Types of Welding Flames » Weld Hacks (2022)

Updated: April 03, 2022

The welding flame is one of the most, if not the most important part of the welding process. The flame is what actually allows the weld to occur, as it heats the metal or filler so that it can be used to combine the materials together.

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Clearly, this is the most integral part of the welding process itself. If the welding flame does not generate enough heat or does not blend the materials together, it can cause the welded area to become compromised, maybe even leading to severe damage. This is why it is essential that the flame be of the right quality and temperature to create a proper weld.

3 Different Types of Welding Flames

While the purpose of the flame is the same no matter what type you are using, the type of flame that is produced can be different. There are three different types of flames, these include:

  • Neutral flame
  • Carburizing flame
  • Oxidizing flame

These flames get their names based upon the chemical effect they have on the material that is being welded. For example, an oxidizing flame produces an oxidation, and this is where its name is derived.

Neutral Flame

A neutral flame gets its name from the fact that it usually has no chemical effect on the materials that are being welded. To create this type of flame, there is a one-to-one ratio of oxygen to acetylene. The additional oxygen that is needed to produce the flame is acquired from the air, which enables complete combustion during the welding process. This is generally considered the prefer method of welding. This type of welding flame is most commonly used with the following materials:

  • Aluminum
  • Copper
  • Cast Iron
  • Stainless steel
  • Mild steel

Just as a reference, if a person is going to use either of the two other types of welding flames, they must first adjusted to neutral before readjusting the mixture for either oxidizing or carburizing.

Within the neutral flame, there are two clearly defined zones. These are easily distinguishable when viewing the welding flame. They include:

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  • The bluish-white area located inside the luminous cone. This is known as the inner zone.
  • The area surrounding the light blue flame envelope or sheath.

How this type of frameworks is quite simple. Because of the excess amount of acetylene that is added to the flame, there is what is referred to as a “feather” extension added to the inner core. As the flow of acetylene is decreased or the amount of oxygen is increased, this feather disappears. When the feather has disappeared, the neutral flame begins.

This neutral flame is achieved when there is an equal amount of oxygen and acetylene gas that is used. It is important to note that this does not have to be an absolute one-to-one match. It must be close, however. To achieve this match, it is common to increase the opening of the oxygen valve slowly until the match has been created.

For those looking for a perfect neutral flame, there should be no whitish looking streamers present at the end of the column. Some prefer to leave a slight acetylene streamer, that is as much as 1/16 to 1/8 of an inch long. This helps to ensure that the flame is not oxidizing. The adjustment of the flame is performed most often when preheating the flame just prior to the cutting operation.

When one is welding using a neutral flame, the molten metal puddle is quiet and clear. The metal should flow easily without foaming, sparking, or boiling. The neutral flame usually reaches a temperature around 5850°F with the end of the outer sheath dropping in temperature to about 2300°F. This variation in flame allows for some degree of temperature control during the weld.

Carburizing Flame

In the carburizing flame, there is an increased amount of acetylene. This gives the inner core a feather edge. In this case, the white feather is referred to as “acetylene feather.”

There are some terms that are important to understand related to the carburizing flame. The first of these relates to the size of the feather. When it is twice as long as the inner core, then it is known as a 2X flame. When referred to in this way, it tells the welder that there is twice as much acetylene that is being used. When using a carburizing flame carbon may be added to the weld metal.

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A carburizing or reducing welding flame is obtained when there is slightly less than one full volume of oxygen mixed with one volume of acetylene. This is why even when the welder is looking for a neutral flame, if there is a larger amount of acetylene in comparison to the oxygen and reducing welding flame is obtained.

As mentioned in the previous section, this flame is obtained by first adjusting the welding flame to reach a neutral position. Then, the amount of acetylene is slowly increased by turning the valve to allow more of the gas to enter. This creates the feather at the end of the inner core.

The length of the streamer gives you the degree of the flame carburization. In most welding operations using this type of flame, the streamer should be no more than half the length of the inner core.

While the neutral flame had two distinct zones, a carburizing flame has three. The first of these is the bluish-white inner core, followed by a light intermediate cone that indicates that there is an excess amount of acetylene. The final area is a light blue outer flare envelope.

The amount of heat generated by this type of welding flame reaches to about 5700°F at the inner core tip. When this type of flame is used, the metal boilers but is not clear. When steel is used, it is absorbing carbon from the flame, giving off heat in the process. This causes the metal to begin to boil. When the metal cools, it has the same properties of high carbon steel, which can mean they will be subject to cracking and brittleness.

This type of welding flame is the perfect choice for those who are welding high carbon steel or who are hard facing non-ferrous alloys, such as nickel. When this flame is used with silver solder or soft solder operations, only the intermediate and outer flame cones are used.

