【作者】 苏允海；

【导师】 刘政军；

【作者基本信息】 沈阳工业大学 ， 材料加工工程， 2006， 硕士

【摘要】 由于环保和节能的要求镁合金成为新材料的代表广受社会的关注,本文研究了镁合金在双逆变脉冲磁场作用下的TIG焊。首先进行无磁场的TIG焊,选用的材质是AZ31和AM50,调节焊接工艺参数进行大量焊接实验,对得到的焊接接头进行性能和显微组织对比分析,研究不同工艺参数对焊接接头性能的影响规律,从而确定一套最佳的焊接工艺参数。最终确定工艺参数范围为焊接电流80-100A,气流量6-9L/min,焊接速度6-8mm/s。由于镁合金物理性能和自身的冶金特点,决定镁合金的焊接性较差,焊接时容易产生变形、烧穿、热裂纹和气孔,其中最主要的是热裂纹和气孔。本文系统的研究了焊接热裂纹产生的机理及防止措施。其中热裂纹是由于熔池金属在凝固过程中出现了低熔点共晶物β—Al₁₂Mg₁₇,大量低熔点共晶物聚集于晶界在应力的作用下发生滑移开裂,最终形成了热裂纹,热裂纹的产生可以通过控制热输入进行有效的抑止。焊缝中的气孔经过分析发现一部分是溶入性气孔,一部分是反应气体,其中气孔的大部分是氢气孔。通过对焊接材料焊前的除油、除杂、烘干等处理可以有效的切断氢来源同时严格控制氩气流量可以防止气孔的产生。 外加双逆变脉冲作用下镁合金的焊接是在前期实验得到的工艺参数基础上进行的。焊接选用的材质为AZ31。焊接过程中调节磁场电流,固定磁场频率,对焊接接头进行性能和显微组织对比分析,发现外加纵向磁场使镁合金TIG焊焊接接头性能明显提高,焊接接头的力学性能达到母材的85%以上,减少焊接接头软化程度,同时外加纵向磁场可以有效的抑止焊接热裂纹的产生,净化组织,减少夹杂、气孔等缺陷。同时本试验从理论上对外加纵向双逆变脉冲磁场对镁合金TIG焊的影响进行了初步研究。更多还原

【Abstract】 For the requiement of environment profection and power saving, magnesium alloys have drawn extensive attention as a representative of new materials. In this paper, the TIG welding of magnesium under the double inversion pulse magnetic field was investigated. First, the TIG welding of magnesium without magnetic field was studied, AZ31 and AM50 were selected as the testing materials. After experiments with different processing parameters and comparative analysis on the performances and microstructure of the welding joint, the effecting laws of different processing parameters on the performances of welding joint were found, and then a suit of favorable technology parameters was made out. The range of final optium processing parameters are such as: the welding current 80-100A, gas feed rate 6-9 L/min, speed of welding6-8 mm/s. During the experiments with different processing parameters, some welding deficiencies were found, the chief ones of them are hot cracking and gas cavity. The forming mechanics and prevention means is discussed in the paper. The forming mechanics of hot cracking is the appearance of β— Al₁₂Mg₁₇, which has low melting point. By controlling the heat input can suppress the appearance of hot cracking. The appearance of gas cavity is because of the magnesium can react with lots of gas which are included in air. After the action, lots of gas can not effuse and stay in welding joint. Through treating before welding and properly protecting during welding can reduce the gas cavities.On the bases of f（?） processing p（?）, the wekling of AZ3（?） （?） （?）loy under double inversion pulse magnetic field was proceeded. During the experiments, the magnetic frequency was fixed and the magnetic current was variable, comparative analysis on the performances and microstructure of the welding joint was proceeded, which were welded in the different processing parameters. Through comparing analyses, found that the properties of weld joint under the magnetic field was obvious improved, and reach 85% of matrix. At thesame time, the input of magnetic field can suppress the appearance of hot cracking and pure the organize, reduce foreign substance. At the last, the influence mechanics of magnetic field on the magnesium alloys TIG welding was discussed.更多还原