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2.25Cr-1Mo 钢厚壁压力容器埋弧焊采用焊后低温加热(LTPWHT)代替中间消除应力退火(ISR)、防止焊缝出现横向裂纹的基础是:焊缝残留应力和扩散氢含量峰值(DHC)位于最终焊道之下的硬化区,而采用正确的焊后低温加热即可使扩散氢含量降到引起开裂的临界扩散氢含量以下。埋弧焊的焊缝金属中扩散氢含量决定于熔剂的类型和成分,PF-200粘结焊剂在炉中再次烘干后立刻用于焊接,其焊缝熔敷金属的扩散氢含量约为1mL/100g。该焊剂的抗吸潮性能优异,甚至在30℃、相对湿度80%的大气中暴露24h,其焊缝金属中扩散氢含量尚可与低氢型熔炼焊剂的相应指标媲美。据此建立一个考虑焊剂在潮湿大气中放置而影响焊缝金属中初始扩散氢含量C_(0.0)变化的技术操作程序图,用以确定焊后低温加热条件,它的实用性已被厚板焊缝试验所证实,试验中采用的焊接参数均易于裂纹的产生。此外,还研究了扩散氢沿厚度方向的分布对焊件最大硬度的影响与引起开裂的临界扩散氢含量之间的关系,并确认采用 PF-200粘结焊剂埋弧焊比用普通熔炼焊剂在防止焊缝开裂方面更为安全。
2.25Cr-1Mo steel thick wall pressure vessel submerged arc welding using low temperature heating (LTPWHT) instead of intermediate stress relief annealing (ISR), to prevent the emergence of transverse cracks in the weld is based on: weld residual stress and diffusion peak hydrogen content (DHC ) Is located in the hardened zone below the final weld bead, and proper post-weld low temperature heating reduces the diffusive hydrogen content below the critical diffusible hydrogen content causing cracking. Submerged arc welding metal diffusion of hydrogen content depends on the type and composition of flux, PF-200 bonding flux in the oven again after drying for welding, the weld deposited metal diffusion hydrogen content of about 1mL / 100g. The flux has excellent moisture absorption resistance, and the hydrogen content in the weld metal is comparable with that of the low hydrogen type melting flux even when exposed to an atmosphere of 30 ° C. and relative humidity of 80% for 24 hours. Based on this, a technical operation procedure chart considering the variation of the initial diffusion hydrogen content C_ (0.0) in the weld metal considering the placement of the flux in the humid atmosphere is established to determine the post-weld low-temperature heating conditions, and its practicability has been verified by the thick plate welding Slit test confirmed that the test used in the welding parameters are easy to crack. In addition, the relationship between the distribution of the diffusion hydrogen in the thickness direction and the maximum diffusible hydrogen content in the crack caused by hydrogen diffusion in the thickness direction was also studied. It was confirmed that the PF-200 bond flux submerged arc welding To prevent weld cracking more secure.