【作者】 李帅伦；

【导师】 马跃进；

【作者基本信息】 河北农业大学 ， 农业机械化工程， 2008， 硕士

【摘要】 焊接作为制造业的基础工艺与技术,在21世纪为工业经济的发展做出了重要的贡献。然而,焊接是一个局部快速加热和冷却的过程,它所引起的不均匀温度场和应变场,在被焊工件内会产生较大的焊接应力,而焊接应力的存在可以导致产生热裂纹及冷裂纹并且还会影响到焊件加工精度和尺寸稳定性,影响了焊接质量。如何降低和消除焊接应力,防止焊接裂纹的产生成为焊接领域广泛关注的一个重要课题。人们提出了热处理法、振动法、机械拉伸法、锤击法等多种消除焊接应力的方法,作为锤击法,随焊锤击是在焊接过程中通过实时锤击焊缝及近缝区金属材料从而消除或减小焊接应力的一种焊接新技术。该方法能有效的改善焊接接头的应力分布状态,降低应力集中现象,防止焊接热裂纹的出现,提高焊件的抗拉强度。与其它消应力的方法相比,随焊锤击具有操作简单,效率高等特点,显示了一定的优越性。为了更好的完善随焊锤击工艺,实现随焊锤击装置的自动化。在前期研究的基础之上,本文继续对随焊锤击设备及工艺进行了研究。首先,分析了随焊锤击强化焊缝的原理,对随焊锤击装置进行了简单阐述。对电磁锤进行了改进,减小了其体积,增加了灵活性。其次,通过改进后的电磁锤设计出了三个自由度的夹具,使电磁锤能自由的调整锤头与堆焊焊头的角度(即锤击温度)及锤击距离。用自行设计的夹具带动随焊锤击装置进行随焊锤击试验,通过试验着重分析了不同的锤击力和锤击温度对焊接应力和显微硬度的影响,并对锤击前后试件的显微组织进行了对比分析。最后,利用数值模拟技术对焊接温度场和应力场进行了分析讨论。通过随焊锤击试验可以得出如下结论:(1)随焊锤击可以使焊缝及其附近的焊接应力得到不同程度的降低,在焊缝处应力降低的幅值最大,距离焊缝越远,应力降低的幅值越小;(2)从焊缝的金相组织可以看出:随焊锤击处理可以细化晶粒,增加焊缝的强度;(3)基于ANSYS有限元,采用埋弧堆焊技术对焊接温度场和应力场进行了模拟,得出在焊接热影响区和距焊缝中心线不同位置处的热循环曲线变化趋势一致,温度都是先迅速升高再下降,随着时间的推移趋于稳定。纵、横残余应力沿焊缝中心线上变化趋势一致,但纵向应力整体表现为拉应力,总体来说纵向应力比横向应力大的多。更多还原

【Abstract】 The welding as a basic craft and technique of manufacturing has made important contribution for the development of the industrial economy in the 21st century. However, welding is a process of fast heating and cooling in part, which causes the non-uniform temperature field and strain field that produce big welding stress in the welded workpiece. But the existence of welding stress may produce the heating crack, cooling crack and also affect the processing precision and size stability, and affect the welding quality.How to reduce and eliminate welding stress, and avoid welding crack form becomes an important topic in welding field draws much attentions. People proposes many methods of eliminating welding stress, including the heat treatment, the vibration method, the machine stretch method, peening method and so on. As peening method, welding with trailing peening is new technique of reducing or eliminating welding stress through real-time peening the welding joint and the near metal in the welding process. Which can effectively improve the stress distribution condition in the welding joint, reduce the stress concentration phenomenon, prevent the welding heating crack and enhance the anti-tensile strength. Comparing with other reducing stress methods, welding with trailing peening has merit of simple operation, high efficiency, and more advantages are being displayed.In order to perfect welding with trailing peening craft, and realize automatization of welding with trailing peening device. The subject is base on predecessor’s research foundation go to study equipment and technics of welding with trailing peening. Firstly, analysed the strengthen principle of welding with trailing peening, and simple expound the welding with trailing peening device. Electromagnetic hammer had been improved, reducing its cubage and enhancing its flexibility. Secondly, through improved the electromagnetic hammer designed its fixture have 3 Degree-of-freedom, and free adjust hammer head with surfacing weld’s angle (peening temperature) and peening distance. Fixture which independently designs to drive device carry through welding with trailing peening experiment, through the welding with trailing peening experiment emphasize analyzed the influence of peening. Force peening temperature on welding stress and microhardness, the microstructure of peening before and after workpieces were contrasted and analysed. Finally, the paper discussed the welding temperature field and stress field by using numerical simulation technique.Drawing the below conclusion through the experiment: (1) The welding stress was reduced in the welding joint and the near area remaining, the peak of reducing value is in the welding seam, more far from welding seam, more small of reducing value of stress. (2) From the welding joint microstmcture: welding with trailing peening can thin crystal grain, increases intensity of the welding joint. (3) Based on ansys finite element, adopted submerged arc surfacing welding techniques to simulate welding temperature and stress field, then concluded that thermal circling curves changed in the trend line at welding heat affected zone and along centerline of the welding joint in different sections. temperature generally increase rapidly and then fell until to become stable; longitudinal, transverse residual stress changed in the trend line along centerline of the welding join, but the whole longitudinal stress represented tension stress, as a whole, longitudinal stress is much bigger than transverse stress.更多还原