Which flame is used for heating and brazing metals in welding?

Which flame is used for heating and brazing metals in welding?

• A. The electric arc flame
• B. The laser flame
• C. The plasma flame
• D. The oxy-fuel flame

Answer: (D)

Heating metals to brazing temperatures without melting the base metal is the idea here. The oxy-fuel flame is used for this because it can reach very high temperatures and can be tuned to heat the joint smoothly. With an oxy-fuel setup you mix fuel gas with oxygen to create a flame that can be made neutral, which helps minimize oxidation of the metal surfaces as they heat. Once the joint is hot enough, you apply the filler metal and it flows into the joint by capillary action to form the bond, with flux helping to keep surfaces clean. Other options are different energy sources that melt metal rather than just heating for brazing. Electric arc welding, laser, and plasma approaches are mainly about melting and fusing metal, not the heating-and-brazing process described here.

Heating metals to brazing temperatures without melting the base metal is the idea here. The oxy-fuel flame is used for this because it can reach very high temperatures and can be tuned to heat the joint smoothly. With an oxy-fuel setup you mix fuel gas with oxygen to create a flame that can be made neutral, which helps minimize oxidation of the metal surfaces as they heat. Once the joint is hot enough, you apply the filler metal and it flows into the joint by capillary action to form the bond, with flux helping to keep surfaces clean.

Other options are different energy sources that melt metal rather than just heating for brazing. Electric arc welding, laser, and plasma approaches are mainly about melting and fusing metal, not the heating-and-brazing process described here.