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国外电站锅炉中奥氏体不锈钢与珠光体热强钢异种钢焊接接头长期运行后容易产生开裂的原因,据分析认为是:焊缝金属与基本金属之间线膨胀系数不同,在母材与焊缝的交界面上产生高的应力,在母材与焊缝交界面上产生应力氧化,在母材与焊缝交界面附近靠近低合金钢一边有一个窄的脱碳区,该脱碳区将产生加速蠕变。为解决这个问题,国外有的工厂采用过渡接头的方法,选择接头材料时使线膨胀系数阶梯过渡。F11钢与12CrlMoV钢的异种钢接头也存在奥氏体钢与珠光体钢异种钢接头类似的问题。国内生产的四台400吨/时锅炉8只再热器集箱三通16只F11钢与12CrlMoV钢的异种钢接头,运行一万小时左右均发生开裂。为解决这个问题,生产上采用含铬量阶梯过渡,即12crMoV-热337-热417-热507-热817-F11的办法。为验证这种过渡接头的可靠性和合理性,对这种形式的过渡接头进行了持久强度试验和金相观察。持久强度试验结果表明这种形式的过渡接头熔合线附近的持久强度是高的。
Foreign power station boiler austenitic stainless steel and pearlite hot steel dissimilar steel welded joints prone to cracking after long-term reasons, according to the analysis is that: the weld metal and the basic metal between the different coefficients of linear expansion in the base metal and welding High stress is generated at the interface of the seam, resulting in stress oxidation at the interface between the base metal and the weld. There is a narrow decarburization zone near the low alloy steel near the interface between the base metal and the weld. The decarburization zone Produce accelerated creep. In order to solve this problem, some factories in other countries adopt the method of transition joint to make the transition of the coefficient of linear expansion transition when selecting the joint material. Dissimilar steel joints of F11 and 12CrlMoV steels also have similar problems with dissimilar steel joints of austenitic and pearlite steels. Domestic production of four 400 tons / hour boiler 8 reheater header three links 16 F11 steel and 12CrlMoV steel dissimilar steel joints, running 10,000 hours or so have occurred cracking. To solve this problem, the production of chromium-containing step ladder, that is, 12crMoV-hot 337-hot 417-hot 507-hot 817-F11 approach. To verify the reliability and rationality of this transition joint, this type of transition joint was tested for durability and metallographic observation. Long-term strength test results show that this type of transition joints near the weld line lasting strength is high.