Preparation And Properties Of Lead-free Antimony Brass Study

Lead brass alloys are applied in various fields,such as household electrical appliances,electric telecommunications,potable water system, toys,automotives,mechanical manufactures and device manufactures, due to its excellent mechanical properties and cutting properties,but Pb is a kind of element harmful to environment and human being,so it will bring enormous social benefit and economic benefit to replace Pb using innocuous elements and reach its cutting properties.Sb is used to replace Pb in this work and rare earth elements and Ti is added to refine the grains.Orthogonal experiment is used to optimize the contents of alloy components,and a new kind of nonleaded Sb-brass is develop;after rational annealing and rolling schedule,the Sb-brass broads are prepared successfully.The test methods of DTA,XRD,SEM, TEM and EDS were used.The influence of different contents Sb on the microstructures and properties was studied,and tested the tensile-strength, the resistance of dezincification and the cutting property.The rolling schedule and the intermediate phases were studied,and the mechanics of Sb-brass was discussed.The conclusions are as followings:(1)The content of Sb is the major factor to affect the systhesis properties of alloys,the second is Ce and the last is Ti.The tensile strength was reduced and the depth of dezincifying layer was reduced with the raising of Sb,especially when the content of Sb was over 1.2%, the tensile-strength reduces rapidly;but when it was less than 0.5%,the depth reaches 445μm,it is worse than HPb59-1;The cutting property of alloy just depend on the content of Sb,the more the better,and the reasonable contents of alloy is(wt%):57-59Cu,0.SSb,0.4Ce,0.3Ti;(2)The Sb mainly exists as intermetallics in alloy,and it distributed onαphase andβphase in ingots and on phase boundary betweenαphase andβphase after rolling;The fractures of the rolling alloy is ductile and after annealing is intercrystalline cracking;The second phases in alloys are rich in Cu,and it can regard as Cu₂Sb phase after the analysis of DTA, the calculation of thermodynamics and the calibration of diffraction spots. Its structure can describe as simple tetragonal,and the lattice parameter is a=b=0.3990nm,c=0.6020nm,belonging P4/nmm space group.(3)After the annealing of 750℃about lh,the beginning rolling temperature was not less than 720℃and the finishing temperature was not less than 600℃,and using 8 passes.The max reduction in pass should be less than 40%,When the total working rates reaches 70%,it should take interprocess at 750℃about 30min to reduce the work-hardening, and it can improve the ultimate rolling properties through controlling the contents of Cu and Zn,also the quantity ofβphase,and avoiding the cracks between rolling;(4)The tensile strength,yield strength and elongation percentage of Sb-brass is 461.7MPa,213.3MPa and 15.67%respectively.The resistance of corrosion in 3.5%NaCl solution is good,and it shows excellent dezincification corrosion resistance and the average depth of longitudinal section and lateral section is about 295.4μm 214.7μm respectively;The cuttings of unleaded Sb-brass were tiny,and its inner surface was smooth, the cutting course of unleaded Sb-brass was stable and fluctuation was slightly,the cutting surface was smooth and the roughness of surface was very small,we can consider it is better than HPb59-1 basically,and it can take the place of HPb59-1;(5)The mainly cutting mechanics of Sb-brass is:there were small spaces between the second phases and the base,it can considered that there were plenty of tiny holes in alloy and those hole were filled with the frangible but not hard Cu₂Sb phases,and the existence of the second phase will cut off the continuous of alloy,it will become the stress raiser and result the notch effect,it is easy to form the stress concentration and the reproduction and movement of dislocations.The dislocations diffuse into the inner of alloy under the force of shear stress of cutting,and it will form a new cutting face,then the cutting lay occurrs plastic yield,and the cuttings fall down along the rake face.