What is Welding Flame?- Neutral, Carburizing & Oxidizing - Engineering Choice (2022)

Today we will learn about the types of welding flames used in gas welding. In my last post, we have discussed gas welding. In this welding process gases, fuels are burned and produce high-temperature flames which are further used to create a weld joint.

The flame plays lead role to create weld joint and the weld properties are highly depended on it. 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 materials used different flames according to weld condition.

What is Welding Flame?

Welding flame is used to heat metal or thermoplastics, fusing them as they cool. Most gas welding processes use oxyfuel welding. It’s one of the oldest welding processes, first developed in 1903. With oxyfuel welding, which is also called oxyacetylene welding, you need a liquid fuel or gas, such as acetylene. The gas is combined with oxygen to increase the temperature of the flame.

The torch has hoses that connect to gas tanks. When I’m ready to start welding, I open the valves and ignite the gas as it exits the torch. I can then adjust the valves to adjust the flow of each gas, altering the gas ratio.

Each flame also has several zones called cones. The inner cone is the hottest part of the flame. It’s where acetylene and oxygen combine. The outer cone is cooler as it gets more oxygen from the surrounding air. It’s also commonly called the outer envelope or sheath.

What is Welding Flame?- Neutral, Carburizing & Oxidizing - Engineering Choice (1)

Types of Welding Flames

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

(Video) Differences between Carburizing Flame and Oxidizing Flame.

  • Natural flame has a synchronized mixture of fuel and oxygen,
  • The carburizing flame has more fuel and,
  • Oxidizing flame has more oxygen..
What is Welding Flame?- Neutral, Carburizing & Oxidizing - Engineering Choice (2)

As we know there are three basic welding flames. These areas follow.

1. Natural Flame

As the name implies, this flame has an equal amount of oxygen and gases fueled by volume. This flame burns fuel completely and does not produce any chemical effect on the metal to be welded. It is mostly used for welding mild steel, stainless steel, cast iron, etc. It produces little smoke.

This flame has two zones. The inner zone has white in color and has a temperature of about 3100-degree centigrade and the outer zone has a blue color and has a temperature of about 1275 degrees centigrade.

2. Carburizing Flame

This flame has an excess of fuel gas. This flame chemically reacts with metal and form metal carbide. Due to this reason, this flame does not use with metal which absorbs carbon. It is a smoky and quiet flame. This flame has three regions.

The inner zone has white color, the intermediate zone which is red in color and the outer cone has a blue color. The inner cone temperature is about 2900 degrees centigrade. This flame is used to weld medium carbon steel, nickel, etc.

(Video) Types of Welding Flames | Neutral flame, Carburizing flame, Oxidizing flame.

3. Oxidizing Flame

When the amount of acetylene reduces from natural flame or the amount of oxygen increases, the inner cone tends to disappear and the flame obtained is known as oxidizing flame. It is hotter than natural flame and has clearly defined two zones.

The inner zone has a very bright white color and has a temperature of about 3300 degrees centigrade. The outer flame has blue in color. This flame is used to weld oxygen-free copper alloys like brass, bronze, etc.

What Type of Gas Should You Use for an Ideal Flame?

Acetylene is the most used gas for producing the types of gas welding flames discussed but it’s not the only option. MAPP and hydrogen are often listed as alternatives to acetylene. Acetylene has a “triple bond” that uniquely bonds carbon atoms.

When other gases reach their ignition temperatures, the bond breaks. The gases then absorb energy. When the bond breaks in acetylene, it releases energy. This allows acetylene to achieve higher temperatures.

Compared to other gases, acetylene also has fewer oxidizing characteristics. However, it also ignites easily. MAPP was created as a safer option. MAPP gas is a liquified petroleum gas combined with propane and acetylene. It can be shipped in smaller containers compared to standard acetylene, has a higher ignition temperature, and works with much higher pressures.

