Editing Welding (section)

===Arc welding===
{{Main|Arc welding|Shielded metal arc welding| Gas tungsten arc welding| Gas metal arc welding| Flux-cored arc welding| Submerged arc welding| Electroslag welding}}
[[File:Weld puddle, also known as a weld pool or welding pool.png|thumb|upright=1.3|Welding seen from a welder's perspective through a shaded lens (left) and from the side without a shaded lens (right)<ref>From video by Jose Bueno: {{cite web |last=Bueno |first=Jose |date=2023 |url=https://www.youtube.com/watch?v=KHb5lU1k_OI&t=857s  |title=SMAW - Single Bevel 2G Welding Project |work=Bueno's Handyworks |time=15:10 |archive-url=https://web.archive.org/web/20230512052647/https://www.youtube.com/watch?v=KHb5lU1k_OI |archive-date=12 May 2023}}</ref>]]

All arc welding processes use a [[welding power supply]] to create and maintain an electric arc between an electrode and the base material to melt metals at the welding point. They can use [[alternating current]] (AC) or [[direct current]] (DC). For DC welding, the electrode can be connected to the machine's positive terminal (DCEP) or negative terminal (DCEN), changing the current's direction. The process and type of electrode used will typically determine the current.<ref>{{cite web |title=How Polarity Affects Electrode Performance in Arc Welding |url=https://www.kobelco-welding.jp/education-center/abc/ABC_2002-02.html |website=Kobelco |access-date=3 February 2025}}</ref><ref>{{cite book |last1=Hughes |first1=S. E. |title=A Quick Guide to Welding and Weld Inspection |date=20 October 2009 |publisher=Elsevier |isbn=978-1-84569-767-9 |url=https://www.google.com/books/edition/A_Quick_Guide_to_Welding_and_Weld_Inspec/OamjAgAAQBAJ |language=en}}</ref> 

[[Shielding gas]] prevents oxygen in the atmosphere from entering the molten weld pool. In some processes, the shielding gas is delivered from [[gas cylinder]]s containing inert or semi-[[inert gas]]. In others, a flux coating on a consumable electrode disintegrates to create the gas.<ref>{{Cite journal |last=Thomas |first=Daniel J. |date=2018-04-01 |title=Analyzing the Failure of Welded Steel Components in Construction Systems |journal=Journal of Failure Analysis and Prevention |language=en |volume=18 |issue=2 |pages=304–314 |doi=10.1007/s11668-018-0392-x |s2cid=139797543 |issn=1864-1245|doi-access=free }}</ref><ref>{{cite web |last1=Molyneaux |first1=Justin |title=Flux-Cored Arc Welding Shielding Gas Basics |url=https://www.canadianmetalworking.com/canadianfabricatingandwelding/blog/welding/flux-cored-arc-welding-shielding-gas-basics |website=Canadian Metalworking |publisher=FMA Communications Canada |date=March 1, 2024}}</ref> Filler material is typically added to the molten weld pool and is necessary for processes that use a consumable electrode.<ref>{{cite web |title=Difference between Filler Metal and Electrode |url=https://aqcinspection.com/difference-between-filler-metal-and-electrode/ |website=AQC Inspection |access-date=3 February 2025 |date=21 November 2022}}</ref>

====Arc welding processes====
[[Image:SMAW area diagram.svg|thumb|right|Diagram of arc and weld area, in shielded metal arc welding:
{{image key
|list type=ordered
|Flux coating
|Core wire
|Shield gas
|Fusion
|Base metal
|Weld metal
|Solidified slag
}}]]

One of the most common types of arc welding is [[shielded metal arc welding]] (SMAW);<ref name="Weman63">{{harvnb|Weman|2003|p=63}}</ref> it is also known as manual metal arc welding (MMAW) or stick welding. Electric current is used to strike an arc between the base material and consumable electrode rod, which is made of filler material (typical steel) and is covered with a flux that protects the weld area from [[redox|oxidation]] and contamination by producing [[carbon dioxide]] (CO<sub>2</sub>) gas during the welding process. The electrode core itself acts as filler material, making a separate filler unnecessary.<ref name="Weman63" />

The process is versatile and can be performed with relatively inexpensive equipment, making it well suited to shop jobs and field work.<ref name="Weman63" /><ref name="Cary103">{{harvnb|Cary|Helzer|2005|p=103}}</ref> An operator can become reasonably proficient with a modest amount of training and can achieve mastery with experience. Weld times are rather slow, since the consumable electrodes must be frequently replaced and because slag, the residue from the flux, must be chipped away after welding.<ref name="Weman63" /> Furthermore, the process is generally limited to welding ferrous materials, though special electrodes have made possible the welding of [[cast iron]], stainless steel, aluminum, and other metals.<ref name="Cary103" />

[[File:GMAW weld area.svg|thumb|alt=diagram|Gas metal arc welding:{{image key|list type=ordered
|Travel
|Contact tube
|Electrode
|Shielding gas
|Fusion
|Weld metal
|Base metal}}
]]

[[Gas metal arc welding]] (GMAW), also known as metal inert gas or MIG welding, is a semi-automatic or automatic process that uses a continuous wire feed as an electrode and an inert or semi-inert gas mixture to protect the weld from contamination. Since the electrode is continuous, welding speeds are greater for GMAW than for SMAW.<ref name="LE5.43">{{harvnb|Lincoln Electric|1994|p=5.4-3}}</ref>

[[File:FCAW diagram.svg|thumb|alt=diagram|Flux-cored arc welding: {{image key|list type=ordered
|Flux core
|Tubular electrode
|Shield Gas
|Fusion
|Base metal
|Weld metal
|Solidified slag}}]]

