Stainless Steel----Medium steel plate new rolling technology
Medium steel plate Mainly used for ships, bridges , boilers, vessels , petrochemical , construction machinery and defense construction , with its variety, wide temperature region (-200 ~ 600 ℃), using a complex environment ( weather, corrosion resistance, etc. ) , the high requirements ( toughness, weldability , etc. ) . Therefore , the thick steel plate steel products is a strategic national economy. Plate Rolling in the control of the organization is the key to improving the performance of the yield of steel , in this respect , at home and abroad in recent years, new technologies are being developed mainly in the following .
One . Intermediate cooling technology.
From the current domestic situation of controlled rolling process applications , controlled rolling is the most widely used two-stage rolling, rolling and recrystallization region that unrecrystallized area rolling . In this two- stage partial recrystallization region need to avoid the intermediate rough finish rolling billet air-cooled until the temperature measures in order to meet this requirement is taken . Intermediate cooling device is between roughing and finishing mill production line or two-rack single stand rolling mill before or after the machine to increase cooling devices to reduce intermediate billet rollers to be warm in time, improve the mill 's production capacity. Using this apparatus , the intermediate billet temperature can be shortened to be 35% to 80% . The device combines the control of the intermediate cooling after rolling and rolling and controlled cooling , the surface can also be used to produce ultra-fine grain steel, or called sandwich steel, the steel because of a certain thickness (4mm) of ultra-fine grain layer, with high crack arrest performance. Of Tangshan Iron and Steel , Nanjing Steel billet additional intermediate cooling equipment , not only improves the production capacity of the mill , but also strengthened the ability to control the microstructure and properties of steel , expanding the range of steel products .
Two . Pre- straightening technology.
Pre- leveler can be installed between the steel finishing mill and the cooling device , its purpose is to reduce the head or tail plate warpage and correct flatness defects steel middle section . Straightening operations to avoid detrimental accumulation of water on the steel plate and improve the uniformity of cooling , to obtain a final product of good flatness . Pre- roller straightening confidential and synchronized with the speed and accuracy with the perfect combination of cooling technology .
Three . Ultra- dense laminar cooling technology.
Beijing University of Science and Technology has recently developed ultra- dense laminar cooling system , the cooling system can not only greatly improve the cooling rate of the steel plate , steel to improve performance , and can not increase on the basis of operating costs , reduce the cost of the alloy . Japan's JFE developed its cold ratio of super-cooling system increased by 50 %, and its 20mm thick steel plate cooling rate can reach 45 ℃ / s. Currently , the use of the equipment system , has successfully developed a high-strength and high-strength steel Q550-Q800 container board N610E.
Four . Line heat treatment technology.
Direct quenching being developed - online and direct quenching and tempering process - process and production cycle is short compared to the tempering process , energy magnitude greater. The final line quenching temperature is not cold room , but the low-temperature phase transition temperature range , so you can take full advantage of the online tempering heat . According to reports, online heating rate 10 ~ 20 ℃ / s, holding time is less than 5 minutes , the tempering time is greatly reduced compared to offline .
Five . Normalizing controlled cooling technology.
Normalization process is an important means to improve the uniformity of steel microstructure and toughness . By controlling the cooling rate and the final cooling temperature to control the temperature of the steel sheet after the normalization of the phase transition , and inhibition of the micro- alloying elements carbonitride was grown , the precipitates and grain refinement to improve the strength of the steel sheet , while substantially maintaining toughness and ductility changed.