The drawback to MAPP is the temperature. The flames produced using MAPP achieve lower temperatures compared to acetylene flames. It’s not suitable for use with most steels but may work well for aluminum. Hydrogen is another gas that welds aluminum easily. As with MAPP, hydrogen flames reach lower temperatures and work with higher pressures.

(Video) Differences Between Carburizing or reducing Flame and Oxidising Flame

Unless you plan on fusing aluminum, stick with acetylene. The low temperature and withdrawal rate keep MAPP and hydrogen from properly fusing harder metals. While MAPP and hydrogen aren’t the best choices for gas welding, they’ve become popular options for gas cutting. When used with a high-pressure torch, MAPP and hydrogen provide cleaner cutting.

The lower temperatures also make MAPP and hydrogen common choices for heating, bending, and brazing.

Common Ratios for Producing Oxyacetylene Flames

Neutral gas welding flames have an equal mixture of oxygen and gas. Carburizing flames have less oxygen while oxidizing flames contain more oxygen. So how do you determine the ratio?

No matter the project, start with a neutral flame. The carburizing flame and oxidizing flame are created by increasing the release of acetylene or oxygen after achieving a neutral flame.

I created the following list to break down the typical ratio of oxygen to acetylene for each flame:

  • Carburizing flame: 0.8 to 1.0
  • Neutral flame: 0
  • Oxidizing flame: 1.0 to 2.5

As you increase the flow of acetylene, the distinct feather starts to extend from the inner cone. The feather should reach about two or three times the length of the inner cone. Preventing the gas from fully combusting also lowers its temperature.

(Video) How to get a neutral flame on a gas welder - Quick Reference to go with the long safety/set up video

If you need an oxidizing flame, you increase the flow of oxygen instead of increasing the flow of acetylene. The extra oxygen produces the oxidizing effect and allows the gas to combust faster, resulting in higher temperatures.

How Do You Create a Neutral Flame for Gas Welding?

As the neutral flame is the starting point for creating other flames, it’s the first flame that I learned how to produce. Start by adjusting the regulators. The oxygen cylinder and acetylene cylinder each have a regulator with two gauges. One gauge tells you the remaining pressure while the other displays the working pressure.

Adjusting the screw on the regulator adjusts the working pressure, allowing you to increase or decrease the flow of oxygen or gas. Before lighting the torch, stand away from the front of the regulators and slowly open the oxygen cylinder and then the acetylene cylinder. Turn the regulator screws to adjust the pressure settings.

With the pressure on the regulators set, you can light and adjust the torch. Open the acetylene valve a quarter turn and ignite the torch. Slowly open the oxygen valve until you see three distinct zones. You should see the inner cone, the feather-shaped acetylene cone, and the outer envelope. Continue to slowly open the oxygen valve until the feather disappears into the inner cone. You now have a neutral flame.

To create a carburizing flame, slowly open the valve on the acetylene cylinder until the feather reaches two to three times the length of the inner cone. To create an oxidizing flame, increase the flow of oxygen until the inner cone is about a quarter of its original size. You should also hear the distinct hissing sound.

(Video) The Carburizing Flame for Brazing

Related Posts


What is flame in welding? ›

The flame plays lead role to create weld joint and the weld properties are highly depended on it. 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.

What is the application of oxidizing flame neutral flame and carburizing flame? ›

A carburizing flame will produce iron carbide, causing a chemical change in steel and iron. For this reason a carburizing flame is not used on metals that absorb carbon. An oxidizing flame is hotter than a neutral flame and is often used on copper and zinc.

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.

What is difference between oxidizing flame and carburizing flame? ›

Carburizing flame is obtained when less oxygen than that is required for stoichiometrically complete combustion is supplied. Oxidizing flame is obtained when excess oxygen than that is required for stoichiometrically complete combustion is supplied.

What is a carburizing 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 a welding process? ›

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.

What are the uses of neutral flame? ›

Neutral flames are used to weld both ferrous and nonferrous metals such as mild steel, cast iron, copper, stainless steel, aluminum, etc. welder are expected to adjust to neutral before any other flame. The flame is indicated from its inner cone consisting of a luminous cone that is bluish-white.

