Welding Toolbar Download Page Welding Directory Image
Home Link to us DirectoryNEW Site map Search Language

Index >> Gas Welding Processes and Equipments >> Oxy Hydrogen and Other Fuel Gas Welding

Oxy Hydrogen and Other Fuel Gas Welding

Oxy Hydrogen and other Fuel Gas Welding -Though oxyacetylene flame is the most versatile and hottest of allthe flames produced by the combination of oxygen and other fuel gases, depending upon various factors as listed below, other gases such as Hydrogen, Propane, Butane, Natural gas, etc., may also be used for some welding and brazing applications.
The factors are:
1. The type of material to be welded.
2. The required welding temperature.
3. Which fuel gas is readily available.
4. The relative cost of supply of the fuel gas.

Given below are the approximate flame temperatures of oxygen and various fuel gas combinations.
Oxyacetylene 3200°C
Oxyhydrogen 2500°C
Oxypropane 2500°C

Hydrogen
Oxyhydrogen flame is used to weld and braze metals only with low melting points, e.g., aluminium, magnesium, lead etc.The temperature of the hottest part of an oxy-hydrogen flame suitable for welding is only about 25000C against 3200°C of an oxyacetylene flame.

In oxyhydrogen welding, if a higher temperature is obtained by increasing the oxygen supply, the flame becomes quite unsuitable for welding. Oxyhydrogen welding is therefore not used for welding steel.
Hydrogen is available in compressed gas cylinders.
Complete combustion of hydrogen requires an oxygen to hydrogen ratio of 1 to 2,
2H2 + O2 --> 2H20
This gas mixture produces a strongly oxidizing flame. The oxyhydrogen flame is scarcely visible and there are no combustion zones as in oxyacetylene flame. Therefore it is impossible to obtain a neutral oxyhydrogen flame by the visible methods of flame adjustment. To avoid an oxidizing flame, the pressure regulators must be set to provide an assured excess of hydrogen.

Since there is no carbon, the oxyhydrogen flame is only reducing (and never carburizing). The oxyhydrogen welding is similar to oxyacetylene welding with the difference that a special regulator is used for metering the hydrogen gas.
Propane, Butane and Natural Gas
Propane and Butane are derived from petroleum. Natural gas is a low pressure fuel gas. Complete combustion of natural gas (methane) and propane is shown, respectively, by the following equations.
CH4 + 2O2 --> CO2 + 2H2O
C3Hg + 5O2 --> 3C02 + 4H2O
These fuel gases alongwith oxygen can be used to weld lower melting point metals, but their use in metal joining is usually limited to brazing. Natural gas can be used in soldering, brazing, preheating and cutting. Propane and Butane are used primarily in brazing. These gases are not used for welding steel.

Because, when the flame temperature is made high enough to weld steel, the flame atmosphere is excessively oxidizing, but when the ratio of oxygen to fuel gas is decreased to produce a carburising condition, flame temperature goes too low. Sometimes, LPG or liquified petroleum gas is also employed as a fuel gas for brazing, soldering and cutting metals.

  
Home | Site map | Submit Article | Directory | Search
  Language >> English | Français | Español | Deutsch | Italiano | Portugues | Japanese | Korean | Sim-Chinese