Welding Techniques

               Welding is a joining process of materials. Mostly metals or thermoplastics can be joined using this procedure.  By applying heat and pressure to the materials being joined and to the filler material, a weld pool is created and it forms a strong joint when it cooled. Picking the right technique is very important in the welding process. Wrong welding choices can cause catastrophic results. In this blog, different types of welding processes are explained.

1-) Arc Welding

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Figure 1 : Arc Welding [1]

Arc welding is the formation of a welding arc between the electrode and the material being welded (usually metal) with the usage of power supply and electrodes. When the melt cools, the weld fuses these two. Arc welding is the most popular type of welding process. It is mainly divided into two; consumable and non-consumable electrode methods.

a-) Consumable Electrode Methods

Stick Welding (Shielded Metal Arc Welding or SMAW)

It is a manual welding technique and it relies on a consumable electrode. The electrode is coated in flux. That flux is then used to lay the weld. This process is generally called stick welding because it uses welding sticks or rods. These are made up of filler material and flux. The flux is used for the protection of the molten metal of the weld. After that, the filler is used to join two pieces of metal together.

This method is generally called “archaic” nowadays. It is a very cheap method and requires minimal equipment. But, the final weld quality is not perfect. It might have porosity, shallow penetration, cracking and it is highly vulnerable to severe weather. It is generally not very durable. It is a very popular method. Mostly third world countries used this method because of the low purchasing power, people can’t afford any other methods. Stick welding method generally used in refrigeration, plumbing, automotive and construction.

MIG Welding (Gas Metal Arc Welding or GMAW)

The most second popular welding technique is MIG welding. It means “Metal Inert Gas Welding”. The process is boiling down the combining of two pieces of metal together with a wire which is connected to an electrode current. After that, the wire passes through the welding stick that is shielded by an inert gas. MIG welding is easier to use and a lower degree of precision is required compared to other welding techniques.  But, it is much more sensitive to external factors like rain, wind, and dust compared to other welding techniques. Because of that, more precise settings must be done like wire speed and voltage. The main two problems are dross and porosity. These will cause a destructive result in the structure when they are not controlled very well.

MIG welding is much easier to operate and quite simple to do. The main reason for that is the electrode is automatically fed through the torch. TIG welding operator uses both hands but the MIG welding operator can guide the welding gun across the welded area easily.

This method is mostly used in automotive repair, plumbing, construction, robotics, and the maritime industry.

Flux-Cored Arc Welding (FCAW)

Flux-Cored Arc Welding uses a special wire filled with flux and shielding gas is not always necessary. FCAW is very cheap and easy to learn, but it has limitations and results are not aesthetic compared to other welding methods. The main advantages of the method are versatility, suitability for outdoor applications, fast application, and being an inexpensive method compared to other welding methods.

Submerged Arc Welding (SAW)

Combination of ferrous steel and nickel-based alloys are done with Submerged Arc Welding. This welding process is the safest process among others. It has minimal emissions of welding fumes and arc lights. SAW requires minimal preparation, it is a quick and efficient method. It shows deep weld penetration as a result. Heat is used to build up the flux to become a conductive material and this provides a path between the electrode and the welding material. The welder is protected from UV and IR from the flux because these are the natural part of the SMAW process.

b-) Non-Consumable Electrode Methods

TIG Welding (Gas Tungsten Arc Welding or GTAW)

Tungsten Inert Gas welding is called TIG and it uses a non-consumable tungsten electrode with an inert gas (usually argon). Tungsten is used for its high purity and hardness. It gives high-quality weld. The heat is created by electric flow through a tungsten electrode in this method. This electricity creates an arc and this arc is used for melting the metal wire to obtain the weld pool. It is a very popular technique used nowadays because it offers high purity and clean weld. Most commonly used in stainless steel, magnesium, aluminum, copper and nickel applications.

This welding process is used generally in nonferrous industries, for example; manufacturing of tubing, vehicles, bicycles etc.

Electroslag welding (ESW)

 ESW is a very efficient, single-pass welding technique which is generally used for thick and nonferrous metals. The electric arc is struck by wire and fed into the weld puddle with flux. This process is applied until the slag reaches the electrode and extinguishes the arc. ESW requires a very high level of skill. It is generally used in maritime applications and aerospace industry.

Atomic Hydrogen Welding (AHW)

AHW is an older arc welding process. The torch of AHW is very hot, even enough to weld tungsten, that is highly heat resistant. This tungsten weld creates strong and cohesive weld. The basic working principle is the hydrogen molecule breakage and recombination in an explosion of heat which can reach up to 3000 degrees Celsius.

Carbon Arc Welding (CAW)

CAW is the first made arc welding process invented but it is not used today. It has been replaced by twin carbon arc welding which is less dangerous and more efficient. CAW uses a non-consumable carbon electrode. It’s working principle is simple, welding the metals together by heating them with electrode up to 3000 degrees Celsius.

Electrogas Welding (EGW)

Metal is welded with the usage of a consumable electrode. This method does not use pressure. In EGW, the arc remains struck during the process, not extinguished. EGW welding is used for generally shipbuilding and storage tank industries.

There are other types of welding processes different than arc welding. These are explained below.

2-) Gas welding

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Figure 2: Gas Welding [2]

Gas welding combines fuel gases and pure oxygen to increase the torch’s flame temperature up to 3500 degrees Celsius. It is also known as Oxyfuel welding. This welding technique is one of the oldest processes and is still used nowadays. It is generally used in pipe welding, tube welding, and repair industries.

3-) Resistance welding

Resistance welding is the application of force to adjacent surfaces and after that, applying electric current near that surface. This electric current creates intense heat. Resistance welding has many variations. These are called spot welding, seam welding, butt welding, flash welding, projection welding, and upset welding.

4-) Energy Beam Welding (EBW)

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Figure 3: Energy Beam Welding [3]

Energy Beam Welding involves firing a beam of high-velocity electrons at the welding materials in a total vacuum. The released energy coming from the electrons transforms into heat and melts the welding material. Mainly used EBW techniques are laser beam welding and electron beam welding.

5-) Solid-State Welding

Solis State Welding does not use filler material and it is done at temperatures below the melting point of the materials. This process is done with the help of time, temperature and pressure individually or with the help of all of them at the same time. In this process, metal is not melted. The most interesting thing about this process is that it is one of the oldest techniques in the world and yet, still most of the modern welding techniques are based upon the solid-state welding process.

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