Lead-free free-cutting phosphorous brass alloy and its manufacturing method

Abstract

Considering the solid solubility of P in the matrix of copper will be decreased rapidly with the temperature decrease and form the brittle intermetallic compounds Cu 3 P with Cu, the present invention elects P as one of the main elements for ensuring the excellent cuttability of the invented alloy. The lead-free free-cutting phosphorous brass alloy comprises: Cu, Zn, 0.4 to 1.6 wt % P. and other elements in the amount of 0.005 to 0.6 wt %, which comprise at least two elments selected from the group consisting of Al, Si, Sb, Sn, Re, Ti and B, and the balance being unavoidable impurities. The phosphorous brass alloy contains a combined wt % of Cu and Zn of between 97.0 wt % and 99.5 wt %, within which the content of Zn is above 35 wt %. The method of manufacturing the alloy is also disclosed. The invented alloy has excellent cuttability, castability, hot and cold workability, dezincification corrosion resistance, mechanical properties and weldability. The phosphorous brass alloy is applicable in spare parts, forging and castings that require cutting, and particularly in forging and castings for low pressure die casting that requires cutting, grinding, welding and electroplating. The phosphorous brass alloy may be used for faucets, valves and bushings of water supply systems, and for bar and wire materials that require high corrosion resistance and compactness.

1 . A lead-free [and bismuth-free] free-cutting phosphorous brass alloy comprising: zinc, in an amount exceeding 35 wt%; copper, in an amount such that the amount of zinc and copper totals between 97.0 wt% and 99.5 wt%; [0.4] in excess of 0.5% to 1.6 wt% P; and other elements in an amount between 0.005 and 0.6 wt%, which comprise at least two elements selected from the group consisting of Al, Si, Sb, Sn, Re, Ti and B; and the balance being unavoidable impurities. 
   
   
       2 . The lead-free free-cutting phosphorous brass alloy of  claim 1 , wherein the amount of P is between 0.5 and 1.35 wt %. 
   
   
       3 . The lead-free free-cutting phosphorous brass alloy of  claim 2 , wherein the amount of P is between 0.5 and 0.8 wt %. 
   
   
       4 . The lead-free free-cutting phosphorous brass alloy of  claim 1 , wherein the other elements are selected from the group consisting of Al, Si, Sb, Ti or B. 
   
   
       5 . The lead-free free-cutting phosphorous brass alloy of  claim 1 , wherein Pb and Fe as the unavoidable impurities, the content of Pb is less than 0.02 wt % and the content of Fe is less than 0.05 wt %. 
   
   
       6 . A manufacturing method of the lead-free free-cutting phosphorous brass alloy of  claim 1 , wherein when a melt of the alloy reaches a temperature of 980 to 1000 degrees Celsius, the melt is poured into ingot molds to form ingots for further processing. 
   
   
       7 . A manufacturing method of the lead-free free-cutting phosphorous brass alloy of  claim 1 , wherein ingots of the alloy are extruded at a temperature among 550 to 700 degrees Celsius for about 1 hour with an elongation coefficient of greater than 30. 
   
   
       8 . A manufacturing method of the lead-free free-cutting phosphorous brass alloy of  claim 1 , wherein ingots of the alloy are forged at a temperature among 570 to 680 degrees Celsius. 
   
   
       9 . A manufacturing method of the lead-free free-cutting phosphorous brass alloy of  claim 1 , wherein ingots of the alloy are remelted and cast at a temperature among 980 to 1010 degrees Celsius at a pressure of 0.3 to 0.5 Mpa.