What Is Aluminum Bronze?
The copper-based alloy with aluminum as the main alloying element is aluminum bronze containing iron and manganese, which is a high-strength heat-resistant bronze.
The Chinese name aluminum bronze constitutes the main material of aluminum, and other elements such as iron, manganese, nickel, etc. are used for screw, nut, copper sleeve, sealing ring, etc.
The aluminum content generally does not exceed 11.5%, and sometimes an appropriate amount of iron, nickel, manganese and other elements are added to further improve the performance. Aluminum bronze can be strengthened by heat treatment, its strength is higher than tin bronze, and its high temperature oxidation resistance is also better.
It has high strength and good wear resistance. It is used for high-strength screws, nuts, copper sleeves, sealing rings, etc., and wear-resistant parts. The most prominent feature is its good wear resistance.
Because aluminum bronze containing iron and manganese elements has high strength and wear resistance, it can increase the hardness after quenching and tempering, and has good high temperature corrosion resistance and oxidation resistance. Corrosion resistance in the atmosphere, fresh water and sea water Very good, machinability is acceptable, welding is not easy to brazing, good pressure processing in hot state. my country has energy production.
Aluminum bronze has many excellent properties. Aluminum bronze has high strength, hardness and wear resistance, and is often used to make gear blanks, threads and other parts. Aluminum bronze has good corrosion resistance, so it can be used to manufacture corrosion-resistant parts such as propellers and valves.
Aluminum bronze does not produce sparks under impact, and can be used to make non-sparking tool materials. It has excellent thermal conductivity and stable rigidity. As a mold material, it has the advantages of not sticking to the mold and scratching the workpiece when stretching and calendering the stainless steel plate heat exchanger. It has become a new type of mold material.
Aluminum bronze has a shape memory effect and has been developed as a shape memory alloy. The price of aluminum bronze alloy is relatively cheap, and it has become a partial substitute for some expensive metal materials, such as replacing tin bronze, stainless steel, and nickel-based alloys. It is precisely because of its excellent characteristics that aluminum bronze has become more and more popular and plays an important role in civil and military industries.
Commonly used domestic brands
QAL7: It has high strength and elasticity, high corrosion resistance in the atmosphere, fresh water, sea water and some acids. It can be processed by hot and cold pressure, and can be welded by electric welding and gas welding. It is not easy to braze.
Purpose: Other elastic components that require corrosion resistance for the spring box.
QAL9-4: It has high strength, good friction reduction and good corrosion resistance. It can be hot-processed and welded, but it is not easy to braze.
Uses: high-strength, wear-resistant parts, such as bearings, bushings, gears, turbines, etc.; it can also manufacture nozzles, flanges, flat rocker arms, brackets, etc.
QAL10-4-4: It has stable mechanical properties below 400°C, good anti-friction properties, good corrosion resistance in the atmosphere, fresh water, and sea water. It can be hot processed and welded, but it is not easy to braze.
Purpose: High-strength wear-resistant parts box for parts that work below 400°C, such as bearings, shaft sleeves, gears, spherical seats, nuts, flanges, etc.
Influence of chemical composition
The influence of chemical composition on the structure and properties of aluminum bronze has always been one of the hotspots of concern. First of all, there is no clear definition of the effect of the chemical composition on the alloy. For example, when iron is added to aluminum bronze, it generally has the function of refining the grain, reducing the “spontaneous tempering brittleness”, and improving the mechanical properties. However, when the iron content is high, the iron will be precipitated as Fe3Al2 compounds, which will change the mechanical properties of the alloy. Bad, so the iron content should not exceed 5%.
There is also zinc element. Many studies believe that it can improve the plasticity of the metal after solid solution with the base metal, and some studies believe that it is an impurity element.
It can be seen from this that the role of alloying elements cannot be generalized. It is generally believed that adding an appropriate amount of alloying elements can improve the mechanical properties of the alloy, such as adding an appropriate amount of iron to form aluminum-iron bronze, adding manganese to form aluminum-manganese bronze, and adding nickel to form aluminum-nickel bronze.
Secondly, there is no clear definition of the requirements for the content of impurity elements. It is precisely because of the change of chemical composition that the types and applications of aluminum bronze are different. Researchers should continue to study the influence and mechanism of chemical composition to further expand the scope of application of aluminum bronze.
Some strengthening processes are usually used to improve the structure of aluminum bronze alloy to achieve the required properties and process performance.
The main methods of strengthening aluminum bronze alloys include solid solution strengthening, fine grain strengthening, and aging strengthening. Solid solution strengthening is the process of heating the alloy to the full or maximum dissolution of alloying elements such as aluminum and manganese into the copper matrix to form a saturated or supersaturated solid solution, and then quenching to room temperature to obtain a supersaturated solid solution.
However, this supersaturated solid solution will decompose at room temperature or higher temperature to precipitate the second phase. This precipitation can significantly increase the strength and hardness of the alloy, which is aging strengthening. Solid solution and aging are often used in conjunction to improve the properties of aluminum bronze alloys.
This mainly refers to aluminum bronze with aluminum content above 11.5% and below 15%. The composition of elements other than aluminum is not much different from ordinary aluminum bronze. Because of the difference in aluminum content, special aluminum bronze has a higher strength than alloy steel and a hardness close to that of alloy steel. It is widely used in force structure parts, transmission parts, etc.
In addition, because of its good corrosion resistance, pressure resistance and wear resistance, it is also used in the drive shaft gear of high-speed trains. China does not produce energy.
Key Points of Aluminum Bronze Welding
The main difficulty in welding aluminum bronze is the oxidation of aluminum, which produces a dense and refractory Al2O3 film covering the surface of the droplet and molten pool.
Defects such as slag inclusion, porosity, and non-fusion are easy to occur in the weld. Removal of aluminum oxide and prevention of aluminum oxidation have become the key to the success or failure of welding aluminum bronze.
In addition, single-phase aluminum bronze with w(Al)<7% has hot brittleness, which is prone to cracks in the heat-affected zone and is difficult to weld. Single-phase alloys and dual-phase alloys with w(A1)≥7% can be welded by taking some anti-cracking measures.
Gas welding is generally not recommended because it is difficult to completely eliminate the harmful effects of aluminum oxide. If gas welding is necessary, the welding wire and welding groove must be thoroughly cleaned, and fluxes containing chloride and fluoride salts must be used. Strictly adopt measures such as neutral flame.
Electrode arc welding is generally used for welding repair of aluminum bronze forgings or castings. Use ECuAl-c (ie T237) electrode. Except for thin parts (≤3mm), a 70°～90° V-shaped groove is required; thin parts are often not preheated. For alloys with w(Al)<10%, the preheating and interlayer temperature should not exceed 150°C. For welding aluminum bronze with an aluminum content of 10% to 13%, the recommended preheating and interlayer temperature for thick workpieces is about 260℃, and the weldments should be cooled quickly. Adopt DC reverse connection, short arc and narrow bead welding. During multi-layer welding, slag must be thoroughly removed between layers.