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Oxidizing Flame

Conversely to the carburizing flame, the oxidizing welding flame occurs when there is slightly more oxygen than acetylene. As with the carburizing option, the flame should first be adjusted to a neutral flame, then the amount of oxygen is increased until the inner core is shortened by about 1/10 of its original length.

You know that you have adjusted the flame properly when the inner core is pointed and has a slightly purplish color. You will also notice that there will be a distinct hissing sound that is made. It is quite recognizable, and you will know it once you initially identify it.

The oxidizing flame reaches a temperature of 6300°F at its inner core tip. That is the highest of any of the flame types we have talked about here. Oxidizing welding flames are commonly used with metals such as:

  • manganese steel
  • copper
  • zinc
  • cast iron

When the oxidizing flame is used with a metal, it causes the metal to foam and give off sparks. This tells the welder than excess amount of oxygen is combining with the steel, causing it to burn.

In most cases, you will find that in oxidizing flame should not be used for welding steel. This is because the metal that is deposited becomes porous, brittle, and oxidized. The flame ultimately ruins most metals, and is why it is not used in the vast majority of welds where steel is used.

Where you will find the oxidizing flame use most of is in the torch brazing of steel and cast iron. It is also used in the welding of brass or bronze.

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A Final Note
Now that you know the different types of welding flames, a little about the ratios of oxygen to acetylene is important. For the best carburizing flame, it should be about 0.8 of oxygen for every 1.0 of acetylene. The neutral flame should have the ratios at zero, while the amount of oxygen in the oxidizing flame can be as much as 2.5 times that of the acetylene.

FAQs

What are the different types of welding flames? ›

There are three types of flames natural flame, carburizing flame and oxidizing flame.

What are the 3 flame categories for brazing? ›

There are three basic flame types: neutral (balanced), excess acetylene (carburizing), and excess oxygen (oxidizing) as shown below.

What is the best flame for welding and cutting? ›

A Neutral Oxy Acetylene Flame is used for Welding, Brazing and Silver Soldering most metals and is therefore the most common type of flame to use. A Neutral Flame is also used for Oxy Acetylene Cutting.

What is a carburising flame? ›

A reducing oxyfuel gas flame in which there is an excess of fuel gas, resulting in a carbon rich zone extending around and beyond the cone. A carburizing flame is used in hardfacing and similar processes to obtain fusion between base metal and weld metal without deep melting of the base metal.

What is the hottest flame in welding? ›

The outer envelope is small and narrow. Oxidizing flames also produce a distinct hissing sound as you open the oxygen valve. When adjusted properly, the inner cone can reach 6300 degrees Fahrenheit, making the oxidizing flame the hottest flame for gas welding.

What type of flame is used for cutting steel? ›

The neutral flame is the flame most generally used when welding or cutting. The welder uses the neutral flame as the starting point for all other flame adjustments because it is so easily defined.

What is a swirl flame? ›

Swirl Flame. Also known as Turbo, Tornado or Vortex Flame. A pencil or general purpose flame has a primary and secondary flame, just like a candle. The swirl flame holder acts like a tornado, creating a vortex to mix the primary and secondary flames together.

What flame is best for brazing? ›

Preferred Torch Brazing Flame Types - YouTube

What is the best flame for welding aluminum? ›

Generally, oxy-acetylene flame with neutral or slightly reducing nature is used for welding aluminium. Oxy-acetylene flame is less malleable and less prone to cracking which makes it easier to weld a soft metal like aluminium with this flame. While there are 4 methods to weld aluminium viz.

Which flame is used for preheating? ›

Acetylene. Acetylene generates the hottest flame of all flammable gases, reaching around 3,100 °C when combined with oxygen.

What is the difference between a harsh flame and a quiet flame? ›

What is the difference between a harsh flame and a quiet flame? A harsh flame is produced by using too much pressure of both gases to the tip, and it is noisy; a quiet flame has the correct amount of pressure and it does not make any noise.

What is a neutral flame in welding? ›

An oxyfuel gas flame that is neither oxidizing nor reducing. It is a quiet and clean flame obtained by burning approximately 50% acetylene and 50% oxygen. See also Carburizing Flame, Oxidizing Flame, Reducing Flame and Oxyfuel Gas Welding.

What does an oxidizing flame look like? ›

If the flame has too much oxygen, an oxidizing flame is produced. When the amount of oxygen increases, the flame shortens due to quicker combustion, its color becomes a more transparent blue, and it hisses/roars.

What is oxidizing flame in welding? ›

An oxyfuel gas flame in which there is an excess of oxygen, resulting in an oxygen-rich zone extending around and beyond the cone. See also Carburizing Flame, Neutral Flame, Reducing Flame and Oxyfuel Gas Welding.

