# Welding Shielding Gas Selection Chart for MIG, TIG and Flux Core > Source: https://netray.co/tools/welding-shielding-gas-selection-reference > Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems. > Section: Free Tools ## Short answer Lookup table of typical shielding and purge gases by welding process and base metal, with effect and caution notes. ## Category industry-templates ## Industry Welding & Fabrication ## Audience - Welding engineer - Welder - Buyer - Fabrication shop ## Tool **Kind:** worksheet **Mode:** reference **Columns:** #### Process **Key:** process **Type:** text #### Base metal **Key:** metal **Type:** text #### Typical gas **Key:** gas **Type:** text #### Effect **Key:** effect **Type:** text #### Caution **Key:** caution **Type:** text **Rows:** **Process:** GMAW short circuit **Metal:** Carbon steel **Gas:** 75-80% Ar, balance CO2 **Effect:** Stable arc, moderate penetration, low spatter **Caution:** Lack of fusion risk on thick plate if heat input is low **Process:** GMAW spray transfer **Metal:** Carbon steel **Gas:** 90-98% Ar, balance CO2 or O2 **Effect:** Smooth spray, good bead wetting **Caution:** Needs sufficient current to reach spray **Process:** GMAW **Metal:** Carbon steel **Gas:** 100% CO2 **Effect:** Deepest penetration, lowest gas cost **Caution:** More spatter and a rougher bead **Process:** GMAW pulsed **Metal:** Carbon steel **Gas:** 90-98% Ar, balance CO2 **Effect:** Spray quality with lower average heat **Caution:** Requires a pulse-capable power source **Process:** GMAW **Metal:** Austenitic stainless **Gas:** 98% Ar, 2% CO2 or Ar-O2 mix **Effect:** Limits carbon pickup and oxidation **Caution:** High CO2 raises carbon and harms corrosion resistance **Process:** GMAW **Metal:** Austenitic stainless **Gas:** Tri-mix of He, Ar and a little CO2 **Effect:** Flatter bead, better wetting **Caution:** Helium costs more **Process:** GMAW **Metal:** Aluminum **Gas:** 100% Ar **Effect:** Good cleaning action and spray transfer **Caution:** Add helium blends for thick sections **Process:** GMAW **Metal:** Aluminum, thick **Gas:** Ar-He mix **Effect:** Hotter arc, better fusion in thick plate **Caution:** Higher gas cost and flow rates **Process:** GTAW **Metal:** Carbon and low alloy steel **Gas:** 100% Ar **Effect:** Stable arc and good control **Caution:** Use a clean electrode and surface **Process:** GTAW **Metal:** Austenitic stainless **Gas:** 100% Ar **Effect:** Standard choice for clean root and cap **Caution:** Pure argon back purge is needed for the root side **Process:** GTAW **Metal:** Austenitic stainless **Gas:** Ar with a few percent H2 **Effect:** Hotter arc and faster travel **Caution:** Austenitic only, never on ferritic, martensitic or duplex **Process:** GTAW **Metal:** Aluminum and magnesium **Gas:** 100% Ar or Ar-He, AC current **Effect:** Arc cleaning of oxide layer **Caution:** Helium raises arc voltage and heat **Process:** GTAW **Metal:** Titanium **Gas:** High purity Ar with trailing and back shield **Effect:** Prevents oxidation and embrittlement **Caution:** Discoloration of the weld shows contamination **Process:** GTAW **Metal:** Copper **Gas:** Helium or Ar-He **Effect:** Needed for the high thermal conductivity of copper **Caution:** Preheat is usually required **Process:** FCAW-G **Metal:** Carbon steel **Gas:** 100% CO2 or 75-80% Ar, balance CO2 **Effect:** Follow the wire maker's C or M designation **Caution:** Mix and CO2 wires are not interchangeable without approval **Process:** FCAW-S **Metal:** Carbon steel **Gas:** None, self-shielded **Effect:** Works outdoors in wind **Caution:** More fume and slag to clean **Process:** GTAW or PAW **Metal:** Duplex stainless **Gas:** Ar, sometimes with a small nitrogen addition **Effect:** Helps maintain phase balance **Caution:** Follow the WPS, since gas affects ferrite content **Process:** Backing purge **Metal:** Stainless pipe root **Gas:** Argon, or nitrogen for some austenitic work **Effect:** Prevents sugaring and oxide on the root **Caution:** Check oxygen level before welding **Process:** SAW **Metal:** Carbon and low alloy steel **Gas:** None, flux protects the weld **Effect:** High deposition, deep penetration **Caution:** Flux must be stored dry **Notes:** Values are typical industry practice, not requirements. Your WPS and the filler maker's data sheet take precedence. Never add hydrogen to carbon or low alloy steel shielding gas because of hydrogen cracking risk. ## Content **Intro:** Shielding gas drives penetration, spatter, bead shape and, for stainless and aluminum, weld quality. This chart shows the usual gas for each process and metal, plus the cautions that cause real defects. **Sections:** #### How to use this chart **Body:** Search by process such as GTAW, by metal such as aluminum, or by gas such as CO2. Compare the Effect and Caution columns before deciding, because the cheapest gas is not always the lowest-cost weld once rework and cleaning are counted. Export the table to put a controlled selection guide beside your gas cylinder storage or in your welding manual. #### Why gas choice matters **Body:** Argon gives a stable arc and low spatter and supports spray transfer. Carbon dioxide gives deeper penetration but more spatter because it is an active gas. Helium raises arc voltage and heat input, which helps with thick aluminum and copper. Small oxygen or hydrogen additions change wetting and travel speed but must match the base metal. The gas is an essential variable on many WPS forms, so a change usually needs approval. #### Common mistakes **Body:** Gas problems often show up as porosity or discoloration, which are expensive to find late. **Bullets:** - Using a CO2-rich mix on stainless and losing corrosion resistance. - Adding hydrogen to a gas for steel work. - Setting flow too high, which causes turbulence and air entrainment. - Welding in drafts without wind shielding or switching to self-shielded wire. - Skipping the root purge on stainless pipe. **Cta:** If gas and consumable usage needs to flow from work orders into cost and purchasing in your ERP, Netray can outline how teams model that. **Faq:** #### What is the best shielding gas for MIG welding mild steel? **Answer:** A 75-80% argon and balance CO2 mix is the common all-round choice for short circuit transfer, and 90-98% argon works for spray or pulse. Pure CO2 gives more penetration at lower cost but with more spatter. Follow your WPS. #### Can I use CO2 on stainless steel? **Answer:** High CO2 content raises carbon pickup and reduces corrosion resistance, so stainless MIG usually uses 98% argon with 2% CO2 or a tri-mix. For TIG welding, pure argon is standard. #### What gas should I use for aluminum? **Answer:** Pure argon is the default for both MIG and TIG. For thick aluminum, argon-helium mixes give a hotter arc and better fusion. Always weld aluminum with clean material and the correct filler such as ER4043 or ER5356. #### Why do I need a back purge on stainless pipe? **Answer:** Without an inert gas on the inside of the joint, the root oxidizes and forms a rough, sugared surface that loses corrosion resistance. Argon purge, monitored with an oxygen analyzer, keeps the root clean and meets many sanitary and process requirements. ## Search terms shielding gas for MIG welding, welding gas chart, 75/25 argon CO2 vs 90/10, TIG welding gas for stainless, aluminum MIG shielding gas, flux core shielding gas, back purge gas stainless pipe, welding gas selection --- Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json