A related process, [[flux-cored arc welding]] (FCAW), uses similar equipment but uses wire consisting of a tubular steel electrode surrounding a powder fill material. This cored wire is more expensive than the standard solid wire and can generate fumes and/or slag, but it permits even higher welding speed and greater metal penetration.<ref>{{harvnb|Weman|2003|p=53}}</ref> As the electrode is consumed, the flux disintegrates to create shielding gas and a protective layer of slag similar to stick welding. Some flux-cored machines have a nozzle that uses a shielding gas to supplement the protection from the flux. This is called dual shield welding, and uses a specialized gas shielded flux-core wire.<ref>{{Cite web |title=Solid Wire Versus Flux Cored Wire: When to Use Them and Why |url=http://www.millerwelds.com/education/articles/article62.html |archive-url=https://web.archive.org/web/20061015112618/http://www.millerwelds.com/education/articles/article62.html |archive-date=15 October 2006 |website=Miller}}</ref>

[[File:GTAW.svg|Gas tungsten arc welding|thumb|alt=diagram]]
[[Gas tungsten arc welding]] (GTAW), or tungsten inert gas (TIG) welding, is a manual welding process that uses a non-consumable [[tungsten]] electrode, an inert or semi-inert gas mixture, and a separate filler material.<ref name="Weman31">{{harvnb|Weman|2003|p=31}}</ref> Especially useful for welding thin materials, this method is characterized by a stable arc and high-quality welds, but it requires significant operator skill and can only be accomplished at relatively low speeds.<ref name="Weman31" />

GTAW can be used on nearly all weldable metals, though it is most often applied to [[stainless steel]] and light metals. It is often used when quality welds are extremely important, such as in [[bicycle]], aircraft and naval applications.<ref name="Weman31" /> A related process, plasma arc welding, also uses a tungsten electrode but uses plasma gas to make the arc. The arc is more concentrated than the GTAW arc, making transverse control more critical and thus generally restricting the technique to a mechanized process. Because of its stable current, the method can be used on a wider range of material thicknesses than can the GTAW process and it is much faster. It can be applied to all of the same materials as GTAW except magnesium, and automated welding of stainless steel is one important application of the process. A variation of the process is [[plasma cutting]], an efficient steel cutting process.<ref>{{harvnb|Weman|2003|pp=37–38}}</ref>

[[Submerged arc welding]] (SAW) is a high-productivity welding method in which the arc is struck beneath a covering layer of flux. This increases arc quality since contaminants in the atmosphere are blocked by the flux. The slag that forms on the weld generally comes off by itself, and combined with the use of a continuous wire feed, the weld deposition rate is high. Working conditions are much improved over other arc welding processes, since the flux hides the arc and almost no smoke is produced. The process is commonly used in industry, especially for large products and in the manufacture of welded pressure vessels.<ref>{{harvnb|Weman|2003|p=68}}</ref> Other arc welding processes include [[atomic hydrogen welding]], [[electroslag welding]] (ESW), [[electrogas welding]], and [[stud arc welding]].<ref>{{harvnb|Weman|2003|pp=93–94}}</ref> ESW is a highly productive, single-pass welding process for thicker materials between 1 inch (25&nbsp;mm) and 12 inches (300&nbsp;mm) in a vertical or close to vertical position.

====Arc welding power supplies====
To supply the electrical power necessary for arc welding processes, a variety of different power supplies can be used. The most common welding power supplies are constant [[electrical current|current]] power supplies and constant [[voltage]] power supplies. In arc welding, the length of the arc is directly related to the voltage, and the amount of heat input is related to the current. Constant current power supplies are most often used for manual welding processes such as gas tungsten arc welding and shielded metal arc welding, because they maintain a relatively constant current even as the voltage varies. This is important because in manual welding, it can be difficult to hold the electrode perfectly steady, and as a result, the arc length and thus voltage tend to fluctuate. Constant voltage power supplies hold the voltage constant and vary the current, and as a result, are most often used for automated welding processes such as gas metal arc welding, flux-cored arc welding, and submerged arc welding. In these processes, arc length is kept constant, since any fluctuation in the distance between the wire and the base material is quickly rectified by a large change in current. For example, if the wire and the base material get too close, the current will rapidly increase, which in turn causes the heat to increase and the tip of the wire to melt, returning it to its original separation distance.<ref>{{harvnb|Cary|Helzer|2005|pp=246–249}}</ref>

The type of current used plays an important role in arc welding. Consumable electrode processes such as shielded metal arc welding and gas metal arc welding generally use direct current, but the electrode can be charged either positively or negatively. In welding, the positively charged [[anode]] will have a greater heat concentration, and as a result, changing the polarity of the electrode affects weld properties. If the electrode is positively charged, the base metal will be hotter, increasing weld penetration and welding speed. Alternatively, a negatively charged electrode results in more shallow welds.<ref>{{harvnb|Kalpakjian|Schmid|2001|p=780}}</ref> Non-consumable electrode processes, such as gas tungsten arc welding, can use either type of direct current, as well as alternating current. However, with direct current, because the electrode only creates the arc and does not provide filler material, a positively charged electrode causes shallow welds, while a negatively charged electrode makes deeper welds.<ref>{{harvnb|Lincoln Electric|1994|p=5.4–5}}</ref> Alternating current rapidly moves between these two, resulting in medium-penetration welds. One disadvantage of AC, the fact that the arc must be re-ignited after every zero crossings, has been addressed with the invention of special power units that produce a [[Square wave (waveform)|square wave]] pattern instead of the normal [[sine wave]], making rapid zero crossings possible and minimizing the effects of the problem.<ref>{{harvnb|Weman|2003|p=16}}</ref>