Effects of Rare Earth on Behavior of Precipitation and Properties in Microalloyed Steels

The influence of rare earths on the behavior of precipitation of 14MnNb,X60 and 10MnV steels was studied by STEM, XRD, ICP and thermal simulation method. The main carbonitride precipitates are Nb(C, N),(Nb, Ti)(C, N)and V(C, N). In austenite RE delays the beginning of precipitation, and decreases the rate of precipitation. In ferrite RE promotes precipitation and increases the amount of equilibrium carbonitride precipitation. RE can make precipitates fine, globular and dispersed in the microalloyed steels. With the increase of the amount of RE in steel, the amount of precipitation increases. The promotion effect is weakened with excessive RE. RE has only little influence on the strength of microalloyed steel, but it can improve impact toughness effectively.

Production Planning System for the Whole Steelmaking Process of Panzhihua Iron and Steel Corporation

A production planning system is designed for the whole steelmaking process, which includes desulfurization, vanadium extraction, steelmaking and continuous casting processes of Panzhihua Iron and Steel Corporation. The system is composed of modeling module, data interface module, data analysis module, static planning module, re-planning module, plan evaluation module, plan simulation module and human-computer interaction module. The system is connected with the L3 system of steel plant by using the data interface module, which can receive the real time scheduling information to make the static plan and re-plan under production disturbances. The simulation and plan evaluation function of the system can assist decision-maker to check and modify the production plan. The simulation experiments with real process data show that the system can make a feasible, executable, and effective production plan, and deal with primary random disturbances during production process timely.

Nonmetallic Inclusion Control of 350 km/h High Speed Rail Steel

Inclusion has an important effect on quality of high speed rail steel. In consideration of the lower acceptance percentage of the inclusion and its constraint against the requirement for large scale production of 350 km/h high speed rail steel in Panzhihua Iron and Steel （Group） Co,the technology of nonmetallic inclusion control for 350 km/h high speed rail steel was studied. An optimized model of the argon-blowing in ladle furnace （LF）,the control of the components of the ladle slag,and the technique of calcium treatment for the molten steel was brought forward. Using the researched technology,the removal ratio of the inclusion was increased and the components,distribution,and shape of the inclusion in the rail steel were changed,which resulted in a reduction in the average total oxygen content to 10.17×10^-6 and an increase in the comprehensive acceptance percentage of the nonmetallic inclusion from 48.21% to 98.1%. Test has shown that this metallurgical technology can meet the requirement for large scale production of 350 km/h high speed steel in Panzhihua Iron and Steel （Group） Co.

Thermomechanical Behavior in Continuous Bloom Casting with Different Mold Tapers

A two-dimensional finite element model was used to analyze the thermal and mechanical behavior during solidification of the strand in a continuous bloom casting mold. The coupled heat transfer and deformation were analyzed to simulate the formation of the air gap between the mold and the strand. The model was used to investigate the influence of mold taper on the temperature and stress distributions in the strand. The results show that the air gap mainly forms around the strand corner, causing a hotter and thinner solidifying shell in this region. The mold taper partially compensates for the strand shell shrinkage and reduces the influence of the air gap on the heat transfer. The mold taper compresses the shell and changes the stress state around the strand corner region. As the strand moves down into the mold, the mold constraint causes compressive stress beneath the corner surface, which reduces the hot tear that forms on the strand.