Beryllium is the
fourth element on the periodic table. Beryllium metal has excellent thermal
conductivity, transparent to X-ray and is nonmagnetic. Beryllium
is a light element (density
1.85 g/cm3, it is even 1/3 lighter than Aluminium), which melts at 1300°C and has a very high Young's
modulus. The physical properties of beryllium make an item for various
applications in high end products. As metallic material, its uses are
relatively limited to aerospace and nuclear industries as well as defense
applications.
The most interesting
property of beryllium, which has been instrumental in the development of
industrial alloys, is its ability as an addition to cause precipitation hardening in other metals,
in particular nickel, aluminum and especially copper. These two alloys owe
their development to the fact that the beryllium nickel or copper,
can cause hardening of the alloy structural precipitation
annealing treatment at low temperature.
Beryllium Copper alloys
are mainly based on copper with a beryllium addition. High strength beryllium
copper alloys contain 0.4 to 2% of beryllium with about 0.3 to 2.7% of other alloying elements such as nickel,
cobalt, iron or lead. The high mechanical strength is achieved by precipitation
hardening or age hardening.
Beryllium Copper binary Phase Diagram
Because the vapor in the beryllium smelting process is poisonous to the human body, in China, the beryllium copper master alloy is only provided by a few companies such as Xinjiang and Sichuan. Internationally, related products are mainly exported from Central Asian countries.
The basic characteristics of copper beryllium alloy:
- High Strength, High Hardness: These alloys can be supplied in almost the same plastically deformed state as copper. Hardnesses up to 400 Vickers or Brinell can be obtained, possibly even higher. After deep drawing parts or parts with complex bends are formed, they can be heat treated to obtain very high mechanical properties, for bearing cages, splines, shafts, etc. Beryllium copper can still maintain its strength at 350-400°C, which is one of the reasons why it is used in die-casting/injection molding/welding machine electrodes;
- Very high tensile strength: up to 1500 MPa for gaskets, gimbal suspensions, etc.
- High Fatigue Strength: Exhibits excellent fatigue strength and excellent fatigue resistance in reverse bending and vibration: Diaphragms, springs, bellows, etc. for instrument elements and flexible parts. Although phosphor bronze can also be used in applications such as springs and diaphragms, beryllium copper has a much higher allowable stress than phosphor bronze due to its higher yield strength, so it is more durable and safer, or the product can be miniaturized and save raw materials. Therefore, due to the excellent performance of copper beryllium springs, it is possible to miniaturize the entire spring contacts originally made of phosphor bronze and cupronickel under the miniaturization trend of electronic products, while maintaining the same or higher strength. This results in a reduction in overall part, surrounding raw material (e.g. metal, plastic, resin, coating, etc.), and overall product cost. Under certain conditions, under the C17200 test with 1.5mm thick rib cold working and precipitation hardening, after 1 million minimum/maximum stress cycle tests, beryllium copper can still reach a tensile strength of 420MPa. After 100 million cycles, it can reach a strength of 300MPa!
- Excellent elasticity and conductivity: critical for power connectors (board-to-board), switches, sensors and relays automotive components, aviation instruments and connectors, telecommunications, home appliances, etc.
- Excellent wear resistance for friction and wear parts. Its excellent wear resistance is attributed to its high hardness, self-lubricating ability, the presence of a hard film surface and its high thermal conductivity. Through lubrication, the coefficient of friction of beryllium copper is significantly reduced (0.02-0.06), even under high stress (500MPa), which cannot be achieved by any other copper alloy. Therefore, beryllium copper is used to produce heavy-duty components. For example, used as bearings and bushings, such as aircraft landing gear and some heavy equipment in mining drilling technology.
- Resistance to stress relaxation: In electronic components, beryllium copper and all materials undergo stress relaxation over time, which is exacerbated by temperature. This relaxation is much lower than most other copper-based alloys (especially brass or phosphor bronze), but it is important to consider in certain applications. Therefore, the material must remain stable during operation, especially when subjected to pressure for long periods of time. Electrical contact springs must retain their properties in use, and materials with too low stress relaxation strength will lose their contact force. Over time, this can lead to increased contact resistance, greater heat generation, which can eventually lead to cracks and thus short circuits, fire hazards, etc. Electronic components are typically tested at 150°C and our beryllium copper materials remain absolutely stable under stress at this temperature for long periods of time.
