| Metal semi-solid forming combines the advantages of casting and forging,and is suitable for forming various types of precision parts.It can be applied in a wide range of applications and is suitable for a variety of metals.The tin bronze alloy has good wear resistance,corrosion resistance and good comprehensive mechanical properties,and is usually used for manufactur ing bearing bushings,valve switches,worm gears and the like on automobiles and marine equipment.The bushing parts manufactured by the traditional casting process often have defects such as cracks and shrinkage cavities,and the mold loss is large,the processing amount is large in the later stage,and the material utilization rate is not high.The use of semi-solid forming technology to manufacture copper alloy bushing parts can improve material utilization,reduce part defects,and increase mold life.In this paper,the tin bronze alloy shaft parts are taken as the research object.The semi-solid copper alloy slurry is prepared by cold rolling-remelting method,then the sleeve is directly extruded and the sleeve is heat treated.The remelting temperature and heat preservation are mainly studied.The influence of time,annealing temperature and holding time on the microstructure of the bushing.The main research contents and results of this paper are as follows:The extrusion die of the set of parts firstly studied the influence of remelting temperature and holding time on the microstructure and mechanical properties of the semi-solid extrusion during the pulping process,and explored the evolution of the solid-liquid two phase in the semi-solid extrusion process.The mechanism and law showed that with the increase of remelting temperature,the average grain size of semi-solid microstructure first increased and then decreasesd,the liquid phase rate increased,the shape factor decreases first and then increa sed;the mechanical properties of the bushing The tensile strength was gradually reduced,the elongation was gradually increased,and the Brinell hardness first increased and then gradually decreased.With the increase of the holding temperature,the avera ge grain diameter and liquid phase rate increased gradually,and the shape factor also decreased first and then increased.In terms of mechanical properties,the tensile strength of the part gradually decreased with the increase of holding time.The trend,while the elongation rate first increased and then decreased,the Brinell hardness also increased first and then decreased.With the increase of holding time and remelting temperature,the way of tensile fracture of materials changed from brittle fracture to mixed fracture mode of cleavage fracture and ductile fracture.The comprehensive comparison showed that the semi-solid microstructure of the sleeve parts was the most uniform,the shape factor was the lowest,and the comprehensive mechanical properties were good at the remelting temperature of 910 ℃ and the holding time of 15 min.The average grain diameter was 63.56 μm.The shape factor was 1.36,the tensile strength of the part was 368 MPa,the elongation was 4.5%,and the Brinell hardness value was 126 HBW.After the extrusion,the heat treatment experiment was carried out on the bushing parts.The influence of annealing temperature and holding time on the semi-solid microstructure and mechanical properties of the bushing parts was further studied.The results showed that the semi-solid ZCuSn10P1 copper alloy increased with the annealing temperature.The average grain size of the structure gradually increased,the shape factor decreased first and then increased,and the liquid phase rate increased gradually.At the same time,as the annealing temperature increased,the tensile strength and elongation of the part increased first and then decreased.The change trend,Brinell hardness first increased and then decreased;and with the increase of holding time,the average grain size of semi-solid ZCuSn10P1 copper alloy also increasesd gradually,the shape factor decreased first and then decreased,and the liquid phase rate increased continuously.The tensile strength and Brinell hardness of the performance showed a tendency to increase first and then decrease,and the elongation showed a gradual increase.After heat treatment,the elongation and tensile strength of the material were improved to different extents.The fracture mode of the material was mainly mixed fracture,and the prolonged holding time can improve the toughness of the material.The suitable heat treatment process can promote the liquid from solid to solid.Phase diffusion improved sharp corner tissue and improved tissue roundness and uniformity.The suitable annealing temperature was 500 ℃ and the temperature was 120 min.The semi-solid microstructure had the highest roundness and the best mechanical properties.The average grain size of the semi-solid microstructure was 75.24μm.It was 1.26;in terms of mechanical properties,the tensile strength was 423 MPa,the elongation was 6.6%,and the Brinell hardness was 141 HBW.Compared with the unheated,the tensile strength was increased by 13%,the elongation was increased by 46%,and the Brinel l hardness was improved.11.9%.In addition,the influence of heat treatment process on the wear resistance of semi-solid ZCuSn10P1 copper alloy was also analyzed.The results showed that the wear loss rate and friction factor showed a trend of decreasing first and then increasing with the increase of annealing temperature and holding time.At the annealing temperature of 500 ℃ and the holding time of 120 min,the grinding loss rate and friction coefficient were the lowest,respectively 6% and 0.48.The we ar surface was smoother than when it was not heat treated,and the block peeling and furrow were less,and the grinding loss rate was also greatly reduced compared with the case of no heat treatment,which was reduced from 17% in the unheated treatment to 6%,indicating a suitable heat treatment.The process can improve the wear resistance of the semi-solid ZCuSn10P1 copper alloy. |
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