scholarly journals Effect of Cooling Path on Microstructures and Hardness of Hot-Stamped Steel

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1692
Author(s):  
Yaowen Xu ◽  
Qiumei Ji ◽  
Gengwei Yang ◽  
Siqian Bao ◽  
Gang Zhao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Hot Stamping ◽  
Lath Martensite ◽  
Critical Value ◽  
Secondary Cooling ◽  
Cooling Process ◽  
Cooling Path ◽  
Martensitic Microstructure ◽  
Hot Stamped Steel

The final mechanical properties of hot-stamped steel are determined by the microstructures which are greatly influenced by the cooling process after hot stamping. This research studied the effect of the cooling path on the microstructures and hardness of 22MnB5 hot-stamped steel. The cooling path was divided into continuous and discontinuous (primary and secondary) processes. After cooling, the Vickers hardness along the thickness of the specimens was measured. The results indicate that, for a continuous cooling process, there was a critical cooling rate of 25 °C/s to obtain fully martensitic microstructure. For the discontinuous cooling process, the slower was the cooling rate, the higher was the degree of auto-tempering that occurred, and the greater was the amount of carbides that formed, regardless of the primary or secondary cooling rate. When the cooling rate was lower than the critical value, a higher primary cooling rate suppressed the auto-tempering of lath martensite and increased the quenched hardness. By contrast, the hardness was not sensitive to the cooling rate when it exceeded the critical value.

Numerical Simulation of the I-Beam during Cooling Process

2013 ◽  
Vol 712-715 ◽  
pp. 1634-1637
Author(s):  
Jian Liu ◽  
Fu Zeng Hou ◽  
Xiao Guang Yu
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Heat Treatment ◽  
Cooling Rate ◽  
Theoretical Basis ◽  
Treatment Process ◽  
Residual Austenite ◽  
Heat Treatment Process ◽  
Cooling Process ◽  
Controlled Cooling

In order to improve the comprehensive mechanical properties of the steel, the heat treatment software COSMAP is used to simulate the rolling and controlled cooling of I-beam. The numerical simulation shows that: when the cooling rate is controlled at 10 °C/s around, the mechanical properties of controlled cooling can be obviously improved. The strength and hardness can be improved on the condition of ductility and toughness ensured, while the amount of residual austenite can be reduced significantly, which provide a theoretical basis for further optimization of the heat treatment process.

Effect of Original Microstructure on Microstructure and Mechanical Properties of High Strength Steel WHF1500H during Hot Forming

2018 ◽  
Vol 941 ◽  
pp. 206-211
Author(s):  
Wen Qiang Zhou ◽  
Li Bo Pan ◽  
Kuan Hui Hu ◽  
Wei Hua Sun ◽  
Rong Dong Han
Keyword(s):  
Mechanical Properties ◽  
Hot Stamping ◽  
Lath Martensite ◽  
Testing Machine ◽  
High Strength ◽  
Optical Microscope ◽  
Original Structure ◽  
Iron And Steel ◽  
Microstructure And Mechanical Properties ◽  
Austenite Grains

The press hardening steel sheets WHF1500H with different original structures produced by compact strip production (CSP) line in Wuhan Iron and Steel Ltd. were austenitized at 950 °C for 5 min, and then hot stamped and quenched by using the flat die. The microstructure and mechanical properties were investigated by optical microscope, transmission electron microscope and universal testing machine. The results show that the microstructure after stamping and quenching is fully composed of lath martensite. The mechanical properties of the steel samples with different original structures are different after hot stamping and quenching, and this difference is smaller than that before hot stamping and quenching. When the original structure consists of ferrite and pearlite, the austenite grains after austenitization are fine and uniform. In addition, the martensite structure obtained after hot stamping and quenching is also uniform and fine, leading to higher mechanical properties. With the increase of the strength of the original steel, when the original structure is martensite, the austenite grains after austenitization are coarse, and the martensite structures obtained after quenching is also coarse, and thereby decreasing the strength.

scholarly journals Evolution of Phase Transition and Mechanical Properties of Ultra-High Strength Hot-Stamped Steel During Quenching Process

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 138 ◽  
Author(s):  
Shuang Liu ◽  
Mujun Long ◽  
Songyuan Ai ◽  
Yan Zhao ◽  
Dengfu Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Phase Transition ◽  
Cooling Rate ◽  
Hot Stamping ◽  
Coupled Model ◽  
High Strength ◽  
Austenitizing Temperature ◽  
Stamping Process ◽  
Quenching Process ◽  
Hot Stamping Steel

Hot stamping process is widely used in the manufacture of the high strength automotive steel, mainly including the stamping and quenching process of the hot-formed steel. In the hot stamping process, the steel is heated above the critical austenitizing temperature, and then it is rapidly stamped in the mold and the quenching phase transition occurs at the same time. The quenching operation in the hot stamping process has a significant influence on the phase transition and mechanical properties of the hot-stamping steel. A proper quenching technique is quite important to control the microstructure and properties of an ultra-high strength hot-stamping steel. In this paper, considering the factors of the austenitizing temperature, the austenitizing time and the cooling rate, a coupled model on the thermal homogenization and phase transition from austenite to martensite in quenching process was established for production of ultra-high strength hot-stamping steel. The temperature variation, the austenite decomposition and martensite formation during quenching process was simulated. At the same time, the microstructure and the properties of the ultra-high strength hot-stamping steel after quenching at different austenitizing temperature were experimental studied. The results show that under the conditions of low cooling rate, the final quenching microstructure of the ultra-high strength hot-stamping steel includes martensite, residual austenite, bainite and ferrite. With the increase of the cooling rate, bainite and ferrite gradually disappear. While austenitizing at 930 °C, the tensile strength, yield strength, elongation and strength-ductility product of the hot-stamping steel are 1770.1 MPa, 1128.2 MPa, 6.72% and 11.9 GPa%, respectively.

