Oxy-fuel welding - Fuels, Flames, Gas Welding & Cutting (2022)

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  • Oxy-fuel Welding Process Fundamentals
    • Critical Differences Between Oxy-Fuel Welding And Arc Welding
    • Equipment Used In Oxy-Fuel Welding
  • Oxy-fuel Gases – Propane, Oxygen, Hydrogen And Acetylene
    • Acetylene Gas
    • Hydrogen Fuel Gas
    • Propylene Fuel Gas
    • Propane And Butane Gas Fuel
  • Types of Flames in Oxy-fuel welding
    • Carburizing Flame
    • Neutral Flame
    • Oxidizing Flame
  • Gas welding Operation Properties
    • Metal Preparation
  • Oxy-fuel Cutting
  • Oxy-acetylene welding Applications
    • Resources:

Oxy-fuel Welding Process Fundamentals

Oxy-fuel welding uses a high-heat, high-temperature flame produced by burning a fuel gas (most commonly acetylene) mixed with pure oxygen. However, keep in mind that three major processes depend on the fuel gas:

  1. oxyacetylene welding
  2. oxyhydrogen welding,
  3. pressure gas welding.

Nonetheless, oxygen can also be mixed with gases such as propylene, butane, and others. The gas used for welding depends on the type of project, cost, and flame control.

This heat is further used to melt interface surfaces of welding plates which are held together to form a joint. You can weld oxy-fuel with or without the help of filler material. If the filler rod is used, it is manually fed directly into the molten weld pool.

Critical Differences Between Oxy-Fuel Welding And Arc Welding

Even though both oxy-fuel welding and arc welding processes such as MIG welding, TIG welding, or Stick use heat to join materials, there is a difference in how heat is formed and the actual temperature.

Arc welding uses electricity as a heat source. As a result, the temperature of the arc reaches roughly 10,000 F.

Meanwhile,Oxy-fuel welding uses a flame as the heat source. The oxygen and acetylene gases reach temperatures up to 6,000 degrees Fahrenheit.

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Equipment Used In Oxy-Fuel Welding

Oxy-acetylene welding equipment is portable and easy to use.The essential kit includes the following:

  • One of the most critical parts of a gas welding system is the fuel gas. The fuel gas is stored insteelpressurized cylindersthat contain oxygen and the fuel gas.
  • Gas flow regulatorstake high pressure from the cylinders and reduce it to working pressure.Typically, this device helps supply oxygen at a steady pressure of between 70 and 130 KN/M2 and the gas supply at between 7 and 103 KN/M2.
  • The oxygen and acetylene gases are transferred from the cylinder to the welding torch through the hose.The flexible hosesshould benonporous to reduce the risks of leaks and to help you install them correctly, the oxygen hose is usually green, and the fuel gas hose is typically red.
  • Manufacturers made another way to help welders install the hoses correctly.The threaded connectorson the hoses are handed to avoid accidental misconnection. That way, the thread on the oxygen hose is right-handed (as standard), while the fuel gas hose has a left-handed thread.
  • Safety valveskeep gas flowing in one direction, preventing gas from flowing back into the wrong line or cylinder. For example, a flashback can damage the equipment or even cause a cylinder explosion, so checking the valve’s state is critical.
  • Welding torcheshave a connection and valve for the fuel gas, a connection and valve for the oxygen, a handle for the welder to grasp, and a mixing chamber with a tip where the flame forms. Keep in mind that there is a difference between a welding torch and a cutting torch.
  • Since there is no industrial standard system for identifyingtip sizes, welders usually compare them to numbered drill sizes.

Oxy-fuel Gases – Propane, Oxygen, Hydrogen And Acetylene

As we mentioned at the start, acetylene gas is the most commonly used fuel in this welding process. However, welders can opt for propylene, liquified petroleum gas (LPG), propane, natural gas, hydrogen, and MAPP gas, depending on the welding operations. In addition, liquid fuel cutting systems use such fuels as Gasoline (Petrol), Diesel, Kerosene, and possibly some aviation fuels.

Propane and Air3590° F
Propane and Oxygen4087° F
Hydrogen and Oxygen5087° F
Acetylene and Oxygen5800°F to 6300 °F

Acetylene Gas

Acetylene is the primary fuel for oxy-fuel welding and is the fuel of choice for repair work and general cutting and welding. Acetylene gas is shipped in special cylinders designed to keep the gas dissolved.

There is about 1700 kPa (250 psi) pressure in the acetylene tank when complete. Acetylene, when combined with oxygen, burns at 3200 °C to 3500°C (5800°F to 6300 °F), which is the highest among commonly used gaseous fuels.

