Brazing

**Brazing** is a common metal joining process, falling between welding and soldering. It **does not melt the base metal, only the filler material**, utilizing capillary action to allow the filler material to fill the joint and form a strong connection.

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## I. What is Brazing? * Heating temperature: **Above 450℃**
* **The base material does not melt**, only the brazing filler metal melts.
* The brazing filler metal flows, wets, and solidifies in the joint gap to complete the connection.
* High joint strength, minimal deformation, and clean appearance.

📌 Difference from welding:

* Welding: Base material melts
* Brazing: Base material does not melt

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## II. Main Applications of Brazing

Brazing is suitable for **precision, thin parts, and multi-material connections**:

### 1️⃣ Refrigeration and Air Conditioning

* Copper tube—copper tube
* Copper tube—brass
👉 Air conditioners, refrigerators, condensers, evaporators

### 2️⃣ Mechanical Manufacturing

* Tools, carbide tool tips
* Gears, small parts

### 3️⃣ Electronics and Electrical Appliances

* Relays, terminals
* Motor windings, conductive components

### 4️⃣ Automotive and Aerospace

* Heat exchangers
* Pipelines, oil lines, hydraulic parts

### 5️⃣ Jewelry and Crafts

* Connection of gold, silver, and copper products

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## III. Common Brazing Filler Materials

Filler material selection depends on **base material + operating temperature + strength requirements**:

### 🔹 1. Silver-based brazing filler metal (most commonly used)

* Composition: Ag-Cu-Zn / Ag-Cu
* Melting point: **620–780℃**
* Features: Good fluidity, high strength, wide range of applications
* Suitable for:

* Copper, brass, stainless steel, cemented carbide

✔ Commonly used in the refrigeration industry

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### 🔹 2. Copper-based brazing filler metal

* Composition: Cu / Cu-P
* Melting point: **710–900℃**
* Features: High strength, high temperature resistance, low price
* Suitable for:

* Copper—copper
* Copper—brass (some require flux)

⚠ Not suitable for stainless steel

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### 🔹 3. Aluminum-based brazing filler metal

* Composition: Al-Si Melting point: **560–620℃**
* Features: Specifically for aluminum and aluminum alloys
* Suitable for:

* Aluminum-aluminum
* Aluminum heat exchangers

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### 🔹 4. Nickel-based brazing filler metal

* Composition: Ni-Cr-B-Si
* Melting point: **900–1100℃**
* Features: High temperature resistance, corrosion resistance
* Suitable for:

* Stainless steel
* High-temperature alloys, aerospace components

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## IV. When to choose brazing?

✔ Thin-walled parts
✔ Precision parts
✔ When melting of the base metal is not allowed
✔ Joining dissimilar metals
✔ High requirements for appearance and dimensions