Recently, JISCO has successfully used CSP thin slab continuous casting and rolling technology to produce bridge steel for the first time. The properties of the products are all in line with and superior to the national standard. At present, the products have been approved by China’s well-known bridge-building enterprises in China Railway Turnout Bridge, the supply of 360 tons.
In recent years, along with our country highway bridge, the railroad bridge, public-railway dual-use bridge, city viaduct, and overpass construction level unceasingly enhances, it is an effective way to develop high-performance bridge steel products, widen product series and reduce production costs to resist market risks and improve the profitability of enterprises. Through continuous R & D and practice accumulation, JISCO bridge steel production more smooth, and product specifications more complete, have been successfully developed in the Q345 series, Q420 series including weathering steel, and more than 30 steel grades.
“With the support of national policies, the construction of steel bridges in the northwest and southwest regions will usher in a new wave of construction,” said Yang Hua, a responsible engineer for hot-rolled high-strength steel at the Institute of Carbon Steel and strip research at Hongxing Steel Research Institute, after a recent period of market research, I have learned that at present, steel + concrete structures are mostly used in the construction of viaducts in China, the bridge steel with 8-30mm thickness, grade Q345QC, and Q345QD is in great demand, mainly used for processing u-beam and support, the thickness of 8 -14 mm bridge steel demand accounts for the overall steel consumption of about 20%.
To meet the market demand, the carbon steel sheet plant decisive decision, immediately set up CSP thin-gauge bridge steel product development team. “Using CSP thin slab continuous casting and rolling technology to produce bridge steel can shorten the production cycle, save energy consumption, reduce production costs and increase the yield,” Yang said, but there are also drawbacks, compared with the bridge steel produced by medium and heavy plate, the compression ratio of CSP production line is small, and it is difficult to ensure the low temperature stamping performance of the steel plate during rolling. This is a rigid index in the production of bridge steel, which means that at low temperature, the higher the value of low-temperature stamping, under the impact of external forces, the steel plate is less prone to brittle fracture.
Faced with the challenge brought by rolling thin-gauge bridge steel, the key members of assembly equipment, technology and production line of the carbon steel sheet plant jointly evaluated the existing risks in production, carried out risk identification in advance, and formulate targeted measures and emergency measures to minimize the risk. In order to ensure the excellent low-temperature stamping toughness of steel plate, the technical personnel changed the ratio of micro-alloying elements and adopted the low-carbon and micro-titanium process to continuously improve the purity of molten steel, at the same time, the process design, chemical composition optimization, and precision control, process temperature matching, mold powder optimization, and process parameters, etc., finally, the key problems of thin slab steelmaking, continuous casting and thin gauge rolling were solved.
After a month of technical research, the carbon steel sheet factory has successfully realized the development of thin-gauge bridge steel, the first batch of 6mm and 8mm Q345QD bridge steels with impact toughness of minus 20 ° C were successfully rolled off the CSP production line. The products are used in key parts such as steel box girders of bridges. The test shows that the low-temperature impact value of the product is much higher than the national standard, with high strength, strong bearing capacity, good formability, and more economical and practical.