Beryllium Copper

Chapter 1: What is Beryllium Copper?

Beryllium Copper is a versatile copper alloy that is valued for its high strength and hardness, combined with good electrical and thermal conductivity. It is a non-ferrous, non-magnetic, and non-sparking metal alloy. The other names for Beryllium Copper are Beryllium Bronze and Spring Bronze.

Beryllium copper is a relatively new metal alloy, unlike brass and bronze which was discovered centuries before this alloy. Beryllium metal was first isolated in 1828 by reacting beryllium chloride with potassium. The first beryllium copper metal pieces in the form of conductive springs were created in the same country in 1920 which were used in telephone switchboard relays. In 1970, the use of beryllium copper became popular in the automotive and telecommunications industry.

Nowadays, beryllium copper is widely used in industries such as energy (tools for oil and gas extraction, coal mining), power, electronics (connectors), cryogenics, automotive (valve seats and guides, anti-lock braking), and much more. Beryllium copper is a good material selection for musical instruments like triangles, trumpets, bells, and tambourines because it gives consistent tones and resonance. It can withstand marine environments due to its biofouling properties combined with high strength. It is also used on Magnetic Resonance Imaging (MRI) equipment wherein the use of magnetic ferrous metals can be detrimental.

Chapter 2: Comparison of Beryllium Copper, Brass, and Bronze

Alloy is a mixture of a metal combined with another metal or other non-metal elements to enhance its properties. Beryllium copper, brass, and bronze are all copper base alloys. Copper is considered as the “solvent” or the main alloying element of these mixtures. Corrosion, biofouling resistance, and thermal and electrical conductivities are all properties inherited from copper.

• Brass: Brass is an alloy of zinc and copper. It is a metal with good strength and ductility that is attributed to zinc properties. It has better malleability than bronze. It has been used since prehistoric times but was discovered at around 1,400 B.C. It has historically been referred to as "yellow copper". It has a dulled yellowish to reddish color, depending on the amount of zinc alloyed. Applications of brass are musical instruments, plumbing materials, and ammunition components. The light-colored variation of brass is used in decorative pieces of jewelry as a substitute for gold.
  
  

  

  
  
• Bronze: This alloy is a combination of copper and additives such as tin (the main additive), manganese, and phosphorus. It was discovered earlier than brass which dates back around 3,500 B.C. It is a hard and brittle metal and has a higher melting point than brass. It is distinguished by its reddish-gold color. Applications of bronze are sculptures, musical instruments, electrical connectors and springs, fittings, etc.
  
  

  

  
  
• Beryllium Copper: This alloy is made of beryllium and copper combined with small amounts of alloying elements. Beryllium is found in 30 different mineral species. It is a soft, low-density metal with a steel-gray color. When alloyed with copper, it increases its strength, hardness, electrical and thermal conductivities. More characteristics of beryllium copper and its applications will be discussed in the succeeding chapters.
  
  

  

  
  

Chapter 3: Types of Beryllium Copper Alloys

Beryllium copper pieces may be wrought or cast and may be sold in a variety of forms such as plates, rods, strips, and wires. Wrought beryllium copper metals are commonly formed through hot or cold working. Cast beryllium copper pieces are shaped by pouring or injecting molten beryllium copper into a mold. The forming process is followed by age hardening for better modification and control of the resulting mechanical properties.

Beryllium copper alloys are divided into two categories according to its composition and the inherent physical properties it exhibits. The physical properties are mainly influenced by the beryllium content of the alloy and addition of other alloying elements, and the heat treatment conditions employed by the manufacturer.

• High Strength Beryllium Copper Alloys: High strength beryllium copper alloys contain 1.6 - 2.05% beryllium. These groups are used for heavier duty applications. Some of the high strength beryllium copper alloys are:
  • Alloy 25: Alloy 25, also known as UNS 17200, has the highest strength and hardness of all beryllium copper alloys. It is the most prominent beryllium copper alloy and is widely used in the oil and gas industry. This alloy is also used in springs that must be non-magnetic, electrically conductive (current-carrying springs), and corrosion-resistant.
    
