Effect Of Mg-Ca Alloy On Removal Lead From Lead-brass

Leaded brass has good free-cutting, mechanical properties and corrosion resistance. Ithas been applied in various fields. However, Lead is toxic element, which hazards to humanhealth and environment. For this study is necessary to develop a new technology of leadremoval from leaded brass, promote leaded brass scrap recycling effectively.This paper was experimental research on the effect of Mg-Ca on lead removal fromleaded brass scrap (Contains3.7Wt.%Pb), guiding with simulation results of FactSagesoftware, and using optical microscope (OM), scanning electron microscope (SEM),transmission electron microscopy (TEM) and energy spectrum analysis (EDS) and X-raydiffraction analysis (XRD).⑴Theoretical analysis and FactSage simulation calculation showed that: Leaded brasshad formed the solid Ca-Pb compounds of high melting point and low density with adding theMg-Ca alloy. It could react with flocculant to form floating composite slag. So it couldachieve the purpose to remove lead. With the addition of Mg-Ca alloy, the percent of Pbremoval from leaded brass was increased. But with the increase of the holding temperature,the percent of Pb removal from leaded brass was changed decreasing. The result wasconsistent with the actual melting experiment: Add4Wt.%Mg-Ca alloy with850℃heatpreservation, the percent of Pb removal was67.3%. So with4Wt.%Mg-Ca alloy addition anddifferent holding temperature (830,840,850,860,870℃), The percent of Pb removal was69.5%with840℃holding temperature. Comprehensive experiment showed that: add4Wt.%Mg-Ca alloy in the840℃holding10minutes, the percent of Pb removal was72.7%.⑵The percent of Pb removal was77.3%with using secondary process of adding3Wt.%Mg-Ca alloy and1Wt.%Mg-Ca alloy. And the Pb content of alloy dropped to0.84Wt.%. Itshowed that secondary process technology of lead removal was efficient than one singleprocess.⑶In the early melting, with the increase of Ca-Mg alloy, β phase of alloy was increased.After adding flocculant to holding, due to the melting time extended, the loss amount of Znwas increased, α phase of alloy was increased. So the content of Cu was increased, and thealloy electric conductivity was increased. Because the effect of Pb removal was remarkablewith4Wt.%Mg-Ca in840℃holding, the alloy conductivity Rose to19.2%IACS and brinellhardness was HB162. Due to the content of Mg was increased, Alloy grain organization shape was become rounded, Add4Wt.%Mg-Ca, the factor of grain shape was best with0.79.⑷With Calculation of elastic constants of compounds, the structure of Ca-Pb compoundswas stable formed with Leaded brass and Mg-Ca alloy. It was calculated that Ca2Pb, Ca5Pb3,Mg2Pb was brittle and CaPb, CaPb3, Cu2Mgwas plastic. After process of moving lead, theresidual metal compounds in alloy had a similar role as free lead in the process of cutting. Soit achieved to remove Pb form lead-brass and got the regeneration of free-cutting nonleadedbrass.