本文關(guān)鍵詞：車用先進(jìn)超高強(qiáng)度鋼板光纖激光焊接接頭的顯微組織和力學(xué)性能的研究　出處：《上海工程技術(shù)大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 光纖激光焊接 超高強(qiáng)鋼 雙相鋼 顯微組織 力學(xué)性能

【摘要】：節(jié)能、環(huán)保、安全是當(dāng)今汽車制造業(yè)的三大主題,而汽車輕量化是各大汽車公司實(shí)現(xiàn)汽車低油耗、少廢氣排放的主要措施之一。先進(jìn)超高強(qiáng)度鋼以其抗拉強(qiáng)度高、能量吸收率高和碰撞后不易發(fā)生變形等優(yōu)勢,迅速發(fā)展成為重要的汽車輕量化材料。目前激光焊接技術(shù)作為一種新型的高能、快速、精確的焊接工藝,在汽車工業(yè)中的應(yīng)用越來越廣泛。結(jié)合激光焊接與先進(jìn)高強(qiáng)鋼以滿足汽車對(duì)輕量化與安全性的要求已經(jīng)引起了許多廠家和研究機(jī)構(gòu)的興趣。本文采用光纖激光器對(duì)超高強(qiáng)度鋼22Mn B5進(jìn)行搭接和對(duì)接深熔焊的研究。另外,22Mn B5鋼分別與車用雙相高強(qiáng)鋼DP980、DP590和傳統(tǒng)高強(qiáng)鋼Q235進(jìn)行了激光拼焊試驗(yàn)。焊后研究了焊接接頭接頭微觀組織形貌和硬度、拉伸、疲勞等性能特點(diǎn)。22Mn B5鋼激光搭接研究表明,接頭寬度隨著焊接速度的增加而減小,當(dāng)焊接速度增加到一定值時(shí),搭接鋼板未能焊透。焊縫微觀組織主要為板條馬氏體,硬度值比母材稍高,熱影響區(qū)發(fā)生了明顯的軟化現(xiàn)象。接頭剪切強(qiáng)度隨著焊接速度的增加而減小,在焊接速度為1.5m/min時(shí)具有最大值。斷口表面的微觀形貌主要為韌窩,這說明斷裂過程是以微孔聚集的形式進(jìn)行的,但從宏觀來看其斷裂方式依然很“脆”。22Mn B5鋼激光對(duì)接焊研究表明,焊縫及其鄰近的熱影響區(qū)組織仍然為板條馬氏體,接頭硬度的分布情況與搭接焊基本一致,熱影響區(qū)有明顯的軟化現(xiàn)象。其熱影響區(qū)可以分成:淬火區(qū)、不完全淬火區(qū)和回火區(qū)。在回火區(qū),馬氏體由于回火轉(zhuǎn)變?yōu)榛鼗瘃R氏體。當(dāng)焊接速度增加時(shí),焊縫組織變得更細(xì)小,馬氏體含量增多,回火區(qū)的寬度變窄,焊接接頭硬度升高。在垂直于焊縫的負(fù)載下,3-5m/min焊接速度的22Mn B5拉伸試樣均斷在熱影響區(qū),塑性較差,斷后延伸率僅為2%左右。斷口表面的微觀形貌為韌窩和解理小平面,還有一些撕裂棱清晰可見,呈現(xiàn)明顯的準(zhǔn)解理斷裂特征。22Mn B5鋼的激光拼焊研究表明,異種鋼焊接接頭的成形良好,無裂紋氣孔等缺陷產(chǎn)生。焊接接頭最大硬度依然在焊縫,然而焊縫卻呈現(xiàn)由低到高增長的兩部分,在雙相鋼和Q235一側(cè)焊縫的硬度明顯低于22Mn B5一側(cè)焊縫的硬度。雙相鋼熱影響區(qū)與22Mn B5一樣存在軟化區(qū),且隨著鋼材等級(jí)的增加,軟化區(qū)區(qū)的軟化程度也相應(yīng)增加,由于Q235鋼板母材為正火態(tài),所以該鋼熱影響區(qū)不存在軟化區(qū)。22Mn B5-22Mn B5、22Mn B5-DP980的拉伸試驗(yàn)均斷在熱影響區(qū),而22Mn B5-DP590、22Mn B5-Q235均斷在低強(qiáng)度鋼板的母材。在相同試驗(yàn)參數(shù)下,22Mn B5母材擁有最高疲勞壽命,22Mn B5-22Mn B5疲勞試樣依然斷在熱影響區(qū),而22Mn B5-DP980的疲勞試樣均斷在DP980的母材。典型的疲勞斷口分為三部分:裂紋萌生區(qū),裂紋擴(kuò)展區(qū),瞬斷區(qū)。萌生區(qū)往往出現(xiàn)在試樣表面,而擴(kuò)展區(qū)會(huì)出現(xiàn)疲勞條帶和二次裂紋,瞬斷區(qū)與拉伸斷口很相似。
[Abstract]:Energy saving, environmental protection, safety is the three major themes in today's automobile manufacturing industry, and the automotive lightweight is the major car companies realize low fuel consumption, one of the main measures to reduce the exhaust emissions. The advanced ultra high strength steel with high tensile strength, high energy absorption rate and after the collision is not easy to deform and other advantages, the rapid development of become important automotive lightweight materials. At present, the laser welding technology as a new type of high energy, fast, precise welding process, the application in the auto industry is more and more widely in. Combined with laser welding and advanced high strength steel to meet the requirements of automotive lightweight and safety has attracted many manufacturers and research institutions of interest. Study on fiber laser lap and butt welding of ultra high strength steel 22Mn B5 in this paper. In addition, 22Mn and B5 steel respectively car with dual phase high strength steel DP980 were studied by DP590 and conventional high strength steel Q235 Laser welding after welding on the tensile test. The microstructure and hardness of joints, welded joints, fatigue properties of.22Mn steel laser lap B5 research shows