Cast Bronze

What Is Cast Bronze?

Cast bronze is bronze used to produce castings. Bronze castings are widely used in machinery manufacturing, ships, automobiles, construction and other industrial sectors, forming a cast bronze series in heavy non-ferrous metal materials. Commonly used cast bronzes are tin bronze, lead bronze, manganese bronze and aluminum bronze.

Name: cast bronze
Definition: Bronze used to produce castings
Subject: Metallurgical Engineering
Classification: tin bronze, Wuxi bronze
Application: machinery manufacturing, ships, automobiles, construction, etc.

Introduction

Cast bronze originally only referred to tin bronze. Later, due to the adoption of various alloying elements, new types of bronzes other than tin bronze appeared, such as aluminum bronze, silicon bronze, manganese bronze, chromium bronze, beryllium bronze and lead bronze.

Cast tin bronze

The volume shrinkage of Cu-Sn alloy is very small (the linear shrinkage rate is 1.45% ~ 1.5%), and it is easy to produce complex castings with accurate dimensions and crafts with clear patterns. Casting tin bronze generally adds elements such as zinc, lead, and phosphorus. Phosphates have high hardness, wear resistance, and good abrasive properties. In wear-resistant tin bronze, the phosphorus content can be as high as 1.2%. Zinc can improve the fluidity of the alloy and reduce the anti-segregation tendency of tin bronze. Lead significantly improves the wear resistance and machinability of the alloy. Cast tin bronze is used as wear-resistant and corrosion-resistant parts.

(1) Tin phosphor bronze. Phosphorus is a good deoxidizer for copper alloys, which can increase the fluidity of the alloy, improve the process and mechanical properties of tin bronze, but increase the degree of reverse segregation. The ultimate solubility of phosphorus in tin bronze is 0.15%. When it is too much, α+δ+Cu3P ternary eutectic will be formed, with a melting point of 628℃. It is easy to produce hot brittleness during hot rolling and can only be cold worked. Therefore, the phosphorus content in the deformed tin bronze should not be greater than 0.5%, and the phosphorus should be less than 0.25% during hot working.

Phosphorus-containing tin bronze is a well-known elastic material. During processing, it is necessary to control the grain size before cold working and low temperature annealing after processing. The strength, elastic modulus and fatigue strength of fine-grain processed materials are higher than those of coarse-grain processed materials, but the plasticity is lower. The cold-worked material is annealed at a low temperature of 200-260°C for 1 to 2 hours to produce an annealing hardening effect, which can further improve the strength, plasticity, elastic limit and elastic modulus of the product, and increase the stability of elasticity.

(2) Tin-zinc bronze. A large amount of zinc is dissolved in the copper-tin alloy, and the amount of zinc added in the wrought tin bronze is generally not more than 4%. Zinc can improve the fluidity of the alloy, narrow the crystallization temperature range, and reduce reverse segregation.

(3) Tin-zinc-lead bronze. Lead is actually insoluble in copper-tin alloys. It is distributed among the dendrites as single-phase, black inclusions. The distribution of lead in the ingot is not easy to be uniform, usually adding a small amount of nickel can improve its distribution and refine the structure. Lead reduces the friction coefficient of tin bronze, improves wear resistance and machinability, but slightly reduces mechanical properties. 3% to 5% of zinc is often added to the copper-tin-lead alloy to further improve the mechanical properties. Adding 0.02%～0.1% zirconium or 0.02%～0.1% boron, especially adding 0.02%～0.2% rare earth elements can refine the lead particles and make them evenly distributed, so as to improve the structure, casting and mechanical properties of lead-containing tin bronze.

Wuxi Bronze

Casting lead bronze has high mechanical properties, corrosion resistance, wear resistance, good fluidity, and can cast dense castings.

Casting manganese bronze is generally added with aluminum, iron, nickel and other elements, which are corrosion-resistant and heat-resistant, and are suitable for making high-temperature parts.

Cast aluminum bronze is generally added with iron, manganese, nickel and other elements, which is suitable for making high-strength and corrosion-resistant parts.

The chemical composition and use of commonly used cast bronze

See the table for the chemical composition and use of cast bronze of commonly used grades in China.