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含铝低合金钢熔合区“铁索体带”问题。是含铝低合金钢焊接研究工作中的共性问题。作者研究了铁素体带的形成特点。在焊接以后。于熔合线靠含铝低合金钢一侧产生的铁素体带与接头两侧化学成份差异,尤其是与由成份所决定的高温晶体结构的差异有关。高温时的碳活度差是形成铁素体带的主要条件。焊接高温及延续时间为碳扩散的动力学条件。铁素体带使焊接接头的韧性、高温强度、应力腐蚀和电化学腐蚀等性能均有所降低。为减少或消除铁素体带产生,主要从热力学方面考虑,力求缩小高温时碳活度差异,通过调整化学成份,或由此减小母材与焊缝的临界转变温度A_3点的差异。含铝低合金钢焊接时,在熔合区产生铁素体带的现象与异种钢焊接(碳钢、钼钢、铬钼钢之间的焊接以及铬钼钢与奥氏体不锈钢之间的焊接)产生的碳迁移现象在本质上是一致的,都遵循碳活度降低的原理。由于母材中所含元素种类不同,焊接接头呈现脱碳、增碳现象有所差异。含非碳化物形成元素为主的含铝低合金钢焊接时,碳迁移的特征在于产生明显的铁素体带。
Problem of “Iron Cable Body Belt” in Fusion Zone of Low Alloy Steel Containing Aluminum. Is a common problem in the research of low alloy steel welding of aluminum. The author studied the formation of ferrite band characteristics. After welding. The difference in chemical composition between the ferrite tape and the joint on the side of the fusion line against the aluminum-containing low-alloy steel side is particularly related to the difference in high-temperature crystal structure determined by the composition. The difference in carbon activity at high temperature is the main condition for the formation of ferrite tape. Welding temperature and duration of kinetic conditions for carbon diffusion. Ferrite tape to weld toughness, high temperature strength, stress corrosion and electrochemical corrosion and other properties are reduced. In order to reduce or eliminate the ferrite band production, we mainly try to reduce the difference in carbon activity at high temperature by adjusting the chemical composition, or reduce the difference between the critical temperature A_3 of the base metal and the weld. Aluminum-containing low-alloy steel welding, the ferrite zone in the weld zone phenomenon with dissimilar steel welding (welding of carbon steel, molybdenum steel, chrome molybdenum steel and between the welding of chromium-molybdenum steel and austenitic stainless steel) The resulting carbon migration is essentially the same, all following the principle of reduced carbon activity. Due to the different types of elements contained in the base metal, welded joints showed decarburization and carbon enrichment. Carbon-containing transitions are characterized by the formation of distinct ferrite bands during welding of aluminum-containing low-alloy steels that are predominantly non-carbide forming elements.