Studies On New Thermite Welding Technology And Engineering Application

People have to operate an emergency welding without electric power in naturedisaster or battle fields. However, all the existed welding method hardly meet thesimple、efficient requirements for emergency repair. This paper presents a novel methodof thermite welding, which combined SHS technology with manual welding. Ahand-operated portable welding can be conveniently realized by using thermite weldingwithout any outside power and auxiliary equipment.Rapid separation of aluminum oxide and molten metal production could berealized by Self-propagating slagging reaction technology. The influence of rawmaterials particle size and milling process were discussed. Finally a controlled thermitereaction and weld formation were achieved.Al/Fe₂O₃and Al/CuO system were selected as the main exothermic reaction inthermite welding. The formability and microstructure of weld bead were studied. Theinfluence of alloying elements on weld microstructure and property were discussed aswell. Results showed the weld performance for Al/Fe₂O₃system is bad and weldabilitywas deteriorated sharply when adding alloying elements C. While Al/CuO system has abetter weld performance and the microstructure and property of weld was improved byadding Al/NiO system.Effect of thermite burning rate and temperature on microstructure and mechanicalproperties of weld joints was studied in Al/CuO、NiO system. The thermite reaction wasadjusted by varying addition of diluent. The causes of solidification cracking duringthermite weld process were discussed and the effect of Ni and Fe content on formingsolidification cracking was studied. Results showed a fine microstructure with fewshrinkage pore or micro-crack was obtained at0.37cm/s burning rate,1918℃with4wt.%wollastonite addition. The Ni and Fe contents were key reasons in formingsolidification cracking, when their levels were controlled by less then10wt.%, it couldbe able to eliminate the solidification cracking. The tensile properties with424MPaultimate tensile strength and10.4%uniform elongation were obtained after strictcontrolling the welding process. The properties of weld fully meet the needs ofemergency welding. A simple and novel method to prepare ceramic particulate reinforced MMCcoatings were realized via thermite welding technology. Results showed in situsynthesized TiC particles were fine with an average size of <10μm and uniformlydistributed in the metal matrix.