    

    

    
    
  • Alloy M25: Alloy M25, also known as UNS C17300, has a higher lead content ranging from 0.2 - 0.6%. The addition of lead results in a reduction of chipped-edge during cutting decreasing tool wear. Hence, it is suitable for the manufacturing of electronic, automotive, and aerospace components. This alloy offers ease of fabrication and machinability over other high strength alloys. Moreover, it also has a high fatigue resistance. It is used in current-carrying springs, welding electrodes, and electrical and electronic connectors.
    
    

    

    
    
  • Alloy 165: Alloy 165, also known as UNS C17000, has lower beryllium content. It has a slightly lower strength than the previous high strength alloys. It is a less expensive alternative to Alloy 25 which may be used when the application is lighter. It also maintains its strength in cryogenic conditions. It is also commercially applied in tools and apparatuses such as fasteners, bearings and bushes, and resistance welding equipment.
    
    

    

    
    
• High Conductive Beryllium Copper Alloys: High conductive beryllium copper alloys contain lower beryllium content that ranges from 0.2 – 0.7%, with trace amounts of cobalt and nickel. As the name implies, these alloys have high electrical and thermal conductivity. The copper alloying element gives the thermal and electrical properties. However, these properties are decreased with increasing beryllium content which in turn results in a higher strength material. The same is true for other alloy mixture systems (e.g., brass and bronze). Some of the high conductive beryllium copper alloys are:
  • Alloy 3: Alloy 3, also known as UNS C17510, contains 0.2 - 0.6% beryllium and 1.4 - 2.2% nickel. This alloy may be used in applications in which moderate material strength would suffice. It has a high resistance to thermal fatigue. The wire form of this alloy is used in power and signal cables in offshore oil and gas operations. In strip form, it is used in switches and relays due to its high electrical conductivity.
    
    

    

    
    
  • Alloy 10: Alloy 10, also known as UNS C17500, contains 0.4 - 0.7% beryllium and higher cobalt content of 2.4 – 2.7%. This alloy has similar mechanical properties to Alloy 3. The addition of cobalt in this alloy slightly lowers its thermal conductivity and melting point. It has a high thermal resistance and has good hot working and cold working properties. It is an excellent material for casting and molding tools.
    
    

    

    
    
  • Alloy 10X: Alloy 10X has 0.4 – 0.7% beryllium content and additions of cobalt (2.0 – 2.7%) and zirconium (0.12 – 0.4%). This alloy is known for its high strength and ductility which are maintained at elevated temperatures. It is also resistant to thermal cracking.
  • Alloy 310: Alloy 310 has 0.4 – 0.7% beryllium content and additions of cobalt (0.8 – 1.3%) and nickel (0.8 – 1.3%). This alloy is less expensive compared to other beryllium copper alloys. It has high strength and hardness, combined with high electrical and thermal conductivity. Alloy 310 is commonly used in welding electrodes, plunger tips, dies, and nozzles.
    
    

    

    
    

Chapter 4: Characteristics of Beryllium Copper

Beryllium copper attains the highest strength of all copper alloys while maintaining high thermal and electrical conductivity. These are the most prominent characteristics of this alloy. Tensile strength of high strength beryllium copper alloys can exceed 200 ksi or around 1,400 MPa. Its strength and hardness are brought by precipitating beryllium out of the alloy mixture through a heat treatment process called precipitation hardening.

Other distinguishable properties of beryllium copper that sets it apart from other metals are the following:

• Non-sparking. This is the most prominent characteristic of a beryllium copper metal piece. It does not produce a frictional spark when struck with other metals which makes it a safe material choice for tools in environments with fire and explosive hazards like oil rigs and coal mines. A hot dislodged particle of beryllium copper from the tools cools rapidly and does not cause ignition of nearby flammable material.
  
  

  

  
  
• Galling and abrasion resistance. Galling is a type of mechanical wear of the metal surface caused by adhesion and frictional forces, especially if it is not lubricated. It is commonly experienced by two metals in which their surfaces are sliding with each other under compressive forces (e.g., thread). Beryllium copper does not exhibit wear and produces minimal friction and surface damage when in contact with other metal pieces, even under overload conditions and continuous vibration. Beryllium copper is also abrasion-resistant.
  
