Influence of Strands' Brittle Zones on Surface Cracks of Hypo-peritectic Steel
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摘要: 针对微合金亚包晶钢凝固过程中产生大量裂纹缺陷的现状，采用光学显微镜、扫描电镜及能谱分析仪对铸坯表面裂纹进行分析，并对析出物进行热力学计算，利用Gleeble-1500对铸坯热塑性进行分析研究。结果表明：裂纹处存在（Fe，Mn，Si，Al）（S，O）等夹杂物，加剧应力对基体的影响；裂纹处存在Ti-Al-（C，N）夹杂物，增加了γ→α转变的脆性，横裂纹敏感性增加。高温脆性区易产生纵裂，断面收缩率（Z）最小值为37.59%，纵裂纹敏感区间为1 454~1 478℃。900~750℃为低温脆性区，易产生横裂纹，Z最小值为45.24%，横裂纹敏感区间900~750℃。896℃时，铁素体开始析出，使得晶界上进一步集中，导致裂纹发生。Abstract: In view of large amounts of cracks formed in the hypo-peritectic HSLA steel during solidification,the cracks on the surface of strands were analyzed by optical microscope,SEM and EDS,and the precipitates were studied by thermodynamic calculation. Furthermore,hot ductility was studied by Gleeble-1500. The results showed that steel matrix was deteriorated by inclusions(Fe,Mn,Si,Al)(S,O) in cracks,and transverse cracking sensitivity was increased by Ti-Al-(C,N) inclusions. The longitude cracks tend to appear in the high-temperature brittle zone with a longitude cracking sensitive range of 1 454~1 478℃,and the minimum value of Z was 37.59%; the transverse cracks tend to appear in the low-temperature brittle zone with a longitude cracking sensitive range of 900~750℃,and the minimum value of Z was 45.24%. Precipitating at 896℃,the ferrite led to strain concentration on the grain boundary,resulting in crack formation.
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Key words:
- hypo-peritectic steel /
- cracking sensitive range /
- brittle zone /
- ferrite /
- precipitate
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