Butt-welding is the process of joining two pieces of material together along a single edge in a single plane. This process can be used on many types of materials, though metal and thermoplastics are the most common. When two sheets of steel are laid side-by-side and joined together along a single joint, this is an example of butt-welding.
Welding can be done using a large machine or a simple portable welder. The machine applies heat to the two materials that are being joined, which causes them to melt slightly to form a liquid. A filler material made from tungsten or a metal alloy is often added in between the two objects and melted into the pool of liquid. When the heat from the welding machine is turned off, the liquefied metal and filler will quickly solidify to form a single unit. When this process is done correctly, the edges of each object are not distinguishable beneath the filler material.
There are three basic types of butt-welding, and each is chosen based on the thickness of the objects being joined. For thin sheets of metal or plastic, a square weld joint can be used. In this instance, the edges of the objects form 90-degree angles to one another, and can be butted together like two building blocks. This is the simplest and most economical type of butt-welding joint.
When thicker materials are welded, the edges must be beveled to form a single or double V-groove. A single V-groove is used on items of moderate thickness, including many pipes. Filler is placed into the wider part of the V-shape to help firmly secure the objects to one another. On a double V-groove, both the top and bottom of each object is beveled. Filler must be placed on both sides and heated in alternating patterns to form the most secure bond possible. This double V-shape is generally used on very thick or large objects.
Butt-welding is used to produce machines, tools, and equipment in a wide variety of industries. It may be performed in manufacturing plants, on construction sites, or in specialty welding shops. Most cities require welders to be trained and certified to operate welding machines, and may also require the use of personal protective equipment and fire-prevention measures.
One of the primary benefits to butt-welding is that it is the only type of welded joint that can be continuously performed by a machine. Series of objects can be passed under a welder automatically in an assembly-line fashion, making this the most efficient and affordable welding technique in use today. While butt welds are considered very strong and secure, they are generally not recommended for use on objects that will be subject to heavy loads or extreme levels of force.