ANS:C - mild steel

Oxyacetylene welding, also known as oxy-fuel welding or gas welding, is a welding process that uses a combination of oxygen and acetylene gases to generate a flame capable of melting metal. This process is commonly used for welding mild steel due to its versatility, portability, and ability to produce high-quality welds. When welding mild steel, the oxyacetylene flame typically used is the reducing flame. This flame type has a chemical composition that is slightly fuel-rich, meaning there is an excess of acetylene gas compared to oxygen. The reducing flame is characterized by its light blue inner cone and darker blue outer envelope. Several reasons make the reducing flame ideal for welding mild steel:

1. Protection from Oxidation: The reducing flame provides a protective atmosphere around the weld pool, preventing the molten metal from reacting with atmospheric oxygen and forming oxides. This protection helps minimize the formation of slag and porosity in the weld, resulting in cleaner and stronger welds.
2. Precise Heat Control: Oxyacetylene welding allows for precise control over the flame temperature by adjusting the ratios of oxygen and acetylene. The reducing flame provides a relatively low-temperature flame compared to other flame types, making it suitable for welding thin sections of mild steel without causing excessive distortion or burn-through.
3. Clean Weld Bead: The reducing flame produces a clean and well-defined weld bead with minimal spatter. This helps maintain good weld aesthetics and facilitates post-welding operations such as grinding and painting.
4. Versatility: While particularly well-suited for mild steel, the reducing flame can also be used for welding other materials such as cast iron and low-alloy steels. Its versatility makes it a preferred choice for many welding applications.

In summary, oxyacetylene welding with a reducing flame is widely used for welding mild steel due to its ability to provide excellent weld quality, precise heat control, and protection from oxidation. This process remains popular in various industries, including automotive, construction, and fabrication, where the versatility and portability of oxyacetylene equipment are advantageous.