Shielding Gas in Laser Welding: The Most Comprehensive Guide

1. Laser welding gas

When using laser welding, shielding gas will be used to improve the welding effect and avoid sediment accumulation on laser tools.

It can be divided into:

  • auxiliary gas (MDE gas)
  • shielding gas
  • jet gas

Auxiliary gas is very helpful when welding with yttrium aluminum garnet laser.

The gas inhibits the absorption of laser beam in metal vapor plasma.

The shielding gas squeezes out the air at the welding position to prevent a reaction with the components in the air.

Jet gas is used in welding applications that produce large amounts of spatter and steam.

The air curtain transmits the air curtain gas to the machining head at an angle of 90 ° through the nozzle to protect the machining head from spatter and mist during welding.

The wind curtain will not affect the metal melt and shielding gas.

2. What is the role of shielding gas?

The laser generates a laser beam to generate the energy necessary for the welding process.

The energy is guided to the joint position of the workpiece through the steering mirror, laser optical cable and focusing device.

Arrange and fix the workpiece so that the focused laser beam can be accurately guided to the joint position.

The focusing optical element moves over the workpiece along the seam position.

The high power density of the laser beam at the focus makes the material melt and a small part of the material is gasified.

The pressure of the metal vapor flowing out is so high that a small vapor hole, the so-called “keyhole”, is formed in the material.

The keyhole enters the material several millimeters deep.

If the focus lens is moved above the workpiece at this time, the lock hole will also move under the focus lens.

Then the molten metal flows together.

The melted and fully mixed material cools down and the melt solidifies into a narrow weld.

Many metals react with components in the air in a molten state.

This results in damage to the welding quality.

The shielding gas extrudes the components in the air, which has a positive effect on the characteristics of the weld.

3. Shielding gas

Inert (inert) gas is mainly used in metal laser welding.

The inert gas does not react or rarely reacts with the matrix material.

The following shielding gases are recommended:

  • Nitrogen (N2)
  • Argon (AR)
  • Helium (he)

Gas purity: industrial gases generally contain a small number of impurities.

The purity of the gas is given by a digital system.

The first number = the number of nine in the percentage value.

The second number = the last digit of the percentage value

Example: he 4.6 = helium purity of 99.996% (volume percentage)

The service life of gas cylinder: the service life of gas cylinder can be easily calculated.

Welding gas is supplied by storing it in gas cylinders.

A gas storage cylinder usually contains 50 liters of gas at a pressure of 200 bar.

gas storage cylinder

  • T: Service life
  • V: Volume of gas cylinder
  • P: Inflation pressure
  • Q: Unit gas consumption


V = 50l,p = 200bar,Q =40l/h → T = 50l • 200bar/40l/h = 250 h

Nitrogen (N2)

Nitrogen is a colorless and tasteless inert gas.

Nitrogen is suitable for welding chromium-nickel steel.

However, it is not suitable for use with zirconium alloy and titanium material because although it is inactive, it can also form compounds with these materials.

When welding steel with nitrogen, it should be noted that nitrogen slightly reduces rust resistance by dissolving chromium and nickel from the steel.


The following table gives an overview of the recommended shielding gases.

Ar He N2 Note
Aluminum & Aluminum alloy + Smooth and glossy welds can be formed with hydrogen or hydrogen mixture.

The use of hydrogen will cause pores in the material

Hydrogen-containing gas will cause pores in the material

Very high quality welds can be formed when welding with carbon dioxide (CO2) or hydrogen/carbon dioxide mixture. However, the smoothness and gloss of these welds are slightly poor.

Chromium nickel steel + + It is recommended to use argon on devices that are prone to overflow gas because it is heavier than nitrogen.If corrosion is to be avoided, argon must be used because nitrogen reacts with chromium and nickel in the material.
Titanium and titanium alloys + + Titanium reacts strongly with components in the air. As long as the weld temperature after cooling is still 200 ℃, it is necessary to completely cover the solution pool with argon (for example, a glove box can be used)
Chromium alloy +
Copper It is generally not necessary to use shielding gas when welding copper.

Suggestions for protective gas of raw materials: “+” = yes, “-” = no


When welding on narrow devices, self-protection is caused by the extrusion of oxygen in the environment by metal vapor.

In this case, it is not necessary to use shielding gas.

4. Shielding gas input

The ways to input shielding gas into the processing position are:

  • Pass through nozzles
  • Clamping device through workbench

The following parameters must be optimally set for use:

  • Type of gas, pure gas or mixed gas
  • Incident angle
  • Incident range
  • airflow
  • Nozzle geometry.

The input of shielding gas must be adjusted according to the type of laser (continuous or pulsed), welding speed and weld.

TRUMPF provides some nozzles as standard, which will be further described below.

Linear gas supply

Linear nozzle is a further development of compound pipe, in which each pipe is assembled.

The linear nozzle has the following advantages:

  • Better weld quality.
  • The structure is more compact, resulting in less interference with the contour.
  • It can be used even if the nozzle is far away from the workpiece.


  • CW laser
  • Objective lens focal lengths f = 150 mm, f = 200 mm, f = 250 mm and F = 300 mm.

