A Study On Lining Reinforcement Technology And Wear Resistant Properties Of Pump Pipe Elbow

At present, the concrete pump truck is widely used in construction. The inner wall of low carbon steel elbow installed in concrete conveying pipeline initial site is abrasive worn most grievously by slurry and sand which is prone to crack and be worn out. Two kinds of inner lining reinforcement technology for low carbon steel bend pipe of concrete pump truck was explored in this paper. High chromium cast iron was used as the bent pipe lining material.The reasonable heat treatment process was utilized to heighten its high abrasion resistance.WC coating was used as the other lining material for the low carbon steel elbow, that is, the coating was sprayed on the inner wall of the low carbon steel pipe to improve the wear resistance. It was made comparative analysis that the wear mechanism of high chromium cast iron and WC coating in the two body and three body abrasive wear.The practicability of the two kinds of inner lining strengthening technology was compared. The main conclusions of the thesis were as follows:1.With the elevation of quenching temperature, the hardness of high chromium cast iron increased first and then decreased, the impact toughness decreased first and then increased.With low temperature quenching, the driving force of the element diffusion was weak causing that the number and the size of carbide were large. With too high temperature quenching, dissolution of carbide was excessive so that the austenite was more stable and the amount of retained austenite was enhanced. When the tempering temperature was less than 400?, the microstructure of high chromium cast iron almost unchanged. A large number of martensite decomposition and carbide coarsening was emerged,When the tempering temperature is higher than 400?.2.Two different groups of four factors and three levels of orthogonal experiment method were compared. The optimum heat treatment process for the high chromium cast iron to obtain the best comprehensive performance was 920? for 105min with the furnace cooling to 860 ?+water quenching+200? for 2h tempering, leading that its impact toughness was 3.74J/cm2, The abrasion loss of three body wear was 0.21g3.In the three body abrasive wear with SiO2 as abrasive, the high chromium cast iron and WC coating as low carbon steel lining materials can obviously improve the wear resistance of elbow. The support ability of the matrix to carbide and the volume fraction of carbide were the important factors to influence the wear resistance. The wear resistance of high chromium cast iron as cast condition was 2.48 times higher of low carbon steel.After optimum heat treatment, the wear resistance of high chromium cast iron was 11.32 times higher of low carbon steel.The heat treatment process can significantly improve the wear resistance of high chromium cast iron.The wear resistance of WC Coating was 14.75 times higher of low carbon steel. Which shown that the wear resistance of WC coating was better than that of high chromium cast iron, but the wear resistance of them was similar.4.In the two body abrasive wear with SiC as abrasive, the high chromium cast iron and WC coating as low carbon steel lining materials can obviously improve the wear resistance of elbow. The wear resistance of high chromium cast iron as cast condition was 2.54 times higher of low carbon steel.After optimum heat treatment, the wear resistance of high chromium cast iron was 5.27 times higher of low carbon steel.Because carbide can not effectively resist abrasive wear, heat treatment process for high chromium cast iron to improve the wear resistance was not obvious.The wear resistance of WC Coating was 6.18 times higher of low carbon steel. Which shown that the wear resistance of WC coating was better than that of high chromium cast iron, but the wear resistance of them was similar.5. Although the WC coating showed better wear resistance, compared with high chromium cast iron, the improvement of the relative wear resistance was not significant.The combination between the coating and the matrix was mechanical.In the working environment with impact force, the WC coating was easy to fall off from the surface of the matrix so that the coating lost the ability to protect the matrix. what is more,the technology of spray endoporus was complicated so that the coating thickness is not uniform and the deposition rate is not high. Therefore,the WC coating need more improvement.Choosing high chromium cast iron as lining material was a reasonable and economical way to strengthen the inner lining of pump truck.