Can You Weld Rebar? All the Facts!
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Also referred to as reinforcement bar or reinforcement steel, rebar is used to enhance the structural strength of concrete. It is usually added to concrete for use, especially in large structures. Rebar has almost the same thermal expansion coefficient as concrete; thus, the two will contract and expand at the same rates, which begs the question of whether you can weld rebar. Well, some rebars are weldable while others are not.
There are various sizes and grades of rebar. Some of the grades can be welded, while others cannot, so another fastener must be used to tie and connect them. Weldable rebars have a carbon ratio of less than 2.1%. On the other hand, non-weldable rebars feature a high amount of carbon that makes them brittle and unsuitable for welding.
In this article, we will discuss in detail the different types of weldable and non-weldable rebar and the methods used in the welding process. We also look at the mistakes to avoid in the rebar welding process. Keep reading.
Types of Rebar
There are different types of rebar you can use for your construction project. As mentioned above, some can be welded while others should not. Here are the different types.
Weldable rebar: Low alloy mild steel rebar can be welded due to its low steel to carbon ratio. A welded rebar remains intact under immense loads since it is fully encased in concrete. It is the only rebar that you can weld without other special considerations.
Non-weldable rebar: The chemical composition or components of steel makes rebar weldable or not. High carbon content makes the steel more brittle, making it unsuitable for welding. The heat and stress of welding the rebar together can make it shatter.
Below are the types of rebar:
Mild Steel Bars
These rebars are round-shaped, featuring a plain and smooth surface. They are available in sizes ranging from 6 mm to 50 mm. Mild steel bars are available in special projects where they are used like dowels in spirals, columns, or where the mild steel must slide into a metal sleeve. One of the most significant benefits of using these bars is that they are easy to cut and bend. It’s also weldable because of its low carbon content, which is 0.3% or less.
Deformed Steel Bars
Deformed steel bars have a deformed surface featuring lugs or ribs. With their different surface texture, it’s easy to transport them since they don’t slide around like the normal steel bar. The uneven surface creates a stronger bond between the steel and concrete.
Besides, they prevent cracks around steel used to reinforce the concrete. It’s another weldable rebar since it just contains 0.42% carbon content.
Thermo Mechanically Treated Bars
These steel bars are heat-treated to offer more strength to the concrete. They are more flexible, easy to bend and weld. The rebars are weldable because of a low carbon ratio of 0.5%.
High-Strength Deformed Bars
The high-strength deformed bars are similar to deformed steel bars, but they are cold treated to make them more flexible and stronger. Due to their low carbon content of 0.2, they are a perfect choice for welding.
There are other types of rebar that are not commonly used. They include galvanized rebar, stainless-steel rebar, carbon steel rebar, and epoxy-coated rebar. Stainless steel rebar is the most high-quality and costly. With a carbon ratio of 0.8%, stainless steel rebars are weldable. Note that the choice of the rebar to use is determined by where they are being used as specified by a building engineer.
How to Weld Rebar
You must weld rebar according to the set standards to get the best results. Once the welding is done correctly, the rebar offers a rigid and strong structural connection making the rebar cages and mats easy to transport. The welded rebar also makes the concrete strong as it should.
Welding rebar is not as complex as many people think. The most important thing is ensuring that the proper welding practices and standards are followed.
- Select the correct type of rebar for welding
- Decide whether preheating of the rebar is necessary and ensure that it is done when required
- Pick the right welding rod or filler wire to weld
- Perform the correct weld placement, and prepare the rebar perfectly
Methods Used to Weld Rebar
As you weld rebar, there are three major welding processes to apply. You can use:
1. Flux Core Arc Welding
This rebar welding process involves using a continuously fed wire electrode filled with flux to form an electrical arc that offers the heat needed to melt the metal welded.
- Collect all necessary equipment such as gloves, welding mask, safety glasses, clamps, magnets, welders, etc.
- Clean the rebar you want to weld.
- Cut a wedge on two pieces to connect when welding.
- Turn the welder on and set the correct settings.
- After welding, clean the welded part.
- Repeat the same for all other rebars you want to weld.
2. Shielded Metal Arc Welding
This rebar welding method utilizes a consumable flux-coated electrode to form an arc between the electrode and welded rebar. Molten metal moves from the electrode through the electric arc and is deposited into the welded rebar. The flux coating melts and forms a surface on the molten weld as a slag.
- Clean the rebar to be welded.
- Put the electrode into the insulated holder and set the proper amperage levels.
- Decide the appropriate arc length and do the welding.
- Remove any slag with a chipping hammer before you apply the second weld.
3. Gas Metal Arc Welding
This arc welding process involves forming an electric arc between the metal and the wire electrode and applying heat to the rebar you want to join. This melts and fuses the two pieces to form a strong joint.
- Set up the machine, gas tank, welding gun, and feed wire.
