高頻電阻焊接高強度鋼管製程之研究

A Study on High Strength Steel Seamed Tube Manufacturing Process with High-Frequency Electric Resistance Welding

陳冠呈(Guan-Cheng Chen)

指導教授 ： 陳復國

國立臺灣大學/工學院/機械工程學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201902827

摘要

隨著汽車產業追求節能減碳和汽車電氣化，管件液壓成形工藝所生產出來的一體成形汽車結構件，逐漸取代傳統沖壓生產再焊接組裝部件，管件液壓成形工藝主要使用成本較低之有縫鋼管，其中又以高頻電阻焊管為首要選擇，原因在於其連續製程生產速度快、品質高等優點。隨著業界追求輕量化與高強度，製管廠也逐漸生產高強度鋼管。然而，高頻電阻焊接出來的高強度鋼管在壓扁試驗中很容易會有焊道開裂的情形，為了解決這項問題，本論文首先整理出製程中會影響焊接品質的因素，並從這些因素中選出最主要的三項：板邊對接型態、鋼帶帶寬與焊道焊流線，建立出有限元素模擬模型，進行深入研究。
本論文建立了焊道擠壓模擬模型，透過此模型重現焊道在擠壓過程中金屬的流向，分析結果與實際焊流線觀測結果有很大的相似性。更進一步使用此模擬模型觀測接合面高低差焊接而產生的焊道偏折缺陷、與接合面夾角V形對接型態產生的焊流線變化，研究結果可以提供現場生產時參數調整方向，不會因為製程中複雜的電、熱與變形關係而分辨不出缺陷產生原因。另外，本論文建立了輥軋成形模擬模型，探討能夠達到最佳I形對接型態時的上下帶寬值，並建立簡易模型與整理帶寬計算公式，減少取得最佳帶寬值所需的時間，讓這套帶寬取得方式更有實際應用的價值。
本論文的另一部分是在探討高強度鋼管經液壓成形工藝製造出扭力樑後，在端口處焊道表面出現芝麻孔缺陷的狀況。首先本論文建立擴孔試驗模擬模型與扭力樑液壓成形模擬模型，藉以了解焊道變形過程中的受力機制。接著，透過顯微鏡觀察芝麻孔型態，還有對退火處理與未退火試片進行硬度試驗。由這些結果中歸納出，焊道中含有焊接時生成的氧化雜質，位於表面的雜質因管材變形受到拉應力而掉出表面形成芝麻孔。最後，本論文透過更改焊道擺放位置與優化液壓成形中側推壓力路徑，來達到更低之焊道材料減薄率，避免芝麻孔缺陷的產生。
本論文所建立的輥軋成形模擬模型與扭力樑液壓成形模擬模型，皆以實際生產之實體樣件進行比對，模擬結果與實際測量值皆十分接近，藉此驗證模擬之準確性。

關鍵字

高頻電阻焊接鋼管 ； 高強度鋼 ； 輥軋成形 ； 管件液壓成形 ； 有限元素法

並列摘要

As the automotive industry pursues energy conservation, carbon reduction, and automotive electrification, one-piece tube-hydroformed parts gradually replace traditional stamping and assembly car parts. The hydroforming process mainly uses the low-cost seamed steel pipe, and the high-frequency electric resistance welded pipe is the primary choice because of its fast production and high quality. As the industry pursues lightweight and high strength, the tube manufacturing plant is gradually producing high-strength steel pipes. However, the high-frequency resistance welded high-strength steel pipe is prone to breaking at the weld bead in the flattening test. In order to solve this problem, this paper produces a detailed list of factors that affect the welding quality in the process. The three most important of these factors are the edge-contact type, strip width, and flow lines in the weld area, and finite element simulation models were established to conduct an in-depth study of these factors.
This paper establishes a weld bead squeezing simulation model, which shows the flow of metal during the squeezing process. The analysis results were very similar to the actual weld flow line observations. Further, using this simulation model, the weld bead deflection caused by the contact surface height difference, and the change of flow line caused by the V-shaped connection, are observed. The results can provide the direction of parameter adjustment during on-site production. Usually, due to the complex relationship between electricity, heat and deformation in the process, the cause of defects cannot be found. With the weld bead squeezing simulation model, this situation will not occur. In addition, a roll forming simulation model was established. This model is used to figure out the upper and lower strip width to achieve the optimal I-shaped connection. A simple model was then established and strip width calculation formulas were sorted out to reduce the time required to obtain the optimal strip width so that this strip width calculation method has more practical application value.
Another part of this thesis is to investigate the microporous on the surface of the weld bead at the connecting section of a twist beam, which occurred after the hydroforming process. Firstly, a flaring test simulation model and a twist beam hydroforming simulation model were established to understand the mechanism of stress during the deformation process. Next, the microporous was observed through a microscope, and the hardness test was performed on the annealed and unannealed test specimen. From these results, it is concluded that the weld bead contained oxidized inclusions generated during welding, and the inclusions located on the surface were subjected to tensile stress due to deformation of the pipe and fall off the surface to form microporous. Finally, this paper achieves lower thinning rate at the weld line and avoids microporous defects by changing the position of the weld bead and optimizing the loading path in the hydroforming process.
The roll forming simulation model and the torsion beam hydroforming simulation model established in this paper are all compared with the finished product. The consistency between the measured data and the predicted values validates the accuracy of the finite element simulation results.

並列關鍵字

high-frequency electric resistance welded pipe ； high strength steel ； roll forming ； tube-hydroforming ； finite element analysis

參考文獻

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