Shielded Metal Arc Welding Electrodes

Shielded Metal Arc Welding Electrodes
Chapter 12

Objectives List the major functions of the SMAW electrode coating.
Describe the composition of an electrode covering. Determine the maximum arc length of an SMAW electrode. List the basic systems for identifying steel electrodes. Explain the electrode selection process. List the AWS electrode classification system.

Objectives List the operating characteristics of the fast fill, fast follow, and fast freeze electrodes. Describe the characteristics of the low hydrogen electrode. Describe the characteristics of the iron powder electrode. List the reasons for keeping mineral coated electrodes dry.

Introduction to Shielded Metal Arc Welding
Acronym of SMAW Also known as stick electrode welding One of most widely used welding processes in field fabrication, maintenance, and repair of metals Two groups besides manufacturers have had major part in research and development American Welding Society American Society for Testing and Materials

Example Welds Welding Current Welding Current Too Low Too High
Excessive piling of weld Overlapping bead with poor penetration Slows up progress Wasted electrodes and production times Welding Current Too High Excessive spatter Undercutting along edges Irregular deposit Wasted electrodes and production times Plan and Elevation Views Hobart Brothers Co. Hobart Brothers Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Example Welds Arc Too Long (Voltage Too High) Welding Speed Too Fast
Bead very irregular with poor penetration Weld metal not properly shielded An inefficient weld Wasted electrodes and production time Welding Speed Too Fast Bead too small Contour irregular Not enough weld metal in cross section Weld not strong enough Wasted electrodes and production time Plan and Elevation Views Hobart Brothers Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hobart Brothers Co.

Proper Current Voltage & Speed
Example Welds Welding Speed Too Slow Excessive piling up of weld metal Overlapped without penetration at edges Too much time consumed Wasted electrodes and production time Proper Current Voltage & Speed Smooth, regular, well-formed bead No undercutting, overlapping, or pilling up Uniform in cross section Excellent weld at minimum material and labor cost Plan and Elevation Views Hobart Brothers Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hobart Brothers Co.

Shielded Metal Arc Welding Electrodes
Definition given in American National Standard and American Welding Society’s “Standard Welding Terms and Definitions”: A composite filler metal electrode consisting of a core of a bare electrode or metal cored electrode with a flux covering sufficient to provide a slag layer and/or alloying elements.

Covered Electrodes Type of covering influences degree of penetration of arc and crater depth Affects extent of recrystallization and annealing of previously deposited layers Improves internal (radiographic) quality of weld Low electrical conductivity of cover permits use of electrodes in narrow grooves Covering also reduces weld spatter

Protective Gaseous Atmosphere and Slag Covering
Coverings provide automatic cleansing and deoxidizing action in molten weld crater Supplies gaseous atmosphere and blanket of molten slag for weld metal Covering excludes harmful oxygen and nitrogen Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Lincoln Electric Co Extend of protection depends on type of covering.

Functions of Slag Acts as scavenger in removing oxides and impurities
Slows down freezing rate of molten metal Slows down cooling rate of solidified weld metal Controls shape and appearance of deposit Affects operating characteristics DCEP, alternating current, etc.

Alteration or Restoration of Base Metal
Covering controls composition of weld metal Maintaining original composition of core wire of electrode Introduction of additional elements Coating may also be balanced to adjust carbon and silicon content of weld deposit

Alteration or Restoration of Base Metal
Addition of large amounts of iron powder to coating of electrode Increases speed of welding Improves weld appearance How? – Iron powder converted to steel in intense heat and contributes metal to weld deposit Low hydrogen electrodes improve welding of steels that tend to be porous and crack under the bead Eliminates these harmful characteristics

Control of Arc Characteristics
Covering makes starting arc easier as begin weld Serves as insulator for core wire of electrode Allows greater variation in arc length Maximum arc length never greater than diameter of bare end of electrode Covering concentrates heat of arc on work thus increased melting rate Flux contains elements that ionize temperature of arc