Influence of Ultra-Fast Cooling Technology on Microstructure and Mechanical Properties of Ti-Microalloyed Steel

2011 ◽  
Vol 337 ◽  
pp. 414-417
Author(s):  
Hai Long Yi ◽  
Yang Xu ◽  
Zhen Yu Liu ◽  
Guo Dong Wang ◽  
Di Wu
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Microalloyed Steel ◽  
New Technology ◽  
Good Effect ◽  
Air Cooling ◽  
Cooling Process ◽  
Ultra Fast Cooling ◽  
Fast Cooling ◽  
Cooling Technology

In recent years, the ultra-fast cooling process is a new technology used to control the strip cooling process in the international which corresponds to an average cooling rate higher than 150°C/s. This new technology can provide an effective means to the development of low-cost and high-performance steels. In this paper, the phase transformation temperatures, microstructures and mechanical properties of a Ti microalloyed steel were investigated by means of a themomechanical simulator and a D450mm mill equipped with ultra-fast cooling device. The results show that the phase transition temperatures decreased and micro-hardness increased with the increasing of cooling rate. The microstructures of steel used ultra-fast cooling process was small and more uniform than the ones used laminar flow cooling and air cooling process, and finer and uniformity dispersed precipitates can be produced under ultra-fast cooling process, hence higher yield strength and good elongation was obtained for the steel. The ultra-fast cooling technology has a good effect on the microstructures and properties of the Ti microalloyed steel.

Effects of cooling rate on the mechanical properties of dual phase treated vanadium steels

1983 ◽  
Vol 41 ◽  
pp. 220-221
Author(s):  
L.J. Chen ◽  
H.C. Cheng ◽  
J.R. Gong ◽  
J.G. Yang
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Automobile Industry ◽  
High Strength ◽  
Weight Percent ◽  
Low Alloy Steels ◽  
Dual Phase ◽  
Resource Requirement ◽  
Alloy Steels ◽  
Potential Weight

For fuel savings as well as energy and resource requirement, high strength low alloy steels (HSLA) are of particular interest to automobile industry because of the potential weight reduction which can be achieved by using thinner section of these steels to carry the same load and thus to improve the fuel mileage. Dual phase treatment has been utilized to obtain superior strength and ductility combinations compared to the HSLA of identical composition. Recently, cooling rate following heat treatment was found to be important to the tensile properties of the dual phase steels. In this paper, we report the results of the investigation of cooling rate on the microstructures and mechanical properties of several vanadium HSLA steels.The steels with composition (in weight percent) listed below were supplied by China Steel Corporation: 1. low V steel (0.11C, 0.65Si, 1.63Mn, 0.015P, 0.008S, 0.084Aℓ, 0.004V), 2. 0.059V steel (0.13C, 0.62S1, 1.59Mn, 0.012P, 0.008S, 0.065Aℓ, 0.059V), 3. 0.10V steel (0.11C, 0.58Si, 1.58Mn, 0.017P, 0.008S, 0.068Aℓ, 0.10V).

scholarly journals Investigation of the Microstructural Evolution during Hot Stamping of a Carburized Complex Phase Steel by Laser-Ultrasonics

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1836
Author(s):  
Alexander Horn ◽  
Marion Merklein
Keyword(s):  
Microstructural Evolution ◽  
Hot Stamping ◽  
Laser Ultrasonics ◽  
Complex Phase ◽  
Finished Steel ◽  
Steel Sheets ◽  
Fine Grain ◽  
Martensitic Microstructure ◽  
Ultrasound Sensor ◽  
Hot Stamping Steel

Prior carburization of semi-finished steel sheets is a new process variant in hot stamping to manufacture parts with tailored properties. Compared to conventional hot stamping processes, a complex phase typed steel alloy is used instead of 22MnB5. Yet recent investigations focused on final mechanical properties rather than microstructural mechanisms cause an increase in strength. Thus, the influence of additional carburization on the microstructural evolution during hot stamping of a complex phase steel CP-W®800 is investigated within this work. The phase transformation behavior, as well as the grain growth during austenitization, is evaluated by in-situ measurements employing a laser-ultrasound sensor. The results are correlated with additional hardness measurements in as-quenched condition and supplementary micrographs. The experiments reveal that the carburization process significantly improves the hardenability of the CP-W®800. However, even at quenching rates of 70 K/s no fully martensitic microstructure was achievable. Still, the resulting hardness of the carburized samples might exceed the fully martensitic hardness of 22MnB5 derived from literature. Furthermore, the carburization process has no adverse effect on the fine grain stability of the complex phase steel. This makes it more robust in terms of grain size than the conventional hot stamping steel 22MnB5.

Sign in / Sign up

Export Citation Format

Share Document