Which flame has a smooth, bullet-shaped inner cone?

The flame characterized by a smooth, bullet-shaped inner cone is the neutral flame. This type of flame is created when the fuel gas and oxygen are mixed in a balanced ratio, allowing for complete combustion. The result is a steady, well-defined inner cone that is optimal for many welding applications, as it produces a clean, hot flame suitable for welding a variety of metals without altering their chemical composition.

In contrast, a carburizing flame has an inner cone that is larger and more diffuse, indicating a higher concentration of fuel gas compared to oxygen, which can introduce unwanted carbon into the weld. An oxidizing flame, on the other hand, will have a shorter, sharper inner cone due to an excess of oxygen, which can lead to oxidation of the base metal and potentially weaken the weld. The cutting flame, while similar in appearance to a neutral flame, is specifically adjusted for cutting purposes and has a different inner cone shape and heat intensity designed for that application.

Understanding the distinct characteristics of these flames is essential for proper welding technique and achieving desired material properties in the weld.