Study On Preparation Technology And Properties Of Double-layer Composite Ceramic Backing For Welding

Ceramic backing welding has been widely used in shipbuilding,pipeline transportation,pressure vessel manufacturing,bridge and other steel structures manufacturing industry.In view of the fact that there are only single layer ceramic backings in the market,and the sintering temperature of the backing is high?1300?¹800??.Long firing cycle?more than24 hours?,high energy consumption,low density and high moisture absorption rate.In this paper,a manufacturing method of double layer composite ceramic backing is developed.Gansu laterite and Al₂O₃ were used as the main body frame of the backing formulation,and Li₂CO₃,3Y-ZrO₂ was used as the additive of the upper backing.Orthogonal screening experiment was used to explore the content of laterite and other ingredients in the formula and analyze the function of each raw material.The preparation process was optimized from raw material treatment,mixing method,blank pressing,drying and firing.Through the inspection of appearance,water absorption,flexural strength and compressive strength,the rationality of the selected backing formula and manufacturing process was analyzed and evaluated.The ceramic backing group with excellent mechanical properties was selected for the one-side welding experiment of CO₂ gas protection.Through the observation and analysis of the back weld formation,weld structure and mechanical performance experiment,the influence rule of the backing on the weld performance was analyzed,and the best formula of the two-layer ceramic backing was selected.The results show that:The highest sintering temperature of the 1013A₄E₁ double-layer ceramic backing is 1250?,the sintering time is about 6 hours,sintering effect and welding forming effect are the best.This group of backing formula is?up A4?Laterite78.86wt%+Al₂O₃16.45wt%+Na₃AlF₆3.69wt%+Li₂CO₃1wt%,?down E1?Laterite 79.86wt%+Al₂O₃ 16.45wt%+Na₃AlF₆ 3.69wt%?Gansu laterite can not only bear the ridge raw material in the ceramic backing formula,but also can take part in the flux raw material.The addition of1%3Y-ZrO₂ and Li₂CO₃ in the surface layer formula can effectively reduce the sintering temperature and sintering time of the ceramic backing.Moreover,the density,strength can be increased to give backing a good mechanical property.Preparation process of double-layer ceramic backing based on laterite:pre-sintering raw materials,pre-treating the mixed powder,dispersing agglomeration with ultrasonic waves,drying the mixed suspension,grinding the grinding powder,and mixing the mixer material.The dry pressing method presses the blank of the backing so that the water content of the powder before pressing is 6wt%,and the double-side is slowly and evenly pressurized,and the blank is taken out after being kept for a period of time,according to 80??5h??100??5h??40??14h??150??5h??200??5h?drying.Non-pressure sintering was carried out in batches,and different sintering temperature and sintering duration were set according to the characteristics of backing composition of each group.After firing,the backing was cooled by the furnace until taken out at room temperature.At 1175?,the firing temperature was insufficient for all the backing groups,the backing was substantially fired,the slag phenomenon occurs,and the internal structure was loose.The excessive firing temperature caused a large melt deformation of the partial liner group between 1225?and 1250?.Ceramic backing can not only play the role of single welding and double forming,but also has good forming effect.In addition,thermal insulation can be carried out on the weld zone and the heat-affected zone,so as to slow down the cooling speed of the weld zone and the heat-affected zone,refine the grain,reduce the hardness of the weld zone and the heat-affected zone,and improve the fracture toughness.In this paper,a new type of double layer composite ceramic backing is developed,which optimizes the process flow of ceramic backing preparation,provides technical support and help for the preparation and application of high-performance ceramic liner.Also provides new ideas for the development of welding technology and the innovation of ceramic backing industry.