What are the advantages of oxidising and reducing flames? ›

Oxidizing flames can oxidize metal surfaces while reducing flames can reduce molten metal. Thus, oxidizing flames are not suitable for soldering and annealing purposes, but reducing flames are ideal for these two applications.

How many types of welding are there? ›

The four main types of welding are: Gas Metal Arc Welding (GMAW/MIG), Gas Tungsten Arc Welding (GTAW/TIG), Shielded Metal Arc Welding (SMAW), and Flux Cored Arc Welding (FCAW).

What is meant by neutral flame? ›

Definition of neutral flame

: a flame resulting from the burning of gases supplied in the proper proportions for perfect combustion (as approximately equal volumes of acetylene and oxygen)

Why is oxidizing flame used? ›

The oxidizing flame is mainly used for welding brass. It is also very suitable for the cutting operations due to nonferrous metals (brasses and bronzes) due to formation of a tenuous oxide film over the molten metal which prevents the vaporization of zinc.

What is the difference between a neutral flame and carburizing flame? ›

Types of Welding Flames | Neutral flame, Carburizing flame, Oxidizing ...

What is the Colour of neutral flame? ›

A flame with a good oxygen-fuel ratio is called a neutral flame. The color of the flame is semi-transparent purple or blue. This flame is optimal for all intentions, because it does not oxidize or get soot onto surfaces.

Which flame is used in gas welding? ›

Flame 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.

How hot is a neutral flame? ›

Table of comparison:
CharacteristicsNeutral flameReducing flame
Inner temp in oC3250 approx2900 approx
Intermediate temp oC2100 approx2500 approx
Outermost temp in oC1300 approx1275 approx
NoiseHissing noiseNo noise
1 more row

Which flame is used for welding steel? ›

Statement (I): In gas welding process, neutral flame is the most common flame used for welding and cutting stainless steel.

How is carburizing done? ›

Liquid or cyanide carburising is carried out by placing the component in a salt bath at a temperature of 845 to 955°C. The salt is usually a cyanide-chloride-carbonate mixture and is highly toxic. The cyanide salts introduce a small amount of nitrogen into the surface which further improves its hardness.

Why is welding used? ›

The basic purpose of welding is to join two elements together with a firm connection. Welders typically work with metal or thermoplastic and use durable filler material to bind them together. Welding is used to create many modern constructions in our world, such as skyscrapers, cars, ships and airplanes.

What are the 3 types of welding? ›

Three of the most common are Arc, MIG (Metal, Inert Gas) or GMAW (Gas, Metal Arc Welding), and TIG (Tungsten Inert Gas) welding. In order to know which process is best for the particular job you're working on, here's what you should know about each of them. Arc welding is the oldest of these three welding processes.

What is used for welding? ›

Welders use stainless steel, carbon steel, and low-carbon mild steel, depending on the project. Mild steel is especially ductile, which makes it easy to weld. The more carbon steel has, the more effort it takes to weld, though welding carbon steels still happens with the proper equipment and methods.

What is the most common welding process? ›

Gas Metal Arc Welding (GMAW/MIG)

This method requires a constant voltage and direct-current power source, and is the most common industrial welding process which includes plate and large bore pipe.

What are different types of welding joints? ›

There are five basic welding joint types commonly used in the industry, according to the AWS:
  • Butt joint welding.
  • Tee joint welding.
  • Corner joint welding.
  • Lap joint welding.
  • Edge joint welding.
2 Sept 2020

What color is the oxidizing flame? ›

An oxidizing flame is any flame that has an excess of oxygen present. A hissing noise, sharp candles, and a paler blue color easily identify the flame. This flame is cooler than a neutral flame because there is an excess of oxygen flowing though the combusting gasses.

How many zones are in carburizing flame? ›

This flame has 3 zones i.e. bright luminous inner zone, acetylene feather and outer blue envelope.