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(Video) Torch Cutting Basics Everyone Should Know | Oxygen & Acetylene Fuel

As a fuel, acetylene’s primary disadvantage, in comparison to other fuels, is its high cost, but the overall prices are still lower when compared to arc welding processes.

Hydrogen Fuel Gas

When combined with oxygen, hydrogen produces a clean flame, which is suitable for gas welding aluminum. In addition, since hydrogen can be used at a higher pressure than acetylene, it is ideal for underwater welding and cutting.

When pre-mixed in a 2:1 ratio with pure oxygen, hydrogen can produce a flame temperature of about 2,000°C (3600 F) at atmospheric pressure. This welding gases mix is often called oxyhydrogen welding.

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Methylacetylene-propadiene (MAPP) gas and LPG gas are similar fuels because LPG gas is liquefied petroleum gas mixed with MPS. It has the storage and shipping characteristics of LPG and a heat value a little lower than acetylene.

MAPP gas can be used at much higher pressures than acetylene, sometimes up to 40 or 50 psi in high-volume oxy-fuel cutting torches which can cut up to 12-inch-thick low carbon steel.

Propylene Fuel Gas

Propylene is used in production, welding, and cutting. It cuts similarly to propane. When propylene is used, the torch rarely needs tip cleaning. There is often a substantial advantage to cutting with an injector torch rather than an equal-pressure torch when using propylene.

(Video) The Full Guide to Oxy Fuel Cutting

Propane And Butane Gas Fuel

Butane and propane do not react with each other and are regularly mixed. As a result, the calorific (heat) values of the two are almost equal. Both are thus mixed to attain the vapor pressure required by the welders and depending on the ambient conditions.

Propane does not burn as hot as acetylene in its inner cone, and so it is rarely used for welding. Propane, however, has a very high number of BTUs per cubic foot in its outer cone, and so with the injector style torch can make a faster and cleaner cut than acetylene.

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Types of Flames in Oxy-fuel welding

Three types of welding flames can be created with oxy-acetylene (OFW). Each one can be differentiated by its color, size, and shape. In addition, each flame can be made with a unique mixture of acetylene and oxygen.

Therefore, the welder can adjust the oxy-acetylene flame to becarburizing(aka reducing), neutral, or oxidizing.

Carburizing Flame

An excess of acetylene in the oxy-fuel gas mixture creates a carburizing flame. You can distinguish this type of flame by observing three flame zones; the hot inner cone, a white-hot “acetylene feather,” and the blue-colored outer cone.

This type of flame is suitable for low-heat flame applications. Therefore, welders use it for welding nickel, Monel metal, high-carbon steel, and a number of non-ferrous metals. However, you cannot use carburizing flame to weld steel.

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Neutral Flame

The neutral flame is the flame most generally used when welding or cutting. As the name states, you can get a neutral flame by equaling the proportions of oxygen and acetylene gases.

You can distinguish this by observing the light blue inner cone and the darker blue to a colorless outer cone. The light inner cone is the place acetylene and oxygen combine. The tip is the hottest part of the flame, as it provides approximately 6,000°F (3,300°C), which is enough to melt steel quickly.

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(Video) Gases used for gas welding and types of oxy-acetylene flames

Remember that this is a chemically neutral flame, meaning it creates fewer sparks and does not boil. In addition, neutral flame protects the steel from oxidation, resulting in solid welds.

Oxidizing Flame

An oxidizing flame has a high content of oxygen (the oxygen and acetylene ratio being 1.5:1). Therefore, increasing the oxygen will result in the hissing noise, while the inner cone gets shorter, brighter, and more pointed.

The oxidizing flame creates undesirable oxides, which affect the structural and mechanical properties of most steel plates. That’s the reason why this type of flame isn’t considered to be practical for welding. However, you can still use it when welding copper and alloys of copper, such as bronze and brass.

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Gas welding Operation Properties

Oxy-fuel welding is used to weld types of metals, including carbon steel, alloy steels, cast iron, aluminum, and magnesium using pure oxygen and fuel/gas. A torch is used to heat two pieces of metals at a temperature that produces a molten pool.

Usually, more metal is added to the puddle by adding a welding rod or filler rod into the molten metal puddle. The metal puddle will travel towards the hottest part of the flame, and that’s why welding torch manipulation is crucial.

The amount of heat depends on the welding tip size, the welding speed, and the welding position.

(Video) Firepower How-to: Setting a Neutral Flame - Welding Attachment
Oxy-fuel welding - Fuels, Flames, Gas Welding & Cutting (8)

The welding tip size determines the flame size. The metal thickness and the joint design determine the proper tip size.