- High and low temperature properties: Beryllium copper is a low temperature alloy that does not exhibit a tendency to fracture at low temperatures, but improves performance. Due to its ability to maintain strength and stability, toughness at low temperatures is used in liquid hydrogen and liquid oxygen applications in aerospace. Beryllium-copper alloys do not exhibit a ductile-to-brittle transition temperature at low temperatures, and strength (and ductility) tend to increase with decreasing temperature. In addition, because beryllium copper is age strengthened at 350-370°C, beryllium copper can work in a wide temperature range, especially at very low low temperatures, but also at high temperatures above what is usually acceptable for common copper alloys down to work.
- High electrical conductivity: Beryllium copper has a high electrical conductivity of 22-70% IACS (increased Ni content increases the electrical conductivity, although the overall electrical conductivity is not as good as pure copper), depending on the alloy and state, so it is often used in combination with good elastic characteristics For conductive connectors and contact materials. Combining high elasticity and high temperature age strengthening properties, beryllium copper is widely used in conductive spring applications because of its excellent combination of properties: strength, fatigue resistance, electrical conductivity and corrosion resistance. Demand for high-performance materials is increasing due to more compact and miniaturized assemblies of electrical components operating at higher temperatures.
- Non-magnetic: C17200 alloy has a magnetic permeability between 0.997 - 1.003 at a field strength of 1000 Gauss. Stable permeability represents perfect transparency to slowly propagating magnetic fields. This property is not affected by hardening or cold working, in contrast to other non-magnetic alloys that are magnetically activated during machining or forming. Combined with its high strength, fracture toughness, and precise dimensional stability, these properties allow our beryllium copper materials to serve exceptionally well in magnetic instrument housings, magnetic support structures, measurement equipment, and a variety of other products.
- Excellent corrosion resistance: ideal for use in marine and industrial environments. Beryllium copper has good atmospheric corrosion resistance. Although it may lose its luster, especially in humid atmospheres, this will not affect the mechanical properties. Gaseous non-anhydrous halogens accelerate corrosion. Likewise, moist ammonia is corrosive to beryllium copper. Beryllium copper has better corrosion resistance in salt spray or fog than copper or phosphor bronze. Beryllium copper is practically immune to galvanic corrosion. As a precious metal with high potential, it is not attacked by the most commonly used metals in industry, such as steel and aluminum. However, if the exposed surface of beryllium copper is large relative to these metals, the latter may be subject to galvanic corrosion instead. However, beryllium copper is corroded by sulfur in the rubber industry. In addition, experience has shown that in the die casting industry, the use of beryllium copper causes minimal corrosion when it comes into contact with molten zinc alloys, especially aluminum. Beryllium Copper is not subject to stress corrosion or "season cracking" like some brasses. They have excellent corrosion fatigue resistance and are free from hydrogen embrittlement. Due to its resistance to salt water corrosion and high mechanical strength (to a depth of up to 8000 meters), beryllium copper can be used as the main fastening element to establish and secure the intercontinental connection of deep-sea cables to surface communication networks.
- 3-5 times higher thermal conductivity than steel: often used in vacuum, non-vacuum die-casting, injection molds, welding machine electrodes. In vacuum die casting, the overflow of the melt can be reduced by 70%, which greatly saves raw materials and post-processing time; in addition, beryllium copper springs are usually active components of current conduction devices. Copper-beryllium contacts within the connector set the insertion force and provide sufficient force to minimize contact resistance. It also maintains the necessary pull-out force to ensure the integrity of the conductor circuit while maintaining current flow through the contact springs. Internal heat generated by the resistivity of the metal may cause stress relaxation in use. Over time, the selection of highly conductive materials like beryllium copper has become critical for switches, sensors and relays in automotive, aerospace and automation components. Demand for maximum performance of beryllium copper materials has increased due to more compact assemblies and miniaturization of electrical components operating at higher strengths.
- High flow and good castability: The properties of beryllium copper depend in part on the chemical composition, but cold working and age hardening are also important. The choice of tempering depends primarily on the degree of deformation or machining that the semi-finished product must undergo, as the final properties of the part depend more on precipitation heat treatment than cold deformation after solution heat treatment. Therefore, according to different applications, beryllium copper materials can have rich delivery states and heat treatment processes to achieve target performance, such as aging heat treatment at different temperatures and durations.
Our company provides various types of beryllium copper alloys:
- Strip/coil in a specific condition of slit on request
- Rods (round rods, square rods, flat bars, etc.)
- Wire (min OD0.03mm!)