Is oxidizing flame the hottest? ›

Carbonizing flames are cooler and often used when working with steel or iron. Oxidizing flames are the hottest and least used, due to the oxidation of the base material.

Which welding is best? ›

Gas Tungsten Arc Welding (TIG) is probably the highest quality and most expensive of the arc welding processes. It is generally performed manually; however, there are some automatic applications. A good welder can deposit ½ pound of weld metal per hour at about 1-to-3-inches-per-minute travel.

What are welders called? ›

Welders are also known as: Aluminum Welder Fabrication Welder Maintenance Welder Sub Arc Operator Welder Operator.

How are welding classified? ›

Welding is broadly divided into three groups: fusion welding, pressure welding, and brazing/soldering, each of which is made up of many welding methods.
Resistance welding:
  1. Resistance spot welding.
  2. Projection welding.
  3. Seam welding.
  4. Upset welding.
  5. Flash 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 is the ratio of carburizing flame? ›

Carburizing Flame:

​The carburizing flame has a 0.85:0.95 ratio of oxygen and acetylene by volume.

Which flame is used for cutting? ›

The neutral flame is the flame most generally used when welding or cutting.

How do you make a neutral flame? ›

How to Light and Set a Neutral Flame with a Gas Torch | ESAB Elite

What is oxidizing zone? ›

An oxidation zone is part of a metalliferous deposit situated below the water table. In this zone the primary ore is highly weathered by rainwater, leading to the formation of secondary oxide , hydroxide, carbonate, sulphate, arsenate, native metal enrichments etc.., which can be economically workable (e.g. gossan).

What steel is neutral flame suitable for? ›

Among the three, mild steel is welded using neutral flame mainly because it is 50% acetylene and 50% oxygen making it easily defined both literally and chemically. The flame is preferred for its inert nature when it comes to dealing with metals.

What is the working principle of gas welding? ›

#Principle: Gas welding is a most important type of welding process. It is done by burning of fuel gases with the help of oxygen which forms a concentrated flame of high temperature. This flame directly strikes the weld area and melts the weld surface and filler material.

What is the difference between combustion and flame? ›

What is the difference between combustion and flame?
1. Combustion is a chemical reaction of carbon-based material with oxygen.Flame is the visible part of the fire
2 more rows

What Colour is a flame? ›

Color tells us about the temperature of a candle flame. The inner core of the candle flame is light blue, with a temperature of around 1670 K (1400 °C). That is the hottest part of the flame. The color inside the flame becomes yellow, orange, and finally red.

What is reducing zone in welding? ›

Welding: When burned in oxygen, acetylene produces a reducing zone, which easily cleans the metal surface. However, propane doesn't have a reducing zone. This property makes it unsuitable for welding. Today, oxy-acetylene welding is employed for high strength steels.

What is a flame in chemistry? ›

A flame (from Latin flamma) is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density they are then considered plasma.

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).

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 CO2 gas used for 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.

Which flame is used for welding aluminium? ›

Neutral flame produces a hissing sound and the flame is used to weld low Carmon steels and aluminium.

What is the temperature of gas welding? ›

Process features. Oxyacetylene welding, commonly referred to as gas welding, is a process which relies on combustion of oxygen and acetylene. When mixed together in correct proportions within a hand-held torch or blowpipe, a relatively hot flame is produced with a temperature of about 3,200 deg. C.

What is an example of a flame? ›

The definition of a flame is burning gas, fire or blaze, or a strong passion. An example of a flame is a fire from a lighter.

What is flame made of? ›

Most flames are made of hot gas, but some burn so hot they become plasma. The nature of a flame depends on what is being burnt. A candle flame will primarily be a mixture of hot gases (air and vaporised paraffin wax). The oxygen in the air reacts with the paraffin to produce heat, light and carbon dioxide.

What is the difference between fire and flame? ›

Flame is a stream of hot, burning gas from something on fire. Fire (material that is in) the state of burning that produces flames that send out heat and light, and might produce smoke.

