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采用SEM、EBSD和TEM研究回火工艺对低C含Cu特厚(100 mm)高强韧NV-F690船体和海洋平台用钢板精细组织的影响,深入探讨钢板低温冲击断裂行为与精细组织之间的关系。结果表明,轧后直接淬火态DQ钢板心部(ND/2)组织为板条贝氏体+粒状贝氏体,板条间距较宽,粒状贝氏体中存在较粗大MA组元,低温韧性差;1/4厚度(ND/4)处组织为板条贝氏体,板条间距窄,低温韧性好。650～690℃回火6 h后,大量ε-Cu弥散沉淀相在钢板基体组织中析出,钢板ND/2处粗大粒状MA组元分解,大角度晶界分数增加,有效晶粒尺寸减小,低温韧性显著提高。
SEM, EBSD and TEM were used to study the effect of tempering on the fine microstructure of the low C-containing Cu-rich (100 mm) high-toughness NV-F690 hull and the offshore platform steel plate. The effects of tempering on the microstructure of low- relationship. The results show that the microstructure of the as-quenched DQ steel core (ND / 2) is lath bainite and granular bainite with wide lath spacing and coarse coarser MA elements in the granular bainite. The low temperature toughness Poor; 1/4 thickness (ND / 4) at the organization of lath bainite, lath spacing narrow, good low temperature toughness. After annealing at 650-690 ℃ for 6 h, a large amount of ε-Cu dispersed precipitates precipitated in the matrix of the steel plate. The coarse granular MA constituent in the ND / 2 steel plate was decomposed, the fraction of large-angle grain boundaries increased, the effective grain size decreased, Low temperature toughness increased significantly.