Studies On Weldability And Welding Technology Of Copper-rich Nanoscale Precipitate-strengthened Steel

As a newly developed low-alloy high-strength steel,the Copper-rich nanoscale strengthened steel has good comprehensive mechanical properties by adopting the method of nanoscale precipitation strengthening and traditional strengthening.The weldability and welding process of Copper-rich nanoscale strengthened steel directly affected the quality of welded joints and the popularization and application of it In this paper,the weldability,welding process and welding material matching of copper-rich nanophase strengthened steel were studied through theoretical calculation and welding process tests.The main conclusions of this article are as follows:The carbon equivalent CEN=0.354%,cold crack sensitivity index Pcm=0.1755%,hot crack sensitivity index HCS=0.607,the tendency of cold cracks and hot cracks is low.The base material didn't need preheat at 20?,and there were no cold cracks initiated in the welded joint,which was consistent with the theoretical calculation.The ductile-brittle transition temperatures of welds,fusion zone and heat affected zone were-55.8 0C,-54.6? and-62.8?,and the welded joints have strong resistance to brittle fracture.Under the heat input of 11 kJ/cm,15 kJ/cm and 20 kJ/cm,the manual arc welding tests of the Copper-rich nanoscale strengthened steel were carried out.With the increase of heat input,the strength and toughness of the Copper-rich nanoscale strengthened steel welded joint show a downward trend and the grain size of the welded joint was increased.The microstructure of the weld weld seam was mainly acicular ferrite and the microstructure of the heat affected zone were mainly lath martensite,lath bainite,granular bainite,tempered martensite and a small amount of ferrite,Under the heat input of 15 kJ/cm,the comprehensive mechanical properties of the welded joint were the best,and the strength and toughness of the A welded joint were better than t the B joint.The manual arc welding tests of the Copper-rich nanoscale strengthened steel were carried out at 90?,110? and 150?.The microstructure of the weld seam was acicular ferrite and the microstructure of the heat affected zone were mainly lath martensite,lath bainite,granular bainite tempered martensite and a small amount of ferrite.As the interpass temperature increased,the strength and toughness of the Copper-rich nanoscale strengthened steel rose first and then decreased,the bending performance didn't change much,and the grain size had increased.At 110? interpass temperature,the welded joint had the best comprehensive mechanical properties,and the strength and toughness of the A joint were better than the B joint.Through the studied in this paper,it is found that Copper-rich nanoscale strengthened steel had a low tendency to weld crackings and strong resistance to brittleness transition of welded joints.When performing manual arc welding,A welding material should be used,the heat input is limited to below 15 kJ/cm,and the interpass temperature at about 110?,the welded joints had the best strength and toughness matching,which could effectively guarantee the welding quality.