A new integration of hot pressing and carbon partition process to produce high strength steel components with better toughness

Abstract

Abstract.A novel one step method for hot pressing and quench & partition (Q&P) integration -hot Pressing-dynamic partitioning (HP-DP) process is presented, which can be processed by regular hot pressing equipment and process. The HP-DP formed steel is an upgrade of the existing hot pressed steel especially suitable for making high strength components with superior crashworthiness due to better toughness. Corresponding steel sheet based on conventional 22MnB5 is designed and prepared. After that, the physical simulation experiments for HP-DP are carried out on thermal-mechanical simulator. Microstructure of the steel subjected to HP-DP treatment, with a typical Q&P treated feature, is mainly composed of initial quenched martensite phase, final quenched martensite phase and retained austenite phase, which indicate the occurrence of carbon diffusion concomitantly with martensite transformation. Compared with conventional hot pressed samples, the HP-DP samples show both better tensile property especially elongation and impact energy absorption ability. The effect of HP-DP parameters on the stability of retained austenite and mechanical property is also discussed. The paper illustrates the promising application potential of the HP-DP process.

Microstructure and mechanical properties of a hot pressing-dynamic partition treated steel

“…And a further examination of martensite indicates existence of both dislocation and twinning martensite phases. As the occurrence of twinning martensite needs the carbon content of mother austenite higher than 0.6 wt-% [10] and the carbon content of initial austenite is 0.19 wt-%, which means the carbon enrich process in austenite (carbon partition from martensite to austenite) happened during cooling below 310°C (corresponding to the martensite transformation region). The austenite with high enough carbon content can have good stability to remain at room temperature and the austenite whose carbon content is not high enough to get stability could be transformed to twinning martensite.…”

“…The chemical composition of the HP-DP steel studied in this work is Fe-0.19C-1.55Si-1.53Mn-0.95Ni-1.01Cr-0.45Mo-1.01Cu-0.033Ti-0.0027B-0.025Al (wt-%) as reported in [7,9,10]. The steel was melted in a vacuum furnace, hot forged to a slab of 60 mm thickness and hot rolled to the blank of 4 mm thickness.…”

“…The feasibility of the process was proved by physical simulations and high PSE level up to 25,600 MPa% with a tensile strength of 1600 MPa and an elongation of 16% could be achieved in the developed low-carbon press-hardened steels. The results have been reported in [10]. In this paper the detailed characterisation of microstructure and mechanical properties of steels treated by the HP-DP process were presented and newly carried experiments for the formed sheet part using the HP-DP process will also be shown to validate the practical feasibility of the HP-DP process for industrial application.…”

“…Following this, the authors of this paper proposed the integrated hot pressing and dynamic partition (HP-DP) process [9,10]. The feasibility of the process was proved by physical simulations and high PSE level up to 25,600 MPa% with a tensile strength of 1600 MPa and an elongation of 16% could be achieved in the developed low-carbon press-hardened steels.…”

Modeling the Evolution of Casting Defect Closure in Ingots through Radial Shear Rolling Processing

“…This technique is widely employed for the production of rods, reinforcement, wires, and various materials featuring a circular cross-section [12,13]. Drawing [14] and hot pressing [15] are alternative methods. Drawing finds its primary application in wire production [16] and occasionally in bar production [17], while hot pressing is mainly utilized for the production of complex cross-section short profiles [18].…”