提高焊接接头疲劳强度的低相变点焊条和超声冲击方法

由于焊趾部位存在有应力集中和残余拉伸应力,焊接接头的疲劳强度远低于基体金属,超声冲击和低相变点焊条的应用是近年来发展的提高焊接接头疲劳强度方法。通过对横向对接焊接接头和纵向角接板焊接接头试件的疲劳试验,在2×106循环次数下与普通E5015焊条焊态试件相比,超声冲击处理的两种型式接头的疲劳强度分别提高50％和71％,低相变点焊条焊接的两种型式接头的疲劳强度分别提高11％和41％,相应接头的疲劳寿命也有大幅度的提高。试验结果说明,两种方法都是提高焊接接头疲劳强度的有效方法,其中超声冲击方法的提高程度较高,而由于免去了焊后加工处理工序,低相变点焊条方法更适合于具有高值残余拉伸应力纵向焊缝焊接接头疲劳强度的改善。

LOW TRANSFORMATION TEMPERATURE ELECTRODE AND ULTRASONIC PEENING USED FOR IMPROVING THE FATIGUE STRENGTHS OF WELDED JOINTS

The fatigue strengths of welded joints in welded structures are much lower than those of the base metal because there are stress concentrations and tensile residual stresses at weld toes. Ultrasonic peening (UP) treatment and the use of low transformation temperature electrodes (LTTE) are new developed methods for improving the fatigue strengths of welded joints. The fatigue tests of two methods are carried out on both transverse butt welded joints and longitudinal fillet welded joints. The fatigue strengths at 2X 106 cycles of the two kinds of welded joints treated by ultrasonic peening are respectively improved by 50% and 71% compared with those of the as-welded condition. The fatigue strengths at 2 X JO6 cycles of the two kinds of welded joints welded with low transformation temperature electrodes are respectively improved by 11% and 41% compared with those of E5015. In addition, their fatigue lives are also increased by from several times to hundred times at different stresses. The test results show that the UP and LTTE are eifective methods to improve the fatigue strengths of welded joints. It is suggested that UP is used to improve the fatigue performance of transverse butt welded joints, but it is thought that the LTTE may be particularly suitable for longitudinal welded joints containing high tensile residual stresses since it is not necessary to add another process after welding.