【作者】 马琳；

【导师】 闫久春；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2009， 硕士

【摘要】 本文主要研究了紫铜厚板不预热GTAW防止热裂纹产生机理及He气保护焊接工艺。首先对比了氩气、氦气和氮气作为保护气,焊接裂纹及氮气孔的形成规律。其次分析研究了Ti元素防止裂纹及氮气孔的机理。进行一系列的氦气体保护焊接工艺试验,并对焊接接头的微观结构、焊缝成分和力学性能进行对比分析。试验结果表明,填加Hs201焊丝,在氩气保护时,预热温度为300℃、500℃和700℃时焊接接头都会产生热裂纹,随预热温度的升高热裂纹逐渐减少。在氦气保护时,预热300℃时焊缝中只有液化裂纹,不预热时焊缝中除液化裂纹外还存在结晶裂纹。采用氮气保护焊接紫铜时,焊缝中不仅会产生结晶裂纹还有大量的氮气孔存在。采用氮气/氩气保护GTAW接紫铜厚板,填加钛含量为4%和5%的Cu-Ti合金焊丝时,均不会产生气孔和裂纹。含钛量为4%的焊缝基体为固熔1.5%左右Ti的Cu,深色析出相为Cu-Ti和Ti-Si金属间化合物,浅色析出相主要为TiCuSn+CuTiSn3+Cu3Sn金属间化合物。含钛量5%焊缝基体为固溶3%左右Ti的Cu;深色析出相主要为Ti-Si及Ti-Cu金属间化合物。浅色析出相A主要为CuTi5Sn3+Cu3Sn+Cu。Ti能够防止焊接接头中产生热裂纹的原因主要为:Cu-Ti合金焊丝中的Ti与O反应生成稳定的产物TiO2以焊渣的形式浮出焊缝表面。从Ti具有较强脱氧能力以及Cu-Ti合金具有较强抗变形能力两方面证明了这一原因。Ti能够防止在氮气保护GTAW时焊缝中产生的大量氮气孔的原因是:Ti在高温时具有很强的吸氮性,与进入焊缝中的N反应生成稳定且密度小的产物TiN以焊渣的形式浮出焊缝表面。采用氦气保护GTAW焊接紫铜厚板,填加含钛量降至3%的铜钛合金焊丝,焊缝中无热裂纹,接头成型好,硬度低,强度高。焊缝金属组织形貌与Cu-Ti焊丝基本相同,焊缝基体主要为Cu中固溶了2%-3%的Ti,焊缝中均匀分布着深色和浅色两种析出相,浅色析出相为CuTi3Sn3+Cu3Sn+Cu的三元金属间化合物。深色析出相为Ti-Si和Ti-Cu金属间化合物。焊接接头的拉伸强度接近母材。但焊接接头的冲击韧性较差。更多还原

【Abstract】 Researching on mechanism of avoiding cracks and process of thick plate of copper without preheating shielding GTAW welds was invesGTAWated in this paper. The law of formation of the weld cracks and nitrogen porosity of argon, helium and nitrogen shielding GTAW was contrasted. Secondly analyzed copper and titanium alloy wire how to eliminate the crack and nitrogen porosity. Experiments of helium gas shielding GTAW welding of copper were done. And the microstructure of joints, the welding components and the mechanical properties were analyzed.The results showed that to add Hs201 welding stick, of the protection of argon, the temperature of preheating is 300℃、500℃and 700℃, all the welded splice will produce the heat check, on the 700℃it will be less welded crack. Of the protection of helium, the temperature of preheating is 300℃, there is only liquefy crack in the welded crack, when not preheating, besides the liquefy crack, there is also ystal crack. When use nitrogen to protect the welded red copper, not only can produce ystal crack, but also lots of nitrogen in the welded crack.Using nitrogen/argon to protect GTAW welding plate making, adding the welding stick of copper and titanium alloy on the quality proportion of copper and titanium is 4% and 5%, the porosity and crackle will be avoided. The 4% welded matrix is mainly 2-3% Ti which is solved in the Cu, the light precipitation phase and the deep color precipitation phase uniformly distributes in the weld seam. The light precipitation maybe is intermetallic compound of TiCuSn+CuTiSn3+Cu3S. the deep color precipitation phase is high-heat intermetallic compound of Ti-Si and Ti-Cu. 5% welded matrix is mainly 3% Ti solved in the Cu, The light precipitation phase and the deep color precipitation phase uniformly distributes in the weld seam. The light precipitation maybe is intermetallic compound of CuTi5Sn3+Cu3Sn+Cu. The deep color precipitation phase is high-heat intermetallic compound of Ti-Si and intermetallic compound of Ti-Cu.The main reason for that the copper and titanium alloy can avoid the crackle of the welded splice: analyzing from the thermodynamics, Ti in copper and titanium alloy has the strong deoxidizing capacity, it can snatch the oxygen from the Cu2O to produce the steady product TiO2 to head above the welded line. The reason of welding stick of copper and titanium can avoid the lots of nitrogen porosity produced in the welded line when the nitrogen protecting GTAW welding is: Ti has the strong ability of nitrogen uptake, it can be reacted with the nitrogen in the welding line to produce the steady and small density product TiN to head above the face of the welding line.Using helium to protect GTAW of welding thick plate of copper, and to add the copper and titanium alloy is over 3% alloy welding stick, it will be good forming in welding and has no defect in the welding line. Weld structure is almost the same as the copper and titanium welding stick. The welded matrix is mainly 2-3% Ti solved in the Cu, The light precipitation phase and the deep color precipitation phase uniformly distributes in the weld seam. The light precipitation maybe is intermetallic compound of CuTi3Sn3+Cu3Sn+Cu. The deep color precipitation phase is the high-heat intermetallic compound of Ti-Si and the intermetallic compound of Ti-Cu. The tensile strength of the welded joint was near to the base of metal. But the impact toughness of the welded splice is poor.更多还原