Microstructural Refinement by Cu Addition and Its Effect on Strengthening and Toughening of Sour Service Line Pipe Steels
Microstructural Refinement by Cu Addition and Its Effect on Strengthening and Toughening of Sour Service Line Pipe Steels
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添加Cu的显微组织细化及其对酸性管线钢强韧化的影响
DOI：
10.2355/isijinternational.36.241
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发表时间：
1996
影响因子：
1.8
通讯作者：
M. Iino
中科院分区：
文献类型：
--
作者：
A. Takahashi;M. Iino
酸性管线钢的Mn含量希望是低的，因为Mn形成伸长的MnS和偏析条纹，所述伸长的MnS充当氢诱导的气泡裂纹的成核位点，所述偏析条纹提供裂纹的传播路径。另一方面，Mn是最有效和最经济的合金化元素之一。研究了Cu替代Mn对低Mn管线钢的强韧化效果。当Cu含量达到1.7%时，合金的屈服强度提高，夏比转变温度降低，这是由于Cu的晶粒细化作用。然而，超过2.0质量%的Cu添加量随着屈服强度的增加而显著提高转变温度，这一不利影响归因于热轧后冷却期间的析出。通过对热变形后等温保温和热变形后连续冷却的结果分析，提出了溶质Cu细化晶粒的机制。奥氏体中的固溶态Cu阻碍了热变形奥氏体的再结晶，使未再结晶奥氏体保留较多，有利于铁素体形核。此外，奥氏体中的溶质Cu抑制贝氏体-铁素体转变，这降低了转变温度，从而防止形成的铁素体晶粒粗化。
The Mn content of sour service line pipe steels is desirable to be low because Mn forms the elongated MnS which acts as nucleation sites of hydrogen induced blister craking, and the segregation streak which provides the propagation path of the cracking. On the other hand, Mn is one of the most effective and economical alloying elements to strengthen and toughen. This study investigates the effect of Cu as an alternative to Mn to strengthen and toughen the line pipe steels containing low Mn. The Cu addition up to 1.7 mass% simultaneously increases yield strength and decreases Charpy transition temuperature, which effect of Cu is attributable to grain-refinement. However, the Cu addition over 2.0 mass% substantially raises the transition temperature with increasing the yield strength, which adverse effect is attributable to the precipitation of during cooling after hot rolling. Analyzing the results of the isothermal holding after hot deformation and the continuous cooling after hot deformation provides the mechanisms of the grain-refinement by solute Cu as follows. The solute Cu in austenite retards the recrystallization of hot deformed austenite, which retains more non-recrystallized austenite enhancing ferrite nucleation. Moreover, the solute Cu in austenite suppresses the austenite-ferrite transformation, which decreases the transformation temperature and thereby prevents formed ferrite grains from coarsening.