What colour is a flame? ›

Color tells us about the temperature of a candle flame. The inner core of the candle flame is light blue, with a temperature of around 1670 K (1400 °C). That is the hottest part of the flame. The color inside the flame becomes yellow, orange, and finally red.

What do you mean flame? ›

Definition of flame

(Entry 1 of 2) 1 : the glowing gaseous part of a fire. 2a : a state of blazing combustion the car burst into flame. b : a condition or appearance suggesting a flame or burning: such as. (1) : burning zeal or passion.

What is the full meaning of flame? ›

The acronym FLAMES stands for Friends, Lovers, Affectionate, Marriage, Enemies, and Siblings.

How hot is a flame? ›

Deep red fire is about 600-800° Celsius (1112-1800° Fahrenheit), orange-yellow is around 1100° Celsius (2012° Fahrenheit), and a white flame is hotter still, ranging from 1300-1500 Celsius (2400-2700° Fahrenheit). A blue flame is the hottest one of all, ranging from 1400-1650° Celsius (2600-3000° Fahrenheit).

How flame is produced? ›

Fire is the result of a chemical reaction called combustion. At a certain point in the combustion reaction, called the ignition point, flames are produced. Ordinarily, flames consist primarily of carbon dioxide, water vapor, oxygen, and nitrogen.

Is a flame a gas? ›

Fire is a plasma, not a gas or a solid. It's a kind of transient state between being composed of the elements prior to ignition and the spent fumes (Smoke - solid particles and Gasses = Gas molecules.)

What is fire flame? ›

A flame (from Latin flamma) is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density they are then considered plasma.

Is a flame matter? ›

Since matter can be defined as “anything which occupies space and has mass or weight”, we can say that fire is a 'matter' because it occupies space and since it is a mixture of gases, it must have some mass. The light and the heat produced by the flame is energy.

Which fire is hotter? ›

Blue flames are the hottest, followed by white. After that, yellow, orange and red are the common colours you'll see in most fires. It's interesting to note that, despite the common use of blue as a cold colour, and red as a hot colour – as they are on taps, for instance – it's the opposite for fire.

What is the hottest flame? ›

Violet is the hottest color fire. It can burn at around 3,000 degrees Fahrenheit (1,650 degrees Celsius). That's hot enough to burn almost any material and a violet flame is often seen in welding and cutting operations for this reason. But that isn't the only fire that can reach these higher temperatures.

Why gas flame is red? ›

Red or yellow flames means there could be a problem, such as incomplete combustion. This color is caused by very fine soot particles produced by the flame, which burns at nearly half the temperature it is supposed to.


1. Oxyfuel Welding Flame Type
(Jared T)
2. Oxy Acetylene Brazing, Torch Adjustments- Reducing Flame, Oxidizing Flame, Neutral Flame
(AC Service Tech LLC)
3. Types of flames | Gas Welding
(The Learning Hub)
4. types of flames | types of flames in gas welding | types of welding flames | gas welding
(Modi Mechanical Engineering Tutorials)
5. Firepower How-to: Setting a Neutral Flame - Cutting Attachment
(Firepower Metal Cutting & Welding Equipment)
(Mechanical Nexus)

Top Articles

You might also like

Latest Posts

Article information

Author: Jonah Leffler

Last Updated: 10/13/2022

Views: 6475

Rating: 4.4 / 5 (65 voted)

Reviews: 80% of readers found this page helpful

Author information

Name: Jonah Leffler

Birthday: 1997-10-27

Address: 8987 Kieth Ports, Luettgenland, CT 54657-9808

Phone: +2611128251586

Job: Mining Supervisor

Hobby: Worldbuilding, Electronics, Amateur radio, Skiing, Cycling, Jogging, Taxidermy

Introduction: My name is Jonah Leffler, I am a determined, faithful, outstanding, inexpensive, cheerful, determined, smiling person who loves writing and wants to share my knowledge and understanding with you.