- Attach the group clamp.
- Clean the rebar parts you want to join.
- Turn on the gas cylinder.
- Set up welding parameters.
- Turn the welder on.
- Set the speed of the feed wire and check the welding gun wire.
- Start rebar welding.
- Clean the welded part after the process.
How to Select the Suitable Filler
The type of filler you choose depends on the type of welding method and the type of rebar you want to use. If you use rebar of A615 grade 60, you can use shielded metal arc welding or gas metal arc welding. With Shielded Metal Arc Welding, the right filler to use are electrodes E9015-X, E9016-X, E9018-X, or E9018M. For gas metal arc welding, you can use ER90S-XXX or ER90C-XXX electrodes.
Before starting the welding process, you must ensure that the rebar welded is perpendicular and parallel.
- Lap Joints – These joints are the same as butt joints; however, the ends of the two pieces of rebar are overlapped instead of being butted together.
- Butt Joints – Butt joints in steel rebar are the same as other butt-welded joints. The two pieces of rebar are butted together and then welded.
- Splices – Splices are the same as lap joints and are a great way to weld rebar.
To connect the pieces of rebar, you need to use a quick wedge. The wedge helps secure the pieces together in a sleeve with a pin. Since assembling the wedge is simple, many rebar pieces can be joined even during poor weather conditions.
Before you start to weld the rebar, make sure that the rebar is locked into position and will not move during the welding or preheating process. If the rebar moves, you need to cut and straighten it or reinforce it to strengthen the new joint. Also, ensure the rebar is sanded and brushed to get rid of oil or dirt.
When to Preheat Rebar before Welding
Whether to preheat rebar or not before welding depends on the size being welded and also the carbon equivalent. Rebar with a large amount of carbon is not easy to weld and needs more preheating to ensure that the welds don’t adversely affect their structural integrity.
Request for a mill certificate from your supplier to determine the carbon content of the rebar you want to use. With the information, you can easily determine whether your rebar requires preheating or not.
How Welded Rebar Adds Strength to Your Structure
Concrete is the most commonly used construction material for laying the foundations of structures and buildings. You can create piers, walls, and foundations using various types of concrete. However, it’s good to know that it is not only the concrete that holds the structures together and makes them strong.
Concrete is prone to cracking, and if you use it alone, your structure or building is prone to cracking and crumbling. Welded rebar helps increase the tensile strength of the concrete to make it more durable and reliable. The rebar design depends on the structure you are building. Thus, walls, posts, and floors have different designs.
What Happens If the Rebar Cannot Be Welded?
If your rebar cannot be welded, they are connected by tying them together using a 16-gauge wire. A significant advantage of the wire-tied rebar is that the complex cages or other structures can be created on the construction site. Rebar tying makes the building construction quicker than welding the different parts.
Common Rebar Welding Mistakes to Avoid
- Poor preparation: If you don’t prepare adequately for the rebar welding, you produce low-quality welds with paint, dirt, or other contaminants in the weld area. You need to remove any cracks on the weld metal by cleaning and grinding the rebar to be welded.
- Failure to observe the right safety precautions: Safety should be a top priority when welding rebar. This helps avoid welding related injuries that may be irreversible and permanent. Ensure you have safety boots, safety glasses, welding helmet, and hearing protection. Safety glasses keep your eyes safe from the spatter from the welding arc, flying metal pieces, and the dangerous arc rays.
- Using wrong wires and electrodes: Regardless of the rebar welding method, you need to select suitable wires and electrodes because different electrodes are made for different uses. With the wrong electrode, you face several problems in the rebar welding process. So, ensure you only use an electrode specifically designed for the rebar welding.
- Allowing the arc to strike out of work: This mistake occurs due to lack of focus on where the arc should be. Allowing the arc to strike out of work can ruin any metal it touches. You can easily damage your work and the rebar you are working on. To avoid this, you must stay focused on the work at hand and be calm.
- Applying the wrong preheat temperature control: Another great mistake you need to avoid is insufficient preheating or failing to do so when the process is required. Preheating is a critical process to prevent cracks from developing in the weld. Another important thing is to ensure that you select the right preheat temperature control for your work. Besides, make sure that you preheat the material by letting the heat go up to three inches on both sides of the weld joint. This makes the joint stronger and be able to sustain itself for a long time.
Some rebars, such as Thermo. mechanically treated bars, deformed steel bars, mild steel bars, high-strength deformed bars, and stainless-steel bars are weldable since they have a carbon ratio of less than 2.1%. High strength and alloy steels are non-weldable because they are brittle and likely to break under load.
For the rebars you cannot weld, you can tie and connect the pieces with 16-gauge wire. Before starting the rebar welding, ensure you are well prepared and equipped with all the necessary equipment. Regardless of the welding method used, ensure that your welds meet the set codes and standards to enhance the structural strength of your building.
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