Tweco XTTM-301 - Manual (Page 53)

Manual 0-4768 4-15 OPERATION
4.08 Gas Selection
A. Plasma Gases
1. Air Plasma
• Most often used on ferrous or carbon base materials for good quality at faster cutting speeds.
• Air plasma is normally used with air secondary.
• Only clean, dry air is recommended for use as plasma gas. Any oil or moisture in the air supply will substantially
reduce torch parts life.
• Provides satisfactory results on nonferrous materials.
2. Argon/Hydrogen (H35) Plasma
• Recommended for use on 3/4 in (19 mm) and thicker stainless steel. Recommended for 1/2 inch (12 mm) and
thicker nonferrous materials. Ar/H2 is not normally used for thinner nonferrous materials because less expen-
sive gases can achieve similar cut quality.
• Poor cut quality on ferrous materials.
• Provides faster cutting speeds and high cut quality on thicker materials to offset the higher cost.
• A 65% argon / 35% hydrogen mixture should be used.
3. Oxygen (O
2
) Plasma
• Oxygen is recommended for cutting ferrous materials.
• Provides faster cutting speeds.
• Provides very smooth finishes and minimizes nitride build-up on cut surface (nitride build-up can cause difficul-
ties in producing high quality welds if not removed).
4. Nitrogen (N2) Plasma
• Provides better cut quality on nonferrous materials such as stainless steel and aluminum.
• Can be used in place of air plasma with air secondary or carbon dioxide (CO
2
).
• Provides much better parts life than air.
• A good clean welding grade nitrogen should be used.
B. Secondary ("Shield') Gases
1. Compressed Air Secondary
• Air secondary is normally used when operating with air plasma.
• Improves cut quality on some ferrous materials.
• Inexpensive - reduces operating costs.
2. Nitrogen (N2) Secondary
• Nitrogen secondary is used with Ar/H2 (H35) plasma.
• Provides smooth finishes on nonferrous materials.
• May reduce smoke when used with Ar/H2 plasma.