Tin Bronze

Tin Bronze

Bronze with tin as the main alloying element. The tin content is generally between 3% and 14%, and it is mainly used to make elastic components and wear-resistant parts. The tin content of deformed tin bronze does not exceed 8%, and sometimes phosphorus, lead, zinc and other elements are added. Phosphorus is a good deoxidizer and can also improve fluidity and wear resistance. Adding lead to tin bronze can improve machinability and wear resistance, and adding zinc can improve casting performance. This alloy has high mechanical properties, anti-friction properties and corrosion resistance, is easy to cut, has good brazing and welding properties, has a small shrinkage coefficient, and is non-magnetic. Bronze bushings, shaft sleeves, anti-magnetic components and other coatings can be prepared by wire flame spraying and arc spraying. The size specifications are Ф1.6mm and Ф2.3mm. It has high strength, corrosion resistance and excellent casting properties, and has been widely used in various industrial sectors for a long time.

Tin-phosphorus bronze:
Phosphorus is a good deoxidizer for copper alloys. It can increase the fluidity of the alloy and improve the process and mechanical properties of tin bronze, but it increases the degree of reverse segregation.
The limit solubility of phosphorus in tin bronze is 0.15%. When it is too much, it will form a+δ+Cu3P ternary eutectic with a melting point of 628℃. It is easy to produce hot brittleness during hot rolling and can only be cold processed. Therefore, the phosphorus content in deformed tin bronze should not be greater than 0.5%, and during hot processing, phosphorus should be less than 0.25%.
Phosphorus-containing tin bronze is a well-known elastic material. During processing, it is necessary to control the grain size before cold processing and low-temperature annealing after processing. The strength, elastic modulus and fatigue strength of fine-grained processed materials are higher than those of coarse-grained processed materials, but the plasticity is lower. Cold-processed materials are annealed at 200-260℃ for 1-2h to produce annealing hardening effect, which can further improve the strength, plasticity, elastic limit and elastic modulus of the products and increase the stability of elasticity.
There are 4 grades of phosphorus-containing tin bronze that are now included in China's national standards.
Among them, QSn6.5-0.1 alloy is mainly used to make elastic elements, especially spring contact pieces with good electrical conductivity, wear-resistant parts and anti-magnetic elements in instruments and meters, etc.;
Qsn6.5-0.4 alloy is mainly used to make metal mesh in industries such as papermaking, chemical industry and food, and is also used to make wear-resistant and spring parts;
QSn7-0.2 alloy is used for parts that bear friction under medium load and sliding speed, such as bearings, bushings, turbines, etc., and can also be used to make elastic elements and other mechanical and electrical parts;
QSn4-0.3 alloy is used to produce various pipes in pressure gauges as sensitive elements, and is known as pressure gauge bronze.

Tin-zinc bronze:
Zinc is dissolved in large quantities in copper-tin alloys, and the amount of zinc added to deformed 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.
The grade of tin-zinc bronze listed in the current Chinese national standard is QSn4-3, which has good elasticity, wear resistance and anti-magnetism. It can be processed under pressure in cold and hot states, is easy to weld and braze, has good machinability, and has good corrosion resistance in the atmosphere, fresh water and sea water. It is used for various elastic components, pipe fittings, chemical equipment, wear-resistant parts and anti-magnetic parts.

Tin-zinc-lead bronze:
Lead is actually not soluble in copper-tin alloys. It is distributed between dendrites as a single-phase, black inclusion. The distribution of lead in the ingot is not easy to be uniform. Usually, a small amount of nickel can be added to 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% zinc is often added to copper-tin-lead alloys to further improve mechanical properties.
Adding 0.02% to 0.1% zirconium or 0.02% to 0.1% boron, especially adding 0.02% to 0.2% rare earth elements can refine the lead particles and make them evenly distributed, so as to improve the organization, casting and mechanical properties of lead-tin bronze.
The tin-zinc-lead bronze listed in the current Chinese national standard has two grades, QSn4-4-2.5 and QSn4-4-4. It has high wear resistance and is easy to cut. It is mainly used in the form of plates and strips for automobiles, tractors, aviation and machinery industries to manufacture bushings and bearing liners. It is known as automotive bronze.