Optimization of Holding Temperature and Holding Thickness for Controlled Rolling on Plate Mill

Holding temperature and holding thickness are main parameters for two-phase controlled rolling on plate mill. The optimization of holding temperature and holding thickness for pass schedule calculation of two-phase controlled rolling on plate mill was presented and its feature is as follows： （1） Determination of holding thickness can be automatically obtained based on the influence of mill safety limits, tracking zone length and holding time on holding thickness; （2） Determination of holding temperature can be automatically obtained and the holding time can be reduced as much as possible; （3） Algorithm can modify the holding temperature and thickness depending on slab size and product size.

Effect of Cr and isothermal holding temperature on microstructure and properties of complex phase steel with high formability(CH steel)

The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated using dilatometry,scanning electron microscopy,transmission electron microscopy(TEM),and X-ray diffraction.The results show that the microstructures of CH steel with 0.3 wt.%Cr are ferrite,granular bainite,martensite,and retained austenite,while no ferrite is observed in the microstructure of CH steel with 1.0 wt.%Cr in the same process.Cr promotes the precipitation of(Nb,Ti)C in the high-temperature austenite region through theoretical calculations and TEM observations.Cr retards the bainite transformation and refines the grain size of CH steel.Furthermore,as isothermal holding temperature increases from 400 to 480℃,the bainite and retained austenite fractions of two CH steels decrease,while the martensite fraction increases in the steels after final quenching.Consequently,the strength has an increasing tendency and the total elongation has a decreasing tendency with increasing isothermal temperature.

Temperature Holding Hood for Hot Charging of Continuous Casting Slab in Tangshan Iron and Steel Company

To improve the charging of high-temperature billets, it is crucial to produce them with zero defects and achieve effective insulation during their hot delivery. A mathematical model was developed based on the heat transfer characteristics of the billet during its hot delivery. The accuracy of the model was established by studying the thermal performance of the cover of the roller conveyer for small billets in Tangshan Iron and Steel Company. The results show that the cover of the roller conveyer of the continuous casting billet can effectively reduce the heat loss during the hot delivery of the billets, and the hot loading temperature was increased by 51.6 °C. The uniformity of the temperature of the casting billet section increased substantially. The temperature difference in the casting billet section was reduced by 120 °C. The heat preservation effects of temperature holding hoods of different materials were compared. It was found that the material of the temperature holding hood has slight effect on the heat preservation.

Effects of annealing temperature and cooling rate on microstructures of a novel titanium alloy Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si manufactured by laser additive manufacturing

The microstructure changes of Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si alloy manufactured by laser additive manufacturing （LAM） are systematically investigated with statistical analysis of primary α phase （αp） and secondary α phase （αs） under different annealing conditions. Results indicate that, with the increase in holding temperature, the content of αp lamellas decreases with the increasing αs content, maintaining the total α phases concentration stabilized. The width of αp lamellas and the nominal specific surface area of α phase both exhibit positive correlation with the temperature, while the increment of αp and the widths of αs lamellas show an increase-decrease tendency. Besides, with the decrease in cooling rate, the total content of α and the width of αp lamellas increase, while the nominal specific surface area of α phase shows no significant change. The results indicate that, in the annealing process, the holding temperature determines the surplus and growth interfaces of % lamellas, and the cooling rate influences the nucleation quantity of c^s in unit time. During the cooling stage, the αp lamellas grow initially, and then, the nucleation and crab-like structure growth occur followed by those of the αs lamellas. The time intervals among them are influenced by cooling rate. The mechanism of microstructure formation of the LAMed titanium alloy during annealing stage was discussed, which would guide for the heat treatment method to achieve required microstructure.