Basic principles of brazing

Brazing is a crucial link in today's industrial development and is a decisive production node among many industries. As a company using brazing technology, it should have a certain understanding of it. We provide our customers with consulting and training on brazing technology. By browsing our website, you will have a shallow to deep understanding of brazing technology and find the right method for you. At the same time, if you have any questions, please contact us in time.

While striving to promote our advanced industrial application experience, Guguang Company is also committed to the research of technical brazing technology, and strives to industrialize the results made by our laboratory and bring to the market, providing customers with better products and services. We have joined hands with many scientific research institutions to improve ourselves while providing more application verification experience for the scientific research field.  

Basic principles of brazing:

concept  

Simply put, brazing is to use the melting of a third-party metal material (brazing material) to connect another metal material (primary material). The melted solder may form an alloy on the contact surface with the welded metal material, which is solidly connected together. The characteristic of brazing is that the material that needs to be welded has no shape changes and the sealing at the link is not porous. The key point of brazing technology is that the melting point of the third-party metal (solder) must be lower than that of the base material, and the third-party metal must be able to flow smoothly and completely fill in the welding gap after melting. This seems simple, but it is difficult to implement. Two of the major difficulties are particularly important.  

Difficulty 1. The surface of metal materials will form an oxide film, especially in high-temperature aerobic environment, which will form a very thick oxide layer. The melting point of this oxide layer reaches several thousand degrees, which is far higher than the melting point of the metal. It wraps around the melted metal, making it impossible for the metal to flow at all. Moreover, the oxide film on the surface of the base material is often difficult to remove, resulting in the inability to form the alloy and the welding is unsuccessful. 

Difficulty 2: Even if the metal material has been separated from the oxide film, it will not flow on the base material, and even if the oxide film on the base material does not exist, the situation will not improve. The melted metal material exists on the metal surface of the base material but does not spread along the surface, but instead forms a spherical shape and stabilizes at a point. This is mainly because the concentrated metals often do not wettability each other, or even if there is a certain wettability of each other, it is not enough to fill the weld, and a spherical shape is formed under the action of integral surface tension.

To solve the above two major problems, we must introduce another material, that is, flux. Flux, also known as brazing additives, contains a variety of chemical components and has various shapes and components and different working principles for different situations. Its main function is to remove the oxide film on the metal surface, break the surface tension of the metal liquid, increase wettability, etc. Its presence makes brazing possible. It is an indispensable material in the brazing process and a material with high technical content in the field of brazing. Reasonable selection of brazing additives can not only make the welding process simple, fast and improve efficiency, but also reduce the amount of solder and save costs while ensuring the quality of the weld.  

Therefore, brazing often consists of the following parts: pre-welding treatment, heating, flux coating, adding brazing, cooling, and post-welding treatment. Each step is very critical. If any step is not handled well, it may cause unsatisfactory welding results or even lead to welding failure.  

The development of Guguang Company began with the production of brazing additives. Through efforts, it began to launch many excellent brazing additives to the market in the late 1990s, becoming a well-known brand in the industry. Entering the 21st century, Guguang Company began to research and develop new types of brazing materials based on the experience of producing brazing additives, improve the formula of brazing materials, and improve the coordination between brazing materials and flux materials, and launched a number of classic combinations.  

Selection of brazing materials

Guguang Company has met customers over the years when choosing brazing materials, they often look for the brazing materials they want to use according to industry experience and peer recommendations. This is of course a simple method, but here we provide a guide to finding materials from scratch, so that everyone can understand the principle of choice, and get rid of the fixed mindset, which may have unexpected effects. We also recommend that merchants who are using some kind of brazing material re-examine their choices.  

The selection of brazing materials determines the result of brazing. First of all, the temperature. The melting temperature relationship of the material must be: the base material is greater than the solder material, and the solder material is greater than the flux. This is relatively simple, as long as you know the base material that needs to be welded, you can position it smoothly.  