What is meant by oxidizing flame? ›

Definition of oxidizing flame

: a flame or the part of a flame having an excess of oxygen (as the outer cone of a gas flame)

Are blue flames hottest? ›

The hottest part of the flame is the base, so this typically burns with a different colour to the outer edges or the rest of the flame body. Blue flames are the hottest, followed by white. After that, yellow, orange and red are the common colours you'll see in most fires.

Is blue part of flame hottest? ›

Although red usually means hot or danger, in fires it indicates cooler temperatures. While blue represents cooler colors to most, it is the opposite in fires, meaning they are the hottest flames. When all flame colors combine, the color is white-blue which is the hottest.

What Colours can fire be? ›

Generally, the color of a flame may be red, orange, blue, yellow, or white, and is dominated by blackbody radiation from soot and steam.

Which flame is used for copper welding? ›

Uses of Oxidizing Flame

This flame is used for welding copper, zinc, cast iron, brass.

Which flame is used in gas welding? ›

Neutral Flame- The neutral flame contains a one-to-one ratio of acetylene and oxygen. It receives additional oxygen from the air & provides complete combustion. It is generally preferred for welding.

Which of the following flame is harmful to steel? ›

6. Which of the following flame is harmful to steel? Explanation: Oxidizing flame is harmful to steel. An oxidizing flame should not be used for welding steel because the deposited metal will be porous, oxidized and brittle.

What is a webbed flame? ›

The versatile webbed flame assists you to complete a variety of household projects, including small diameter soldering, thawing, melting and various other heat applications. Constructed with brass, you get a longer durability and quality.

How do you make swirls? ›

2. Swirl generation techniques
  1. Use of fins or adjustable propellers tangentially deflecting the axial flow. ...
  2. Rotating mechanical devices which generate a rotational movement to the fluid passing between them [10].
  3. Tangential injection of part or all fluid quantity into a main duct.
Jun 26, 2019

What is a low swirl burner? ›

One technology that is relatively tolerant to fuel composition changes is the low swirl burner (LSB), also called low swirl injector (LSI). The LSB stabilizes a lifted flame in a velocity flow field that linearly decays along the centerline [24], [25], [26].

What temperature do you braze? ›

Most brazing processes run at temperatures between 800°F and 2,000°F. For a strongest braze joint, the metals that are being joined together need to be at close to the same temperature.

What does an oxidizing flame look like? ›

If the flame has too much oxygen, an oxidizing flame is produced. When the amount of oxygen increases, the flame shortens due to quicker combustion, its color becomes a more transparent blue, and it hisses/roars.

Which flame is used in gas welding? ›

Oxy-acetylene flame is mostly used for gas welding because of its high flame temperature (3200 °C). Oxygen is generated by liquefaction of air or by electrolysis of water and acetylene is produced as a result of a chemical reaction of calcium carbide in contact with water.

Which of the following flame is the hottest? ›

The correct answer is the Non-luminous zone. ​ The Hottest part of the gas flame is known as the Non-luminous zone. The Non-luminous zone flame is blue. In this zone, complete combustion of the fuel takes place because there is plenty of air around it.

What is the best flame for welding aluminum? ›

Generally, oxy-acetylene flame with neutral or slightly reducing nature is used for welding aluminium. Oxy-acetylene flame is less malleable and less prone to cracking which makes it easier to weld a soft metal like aluminium with this flame. While there are 4 methods to weld aluminium viz.

What is a neutral flame in welding? ›

An oxyfuel gas flame that is neither oxidizing nor reducing. It is a quiet and clean flame obtained by burning approximately 50% acetylene and 50% oxygen. See also Carburizing Flame, Oxidizing Flame, Reducing Flame and Oxyfuel Gas Welding.

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.

What does flux do 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 of the following flame is harmful to steel? ›

6. Which of the following flame is harmful to steel? Explanation: Oxidizing flame is harmful to steel. An oxidizing flame should not be used for welding steel because the deposited metal will be porous, oxidized and brittle.

What is the difference between reducing and oxidizing flame? ›

The key difference between oxidizing and reducing flame is that oxidizing flames are produced in the presence of an excessive amount of oxygen, whereas reducing flames are produced in the presence of a low level of oxygen. Oxidizing flames can oxidize metal surfaces while reducing flames can reduce molten metal.

What does AC and DC stand for in welding? ›

These types of welding involve the creation of an electric arc between an electrode and the metal being welded. The electric arc provides heat to fuse the metals together. A power supply is used to generate the arc, which can either use an alternating current (AC) or a direct current (DC).

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