Rival multiprocess 175 Operating Manual - page 9
EN
Multiprocess 175. Operating manual.
Multiprocess 175. Operating manual.
17
16
Use of DCEN
For a given diameter of tungsten electrode, higher amperage can be
used with straight polarity. Straight polarity is used mainly for welding:
→ Carbon steels
→ Stainless steels
→ Copper alloys
The increased amperage provides:
→ Deeper penetration
→ Increased welding speed
→ A narrower, deeper, weld bead
DCEP
The DCEP (reverse polarity) is different from the DCEN in the following
ways:
→ High heat is produced on the electrode rather than on the base metal
→ The heat melts the tungsten electrode tip
→ The base metal remains relatively cool compared to straight polarity
→ Relatively shallow penetration is obtained
→ An electrode whose diameter is too large will reduce visibility and
increase arc instability
Use of DCEP
→ Intense heat means a larger diameter of electrode must be used with
DCEP
→ Maximum welding amperage should be relatively low (approximately
six times lower than with DCEN)
2.4 Shielding gas selection
Brass
Cobalt-based alloys
Copper nickel (Monel)
Deoxidised copper
Nickel alloys (Inconel)
Mild steel
Magnesium alloys
0.5% Molybdenum
Silicon bronze
Stainless steel
Titanium alloys
With argon, the arc is stable and there is little smoke.
Argon provides a stable, easy-to-control arc.
Argon gives a stable, easy-to-control arc. Also used for welding copper nickel to steel.
Helium is preferred as it helps greatly in counteracting thermal conductivity of copper. A mixture of 75% helium and 25%
argon (Alushield Heavy) produces a stable arc, less heat than an arc produced with helium alone.
Argon produces a very stable arc. Helium is recommended for automatic welding at high speeds
For manual welding, argon is recommended. Successful welding depends on the skill of the welder. Helium is preferred for:
→ high speed automatic welding
→ where deeper penetration than with argon is required
→ small HAZ
Argon recommended with continuous high frequency AC. Produces good arc stability and good cleaning action
Pure argon or helium is recommended. For good welding ductility, welding must be carried out in a draught-free area.
Argon decreases internal tension in base metal and in the weld since there is less penetration with this gas compared to
helium.
Argon is the most commonly used gas for stainless steel. Helium can be used if better penetration is required.
Argon produces a stable arc. Helium is recommended for high speed welding.
DCEN – Narrow bead, deep penetration
DCEP – Wide bead, shallow penetration
Nozzle
Nozzle
Ions
Ions
Electrons
Electrons
3.5 Consumable selection
Filling rod
Filler rod diameter (mm)
Thickness of metal (mm)
2
3
4
4 or 5
5 or 6
0.5–2
2–5
5–8
8–12
12 or more
3.6 Non-consumable tungstens – tungsten electrode selector chart
Copper alloys, Cu-NI alloys and nickel alloys
Thickness range
All
Only thin sections
Only thick sections
Desired results
General purpose
Control penetration
Increase penetration
or travel speed
Welding
current
DCSP
ACHF
DCSP
Electrode type
2% Thoriated
(EW-Th2)
2% Ceriated
(EW-Ce2)
Zirconiated
(EW-Zr)
2% Ceriated
(EW-Ce2)
Shielding gas
75% Argon/
25% Helium
75% Argon/
25% Helium
Argon
75% Argon/
25% Helium
Tungsten performance characteristics
Best stability at medium currents. Good arc starts.
Medium tendency to spit. Medium erosion rate.
Low erosion rate. Wide current range. AC or DC.
No spitting. Consistent arc starts. Good stability.
Use on lower currents only. Spitting on starts.
Rapid erosion rates at higher currents.
Low erosion rate. Wide current range. AC or DC.
No spitting. Consistent arc starts. Good stability.
Mild steels, carbon steels, alloy steels, stainless steels and titanium alloys
Thickness range
All
Only thin sections
Only thick sections
Desired results
General
purpose
Control penetration
Increase penetration
or travel speed
Welding
current
DCSP
ACHF
DCSP
Electrode type
2% Thoriated
(EW-Th2)
2% Ceriated
(EW-Ce2)
2%
Lanthanated
(EWG-La2)
Zirconiated
(EW-Zr)
2% Ceriated
(EW-Ce2)
2%
Lanthanated
(EWG-La2)
Shielding gas
75% Argon/
25% Helium
75% Argon/
25% Helium
75% Argon/
25% Helium
Argon
75% Argon/
25% Helium
Helium
Tungsten performance characteristics
Best stability at medium currents. Good arc starts.
Medium tendency to spit. Medium erosion rate.
Low erosion rate. Wide current range. AC or DC.
No spitting. Consistent arc starts. Good stability.
Lowest erosion rate. Widest current range on DC.
No spitting. Best DC arc starts and stability.
Use on lower current only. Spitting on starts.
Rapid erosion rates at higher currents.
Low erosion rate. Wide current range. No spitting.
Consistent arc starts. Good stability.
Lowest erosion rate. Highest current range.
No spitting. Best DC arc starts and stability.