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High strength steel has been increasingly used in auto body design to achieve lightweight and safety. Recently WISCO made great efforts in research and development of HSS, including new grades development, new forming technology research and application. DP780 as a typical UHSS had been widely applied in car body parts after deep investigation in all kinds of properties. Springback analysis and welding test had been carried out to have better understanding in different grades of HSS. Roll forming, as an efficient forming technology, had been successfully applied in processing WISCO's hot rolled high strength steel product used for bus body. Many Optimizing methods were researched and utilized to provide high quality roll formed parts to customers. In hot forming area, WISCO had been working on boron steel development, tool design, whole process technology, tailed blank design, and post-treatment for part surface for long time. A lot of novel research results showed that hot forming will be more and more important in lightweight and safety for the future vehicles.

Hot forming of boron steel has become increasingly popular due to the demand of both weight reduction of body parts and enhanced safety for passengers. The most commonly used boron steel grade for hot forming is 22MnB5, with an ultimate tensile strength of ~1,500MPa and quite low total elongation of ~6% in the martensitic state. Recent research mainly focused on improving the ductility of hot formed steels by either introducing a post-hot forming tempering treatment for 22MnB5 or developing an alternative class of hot formed steels such as a medium Mn steel. However, the dimensional variability of the cold-stamped TRIP parts is too high due to the high instantaneous plastic modulus at all strains; whereas hot forming provides a new opportunity for these types of steel grades. This present work will focus on the microstructure characteristics and mechanical behavior of the warm-rolled 0.17C-6.5Mn-1.1Al-0.22Mo-0.05Nb steel, and compared with the commercial hot formed 22MnB5 steel and the conventional multi-stage thermo-mechanical process including hot rolling, cold rolling and intercritical annealing. It can be concluded that the microstructure and mechanical characteristics strongly depended on the warm rolling temperature. The best combination of UTS and TE (~32.0GPa%) was achieved in the 660°C-warm rolled specimen, which is much higher than 12.3GPa% for the hot formed 22MnB5 steel, and is also comparable to 38.3GPa% for the annealed CR specimen.

In order to enhance the hot-quenching steel's comprehensive performance, a C-Si-Mn-Ti-B hot forming steel is designed. By the means of experiment, WHF1300R/D steel's micro metallographic structure and mechanical performance in the procedures of hot rolling, annealing and hot stamping is studied and it performs good hardenability. Through the hot forming technic experiment, the most appropriate cooling velocity is found, which inhibits the formation of pearlite and bainite effectively. The microstructure of the hot-stamped WHF1300R/D steel sheet is composed of lath martensite. The strength and ductility of the hot-stamped WHF1300R/D steel sheet are matched well with a tensile strength of about 1300MPa and a total elongation up to 12%.

To improve the mechanical properties of hot formed part, in this paper, a new hot forming process combined with quenching and partitioning treatment is proposed. In the new process, tools with high temperature are used to control the quenching temperature between M_s and M_f, and carbon partitioning process is carried out in the furnace. The results show that the mechanical properties of different area (with different quenching temperature) of the part are different. So the key problem of the new process is to how to control the quenching temperature and broaden the process window.

Paper presents advanced innovative design of continuous roller furnace. These types of furnaces are generally used in hot stamping / press hardening lines. Design is focused on optimal heating layout, modern drives of rollers, new design of furnace's input and output without movable parts and other items respecting the optimal technological and technical aspects. Also the technological functions like the dew point temperature regulation, oxygen rate regulation with permanent monitoring function are described. All results are based on the theoretical background of heat and mass transfer, confirmed by numerical FEM analysis and of course long term experience from real hot forming production.

Due to the strict requirements from the government for CO₂ emission of vehicles, Light-Weight design is now one of the most important and popular topic in automotive manufacturing. Therefore, the hot forming steel, as a high strength material, is used for manufacturing of more and more automotive body parts. And the laser is now a mandatory tool in the manufacturing. TRUMPF, as a leader of Laser manufacturing technology, is devoting its effort to improve the existing laser processes, such as 3D laser cutting, laser ablation of Al-Si coating and laser welding of patchwork. Meanwhile, we're also developing new applications for manufacturing of hot forming parts, such as laser softening of the hot forming parts on a certain area for diverse purpose. This paper demonstrates our latest development and new trends of the laser applications for hot forming parts.

Hot stamping door bumper cracked after cold bending and placing for 24 hours. This paper analyzed the reasons for cracking by measuring the mechanical properties, chemical composition, microstructure, hydrogen content, hardness and observing tensile and crack fracture of the sample which were taken from the hot stamping door bumper. The analysis results show that the steel microstructure, mechanical properties and hardness were in line with the relevant requirements of 22MnB5. The cracking fracture, which were divided into different regions, showed a typical hydrogen induced delayed fracture morphology. Some stress included hot stamping organizational stress, thermal deformation stress and cold bending deformation stress, and the hydrogen induced delayed fracture caused by quenched martensite sensitivity to hydrogen embrittlement, were the main reason causing the cold bending of the door bumper.

