Fronius MTG320i & MTB320i Parts FAQs
Straight answers on choosing, fitting and looking after the wearing parts of a gas-cooled MIG torch from one maker's range.
How do I make sure I order the right part for my torch?
Start with the torch itself. Note the type designation on the torch body or handle and look it up in the maker's operating instructions or parts list, which show every wearing part for that torch. Then note your wire diameter and wire type, and the shape and thread of the old part.
Parts are tailored to a particular torch and process, so a part that looks the same may not seat or conduct properly. If you are unsure, compare the old part with the parts list, or ask the maker or our team before you order.
Which parts wear out first, and what does a worn part look like?
The contact tip, gas nozzle, insulating parts, nozzle fittings and spatter guard are the usual wearing parts, because they face heat, spatter and the constant rubbing of the wire.
The maker's instructions describe the signs to look for. On a contact tip, the wire entry and exit holes wear oval or the tip is heavily covered in spatter. On a gas nozzle, the edges are burned off, notched or clogged with spatter. Check the wearing parts every time you start work and replace any that are damaged rather than waiting for the weld to suffer.
What are contact tips made from, and does the material matter?
Yes, it can. Plain copper tips have good electrical conductivity and are the usual choice for general work on steel, stainless steel and aluminium. Harder copper alloys, such as copper-chromium-zirconium, resist heat and wear better, so they suit heavy use, long arc-on times and abrasive wires such as some cored or uncoppered wires, though their conductivity is slightly lower.
The right choice depends on your wire material, your welding current and how long you weld at a time, so follow the torch maker's recommendation. Some tips are made specifically for aluminium wire. Whatever the material, the bore must match your wire size.
What do the insulating parts and nozzle fittings do?
They keep the live front end of the torch electrically separate from the gas nozzle, and they seat the nozzle in the right position. Without sound insulation, current can arc to the nozzle, which can damage the parts and upset the weld.
The maker's instructions list insulating parts and nozzle fittings among the parts to check for damage. Look for cracks, charring, heavy spatter or a nozzle that sits loose, and replace the part rather than cleaning a damaged one. If you use anti-spatter compound, apply it sparingly and as its maker directs.