Papers by Author: Guo Dong Wang

Abstract: An Fe-6.2wt%Si as-cast strip with equiaxed grains and obvious {001} fiber texture was produced by twin-roll strip casting process. The as-cast strip was successively performed by hot rolling, warm rolling and annealing. The microstructure and texture evolution at each process stage were investigated by using electron backscatter diffraction and x-ray diffraction. It was found that the finally annealed sheet was characterized by large grain size, mild γ-fiber texture and obvious {001} fiber texture. Therefore, a high magnetic induction and a low core loss were obtained in the sheet.

Abstract: To develop 590/780MPa grade low yield ratio structural steel, the effects of ultra fast cooling (UFC) new process on microstructure and mechanical properties were investigated. The results showed that the low yield ratio and high strength can be obtained by proper phase compositions including relative soft phase and hard phase. For the process of UFC + air cooling, when UFC final cooling temperature was 521°C, 22.5% M-A second hard phases were distributed on bainite ferrite matrix in steel No.A2. The mechanical properties can meet requirement of 590MPa grade low yield ratio structural steel. For the process of air cooling + UFC, when UFC initial cooling temperature was 781°C, the multiphase composed of 28.3% ferrite and other bainite / martensite lath structure can ensure the high strength and low yield ratio of steel No.B1. And performance indexes can meet the requirement of 780MPa grade low yield ratio structural steel.

Abstract: Based on the new generation TMCP technology, The State Key Laboratory of rolling and automation, Northeastern University(RAL) developed an advanced cooling system(ADCOS-PM). The system was combination of ultra-fast cooling (UFC) equipment with the advantage of high cooling intensity and homogeneous cooling and traditional accelerated cooling equipment(ACC). The UFC equipment was composed of jet impingement cooling device with high-pressure water and the ACC equipment was composed of laminar cooling device with good controllability. The control object of ADCOS-PM control system including finish cooling temperature and cooling-rate of every stage was controlled by adjusting the parameters such as the run-out table speed, state of active and inactive jet, flow rate of active jet. The temperature profile of plate was completed on the run-out table so that the product with fine microstructure and good mechanical properties was produced. The ADCOS-PM was built in 4300mm plate mill of Anshan Iron and Steel Co., Ltd. in 2010 and the recycling products with high-performance were produced.

Abstract: Focusing on the need of actual production, physical analogue experiments were done on the 400MPa ultra fine grained steel under different welding heat circulations. The experiment results showed that grains growing up and performance dropping was inevitable, the coarsening temperature range was 1000~1200 ; where the heating temperature was 800 in the Heat Affected Zone, the soften was the most obvious, but when the cooling rate t_8/5<10s, the soften disappeared; speeding up the cooling rate could improve the microstructure of the Heat-affected Zone effectively and made the mechanical properties of the joint better than that of the base metal.

Abstract: The medium and heavy plate of 800 MPa grade ultra-fine grained steel was welded by CO₂ gas shielded welding using large line energy. The effect of cooling condition on microstructure and mechanical properties of welded joints was investigated. The results showed that the cases about significant grain size increasing and strength decreasing do exist in the heat affected zone of large line energy welded joints of 800 MPa grade ultra-fine grained steel. Grain growth and softening in the heat affected zone could be suppressed effectively by water cooling in the course of welding. The mechanical properties of welded joints could be significantly increased by water cooling, and the process of CO₂ gas shielded welding under water cooling is practical for joining ultra-fine grained steel using large line energy.

Abstract: The effect of hot rolling parameters including different hot rolling reduction, soaking time of ingots and chemical composition on cold rolling texture by TSCR process was studied. The result indicates that α fibers and γ fiber texture were affected by hot rolling reduction, and oriented density αfibers texture increases with hot rolling reduction rate increasing, and the texture components is same in the surface and different in the center. The strength of γ fiber texture, from {111}<110>to {111}<112>, is decreasing trendency for ingot soaked for 10min and 20min. however, changing trendency from {111}<110>to {111}<112> in 1/8 thickness and 1/4 thickness of cold rolling strip for ingot soaked for 30min. The volume fraction of {111}<112> is rising with the ingot soaked time and the maxium is 3.5 percent, and the volume fraction of {111}<112> is higher in every layer of cold rolling strip whose chemical composition includes Sn than without Sn, the volume fraction of {111}<112> is higher in 1/8 and 1/4 layers than the surface and center layers.

Abstract: The microstructure and textures of oriented silicon steel produced by Thin Slab Casting and Rolling (TSCR) were studied in laboratory. The fractions of equiaxed grains and columnar grains are close to 35% and 65% respectively in as-quenched ingot after being pulled out from the mould. The equiaxed grains and no texture gradient from surface to center can be observed for the 3-pass hot-rolled strips, and the inhomogeneities of microstructure and texture in thickness are relatively clear for the 7-pass samples. The subsurface texture of the hot-rolled sample contains of e (TD// <110>) fibers. The texture of the cold-rolled samples mainly consists of a (<110>//RD) and g (<111>//ND) fibers, and Goss texture ({110}<001>) disappears. The strong a fiber, weak g fiber and minor {001}<110>can be found in all layers in the cold-rolled condition.

Abstract: According to the characteristic of plate rolling process and the on-line applications, the non-homogeneous wear and thermal expansion of rollers, the elastic recovery and thermal expansion of work pieces, the variation of oil film thickness and the zero point deviation, which influence the precision of gap setting model, are analyzed. Based on the results of analysis, a high-precision gap setting model is proposed, and a zero point correction method is developed, in order to avoid overshoot, damp coefficient, which is affected by the thickness of work piece and zero point deviation are considered, is introduced. On-line applications indicate that the gap setting model improves the precision of gap setting and laid a good foundation of further improvement of thickness accuracy.

Abstract: In twin-roll thin strip casting, the temperature of casting roll affects the roll thermal stress, and influences the thermal deformation, the generation of roll surface cracks, the strip shape and the service life of casting roll. In this paper, the features of the casting roll materials have been analysed, the effects of the clad materials and thickness on temperature field of the casting roll have been simulated and discussed. The developed temperature model of casting roll is helpful in optimising processing parameters and the design of casting roll during twin-roll thin strip casting.

Abstract: Based on the character of plate rolling, the temperature model was developed by considering the influence of radiation, convection, water descaling, and roll conductivity and deformation energy. The factors affect the finishing temperature of the plate were analyzed, including the holding time during control rolling, rolling speed, slab temperature and pass number. Holding time, rolling speed and slab temperature have significant influence on finishing temperature, and pass number has great influence on finishing temperature of thick plate, but has little on finishing temperature of media plate.