that the joint width decreases with the increase of welding speed, when the welding speed increases to a certain value, the plate can not lap welding. The microstructure of the weld is mainly lath martensite, hardness is slightly higher than the parent material, has an obvious softening of heat affected zone. The shear strength of joint decreases with the increase of welding speed, the maximum value in the welding speed is 1.5m/min. The micro morphology of the fracture surface is mainly dimple, it indicated that the rupture process is carried out in the form of microporous gathering from a macro point of view, but the fracture is still "brittle".22Mn B5 steel butt laser welding research shows that the weld heat affected zone and its adjacent tissue is lath martensite, hardness distribution of joint Consistent with the overlap welding heat affected zone has obvious softening phenomenon. The heat affected zone can be divided into: quenching zone, incomplete quenched zone and tempering zone. In the tempering zone, the martensite tempering is tempering martensite. When the welding speed increases, the weld microstructure become finer, more martensite content. Tempering zone width of welded joints, hardness increased. In the direction perpendicular to the weld load, 22Mn B5 specimens of 3-5m/min welding speed were broken in the heat affected zone, poor plasticity, the elongation is only about 2%. The morphology of the fracture surface dimple and cleavage planes, and some clear tear ridge therefore, the laser show quasi cleavage fracture characteristics of.22Mn steel B5 was welded research shows that the forming of dissimilar weld joints, no crack defects such as pores. The maximum hardness of welded joints in the weld seam is still, however, presented by Low to high growth in the two part, one side of the Q235 dual phase steel and the hardness of the weld was significantly lower than that of 22Mn B5 on one side of the hardness of the weld. Dual phase steel heat affected zone and 22Mn B5 as the softening zone, and with the increase of steel grade, softening also increased softening degree only, because of the Q235 steel base metal for normalizing state, so the steel heat affected zone does not exist.22Mn B5-22Mn B5,22Mn tensile softening zone B5-DP980 were broken in the heat affected zone, and the 22Mn B5-DP590,22Mn B5-Q235 parent material are broken in low strength steel. Under the same experimental conditions, 22Mn B5 parent material has the highest fatigue life, 22Mn B5-22Mn B5 is still broken in thermal fatigue specimen the affected area, and fatigue specimens of 22Mn B5-DP980 were broken in base metal DP980. Typical fatigue fracture is divided into three parts: crack initiation, crack propagation and fracture zone. The initiation region often appear in the surface of the sample, and the exhibition will be expanded The fatigue strip and two cracks are present, and the instantaneous fracture zone is similar to the tensile fracture.

【學(xué)位授予單位】：上海工程技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG456.7

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