Preparation Technology And Welding Properties Of Quenched And Tempered High Strength Q890D Steel Plate

With the rapid economic and social development,construction machinery tends to be more large-scale,more lightweight,and safer.Traditional low-alloy steel has been gradually replaced by high-strength steel,and its application in the field of construction machinery manufacturing becomes more and more extensive.The successful design and application of construction machinery products not only depend on the design and selection of steel materials,but also greatly depend on the design of the welding process and the welding quality of the product.Based on the analysis of strengthening and toughening mechanism of quenched and tempered high strength steel,the design composition and key preparation process parameters of Q890D steel plate were determined.The test results of steel plate properties and metallographic structure shows that the steel plate prepared by clean steel smelting technology,controlled rolling and controlled cooling technology combined with off-line quenched and tempered heat treatment process has very good comprehensive mechanical properties as well as uniform and fine microstructure along the thickness direction,The steel can meet with the design requirements of high strength steel in the field of construction machinery.Combined with the demand of construction machinery steel,the welding performance of Q890D high strength steel is also evaluated by both welding cold-crack sensitivity test and comprehensive mechanical property test,and the key welding process parameters of steel plate are determined.When the welding preheating temperature is between 150?200?,the occurrence of welding cold-crack can be effectively prevented;When the welding line energy is15k J/cm,the comprehensive performance of the welded joint is the best;When the welding thermal cycle parameter t_8/5 is 20s,the toughness of superheated zone is the best.Through the study of microstructure and mechanical properties of Q890D steel plate in quenched and tempered state,the coupling relationship between microstructure and properties is established,and the micro-mechanism of strengthening and toughening is clarified.By analyzing the influence of steel plate welding process on joint performance,the key welding process parameters suitable for Q890D steel plate are decided,provides the basis for the actual welding of steel plate in the field of construction machinery,a complete set of product development research and the key welding technology results of low alloy high strength steel plate.In addition,it offers the technical basis for the development of higher strength steel plate and the formulation of welding process,which promotes the possibility for the development and application of larger-scale and lighter-weighted construction machinery in the future.