| Road milling machine is the primary equipment for the construction and maintenance of asphalt pavement and cement pavement road.It is mainly used for the excavation and renovation of asphalt concrete and cement concrete surface of expressway,national highway,airport,large square,parking lot and so on.The milling machine is made up of the lifting leg and the base,and it is integrated with the walking system.The operation is subject to high load and the force is very complicated,thus ensuring the welding quality between the leg and the base and obtaining high quality welded joints with high strength,plasticity,good toughness milling machine are the key of processing a milling machine leg.In this paper,the optimization of the welding process of the 27SiMn alloy steel and the base Q345 steel was carried out based on the actual situation of the production and the control of the production site is improved.Research has shown that:(1)By opening a V groove on the 27SiMn alloy legs,and a 7mm-thick parallel transition on the second layer,the amount of welding can be reduced and the quality requirements can be met.The quality of the weld obtained by preheating is better than that of normal temperature weld,with 230-280 ? as its suitable preheating temperature,the ideal welding microstructure can be obtained.The excellent performance lies in the tensile and impact performance and so on.(2)Semi-automatic gas shielded welding can meet the welding requirements of this work piece.The protection gas is made of CO2(20%)+ Ar(80%)mixed gas.The optimum welding parameters are as follows:welding current:250-280A,welding voltage:28-29V,protection gas flow:15-181/min,welding wire speed:200-240mm/min,post weld temperature:250-300 ?,insulation for 2.5 hours.(3)27SiMn special alloy material welding production site key quality control points include:the test leg sets and legs of the material composition,samples of each batch of leg and leg sets sent to do the composition analysis and other important performance indicators and welding quality assurance 100%full inspection.Strict control following items but not limited to them,such as preheating temperature before welding,welding current,voltage,wire feed speed,protection of gas flow and composition and so on,especially in the winter when the low temperature post weld temperature is particularly important.(4)By dry the wire and protect the gas dehydration before welding and other measures to reduce the risk of Hydrogen crisp of the weld;Group pairs after spot welding with a three-coordinate instrument accurate and rapid positioning;preheated can easily and accurately measure preheating temperature using hand-held infrared thermometer;control welding staff functional level,must be more than intermediate to welding;to ensure the quality of welding,the entire welding process must be completed within 0.5 hours,high operating efficiency;In addition,in order to develop the potential application and accumulation data of the product,In this paper,the temperature field and stress field of 27SiMn steel and 45 steel welding are simulated.The temperature field and stress field of welding heat affected zone under different welding heat input conditions are obtained.For 27SiMn steel and 45 steel welding process to provide reference. |
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