【作者】 曾如川；

【导师】 何景山；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2006， 硕士

【摘要】 本文主要研究了LF2铝合金与Q235钢之间异种金属电子束焊接工艺。试验中引入偏束焊技术以解决异种金属连接时两侧母材热输入不均以及焊缝表面成形的问题,并研究了通过在接头处添加Cu以解决焊缝区大量Fe-Al脆性金属间化合物生成的问题。通过光学显微镜和扫描电镜等测试方法分析了焊接接头的组织结构和断口,揭示了接头形成过程。8mm厚LF6铝镁合金电子束焊接性试验研究结果表明,在焊接电压55kV,聚焦电流2595mA,采用电子束流为31mA,焊接速度为840mm/min时,可以得到355MPa的最高抗拉强度,为母材强度的95%以上。对焊接接头进行了微观组织分析以及断口分析,发现焊缝区组织均匀致密且无明显的气孔、夹杂等缺陷,并证实都属于韧性断裂。LF2-Q235的电子束焊接研究结果表明,焊接时熔池分为两部分:主熔池和辅助熔池。得到的焊缝区分为三个部分:焊缝A区、焊缝B区和焊缝C区。通过分析确定了焊缝各个区域中在焊接时可能发生的反应以及最后所得到的产物,发现C区存在着大量呈层带状分布的脆性金属间化合物,为接头强度薄弱区。经断口分析发现断裂发生在焊缝C区的位置,断口表面主要存在着Fe3Al和Al2Cu这两种金属间化合物,它们的存在是引起脆性断裂发生的主要原因。在组织结构分析的基础上建立了LF2-Q235异种金属电子束对接接头形成的物理模型,分析了接头形成的具体过程。更多还原

【Abstract】 The dissimilar metals joining between aluminum alloy LF2 and Q235 steel with electron beam welding (EBW) was investigated. Deflection electron beam welding was brought out to improve the heat input of both side dissimilar metals and the appearance of weld surface. Cu was added into the joint to prevent the intermetallic compound Fe-Al from generating. The structure of the joints and the appearance of fracture were studied with OM and SEM. The growing of joint was studied.The weld performance of aluminum alloy LF6 with 8 mm width was studied in experiment. The optimum processing parameters were determined as“U: 55kV, If: 2595mA, Ib: 31mA, v: 840mm/min”. The tensile strength of the joint was 355 MPa, which was more than 95% of base metal. The microstructure of joint was analyzed. It’s found that the structure of weld bead was very homogeneous. Neither hole nor flaw was found in joint.The gliding fracture was approved by analyzing the appearance of fracture.The result of EBW of LF2-Q235 showed that the molten pool was composed of two parts: main pool and assistant pool. The joint zone was composed of three parts: zone A, zone B and zone C. The reaction and product in each zone was determined by energy spectrum analysis. It’s found that much intermetallic compound which was very brittle and layered distributed in zone C, which showed much weaker than other zones in joint. Fracture was found to happen in zone C through fracture appearance analysis. Intermetallic compound Fe3Al and Al2Cu were present on the fracture surface which were the main responsibility to brittle fracture. Based on the analysis of the structure of joint, the physical model on the formation of dissimilar metals joint between aluminum alloy LF2 and Q235 steel with EBW was built. The process of the formation of the joint was analyzed.更多还原