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Composition and Purpose of Hard Soldering Agent for Aluminum
Hard soldering agents, also known as solder paste, are a type of flux used for solder welding processes. Hard soldering flux consists of a blend of flux components that, when combined, create a low-temperature, high-strength joining material for aluminum. The composition of this flux includes compounds and compounds of compounds for use together to attain the desired result. The purpose of hard soldering agents for aluminum is to reduce the melting temperature of the aluminum material and to increase the strength of the joint formed between two aluminium parts.
Hard soldering agents are typically mixtures of mineral and organic compounds, whose purpose is to ensure proper wetting and provide the correct chemistry for soldering aluminum. These agents are generally composed of fluxing agents and fluxing activators. Fluxing agents reduce the surface tension of the molten metal to ensure good alloy adhesion. They also keep free oxide particles from the surface layers of the aluminum, thus allowing the solder to properly wet the surface. Fluxing activators are responsible for ensuring that the oxidation products are sufficiently active to promote wetting when the solder is flowed onto the joint.
For aluminum, the most common fluxing agent is sodium fluoride. Sodium fluoride acts as a wetting agent and a flux activator and works by breaking down the oxide film on the surface of the aluminum. It is believed that the fluoride ionicity is what penetrates the alloy and makes it softer and more malleable and therefore increases the surface adhesion of the join. Along with sodium fluoride, flux compounds, such as the flux compounds ofmagnesium chloride, calcium chloride, potassium chloride, zinc chloride, tin chloride and boron chloride, are often added.
The other major component of hard soldering agents for aluminum are activators. Activators are compounds that increase the reactivity of the flux and enable it to penetrate the aluminum’s oxides more readily. Some of the most commonly employed activators in aluminum welding are aluminum, magnesium, calcium, boron, zinc, titanium and chromium, calcium chloride and calcium chromate.
Organic compounds are also used in hard soldering fluxes for aluminum. It is believed that the organic compounds used in these fluxes increase the flow rate of the metal and help to minimize surface oxidation of the aluminum. Organic compounds commonly found in this type of flux include soap, rosin and its derivatives, silicone, wax, and oils. These compounds have different functions and are added in specific proportions to act as lubricants.
The primary purpose of hard soldering agents for aluminum is to reduce the melting temperature of the aluminum material and to increase the strength of the joint formed between two aluminium parts. By reducing the melting point of the aluminum, the joint area becomes more malleable making it easier to join the two pieces. The activators are also believed to penetrate the oxide layers on the surface of the aluminum, creating a stronger bond and a more corrosion-resistant join. In addition, the moistening of the surface of the aluminum allows the solder to form a more reliable connective bond with the metal.
Overall, hard soldering agents for aluminum are an essential part of the aluminum welding process and are used to create strong and reliable welding joints. The composition and purpose of a hard soldering agent for aluminum may vary depending on the type of application, but generally, the purpose is to reduce the melting temperature of the aluminum and increase the strength of the joint formed between two metal pieces.
