高強度鋼板熱沖壓與固接複合成形技術之研究

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

黃建銘(Jian-Ming Huang)

指導教授 ： 許源泉

共同指導教授 ： 陳立緯

國立虎尾科技大學/工程學院/機械與電腦輔助工程系碩士班/碩士(2015年)

https://doi.org/10.6827/NFU.2015.00138

摘要

板金沖壓固接複合成形是利用板材的冷變形能力，對板材進行加壓，使板材產生局部變形並連接在一起的一種新連接技術，與傳統的鉚接製程相比，其具有良好的密封性、防腐蝕性、加工製程簡單以及高連接強度(抗拉強度與抗剪強度)等特點。本研究嘗試將此技術與高強度鋼板熱沖壓技術結合，利用有限元素軟體DEFORM-3D對CSC-15B22高強度鋼板進行板金熱沖壓固接複合成形製程分析，以瞭解板材成形時之溫度變化與板材成形後之強度變化、速度場分佈、應力、應變以及頸部厚度與互鎖值對連接強度(抗拉強度與抗剪強度)之影響，進一步探討模具應力、模具冷卻與浮料銷設計等相關參數研究，再以實驗去佐證其準確性，並檢測板材成形後之外型、頸部厚度與互鎖值、模具溫度以及板材冷卻淬火時間等，同時也進行微觀組織、維氏硬度與抗剪強度等分析。
研究發現，冷卻水道的設計能有效帶走板材以及板材傳遞至模具上的溫度，經過十次熱沖壓製程週期後，其模具溫度仍維持在59℃左右；浮料銷能防止高溫板材成形前就與模具表面接觸，使溫度極度散失，有、無浮料銷設計之板材溫差達300℃以上；因人為因素而造成互鎖值之模擬與實驗的誤差雖達35%，但模擬與實驗的趨勢一致，故有限元素軟體DEFORM-3D具有相當的參考價值；CSC-15B22高強度鋼板經熱沖壓製程轉換後之材料組織已從肥粒鐵與波來鐵變成麻田散鐵，板材未成形處與原始素材之維氏硬度相比，已從209.7Hv提升至407.2Hv，對應之抗拉強度也從669.851MPa提升至1320.91MPa；不同板材連接之研究發現，硬質上板材與軟質下板材組合之抗剪強度是相同板材材質組合之抗剪強度的7.33%，厚上板材與薄下板材組合之抗剪強度是相同板材厚度組合之抗剪強度的16.91%，故硬質上板材與軟質下板材的組合以及厚上板材與薄下板材的組合之抗剪強度會比相同板材材質與厚度組合之抗剪強度高。

關鍵字

高強度鋼板 ； 有限元素分析 ； 熱沖壓固接 ； 頸部厚度 ； 互鎖值 ； 連接強度 ； 微觀組織

並列摘要

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.

並列關鍵字

High Strength Steel Sheets ； Finite Element Analysis ； Persistent Hot Stamping ； the Neck Thickness ； Interlock ； Connecting Strength (Joining Strength) ； Microstructures

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