Beryllium bronze is a type of alloy that is typically strengthened by a dispersed phase. After heat treatment, it has extremely high strength and hardness, far exceeding all other copper alloys, and even comparable to high-strength steel. In addition, it also has high elasticity, fatigue resistance, cold resistance, corrosion resistance, small elastic hysteresis, non-magnetic, impact and no spark generation, etc., is an essential material for modern manufacturing, Used to restrict the export of military copper alloys to China for foreign countries. Although beryllium has certain toxicity, it may cause damage to human body and natural environment during cnc machining and use.
However, due to the excellent comprehensive properties of beryllium copper alloys, it cannot be replaced by other materials. In recent years, with the rapid development of electric vehicles, electrical and electronic industries, high-speed railway networks, and high-speed train construction, beryllium bronze has become increasingly important worldwide as an important raw material for the manufacture of parts in this field. With the development of economy and society, customers have put forward more stringent requirements for the comprehensive performance and environmental friendliness of beryllium bronze, and some new preparation and processing technologies can more and more meet these requirements. This paper studies and summarizes the preparation and heat treatment process of beryllium bronze alloy material, and prospects the development direction and application prospect of its future processing technology.
Commonly used beryllium bronze grades are QBE1.7, QBE2, QBE1.9, QBE2.5. Their chemical composition table is shown in Table 1. Zh
Beryllium bronze alloy not only has good plasticity during processing before precipitation of the strengthening phase (solid solution state), but also can prepare for subsequent aging strengthening. Its strength and hardness increase with the increase of beryllium content, but beryllium has a certain solubility in copper. When the maximum solubility of beryllium is reached, more γ phases cannot be precipitated from the saturated α solid solution in the subsequent aging process. (The γ phase is a solid solution based on a CuBe compound), so its hardness is no longer improved. Beryllium bronze parts have a high fatigue life. For example, the fatigue life of parts such as micro-switch bent pieces and contact springs processed from beryllium bronze alloys has reached more than one million times. The beryllium bronze alloy has good corrosion resistance, and the corrosion rate in seawater is extremely low ((1.1 ~ 1.4) × 10-2mm / a), and its elongation and strength hardly change after corrosion. It also has the characteristics of non-sparking and non-magnetic impact, and has important applications in military weapons and aerospace equipment; for example, its application in aviation products can ensure the magnetic cleanliness of spacecraft. In addition, beryllium bronze alloys have good thermal conductivity and solderability, and are widely used in mold manufacturing and other applications.
2. During the smelting process of beryllium bronze alloy, it is necessary to strictly control the process parameters such as smelting temperature and time, and perform slag refining and deoxidation and exhaust operations when the smelting temperature reaches 1,200 to 1,300 ° C. Casting at a temperature of 1,100 to 1,150 ° C can obtain higher quality beryllium bronze ingots [6-7]. Homogenization annealing can make the structure more uniform and the performance more stable. Beryllium bronze alloy easily reacts with oxygen in the air during the smelting process.
3. Take anti-oxidation measures in non-vacuum melting. When charcoal and phosphorous copper are used for degassing, the charcoal powder cannot be used to form a comprehensive and effective protection because the charcoal powder is burned at high temperatures. The degassing process covered with borax and broken glass and passed in argon works best; the reason is that borax and glass are under high temperature After melting, a uniform and dense protective film is formed to prevent air from entering. Smelting a beryllium bronze alloy using a vacuum device can prevent oxidation and reduce the volatilization of beryllium oxide, reducing the damage to the environment and workers' bodies.
1.Solution treatment process of beryllium bronze material
The solubility of beryllium in copper increases with increasing temperature. The solubility of beryllium at room temperature is 0.16%, its solubility at 400 ° C is 0.6%, and its solubility reaches its maximum when the temperature is 866 ° C. (2.7%), a supersaturated alpha solid solution was formed. At this time, as the temperature decreases, the beryllium content in the α solid solution gradually decreases, and the solubility curve of beryllium gradually shifts to the copper side. The beryllium bronze alloy reaches the solid solution temperature and then keeps the heat for a suitable time to allow the beryllium to fully solidify and quickly cool. The beryllium-rich phase is too late to precipitate, thereby forming a supersaturated alpha solid solution. This is the solid solution principle of beryllium bronze. In order to ensure its good comprehensive properties after aging, the parameters of solid solution treatment of beryllium bronze alloy should be controlled within a range that can make beryllium fully solid solution without grain growth. If the solution temperature is too low or the time is short, beryllium cannot be fully dissolved in the copper matrix, which will cause the precipitation strengthening ability of the alloy to be reduced. If the solution temperature is too high, the grains will be coarsened and even the grain boundaries will melt ( (Overburning), the brittleness of the material increases and the performance deteriorates.
