An oxy-acetylene flame is generated by mixing acetylene gas with pure oxygen. This combination creates a flame capable of reaching high temperatures, making it a valuable tool in industrial and artistic applications. This article explores the heat produced by an oxy-acetylene flame and its practical implications.
The Extreme Temperature of Oxy-Acetylene
An oxy-acetylene flame can generate temperatures ranging from approximately 5,600°F to 6,300°F. This temperature range is considerably higher than many other common flames. For instance, a typical candle flame reaches temperatures between 1,800°F and 2,550°F in its hottest regions. Similarly, a natural gas stove flame usually burns at around 3,500°F to 3,560°F. The most intense heat within an oxy-acetylene flame is concentrated in its inner cone, which is the primary reaction zone.
The Science Behind the Heat
The extreme temperatures of an oxy-acetylene flame result from an energetic chemical reaction between acetylene (C₂H₂) and pure oxygen (O₂). When acetylene combusts in the presence of pure oxygen, unlike atmospheric air, the reaction rate increases significantly. Air contains only about 21% oxygen, while pure oxygen provides a concentrated supply, allowing for more complete and rapid combustion. This increased reaction speed releases more heat in a confined space, leading to a much hotter flame.
The combustion process occurs in two distinct stages. The first, known as primary combustion, takes place in the inner cone of the flame. Here, acetylene reacts with a limited amount of oxygen to produce carbon monoxide and hydrogen. This initial reaction releases much heat, forming the hottest part of the flame.
Following the primary stage, secondary combustion occurs in the outer envelope of the flame. The carbon monoxide and hydrogen produced in the inner cone then react with additional oxygen drawn from the surrounding air. This reaction completes combustion, forming carbon dioxide and water vapor. Both stages contribute to the flame’s high temperature and efficiency.
Practical Uses of This Intense Heat
The heat produced by an oxy-acetylene flame makes it useful for industrial applications. One common use is in welding, where the flame melts and fuses metal pieces together. The high temperature is sufficient to melt steel, allowing for strong joints to be formed. This process often involves adding a filler rod to bridge the gap between the metals being joined.
Oxy-acetylene torches are also used for cutting metal. The flame preheats the metal to its ignition temperature, which for steel is typically between 1,300°F and 1,600°F. Once the metal is sufficiently heated, a high-pressure stream of pure oxygen is directed at the heated area, causing a rapid chemical reaction that cuts through the material. This reaction, an exothermic oxidation, melts the metal and blows away the resulting slag, creating a clean cut.
Brazing is another application that benefits from the high heat of an oxy-acetylene flame. In brazing, a filler material with a lower melting point than the base metals is melted and flows into the joint to create a bond. The flame’s temperature ensures the filler material melts and spreads through capillary action, joining components without melting the base materials themselves.