  

  

  
  
• Non-magnetic. Being a non-ferrous metal, beryllium copper is non-magnetic. Magnetic fields do not disrupt the normal function of a beryllium copper component. Beryllium copper does not behave like a “hot magnet” during machining and forming, unlike other metal alloys.
• Excellent response to temperature extremes. Tensile strength and toughness of beryllium copper are maintained at temperature extremes, even at long exposure times. Beryllium copper can be used in cryogenic conditions, wherein steels become brittle at very low temperatures. The performance of beryllium copper at elevated temperatures is above average compared to other copper alloys. Along with its inherent hardness, it is therefore commonly used in molding tools and welding electrodes.
  
  

  

  
  
• Corrosion resistance. Beryllium copper does not corrode in harsh environments, resistant to biofouling, and does not tarnish easily. It is immune to chlorine-induced stress corrosion cracking, unlike stainless steel of the same value that cracks after a few hours of exposure to high chloride conditions. Hence, it is a good material selection for apparatuses and equipment in a saline environment and oil and gas plants.

  Beryllium copper can be used to routinely handle glycols, ketones, hydrocarbons, and esters. However, impurities present in these solutions can accelerate the corrosion of beryllium copper. These impurities can be sulfides, acids, and salts. Curing of polyvinyl chloride and room temperature vulcanized silicone emit fumes which can corrode the beryllium copper metal piece.

• Good machinability. Beryllium copper is machined with relative ease. It is metal-worked before the hardening process which is done by the fabricator. Before the hardening process, the beryllium copper has a moderate hardness level and high ductility.
  
  

  

  
  

  Beryllium copper is resistant to hydrogen embrittlement. Hydrogen embrittlement is the phenomenon where hydrogen atoms are absorbed in the beryllium copper microstructure during fabrication processes such as welding, hot forming, and electroplating. Hydrogen-embrittled beryllium copper parts are prone to cracking when stress is applied.

• Dimensional stability. Age precipitation of beryllium copper relieves stress and imparts exponential strength and hardness which results in high dimensional stability of the metal piece during stamping and cutting processes.

Chapter 5: Heat Treatment of Beryllium Copper

Heat treatment of beryllium copper requires a series of controlled heating and cooling which gives it desirable mechanical properties. The benefits of heat treatment of beryllium copper are a significant increase in strength, durability, and machinability. This process applies to all wrought and cast beryllium copper alloys.

The physical states of the beryllium copper solution are illustrated as a function of temperature and concentration in the binary phase diagram shown below. A phase diagram is a useful tool for understanding the heat treatment process. Thermal properties of beryllium copper, such as boiling point and melting point, varies with beryllium content.

Heat treatment of beryllium copper occurs in two stages: solution annealing and age precipitation.

Solution Annealing

Solution annealing is usually done at the supplier’s side and prepares the beryllium copper piece for age hardening. At this stage, the beryllium precipitates are dissolved in the copper matrix to form a supersaturated beryllium copper solution, through the diffusion of beryllium atoms in the alpha phase. It also ensures a uniform concentration of beryllium on the alloy system and regulates its grain size. Depending on the alloy composition, the beryllium copper is heated slightly below the solidus temperature which is varying around 790⁰C for high strength alloys and 900⁰C for high conductivity alloys until a solid homogeneous mixture is present. At the solidus curve (curve BC) in the binary phase diagram, the solid and liquid phases of beryllium copper coexist. The solidus temperature decreases with increased beryllium concentration. The annealing temperature and time are controlled to prevent undesirable grain growth and melting.

To maintain the resulting structure (in a supersaturated solution) from the annealing step at room temperature, the beryllium copper piece is rapidly quenched in cooling water. The result is a soft and ductile beryllium copper metal piece that is readily cold worked by forming, drawing, or rolling.

Age Hardening

Age hardening, or precipitation hardening, involves heating below the solvus temperature and slow cooling of the annealed piece. Heating lasts for one to more than an hour at around 200-400⁰C in a furnace. Below the solvus region in the binary phase diagram, beryllium and copper exist as two distinct solid microstructures. The solvus temperature also increases with increased beryllium concentration. Age hardening is performed after the forming and shaping process.

