Progress of Sintering Technology in Handan Iron and Steel Company

As one of the biggest iron and steel companies in China, Handan Iron and Steel Co has made a substantial progress in the sintering process. The mini-pellet sintering technology has been successfully applied based on lab investigation and industrial trials. Equipment enlargement was realized through replacing small sintering strands with the construction of huge sintering machine with a grate area of 400 m 2. The productivity, iron content and the metallurgical properties of sintering process have been improved.

Mathematical modeling of flow field in slab continuous casting mold considering mold powder and solidified shell with high temperature quantitative measurement

Optimization of mathematical model of flow field in slab continuous casting mold was performed by means of industrial measurement and mathematical modeling.The rod deflection method was used to quantitatively measure the velocities near the mold surface at high temperature.The measurement results were compared with the simulation results of three mathematical models at different argon gas flow rates of 6,10 and 14 L min^(−1).The model 1 neglects the mold powder layer,thermal effect and solidified shell.The model 2 only considers the influence of mold powder layer.The model 3 considers the influence of mold powder layer,thermal effect and solidified shell on the flow field.In all three models,the diameter of argon bubbles obeys Rosin-Rammler distribution fitted according to the experimental data of others’previous work.With increasing the argon gas flow rate,the velocity of liquid steel near the mold surface decreases.The model 1 seriously underestimates the shear stress of liquid steel near the mold surface,and its calculation results show higher velocity near the mold surface,lower turbulent kinetic energy and wider distribution of argon gas bubbles in the mold.The simulation results of model 2 only considering the viscous resistance of the mold powder layer to liquid steel makes the velocity near the surface lower than the measurement results obviously.The calculated velocities near the mold surface with model 3 are in best agreement with the measured results,showing the reasonable spatial distribution range of argon bubbles in the mold and the moderate turbulent kinetic energy.In the present conditions,the best argon gas flow rate is 10 L min^(−1) due to the moderate velocity near the mold surface,the appropriate distribution of argon gas bubbles in the mold and the smallest fluctuation amplitude on the mold surface.

Microstructure evolution and mechanical properties influenced by austenitizing temperature in aluminum-alloyed TRIP-aided steel

The Fe-0.21C 2.2Mn 0.49Si-1.77A1 transformation induced plasticity （TRIP） aided steel was heat trea- ted at various austenitizing temperatures under both TRiP-aided polygonal ferrite type （TPF） and an- nealed martensite matrix （TAM） processes. The microstructure evolution and their effects on mechanical properties were systematically investigated through the microstructure observation and dilatometric analysis. The microstructure homogeneity is improved in TPF steel heated at a high temperature due to the reduced banded martensite and the increased bainite. Compared with the mechanical properties of the TPF steels, the yield strength and elongation of the TAM steels are much higher, while the tensile strength is lower than that of TPF steels. The stability of intercritical austenite is affected by the heating tempera- ture, and thus the following phase transformation influences the mechanical properties, such as the bain- ite transformation and the precipitation of polygonal ferrite. Obvious dynamic bainite transformation occurs at TAM850, TAM900 and TAM950, More proportion of polygonal ferrite is found in the sample heated at 950 ℃. The bainite transformation beginning at a higher temperature results in the wider bainitic ferrite laths. The more proportion of polygonal ferrite and wide bainitic ferrite laths commonly contribute to the lower strength and better elongation. The uniform microstructure with lath-like morphology and retained austenite with high average carbon content ensures a good mechanical property in TAM850 with the product of strength and elongation of about 28 GPa ·%,

Generation mechanism of quarter buckle in hot-rolled temper rolling

To reveal the generation mechanism of the quarter buckle in the process of hot-rolled temper rolling,the elastic–plastic finite element method is used to calculate the deformation of the roll and the strip during the temper rolling.The change of the cross section of the strip and the distribution of the longitudinal stress are analysed under different bending forces to obtain the boundary conditions of the quarter buckle.The generation of the quarter buckle is further analysed from the bending and contact flattening of the roll system and the elastic recovery of the strip after rolling.We found that the quarter buckle is closely related to the high-order distribution of the contact flattening between the work roll and the strip and is less affected by the bending deformation of the roll and the contact flattening between the rolls.Finally,a new work roll contour of the locally variable crown is proposed to change the distribution of contact flattening between the work roll and the strip.It is verified through theoretical calculations and industrial applications that the new contour can effectively improve the quarter buckle.