Beryllium Bronze

What Is Beryllium Bronze?

A Wuxi bronze with beryllium as the main alloy component. It contains 1.7-2.5% beryllium and a small amount of nickel, chromium, titanium and other elements. After quenching and aging treatment, the strength limit can reach 1250-1500MPa, which is close to the level of medium-strength steel. In the quenched state, it has good plasticity and can be processed into various semi-finished products.

Beryllium bronze has high hardness, elastic limit, fatigue limit and wear resistance. It also has good corrosion resistance, thermal conductivity and electrical conductivity. It does not produce sparks when impacted. It is widely used as important elastic components and wear-resistant parts. And explosion-proof tools, etc.

Commonly used grades are QBe2, QBe2.5, QBe1.7, QBe1.9, etc.

Introduction

Bronze with beryllium as the main additive element. The beryllium content of beryllium bronze is 0.2% to 2%, and a small amount (0.2% to 2.0%) of the third component of cobalt or nickel is added. The alloy can be strengthened by heat treatment. It is an ideal high-conductivity, high-strength elastic material.

Beryllium bronze is non-magnetic, anti-spark, wear-resistant, corrosion-resistant, fatigue-resistant and stress-relaxation resistant. And easy to cast and press forming. The typical uses of beryllium bronze castings are as plastic or glass molds, resistance welding electrodes, explosion-proof tools for petroleum openings, and submarine cable shields.

The typical use of beryllium bronze processing materials is as current-carrying reeds, connectors, contacts, fastening springs, leaf springs and coil springs, bellows, bellows and lead frames in electronic devices.

classification

Beryllium bronze is divided into two categories. According to the alloy composition, the beryllium bronze with a beryllium content of 0.2% to 0.6% is high-conductivity (electrical and thermal) beryllium bronze; the beryllium bronze with a beryllium content of 1.6% to 2.0% is a high-strength beryllium bronze. According to the manufacturing process, it can be divided into cast beryllium bronze and deformed beryllium bronze.

The internationally used beryllium bronze alloy grades are led by C. There are two types of deformed beryllium bronze: C17000, C17200 (high-strength beryllium bronze) and C17500 (high-conductivity beryllium bronze). Corresponding cast beryllium bronzes are C82000, C82200 (high-conductivity cast beryllium copper) and C82400, C82500, C82600, C82800 (high-strength wear-resistant cast beryllium copper).

The history of China’s production of beryllium bronze is almost synchronized with the former Soviet Union, the United States and other countries, but the only grades listed in the national standard are high-strength beryllium bronze QBe1.9, QBe2.0, and QBe1.7. Other high-conductivity beryllium bronzes or cast beryllium bronzes have been put into mass production according to the needs of the development of the petroleum industry and the defense industry.

performance

Performance parameter table

Grade	Main ingredients	Impurity content (≤ wt%)    Ni Cu Fe Al Si Pb total
QBe2.0	1.8-2.1 / 0.2-0.25	margin 0.15 0.15 0.15 0.005 0.5
QBe1.9	1.85-2.10 0.1-0.25 0.2-0.4	margin 0.15 0.15 0.15 0.005 0.5
CuBe2	1.8-2.0	Co≤0.20        Ni+Co+Fe≤0.6
CuBe1.0	0.40-0.70	Co:2.35-2.70      Cu+Be+Ni+Co≥99.5

Physical characteristics

Performance\Alloy	QBe2.0 CuBe10 CuBe7
Density g/cm	at 20℃ 8.26 8.75 8.75
Thermal expansion coefficient	at20-300℃ 1.78×10 -5 1.76×10 -5 1.75×10 -5
Specific heat　Cal/g ℃	at 20℃  0.1 0.1 0.1
Conductivity %IACS	at 20℃ 22 48 38
Longitudinal modulus of elasticity LME	MPa 130000 135000 127000
Transverse modulus of elasticity TME	MPa 50000 52500 49000
Thermal conductivity　Cal/cm sec ℃	at 20℃ 0.2-0.31 0.40-0.62 0.40-0.60

Beryllium bronze has good comprehensive properties. Its mechanical properties, namely strength, hardness, wear resistance and fatigue resistance rank first among copper alloys. Its electrical conductivity, heat conduction, non-magnetic, anti-sparking and other properties cannot be compared with other copper materials. In the solid solution and soft state, the strength and conductivity of beryllium bronze are at the lowest value. After work hardening, the strength is improved, but the conductivity is still the lowest. After aging heat treatment, its strength and electrical conductivity increase significantly.

