In Situ Observation of Phase Transformations during Welding of Low Transformation Temperature Filler Material
In Situ Observation of Phase Transformations during Welding of Low Transformation Temperature Filler Material
复制标题
低相变温度填充材料焊接过程中相变的原位观察
DOI：
10.4028/www.scientific.net/msf.638-642.3769
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
J. Gibmeier
中科院分区：
文献类型：
--
作者：
A. Kromm;T. Kannengiesser;J. Gibmeier
传统焊接工艺引入的拉伸残余应力降低了焊接部件的抗裂性和疲劳寿命。为了在焊接部件的表面产生有益的压缩残余应力，可以使用各种焊后处理程序，如喷丸、锤击等。然而，这些焊后处理时间和成本很长。一种有吸引力的替代方案是在焊接过程中通过所谓的低转变温度（LTT）填充材料在整个焊接接头上产生压应力。相变引起的体积变化影响焊缝及其附近的残余应力。LTT填料表现出相对低的转变温度和正体积变化，导致焊接区域中的压缩残余应力。首次成功地实现了钨极气体保护焊（GTA）过程中真实的焊接实验中衍射轮廓的原位测量。在加热和随后的冷却过程中的LTT焊接材料的相变温度可以通过使用高能同步辐射的能量色散衍射来评估。结果表明，马氏体起始温度（Ms）与合金元素含量密切相关。此外，结果表明，不同的相变温度存在取决于焊接深度。残余应力的额外测定使其能够将时间和温度分辨的相变和所产生的相特异性残余应力拉在一起。结果表明，对于LTT焊缝的残余应力状态的评估，在详细描述相应材料的全局应力条件时，必须考虑共存的马氏体和奥氏体相。
Tensile residual stresses introduced by conventional welding processes diminish the crack resistance and the fatigue lifetime of welded components. In order to generate beneficial compressive residual stresses at the surface of a welded component, various post-weld treatment procedures are available, like shot peening, hammering, etc. These post-weld treatments are, however time and cost extensive. An attractive alternative is to generate compressive stresses over the complete weld joint in the course of the welding procedure by means of so-called Low Transformation Temperature (LTT) filler materials. The volume change induced by the transformation affects the residual stresses in the weld and its vicinity. LTT fillers exhibit a relatively low transformation temperature and a positive volume change, resulting in compressive residual stresses in the weld area. In-situ measurements of diffraction profiles during real welding experiments using Gas Tungsten Arc (GTA)-welding process were realized successfully for the first time. Transformation temperatures during heating and subsequent cooling of LTT welding material could be assessed by means of energy dispersive diffraction using high energy synchrotron radiation. The results show that the temperature of martensite start (Ms) is strongly dependent on the content of alloying elements. In addition the results indicate that different phase transformation temperatures are present depending on the welding depth. Additional determination of residual stresses allowed it to pull together time and temperature resolved phase transformations and the resulting phase specific residual stresses. It was shown, that for the evaluation of the residual stress state of LTT welds the coexisting martensitic and austenitic phases have to be taken into account when describing the global stress condition of the respective material in detail.