- Cast and/or rolled plates
Alloy Codes Available:
- ISO/EN symbology: CuBe, CuBePb, CuBe1.7, CuNiBe
- ISO/EN number system: CW101C, CW102C, CW100C, CW110C
- UN(ASTM) system: C17200, C17300, C17000, C17510, C17530
Tempers on delivery:
- Annealed (A, fully soft)
- 1/4H
- 1/2H
- H (full hard)
Processing of beryllium copper:
For beryllium copper machining, the following points must be kept in mind:
- This alloy work hardens very rapidly and each cut must penetrate below the surface hardened by the previous cut; for practical purposes a depth of 0.2 mm is considered a minimum.
- Beryllium copper is a precipitation hardening alloy and prolonged heating during machining initiates the hardening effect. Therefore, it is very important to keep the part cool during machining.
- Beryllium oxide is very abrasive. Therefore, when machining oxidized parts, the tool should always go deep into the metal to avoid scratching the surface oxide. But on the other hand, this layer of oxide is also a strong guarantee for the high wear resistance of beryllium copper alloy.
- Beryllium copper exhibits an average 0.6 % volumetric shrinkage, 0.2 % linear shrinkage during precipitation hardening; this must be borne in mind for parts requiring close machining tolerances and final machining should be done after precipitation hardening.
- Finally, regarding the pressure of the tool and the rigidity of the support, it must be kept in mind that the yield strength of beryllium copper is only 60% of that of steel.
Joint of beryllium copper:
- Soldering: Soft solders have a relatively low melting point, below 250°C. Therefore, welding can be performed after precipitation hardening without changing the properties of beryllium copper. However, the metal must be absolutely clean before welding.
- Brazing: Silver brazing yields better results in terms of strength. Eutectic copper-silver alloys with a melting point of 780°C theoretically allow brazing at solution annealing temperatures. But this is a very delicate operation and the brazing alloys typically used melt between 600 - 650°C. The most typical melting point is 625°C and the pour point is 635°C (composition: 50% Ag, 15.5% Cu, 16.5% Zn and 18% Cd). Because these temperatures are below the solution annealing temperature, the time at these temperatures must be minimized to achieve optimum properties after precipitation hardening.
- Resistance welding: Beryllium copper can be spot welded, but also welded and lap welded. Seam welding is more difficult. Best results are obtained when the weld is in an unaged condition due to lower electrical and thermal conductivity. The welding current should be about 50% higher than that of mild steel, but the time should be shorter. If beryllium copper is to be joined to another metal, special attention must be paid to electrode selection (shape and material) and precise control of welding conditions.
- Arc welding: Arc welding can be done by the TIG method using tungsten electrodes or by the MIG method using consumable electrodes. The TIG method is of particular interest because it does not use any flux, the heating effect is limited to a relatively small area, and the inert gas protects the metal from oxidation. Welding problems with beryllium copper stem from two characteristics of the alloy:
1. Since beryllium copper is a precipitation hardening alloy, heating during welding will more or less destroy the effect of the precipitation heat treatment, so if optimum performance is desired, then Re-aging is required.
2. Beryllium oxide is very refractory and forms easily. It is therefore absolutely necessary to avoid the presence or formation of oxides.
- Electron Beam Brazing(EBM): Electron beam welding is particularly interesting for fine work, since deformations caused by the operation are minimal. Since welding is performed under vacuum, any oxidation of the materials to be joined is avoided.
Plating of beryllium copper:
- Manufacturers of beryllium copper parts are often required to supply parts with plated surfaces. Before plating, the metal must be pickled and must be absolutely clean. This is necessary because heat treatment usually produces some surface oxidation which prevents adhesion of the plating. It is recommended to use a sulfuric acid bath after heat treatment of the parts to be plated. However, this pickling leaves a reddish deposit on the metal surface, which must be removed by mechanical means (such as tumbling) or chemical means (using 20% nitric acid in water for a short period of time) to avoid attack Metal. Thorough rinsing and drying must be done after pickling.
- Plating of precious metals (gold or silver) is often required for electrical contacts that must have low contact resistance, good surface conductivity for high frequency currents, etc. For this type of plating, a thin layer of nickel is usually deposited as a diffusion barrier. This deposit should be very thin, about 0.5-1 micron, especially if the part is subjected to bending in operation, as the nickel layer is particularly fragile.
Please contact us if you have any demand on the beryllium copper alloys from us.