The machining performance, welding performance and polishing performance of beryllium bronze are similar to those of general high-copper alloys. In order to improve the machining performance of the alloy to meet the precision requirements of precision parts, various countries have developed a high-strength beryllium bronze (C17300) with a lead content of 0.2% to 0.6%. Its various properties are equivalent to C17200, but the alloy’s cutting coefficient Increased from the original 20% to 60% (100% for free-cutting brass).

Process treatment

Beryllium bronze is a typical aging precipitation strengthening alloy. The typical heat treatment process of high-strength beryllium bronze is to keep it at a temperature of 760～830℃ for an appropriate time (at least 60 minutes per 25mm thick plate), so that the solute atom beryllium is fully dissolved in the copper matrix to form the α phase of the face-centered cubic lattice Supersaturated solid solution. Subsequently, the temperature is kept at 320-340°C for 2 to 3 hours to complete the precipitation and precipitation process to form a γ’phase (CuBe2 metastable phase). This phase is coherent with the matrix to create a stress field and strengthen the matrix.

The typical heat treatment process of high-conductivity beryllium bronze is to keep it at a high temperature of 900～950℃ for a period of time to complete the solid solution process, followed by keeping it at 450～480℃ for 2～4h to realize the precipitation process. Since more cobalt or nickel is added to the alloy, the dispersion strengthening particles are mostly intermetallic compounds formed by cobalt or nickel and beryllium.

In order to further improve the strength of the alloy, a certain degree of cold working is often performed on the alloy after solution heat treatment and before aging heat treatment, in order to achieve the comprehensive strengthening effect of cold work hardening and age hardening. The degree of cold working generally does not exceed 37%. Solution heat treatment should generally be carried out by the alloy manufacturer. After the user punches the solution heat-treated and cold-rolled strip into parts, it is self-aged and heat-treated to obtain high-strength spring elements.

In recent years, the United States has developed strips that are aging heat treated by beryllium copper manufacturers, and customers can directly punch them into parts for use.

After beryllium bronze has been treated by various processes, the letters in Europe and the United States for the alloy state are: A means solution annealed state (annealed), the alloy is in the softest state, easy to stamping and forming, and it needs to be cold worked or direct aging strengthening treatment in the next step .

H stands for work-hardened state (hard). Taking cold-rolled plates as an example, 37% of cold work is fully hard (H), 21% of cold work is semi-hard (1/2H), and 11% of cold work is 1/4 hard state (1/4H), the user can choose the appropriate soft and hard state according to the difficulty of the shape of the part to be punched. T represents the heat treatment state (heat treatment) that has been aging strengthened. If the deformation and aging strengthening process is adopted, its state is indicated by HT.

Security

The beryllium contained in the beryllium bronze alloy has a mass percentage of 2%, but an atomic percentage of 9.0122%. During high temperature operations such as smelting, casting, heat treatment, welding, and cutting machining, beryllium oxide (BeO) is formed.

Most of the beryllium oxide will firmly adhere to the surface of the original workpiece, but during intense movements such as cutting, polishing, welding, etc., fine particles (less than 10μm) dust will be suspended in the air. If the operator inhales excessively, it will cause ” Beryllium lung” occupational disease. Therefore, the above working environment must have a complete directional exhaust device. Cutting, polishing and other processes must be carried out in a wet state with coolant.

The United States Occupational Safety and Health Administration (OSHA) stipulates the following standards: Regular air sampling is carried out in the operation workshop of beryllium products and the surrounding environment. For workers who work 8 hours a day, the content of beryllium in the working environment shall not exceed 2μg/m3. . In order to reduce the pollution caused by beryllium copper, China and Japan have developed titanium with similar elasticity in recent years, and can be used as a good substitute material for beryllium bronze in some workplaces.