铝合金剪裁拼焊板激光焊接工艺研究

【作者】 王刚；

【导师】 樊丁；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2005， 硕士

【摘要】 剪裁拼焊板是将不同材质、不同厚度的板料经剪裁后,用激光焊接拼成各种坯板,然后整体冲压成形的一种新技术。剪裁拼焊钢板在汽车工业中的应用,取得了很大的经济效益,而铝合金激光剪裁拼焊技术尚未得到应用。铝合金的激光焊接存在不少技术难点,而铝合金薄板的激光对接拼焊比搭接更为困难,它不仅存在铝合金激光焊接的一般问题,而且由于激光束对接口间隙的大小非常敏感,又由于材料厚度和材质的不同,激光拼焊存在的问题更多,如焊缝成型困难、受热不均以及应力集中等。 本文主要研究铝合金5A02、5A06不等厚度薄板的激光拼焊工艺。在添粉和不添粉的情况下,进行了不等厚度的铝合金(5A02、5A06)薄板的激光拼焊,确定了添粉的铝合金5A02和5A06拼焊板的最佳工艺参数范围,得到性能合格的铝合金激光剪裁拼焊板。分析了各种因素(包括铝合金表面涂粉、激光器的输出功率、焊接的速度、离焦量等)对激光的吸收率、焊缝成型和焊接宏观质量的影响及规律。同时还进行了两种铝合金拼焊板激光焊接接头的性能测试(拉伸性能、硬度)。并利用SEM等手段观察了铝合金激光接头的金相组织和拉伸断口形貌。 实验结果表明,在激光焊接中,不添粉的铝合金5A02拼焊板的激光焊接过程不稳定,易产生焊穿和焊不透等焊接缺陷,而添粉的铝合金5A02拼焊板的激光焊接过程比较稳定,焊缝均匀、平整;而添粉对铝合金5A06薄板的焊接过程稳定性及焊缝的外观质量影响不明显。铝、镁混合粉能提高铝合金对激光的吸收率,在相同的焊接条件下,添粉的铝合金5A02和5A06拼焊板的熔宽比不添粉的熔宽大。添粉的铝合金5A02和5A06拼焊板焊缝的显微硬度要比不添粉的拼焊板的显微硬度高,这是因为粉中的镁元素补偿了焊接过程焊缝中镁元素的损耗。添粉和不添粉的5A02和5A06铝合金拼焊板的横向拉伸试件均断裂于薄板母材,证明焊缝的强度合格。通过扫描电镜观察,拼焊板激光接头拉伸断口均为韧性断口。更多还原

【Abstract】 Tailor-welded Blanks are comprised of two or more separate pieces of sheet mental with different materiel and different thickness that have been welded together previous to stamping. The use of Tailor-welded Steel Blanks in Automobile industry has gotten a great economic efficiency. But Tailor-welded Aluminum Blanks have still not been used in automobile. There are many difficulties in Laser welding of Aluminum Blanks. Laser welding of Tailor-welded Blanks with butt joint is more difficult than lap joint. Because the laser beam is very sensitive to the groove gap and the welding blanks have different materiel and different thickness, there are more problems in butt welding of Tailor-welded Blanks, such as difficulty of weld molding, odds in heated and stress centralization.In this thesis, laser welding of tailored blanks with different thickness of two kinds of materials (5A02 and 5A06) with metal powder and without metal powder were carried out. Influence factors on laser absorption geometry and quality of weldment (surface coating, type of aluminum alloys, power of laser apparatus, weld speed and defocused distance etc) were also analyzed. Meanwhile, the causes of porosity and cracking were described. As well as, mechanical properties (tensile strength and hardness)were test. Micro structural characteristics and fractography were observed by SEM.The result of test indicated that the metal powder of Mg and Al can improve absorbability of aluminum alloys. The width of aluminum 5A02 and 5A06 alloys welds with metal power was wider than that with not metal power, when using the same weld condition. The hardness of 5A02 and 5A06 welds with metal power was harder than that without metal power, because the magnesium of metal powder can amend the loss of magnesium. The longitudinal tension PM specimen of Tailor Welded Blanks of 5A02 and 5A06 were all fractured on the thinner base metal, which indicated that welds were eligibility. The fracture of the longitudinal tension PM specimen was toughness fracture.更多还原