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Section 4
Shielding Gas Selection for Steels
The choice of gas depends on two factors, weld penetration and appearance. Pure argon provides the best looking welds,
but has the least weld penetration. To increase penetration C02 is added to the mix. C02 percentages range from 10% to
25% depending on the desired level of penetration. Stainless steel will typically use a mix of 82% Argon and 18% C02.
Other mixes are used to achieve different results.
Aluminum
In general, all plate alloys of the 1100, 3000, and 5000 series are considered excellent for stud welding; alloys of the 4000
and 6000 series are considered fair; and the 2000 and 7000 series are considered poor. Most aluminum weld studs are
manufactured from 5000 series aluminum.
Base Metal Preparation
Base metal to which studs are to be welded should be free of anodic coatings, moisture or other foreign material to assure
obtaining sound welds. These areas may be cleaned by etching, brushing with a stainless steel bristle brush, scraping or
grinding.
Prior to welding, surface areas to which studs will be welded should be clean and free of foreign matter including the
following:
(1) Paint
(2) Moisture
(3) Heavy oxide film
(4) Oil, grease, indelible markings, etc.
(5) Anodic coatings
Cleaning may be accomplished by mechanical means (milling, stainless steel wire brushing), chemical methods, or both. Oil,
grease, and similar contaminants should be removed with a suitable, safe solvent. (The use of chlorinated hydrocarbons
should be avoided.) A heavy oxide film may require removal by chemical means. Welding should take place within eight
hours after cleaning.
Electrical Arrangements.
Arc stud welding of aluminum should be performed with direct current, electrode positive (DCEP). This is the opposite of
standard stud welding. For aluminum, the weld tool should be connected to the RED output terminal and the ground should
be connected to the BLACK output terminal.
Shielding Gas for Aluminum
Shielding gas for arc stud welding and drawn-arc capacitor discharge stud welding is generally argon of at least 99.95 percent
purity. Helium may be used with large studs to take advantage of the higher arc energy (required for magnesium). The gas
should be directed to the weld area with an adaptor foot, and permitted to flow only while the weld tool is held against the
work in the welding position. Generally, 10ft
flow rates recommended by the stud manufacturer should be used.
Other Materials
On a moderate scale, stud welding is being done commercially on various brass, bronze, nickel-copper, and nickel- chromium-
iron alloys. These applications are usually very special ones requiring careful evaluation to determine suitability of design.
Nickel, nickel-copper, and nickel-chromium-iron alloy stud welds tend to contain porosity and crevices. The mechanical
strengths, however, are usually high enough to meet most requirements. The weld itself should not be exposed to corrosive
media. This section does not apply to QuikLinx clips.
Special Welding
3
/hr (9l/min) is a good starting point for gas flow; however, the shielding gas
Techniques
24
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