Effect Of Nano-composite Lubricants On The Contact Tube Wear And Anti-rust Property Of Non-copper Coated Solid Wires

Gas-shielded solid wires are often coated with copper as a final surface treatment.Although the copper plating solid wires have excellent electrical conductivity and anti-rust properties,low contact tube wear,there are some prominent problems applied in robot auto-welding:1)Lots of contaminants are generated during the manufacturing of the solid wires,such as waste water,gases and solids;2)Copper fumes are included in the welding fumes;3)Copper layers at the surface of copper plating solid wires are easily peeled off,which can block wire feeding tube,thus they are not suitable for continual welding of automatic robots.Owing to the removal of acid pickling and copper plating process,non-copper coated solid wires with excellent feedability of wires have little pollution on environment,especially for robotic arc welding,therefore they are tendency for the development of gas-shielded solid wires.However,contact tube wear is the bottleneck of industrial application for non-copper coated solid wires.To figure out contact tube wear mechanisms is the key to solve contact tube wear.Consequently,the investigation that the effects of nano-composite lubricants on contact tube wear and anti-rust properties of welding wires for non-copper coated solid wires will provide some guide for solve contact tube wear and intelligent welding of non-copper coated solid wires.Graphite-MoS₂-Fe₂O₃?Fe₃O₄?nano-composite lubricating coatings were prepared on the surfaces of non-copper coated solid wires by a mechanical coating technique in line.The effects of nano-composite lubricants constituents on the wear properties of conatct tube were investigated with robots auto-welding method.The worn morphology of the inner surface of the contact tube and interface compositions were analysed.The results show that the lubricating properties of C-Fe₃O₄ coatings outperform the lubricating properties of C-Fe₂O₃ coatings when the proportioning of graphite and Fe₃O₄?Fe₂O₃?is 1:1.The anti-wear performance of the contact tube is enhanced with an addition of nano-MoS₂.The anti-wear performance of the contact tube is optimum when the content of nano-MoS₂ is 20 wt.%,with a mass loss rate of the contact tube equal to 0.35%,and a wear rate of contact tube inner diameter being equal to 26.1%.Layers of protective lubricating films are formed at the rubbing interfaces of wires against the contact tube by the tribochemical reactions among graphite,MoS₂ and Fe₃O₄?Fe₂O₃?.The films are composed of FeO,MoO₃ and FeMoO₄ whose lubricating properties are outstanding,which avoid the direct contact of the wires against the inner surfaces of the contact tube,thus significantly decreasing contact tube wear.The contact tube temperature during welding was real-time measured by thermocouple.The effects of temperature and heat inputs on the wear properties of contact tube were tested with automatic wire feeder and robots auto-welding method,respectively.The worn morphology of the inner surface of the contact tube and interface compositions were analysed.The results demonstrate that the contact tube temperature for copper plating wire is lower than it for non-copper coated solid wires.The wear rate of the contact tube is improved with increasing the contact tube temperature.The main mechanism of contact tube at 20?is fatigue peeling,while adhesive wear,oxidative wear and abrasive wear are the dominant mechanisms of contact tube at 450?.The wear rate of contact tube during welding is evidently enhanced in comparison with it at 20?and 450?,respectively.The wear rate of contact tube is enhanced with increasing heat inputs.When contact tube is transformed from mild to severe wear,the transition heat input was 9114 J/cm,its wear mechanism are converted from fatigue peeling,oxidative wear and abrasive wear to abrasive wear and arc ablation.The anti-rust properties of self-made welding wires coated with different anti-rust oil were evaluated with different corrosion test methods,such as atmospheric exposure test,constant temperature and humid test,salt spray corrosion test and electrochemical corrosion test.The results illustrate that anti-rust oil of 1#exhibits excellent anti-rust property,followed by anti-rust oil of 3#,while base oil of150N is the worst.The anti-rust property of base oil is strengthened with the addition of appropriate composite rust inhibitors.On the basis of this,a synthetic comparision of non-copper coated solid wires GDMG 50-6N with other solid wires were conducted.The results show that the welding performance and mechanical properties of GDMG 50-6N meet relevant standards,and have excellent rust resistance and stability of arc,wear property of contact tube is better,therefore satisfying the requirements of industrial application.