TC4钛合金等离子弧焊接工艺及组织性能

发布时间：2018-06-23 12:32

本文选题：TC4钛合金 + 焊接工艺　；参考：《内蒙古工业大学》2017年硕士论文

【摘要】：TC4钛合金作为一种典型的α+β双相钛合金,由于其具有良好的强度、塑性、耐腐蚀性等,被广泛的用于制造高性能飞机的机身以及各种的承力构件,在一些大型的机构中如压力容器、发动机、发动机支架等部件,钛合金的用量也急剧上涨,并且在军工方面的用量也不断提高。据统计发现钛合金在航天航空领域的实际使用量已经高达80%以上,并且在一些关键的部位都采用了TC4钛合金焊接结构。随着其在各个领域的应用不断提高,TC4钛合金的焊接方法也日趋成熟。已有研究表明在使用高能束焊接时TC4钛合金均能获得性能较好的焊接接头,但针对TC4钛合金等离子弧焊的研究则相对较少。本文采用等离子弧焊对3mm厚TC4钛合金进行焊接。分别以焊接接头抗拉强度以及弯曲强度为评价指标,通过响应曲面法确定较优焊接参数,确定各焊接参数对评价指标的影响程度顺序,并对较优参数下获得的焊接接头的组织性能进行分析。通过观察TC4钛合金自熔焊以及对焊的焊缝成形情况,确定了响应曲面的参数范围。通过响应曲面分析得到较优参数:当焊接速度为14mm·s~(-1)、焊接电流为160A、离子气流量为3L·min~(-1)时,TC4钛合金等离子弧焊焊接接头抗拉强度为1080MPa;当焊接速度为14.4mm·s~(-1)、离子气流量为3.8 L·min~(-1)、焊接电流为161A时,TC4钛合金等离子弧焊焊接接头弯曲强度为1426MPa。通过响应曲面分析方法分别确定出拟合程度较好回归方程H_1和H_2,发现在较优参数下获得的TC4钛合金等离子弧焊焊接接头抗拉强度的实测值与预测值相当,焊接接头弯曲强度的实测值与预测值误差仅为2.983%。其中,回归方程H1中的一次项中C_1(焊接速度)、C_3(焊接电流)是差异显著,二次项C_3~2(焊接电流2)是极差异显著,在交互项中C_1C_2(焊接速度·离子气流量)也是极差异显著的。回归方程H_2的一次项中C_1(焊接速度)、C_2(离子气流量)、C_3(焊接电流)都是极差异显著,二次项C_22(离子气流量2)是极差异显著,在交互项中C_1C_3(焊接速度·焊接电流)是极差异显著的。显著性分析后可知一次项中焊接速度为显著性较高的焊接参数,因此以焊接速度为单一变量对焊接接头组织性能分析发现:当焊接电流为160A、离子气流量为3L·min~(-1)、焊接速度范围为14mm·s~(-1)~16mm·s~(-1)时,焊接接头性能较为理想;焊缝中心显微组织由“网蓝状”分布的α′相组成,临近焊缝中心处热影响区的显微组织是由原始的α相与针状α′相构成,临近母材热影响区的显微组织由原始α相、原始β相与针状α′相构成。
[Abstract]:As a typical 伪尾 dual phase titanium alloy, TC4 titanium alloy is widely used in the manufacture of high performance aircraft fuselage and various load-bearing components because of its good strength, plasticity, corrosion resistance and so on. In some large organizations, such as pressure vessels, engine support and other components, the amount of titanium alloy also increased sharply, and the amount of military industry is also increasing. According to statistics, it is found that the actual usage of titanium alloy in aerospace field has reached more than 80%, and TC4 titanium alloy welding structure has been adopted in some key parts. With its application in various fields, the welding method of TC4 titanium alloy is becoming more and more mature. It has been shown that TC4 titanium alloy can be welded with better performance when high energy beam welding is used, but the research on plasma arc welding of TC4 titanium alloy is relatively rare. In this paper, 3mm thick TC4 titanium alloy is welded by plasma arc welding. Taking the tensile strength and bending strength of welded joints as evaluation indexes, the optimal welding parameters are determined by response surface method, and the order of influence of each welding parameter on the evaluation index is determined. The microstructure and properties of welded joints obtained under optimum parameters were analyzed. The parameter range of the response surface was determined by observing the weld formation of TC4 titanium alloy in self-fusion welding and butt welding. The optimum parameters are obtained by response surface analysis: when the welding speed is 14mm s-1, the welding current is 160 A, the ion flow rate is 3 L min ~ (-1), the tensile strength of plasma arc welding joint of TC4 titanium alloy is 1080 MPA, the welding speed is 14.4mm s ~ (-1), the ion gas flow rate is 3.8 L min ~ (-1). When the welding current is 161A, the bending strength of plasma arc welding joint of TC4 titanium alloy is 1426MPa. According to the response surface analysis method, the regression equations H _ (1) and H _ (2) of fitting degree are determined respectively. It is found that the tensile strength of plasma arc welding joint of TC4 titanium alloy obtained under the better parameters is equal to the predicted value. The error between the measured and predicted bending strength of welded joints is only 2.983. Among them, there are significant differences in the first term of regression equation H1 (welding speed) and C _ S _ 3 (welding current), the second term C _ 3O _ 2 (welding current 2) is extremely different, and in the interactive term C _ 1C _ S _ 2 (welding velocity ion gas flow) is also very different. In the first term of the regression equation H2, there is a very significant difference between C _ 1 (welding speed) and C _ S _ 2 (ion gas flow) and C _ (3) (welding current) for C _ (1) C _ (2), and for C _ (1) C _ (2) (welding current), there is a significant difference between C _ (1) C _ (2) and C _ (1) C _ (3) (welding current) in the interaction. After significant analysis, it was found that the welding speed of one item was higher than that of other welding parameters. It is found that when welding current is 160 A, ion flow rate is 3 L min ~ (-1), and welding speed range is 14mm s ~ (-1) ~ (16 mm s ~ (-1), the welded joint properties are better. The microstructure in the center of the weld is composed of 伪 'phase of "net blue" distribution, the microstructure of the heat-affected zone near the center of the weld is composed of the original 伪 phase and the needle-like 伪' phase, and the microstructure near the heat-affected zone of the base metal is composed of the original 伪 phase. The original 尾 phase is composed of acicular 伪 'phase.
【学位授予单位】：内蒙古工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.19

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