Here in this paper, a multiscale framework based on crystal plasticity is proposed coupling with thermal activation mechanism, as well as the continuum damage mechanism. The microscopic hardening phenomenon is revealed by a dislocation density evolution model, which is constructed according to the temperature. The physical-based exponential function of shear strain rate is posed to describe the thermal material behavior replacing the general phenomenological power-law equation. A 3D spatial distribution of stress, strain and damage is presented in the finite element method, parameters of which are previously determined by a RVE calculation and fitting test compared to the experimental data. Finally, some discussions of stress heterogeneity and texture evolution are proposed and conclusions are made.

In vehicle crashworthiness simulation analysis, anti-crash performance of the front bumper beam assembly of auto body made of 22MnB5 by hot forming and high strength steel by cold forming is compared. Software PAM-CRASH is employed to analyze the energy absorption and the acceleration value of beams with different profiles and thicknesses during the frontal impact process. And the structure of the hot forming bumper beam is optimized to get more light-weight effect. The results show that the use of hot forming beam can not only improve the energy absorption, but also can effectively reduce the weight of the body in white.

The traditional hot forming product has high strength, but the plasticity is usually low and comprehensive mechanical performance is not high. In order to improve the comprehensive mechanical properties, the variable gradient characteristics of forming technology has been drawing more and more attention and has become a research hot spot in hot forming control technology. The variable gradient characteristic is different from the traditional pressure processing and has its own characteristics in numerical simulation. It belongs to the problem of the intersection of pressure processing, material science and computational mechanics. In this paper, the main numerical simulation differences between the hot stamping process and traditional pressure processing are summarized. We take a non-uniform initial heating temperature field to form the variable gradient component by hot stamping as the research object, and a finite element model is established in order to analyze the key influence factors of the hot stamping to form the variable gradient characteristics parts. The initial sheet is divided into high temperature and low temperature regions. The simulation and the forming process satisfy certain stamping and quenching conditions. The simulation results shows that stamping speed, the die temperature and the holding time are the important influence parameters in the variable gradient characteristics hot forming process.

Aluminum alloys, such as the 6082 alloy, is now becoming established for future lightweight vehicle structures, while Magnesium alloys remain a specialist material. By developing a low-cost, massproduction route for sheet magnesium, designers can start to explore the use of pressed magnesium panels into future vehicles. In this work, it is presented the feasibility study for an application and development of a hot forming technology to the forming an automotive external body (skin) panel. The reported forming trials of the front cowl panel were conducted using AA6082 and AZ31b alloys.

In this paper, the contents mainly include two aspects, one of which is the study of Q&P parameters effects, the main parameters are quenching temperature, partition temperature and partition time. Several groups experiments are carried on under different conditions, the results are determined by the tensile strength and elongation rate which are obtained by tensile test. The second is to carry out experiments on U shaped parts in the same conditions respectively with the traditional hot formingquenching process and Q&P process, comparing the effect of Q&P and traditional hot forming process on springback, the results of springback are evaluated by the rebound angle. Finally, by analyzing and summarizing the experimental results, finding that Q&P process has little influence on springback.

This paper presents an advanced innovative design of a continuous roller furnace. These types of furnaces are generally used in hot stamping / press hardening lines. Design is focused on optimal heating layout, modern drives of rollers, new design of furnace’s input and output without movable parts and other items respecting the optimal technological and technical aspects. The cycle time of the hot forming process is a function of several technical parameters. Also the technological functions like the dew point temperature regulation, oxygen rate regulation with permanent monitoring function are described. All results are based on the theoretical background of heat and mass transfer, confirmed by numerical FEM (Finite element method) analysis.

The boron alloyed steel can get ultra-high strength after hot forming process, which can improve the safety while realizing automobile lightweight. So HFS has been used more and more widely. Ma steel has developed HFS since 2013. At present, the HFS produced by Ma steel covers 1300MPa∼1800MPa, we can supply the HFS by different product category, such as HR, PO, CR and coated product. In the frontier research of HFS, Ma steel has developed zinc based and high bendability HFS, which have been recognized by customers. On the other hand, in the research of hot stamping technology, TRB and TWB products developed by Ma steel and its partner were used in hot forming parts, which provide a more extensive way for vehicle lightweight selection.

Hot formed part is widely used in the automotive industry to meet increasing requirements of safety and light weight. However, the corrosion protection is also a major aspect for automotive materials. For this reason, aluminized, galvanized and galvannealed hot forming steels were developed. Here the corrosion resistance of hot formed zinc-based coating was evaluated by cycle corrosion test. And it was compared with aluminum-silicon coated steel.

