Shielded Metal Arc Welding (SMAW)

Effect of Welding Amperage Arc Length and Travel Speed on Covered Electrode Weld Beads (See Exam 1 Figures File, Figure 4.2).

A. Proper amperage, arc length, and travel speed B. Amperage too low C. Amperage too high D. Arc length too short E. Arch length to long F. Travel speed too slow G. Travel speed too fast

List SMAW Capabilities

Can be used to weld most commercial alloys except for titanium (welding of aluminum is possible but rare) Thickness ranges from 1/8in to unlimited thickness (more economical than GWAM or FCAW) can be welded with the same machine. Extremely versatile - relatively insensitive to joint fill up. Portable Can be used in all positions with proper electrode choice. Can be used in drafty conditions.

List SMAW Advantages

Can weld in all positions (depending on type of electrode) Inexpensive equipment Flexible, portable Ability to weld in drafty conditions Not as sensitive to part fit-up variances as many other processes

Define ASME Mild Steel Electrode Classification System

Classified via four main groups: F-1 - High deposition group known as "Fast-Fill" F-2 - Mild penetration group known as "Fill-Freeze" F-3 - Deep penetration group known as "Fast-Freeze" F-4 - Low hydrogen group

Define the labeling system for specification of Carbon Steel Electrodes in SMAW (EXXXX)

E = electrode First two or three digits = ultimate tensile strength (UTS) of weld metal in ksi Second from last digit = position Last digit = type of coating/current

Define the labeling system for specification of Stainless Steel Electrodes in SMAW (E-XXX-XX)

E = electrode Uses AISI number to denote alloy and a suffix for coating type

List SMAW Limitations

Less than 1/8in thickness can be welded but requires great skill. Deposition rate is slow due to relatively slow travel speeds combined with the requirement for frequent stops to change electrodes. Potential for high draft rates. Fume generation rates are high.

SMAW Limitations

Low deposition rates Requires high level of manual welder skill Not ideal for thin sheets Frequent stops and starts increase possibility for weld defects Electrode waste (stubs) Significant welding fumes

Describe SMAW

Most widely used process worldwide. Outgrowth of original carbon arc welding process. Manual process which requires considerable skill. Equipment and consumable costs are low.

What is SMAW electrode coating?

Provides a gas cover to shield the arc and prevent excessive atmospheric contamination of the molten filler metal. Provides scavengers, deoxidizers, and fluxing agents to cleanse the weld and (potentially) prevent excessive grain growth in the weld material. Establishes the electrical characteristic of the electrode. Provides a slag blanket to protect the hot weld metal from the air and enhance the mechanical properties, bead shape, and surface cleanliness of the weld metal. Provides a means of adding alloying elements to weld metal to alter the microstructure and mechanical properties of the weld metal.

What are the two orientations of the electrode in SWAM welding?

Push (electrode is pointed in direction of travel) Drag (electrode is pointed in opposite direction of travel)

Define the ASME Mild Steel Electrode Classification of F-1

• Contain iron powder for highest deposition rates of the four groups • Can only be used in flat and horizontal positions due to dense slag and slow cooling rate • Smooth, ripple-free bead with minimal spatter • Slag is easily removed • Example is E7024

Define the ASME Mild Steel Electrode Classification of F-2

• Excellent for welding thin sheet (less than 3/16 inch) • Often used with DCEN • Contains titania, rutile, or lime-based coating • Example is E6012

Define the ASME Mild Steel Electrode Classification of F-3

• High cellulose coating produces deep penetration and forceful arc • Welds solidify rapidly - good for all positions • Good for dirty, greasy, or painted metal • Light slag • Example is E6010

Define the ASME Mild Steel Electrode Classification of F-4

• Reduces likelihood of hydrogen cracking (medium to high carbon steels) and hot cracking (high phosphorus steels) • Good mechanical properties and x-ray quality welds • Best choice for welding galvanized steel • Example is E7028