基于BP神经网络的回火温度对LCMB钢力学性能的影响研究

基于BP神经网络的方法和原理,避开寻找材料性能的本构方程,采用BP神经网络强大的映射能力来研究LCMB钢的力学性能。结果表明,随回火温度的升高,抗拉强度有明显的下降趋势,而屈服强度则没有明显的变化,小幅上下波动;伸长率则随回火温度的升高一直在增大。BP神经网络的预测精度高,系统收敛速度快,误差范围在2%以内,具有很高的可靠性,对进一步研究LCMB钢有很大促进作用。

Mn-Series Low-Carbon Air-Cooled Bainitic Steel Containing Niobium of 0.02%

A new hot rolled low-carbon air-cooled bainitic steel containing Nb of 0.02% has been developed based on alloying design of the grain boundary allotriomorphic ferrite （FGBA）/granular bainite （BG） duplex steel. The as-rolled microstructure and mechanical properties of bainitie steel containing Nb of 0. 02% were investigated by tensile test, optical microscopy （OM）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results show that adding 0.02 % of Nb obviously improves the strength without sacrificing toughness of the FGBA/BG steel. Adding 0.02% of Nb not only refines the grain boundary allotriomorphic ferrite grains but also promotes the refinement of granular bainite including its bainitic ferrite and M/A island. Any Nb（C,N） has been hardly observed in the steel containing Nb of 0.02%. It is suggested that the strengthening mechanism of Nb of 0.02% can be mainly attributed to the effect of Nb in solution （solute drag-like effect） on the phase transformation rather than the precipitation strengthening of Nb（C, N） particles.

Effect of cathodic potential on stress corrosion cracking behavior of different heat-affected zone microstructures of E690 steel in artificial seawater

In this work,the stress corrosion cracking(SCC)behavior of E690 steel base metal(BM)and different heat-affected zone(HAZ)microstructures,i.e.,coarse grain HAZ(CGHAZ),fine grain HAZ(FGHAZ),and intercritical HAZ(ICHAZ),was investigated at different cathodic potentials in artificial seawater by slow strain rate tensile tests,scanning electron microscopy and electron back-scattered diffraction measurements.The results show that the HAZ microstructures and BM exhibit different SCC susceptibilities:FGHAZ<ICHAZ<BM<CGHAZ,which are controlled by anodic dissolution(AD)at the open circuit potential.With the cathodic potential equaling to-750 mV,the SCC susceptibility of the four microstructures increases because of the synergistic effect of AD and weak hydrogen embrittlement(HE).At-850 mV,AD is inhibited,and the SCC susceptibility of BM decreases,while the SCC susceptibility of the HAZ microstructures increases.At a potential below-850 mV,the SCC susceptibility of the four microstructures gradually increases because of the augment of HE,and the SCC susceptibility of the HAZ microstructures is higher than that of BM.The distinction reveals that the HAZ microstructures have the greater HE susceptibility than BM.

960 MPa Grade High Performance Weldable Structural Steel Plate Processed by Using TMCP

To develop high strength, good toughness, and weldable steel plate, a steel composition was designed. It was an ultra-low-carbon microalloyed steel. TMCP （thermal mechanical control process） and RPC （relaxation precipitation control） were employed to ensure fine lath bainite microstructure. This kind of microstructure could induce higher strength and better toughness.

Microstructure and Mechanical Properties of 1,000 MPa Ultra-High Strength Hot-Rolled Plate Steel for Coal Mine Refuge Chamber

The 1,000 MPa ultra-high strength hot-rolled plate steel with low-carbon bainitic microstructure was developed in the laboratory for coal mine refuge chamber. The static recrystallization behavior, microstructure evolution, and mechanical properties of this hot-rolled plate steel were investigated by the hot compression, continuous cooling trans- formation, and tensile deformation test. The results show that the developed steel has excellent mechanical properties at both room and elevated temperature, and its microstructure mainly consists of lath bainite, granular bainite, and ferrite after thermal-mechanical control process （TMCP）. The ultra-high strength plate steel is obtained by the TMCP process in hot rolling, strengthened by bainitic transformation, microstructure refinement, and precipitation of alloying elements such as Nb, Ti, Mo, and Cu. The experimental steel has relatively low welding crack sensitivity index and high atmospheric corrosion resistance index. Therefore, the developed steel has a good balance of strength and ductility both at room and elevated temperature, weldability and corrosion resistance, and it can suffice for the basic demands for materials in the manufacture of coal mine refuge chamber.