Numerical Simulation Investigation on the Temperature Field Distribution and Variations in Hot Stamping Process
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With finite element software Abaqus, a coupled thermal mechanical simulation of hot stamping process of U-Channel part using high strength steel was performed. Through the analysis of the temperature field distribution on the die surface, the influence of contact state between die and blank on the temperature field distribution was discussed. With temperature history curve of a selected node on die corner, the heat flow on two contact boundaries (die surface and cooling water channel surface) was discussed and its effects rules on the die temperature were given.Keywords:
Blank
Hot stamping
Stamping
Full-scaled hot stamping dies were designed for a vehicle bumper, based on evaluation of cooling system by FE simulation and the temperature variation assessment by analytical model. The blank shape was gained using inverse algorithm and well-designed according to production practice. Experiments were conducted to verify the reliability of both the die and blank design, as well as tests for microstructure and mechanical properties of the hot-stamped part. Results show that, CAE analysis provides a robust support for hot stamping die and blank design; Position stability of hot blank is greatly improved during robotic transport process after shape designing; Metallographic analysis demonstrates the hot-stamped bumper obtained a fully martensitic microstructure, its tensile strength is about 1550 MPa, microhardness is 47.5 HRC, and the elongation is up to 6%.
Blank
Hot stamping
High strength steel
Stamping
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Abstract Usually, the exact geometry of the blank of a stamping is obtained by successive corrections of a presupposed blank subjected to the operation of stamping or its simulation. This paper presents an innovating method of direct predetermination of the blank. The part is set flat that it gives the required part when subjected to the action of the tool for stamping. The setting flat presents splits and the part carried out some discontinuities. The setting flat is then deformed to reabsorb the splits and the shape thus obtained is the optimized blank. This method is illustrated and validated on a rectangular cup by a comparison between the calculated blank and the part obtained.
Blank
Stamping
Classification of discontinuities
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The hot stamping process parameter of high strength steel is the key factor to influence the quality of part. The hot stamping finite element model( FEM) of the U-shape part was established,and the coupled thermo-mechanical numerical simulation was adopted to obtain the blank temperature,thickness and stress distribution during hot stamping process. Based on this,the orthogonal experiment was adopted to study the influence degree of the four process parameters such as the blank initial temperature,the die initial temperature,the stamping speed and the blank holder force to the lowest temperature and the maximum stress of the U-shape during hot stamping. The results show that the influence of the blank initial temperature is largest. Along with the blank initial temperature decreasing,the lowest temperature of the U-shape after stamping will decrease and the greatest stress value will increase substantially. The die initial temperature changing has the minimum affect on the lowest temperature and the maximum stress value changing of the U-shape after stamping. The influence of the stamping speed is quite large. Along with the stamping speed decreasing,the lowest temperature of the U-shape after stamping will decrease and the greatest stress value will increase. The blank holder force changing does not influence the heat transfer between the blank and die. Along with the blank holder force decreasing,the lowest temperature and the maximum stress value of the U-shape after stamping will decrease and change lesser in an area.
Blank
Stamping
Hot stamping
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Blank
Stamping
Deep drawing
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Due to the demands to reducing the gas emissions, energy saving and producing safer vehicles have driven the development of ultra high strength steel. Since the mechanical properties of ultra high strength steel are remarkably high, it has become a major setback for forming process and this has led lead to the development of special forming technique for ultra high strength steel called Hot Stamping. In hot stamping, the ultra high strength steel blank is heated to its austenization temperature of about 900 - 950 ◦C inside the furnace. Then, the heated blank is transferred to the tool where forming takes place and simultaneously quench the blank inside the tool. As the tool dwells, the microstructure of the blank becomes fully martensite thus giving the final part strength of up to 1500 MPa. In order to have a better understanding of the Hot Stamping Process, a numerical model of heat transfer need to be developed to simulate the temperature changes of the blank as well as validate the heat transfer coefficient (HTC) of the blank and tool contact surface as a function of distance and time. The numerical model is based on the heat transfer at the contact surface between the ultra high strength steel blank (Boron Manganese Steel) and the tool made of Tool Steel (SKD11).
Blank
Hot stamping
High strength steel
Stamping
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In the hot stamping and quenching process of ultra high strength steels,the formability and the final mechanical property of the steels are directly influenced by the heat transfer condition between the blank and the die.The heat transfer of the blank in the hot stamping and quenching process was analyzed by analytical method.According to the heat transfer behavior of the steels,the whole heat transfer process was divided into three phases:transfer to air,transfer to die and the mix of air and die.The analytical model was proposed to describe the relationship between the temperature change and time in different phases and verified by experimental investigation.Results show that there is acceptable agreement between the analytical model and the experimental results,and the temperature of steel blank calculated by the proposed model can reflect the law of the steels temperature change during hot stamping process.The proposed model will provide necessary and reliable basis for the further investigation and application of the hot stamping and quenching process.
Blank
Hot stamping
Stamping
High strength steel
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In hot stamping process, (UHSS) blank was cut into the rough shape. The blank is then heated to the temperature (900 - 950 °C) for 5 to 10 minutes inside the furnace. Then, the blank must be transferred quickly to the press to avoid the part is cooled before forming. After that, the
blank is formed and cooled simultaneously by the water cooled die for 5 to lOs. Due to the contact between hot blank and the cool tool, the blank is cooled in the closed tool [1]. Today, hot stamping exists in two different types of methods which are direct and indirect. For indirect hot stamping method, before the blank is heated inside the furnace, it then undergoes cold pre-forming process. This process is done once after the blank is cut.
Blank
Hot stamping
Stamping
Hot rolled
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Blank
Trimming
Stamping
Hot stamping
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Objective To study the temperature distribution and phase transformation of blank in hot stamping process.Methods The thermo- mechanical model was established in Abaqus software to simulate the U- shaped part forming and quench cooling process. The temperature distribution of blank and die and cooling rate were analyzed in this study. The hot stamping experiment was conducted to validate the simulation. Results The results showed that the temperature of blank was uniformly distributed after the quench cooling process. The cooling rate of blank was greater than the critical cooling rate and the martensitic phase transformation occurred completely in the blank. Conclusion The microstructure was all fine martensite and distributed uniformly at the bottom owing to its fastest cooling rate among the three areas of the blank. The accuracy of simulation was verified with the hot stamping experiment.
Blank
Hot stamping
Stamping
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Abstract The dispersion of blank masses depending on the accuracy class of the initial metal rolling is estimated. The influence of the method of the initial blank segments on the stamping process is described.
Blank
Stamping
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