To improve the formability and productivity in cold stamping of aluminum alloys, warm forming and hot forming processes were developed, in which heating process plays an important part. This paper presents investigations on direct contact heating of aluminum sheets by the approach of modeling. The influence factors of working face temperature uniformity of the direct contact heating device were studied, as well as the continuous heating of aluminum sheets by direct contact heating process. Simulation results indicate that direct contact heating process can realize continuous quick heating of aluminum sheet, and the solution heat treatment of aluminum alloys can also be achieved. In the process of direct contact heating, the heating time is short, the temperature of the heated sheets is relatively uniform, and there is little difference of temperature distribution between different sheets in same heating condition. The direct contact heating process represents a feasible as well as time-saving alternative for the heating of aluminum alloys.

To eliminate laser cutting for hot formed part, hot blanking process for hot forming of press hardened steel were developed. Hot blanking process is finished between forming and final quenching during the hot stamping. The effects of different blanking parameters on quality of blanked surface are studied in this paper. The results provide a reference for the actual hot blanking process and tool design.

Use of press hardened parts in BIW (Body in White) structures has evolved in recent years to encompass a wide range of part complexity, size and mechanical properties. In addition, the number of components per vehicle has also increased pushing demand for more capital investments. Suppliers of press hardened parts need to accommodate these changes while staying competitive. Advanced design of heat treatment furnace has to offer a unique furnace design that provides flexibility to handle future part sizes, minimizes down time to increase line utilization and offers a unique solution to produce tailor tempered parts for crash performance. This paper presents advanced innovative design of continuous roller furnace. These types of furnaces are generally used in hot forming lines. Design is focused on optimal heating layout, modern drives of rollers, new design and other items respecting the optimal technological and technical aspects. Technological functions like the dew point temperature regulation, oxygen rate regulation are considered. Based on the long-time experiences with manufacturing and development of the machinery for the automotive industry, new roller furnaces were designed using modern methods including the FEM analyses for numerical simulations of heating processes and heating power distribution. The numerical solution of many mathematical problems involves the combination of external and internal conditions and different technological processes.

Press hardened Boron steel is still gaining importance for automotive body parts because of its advantageous material properties. For forming and hardening the flat metal sheets are heated up to Austenite temperature, transferred to the dye, high speed formed and hardened — while cooling down within the forming tool [1]. This process leads to high strength properties of about 1500 MPa and is used for weight reduction purposes in car design [2]. The combination of heat treatment and forming is also strongly influenced by the cooling gradients within the forming tool. High cooling gradients lead to bainitic and martensitic structure formation — structure parts which show high hardness [3]. Car manufacturers look into the application of flaps in the design of car body parts. Using flaps within the assembly process is helpful for part-positioning. In case of already press hardened Boron steel it is necessary to perform a heat treatment before bending to prevent crack formation in the bending zone. This paper shows how this process can be performed most efficiently within the laser cutting machine. Soft areas for rivet points to facilitate joining operations and ductile flange areas or complex 3D-contours to improve crash performance can also be realized by this technology. This paper shows a specially designed line optic for these applications.

Hot stamping parts have been widely used as re-enforcement for better crash safety and other attributes as well as in lightweight applications such as vehicle B-pillar, rocker and other structure parts. In this paper hot stamped torsion beam is studied as a function of product DVP and hot stamping process. Although hot-stamping process is fairly understood, the lightweight designed torsion beam’s property as a function of various parameters is not well studied. In order to study the temperature field, stress field, strain field, thinning rate and phase distribution in the hot forming process of torsion beam, the finite element software was used in this paper. The study found the maximum principal strained area appeared in the highest temperature region due to the different regions of part contact with the tool in the different order while the maximum principal stress area is located in the lower temperature region. In the process of hot forming, the slow cooling rate of the part is 77 °C/s, which is greater than critical cooling rate of martensitic transformation 30 °C/s; With the increase of the initial temperature of sheet metal, the maximum content of austenite and thinning rate of the parts increase, and the forming quality of the parts decreases; with the increase of stamping speed, the thinning rate of parts is violent fluctuation. When the stamping speed is too large, parts of the temperature of parts is greater than the martensite transformation temperature in some regions at the end of forming; with the increase of friction coefficient, the thinning rate and the minimum content of martensite firstly increase and then decrease; the maximum content of austenite decreases first and then increases. Research shows that: when the initial temperature of blank is 850, stamping speed is 75 mm/s, coefficient of friction is 0.45, the quality of the parts is the best and thinning rate is 5.804 %. At the end of forming, the minimum temperature of parts is 285 °C; minimum martensite content is 75.63 % and the maximum content of austenite is 24.36 %.