The Function of Flux：
Flux is an indispensable 'unsung hero' in brazing. It is like a 'cleaner + bodyguard' for metal connections, with three core missions:
1. Powerful Decontamination: After melting, it dissolves the oxide film on the surface of the base metal (such as rust and patina on copper), enabling the brazing filler metal to have 'intimate contact' with the metal.
2. Isolation and Protection: It covers the metal surface to prevent oxygen from 'causing damage' at high temperatures and avoids secondary oxidation.
3. Paving the Way: It reduces the surface tension of the liquid brazing filler metal. Just like a 'lubricant', it helps the brazing filler metal flow evenly and fill the gaps.
Types of Flux and Their Applicable Scenarios
According to the composition and application, fluxes can be divided into four categories, which are suitable for different scene requirements:
|
Types |
Representative components |
Features |
Applicable scenarios |
|
Fluoride Flux |
Lithium fluoride (KBF4) |
Strong activity, specifically effective against the "stubborn oxide film" of stainless steel |
Brazing of stainless steel and superalloys |
|
Borax-based Flux |
Borax (Na₂B₄O₇) |
High cost performance, suitable for copper and iron |
Brazing of red copper tubes, cutting tools and cast iron parts |
|
Organic Soft Flux |
Rosin, Hydrazine hydrochloride |
Low temperature and environmentally friendly, with no corrosive residues |
Electronic circuit boards, gold and silver jewelry |
|
Special Flux |
Aluminum brazing flux (containing chlorides) |
Specifically solves the brazing problems of special metals such as aluminum and nickel |
Aluminum alloy, nickel-based superalloy |
How to Select Flux?
|
Consider the base material |
Consider the brazing temperature |
Consider the process requirements |
|
- Stainless steel → Fluoride flux (such as FB101) |
- For low-temperature environments (<450℃) → Organic brazing fluxes (such as rosin) |
- For easy cleaning → Water-soluble brazing flux (Just rinse with hot water after welding.) - For high strength → High-activity fluoride brazing flux - For environmental protection requirements → Lead-free and halogen-free brazing flux |
The Forms of Flux and Its Usage Techniques
Paste - like
It can be accurately applied and is suitable for complex joints (such as threads and grooves).
Powder
It is brushed after being mixed with ethanol, which is economical and practical.
Pre - coated
The brazing flux is pre - coated on the surface of the filler metal to simplify the operation (such as flux - cored wire).
Spray - type
It can quickly cover large - area welds on automated production lines.
Precautions for Using Flux
Safety first
Fluoride brazing flux will release harmful gases when heated. It is necessary to ensure good ventilation and wear protective masks!
Appropriate usage amount
If the amount is too small, the oxide film cannot be cleaned thoroughly, and if it is too much, it is likely to leave residues that cause corrosion (the recommended thickness is 0.1–0.3mm).
Clean in a timely manner
Use hot water or special cleaning agents to remove the residues after welding (sandblasting can be used for hard residues).
Store in a sealed way
Borax is prone to absorbing moisture and caking, and fluoride brazing flux needs to be protected from light and moisture.
Summary in One Sentence
Flux is the 'unsung hero' behind the success of brazing - it clears obstacles, ensures purity, and aids in the flow. By choosing the right type, metal connections can be achieved with twice the result for half the effort!
Hot Tags: brazing flux, China brazing flux manufacturers, suppliers, factory, accessories, Brazing Filler Metal, Brazing Flux, Customized High End Inductor, Dotting Machine, Special Water Chiller For Induction Heating
