Lead-Free Free-Cutting Aluminum Brass Alloy And Its Manufacturing Method

Abstract

The present invention provides a lead-free free-cutting aluminum brass alloy and its manufacturing method. The alloy comprises: 57.0˜63.0 wt % Cu, 0.3˜0.7 wt % Al, 0.1˜0.5 wt % Bi, 0.2˜0.4 wt % Sn, 0.1˜0.5 wt % Si, 0.01˜0.15 wt % P, at least two elements selected from the group of 0.01-0.15 wt % Mg, 0.0016-0.0020 wt % B, and 0.001-0.05 wt % rare earth elements and the balance being Zn and unavoidable impurities. The inventive alloy has excellent castability, weldability, cuttability and corrosion resistance. It is suitable for low pressure die casting, gravity casting, horizontal continuous casting, forging and extrusion. Its metal material cost is lower than bismuth brass. It is particularly applicable for components used in drinking water supply systems and other structural components. It is a new environmentally-friendly free-cutting aluminum brass alloy.

Description

RELATED APPLICATION[0001]This application is a continuation-in-part of U.S. application Ser. No. 12 / 643,513, filed Dec. 21, 2009, and claims priority therefrom.FIELD OF THE INVENTION[0002]The present invention generally relates to a lead-free free-cutting aluminum brass alloy, in particular a lead-free free-cutting aluminum brass alloy and its manufacturing method which is applicable in low pressure die castings and forgings.BACKGROUND OF THE INVENTION[0003]Currently, when people search and develop lead-free or low lead free-cutting brass alloys, they typically follow two routes to find the elements which could replace Lead: one route is to select the elements which hardly form solid solutions in Cu and can't form intermetallic compounds with Cu, such as Bi, Se and Te, etc; the other route is to select the elements which will form solid solutions in Cu wherein the solid solubility is reduced with decreasing temperature, so as to form intermetallic compounds with Cu, and with Sb, P, ...

AI Technical Summary

Problems solved by technology

Therefore, such brass alloys cannot be used in the components for drinking water supply systems, such as faucets and valves.

With the increasingly extensive application of bismuth brasses, their negative effects are also increasingly notable, such as susceptibility to hot and cold cracking, poor weldability, the necessity to slowly heat and cool when annealing, etc.

The public casting bismuth brasses, such as C89550 (which comprises 0.6˜1.2 wt % Bi), have high tendencies to experience hot cracking during low pressure die casting, and are not easily welded.

However, antimony is more toxic than lead.

Antimony brass is not suitable for components used in drinking water supply system.

Most of them comprise small amounts of bismuth and the cost of raw material is rather higher.

Aluminum brass has good corrosion resistance, but its cuttability is inadequate.

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