Tin bronze

What Is Tin bronze?

Bronze with tin as the main alloying element. The tin content is generally between 3 and 14%, which is mainly used to make elastic components and wear-resistant parts. The tin content of wrought tin bronze does not exceed 8%, and elements such as phosphorus, lead, and zinc are sometimes 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-wear properties and corrosion resistance, easy cutting processing, good brazing and welding properties, small shrinkage coefficient, and non-magnetic. Wire flame spraying and electric arc spraying can be used to prepare coatings such as bronze bushings, shaft sleeves, diamagnetic elements, etc. The size specifications are Ф1.6mm and Ф2.3mm. With high strength, corrosion resistance and excellent casting performance, it has been widely used in various industrial sectors for a long time.

characteristic

In addition to tin bronze containing 3% to 14% tin, phosphorus, zinc, lead and other elements are often added. It is the earliest alloy used by mankind, and it has been used for about 4,000 years. It is corrosion-resistant, wear-resistant, has good mechanical properties and process performance, and can be welded and brazed well without sparks during impact.

Divided into processed tin bronze and cast tin bronze. The tin content of tin bronze used for pressure processing is less than 6% to 7%, and the tin content of cast tin bronze is 10% to 14%. Commonly used grades are QSn4-3, QSn4.4-2.5, QSn7-O.2, ZQSn10, ZQSn5-2-5, ZQSN6-6-3, etc.

Tin bronze is a non-ferrous metal alloy with the smallest casting shrinkage. It can be used to produce castings with complex shapes, clear contours and low air tightness requirements. Tin bronze is very resistant to corrosion in the atmosphere, sea water, fresh water and steam, and is widely used in steam boilers and marine ship parts.

Phosphorus tin bronze has good mechanical properties and can be used as wear-resistant parts and elastic parts of high-precision machine tools;

Leaded tin bronze is often used as wear-resistant parts and sliding bearings;

Zinc-tin bronze can be used as high-airtight castings.

The solidification range of tin bronze is large, and dendrite segregation is serious; concentrated shrinkage is not easy to form during solidification, and the volume shrinkage is small; reverse segregation of tin is easy to appear in the ingot, and white spots (8-phase precipitation) can be seen on the surface of the ingot in severe cases. There are even tin-rich particles, generally called tinsweat.

Improving the casting method and process conditions can reduce the degree of reverse segregation; in liquid alloys, tin is prone to form hard and brittle inclusions SnO2, and smelting must be fully deoxidized to prevent the decrease of alloy mechanical properties caused by inclusions; sensitivity to overheating and gas It is small and can be welded and brazed well; no spark occurs when impacted, non-magnetic, cold-resistant, and has high wear resistance.

classification

Industrial tin bronze Tin bronze is an important copper alloy used in industry. In order to improve its casting, mechanical and wear resistance properties, and save tin, alloy elements such as phosphorus, zinc, lead, etc. are added to tin bronze. Therefore, tin bronze can be divided into three types: tin-phosphorus bronze, tin-zinc bronze and tin-zinc-lead.

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, a+δ+Cu3P ternary eutectic will be formed, with a melting point of 628℃. It is prone to 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.

Cold-worked materials undergo low-temperature annealing at 200-260°C for 1 to 2 hours to produce annealing hardening effect, which can further improve the strength, plasticity, elastic limit and elastic modulus of the product, and increase the stability of elasticity.

A total of 4 grades of phosphorous tin bronze have been included in China’s national standards.

Among them, QSn6.5-0.1 alloy is mainly used to make elastic components, especially spring contact sheets with good electrical conductivity, wear-resistant parts and diamagnetic components in instruments and meters, etc.;

Qsn6.5-0.4 alloy is mainly used in papermaking, chemical and food industries to make metal meshes, and also used to make wear-resistant and spring parts;

QSn7-0.2 alloy is used for parts that bear friction under moderate load and sliding speed, such as bearings, bushings, turbines, etc., and can also be used to manufacture elastic components and other mechanical and electrical parts;

QSn4-0.3 alloy is used to produce various pipes in pressure gauges, as sensitive components, and is called pressure gauge bronze.

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, reduce the crystallization temperature range, and reduce reverse segregation.
The tin-zinc bronze grade listed in the current Chinese national standard is QSn4-3, which has good elasticity, wear resistance and diamagnetism. It can be press-processed in cold and hot conditions, easy to weld and braze, and has good machinability , It has good corrosion resistance in the atmosphere, fresh water and sea water. It is used for various elastic components and pipe fittings, chemical equipment, wear-resistant parts and anti-magnetic parts, etc.

Tin zinc lead bronze

Lead is not actually dissolved in the copper-tin alloy. 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 mechanics of lead-containing tin bronze performance.

The tin-zinc-lead bronzes listed in the current Chinese national standards are:

QSn4-4-2.5 and QSn4-4-4 two grades

It has high wear resistance and easy cutting processing. It is mainly used in the automobile, tractor, aviation and machinery industries in the form of plates and strips to manufacture bushings and bearing pads. It is called automobile bronze.

application

Copper is a non-ferrous metal closely related to human beings. It is widely used in electrical, light industry, machinery manufacturing, construction industry, national defense industry and other fields. It is second only to aluminum in the consumption of non-ferrous metal materials in my country.

Tin bronze is a non-ferrous metal alloy with the smallest casting shrinkage rate. It is used to produce castings with complex shapes, clear contours and low air tightness requirements. Tin bronze is very resistant to corrosion in the atmosphere, sea water, fresh water and steam, and is widely used in steam boilers and marine ship parts.

Phosphorus-containing tin bronze has good mechanical properties and can be used as wear-resistant parts and elastic parts of high-precision machine tools. Leaded tin bronze is often used as wear-resistant parts and sliding bearings.

Zinc-tin bronze can be used as high-airtight castings.

Tin bronze is the most widely used and used in the electrical and electronic industries, accounting for more than half of the total consumption. Used in various cables and wires, motors and transformers, switches, and printed circuit boards. In the manufacture of machinery and transportation vehicles, it is used to manufacture industrial valves and fittings, meters, sliding bearings, molds, heat exchangers, and pumps.

It is widely used in the chemical industry to manufacture vacuum vessels, distillation pots, brewing pots, etc. In the defense industry, it is used to manufacture bullets, shells, gun parts, etc. For every 3 million bullets produced, 130-140 tons of copper are needed.

In the construction industry, it is used as various pipes, pipe fittings, decorative devices, etc.