Butt welding is a welding technique used to connect parts which are nearly parallel and don't overlap. It can be used to run a processing machine continuously, as opposed to having to restart such machine with a new supply of metals. Butt-welding is an economical and reliable way of jointing without using additional components.
Usually, a butt-welding joint is made by gradually heating up the two weld ends with a weld plate and then joining them under a specific pressure. This process is very suitable for prefabrication and producing special fittings. Afterward, the material is usually ground down to a smooth finish and either sent on its way to the processing machine, or sold as a completed product.
This type of weld is usually accomplished with an arc or MIG welder. It can also be accomplished by brazing. With arc welding, after the butt weld is complete, the weld itself needs to be struck with a hammer forge to remove slag (a type of waste material) before any subsequent welds can be applied. This is not necessary for MIG welds however, as a protective gas removes any need for slag to appear. Another advantage with a MIG welder is that a continuous copper wire is fed onto the stock, making the weld virtually inexhaustible.
Butt welding can also be achieved through traditional blow torches in the most common form of butt joints, a process that uses some variety of flux, usually a tin-based solder and precise hand-eye coordination that is common for hand-made boxes of copper, brass, and silver. There are two types of butt welding; one is carried out by smiting and another is carried out by welding two work pieces by non-overlapping.
The process consists of two desired strips of metal that are lined with flux that is lightly dried with a blowtorch until it is a sticky consistency, followed by cutting a strip of solder that is generally 20% of the full joint's size. Applying heat gently makes the gel-like flux now appear white and powdery which now is primed to be welded in which the blow torch is arched so that the "heat cone", the bluest and hottest part of the flame, is now directly upon the sauter melting the joints together evenly.
The joint is then cooled and cleaned in a solution of sulfuric acid diluted in 20 parts water – commonly known as "pickle" – to remove imperfections. Sanding and polishing then achieves the desired finishing.
EN 1993-1-8, which covers the design of joints in the design of steel structures, defines a set of provisions for welding structural steel.
- Britannica Concise Encyclopedia (2003) p. 1997