2.Aging treatment process of beryllium bronze material
The workpiece in the solid solution state cannot be used directly, and it must have high strength, hardness, elastic modulus, elastic limit, fatigue limit and creep resistance after aging treatment. The essence of beryllium bronze gold ageing treatment is to decompose the highly dispersed γ phase from the supersaturated α solid solution at a suitable temperature, forming a dispersion strengthening effect, and improving the comprehensive mechanical properties of the material. The supersaturated solid solution decomposition process is as follows: supersaturated α solid solution → G · P zone → γγ → γ First, beryllium is enriched at the grain boundary to form a G · P · zone (segregated zone). As the aging temperature increases and the aging time increases The G · P · region grows up and transforms into an intermediate transition phase γ ′, and then further transforms into a stable γ phase. The γ phase is an intermetallic compound, which is brittle and hard. Its dispersion distribution can increase the resistance of dislocation movement, which further improves the strength and hardness of the beryllium bronze material. In addition to the element Be in the beryllium bronze alloy, other elements can also affect the mechanical properties of the beryllium bronze alloy.
The beryllium bronze alloy parts used in the field of electronics and electronics not only require good abrasion resistance, but also have excellent electrical conductivity. To this end, the surface needs to be silver-plated [31]. In addition, beryllium bronze alloys need to be plated for aesthetic or other purposes, such as increased solderability.
Beryllium bronze parts are electroplated to meet customers' pursuit of higher performance, which is an important part of their processing technology.
The beryllium bronze alloy contains elements such as beryllium, nickel, and titanium that are easily passivated, and can form an invisible oxide film even at normal temperature. During the heat treatment, even a heat treatment performed in a vacuum furnace may undergo slight oxidation. These oxide films can cause poor bonding between the substrate and the plating layer, which can cause defects such as bubbles, molting, and pitting in the coating layer. In addition, once the plating layer contains impurities such as organic matter, more micropores are prone to occur. The formation of micro-batteries under the effect of, causing more severe corrosion. The pre-plating treatment can remove the oxide film. The traditional pre-treatment process is not effective, and the acid mist will volatilize, endangering the natural environment and workers' health.
However, due to the excellent comprehensive properties of beryllium copper alloys, it cannot be replaced by other materials. In recent years, with the rapid development of electric vehicles, electrical and electronic industries, high-speed railway networks, and high-speed train construction, beryllium bronze has become increasingly important worldwide as an important raw material for the manufacture of parts in this field. With the development of economy and society, customers have put forward more stringent requirements for the comprehensive performance and environmental friendliness of beryllium bronze, and some new preparation and processing technologies can more and more meet these requirements. This paper studies and summarizes the preparation and heat treatment process of beryllium bronze alloy material, and prospects the development direction and application prospect of its future processing technology.
Performance of Beryllium Bronze
The mechanical properties of beryllium bronze alloys are closely related to the beryllium content. According to the different beryllium content, beryllium bronze alloys can be divided into high-strength, high-elasticity alloys and high-conductivity alloys. According to the product molding method, they are divided into processing alloys and casting alloys. Processing alloys are mainly used to manufacture various precision elastic components. Used in aerospace, electronics and machinery manufacturing industries.Commonly used beryllium bronze grades are QBE1.7, QBE2, QBE1.9, QBE2.5. Their chemical composition table is shown in Table 1. Zh
Beryllium bronze alloy not only has good plasticity during processing before precipitation of the strengthening phase (solid solution state), but also can prepare for subsequent aging strengthening. Its strength and hardness increase with the increase of beryllium content, but beryllium has a certain solubility in copper. When the maximum solubility of beryllium is reached, more γ phases cannot be precipitated from the saturated α solid solution in the subsequent aging process. (The γ phase is a solid solution based on a CuBe compound), so its hardness is no longer improved. Beryllium bronze parts have a high fatigue life. For example, the fatigue life of parts such as micro-switch bent pieces and contact springs processed from beryllium bronze alloys has reached more than one million times. The beryllium bronze alloy has good corrosion resistance, and the corrosion rate in seawater is extremely low ((1.1 ~ 1.4) × 10-2mm / a), and its elongation and strength hardly change after corrosion. It also has the characteristics of non-sparking and non-magnetic impact, and has important applications in military weapons and aerospace equipment; for example, its application in aviation products can ensure the magnetic cleanliness of spacecraft. In addition, beryllium bronze alloys have good thermal conductivity and solderability, and are widely used in mold manufacturing and other applications.
Preparation process of beryllium bronze material
1. Beryllium bronze alloy is generally prepared by casting process. Casting is divided into vacuum casting and non-vacuum casting; non-vacuum casting mainly includes inclined iron mold casting and flowless casting. The preparation process is firstly smelting ingredients, then casting, and finally performing subsequent processing according to demand.2. During the smelting process of beryllium bronze alloy, it is necessary to strictly control the process parameters such as smelting temperature and time, and perform slag refining and deoxidation and exhaust operations when the smelting temperature reaches 1,200 to 1,300 ° C. Casting at a temperature of 1,100 to 1,150 ° C can obtain higher quality beryllium bronze ingots [6-7]. Homogenization annealing can make the structure more uniform and the performance more stable. Beryllium bronze alloy easily reacts with oxygen in the air during the smelting process.
