AWS C4.7/C4.7M:2020

AWS C4.7/C4.7M PDF

This recommended practice describes the equipment, procedures, and safe practices for the oxyacetylene welding of steel. This process is most commonly used for welding carbon steels; however, it is sometimes used on alloy steels, cast iron, aluminum, brass, bronze, copper, nickel, and tin. It is for manual welding using hand torches and is recommended for end users (welders) and management personnel associated with the oxyacetylene welding process.

Oxyacetylene Welding (OAW) is a process where a metal (usually an iron base alloy) is heated to its melting point by an oxyacetylene flame. A welding torch is used for this operation. OAW uses the combustion of acetylene gas in a mixture with oxygen. Acetylene is the fuel gas of choice because it has the ability, along with oxygen, to form a gaseous shield around the molten metal protecting it from ambient contaminants until the molten metal cools. Acetylene is also preferred because most of the heat is concentrated at the tip of the inner cone. This heat focus allows better control to move the weld pool. Virtually all the commercial fuel gases can produce temperatures high enough to melt most metals but acetylene remains the fuel gas of choice because acetylene has the higher combustion temperature. During the welding process, filler material may be added, but it is not always needed. The filler material is used to fill in, build up, and strengthen the weld. OAW is a better choice because the flame condition (reducing, natural, and oxidizing) is easy to adjust compared to other fuel gas mixtures. OAW is not suggested for the fabrication or repair of high-strength steels or heat-treatable metals. OAW is very widely used for maintenance and repair, where flexibility and mobility are important.

Although this recommended practice is not written with mandatory requirements, mandatory language, such as the use of “shall,” will be found in those portions of the document where failure to follow the instructions or procedures could produce inferior, misleading, or unsafe results.

AWS A3.0M/A3.0, Standard Welding Terms and Definitions, are included in Annex B of this recommended practice for information only.