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Lesson 1
The Basics of Arc Welding
Lesson 2
Common Electric
Arc Welding Processes
Lesson 3
Covered Electrodes for Welding
Mild Steels
Lesson 4
Covered Electrodes for Welding Low Alloy Steels
Lesson 5
Welding Filler Metals for Stainless Steels
Lesson 6
Carbon & Low Alloy
Steel Filler Metals -
Lesson 7
Flux Cored Arc Electrodes Carbon Low Alloy Steels
Lesson 8
Hardsurfacing Electrodes
Lesson 9
Estimating & Comparing Weld Metal Costs
Lesson 10
Reliability of Welding Filler Metals
© COPYRIGHT 1998 THE ESAB GROUP, INC. LESSON II weld metal.  Corrosion resistance in stainless steel is reduced as the carbon content increases.  To counteract this possibility, a less reactive mixture of 90% helium - 7-1/2% argon - 2-1/2% CO2 is sometimes chosen.  This combination, known as a trimix, provides good arc stability and wetting. Spray Arc Transfer - Pure argon produces a deep constricted penetration at the center of the bead with much shallower penetration at the edges (Figure 16).  Argon performs well on nonferrous metals, but when used on ferrous metals, the transfer is somewhat erratic with the tendency for the weld metal to move away from the center line.  To make argon suit- able for spray transfer on ferrous metals, small additions of 1 to 5% oxygen have proven to provide remarkable improvements.  The arc stabilizes, becomes less spattery, and the weld metal wets out nicely.  If the percentage of argon falls below 80%, it is impossible to achieve true spray transfer.   Pure helium or combinations of helium and argon are used for welding nonferrous metals.  The bead profile will broaden as the concentration of helium increases. Pulse Spray Transfer - The selection of shielding gas must be adequate enough to support a spray transfer.  Material type, thickness, and welding position are essential variables in selecting a particular shielding gas.  The following is a list of recommended gases: Carbon Steel Argon/CO2/O2/He (He less than 50%) Alloy Steel Argon/CO2/O2/He (He less than 50%) Stainless Argon/O2/CO2 (CO2 max. 2%) Copper, Nickel, & Cu-Ni Alloys Argon/Helium Aluminum Argon/Helium 2.4.8 Electrodes - The solid electrodes used in GMAW are of high purity when they come from the mill.  Their chemistry must be closely controlled and some types purposely contain high levels of deoxidizers for use with CO2 shielding. The electrode manufacturer draws down the electrode to a finished diameter that, with GMAW, is usually quite small.  Diameters from .030" thru 1/16" are common. Most steel GMAW electrodes are copper plated as a means of protecting the surface.  The copper inhibits rusting, provides smooth feeding, and helps electrical conductivity. Information on types and classifications will be covered in a future lesson.