| The Pb brass often used can be applied to many industries widely, because it has good mechanical and corrosion resistance property.But when the abandoned leaded metals was burn, it will pollute the air.And Pb is a little soluble in water, the leaded products will pollute the water in process of using them.Pb is a kind of very toxic element, it can harm the brain and nervous system and hemopoiesis system. so whether human drink the water or breathe the air which contain lead will give the body a big harm.Based on these reasons, exploiting a lead free easy-cutting brass become more and more important.The classification and wide application of brass was introduced in this paper,and the mechnism of easy-cutting brass was analysised.The Pb granules distribute in Pb brass, when it is cutting, it make the stress focus here, the cutting chips are easy to break, so the Pb brass has good machinability.As the weight percent of Pb contained in Pb brass is usually about1.0%, according to this principle, the Si element is used to substitute for Pb in this experiment and the content of silicon is also nearly1.0%.Meanwhile trace amounts of Ni、Sn、P and rare earth element La are been added to manufactures the lead free easy-cutting Si brass.In order to explain the feasibility of this Si brass, the mechanical property、cutting ability、corrosion property and microstructure were tested and studied.For the mechanical property of the Si brass, the hardness of casting and hot rolling samples was tested at first. It was found that with the increasing content of Si, the hardness of alloy rises.The hardness of hot rolling samples are higher than the casting samples, and the hardness of hot rolling sample which contain1.0%Si could reach252.16HB.Then, the tensile test was processed on the hot rolling samples, the tensile strength and elongation were measured.Then, some alloy rods were prepared to cut in the factory, the machinability can be judged by the the quality of cutting chips.The texture of grain phase was observed under the grain phase microscope after burnishing and polishing the casting and hot rolling samples, it can estimate whether the grain and phase are combined well and what effects of it can make to improve the mechanical property.For the corrosion property of silicon brass, the mechnism of corrosion was introduced at first, and it is known that the corrosion in brass are dezincification which is followed with electrochemical reaction and stress corrosion.Then the dezincification resistance experiments were conducted with casting and hot rolling samples to measure the corrosion depth here to evalute the corrosion resistane ability, and next the corrison property was judged by the average lost weight by taking the artificial seaeater corrosion test.The contents of α phase and β phase in the Si brass were confirmed by observing the appearance and spectrum through SEM and XRD.After scanning the surface, a third phase which contains much Si and Ni was found.The small white granules which appeared under SEM were observed by magnify20000times under the TEM.By making diffraction to them, it was found that the granule was a special phase which containing much P、Si and Ni elements with the scale about400-800nm. The effect of these distributed granules is similar to Pb, it makes the stress focus here when it is cutting, the cutting chips are easy-broken, so it improves the machinability.There are many dislocations in the alloy which was observed under TEM, so they improve the working properties.Because this Si brass has good mechanical property、cutting ability and corrosion property, we could use Si to substitute for Pb to develop the lead free easy-cutting Si brass. |
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