Investigation of austenitising behaviour of medium-Mn steel in the hot-stamping heating process

Tong, Chenpeng; Zhu, Guangming; Rong, Qin; Yardley, Victoria A.; Shi, Zhusheng; Li, Xuetao; Luo, Jiaming; Lin, Jianguo

doi:10.1016/j.jmatprotec.2021.117269

Cited by 14 publications

(4 citation statements)

References 27 publications

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“…These phenomena were due to the fact that the high heating temperature with the long soaking time makes the austenite grain coarser, which reduces the strength of the specimen. [ 23 ] When the heating temperature is 900 °C, the hardness of the specimen with the soaking time of 4 min is nearly equal to that of 8 min. So it can be assumed that the hardness value of the specimen with 900 °C heating temperature can reach the largest value when the soaking time is 6 min.…”

Section: Resultsmentioning

confidence: 99%

Effect of Heat Treatment on the Formability of Zn‐Coated Hot Stamping Steel

Zheng

et al. 2022

steel research int.

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Herein, the effect of heat treatment with die quenching on Zn‐coated hot stamping steel is analyzed. Heating temperatures are 850, 880, 900, and 930 °C, and soaking times are 4 and 8 min. Then, microstructure, hardness, coating layer morphology, element diffusion and distribution, formation of microcrack and microvoid, and oxidation are analyzed. Results reveal that as heating temperature increases, the Vickers hardness of Zn‐coated hot stamping steel increases when soaking time is 4 min, while it decreases when soaking time is 8 min. The least average hardness value is still larger than 460, resulting from the formation of the martensitic phase. The diffusion tends to be significant as heating temperature and soaking time increase. Both the diffusion and the evaporation affect the thickness of the coating layer remarkably. The average layer thickness is at least 18.2 μm. Microcrack generates in the coating layer due to different thermal expansions between substrate and coating layer and the melting of Zn or Zn–Fe binary phase with high content of Zn. Microvoid forms in the coating layer, resulting from the Kirkendall effect and oxidation of the Zn element. Moreover, with the increase in heating temperature and soaking time, Fe2O3 is also generated on the coating surface along with ZnO.

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Section: Resultsmentioning

confidence: 99%

Effect of Heat Treatment on the Formability of Zn‐Coated Hot Stamping Steel

Zheng

et al. 2022

steel research int.

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“…The parameters A c1 , A c3, and T h shown in table 2 represent the initial temperature, final temperature, and austenite homogenization temperature of austenite transformation respectively. It can be seen that A c1 , A c3, and T h all rise with the increase in heating rate, while the austenite homogenization time is inversely proportional to the heating rate [21]. More importantly, the reduction of heating time is beneficial to reducing surface oxidation and refining austenite grains.…”

Section: Induction Heating Temperaturementioning

confidence: 94%

Effect of induction heating temperature on the microstructure and mechanical properties of HSLA square tubes

Wang¹,

Mehari²,

Wu³

et al. 2022

Mater. Res. Express

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Severe strain hardening, thickness reduction, and large outer corner radius are three typical characteristics in the corner section of cold roll-formed steel. This paper presents a new manufacturing technology called cold and hot composite roll forming to improve the shape and properties in the corner section. In order to study the effect of induction heating temperature, a multi-pass cold and hot composite roll forming experiment for high-strength low-alloy steel (HSLA) square tubes was carried out under three different heating temperature ranges namely: the non-austenitizing zone, partial austenitizing zone, and austenitizing homogenizing zone. The microstructure and mechanical properties in the corner section of square tubes were studied using the material testing machine, optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). Results showed that with the increase of induction heating temperature, the geometrical morphology and mechanical properties in the corner section of the cold and hot composite roll-formed square tube were significantly improved. Thus, compared with cold roll-formed square tubes, the corner thickness of cold and hot composite roll-formed square tubes was increased by 59%, the product of strength and elongation was increased by 48%, the outer corner radius was decreased by 91%, and no cracks appeared during the flattening test. Moreover, the proportion of granular bainite in the outer corner section increased, and the grain distortion in the inner corner section was relieved. The experimental results further showed that the austenitizing homogenizing zone was preferable among the three heating temperature ranges to manufacture high-quality HSLA square tubes.

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“…Hot stamping technology is an advanced technology to fulfill automobile lightweight, characterized by lower forming resistance, better formability, higher dimensional accuracy and less springback [ 6 , 7 ]. The tensile strength of the hot stamped parts of medium manganese steel can reach at least 1500 MPa, while their elongation after fracture only ranges from 5% to 10% [ 8 ], of which the strength and plastic product is far below the requirements of the third-generation advanced high-strength steel. Therefore, under the premise of ensuring the excellent hot stamping performance of medium manganese steel, it is necessary to explore new forming and heat treatment processes to improve the plasticity to satisfy the performance demands.…”

Section: Introductionmentioning

confidence: 99%

Research on Hot Stamping-Carbon Partition-Intercritical Annealing Process of Medium Manganese Steel

et al. 2023

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In order to improve the plasticity of hot stamping parts, this paper combines the heat treatment process with the plastic forming of sheet metal, and creatively proposes a new process of hot stamping-carbon partitioning-intercritical annealing. The mechanical properties and microstructure are characterized under the newly proposed process, the quenching-partition (QP) process, and the intercritical annealing (IA) process, respectively. The new process firstly undergoes incomplete austenitizing treatment at 610 °C, then carries out distribution treatment while stamping at 300 °C, and finally conducts annealing treatment in critical zone at 680 °C in two-phase zone. The results show that a multi-phase refined microstructure composed of lath martensite, retained austenite, fresh martensite, and carbides are obtained by the new process. Most of the retained austenite is shaped in the thin film due to martensitic shear, in which carbon and manganese elements diffuse from martensite to austenite by heat treatment, thus stabilizing the retained austenite. Retained austenite with a volume fraction of 33.7% is obtained in the new process. The retained austenite with higher content and better stability is completely consumed during the stretching process, which gives full play to discontinuous TRIP effects, thus delivering the elongation of 36.8% and the product of strength and elongation (PSE) reached as high as 43.6 GPa%.

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Investigation of austenitising behaviour of medium-Mn steel in the hot-stamping heating process

Cited by 14 publications

References 27 publications

Effect of Heat Treatment on the Formability of Zn‐Coated Hot Stamping Steel

Effect of Heat Treatment on the Formability of Zn‐Coated Hot Stamping Steel

Effect of induction heating temperature on the microstructure and mechanical properties of HSLA square tubes

Research on Hot Stamping-Carbon Partition-Intercritical Annealing Process of Medium Manganese Steel

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