Investigation of the Clinching Process Combines with Hot Stamping Process for High-Strength Steel Sheets

• Main Authors: Jian-Ming Huang, 黃建銘
• Other Authors: 許源泉
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/5cfcgu

碩士 === 國立虎尾科技大學 === 機械與電腦輔助工程系碩士班 === 103 === The clinching process is a technique using punches and dies for activating local deformation of the sheets at low temperature, and then connecting the sheets each other. This technique is different from a traditional clinching process, because this technique results better seal property, well corrosion resistance, machining process simplifying, and stronger connecting strength (tensile strength and shear strength). The present research utilized the finite element analysis software DEFORM-3D to simulate the clinching process with hot stamping process for the high strength steel (CSC-15B22). The simulations are to present the temperature distribution and variation, the strength distribution on sheets, velocity field, stress, and strain conditions while conducting sheet forming, and to analyze how the connecting strength (tensile strength and shear strength) be affected by the neck thickness and interlock values. Furthermore, to study the parameters of die stress, cooling system, and the lifter floating pin design. The experiments are to validate the accuracy of our simulations, including the appearances of sheets, the neck thickness, the interlock values, the die temperatures and cooling rate etc. To realize the hardness and strength variation of sheet forming zone after hot stamping process and between the sheets of the shear strength, analyses of microstructure, Vickers hardness and shear strength are applied. Results have indicated that the cooling channel design could maintain the die temperature at around 59 ℃ after ten hot stamping process cycle and effectively took heat away from the sheet. The floating pin is reliably prevent the heat loss while the hot temperature sheets contacting the mold surface, otherwise the temperature difference between the sheet can be above 300 ℃ without floating pin. The human factors caused the interlock values deviation between simulations and experiments are up to 35%, but the simulation and experimental trends are coinciding. Therefore, the simulation results of the finite element software, DEFORM-3D, represented convincing reference. After hot stamping process conversion, microstructure of CSC-15B22 high strength steel sheets had been turned from ferrite and pearlite into martensite. While comparing properties of the deformed area and raw sheets, not only the Vickers hardness had changed from 209.7Hv to 407.2Hv but also the tensile strength had gone from 669.851MPa up to 1320.91MPa. The shear strength of combining hard upper sheet and soft lower sheet is 7.33% of the combination with two same sheets. The shear strength of combining thick upper sheet and thin lower sheet is 16.91% of the one with two sheets with the same thickness. Therefore, shear strength of the different sheets combination are stronger than that with duplicate sheets.