車用高強鋼MAG焊焊接工藝研究[純論文]【YC系列】

車用高強鋼MAG焊焊接工藝研究[純論文]【YC系列】,純論文,YC系列,高強,mag,焊接,工藝,研究,鉆研,論文,yc,系列 摘 要 高強鋼中的雙相鋼和熱軋微合金鋼不僅具有較高的強度還具有較好的塑性，與傳統(tǒng)的低碳鋼和低合金高強鋼相比，具有強大的優(yōu)勢，因而廣泛應用于汽車工業(yè)上。針對RCL540鋼電阻對焊后成形過程中開裂率比SPFH540鋼高的問題，本文對兩種鋼的成分、組織、性能進行了深入分析。此外利用正交試驗設計法及單因素變量控制法對輪輻材料DP600雙相鋼分別和輪輞用鋼RCL540、SPFH540的MAG焊搭接工藝進行了優(yōu)化。 以2mm 厚RCL540鋼板和SPFH540鋼板為研究對象，對其進行了成分、組織、性能研究。結果表明：兩者的微觀組織主要是鐵素體和珠光體。和RCL540鋼相比，SPFH540鋼具有更低的S含量與碳化物形成元素含量。分析認為較高的S含量，力學性能不均勻，是RCL540鋼電阻焊后開裂率比SPFH540 鋼高的主要原因。 利用正交設計法對4mm厚的DP600雙相鋼分別與2mm厚的RCL540鋼、SPFH540鋼的MAG焊搭接工藝進行了優(yōu)化，研究了主要參數對焊縫成形、力學性能、金相組織的影響。實驗結果顯示：焊接電流和焊接速度是影響熔深的主要因素。對工藝進行優(yōu)化后，搭接接頭的薄板熔深滿足率分別提高為原來的1.5倍（RCL540鋼）和2倍（SPFH540鋼）。搭接間隙為0.24mm時，熔深減少0.3mm。鋼中的氧化物類別會影響材料的沖擊韌性，RCL540鋼的氧化物為脆性的Al2O3，SPFH540鋼的氧化物為Mg、Ca、Al、S的復合型氧化物，氧化物類型的差別導致RCL540的沖擊功比SPFH540的沖擊功約低4.5J。此外余高較大時沖擊韌性降低。 利用單因素變量控制法研究了不同氣體流量和不同混合氣配比對焊縫成形的影響。結果表明：氣體流量小于等于15L/min時保護效果不好，容易出現大尺寸的氣孔；混合氣配比也會影響焊縫的成形，焊縫的熔深隨著混合氣中CO2含量的提高而有所增加，但是隨著CO2含量的增加，焊接接頭的沖擊韌性會降低。 最后對填充材料ER50-6和母材的匹配特性進行了分析，在分析其存在的不足后，秉著“成本低、性能好”的原則，挑選了低合金鋼焊絲ER70S-6和ER70S-G兩種焊絲。在同等焊接參數對比實驗中發(fā)現：利用ER70S-6與ER70S-G焊絲進行焊接時，熔池的流動性更好，熔深能增加0.3-0.5mm，沖擊功稍有提高。 關鍵詞：高強鋼；MAG 焊；焊接工藝；力學性能；微觀組織 Abstract Dual-phase steel and micro-alloyed steel both have the comprehensive benefits, such as high strength and good ductility. They have a lot of advantages over raditional mild steel and low alloy high strength steel. So recent years they areapplied widely in automobile industry. During manufacturing and forming RCL540 steel plate and SPFH540 steel plate into wheel rims, a major problem was cracking of wheel rims. To solve the problem, this paper made a systematic research on chemical composition, mechanical properties, and microstructures of RCL540 steel and SPFH540 steel. And comprehensive analysis of weldability differences was made between RCL540 steel and SPFH540 steel during resistance butt welding. Besides, utilizing the method of orthogonal design and univariate variable control,the process of metal active welding was optimized. Aiming to 2mm RCL540 and SPFH540 steel plate, experiments of chemical composition measuring, microstructures observation and mechanical properties tests were done. The results proved that, comparing to RCL540 steel, SPFH540 had the lower sulfur content and Lower carbide forming content. Microstructures of themwere mainly ferrite and pearlite. However, SPFH540 had severe banded structure. The tensile strength of RCL540 differed obviously in the parallel rolling direction and the perpendicular rolling direction. High strength and higher sulfur content were the main reason that RCL540 steel plate has the larger cracking ratio. Orthogonal design was applied to get the better parameters for metal active welding. The influence of main factors (welding current, arc voltage, welding speed on shaping ability, mechanical properties and microstructure were investigated. The investigation showed that welding current and welding speed were the main factors which affected depth of penetration. Because of the differences in oxide, SPFH540 steel welded joints had 4.5J larger impact energy than RCL540 steel welded joints. While RCL540 steel welded joints had the oxide of Al, SPFH540 steel welded joints had the oxide of Mg, Ca, S, Al. Besides, the excess height was high, the impact strength was cut down. In addition, the effects of protective gas flow and mixing ratio on formation of joints and protective efficiency were studied. It revealed that when the gas flow was too small, protective efficiency would be influenced. It would be easy to produce gas cavity. Protective gas mixing ratio would also affected the shape of weld. As the fraction of CO2 got larger, the depth of penetration of 2mm steel plate would turn deeper. However, the surface was not so beautiful and the impact energy would decrease.At last, when using ER50-6 welding wire rod, matching mode of deposited metal and base metal was researched. The matching was under strength matching.After learned the shortcomings of ER50-6 welding wire rod, at the principle of “l(fā)ow cost, high efficiency”, two low alloy welding wire rod were chosen. At the same welding condition, the joints which used the ER70S-6 welding wire rod and ER70S-G welding wire rod had a little higher impact energy. 【Key word】high strength steel, MAG welding, welding procedure, mechanical properties, micro-structure 目 錄 摘 要 I Abstract II 目 錄 III 第1章 緒論 1 1.1課題的來源及研究意 1 1.2車用高強鋼的發(fā)展和分類 1 1.3車輪用鋼焊接的研究現狀 3 1.4本課題的主要研究內容 6 第2章 RCL540與SPFH540鋼的組織與性能分析 8 2.1熱軋高強鋼RCL540與SPFH540成分與焊接性分析 8 2.2 RCL540鋼與SPFH540鋼的力學性能對比 10 2.3 RCL540鋼與SPFH540鋼的微觀組織分析 12 2.4 本章小結 14 第3章 高強鋼MAG焊的工藝優(yōu)化 15 3.1高強鋼MAG焊正交試驗 15 3.2焊接工藝參數對焊縫力學性能的影響 22 3.3 MAG焊焊縫金相組織分析 29 3.4保護氣對焊縫成形的影響 30 3.5本章小結 33 第4章 焊絲材料的選擇 34 4.1焊絲優(yōu)選的理論依據 34 4.2 ER50-6焊絲與母材的匹配特性 34 4.3優(yōu)選焊絲與ER50-6焊絲綜合對比 35 4.4本章小結 38 結 論 40 參考文獻 41 IV