Effect Of Heating Process On Microstructure And Properties Of Copper Alloy After Extrusion

Tin bronze has the high elasticity and abrasion resistance,can be used for processing medium sliding speed and load to withstand friction parts,such as bearings,bushings,turbines and so on.With tin bronze as the raw material processing of the connecting rod bushing has a good comprehensive mechanical properties,high surface hardness,can satisfy the requirement of high speed diesel engine on the connecting rod bushing.But tin bronze in the casting,prone to reverse segregation phenomenon,serious in the casting surface appears white "tin sweat" tumor;the addition of phosphorus can improve copper tin alloy casting performance,improve the liquidity,and effective deoxidization,but the disadvantage is to increase the degree of reverse segregation of the ingot.When tin and phosphorus reach a certain content,Cu3 P and(? + ?)forms a ternary eutectic(? + ? + Cu3P),its melting point is 628 ?.The presence of ternary co-crystals allows the alloy to exhibit hot brittleness.Therefore,tin phosphor bronze has been considered only under the cold processing,but under the cold processing the molding process has many shortcomings,such as alloy high strength,large deformation resistance and fast tool wear,difficult and unsafe operation.So,the study of high phosphorus content of tin phosphor bronze hot processing technology is particularly necessary.In this paper,tin bronze QSn7-0.2 as the research object,using backward extrusion molding technology to study the deformation before the material heating temperature,heating method and holding time and other technical parameters on the impact of material after forming the impact.The effects of the heating process on the microstructure and properties of the microstructures were investigated by means of metallographic microscope(OM),BH tester,tensile tester,X-ray diffraction(XRD)and scanning electron microscopy(SEM).The main contents and results of this paper are as follows:(1)Effect of different heating temperature on the microstructure and properties of tin bronze after extrusion,this experimental results show that After heating to 720?,the microstructure of the blank is best(especially the reduction of area ?),So as to provide the best blank for the next spinning process;And the causes of extrusion cracking at 780 ? were analyzed:In the heated to 780 ? billet surface edge of the "tin sweat" emerge,The end face of the extruded cup is then cracked in the " tin sweat " zone,It found that their organizations were analyzed in this area were cast microstructure of dendrites,Intra-granular segregation is obvious,And the ternary eutectic structure(? + ? + Cu3P)is found.The existence of the ternary eutectic causes the hot brittleness of the alloy,which is the main reason for the crack in the hot extrusion of tin bronze cup.(2)The effect of different heating methods on the microstructure and properties of tin bronze after extrusion the experimental results show that under the same heating temperature,the induction heating speed is fast,the degree of oxidation of the material is small,the thermal permeability is good and the extrusion is The microstructures of the cups are ?-single-phase paraxial twin recrystallization,occurrence fully dynamic recrystallization.The cup-shaped tissues with the furnace heating and the temperature heating are fibrous,banded and small and dynamic recrystallization,and there are a large number of slip bands.At the same time,due to the different heating methods,resulting in the actual heating temperature of the material and equipment display temperature gap,thus affecting the degree of dynamic recrystallization.(3)The effect of different holding time on the microstructure and properties of tin bronze after extrusion the experimental results show that under the same heating temperature,the strength and hardness of the cup are reduced and the plasticity increases with the increase of the holding time,And the ratio of dynamic recovery and dynamic recrystallization of the material increases.the ratio of dynamic recovery and dynamic recrystallization of the material increases.This is due to the heating equipment to make the material heating the actual temperature than the display temperature is low,resulting in the holding process has become the material heating process,but also to improve the material heat permeability process,affecting the dynamic recrystallization.For the material after induction heating without direct extrusion,the microstructure of the material is single-phase paraxial twin recrystallization,occurrence fully dynamic recrystallization.Whether it is from the organizational performance or heating process must be fine,so it is the best spinning process blank.