If your project requires the addition of filler metal, you shouldn’t let the welding flame burn it off. Burning filler material with a hot flame will look like a series of cold dots, affecting the strength of the weld. The weld will be stronger than the original base metal when the filler metal is properly added.

Metal Preparation

Base metal preparation is a crucial part of any welding method, and the oxy-acetylene welding process is no exception. Therefore, you should remove contaminants such as oil, dirt, or oxides, as they can cause incomplete fusion, porosity, or slag inclusions.

The thickness of the base metal at the joint determines the type of edge preparation for gas welding. A butt joint is most commonly used to join materials thinner than 3/16 in., while metals thicker than 3/16 to 1/4 in. require a slight root opening or groove. When joining metals thicker than 1/4 in., edges should be beveled.

Oxy-fuel Cutting

Besides welding, the oxy-fuel process can be used for cutting but with a different approach and setup. A cutting torch has a 60- or 90-degree angled head with orifices placed around a central jet.

The torch blows extra oxygen pressure causing the metal to burn and blowing the resulting molten oxide through to the other side. That’s why the oxygen flow rate is critical. The lesser flow will make a slow, ragged cut, while too much oxygen will waste the fuel and produce a wide concave cut.

Oxy-fuel welding - Fuels, Flames, Gas Welding & Cutting (9)

Oxy-propane torches are usually used to cut scraps to save money, while oxy-acetylene can cut only low- to medium-carbon steels and wrought iron.

(Video) Oxy-acetylene welding/ metal cut/ Rayhan Info

Oxy-acetylene welding Applications

Oxy-fuel welding, widely known as oxy-acetylene welding is used for smaller home-based shops and metal-based artworks. In addition, it is helpful once when electricity is inaccessible. Moreover, it’s also used for welding pipes as well as tubes.

Meanwhile, oxy-fuel cutting is still vastly used in heavy industry as well as light industrial and repair work, including the automotive industry.

Overall, the this welding and cutting process is mostly used due to its ability to reduce the thickness of metals. In addition, the equipment is also inexpensive and can be used in both ways, manually as well as mechanized.


Which oxy-fuel flame is usually used for the cutting process? ›

Oxy acetylene cutting has pretty much become synonymous with oxyfuel cutting. The reason is that this is the most common fuel used in the process. The main reason for that is the temperature it can achieve – around 3200° C. Such a high temperature makes faster piercing and cutting possible.

What type of welding is oxy-fuel? ›

Also known as oxy-fuel welding, oxy-acetylene welding is a process that relies on the combustion of oxygen and a fuel gas, typically acetylene. You might hear this type of welding referred to as “gas welding.” Gas welding is used almost exclusively for welding thin metal sections.

What gases are used in oxy-fuel cutting? ›

Oxy-fuel cutting is a thermal cutting process that uses oxygen and fuel gas (such as acetylene, propane, MAPP, propylene and natural gas) to cut through materials.

How does oxy-fuel welding work? ›

In oxy-fuel welding, a welding torch is used to weld metals. Welding metal results when two pieces are heated to a temperature that produces a shared pool of molten metal. The molten pool is generally supplied with additional metal called filler. Filler material selection depends upon the metals to be welded.

What is the temperature of gas welding? ›

Gas welding is carried out by a flame produced by burning approximately equal volumes of oxygen and acetylene which are delivered at equal pressures from gas bottles to a welding torch. The flame temperature is approximately 3100°C, which is high enough to melt steel and other metals.

Which gas is used in gas welding? ›

Acetylene is a major fuel gas used in welding and cutting processes.

What is oxyacetylene used for? ›

Oxy-acetylene gas welding is generally used for welding and cutting operations for metals and alloys. Welding is generally used to join several metals utilizing the heat generated by the combustion of fuel gasses like acetylene, hydrogen, propane, or butane with an oxygen mixture.

How many types of gas cuts are there? ›

There are five main types of gas that are regularly used to perform gas cutting processes – natural gas, MAPP, acetylene, propylene and propane. We can go over each and every one of them in a bit more detail.

What is gas cutting process? ›

In gas cutting a flame of fuel gas such as acetylene burning in oxygen heats the area to be cut; a stream of oxygen is then injected around the flame which actually burns the steel and ejects the oxide as dross.

What is gas cutting safety? ›

Gas Cutting Equipment: Cylinders and Hoses

Only store and use cylinders in the upright position. Secure cylinders at all times to prevent them from falling, whether empty or full. Cylinders should not be rolled on their sides, carried or hoisted unless they are properly slung. Cap all cylinders when not in use.