Composition of Electrode Coverings
Affects arc length, welding voltage, and welding position in which electrode used Composition very important Should have melting point lower than both core wire and base metal Slag must have lower density than solidifying weld metal and able to solidify quickly when electrode used for overhead and vertical welding Coating responsible for differences between electrodes: core wires same type of steel

Materials for Electrode Coverings
Fluxes Deoxidizers Slagging ingredients Alloying ingredients Classified according to their purpose: Gas reducers Binders Arc stabilizers Shielding gas

Materials for Electrode Coverings
Binders: sodium and potassium silicates Some organic gums have limited use Deoxidizers and alloying ingredients Ferro-alloys and pure metals Best arc stabilizers: alkaline earth metals Provide shield of reducing gases Wood flour, wood pulp, refined cellulose, cotton linters, starch, sugar, and other organic materials Fluxes and slagging ingredients Silica, alumina, clay, iron ore, rutile, limestone, magnesite, mica, potassium titanate, and titanium dioxide, and other minerals

Polarity Interchangeability
Composition of covering determines best polarity of electrode used for d.c. applications Some more efficient with electrode negative Some more efficient with electrode positive Both types have advantages for certain applications Coverings developed that operate equally well on either polarity Become familiar with Tables 12-1 through 12-5 Coverings, properties of various types of electrodes

Polarity Interchangeability
This video clip shows the SMAW process with direction of current flow with DCEP polarity.

Identifying Electrodes
System for covered arc welding electrodes requires electrode classification number be imprinted or stamped on covering Within 2-1/2 inches of grip and electrode Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

AWS Classification of Carbon Steel Electrodes
AWS Specifications for Iron and Steel Welding Electrodes Booklet purchased from American Welding Society Classifies many types of electrodes available to weld carbon and alloy steels

Other Agencies American Society of Mechanical Engineers (ASME)
American Bureau of Shipping (Bureau of Ships) U.S. Department of Defense (for Army, Navy, and Air Force) U.S. Coast Guard Canadian Welding Bureau, Division of Canadian Standards Association Municipal, county, and state organizations

Classification System
System of numbers and organized on basis of: Mechanical properties of deposited weld metal Type of covering Recommended welding position of electrode Type of current required for best results Series of 4- or 5-digit numbers prefixed with letter E (electrode for electric welding) Further interpretation in Tables 12-6 and 12-7

SMAW Electrode Classification Designators
Must be used as an electrode

Minimum tensile strength in 1,000 psi increments May be in two or three digits

Welding position all positions horizontal and flat not currently used vertical down

See Table 12-7 for list of the designation and covering type match
SMAW Electrode Classification Designators Type of covering and type of welding current See Table 12-7 for list of the designation and covering type match

Optional, meets military requirements, greater toughness, lower moisture content, and mandatory diffusible hydrogen limits

Designates electrode has improved toughness

Optional supplemental hydrogen designator

Optional absorbed moisture test for low hydrogen electrodes

Electrode Selection One of most important decisions welder faces
Determined by: Nature of deposited weld metal Suitability of weld metal as joining material for pieces being welded Continued use of shielded metal arc welding process due to high quality of electrodes available

Electrode Grouping Operating characteristics Type of covering
Characteristics of deposited metal Size

Electrode Classifications
Many contain same basic core wire Differences determined by materials in covering Many codes group electrodes based on ease of welding – rather than mechanical properties One group is from AWS D1.1 Structural Welding Code – Steel (See Table 12-8) Welder who passes welder qualification test using electrodes in F4 grouping will be qualified for this group and all lesser group numbers

Size of Electrodes As important as selecting right classification of electrode Joint design Fillet weld welded with larger electrode than open groove welds on butt joints Material thickness Larger electrode used as thickness of material increases

Size of Electrodes Thickness of weld layers Welding position
More weld material deposited in flat and horizontal positions than in vertical and overhead Welding position Larger size electrode can be used in flat and horizontal than in vertical and overhead positions Amount of current Higher the current value, the larger the electrode Skill of the welder

