900MPa含Ti低碳贝氏体钢的研究

Study on Ti-bearing low carbon bainitic steel with 900 MPa yield strength

采用高Ti成分设计,通过高温轧制方法制备了3种含硼和不含硼7 mm厚的高强度贝氏体钢板,对钢中合金元素的作用以及加热、轧制工艺对钢板性能的影响进行了研究。结果表明,含硼钢板经600℃回火后,屈服强度达920 MPa,伸长率14.0%;回火后的含硼和不含硼钢板在-60℃～-20℃条件下5 mm厚试样的冲击韧度值均大于50 J,冲击断口具有韧窝形貌,并有大量平行于轧制方向的分层。含硼钢板具有细小板条贝氏体组织,原奥氏体晶粒宽度在10μm左右,内部贝氏体板条宽度150～300 nm。这种细小的贝氏体组织以及冲击试验中出现的断口分层现象,使钢板在达到极高屈服强度的同时,仍具有极佳的低温韧性。

By addition of high concentration of titanium ,Ti-bearing and Ti-B-bearing high strength bainitic steels with thickness of 7 mm were prepared by high temperature processing（HTP） method. Influence of alloy elements, reheating and rolling process on mechanical properties of the test steels were investigated. The results show that Ti-B-bearing steel exhibits higher yield strength of 920 MPa and elongation of 14. 0% after being tempered at 600 ℃. The Charpy impact energy of Ti-bearing and Ti-B-bearing steels at - 60 ℃ - - 20 ℃ exceeds 50 J with ductile fracture appearance. Delamination cracks parallel to the rolling direction are found in Charpy test specimens of all the test steels. Ti-B-bearing steel has a mean austenite grain size of about 10 μm and the internal bainitie lath width is about 150-300 nm. The fine lath bainite microstructure as well as the delamination phenomenon in impact specimens contributes to the extra-high strength and excellent low temperature toughness of the Ti-B-bearing steel.