Brazing is a metal joining technique that uses a metal filler (usually an alloy containing elements such as copper, silver, or aluminum) to join two metal workpieces at high temperatures. Unlike welding, the base metal does not melt during brazing; instead, the molten filler is applied to the joint between the metals, forming a strong connection.
1. Basic Principles of Brazing
1.1 Heating: The metal workpieces to be joined are heated to a specific temperature (usually below the melting point of the base metal, typically between 450°C and 1200°C), causing the filler metal to melt while keeping the base metal in a solid state.
Melting Filler: When the filler metal melts, it flows into the seam between the two metal workpieces and fills the gaps uniformly due to capillary action.
1.2 Cooling: As the temperature decreases, the filler metal solidifies, forming a strong metal bond. The final joint is very strong, with good mechanical strength, corrosion resistance, and electrical conductivity.
2. Differences Between Brazing and Other Joining Methods
2.1 Compared with welding: Welding involves partially melting the base metal before fusing it, while brazing fills the joint with molten filler metal, keeping the base metal solid.
2.2 Compared with riveting and screwing: Brazing creates a solid joint through molten filler metal, while riveting and screwing are mechanical methods that do not involve melting.
3. Types of Brazing
3.1 Soft Brazing (Low-temperature): Conducted below 450°C, typically using low-melting-point fillers such as lead-tin alloys. It is used for applications requiring lower temperatures.
3.2 Hard Brazing (High-temperature): Conducted at temperatures above 450°C, using fillers such as copper, silver, or nickel alloys. It is suitable for joints requiring higher strength and resistance to high temperatures.
4. Advantages
- No high temperatures required: I requires lower temperatures compared to welding, preventing excessive thermal effects on the base metal.
- Applicable to different metals: It can be used to join various types of metals, including stainless steel, copper, and aluminum.
- Good joint strength and conductivity: Brazed joints typically offer high strength, corrosion resistance, and good electrical conductivity.
5. Disadvantages
- High operational environment requirements: The process requires careful control of temperature, pressure, and atmosphere to avoid oxidation and contamination.
- Not suitable for large components: Brazing large components can be complex and costly.
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