Electrode Classes for Multiple-pass Welding
Size varies with types of joints and position Pipe welding and other groove welds on butt joints first pass – 1/8-inch or 5/32-inch electrodes Good fusion at root; avoid excessive melt-through Remaining passes use 5/32-inch or 3/16-inch electrodes in all positions Use 3/16-inch or larger in flat position Flat position welding of groove weld-butt joint with backing bar – 3/16-inch for first pass Remaining passes use 7/32-inch or larger electrode

Electrode Classes for Multiple-pass Welding
Fillet welds in flat position and other deep groove, flat position joints 3/16-inch, 7/32-inch, or 1/4-inch electrodes Extra heavy plates welded with larger electrodes Out-of-position fillet and groove welding 5/32-inch electrodes Sizes of low hydrogen electrodes used for vertical and overhead welding 1/8-inch and 5/32-inch electrodes Flat and horizontal welding 3/16-inch or larger

Conditions to Check Skill of the welder
Code requirements Properties of base metal Position of the joint Type/preparation of joint Heat-treating requirements Environmental job conditions Amount of weld required Expansion and contraction problems Tightness of fitup Available welding current Thickness and shape of base metal Specifications and service conditions Demands of production and cost considerations

Operating Characteristics of Electrodes
Different electrodes require different welding techniques Electrodes may be grouped according to operating characteristics of joints to be welded Fast fill Fast follow Fast freeze

Fast Fill Electrode Includes heavy-coated, iron powder electrodes
Designed for fast, flat position welding High metal deposition; easy slag removal Little undercutting Burns with soft arc and has shallow penetration Little mixing of base metal and weld metal Bead appearance very smooth, flat to slightly convex face, and little spatter EXX24 electrodes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fast Follow (Fill-freeze)
Combined characteristics of both fast-freeze and fast-fill Burns with forceful arc with medium penetration Lower current and lower heat input Reduces problem of excessive melt-through Complete slag coverage Beads formed with distinct, even ripples Good general-purpose electrodes Example: EXX13 for a.c., DCEN, and DCEP welding Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fast Freeze Electrodes
Ability to deposit weld metal that solidifies or freezes rapidly Important when chance of slag or weld metal spilling out of joint (vertical or overhead) Snappy, deep-penetrating arc Little slag and produce flat beads Produce X-ray quality weld deposits Used for pipe and pressure vessel work Widely used for all-position welding EXX10, DCEP, EXX11 a.c., DCEP Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Combination Types Characteristics of both fast-fill and fast-freeze electrodes All-position, iron powder electrode EXX14 Do not have as much fast fill as EXX24 Do not have degree of fast freeze of EXX10 Compromise between above two types

Low Hydrogen Electrodes
Have coverings containing practically no hydrogen Produce welds free from underhead and microcracking Have exceptional ductility Eliminate porosity in sulfur-bearing steels and ensure X-ray quality deposits Reduce preheat requirements

Chief use in welding of hard-to-weld steels and high-tensile alloy steels Examples: EXX18 and EXX28 classifications Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Iron Powder Added to covering of many electrodes
Converted to steel in intense arc heat Contributes addition metal to weld deposit Added to electrode covering in large amounts Increases speed of welding Stabilizes arc Reduces spatter Improves removal of slag Weld appearance very smooth Examples: EXX14, EXX18, EXX24, and EXX28 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Addition of Iron Powder
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Type of Base Metal Nature of material to be welded of prime importance
Satisfactory welds occur when base metal has same physical and chemical qualities as weld metal deposited Simple tests used to determine unknown base Spark test, torch test, chip test, magnetic test, color test, fracture test, and sound test

Temperature Data Section of Table 12-10 in Text table 12-10
Linde Division, Union Carbide Corp. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Nature of Welding Current
Two types of welding current produced by welding machines Alternating current Direct current Influences selection of electrode E6010 and E7015 designed for d.c. E6011, E6013, E7016, E7014, E7018, and E7028 designed for use with a.c. Perform adequately with d.c.