Linear gas supply

Welding application:

The linear nozzle is suitable for linear weld welding:

  • Butt weld.
  • Fillet weld.

Linear gas supply with lateral MDE nozzle

With this nozzle, the shielding gas can be transported in a straight line, and the metal vapor effect can be eliminated through the lateral MDE nozzle.


  • CW laser
  • Objective lens focal lengths f = 150 mm, f = 200 mm, f = 250 mm and F = 300 mm.

Linear gas supply with lateral MDE nozzle

Welding application:

Linear nozzle is suitable for linear weld welding:

  • Butt weld.
  • Fillet weld.

Bubbling nozzle gas supply

The conical nozzle contains a ray regulator.

The ray regulator ensures laminar flow and uniform distribution of shielding gas.

Bubbling nozzles may be used when the following preconditions are met:

  • CW laser
  • Pulsed laser.
  • Objective lens focal lengths f = 150 mm, f = 200 mm, f = 250 mm and F = 300 mm.

Bubbling nozzle gas supply 

Welding application:

The bubbling nozzle can realize large-area laminar gas supply when the beam power and welding speed are small.

Conical nozzles provide a uniform distribution of shielding gas, especially in difficult-to-reach locations.

It is recommended to keep a distance of 8 – 12 mm and an angle of 30 ° – 50 ° from the workpiece according to the use.

Bubbling nozzles

Other methods

Glove boxes are recommended if the material is required to be well and evenly covered with shielding gas.

The glove box completely covers the working range and the protective gas cannot overflow.

The shielding gas nozzle is not required because the glove box is completely filled with shielding gas.

5. Layout of shielding gas nozzle

There are two different welding processes for laser welding:

For thermal conductivity welding, the material melts only on the surface.

The resulting weld is a few tenths of a millimeter deep.

The welding process is mainly used for pulsed Nd: YAG laser.

In contrast to thermal conductivity welding, deep penetration welding produces deep and narrow welds.

Deep penetration welding is carried out by Nd: YAG laser in continuous wave operation mode.

Layout of shielding gas nozzle

Pulsed laser

In order to obtain the best welding results by pulse laser, the welding wire (if used) is usually inserted slowly (first).

The input direction of shielding gas can be freely selected.

Pulsed laser

CW laser

In order to obtain the best welding results through the continuous wave laser, it is necessary to input the shielding gas forward (push) and slow down (advance) the welding wire input (if used).

CW laser

Welding on edges

The shielding gas input nozzle must be arranged to produce a laminar uniform air flow.

Especially when welding on the edge, the vortex will be generated, which will bring oxygen in the environment into the welding position.

If the oxygen content is > 0.5%, the material can react with oxygen. If welding is carried out on the edges, the airflow vortex on the edges can be prevented by installing buffer plates.

Welding on edges

6. Protective gas metering

The correct measurement of shielding gas is very important to achieve the best welding results.

Ideally, laminar airflow flows evenly above the processing point.

If too little shielding gas is input, it cannot fully protect and moisture in gas or air will enter the weld.

Too much shielding gas will create vortices, which will bring air into the welding position.

Protective gas metering

The color of the weld can indicate the amount of shielding gas used.

If the weld turns gray, it indicates that shielding gas is not used. If the weld turns yellow, the metering must continue to be optimized.

If the shielding gas has been optimally metered, a high gloss weld will be formed.

measurement of shielding gas Shielding Gas in Laser Welding: The Most Comprehensive Guide 1 Shielding Gas in Laser Welding: The Most Comprehensive Guide 2

The shielding gas nozzle with ray regulator can make the shielding gas flow out evenly. The same effect can be achieved through the steel wool in the nozzle.

shielding gas nozzle with ray regulator

Transverse air curtain:

Wind curtains can be used in welding applications that produce large amounts of spatter and steam.

The air curtain must be set so that the shielding gas is not affected by the airflow of the air curtain.


Through a simple test, you can determine whether the jet gas has been optimally set: keep a piece of paper above the workpiece and set the air pressure of the jet so that the paper will not be pressed down or inhaled by the jet.

7. Role of shielding gas

Different shielding gases have different effects. They affect the shape of the weld and can form a smoother and more shiny weld surface.

The selection of different shielding gases will affect the formation of pores in the weld and spatter. Shielding gas will hinder the coupling of laser beam!

Ar He N2 No protection gas
Welding shape

b = width

T = depth

Shielding Gas in Laser Welding: The Most Comprehensive Guide 3 Shielding Gas in Laser Welding: The Most Comprehensive Guide 4 Shielding Gas in Laser Welding: The Most Comprehensive Guide 5 Shielding Gas in Laser Welding: The Most Comprehensive Guide 6
Weld surface ++ + +
Spatter + + 0
Stoma ++ + +
Laser beam coupling +
Cost 0 Less

In order to achieve the best effect of shielding gas, it is necessary to open the shielding gas approximately briefly before and after welding.

After opening the shielding gas, it takes a certain time for the gas to reach the workpiece.

The melt still cooling after welding needs to be covered with shielding gas for a short time.

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