Brazing is classified as high-temperature brazing (its melting point is 880-950 ° C). It is used in cases when there is a need to get a stronger connection than when using soft solders. Also the advantages of this type of soldering is the resistance to high temperatures of the compound obtained and the absence of changes in the metal structure (which is inevitable when using welding).
Brass soldering scheme using a gas burner.
Compared with other refractory solders (silver, copper-phosphorus), this alloy is the most durable and high-temperature. Due to the presence of zinc in the composition of brass has an increased resistance to the environment, slightly susceptible to corrosion. Tin, which is part of some types of brass, increases fluidity and lowers the melting point, while silicon does not allow zinc to oxidize and evaporate.
These solders are used exclusively for soldering iron, steel, copper and tin bronze (with a tin content up to 8%).
For this type of soldering does not fit the usual soldering iron. You need equipment that can heat the product to a temperature that slightly exceeds the melting point of brass (900-1000 ° C). In most cases, a variety of gas-flame burners and stoves are used. A significant drawback to the use of burners is the speed and uneven heating. Together with the property of brass in the liquid state to penetrate the grain boundaries of steel (which can cause brittle fracture under stress), this contributes to the formation of cracks. The probability of their occurrence becomes much lower when brazing steel in furnaces or in salt baths, where uniform heating of the brazed products is ensured. Re-soldering in any case increases this danger.
A borax mixed with boric acid in a 1: 1 ratio and filled with water is used as a flux (for 20 g of each component it is necessary to take 250 ml of liquid).
Brass brazing technology using a gas flame burner
Solder table for soldering.
- First of all, it is necessary to clean the joints. This is done in order to remove a resistant oxide film that the flux cannot remove. To do this, use metalwork tools (files, scrapers, needle files and hacksaws).
- Connect the parts using a vise (or in any other way).
- Fluff the soldering zone with flux, which will remove the oxide film from the metal and provide better adhesion.
- Ignite the burner, adjust the flame with a small excess of oxygen (in order to avoid oxidation of the metal surface).
- Preheat the tip of the solder and dip it into the flux (if the solder was not originally fluxed).
- Heat the product evenly at the docking point to cherry color.
- Melt the solder at the soldering point (if there is a sufficient amount of flux, it will easily spread and tighten the joint).
- Let the solder harden.
- Clean the junction.
Brazing technology in the furnace
- Clean the dock parts.
- Connect them in any way that allows you to shift the product into the oven.
- Heat in a preheated oven to cherry color.
- Without removing it from the furnace, melt the solder in the soldering zone.
- Extinguish the stove and, without touching the part, allow it to cool.
- Clean the junction.
Summing up, it can be said with confidence that brazing solders are the best option for soldering iron, steel, copper and bronze.