After determining the material selection range, the selection of brazing materials becomes much more difficult, and there are many more factors to be considered, such as cost, quality, appearance, production efficiency, laws and regulations. We recommend that when choosing, first consider the quality requirements of the product and what environment to use after the product is sold. This will greatly affect the selection of brazing materials. For example, if the product has long-term vibration load when used, a brazing material with good toughness should be selected. If the product is loaded with current when used, you need to choose a material with good conductivity. If the product is used in a corrosive environment, then a corrosion-like material should be selected, and the material metal and the base material will not cause electrochemical corrosion. For example, are there any legal and regulatory restrictions in the market in which the product materials are sold? This also has a decisive impact on the choice, such as the toxicity of the material, the legality of the material metal, the strategy, etc.  

After that, merchants should choose brazing materials from the perspective of considering production efficiency. When choosing solder, what kind of solder is used has become an important issue. Manufacturers of welding pipes can choose to be prefabricated into rings, manufacturers of flat welding interfaces can choose to be prefabricated into sheets, manufacturers with many and small welding ports can choose to pre-coat the solder material on the welding port, and manufacturers with complex welding ports can choose powdered solder material, etc. When it comes to choosing flux, manufacturers have more ways to choose. You can choose powder, paste, you can choose to clean after welding, you can choose to have no need to clean after welding, you can choose to have the core solder material wrapped in the solder material or the skin solder material applied to the surface, or you can choose to have the solder powder evenly mixed with the flux, etc. These choices directly affect the efficiency of brazing.  

Finally, we must choose brazing materials from the perspective of cost control. Guguang Company has been working hard to correct a misunderstanding among Chinese companies, which is its quick success in cost control. Brazing materials are different from other materials and are used in a single product in a very small amount. We know that the dosage of brazing and flux used for each brazing is small, and in most products, the cost of brazing material is almost negligible in the total cost value. Although the price of centralized procurement of a batch of materials is also very objective, the cost of sharing a single workpiece is minimal. Even if the price of brazing materials doubles, there is no obvious change in cost ratio. However, the impact of brazing materials on quality in product production is of great importance. Choosing the right, high-quality materials and brazing services, as well as the correct process, can guarantee the quality of the product. Therefore, we recommend that when choosing welding materials, manufacturers should not just look at the price. Whether there are advantages in quality and whether the stability of quality is guaranteed is the important choice condition.  

Brazing heating method

There are many ways to heat brazing, including flame heating gas welding, high-frequency welding (induction welding) heated by high-frequency welding machines, in-furnace welding by brazing furnace heating, and friction welding, salt bath welding and other methods. Choosing a suitable brazing heating method is also an important issue. Customers can make decisions through factors such as processing workpiece shape, cost investment, work efficiency, and operating environment.  

Flame-heated gas welding 

Gas welding is a common heating method that heats through a pipe, mixes combustible gas through a welding torch, mixes with air or oxygen through a welding torch, and burns violently at the nozzle of the welding torch. Its advantage is that its startup capital is small and its equipment is simple. The obvious disadvantage is that it has a high degree of dependence on welder technology, is relatively low in efficiency, and is difficult to achieve automation.  

High-frequency welding heated by high-frequency welding machine  

The method of heating the workpiece into the middle of the heating ring of the high-frequency welding machine, with power-up and cooling water, and heating it using the principle of electromagnetic induction is called high-frequency welding. This method has a very fast heating speed, especially suitable for welding welded parts with small welding volume and uniform specifications. High-frequency welding has distinct advantages, fast heating speed, low requirements for welders, stable processes and high efficiency. His shortcomings are also prominent. He cannot weld welds with more dense welds, and since the workpiece must be placed in the middle of the heating ring, there are relatively strict requirements on the size and shape of the workpiece.  

In-furnace welding for brazing furnace heating  

The method of heating and brazing of workpieces coated with brazing materials and fluxes using a brazing furnace is called in-furnace welding. Brazing furnaces welded in furnaces are expensive, ranging from tens of thousands to millions. However, the brazing advantage of this method is very outstanding. The temperature control system of the brazing furnace can be used to stabilize the temperature, so that the product quality is stable and the defective rate is greatly reduced. At the same time, the melting point temperature difference between the solder and the base material can be appropriately reduced.