【作者】 张平；

【导师】 刘仁培；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2008， 硕士

【摘要】 药芯焊丝是近几年来发展最快、最有吸引力的新型焊接材料。为改善和提高碱性渣系药芯焊丝的焊接工艺性能,本文对己有的普通碱性渣系进行了改进,研制了一种碱性MgO-氟化物-SiO₂-TiO₂渣系的混合气体保护药芯焊丝。围绕渣系组分对药芯焊丝熔滴过渡行为、焊接电弧稳定性、熔渣覆盖及脱渣性等方面的影响进行了系统的研究和探讨。通过高速摄影观察熔滴过渡过程、水中收集熔滴和焊接飞溅测试等方法,研究了渣系组分对焊丝熔滴过渡行为以及焊接飞溅的影响。结果表明:当MgO含量小于25%时,熔滴颗粒相对细小,沿着焊丝轴向平稳过渡,焊接飞溅较小。用一部分氟硅酸钠代替萤石时,可以细化熔滴,降低飞溅。但是氟硅酸钠的含量超过12%以上时,又会使得焊接飞溅增大。通过与焊机相匹配的Lookout Weldoffice2000软件同步测试焊接过程的电弧电压和焊接电流数据,生成电弧电压、焊接电流波形图;同时结合高速摄影观察电弧的形态,研究了渣系组分对焊接电弧稳定性的影响。结果表明:当MgO为22%左右,CaF2为6%、Na2SiF6为9%时,焊接电弧稳定性较好。通过熔渣覆盖性评定及落球脱渣性试验研究了渣系组分对渣覆盖及脱渣性的影响,并建立了脱渣率的数学模型。结果表明:当MgO含量22%²5%左右,SiO₂含量5%⁷%左右,氟化物含量15%左右,TiO₂含量13%¹5%左右时,焊缝熔渣覆盖良好,脱渣性好。此外,分析了熔渣微观组织结构、内表面形貌和断口特征对焊缝脱渣性的影响。结果表明:当熔渣的组织粗大,第二相为方向性较强的条带状,熔渣结构密实时,脱渣性较好;反之,脱渣性较差。最后,本文得出了具有较好焊接工艺性能的药芯焊丝渣系主要成分配比为:MgO（22%²5%）-CaF₂+Na₂SiF₆（15%）-SiO₂（5%⁷%）-TiO₂（15%）。更多还原

【Abstract】 Flux cored wires are the most attractive new welding materials with the fastest developing speed in recent years. In order to improve the welding operation performance of basic flux cored wire, the paper has modified the present slag system and developed a new slag system for mixture gas-shielded flux cored wire, i.e. MgO-fluoride-SiO₂-TiO₂ slag system. The paper has carried on systematic research and discussion around slag system composition influences on droplet transfer formations, welding arc stability, slag covering ability and detachability of the flux cored wire.The effects of slag system composition on droplet transfer formations of flux cored wire and welding spatter were investigated by high-speed photography, by collecting droplets in a water through and test of spatter. The results showed that when MgO was less than 25%, the droplet transfer was steady with relatively small molten droplets and welding spatter was smaller too. Replacing a part of CaF2 with Na2SiF6 could reduce welding spatter with thinning molten drops. But when the Na2SiF6 was more than 12%, it would increase the welding spatter.The arc voltage and welding current was recorded synchronous with the software Lookout Weldoffice2000 which matched with the welding machine, and then the arc voltage and welding electric current oscillogram were produced according these data. At the same time, the electric arc shape could be observed through the high-speed photography. The effects of slag system composition on welding arc stability of the flux cored wire were therefore studied. The results showed that when MgO was about 22%, CaF2 was 6% and Na2SiF6 was 9%, the welding arc stability was well.The paper has investigated the slag system composition influences on slag covering ability and slag detachability by slag covering ability evaluating and slag detachability testing, and established slag detachability mathematical model. The results showed that when the contents of MgO was 22%²5%, SiO₂ was5%⁷%, fluoride was about 15% and TiO₂ was 13%¹5%, the slag was covered well and it was easy to take off. In addition, the paper has analyzed the microstructures of slag, the inner surface structure of slag and the characteristic of slag fracture. The results showed that it was benefit for the slag detachability when the microstructure of slag was coarse, the second phase of microstructure presented strip-shaped distribution, and the slag structure was compact, and, contrariwise, the slag detachability became worse.Finally, the paper has acquired the slag system composition for the flux cored wire with favorable welding operation performance, i.e. MgO was 22%²5%, CaF₂ and Na₂SiF₆ were15%, SiO₂ was 5%⁷% and TiO₂ was about 15%.更多还原