Carbon steel is a large family of steel alloys that feature a common carbon alloying element along with various other elements depending on the intended end use of the steel. There are several fabrication methods used to join these materials, with welding being one of the more popular examples. Low carbon steel is fairly easy and straightforward to weld using a number of different methods including arc and shielded gas processes. High-carbon steel welding is a little trickier and requires careful pre-heating and post-weld cooling of the metal.
The term carbon steel is a fairly generic description of a large family of steel alloy products. These materials may feature a number of different alloying elements depending on their intended use, but all contain carbon to varying degrees. One of the more common methods of construction and fabrication of structures and parts using these materials is carbon steel welding. Welding involves bringing two pieces of metal together to form a close union with little or no gap between them. A permanent joint between the two is then formed by melting the pieces together in a narrow, focused line along the union with localized high temperatures.
The carbon content of any carbon steel product not only dictates its working characteristics, but also affects the welding of the materials. For this reason, carbon steel welding of high and low carbon varieties differ from each other to an extent determined by the total carbon content of the metal. Steel with a low carbon content, or mild steel as it is commonly known, is the easier range to weld and represents the majority of carbon steel welding in manufacturing and construction. Mild steel may be welded using conventional arc welding, oxy-acetylene welding, or one of the gas-shielded arc welding processes.
Arc, or stick, welding is one of the two most common methods of welding low-carbon steels. Arc welding machines produce a high electric current that passes through a pair of cables attached to live and earth terminals on the machine. The live cable has a spring-loaded clamp on its end into which a flux-covered electrode is clamped. The earth cable is fixed to metal work pieces with another clamp. When the electrode is brought close to the metal, the current arcs onto the metal, producing a strongly-focused, localized area of intense heat.
This heat melts the metal work pieces at the weld point along with the electrode and the flux, the melted flux pool preventing oxidization contamination of the weld. The other common low-carbon steel welding method is gas metal arc welding, or MIG. This process works in a similar fashion to arc welding, only the electrode is a continuous wire strand fed through to the welding point by the welding machine. A constant stream of argon gas or an argon/helium mixture is directed onto the weld point, which shields the weld pool from contamination. Gas tungsten arc welding, or TIG, and oxy-acetylene welding are less commonly used low-carbon steel welding methods.
High-carbon content steel is useful due to its hardness, a characteristic that makes it more difficult to weld than mild steel due to the fact that heating the metal tends to soften it. Although the same carbon steel welding methods are used to weld high-carbon steel, the preparation and post-welding treatments differ. To prevent the steel softening during welding, the parts are typically pre-heated and cooled in a controlled fashion after welding. The extent of this pre-heating and cooling process is dictated by the overall carbon content of the steel.