Strengthening and hardening of the beryllium copper piece are attributed to the precipitation of beryllium out of the solution. Precipitation is brought by slow cooling. In general, the solubility of the solute decreases as the temperature of the solution decreases. Beryllium-rich (gamma) phase comes out in the copper matrix as beryllides, along the grain boundaries.

Heating temperature and time are the critical parameters in age hardening, in which physical properties such as strength and conductivity are the responses. The age hardening condition is arbitrary to the customer, depending on the end application of the beryllium copper piece. The common age hardening conditions are:

• Under aging. Under aging is done at lower heating temperatures and/or lower heating times. Under aging a beryllium copper piece results in uniform elongation and increases its ductility and toughness. The strength and hardness are lower than the optimal.
• Over aging. Over aging, on the other hand, is done at higher heating temperatures and/or higher heating times. This age hardening condition produces a beryllium copper piece that is thermally and dimensionally stable, ductile, and tough, and has high electrical and thermal conductivity.
• Peak aging. This age hardening condition is brought by the optimal heating temperature and time which yields the highest tensile strength, hardness, thermal and electrical conductivity.

During age hardening, oxides of beryllium and copper are developed on the surface of the metal piece. The development of oxides is inevitable even in pure hydrogen atmospheres or in vacuum conditions, but its effect is not detrimental to the properties of the parts. However, it is important to remove the surface oxides if the parts were to be plated or soldered.

Chapter 6: Safe Handling of Beryllium Copper

Beryllium copper can pose health hazards like other metal alloys. The mechanisms of its entry into the human body and its effects on health are:

• Inhalation of dust and fumes. Operations such as grinding, abrasive cutting, polishing, and electrochemical machining produce fine beryllium copper particulates. Heat treatment and welding can produce fumes with low to moderate beryllium concentration. Beryllium copper particulates can irritate the nose, throat, lungs, and mucous membranes. Long term exposures from beryllium copper particles can cause a serious lung disease called chronic beryllium disease (CBD) to susceptible individuals.

  Beryllium is known to be a human carcinogen. Workers involved in beryllium copper production have a high risk to develop lung cancer.

• Ingestion by accident, or swallowing food and drinks contaminated with beryllium copper. Beryllium copper has no effects when ingested in minimal amounts. However, large doses can induce ulceration, jaundice, and kidney and liver damage.
• Skin or eye penetration of fine beryllium copper particulates. Since beryllium copper is not soluble at room temperature, it is unable to penetrate the skin and eyes, thus it not hazardous when handled in solid or bulk form. However, it may be a skin allergen to some individuals. It can also cause eye irritation.

The following are industry practices to minimize the health risks involved when handling beryllium copper, particularly to protect the workers from toxic dust and fumes:

• Use of coolant and lubricant during machining to collect beryllium copper dust and shavings.
• Wearing personal protective equipment. Specialized air-supplied breathing masks must be worn by furnace operators.
• Air filtration systems.
• Monitoring of beryllium content in the air on the shop floor. The occupational exposure limit set by OSHA is 2 micrograms of beryllium per cubic meter of air (2 µg/m3) for an 8-hour work shift.

Conclusion:

• Beryllium copper is a valued metal alloy known for its high strength and hardness, combined with high electrical and thermal conductivity. It is non-ferrous, non-magnetic, and non-sparking. It is widely used in industries like energy, automotive, electronics, and much more.
• Brass and bronze are other copper base alloys. Brass is a strong and ductile metal which is an alloy of copper and zinc. Bronze is a hard and brittle metal that is a combination of copper and other alloying elements such as tin (the main additive), phosphorus, and manganese.
• Two categories of beryllium copper alloys are high strength alloys and high conductivity alloys.
• Other properties that set beryllium copper from other metals are non-sparking, galling and abrasion resistance, non-magnetic, excellent response to temperature extremes, corrosion resistance, good machinability, and dimensional stability.
• Heat treatment of beryllium copper gives its desirable mechanical properties. It occurs in two stages: solution annealing and age hardening.
• Conditions for age hardening are: under aging, over aging, and peak aging.
• Health hazards are present when handling beryllium copper. It can enter the human body by inhalation (the most hazardous), ingestion, and skin and eye penetration. Safety measures must be taken on the shop floor when working with beryllium copper.