Thickness and Shape of Material to be Welded
General rule Never use an electrode having diameter larger than thickness of material being welded Light gauge sheet metal work 1/32-inch or thinner E6013 electrode designed for this type of work Least penetration of any electrode in E60XX series

Joint Design and Fitup Each joint type has particular requirements for welding Fitup may have large gaps or be to tight E6013 can be used with a.c. or d.c. equipment Bridge gaps very well because of globular transfer of metal through arc stream

Welding Position Type of position has influence on costs
From least to most: flat, horizontal, vertical and overhead Important consideration in choice of electrode Larger diameter of electrode, greater quantity of weld deposited in unit of time Horizontal and flat positions easiest to handle EXX13, EXX24, EXX28 Vertical and overhead positions easiest to handle EXX10 and EXX11

Conditions of Use Type of structure Stress it will encounter in use
Important weld characteristics for determining choice of electrode Tensile strength Ductility Fatigue resistance Check Table 12-3 or variation in weld metal properties

Engineering Specifications
Note carefully Type of electrode is specified in code requirements

Production Efficiency
Principal factor in cost of welding job is speed with which welding can be done Electrode cost small by comparison Compare rates of deposition given in Table 12-4

Job Conditions Study manufacturer’s specifications Important questions
Is material clean, rusty, painted, or greasy? What is type of surface treatment required for finished job? Is completed job to be stress relieved or heat treated? Are welds in prominent location so weld appearance important?

Factors Affecting Selection of Electrodes
Type of joint and position of welding Type of welding current Properties of the base metal Thickness of the base metal Depth of penetration desired

Factors Affecting Selection of Electrodes
Weld appearance desired Whether the work is required to meet code specifications Tensile strength, ductility, and impact strength required of the weld deposit Design and fitup of the joint to be welded Nature of slag removal

Carbon Steel Electrodes
AWS classification numbers for welding low and medium carbon steels E6010, -11, -13, -20 E7014, -15, -16, -18, -24, -28, -48

E6010 Electrode All-position, DCEP (fast-freeze type)
Best adapted of shielded arc types for vertical and overhead welding Used to advantage on galvanized plate Quality of weld metal of high order Forceful arc and light slag Reduces bubbling and prevents porosity Typical applications include shipbuilding bridges, storage tanks, pipe welding, tanks Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Essential Operating Characteristics of the Electrode
Strong and penetrating arc Enables penetration beyond root of groove or fillet welds on a variety of joints Quickly solidifying weld metal Enables deposition of welds without excessive convexity and undercutting

Essential Operating Characteristics of the Electrode
Low quantity of slag with low melting and low density characteristics Does not become entrapped nor interfere with oscillating and weaving techniques Adequate gaseous atmosphere to protect molten metal during welding Electrodes of this type are usable only with DCEN

E6010 Electrode Commonly classified as cellulosic type
Coating contains cellulose During welding, cellulose changed to carbon dioxide and water vapor Forms gaseous envelope that excludes harmful oxygen and nitrogen in air Needs certain amount of moisture present in coating; should not be stored in dry rod ovens

E6010 Electrode Slag-forming materials of covering include titanium dioxide and either magnesium or aluminum silicates Ferromanganese used as deoxidizer (degasifier) Manganese enters slag as oxide Common binder of sodium silicate solution Also slag-forming material Core wire low carbon rimmed steel 0.10–0.15% carbon, 0.4–0.6% manganese, 0.4% sulfur and phosphorus, and max of 0.025% silicon

E6011 Electrode All-position, alternating current and DCEP
Fast-freeze type Weld deposit free from porosity, holes, and pits Slag removed readily Fillet and bead contours flat rather than convex Used in all-position welding Classified as high cellulose potassium type Core wire identical to that used for E6010

E6013 Electrode All-position, alternating current and DCEN or DCEP (fill-freeze type) Permits satisfactory operation with lower open-circuit voltage Arc action quiet and bead surface smooth with fine ripple Suitable for making fillet welds and groove welds with flat or slightly convex appearance Easily ionized materials incorporated in covering Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

