Welding-gas,

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Why Gas Welding?

Welding-gas, welding gas, gas welding, oxyacetylene flame, welding, fusion welding, welding history, acetylene gas, temperature control, welding torch, welding fusion, cutting torches, gas regulators, compressed gases, welding goggles, welder skill, techniques, brazing, hard-surfacing, cutting, welding links, welding tips, instructions, improving welding results, safety issues, joining questions needing answers: these are some of the items developed in this Site for the benefit of interested readers.

In a previous page on WELDING PROCESSES, a short review was offered grouping processes according to some general characteristic. Here we are going to enter into some more detail for the class of FUSION Welding-gas processes known and described as Oxyfuel Gas Welding processes.

What is in here for me?

If you work with oxyacetylene flame you know what you need. But are your helpers as knowledgeable as you are? How would you summarize to them the strong points of the process? Welding-gas Flame or Arc? Which is better for what? Why skill is so important?

Of the fusion welding gas processes developed in the twentieth century, GAS WELDING is probably one of the earliest of modern welding history. Of all the combustible gases tried and used in the past only Acetylene gas practically has been retained for its major advantages which are mainly the high temperature of combustion and ease of production and transportation.


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Tip!: The versatility of the Welding-gas process depends on the level of control that the welder has on the flame, on the heat, on the filler metal and on the welding gas speed. In order to exploit these advantages to their best, the welder must develop substantial skills, through learning and training.

Here are...

The main advantages of Welding-gas, Oxyacetylene welding, are that the process is versatile, adapted to many different jobs, that the equipment is relatively of low cost, portable on a truck or a trailer, even on one's back, self sufficient, independent from availability of external energy sources.

With the limitations of Welding-gas we should include the requirement for welder's skill in manipulating the torch, the flame and the filler rod. Also the use of fluxes which is required for most materials other than low carbon steel. Reactive or refractory metals are unsuited to gas welding.

Do not forget...

Safety issues, like proper handling of compressed gas cylinders, mastering the dangers of explosive gas mixtures, or of burns, or the precautions to take before attempting to repair a drained container of combustible material (fill it with water...), must be addressed seriously and completely: a short account of these issues is presented in the separate page underlined above. In the manual Welding-gas process the heat required for local progressive melting is provided by the oxyacetylene flame. A filler metal rod of appropriate composition may or may not be used as required.

The success of this Welding-gas process, which requires continuous independent supply of the gases acetylene and oxygen from separate high pressure cylinders, derives from the fact that it makes use of a simple but powerful welding torch, where the gases are mixed in about equal volumes and ignited at the exit tip.

The oxyacetylene flame of the Welding-gas process develops an extremely high temperature (max. about 3030oC or 5500oF) at its bright inner cone, useful for melting metals, and permits the welder to protect with the flame itself and with its surrounding envelope the molten puddle from neighboring air which, if allowed in, would oxidize the metal and impair the weld properties.

All the controls...

The flow of the gases can be easily controlled to provide a neutral flame, an oxidizing one or a reducing (carburizing) one depending on the technique of welding employed and on the application requirements.

The welder has also control of the temperature of the metal in the weld zone. By adjusting the flame intensity and the speed of welding, the size and the characteristics of the molten pool are kept consistent with the required shape and appearance of the weld.

The molten metal from the two elements flow together, with or without additional filler metal, and the weld solidifies upon cooling so that the pieces are permanently connected at the joint.

To perform Welding-gas joining, the items of the structure are first assembled, fixtured if necessary and tack welded. Then the welding gas process takes place, possibly in steps, using a proper sequence of separate stretches of welding to minimize deformation.

The flame can be directed to impinge preferentially on the thicker element which should absorb more heat. The thinnest element can be shielded in part from the Welding-gas flame by interposing the filler rod as needed. The filler metal deposition rate is easily controlled by pushing or pulling the filler rod from the tip of the welding gas flame.

The above characteristics make the Welding-gas process best suited to join thin steel sheet metal, tubing and small pipes. Obviously the results depend heavily on the manual dexterity and experience of the welder, namely on his skill.

A good weld has usually a regular appearance, without spatter, visible cracks or other objectionable defects, so that a first quality assessment can be provided by nothing more sophisticate than visual inspection.

Tip!: if an experienced welder cannot satisfactorily weld a simple joint, the reason most probably is in the material, possibly a steel containing high carbon or alloying elements. A complete knowledge of the material type is necessary for dealing adequately with these issues. See the page on MATERIALS IDENTIFICATION.

Check the Hardness!...

Note: for orientation on causes and remedies for poor welds the knowledge of the hardness of the material to be welded may be helpful. Or better, its importance cannot be overstated.

See also our page on Welding Gas Equipment.

In a new page on Oxyacetylene Welding Tips essential information and relevant links to safety provisions for the process are offered.

Summing up

The Welding-gas equipment is generally simple, inexpensive and portable. The techniques of flame control and torch manipulation can be learnt by proper training so that the process is quite diffused and popular, not only for certain production applications but much more for maintenance, for small repairs.

Consider the fact that any maintenance department, big or small, has at least one Welding-gas outfit ready and available for repair work. Suited to short runs, welding gas does not need expensive fixtures. It is best for thin thickness of carbon steel sheet and tube and it is highly controllable.

The equipment as is, is also suited for Brazing, a different process opening up a new full range of applications.
And for Braze Welding, to manufacture or repair many different materials for any sort of uses.

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Any questions or comments or feedback? Write them down and send them to us by e-mail. Click on the Contact Us button in the NavBar at top left of every page.

Hardness Testing made simple We are glad to be able to offer a FREE copy of our book on PRACTICAL HARDNESS TESTING MADE SIMPLE for your direct download on your computer, as already proposed in other sections of this Site. Click on Subscription.

It might help when welding unknown materials.

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The following pages can be reached by clicking on the underlined items:

Gas Welding Equipment
Hobby and Home Welding.
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Hard surfacing
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Issues of SAFETY are addressed separately.

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Welding-gas: versatile, low cost, portable, self sufficient, for short runs, repairs, field work, for thin gages, for artistic, home and hobby work. Adaptable to cutting, brazing, hard-surfacing. See here...

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