What is Brazing?
Basically, brazing, welding, soldering all are quite similar metal joining processes. There are some little bit differences which compel us to give different names to this metal joining processes. In this article we will discuss what is brazing, why brazing is different from soldering and welding, why to select brazing and not soldering or welding, its advantages, applications and some features as well as types.
Let us first start with definition of brazing. Brazing is a technique in which two or more similar or dissimilar metals are joined with the help of filler material. The filler metal that we use in brazing is first melted and then allowed to flow into the joint. The main point to note here is that this filler metal always has lower melting point than that of base metals. The melting temperature of filler material is above 450 oC in brazing.
Why to Choose Brazing?
We choose brazing because of some of the below mentioned key-features of brazing:
- It is the most cost-efficient process.
- The component distortion taking place is almost eliminated or we can say reduced.
- It is the most compatible for joining dissimilar material with strong joint.
- No more need of much skilled labor work.
- Thin and thick surfaces for example plates can be easily joined.
- The more complicated joints which can not be joined with welding process can be easily joined with the brazing process.
How Brazing Differs From Welding & Soldering?
Now let us consider the first part of the above question, as earlier stated, as brazing, welding, soldering all are similar metal joining processes. Then why we choose brazing over soldering and welding? In brazing there is no melting of base metals where in case of welding this melting takes place. In short, in brazing melting of filler metal takes place and not of the parent metal. And if we talk about soldering, then definitely brazing gives us much stronger joints than soldering. Also, the temperature conditions requirement is also high in brazing compare to that of soldering.
These are the most important components in brazing:
1. Flux: A flux plays an important role in the overall brazing process. As brazing usually takes place in open environment so there are many chances of the development of oxides which are very harmful for brazing. So in order to prevent flux formation, we use a flux like a borax. The most important part to take in consideration is that this flux must be chemically suitable for both the filler metal as well as base metal.
2. Base metal or joining elements: The joining parts may be similar or dissimilar.
3. Heating sources for brazing:
- Torch: It is a heating source consist of fuel gas flame. The gases which are included in this are acetylene, hydrogen.
- Induction heating: Electric coils are used in this for heating purpose. It is used while handling copper and silver alloys.
- Vacuum furnace: Basically, this type of furnace consists of electrically heated elements itself. When the base metal comes in surrounding of vacuum furnace, then the filler metal automatically gets heated and thus it melts.
4. Filler material: Filler material used in brazing are usually made up of more than 3 or more metals. These filler material is applied in brazing in various forms such as powder, powder, paste. Copper, silver, brass, bronze, aluminium-silicon are some of the various filler alloys used in brazing.
How Brazing Process Works?
In brazing the filler metal has lower melting point than parent metal. So first of all, this filler metal is heated and as a consequence of this heating, this filler metal starts to melt. This filler metal then allowed to flow into the joint formed by the workpieces. At the same time this filler metal is protected by a flux. As this filler metal is in liquid form starts to flow over parent metals (wetting takes place) and it is then slightly cooled to form the solid and clear joint.
For Better Explanation Watch the Video Given Below:
As we know that many heating methods are used in to complete brazing process. The variety of heating sources are used according to the situation. There are many types of brazing techniques which are available and the basis of categorization of these techniques is the heating method we used for brazing. In short, on the basis of heating methods used following are some of the brazing techniques at a glance:
1. Torch Brazing:
Torch brazing is the most common type of brazing technique and is one of the most commonly used brazing processes. Basically, it is done in air or open environment. The torches used are oxyfuel gas torches. Torch brazing is further classified as manual, automated and machine torch brazing. Propane or acetylene are the two fuels that are used in torch brazing.
Manual torch brazing: This is one of the easy methods of torch brazing as it requires nothing but a torch and simply two or more tanks. This is the most flexible as well as easily applicable torch brazing method. Also, it is portable as well as cost effective process and massively used in small scale applications.
2. Silver Brazing
Silver brazing is often called as hard soldering. One important thing in silver brazing that you must know is that the strength of the joint formed in this process is directly dependent on the thin film of filler material. The silver content varies from 5-50% that’s why it is called as silver brazing. Remaining content is composed of mainly copper or zinc. Silver brazing has its application mostly in jewellery and it is a quite expensive brazing process.
3. Vacuum Brazing
As the name suggests this type of brazing is done in vacuum. As it is done in vacuum it results in stronger as well as cleaner joints. In vacuum brazing furnace, controlled temperature is maintained inside the furnace. Due to this, there is a uniform heating of all workpieces takes place and thus multiple joints can be designed at a single time. Vacuum brazing is mostly used for alloys like stainless steel, carbon steel.
4. Induction Brazing
In induction brazing, the metal parts that are to be joined are placed inside an induction coil and a high frequency electrical current is passed through it. As current gets induced on the surfaces of these metal parts, the resistance of these metal parts opposes the inducing current. As a result of this heat is developed and consequently metal parts gets heated. Thus, melting of filer material takes place. Some of the benefits of induction brazing are:
- It is a very efficient and fast process.
- It requires very less amount of energy and reduces thermal distortion and is the most easy to implement brazing process.
5. Dip Brazing
It is mostly compatible with the aluminium as no oxidation takes place due to absence of air. This type of brazing has its application in aerospace industry as dip brazed parts are used in heat transfer.
Precautions that you must take while Brazing process:
- As brazing is one of the efficient metal joining processes, you must take into consideration following precautions in order to complete brazing smoothly.
- Use a flux in proper amount to prevent oxidation.
- Do not overheat and also provide proper temperature with appropriate atmosphere.
- Wear proper gloves, goggles and also avoid direct contact with the work place.
- Keep good ventilation and do brazing at sufficient places rather than small or unfavorable places.
In this article we have learnt about what is brazing, its working and types and what is the precautions that should be taken while doing brazing. If you found anything missing or incorrect than comments. If this looks you informative than don’t forget to like and share it. Thanks in advance.