In this article we’ll learn in-depth about Electroslag Welding, how it’s works, its applications, benefits and so much more in detail.
What Is Electroslag Welding?
The Electroslag Welding process can be explained as a combination of Arc welding and Resistance welding. This is because an arc is created at the very beginning of the process and then the weld is produced by the resistance offered by the Flux used. This process of welding is widely used in many heavy industries. Electroslag welding is used for welding heavy metallic parts together.
Why Is Electroslag Welding Used?
It is quite efficient to weld small metallic pieces using traditional welding methods But when it comes to welding materials that are thicker than 30mm, electro slag welding can be a suitable replacement. This process of welding can be used to weld materials ranging from 30mm to 300mm. Electroslag welding is a single pass welding process, hence it is very convenient to weld thick materials.
History Of Electroslag Welding
It was in the year 1940 when the first patented electroslag welding process was published in the name of Robert K Hopkins. It was 1959 until electroslag welding was used effectively by General Motors Electromotive for the fabrication of engine frames. On 7 January 1994 when the Northridge earthquake occurred, it provided a natural check for the welds in that area. It was evident that all the other welds failed while electroslag weld being single pass weld survived. Though this process was banned for several applications due to the excessive heat produced during the process forms the Brittle and coarse-grained weld.
Elements And Construction Of Electroslag Welding
The construction of electroslag welding is not very complex. The base plate acts as a positive electrode and the filler wire acts as a negative electrode. Two workpieces to be joined are kept on the base plate. The filler wire is inserted in the cavity from the top and is perpendicular to the base plate. Flux is also fed into the cavity using a hopper. A guide tube is used to guide the filler wire to the correct position.
The important elements involved in electroslag welding equipment.
DC power supply:
A DC power supply is used in the case of electroslag welding. The potential difference created by the power source ranges from 40V-50V. Current depends upon the thickness of the workpiece to be welded, generally, the current supply is 600A or more.
The base plate acts as one of the electrodes used in electroslag welding. One terminal from the power supply is connected to the base plate. It is also known as the starter plate. It also supports the whole setup of electroslag welding.
Workpieces are the metals to be welded together, the two workpieces are held vertically in an electroslag welding setup.
The welding actions take place in a vertical direction.
A filler wire is used as another electrode, it is used to create an arc while coming in contact with the flux. There is a continuous supply of filler wire used in the electroslag welding process. The filler wire is guided to the correct position using a consumable guide tube. The carbon percentage in the filler wire is less than that of base metal this prevents cracking of the weld due to high carbon percentage.
Flux and slag:
Flux may be said to be the most important filler material used in electroslag welding. Flux is added in the form of powder and then is melted because of the arc produced. Slag is the waste material that floats over the Flux. The flux used in electroslag welding must have the following properties.
- It must transform electrical energy to heat energy in its molten state.
- It must protect the weld from atmospheric gases
- It must conduct the electricity at the same time and must offer sufficient resistance to generate heat.
Working of Electroslag Welding
Electroslag welding works on the principle of joining two metals with heat generation between them due to arc and electric resistance. The arc is first created by applying a potential difference between the base and the electrode. This arc melts the filler and fills the cavity. Then the filler is melted due to the resistance offered by the slag. Now the electrode wire and filler melt to form a filler weld in the vertical direction between the workpieces.
- Initially, the flux is fed inside the cavity then the power supply is started.
- When the filler wire touches the base plate through the flux, an arc is generated due to a short circuit between the filler electrode and the base plate.
- This arc produces heat which is sufficient to melt the flux. This is the principle of arc welding used in electroslag welding.
- After the arc is produced and the flux is melted the weld progresses in the upward direction.
- More flux is added from the top, now the heat generation takes place due to the resistance offered by the molten flux and the process looks like resistance welding.
- This helps in fusing the walls of the workpiece and the consumable wire. Hence a weld is formed between the two workpieces.
- The weld formed is due to the molten filler wire, molten flux as well as fusing of the walls of the workpiece.
NOTE: There must be a continuous supply of filler wire and flux till the cavity is filled.
Advantages Of Electroslag Welding
- Material thickness:
One of the major advantages of electroslag welding is that it can be used to weld thick workpieces together. This is not possible using conventional welding methods. Workpieces ranging from 30mm to 300mm can be welded using electroslag welding. It can be used in heavy manufacturing industries where the strength of the weld is the key concern.
- High deposition rate:
The deposition rate in a welding process can be termed as the mass of metal deposited in the cavity with respect to time. It is generally calculated in gm/min. In the case of electroslag slag welding, the deposition rate is about 330gm/min which is much more than traditional welding methods.
- Minimum cold cracking:
cold cracking is a phenomenon because of which cracks are developed on the welds due to sudden cooling of the welded areas. In the case of electroslag welding, the welds do not cool suddenly, preventing then cold cracking on the welded areas.
- High productivity:
Productivity is an important aspect while working in any manufacturing industry. The process of electroslag welding can be made semi-automatic which may help in faster welding of the workpiece.
- Minimum slag:
Slag is the waste product generated during the process of welding. Slag may weaken the welding areas. Electroslag welding promotes low slag deposition than traditional welding methods. The slag deposition is less than 5% in the case of electroslag welding.
Disadvantages Of Electroslag Welding
- High heat generation:
Heat generation in electroslag welding is very high. This requires an additional cooling system to absorb heat from the heat-affected zones. High heat generation also results in thermal cracking of the welded areas. This may also decrease the toughness of the weld.
- Restricted position:
Electroslag welding process takes place only in the vertical direction. Horizontal welding is not possible as the molten metal pool is large and won’t spread evenly.
- Large grain size:
The grain size of the welds is large in the case of electroslag welding. This results in less compact welds. This is one of the major disadvantages of electroslag welding.
- Unsuitable for cylindrical objects:
Electroslag welding is not a suitable process for welding cylindrical objects. This is due to the curved surface area of the cylinders. The molten flux will flow away from the workpiece due to the curved surface resulting in the improper and weak weld.
- High cost:
The overall cost of the equipment and the cost of running both are high for electroslag welding when compared to traditional welding methods. The filler wire and flux requirement are much higher than other welding processes. This is a major economical disadvantage of electroslag welding.
Applications Of Electroslag Welding
- As mentioned earlier in the advantages of electroslag welding that it can be used to weld heavy components. Hence electroslag welding can be used to weld large forging and casting parts to create a composite structure.
- It is used for welding large ships, as the components of ships are large and heavy it provides strong and durable welds to many parts of a ship.
- Electroslag welding is widely used in the welding of large pressure vessels and large tanks to provide a strong weld.
- This method of welding was also used for the welding of construction steel during the late 90s.
This is all about Electroslag Welding. Let me know in the comment section if you have any doubts regarding this session. I will get back to you within 24 hours.