Research On The Effect Of Pulse TIG Welding On Explosive Welding Interface In Titanium/Steel Composite Structure

Since the low cost and excellent corrosion resistance of titanium/steel composite structure,it has been more and more used in modern industry.However,the complex service environment makes the reliability requirements of titanium/steel joints increased.This puts forward higher requirements for the reliability of titanium/steel joints.In this paper,pulse TIG welding of TA2 titanium plate and TA2/Cr Ni3Mo V explosive welding composite plate was performed.The microstructure and properties of the titanium/steel explosive bonded interface under different welding process parameters were studied.The temperature field of welding process was monitored by thermocouple.In addition,temperature and stress fields at the explosive bonded interface during the welding process were calculated by finite element analysis software,which provided a reference for the actual welding process.The effects of different welding thermal cycles on the microstructure and mechanical properties of the titanium/steel explosive welding interface were studied by the thermal simulation,and the mechanism of the transition of the interface microstructure was revealed.The titanium plate and the titanium/steel explosive welding composite plate were grooved fillet welding by pulse TIG welding.With the increase of peak current,the thickness of continuous TiC layer at the Ti/steel explosive bonded interface increases slightly at first,and then partially dissolves to form a semi-continuous structure.A continuous?-Ti layer appeared at the peak current of pulse welding was 180A.When the peak current of pulse welding was 300A,the continuous TiC at the interface was dissolved and distributed at a semi-continuous shape.At the same time,the thickness of the Fe-Ti intermetallic compounds at the interface increased rapidly while the interface shear strength dropped sharply to 263.2MPa.The temperature field at the titanium/steel explosive bonded interface was calculated by finite element analysis software.The results show that the temperature at the interface increased with the pulse peak current.When the pulse peak current was 300A,the peak temperature of welding thermal cycle at the Ti/steel explosion welding interface was up to 969?.The transformation mechanism of the microstructure and mechanical properties of the titanium/steel explosive bonded interface under different welding thermal cycles was investigated.The microstructure results were elucidated that there was no obvious variation in the titanium/steel explosive bonded interface when the peak temperature of the welding thermal cycle is 692?.When the peak temperature of the welding thermal cycle is 873?,a continuous?-Ti layer appears at the interface and the thickness of original TiC increased.When the peak temperature of the welding thermal cycle is 987?,the TiC layer at the interface was partially dissolved.When the peak temperature of the welding thermal cycle is 1081?,the interface melted.When the peak temperature of the welding thermal cycle is 1192?,Fe Ti+?-Ti eutectic and cracks were determined at the Ti/steel explosive bonded interface.Enhancement in the peak temperature of the welding thermal cycle to 1283?,reactions such as eutectic and peritectic will occur at the interface,which results in a great number of Fe₂Ti and Fe Ti intermetallic compounds and microcracks occurred.The tensile and shear tests indicated that tensile and shear strength of Ti/steel explosive bonded interface decreased with increasing peak temperature of the welding thermal cycle.When the peak temperature of the welding thermal cycle is1192?,the tensile strength and shear strength of the interface were decreased to the lowest points,which were 59.63MPa and 58.09MPa,respectively.The effect of the structure of the interface on the mechanical properties of the interface was analyzed.The results demonstrate that the nano-hardness of Fe₂Ti is12.23GPa,which is 1.24 and 2.57 times that of Fe Ti and?-Fe,respectively.Inaddition,the brittleness of Fe₂Ti was extremely huge,which results in cracks during nano-indentation loading.During the cooling process,due to the combined effects of stress concentration and self-brittleness,a large number of microcracks were generated at the phase boundary of Fe₂Ti and Fe Ti,which results in the interfacial shear and tensile strength drop dramatically.