after pre-quenching and annealing at 625 °C for 4 h with tensile strength of 1177 MPa, total elongation of 30.92 % and UTS*TE of 36.39 GPa•%.


Author(s):  
Ying Chang ◽  
Cunyu Wang ◽  
Kunmin Zhao ◽  
Han Dong ◽  
Jianwen Yan

The medium-Mn steel is a promising third-generation automobile steel. Its chemical composition, microstructure, and thermal and mechanical properties are introduced and a warm-stamping process for the medium-Mn steel is proposed. The optimal process parameters are identified through the design of experiments (DOE) and range analysis. The evaluated experimental indexes include tensile strength, elongation, and hardness. The optimal forming process consists of an austenitization temperature of 840 °C, a soaking time of 4 min, and an initial stamping temperature of 500 °C. The proposed process was applied to the warm stamping of an automotive B-pillar. The microstructure of ultrafine, uniform, and complete martensite laths was obtained. The formed part exhibits approximately 1420 MPa tensile strength, over 11% elongation and 460 HV hardness. The optimal warm-stamping process has proved effective and applicable for forming medium-Mn steel parts. It will help promote the application of the third-generation automotive steels.


2014 ◽  
Vol 1063 ◽  
pp. 65-68 ◽  
Author(s):  
Peng Zhang ◽  
Gang Wang ◽  
Chun Cheng Pan ◽  
Xiao Qi Ren

Microstructure and mechanical properties of different area of 22MnB5 hot stamping part were analysis by experiment. The results show that the maximum tensile strength reaches 1578MPa at bottom surface area, and the elongation is at the region of 8.5~12 with die cooling area, and the area of bottom surface has higher tensile strength than that of side wall area. Martensite is formed with die cooling, and tempered martensite and undissolved ferrites were found at side wall area. The microstructure of area with air cooling is composed of ferrite and pearlite, and a small amount of martensite.


Author(s):  
Zhenjiang Li ◽  
Yujing Liu ◽  
Pengju Jia ◽  
Chao Luo ◽  
Ruyi Zhang ◽  
...  

Microstructure and mechanical properties of medium-Mn steel (Fe–0.14C–5Mn–1Al–Ce) processed by different austenite reverted transformation-annealing temperatures vary from 580 °C to 740 °C were studied. It was found that the austenite reverted transformation-annealing temperature has a strong effect on microstructure evolution. The martensite structure was transformed into austenite by austenite reverted transformation during the austenite reverted transformation-annealing process. The orientation relationship between the austenite and the matrix was dominated by the Kennicutt–Schmidt relation. With the increase of the austenite reverted transformation-annealing temperature, the content of retained austenite first increases and then decreases at room temperature. The tensile strength first decreases and then increases, while the elongation first increases and then decreases. An excellent combination of tensile strength and elongation (Rm × A) was obtained in the Fe–0.14C–5Mn–1Al–Ce steel by austenite reverted transformation-annealing at 640 °C.


2020 ◽  
Vol 258 ◽  
pp. 126804 ◽  
Author(s):  
Feng Yang ◽  
Jian Zhou ◽  
Yun Han ◽  
Peng Liu ◽  
Haiwen Luo ◽  
...  

Author(s):  
Chenpeng Tong ◽  
Guosen Zhu ◽  
Qi Rong ◽  
Victoria A. Yardley ◽  
Zhusheng Shi ◽  
...  

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3362
Author(s):  
Manfred Stadler ◽  
Ronald Schnitzer ◽  
Martin Gruber ◽  
Katharina Steineder ◽  
Christina Hofer

The properties of the heat-affected zone (HAZ) are reported to have a great influence on the mechanical performance of resistance spot welded advanced high strength steels. Therefore, in the present work, the HAZ of a medium-Mn steel is characterized regarding its microstructure and its mechanical properties depending on the distance to the fusion zone (FZ). In order to obtain the local mechanical properties of the HAZ, samples were heat-treated in a joule-heating thermal simulator using different peak temperatures to physically simulate the microstructure of the HAZ. By comparing the microstructure and the hardness of these heat-treated samples and the HAZ, the local peak temperatures within the HAZ could be determined. Subsequently, tensile tests were conducted, and the austenite phase fraction was measured magnetically on the physically simulated HAZ samples in order to determine the local mechanical properties of the HAZ. As verified by energy-dispersive X-ray spectroscopy, peak temperatures above 1200 °C led to a uniform distribution of manganese, resulting in a predominantly martensitic microstructure with high strength and low total elongation after quenching. Below 1100 °C, the diffusion of manganese is restricted, and considerable fractions of austenite remain stable. The austenite fraction increases almost linearly with decreasing peak temperature, which leads to an increase of the total elongation and to a slight decrease in the strength, depending on the distance to the FZ. Temperatures below 700 °C exhibit hardly any effect on the initial microstructure and mechanical properties.


2018 ◽  
Vol 385 ◽  
pp. 308-313 ◽  
Author(s):  
Vladimir Torganchuk ◽  
Dmitri A. Molodov ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev

The effect of cold working followed by annealing on the development of ultrafine grained microstructure and mechanical properties of an Fe-12%Mn-0.6%C-1.5%Al medium-manganese steel was studied. The steel was cold rolled with intermediate annealings and then annealed at 873 K or 923 K for 30 min. The yield strength and total elongation of the Fe-12Mn-0.6C-1.5Al steel after cold rolling were 1200 MPa and 14%, respectively. The heat treatments resulted in the formation of two phase (austenite-ferrite) ultrafine grained microstructures with average grain sizes of 0.9 to 1.2 μm, depending on the annealing temperature. The annealed ultrafine grained steel samples exhibit the yield strength in the range of 800-950 MPa, the ultimate tensile strength in the range of 1150-1200 MPa, and total elongation of 12% to 19%.


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