Papers by Author: Yong Feng

Abstract: The grade 590MPa high strength steel for construction machine and mine machine can be produced in mass and at lower cost with optimization of chemical composition and production process. The thickness of steel plates is from 6 mm to 60 mm. The microalloy system can be designed as Nb-V,Nb-Ti or Nb-Ti-V. Due to application of controlled rolling and controlled cooling (thermal mechanical control process TMCP) the properties of steel plates are perfect. Test and process simulation be conducted in lab rolling mill. The results and process were transplanted to middle plate mill and heavy plate mill, the process parameter can be matched well and appropriately, the production process is smooth and properties of steel plates are excellent and stable. The new manufacture technology for production of 590MPa high strength steels is opened up. The output of 590MPa high strength steels has been reached more than 81000 tons every year in Jinan Iron and Steel Co. Ltd. and it meet the needs of market preferably. The application of this type high strength steel can create a great of economy and social profits.

Abstract: The phase transformation rule, microstructures and properties of JG590 high strength steel produced in Jinan Iron and Steel Co. ltd. have been investigated in this paper. When the chemical composition of steel are given, the cooling rates after finished rolling affect on the properties of steel greatly. The yield strength and tensile strength increasing, the elongation and reduction of area decreasing as increasing of cooling rates after rolling. The main cause is due to appearance and increasing of Bainite and Martensite other than Ferrite and Pearlite in room temperature. The finished rolling temperature have distinct effects upon the mechanical properties of steel plates. Finished rolling at different temperature with the 0.5°C/s cooling rate, the tensile strength vary in 599-698MPa, the yield strength changed from 412 MPa to 536MPa. The elongation is between 30.4-40.5%. But when finished rolling at different temperature with the 2.0°C/s cooling rate, the tensile strength vary in 747-784MPa, the yield strength changed from 441 MPa to 601MPa. The strength index can both meet the requirements of employ. But the elongation is only 18.7-24.5%. This is related with production of lots of Bainite microstructure more than 2°C/s cooling rate. In the procedure of manufacture of JG590 high steel, the quickly cooling rate should be avoided to keep suitable microstructure and good elongation and toughness.