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Sub Arc Welding: A Complete Overview

I often hear the term Sub arc welding may seem simple, but it is actually a complex skill that takes a lot of training and practice to master. It is used widely to make metal structures and parts in many industries, including construction, manufacturing, and the oil and gas industries.

SAW, or sub arc welding, uses a continuously fed electrode to bond metal. It moves quickly and has the potential to accomplish both rapid deposition rates and deep penetration. Fabricators who work with flat plates, girth welds in pipes, and spiral pipe mills use this technology to help them get the most out of their time and work.

There are many different types of arc welding, and each has its own advantages and disadvantages. One particularly common type of arc welding is sub-arc welding. In this article, we will take a closer look at what sub-arc welding is, how it works, and the benefits it offers.

A picture of Sub arc welding

What Is “Sub-Arc Welding”?

When sub arc welding, a continuously fed electrode is used to create an arc between the metal workpiece and the electrode. This arc melts the base metal’s surface and the electrode’s end, which forms the molten used to bond the workpieces. When this occurs, a blanket of powdered flux generates a protective gas shield and slag.

While sub arc welding can be used on a variety of metals, it is most commonly used on stainless steel and mild steel. When used on these types of metals, sub-arc welding provides a strong, durable weld that is resistant to corrosion. As a result, it is an excellent choice for use in applications where strength and durability are required.

How Does Sub Arc Welding Work?

In addition to requiring a continuous supply of flux powder, sub-arc welding necessitates an ongoing collection of consumable wire electrodes. The wire electrode could be in the form of either solid or cored continuously fed wire.

To ensure that the arc is always covered in a substantial layer of flux, flux powder is consistently applied to the weld length just before the start of the welding process.

The SAW technology is suited for building big pipelines and pressure tanks because it allows for substantial butt welds to be performed both longitudinally and circumferentially.

Due to the high fluidity of the molten weld pool and slag, submerged arc welding is performed in a flat position. This ensures that a thick flux layer is maintained throughout the welding process.

Tools and Machines Used in Sub Arc Welding

The following essential pieces of gear are required for sub arc welding:

  • Machine for welding or power supply
  • A welding head can be operated automatically or semi-automatically, depending on the user’s preference.
  • Unit for the controlled feeding of the electrode wire.
  • A flux feeder is built into the flux hopper.
  • A measurement of the flux recovery unit.
  • Carriage for travel.
  • To name a few examples: cable set, ground clamp, chipping hammer, wire brush, etc.
A picture of welding machine

There Are Different Kinds Of Sub Arc Welding

The sub arc welding can be performed in three distinct modes, which are as follows:

  • Semi-automatic setting.
  • Automatic setting.
  • Machine setting.

1. The semi-automatic setting

This process is carried out with the assistance of a hand-held semiautomatic weld head, which is responsible for receiving the wire electrode and the flux powder (either through gravity from a hopper located on the welding head or through a hose that is linked to the welding head).

To properly feed the wire electrode, a wire feeder and a copper contact tube will need to be utilized. The wire electrode, current, arc voltage, and travel speed must be set appropriately to produce a quality weld. This is because the welder cannot see either the welding arc or the weld pool.

The welding head may be fitted with a start switch, which will initiate the welding process; alternatively, the system may be pre-programmed to create the feeding of the flux as soon as the electrode comes into contact with the piece of work being welded.

2. The automatic setting

This method involves the utilization of very sophisticated machinery, and the welding process can be carried out without the participation of a welder in any capacity whatsoever. Expensive equipment that is either self-regulated or auto-regulated is deployed so that extremely high output levels can be accomplished.

This system will come equipped with a method for the automatic supply of flux and wire electrodes, in addition to a plan for the recovery of flux. The flux hopper is attached to the front of the welding head and has magnetically controlled valves that can be opened or closed by the control system.

The wire electrode is continuously supplied at the predetermined constant speed during the process. Either the workpiece is moved or rotated underneath a stationary welding head, or a separate driving system drives the welding head over the workpiece while it is still fixed.

3. Machine mode

Equipment such as a hopper feeding for flux, an automatic arc creation unit, a wire feeding unit, and a flux recovery unit is used in this process. 

Despite this, it is the responsibility of the welder to oversee the process by correctly positioning the work, starting and halting the welding process, and adjusting the controls and speeds so that they are appropriate for each welding.

The wire electrode is continuously supplied at a pace decided upon in advance and remains consistent throughout the process. Either the workpiece is moved or rotated underneath a welding head that is fixed in place, or a separate driving system drives the welding head over the workpiece while it is still fixed.

The Sub Arc Welding’s Primary Applications

A picture of welding using sub arc technique

The process known as the submerged arc is frequently utilized in fabricating heavy steel plates. This includes welding the following items:

  • Structural shapes are the seam that runs longitudinally on pipes with larger diameters.
  • The production of different kinds of machine components for use in all types of heavy industry, the production of vessels and tanks for use in applications involving pressure and storage
  • It is utilized in the shipbuilding industry for splicing and fabricating sub-assemblies, in addition to being used in a wide variety of other industries that use steel in thicknesses ranging from medium to heavy.
  • It is also used for surfacing, buildup, maintenance, and repair.

