Cr15Mn9Cu2Ni1N不锈钢连铸坯的高温拉伸变形特性

Tensile deformation characteristics of Cr15Mn9Cu2Ni1N stainless steel slab at elevated temperature

对于Cr15Mn9Cu2Ni1N不锈钢连铸坯,热变形过程中变形局部化的发生会影响其表面质量。从连铸坯的表层及芯部制取小型试样,利用热/力模拟试验机,进行温度950℃～1150℃范围内的拉伸试验。结果发现,随变形温度升高,该钢强度降低而延伸率提高;试样在发生颈缩,即变形局部化之前,要经历均匀变形和扩散颈缩变形,两种变形均使试样变形区获得均匀的宏观变形形貌;而高温拉伸的延伸率主要由扩散颈缩阶段的变形量决定。分析表明,均匀变形阶段主要靠应变强化抑制变形局部化的发生,而扩散颈缩变形阶段应变速率强化起主导作用。随变形温度升高,尤其在温度高于1100℃时,该钢的应变速率强化效应增强,可推迟最终变形局部化的发生,从而获得较大的延伸率。

For Cr15Mn9Cu2Ni1N stainless steel slab,the occurrence of strain localization during the hot deformation may cause surface defects.Small specimens were cut from the surface layer and the core of a slab,and tension tests were performed on thermal-mechanical testing machine at 950℃~1150℃.Experimental results show that,with the increase of deformation temperature the strength are decreased and percent elongation increased.Before the occurrence of necking or strain localization,specimen experienced two stages including uniform deformation and necking diffusive deformation,both of which causing deformation zone of specimen to obtain macroscopic uniform appearance.The percent elongation of hot tensile test is mainly dependent on the deformation during the stage of necking diffusion.It is understood that during stage of uniform deformation the inhibition of strain localization is mainly depended on strain hardening;during stage of necking diffusive deformation strain rate hardening played a vital role in obtaining larger macroscopic uniform deformation.With the increase of deformation temperature,particularly as temperature higher than 1100℃,strain rate hardening effect of this steel is strengthened,and the occurrence of necking is postponed,thus bigger percent elongation is obtained.