How do you take Oxy cut? ›

how to cut with a torch. oxygen acetylene welding cutting torch

How do you do oxy welding? ›

Intro to Oxy-Acetylene Welding - Part 2 - YouTube

What are the 4 main parts of an oxy fuel set up? ›

torch body (or handle) two separate gas tubes (through the handle connected to the hoses) separate control valves. mixer chamber.

What type of process is welding? ›

Welding is a fabrication process whereby two or more parts are fused together by means of heat, pressure or both forming a join as the parts cool. Welding is usually used on metals and thermoplastics but can also be used on wood. The completed welded joint may be referred to as a weldment.

How many types of flames are used for welding? ›

There are three types of flames natural flame, carburizing flame and oxidizing flame. Natural flame has synchronized mixture of fuel and oxygen, carburizing flame has more fuel and oxidizing flame has more oxygen. Different material used different flames according to weld condition.

What is the name of gas flame? ›

The LPG (propane) is a blue flame because complete combustion creates enough energy to excite and ionize the gas molecules in the flame. The exception is a gas fireplace having yellow or red flames, for a more realistic look.

Why is gas welding used? ›

Welding gas is used in a range of different ways. These include shielding the arc from impurities like air, dust, and other gases; keeping welds clean on the underside of the seam opposite the arc (or purging); and heating metal. Blanketing gases are also used to protect metal after the welding process.

What is flux in welding? ›

Flux is a mixture of various minerals, chemicals, and alloying materials that primarily protect the molten weld metal from contamination by the oxygen and nitrogen and other contaminants in the atmosphere. The addition of certain chemicals and alloys also help to control arc stability and mechanical properties.

Which air is used in welding? ›

Gases used in welding and cutting processes include: shielding gases such as carbon dioxide, argon, helium, etc. fuel gases such as acetylene, propane, butane, etc. oxygen, used with fuel gases and also in small amounts in some shielding gas mixtures.

Why CO2 is used in welding? ›

Carbon Dioxide (CO2)

Pure CO2 provides very deep weld penetration, which is useful for welding thick material. However, it also produces a less stable arc and more spatter than when it is mixed with other gases. It is also limited to only the short circuit process.

What is the formula of welding gas? ›

∴ g-atoms of C in gas =3.3844=0.077 g-atoms of H in gas =0.690×218=0.077 ∴ Ratio of C and H atoms in gas is 1:1 Thus, empirical formula of welding gas is CH Empirical formula mass of welding gas =13 Molecular mass = (empirical formula mass)×n ∴ n=25.9813≃2 ∴ Molecular formula =2× empirical formula =2×(CH)=C2H2.

How do you cut oxy acetylene? ›

Torch Cutting Basics Everyone Should Know | Oxygen & Acetylene Fuel

How do you use a gas cutter? ›

Welding: Gas Cutting Torch - YouTube

Which tool is used for cutting gases? ›

Gas cutting torches - It is used in oxy-fuel cutting to heat the metal at its ambient temperature. This gas cutting torches use gases like acetylene, propane, propylene and natural gas. The welding torch is a heat source for manual brazing and braze welding and metal forming and welding.

What are the 2 main types of cutting nozzles? ›

» Cutting nozzles for Acetylene are known as ANM nozzles while cutting nozzles for LPG are known as PNM nozzles.

What is the size of cutting nozzle? ›

BOC Cutting Nozzle ANME 1/8", 1/16", 1/32", 3/32", 3/64", 5/64" Acetylene Oxygen Welding.

What temperature does oxygen and acetylene burn at? ›

Air-acetylene produces a flame temperature of around 4000° F (2200° C). This is hot enough to solder aluminum work glass, repair radiators and braze plumbing fixtures. It is not hot enough to weld steel. When acetylene is burned in pure oxygen, the flame temperature may be as high as 5730° F (3166° C).

How do you use oxy torch? ›

How do you turn on an oxy acetylene torch? - YouTube

Is oxy acetylene welding still used? ›

In recent decades, oxy acetylene welding has become obsolete. Our modern arc welders have more consistency and weld faster. However, oxy acetylene cutting is still a commonly used process that is utilized by millions of welders every day.

What are the advantages of oxy acetylene welding? ›

Advantages of Oxy-Acetylene Welding :
  • It's easy to learn.
  • The equipment is cheaper than most other types of welding rigs (MIG/TIG welding)
  • The equipment is more portable than most other types of welding rigs (MIG/TIG welding)
  • Oxy/Acetylene equipment can also be used to "flame-cut" large pieces of material.

What metals can be welded with oxy acetylene? ›

Metal which can be welded with oxy-acetylene flame include iron, steel, cast iron, copper, brass, aluminum, bronze as well as many alloys may be welded. The oxy-acetylene flame is also used for cutting metal, case hardening and annealing.


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