The Critical Role of Argon in Laser Welding

In fiber laser cutting production and processing, the choice of auxiliary gases varies significantly depending on the material. Different cutting thicknesses also require different gas pressures and specifications. Cost-wise, oxygen (O₂) used for cutting carbon steel is relatively inexpensive, while nitrogen (N₂) consumption for cutting stainless steel is substantial. The harder the stainless steel, the higher the required N₂ volume and purity—leading to increased costs.

Primary Gases Used in Laser Cutting Machines:

1. Laser Gas (Gas used inside the laser resonator to generate the laser beam.)

2. Compressed Air (Typically used to protect the laser path; some manufacturers also use it to generate shielding gases.)

3. Auxiliary/Process Gas (Gas ejected from the cutting torch nozzle.)

Oxygen in Carbon Steel Cutting:

Oxygen (purity generally >99.5%) is used for laser cutting carbon steel. Its main functions are to support exothermic burning and blow away molten slag. Required pressure varies among laser cutter manufacturers and depends heavily on nozzle type/size and material thickness. Typical pressure ranges from 0.3–0.8 MPa, with the torch section often around 0.02–0.05 MPa. Flow rates are significant; for example, cutting 22mm carbon steel may require up to 10 m³/h of oxygen (which also serves to protect the dual-layer torch).

Nitrogen in Stainless Steel Cutting:

Nitrogen is used for cutting stainless steel to prevent oxidation and remove slag. It demands very high purity (especially for stainless steel >8mm, often requiring ≥99.999%) and high pressure, typically above 1 MPa. For thicknesses exceeding 12mm or up to 25mm, pressure requirements increase to 2 MPa or higher. Flow rates are substantial and vary with torch type—e.g., cutting 12mm stainless steel may require ~150 m³/h, while 3mm may need below 50 m³/h.

Argon in Laser Welding:

Argon is employed during laser welding processes. It is ejected through a nozzle at a specific pressure onto the workpiece surface. Many may wonder why argon is used. Here, Shen Yuejia Gas’s technical experts explain the key reasons for using argon in laser welding:

Reason 1: Protects the Focusing Lens from Contamination

Argon shields the laser welding equipment’s focusing lens from contamination by metal vapor and spatter from liquiddroplets. This protection is especially critical in high-power welding, where ejecta are more intense.

Reason 2: Effectively Disperses Plasma Shielding in High-Power Welding

Metal vapor absorbs laser energy and ionizes into a plasma cloud. The surrounding argon, when heated, can also ionize. Excessive plasma can absorb and scatter the laser beam, reducing energy delivery to the workpiece. This plasma, acting as a secondary energy source on the surface, can shallow the weld penetration and widen the weld pool. Argon, with its high ionization energy, increases the recombination rate of electrons and ions through three-body collisions, thereby reducing plasma density. Its light atomic weight promotes higher collision frequency and faster recombination, without contributing significantly to plasma formation itself.

Reason 3: Prevents Workpiece Oxidation During Welding

Laser welding typically requires gas shielding. Setting the process to use argon synchronized with the laser prevents oxidation during continuous operation. While inert gas shielding protects the molten pool, and some materials may not require it if oxidation is not a concern, gases like helium, argon, or nitrogen are commonly used in most applications to ensure the workpiece remains free from oxidation during welding.