| The blast furnace tuyere is the key components of smelting blast furnace, which have the harsh service condition, and in front of it is scoured by 1500℃of liquid slag iron and high-speed circular motion hot material and strong oxidation draught cause tuyere failure. According to the statistics of domestic blast furnace tuyere average life expectancy is only 150 days, therefore, improve tuyere surface wear-resisting performance and the service life of outlets can effectively guarantee the normal operation of the blast furnace,which has tremendous economic and engineering application value.The blast furnace tuyere is in the blast furnace so it is need tuyere material has good thermal conductivity,and under normal temperature red copper thermal conductivity is carbon steel nine times, therefore, the blast furnace tuyere material selection copper cannot be replace by other common metal.Copper wear-resisting restricted using life of the tuyere,so it is affected smelting quality and increased smelting costs and through welding wear-resistant materials to the surface of the copper substrate can solve the problem that copper matrix is not wear-resisting, also do not affect its thermal capacity.It is difficult to heat the part of the weldde copper to the temperature that can melt it because of its high heat conductivity. Due to the existence of impurities in the copper,it is easily to form the eutectic objects during the welding process and it is formed cracks by the welding stress.But the Plasma Transferred Arc can solve these defects.This topic aim at the common problem in engineering that tuyere wear failure. Strengthened the surface of the blast furnace tuyere by using the PTA process can improve its wear resistance and service life.By improving plasma welding equipment selling in the market can increase welding power and make the maximum current of transfer arc reach to 500A. Adopting advanced PLC control system and touch human-machine interface for operation interface, effectively improve the whole spray welding process reliability, stability and precision.Using orthogonal experimental method optimizes technological parameters of the plasma welded Ni matrix wear-resisting layer on the surface of the Cu matrix.The evaluation standard which is based on the combination of wear-resisting layer and the forming quality get that the main influence factors are preheating temperature, transfer arc current, send powder quantity and spray welding speed. Through experiment we determined the best preheating temperature is 500～600℃. And Through orthogonal experiment we get the spray-welding technique parameters which is optimized are those transfer arc current is 200A, spray welding speed is 64.6 mm/min, the speed of sending powder is 58.4 g/min. Using the optimized spray-welding technique parameters, The result of this paper shows the wear-resistant layer and the copper substrate can be well integrated as a metallurgical bond with dilution rate of only 6%. Moreover, the wear-resistant layer appears a tiny microstructure of feature as dendritic crystal with dispersed hard phase. Main elements contain y-phase solid solution,Cr23C6, Ni3Fe, Cr7C3 and a few amount of boride. Carbonide and boride contribute the average micro hardness of 364 HV to the wear-resistant layer,7 times higher than the one of normal copper substrate (46.4 HV). High temperature wear-resistant increased by nearly 3 times.Optimization spray-welding technique parameters:the best preheating temperature is 500-600℃, transferred arc current is 500A, the speed of sending powder is 79.7g/min,turntable speed is 1.3r/min.The Ni matrix wear-resisting layer which is successfully equiped on the blast furnace tuyere is laid the foundation to the engineering application that is used on the blast furnace tuyere by plasma spray welding technology. |
PDF Full Text Request