The Pros and Cons of Employing a Submerged Arc Welding Process

Pros

  • Welding of metal of the highest quality.
  • A mind-bogglingly quick rate of both speed and deposition
  • Welding that is smooth, homogeneous, and finished without any splatter.
  • Little or no smoke.
  • The protective equipment requirement was drastically reduced when there was no arc flash to worry about.
  • It appears that a sizeable quantity of electrode wire is being utilized.
  • Automated processes can easily replace a large number of operators.
  • Manipulative abilities are not required in an everyday setting because they are not needed.

Cons

  • The SAW process can only be used on ferrous (including carbon steel, stainless steel, and mild steel) and nickel-based alloys.
  • Only the 1F and 2F weld positions (fillet welds in flat and horizontal position) and the 1G weld position (butt welding in flat position) are compatible with the SAW process.
  • The SAW process is typically limited to lengthy straight welding and the circumferential welding of pipes with large diameters.
  • The flux supply unit and the flux recovery unit both contribute to the complexity of the system.
  • In multi-pass welding, the slag has to be cleaned up after each pass, and it also has to be cleaned up once the welding process is complete.
  • Semiautomatic or manual operation presents challenges because the welder cannot see the arc created.
  • It is necessary to use a backing plate or strip to get the best possible weld penetration and to stop metal from flowing out of the weld.

Facts About Sub Arc Welding

Fact #1

The use of sub arc welding is often limited to horizontal fillet weld sites, flat or circumferential butt joints, and flat joints. Welding in the horizontal groove is possible if the required precautions are taken to maintain the flux in its current location. Using specifically tailored arrangements, other postures can be put to the test. On the other hand, SAWs are not permitted to be utilized in horizontal or vertical positions.

Fact #2

The weld metal’s strength and flexibility can be greater than that of the workpiece metal if the appropriate combination of wire electrode metal and flux is used. The weld metal quality is good when this combination is used.

Fact #3

As a result of the elimination of the human element caused by the automatic and machine SAW, the weld produced is more consistent and uniform. When put up against other methods, the SAW can produce a bigger weld bead with each pass. The SAW has a higher heat input and a slower cooling rate than other models, allowing the vapors more time to escape.

Fact #4

SAW is superior to other arc welding processes in terms of the amount of weld metal deposited during the process. Compared to the SMAW/MMA method, the SAW process can deposit weld metal at a rate of up to 45 kilograms per hour, while the SMAW/MMA method can only deposit up to 5 kilos per hour.

Fact #5

The pace of weld metal deposition can be affected by various factors, including polarity, the length of electrode stick out, the flux composition, and the number of electrodes used. The increased deposition rate for DCEN can be attributed to the fact that negative polarity results in generating the most heat at the electrode (direct current electrode negative).

Examples of Where Sub Arc Welding Can Be Used

  • The sub arc welding method is perfect and highly appropriate for the lengthy straight welding of large-diameter pipes and the circumferential welding of these pipes.
  • Sub arc welding (SAW) is often used to join high-pressure gas cylinders, such as those used for cooking gas in homes.
  • The process of putting a stainless steel surface or cladding over a soft or medium carbon steel base metal to get the high strength of carbon steel and the resistance to corrosion of stainless steel. The way that surfacing is done can also be used for other kinds of maintenance.
  • The sub arc welding method is perfect for making large metal structures and fabrications where the weld length is long, and the welding position is 1F, 2F, or 1G (fillet welds in a flat or horizontal position) (butt welding in a flat position).
  • When welding ferrous materials, such as mild steel, carbon steel, and stainless steel, as well as some nickel-based alloys, the sub arc welding process is typically the one that is used. This approach has become standard practice.
  • The manufacturing of massive military vessels, boilers, chemical reactors, and tanks used in military operations.
  • Since the sub arc welding process can involve numerous passes of welding, the thickness of the metal being welded is not a limiting issue in this method.
  • Welding work on large-scale fabrication projects, including beams and columns.

Conclusion

Sub arc welding is a process that uses an electrode to create the weld. The electrode is placed in a holder, and the welder inserts it into the weld joint. 

When you are sub arc welding, you want to ensure that you have good contact with the workpiece to get a good weld. If you are looking for quality welds, then sub-arc welding is your process.

Below is the helpful YouTube video about Sub Arc Welding

Frequently Asked Questions

What are some applications of the saw welding process?

SAW technology is a great choice for building big pipelines, vessels, pressure tanks, and many other structural applications. SAW is suitable for welding of carbon steels, low alloy steels, stainless steels, and nickel-based alloys.

Why is it called “submerged” arc welding when it’s done above water?

The process of submerged arc welding is named this because the arc and weld zone are submerged in a layer of flux.

What kind of electrode is used during the SAW welding process?

Direct-current positive (DCEP) and direct-current negative (DCEN) electrodes are used during the SAW welding process. The most commonly used size when SAW welding with direct power is an electrode of 3.2 millimeters.

Where does saw welding fall short, and what are its limitations?

One of the few significant constraints is that it can only be carried out in a flat welding posture. Because the molten metal can only be used in the 1F, 1G, and 2F positions. Additionally, it is unsuitable for thin metals.

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