One possible option for increasing the fatigue strength of welded joints is the use of so-called low transformation temperature (LTT) alloys. The aim is to introduce residual compressive stresses into the weld to counteract crack initiation and propagation. Until now, there has been no application of an LTT effect to high-performance welding processes such as the laser beam submerged arc hybrid welding process (LUPuS hybrid). First, the LUPuS hybrid single-wire process was further developed into the LUPuS tandem hybrid process. This makes it possible to equip the two submerged arc welding torches with different commercially available filler wires. The aim of the work is to further develop the LUPuS tandem hybrid welding process to enable the use of the LTT effect. The in situ alloying process for obtaining the LTT effect from commercially available material combinations was extended to the two-wire process. The alloy obtained was investigated by means of energy dispersive x-ray spectroscopy and hardness measurements and the influence on residual stresses was determined by the borehole method supported by electronic speckle pattern interferometry.

中文翻译：

---

开发高性能焊接工艺的原位合金化方法，通过局部修改合金含量来实现 LTT 效果

提高焊接接头疲劳强度的一种可能选择是使用所谓的低转变温度 (LTT) 合金。目的是在焊缝中引入残余压应力，以抵消裂纹的萌生和扩展。到目前为止，LTT效应还没有应用于高性能焊接工艺，例如激光束埋弧复合焊接工艺（LUPuS混合）。首先，LUPUS混合单线工艺进一步发展为LUPuS串联混合工艺。这使得可以为两个埋弧焊枪配备不同的市售填充焊丝。这项工作的目的是进一步开发 LUPuS 串联混合焊接工艺，以实现 LTT 效应的利用。用于从市售材料组合中获得 LTT 效应的原位合金化工艺已扩展到两线工艺。通过能量色散 X 射线光谱和硬度测量对所得合金进行了研究，并通过电子散斑干涉测量法支持的钻孔方法确定了对残余应力的影响。