Structural welding involves creating a variety of welds with different component materials to create, fabricate, and erect welded structures. Structural welding has its own set of codes, blueprints, and types of weld joints.
Structural welders require a specific set of skills involving balanced measurements and precision to do an effective job. In this article, I’ll cover several issues concerning structural welding, its requirements, and its results.
Where is structural welding used?
Structural welding is used to create metal frameworks for buildings, bridges, vehicles, and a variety of other complex structures. Structural welding is also used to cut and repair beams, columns, and girders.
Structural welding is used in various industries, including construction, manufacturing, shipbuilding, mining, oil and gas distribution, vehicle manufacturing, aerospace, military, and heavy industries.
Types of welding processes used in structural welding
Commercial-grade steel is the most widely used metal in structural welding. It offers much better durability and is more sustainable under stress than most other metals.
Another benefit is that it is quite lightweight compared to other metals like aluminum and iron. Steel is also quite economical.
There are mainly three types of welding processes involved in steel structural welding; stick welding, stud welding, and flux core arc welding.
Stick welding
Stick welding is also commonly known as shielded metal arc welding (SMAW). It is the most widely used steel structural welding process.
In this method, the arc is struck between a flux coated consumable electrode and the metal that needs to be welded.
The flux is created from a mineral-based component that covers the molten weld puddle and protects it from the environment. Once the weld cools off and solidifies, the slag deposit is removed with a chipping tool or a wiring brush.
SMAW welding is used to weld or join together two metals pieces, such as steel, with steel to create more complex structures. The electric current used in stick welding can be either AC or DC.
Stick welding is considered the most simple and inexpensive type of welding process for creating steel structures. Much of the fabricating and metal welding industry prefers using this welding process due to its simplicity.
Stick welding offers several benefits for creating structures:
- This welding process is can be used indoors and outdoors
- Stick welding is inexpensive compared to other types of structural welding processes
- It offers a large variety of welds
- SMAW can be used for many types of metals besides steel
- You can use different electrodes with stick welding
Stud welding
Stud welding is also used for the fabrication of steel structures. This process is also called drawn arc stud welding (DASW).
In this method, a fastener or stud is secured on a base metal during the welding process. The fastener comes in different types of shapes such as tapped, threaded, or unthreaded.
A special type of flux is used in the stud welding method. Both the fastener and the substrate that is joined together can be of different materials including steel, stainless steel or aluminum, etc.
Stud welding is also very popular for creating more-complex metal structures. Structural welders opt for stud welding due to the following:
- This type of welding is only carried out on a single-sided, which means you don’t need access to the other side. Sometimes this is the only option you have.
- Stud welding is quite secure. Unlike peripheral welds that are used to weld bolts into place, a DASW joint is a complete cross-sectional weld.
- In terms of cosmetic appearance, a structural weld is superior to a stick weld. Since you only need to use a fastener on one side, there may be no indicators that you have attached a fastener from the other side.
- Stud welding is easy to learn and does not require any special skills to accomplish.
- Stud welding is quicker than other types of structure fabrication methods. Welding a 3/4” fastener only takes about one second.
The stud welding method is applied in the following industries:
- Buildings, construction sites, and bridges
- Cable management firms
- Foodservice businesses including coffee houses, salad bars, bakeries, griddles at restaurants, etc.
- Power supply equipment
- Military, shipbuilding, and aeronautical applications
- Manufacture of moving vehicles in construction, automotive, agriculture, etc
Flux core welding
Flux-core arc welding (FCAW) is a semi-automatic or electric welding process that is used for creating complex structures. The process is quite similar to MIG welding in practice because both of them use the same type of filler wire as an electrode for the arc.
The process uses the flux itself to shield and coat the weld pool instead of shielding gas. The coating also gives the weld puddle more time to cool, creating a more stable weld.
FCAW requires a machine to continuously feed the electrode into the weld puddle, which makes it relatively easy to use. This type of welding is more useful for dense welding sections of a structure that is at least one inch thick because it has a higher weld metal deposit rate.
Flux core welding offers a few unique benefits that make it preferable over other types of welding:
- Flux core welding does not require an additional shielding gas
- It is ideal for welding in outdoor environments even in windy conditions
- Other types of structural welding have a higher chance of porosity than flux core welding
- When you have the right filler material available, FCAW is all about positioning; it is quite easy to learn and apply
- Flux core welding is vastly used in industries that require high speed, consistent welding
Since flux core welding offers high penetration and ideal for outdoor application, you will find it more commonly used in heavy industries including building and public works construction.
Field vs shop based structural welding
Structural welding can take place on the field or inside a workshop. On-site welding in the field will require you to account for a host of elements such as wind, height, and angle of work.
Welding in the shop has its challenges because you will need to prepare the structure in a way that it can be carried to the site.
Structural welding in the field
Most of the experienced welders prefer to use stick welding for outdoor jobs because they are comfortable with it. However, switching to FCAW can really improve productivity.
FCAW welding does not require any shielding gas and creates deep welds that may be ideal on a construction site.
While stick welding is a familiar process for many and welders prefer it because it is more portable, it is also very slow. You will need to change the filler sticks often.
That is why, when a structural welding job in the field requires a large amount of welding in a single location, it could be much more productive to switch to FCAW wire welding.
In some cases of field structural welding applications, it may be more effective to use a mix of stick and FCAW welding on the same job. Areas that require more welding at a single location should be tasked with a flux core machine while small welds spread over a large area should be completed with stick welding.
Structural welding in the shop
For structural metal welding applications in the shop, both FCAW and stud welding are useful due to their ease of application and all-position capabilities. You don’t need a lot of skill in operating the equipment.
What you do need are proper structure blueprints, understanding of welding codes, and a good head on your shoulders to apply the arc.
These features make both methods useful for structural welders of different skill levels. The wires used in flux welding, in particular, allow a very large parameter in which they can operate quite well.
They give you a large margin of error, and even inconsistent techniques can get the job done quickly.
If you are looking to create a smoother finish, then stud welding may be ideal for projects you need to complete in-shop. You can also use these welding techniques on dirtier base metals without the need for clearing them up.
Stud and FCAW welding does produce a lot of slag and splatter which must be removed in between passes and after finishing up the welded structure. The slag can also accumulate on the shop floor, which requires additional cleaning.
This may be new for welders who are only used to stick welding in the shop.
Summary
In this post, I took a brief look at structural welding and different types of processes used for fabricating and joining structures. We also examined the differences between welding structures in the shop and out on the structure construction site.