© COPYRIGHT 1998 THE ESAB GROUP, INC. LESSON II
Current
Chapter
Table of Contents
Go To Test
Print
Glossary
Search
Chapter
(Faster Download)
Turn Pages
Search
Document
(Slower Download)





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 -
GMAW,GTAW,SAW
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
profile (See Figure 16), penetration, and speed of welding.  In our discussion, we will deal with the more common choices used for the various transfer processes. 2.4.7.1 Short Circuiting Transfer - Straight carbon dioxide (CO2) is often used for short circuiting arc welding because of its low cost.  The deep penetration usually associated with CO2 is minimized because of the low amperage and voltage settings used with this process. Compared to other gas mixes, CO2 will produce a harsher arc and therefore, greater spatter levels.  Usually, this is minimized by maintaining a short arc length and by careful adjustment of the power supply inductance.  The temperatures reached in welding will cause carbon dioxide to decompose into carbon monoxide and oxygen.  To reduce the possibility of porosity caused by entrapped oxygen in the weld metal, it is wise to use electrodes that contain deoxidizing elements, such as silicon and manganese.  If the current is increased above the short circuiting range, the use of carbon dioxide tends to produce a globular transfer. 2.4.7.1.1   Mixing argon in proportions of 50-75% with carbon dioxide will produce a smoother arc and reduce spatter levels.  It will also widen the bead profile, reduce penetration, and encourage "wetting".  Wetting, i.e., a uniform fusion, along with joining edges of the base metal and the weld metal, minimizes the weld imperfection known as undercutting (See Figure 17). FERROUS METALS NON-FERROUS METALS CO2 ARGON + CO2 ARGON + O2 ARGON HELIUM BEAD PROFILE FIGURE 16 FIGURE 17 UNDERCUT WETTING 2.4.7.1.2   The 75% Argon/25 CO2 mixture is often chosen for short circuit welding of thin sections, whereas the 50-50 combination works well on thicker sections. 2.4.7.1.3   It should be noted that shielding gases can affect the metallurgy of the weld metal. As an example, a combination of argon and carbon dioxide may be used for welding stainless steel, but as the carbon dioxide breaks down, excessive carbon may be transferred into the