Chapter 11 SMAW Electrodes GoodheartWillcox Publisher Learning Objectives

Chapter 11 SMAW: Electrodes Goodheart-Willcox Publisher

Learning Objectives • Identify carbon and low alloy SMAW electrodes. • List six purposes of an electrode covering. • Interpret the AWS electrode identification system. • Determine the trial amperage of a welding machine using the rule-of-thumb method. • Select an electrode to meet the requirements of a weld. • Identify two means of storing electrodes. Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Introduction • SMAW electrode properties – Solid, round metal wires – Low-carbon steel – Covered (coated) • Melting electrode provides filler material • Electrode selection depends on several factors Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

AWS Electrode Specifications Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Electrode Coverings • Also called flux coverings • Purposes – Create shield around arc and weld – Create flux to clean impurities – Create hard slag covering to protect weld while cooling – Improve mechanical and chemical properties of weld – Provide filler metal – Determine current type and polarity in electrode Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Effects of Certain Flux Coverings • Metallic salts – Make weld stronger, more corrosion resistant, or more ductile • Iron powder – Electrode deposits more filler metal into weld in given length of time • Low hydrogen electrodes – Deposit minimum amount of hydrogen into weld – Help prevent weakened welds Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Electrode Sizes • Lengths – 9″ (229 mm) – 12″ (305 mm) – 14″ (356 mm) – 18″ (457 mm) • Diameters – 1/16″ (1. 6 mm) – 5/64″ (2. 0 mm) – 3/32″ (2. 4 mm) • Diameters (cont. ) – 1/8″ (3. 2 mm) – 5/32″ (4. 0 mm) – 3/16″ (4. 8 mm) – 7/32″ (5. 6 mm) – 1/4″ (6. 4 mm) – 5/16″ (7. 9 mm) – 3/8″ (9. 5 mm) Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

AWS Electrode Identification System for SMAW Electrodes Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Recommended Polarity • Last two numerals of electrode designation indicate recommended electrical polarity Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

AWS Electrode Suffixes • Suffix indicates that alloys have been added to electrode Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Low Hydrogen Electron Covering Compositions Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Electrode Amperage Requirements • Electrode diameter determines amperage required – Larger diameter needs higher amperage – Manufacturer’s guide provides guidelines • Trial amperage – Rule-of-thumb method Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Rule-of-Thumb Method Steps 1. Determine base amperage for the electrode 2. Determine difference between 1/8″ (3. 2 mm) electrode and electrode to be used 3. Convert the fractional difference from step 2 to equivalent fraction with 32 in denominator 4. Multiply the number of 32 nds by 30 A Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Rule-of-Thumb Method Steps (Cont. ) 5. Calculate the trial amperage – If the electrode diameter is larger than 1/8″, add the answer from step 4 to the base amperage in step 1 – If the electrode diameter is smaller than 1/8″, subtract the answer from step 4 to the base amperage in step 1 Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Welding Procedure Specification (WPS) • Used for commercial jobs – Outlines how weld is to be made – Lists diameter and type of AWS electrode – Specifies type of current and current setting or range • Not needed for most fabrication, repair, and craft welding – Welder or shop owner selects electrode Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Factors for Selecting Electrodes • • • Type of metal Metal thickness Groove design Joint alignment Available welding current Welder skill • • • Welding position Deposition rate Depth of penetration Weld bead finish Additional metal properties Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Type of Metal • Determine tensile strength of base metal • Tensile strength of electrode should be as strong as that of base metal Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Metal Thickness • Consider number of passes needed for metal thickness – Weld passes no more than 1/4″ (6. 4 mm) thick – Wider weld beads needed for thicker metal • Electrodes that do not penetrate deeply work well with thin metal – E 6012 – E 6013 Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Groove Design • Wide V-groove joint – Small-diameter electrode for root pass – Larger electrodes for filler and cover passes • Narrow bevel-, V-, J-, and U-groove joints – Smaller-diameter electrodes for root pass and next few passes Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Joint Alignment • Poorly designed or assembled joints may have large openings • Use electrodes designed to span large root openings – E 6012 – E 6013 – E 7014 Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Welder Skill • Highly skilled welders – May use large-diameter electrode and high amperage – Achieve proper penetration • Less-skilled welders – Selectrode that allows proper penetration with their level of skill Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Welding Position • Flat – All electrodes • Overhead – EXX 1 X – EXX 4 X Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Deposition Rate • Amount of filler deposited per unit time • Measured in pounds or kilograms per hour • Achieving high deposition rate – Larger electrode diameter – Higher amperage – DCEP Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Depth of Penetration • Good penetration on thick metal – E 6012 – E 6013 • Deeper penetration – E 6010 – E 6011 Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Weld Bead Finish • When good appearance • When appearance is is needed not as important – E 6013 – E 7024 – E 6010 Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Additional Metal Properties • Alloying elements – Improve strength – Provide corrosion resistance – Add other desirable characteristics • Low hydrogen electrode coatings – Low in moisture – Low in hydrogen Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Care of Electrodes • Keep in shipping containers until used • Keep away from moisture – Moisture contains hydrogen (H 2) – Hydrogen weakens the weld • Do not bend electrodes Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Care of Low Hydrogen Electrodes • Store in electrode drying oven • Use within specified time after removing from oven Goodheart-Willcox Publisher Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.

Electrode Dispenser • Provides temporary storage • Protects electrodes while out of oven Copyright Goodheart-Willcox Co. , Inc. May not be posted to a publicly accessible website.