Changsheng Li

Effect of ball scribing on relative permeability of grain-oriented electrical steel

Effect of ball scribing on relative permeability of conventional grain-oriented (CGO) and high permeability grain-oriented (HGO) electrical steel was investigated. The samples were scribed with spacing of 2 mm, 4 mm, 8 mm and 16 mm. The results show that after ball scribing with 16 mm width at 1.0 T, relative permeability of both CGO and HGO steels was increased by 109% and 80%, respectively. Relative permeability rises as the scribing space increases, with the movement of the peak value of relative permeability to a higher flux density. Relational models describing relative permeability and flux density were constructed with high accuracy based on experimental data. The experimental data curves were analyzed during the magnetizing process.

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

The 1,000xa0MPa 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 transformation, 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.

Microstructure and strength of a bainitic steel for underground mine equipment

To develop high strength steel for underground mine equipment, the microstructure and mechanical property at two different finish cooling temperatures were investigated. The primary microstructures were massive granular bainite. Coarse martensite-austenite constituents as well as a small amount of quasi-polygonal ferrite and degenerated pearlite formed at the finish cooling temperature of 630°. As the finish cooling temperature was lowered to 580°, the steel showed higher yield and ultimate tensile strength of 605 MPa and 870 MPa, respectively. Besides grain coarsening, the strength reduction due to increasing finish cooling temperature is mainly attributed to the existence of the small amount of quasi-polygonal ferrite based on the analysis for available strength models. The effect of a relatively higher proportion of coarse martensite-austenite constituents on tensile property is weakened when small amounts of quasi-polygonal ferrite in granular bainitic steel appear. Thus, a new yield strength model is...

Experimental research on micro-pit defects of SUS 430 stainless steel strip in cold rolling process

In order to improve surface glossiness of stainless steel strip in tandem cold rolling, experimental research on micro-pit defects of SUS 430 ferrite stainless steel was investigated in laboratory. The surface morphology of micro-pit defects was observed by SEM. The effects of micro-pit defects on rolling reduction, roll surface roughness and emulsion parameters were analyzed. With the pass number increasing, the quantity and surface of micro-pit defects were reduced, uneven peak was decreased and gently along rolling direction, micro-pit defects had equally distributed tendency along tranverse direction. The micro-pit defects were increased with the roll surface roughness increase. The defects ratio was declined with larger gradient at pass number 1 to 3, but gentle slope at pass number 4 to 5. The effects of temperature 55° and 63°, concentration 3% and 6% of emulsion on micro-pit effects had not obvious difference. Maintain of micro-pit was effected by rolling oil or air in the micro-pit, the quality o...

Models between Barkhausen noise and coercive force of grain-oriented electrical steel

Effect of ball scribing on relational models between coercive force and Barkhausen noise of conventional grain-oriented (CGO) and high-permeability grain-oriented (HGO) electrical steel was investigated. Models between two parameters in both CGO and HGO electrical steel were established. The results show that after ball scribing, Barkhausen noise of CGO steel increases (26% after 4mms scribing at 1.0T) and that of HGO electrical steel apparently decreases (17.3% with 16mms scribing at 1.0T), while coercive force of both CGO and HGO electrical steel decreases. Models between coercive force and magnetic Barkhausen noise after scribing were also constructed according to experimental data, and the experimental data curves were analyzed in the magnetizing process, which provides reference for correlation of different magnetic parameters.