Development of Evaluation Procedures for the Fracture Mecharical Characterization of Welds at Cryogenic Temperatures

大型超导磁体支撑结构承载构件的制造需要对厚截面进行焊接。这些焊接件必须能够承受液氦温度（4K）下的高应力。因此，焊接件的低温断裂韧性是重要的设计参数。研究了厚截面焊接件断裂力学性能的评价方法：1.采用25 mm厚的1 TCT（Compact Tensile Tension）试验机进行了弹塑性断裂韧性（JIC）试验。4K试样评价了下一代聚变堆磁体用锻造JN 1型奥氏体不锈钢厚板焊接件的断裂韧性和温升。焊缝通过钨极惰性气体（TIG）电弧焊使用Inconel 625型填充金属产生。采用Au/0. 07% Fe-Chromel热电偶测量裂纹尖端附近的温升。JN 1型奥氏体不锈钢， ...更多信息 在200 mm厚焊接深度的五个位置测试和分析LD。研究了氮含量对J积分的影响<IC>，发现温升与J积分塑性分量的增加有很好的相关性。2.<IC>在4K下对1 TCT试样进行了J积分试验，以确定氮含量、夹杂物含量和二次裂纹对<IC>锻造JJ 1型奥氏体不锈钢厚板焊接件J积分的影响。试验试件由200 mm厚锻造板的TIG焊件加工而成。在4K应变条件下，测量了母材试样的温度，并用二维有限元分析解释了实验测量结果。3.<IC>采用0.5TCT和1 TCT试样在4K下进行了J_（max）试验，以评价大型螺旋装置超导线圈系统用SUS 316型奥氏体不锈钢电子束焊缝的断裂韧性。对SUS 316型奥氏体不锈钢焊缝在75 mm厚的焊接深度的三个位置进行了测试和分析。4.采用4K下的J_<IC>2<IC>试验和声发射测量相结合的方法对奥氏体不锈钢焊缝进行了表征。5.采用小冲杆试验对奥氏体不锈钢焊缝进行了4K下的断裂韧性测试，研究了加载速率对小冲杆试验结果的影响。少

The fabrication of load-bearing members of large superconducting magnet support structures requires the welding of thick section. These weldments must be capable of withstanding high stresses at liquid helium temperature (4K). Therefor, the cryogenic fracture toughness of the weldments is important design parameter.In this research project, evalustion procedures for the fracture mechanical characterization of thick section weldments are investigated.1.Elastic-plastic fracture toughness (JIc) tests were performed with 25-mm-thick compact tension (1TCT) specimens at 4K evaluate the fracture toughness and the temperature rise of thick section weldment in forged JN1 type austenitic stainless steel plate for the fusion reactor magnets of the next generation. The weld was produced by tungsten inertgas (TIG) are welding using Inconel 625 type filler metals. Au/0.07%Fe-Chromel thermocouples were used to measure the temperature rise near the crack tip. The JN1 type austenitic stainless steel we … More ld was tested and analyzed at five locations through the depth of 200-mm-thick welding. The effect of nitrogen content on J_<IC> is examined, and the excellent correlation between temperature rise and increase in plastic component of J-integral is found.2.J_<IC> tests were carried out with 1TCT specimens at 4K to establish the effects of nitrogen content.inclusion content and secondary cracking on J_<IC> of thick section weldment in forged JJ1 type austenitic stainless steel plate. The test specimes were machined from TIG weldment in 200-mm-thick forged plate. Temperatures of base metal specimen were also measured during straining at 4K,and a two dimensional finite element analysis was used to interpret the experimental measurements.3.J_<IC> tests were carried out with 0.5TCT and 1TCT specimens at 4K to evaluate the fracture toughness of SUS316 type austenitic stainless steel slectron-beam weld for the superconducting coil systems in the Large Helical Device. The SUS316 type austenitic stainless steel weld was tested and analyzed at three locations through the depth of 75-mm-thick welding. The effects of specimen size, precracking temperature and ferrite content on J_<IC> are examined.4.J_<IC> tests supplemented with acoustic emission measurement were conducted to characterize austenitic stainless steel welds at 4K.5.Small punch tests were performed to estimate the fracture toughness of austenitic stainless steel welds at 4K.The effect of loading rate to small punch test results is examined. Less