3. Take anti-oxidation measures in non-vacuum melting. When charcoal and phosphorous copper are used for degassing, the charcoal powder cannot be used to form a comprehensive and effective protection because the charcoal powder is burned at high temperatures. The degassing process covered with borax and broken glass and passed in argon works best; the reason is that borax and glass are under high temperature After melting, a uniform and dense protective film is formed to prevent air from entering. Smelting a beryllium bronze alloy using a vacuum device can prevent oxidation and reduce the volatilization of beryllium oxide, reducing the damage to the environment and workers' bodies.
Heat treatment process of beryllium bronze alloy
Beryllium bronze alloy relies on the precipitation of the second phase to change its properties, so heat treatment plays a decisive role in its performance. The heat treatment process is divided into two major parts, the first part is solution treatment, and the second part is aging treatment. In some areas, in order to make beryllium bronze parts have certain special properties, such as high conductivity, weldability, high corrosion resistance, wear resistance, etc., the surface treatment of beryllium bronze alloy is required. The surface plating is the most commonly used, One of the most obvious processing improvements in performance.1.Solution treatment process of beryllium bronze material
The solubility of beryllium in copper increases with increasing temperature. The solubility of beryllium at room temperature is 0.16%, its solubility at 400 ° C is 0.6%, and its solubility reaches its maximum when the temperature is 866 ° C. (2.7%), a supersaturated alpha solid solution was formed. At this time, as the temperature decreases, the beryllium content in the α solid solution gradually decreases, and the solubility curve of beryllium gradually shifts to the copper side. The beryllium bronze alloy reaches the solid solution temperature and then keeps the heat for a suitable time to allow the beryllium to fully solidify and quickly cool. The beryllium-rich phase is too late to precipitate, thereby forming a supersaturated alpha solid solution. This is the solid solution principle of beryllium bronze. In order to ensure its good comprehensive properties after aging, the parameters of solid solution treatment of beryllium bronze alloy should be controlled within a range that can make beryllium fully solid solution without grain growth. If the solution temperature is too low or the time is short, beryllium cannot be fully dissolved in the copper matrix, which will cause the precipitation strengthening ability of the alloy to be reduced. If the solution temperature is too high, the grains will be coarsened and even the grain boundaries will melt ( (Overburning), the brittleness of the material increases and the performance deteriorates.
2.Aging treatment process of beryllium bronze material
The workpiece in the solid solution state cannot be used directly, and it must have high strength, hardness, elastic modulus, elastic limit, fatigue limit and creep resistance after aging treatment. The essence of beryllium bronze gold ageing treatment is to decompose the highly dispersed γ phase from the supersaturated α solid solution at a suitable temperature, forming a dispersion strengthening effect, and improving the comprehensive mechanical properties of the material. The supersaturated solid solution decomposition process is as follows: supersaturated α solid solution → G · P zone → γγ → γ First, beryllium is enriched at the grain boundary to form a G · P · zone (segregated zone). As the aging temperature increases and the aging time increases The G · P · region grows up and transforms into an intermediate transition phase γ ′, and then further transforms into a stable γ phase. The γ phase is an intermetallic compound, which is brittle and hard. Its dispersion distribution can increase the resistance of dislocation movement, which further improves the strength and hardness of the beryllium bronze material. In addition to the element Be in the beryllium bronze alloy, other elements can also affect the mechanical properties of the beryllium bronze alloy.
Pretreatment process of beryllium bronze material
The beryllium bronze alloy parts used in the field of electronics and electronics not only require good abrasion resistance, but also have excellent electrical conductivity. To this end, the surface needs to be silver-plated [31]. In addition, beryllium bronze alloys need to be plated for aesthetic or other purposes, such as increased solderability.Beryllium bronze parts are electroplated to meet customers' pursuit of higher performance, which is an important part of their processing technology.
The beryllium bronze alloy contains elements such as beryllium, nickel, and titanium that are easily passivated, and can form an invisible oxide film even at normal temperature. During the heat treatment, even a heat treatment performed in a vacuum furnace may undergo slight oxidation. These oxide films can cause poor bonding between the substrate and the plating layer, which can cause defects such as bubbles, molting, and pitting in the coating layer. In addition, once the plating layer contains impurities such as organic matter, more micropores are prone to occur. The formation of micro-batteries under the effect of, causing more severe corrosion. The pre-plating treatment can remove the oxide film. The traditional pre-treatment process is not effective, and the acid mist will volatilize, endangering the natural environment and workers' health.