E7014 Electrode All-position, alternating current and DCEN or DCEP (fast-fill type) Covering similar to E6012 and E6013, but thicker due to addition of iron powder Suitable for welding mild steel in all positions Weld beads have smooth surface with fine ripples, slag easily removed Fillet welds flat to slightly convex Good for production welding on plate of medium thickness

Result of research during World War II Name stems from fact that coatings free of minerals containing hydrogen Underbead cracking prevented Produce porosity-free welds in high sulfur steels and eliminate hot-shortness in phosphorus-bearing steels Addition of iron powder in coating increases deposition rate SMAW classifications ending in 5, 6, or 8

Core of mild steel or low alloy steel Mineral covering consists of alkaline earth carbonates, fluorides, silicate binders, and ferro-alloys Must not be exposed to humid air Absorb considerable amount of moisture Hydrogen pickup Not truly all-position welding

E7015 Electrodes All-position, DCEP (low hydrogen)
Coating high in calcium compounds and low in hydrogen, carbon, manganese, sulfur, and phosphorus Contains trace of silicon Arc moderately penetrating Slag heavy, friable, and easily removed Deposited metal flat and somewhat convex

E7015 Electrodes Welding in all positions possible with sizes up to 5/32-inch Larger can be used in horizontal and flat positions Recommended for welding of alloy steels, high carbon steels, high sulfur steels, malleable iron, sulfur-bearing steels, steels to be enameled, spring steels, and mild steel side of clad plates Preheating and postheating may be eliminated

E7016 Electrodes All-position, alternating current and DCEP
Low hydrogen Has all characteristics of E7015 type Used with either alternating or direct welding current Core wire and covering similar to E7015 Addition of potassium silicate or other potassium salts Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

E7018 Electrodes All-position, alternating current and DCEP
Low hydrogen, iron powder Coating contains high percentage of iron powder (25–40%) Slag heavy, friable, and easily removed Deposited metal flat; slightly convex in fillet or groove weld Welding done in all positions Electrodes sizes up to 5/32 in.

E7018 Electrodes Larger diameters used for fillet and groove welds in horizontal and flat positions Short arc must be held at all times Strength of deposited weld metal can be improved through addition of certain alloys to coverings Usually require specific mechanical and chemical properties to meet requirements of base metal

E7028 Electrode Horizontal and flat positions, alternating current, and DCEP Low hydrogen, iron powder Coating contains 50% iron powder Thicker and heavier than E7018 Penetration not deep Weld appearance flat to concave with smooth, fine ripple Slag coating heavy and easily removed Fast-fill type of electrode

E7048 Electrode Flat, horizontal, overhead, and vertical down positions, alternating current and DCEP Low hydrogen, iron powder Formulated for vertical down welding techniques Used on cross-country pipelines

E7024 Electrode Horizontal fillet and flat position, alternating current and DCEN or DCEP Iron powder 50%, titania Also referred to as contact electrodes Electrode coating may rest on surface of joint to be welded (drags) Results in effective shielding of weld pool from atmosphere 1/3 of weld metal deposit comes from covering

Contact Welding Advantages
When comparing E7024 electrodes with conventional electrodes Less weld spatter Lower nitrogen content within weld metal Sounder metal with less tendency for defects Welds practically self-cleaning Smoother weld appearance

Contact Welding Advantages
Welds slightly convex in profile Very smooth surface and extremely fine ripple Characterized by smooth, quiet arc, very low spatter, low penetration Can be used at high lineal speed The Lincoln Electric Co. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Alloy Steel Electrodes
Use of high strength alloy steels increased Shielded arc electrode capable of producing weld deposits with tensile strength exceeding 100,000 p.s.i. developed Core wire alloy steel Available in tensile-strength classifications of 80XX, 90XX, 100XX, 110XX, 120XX Medium arc force and penetration Slag heavy, friable, easily removed

Stainless Steel Popular term for chromium and chromium-nickel steels
Tough, strong material Highly resistant to corrosion, high temperatures, oxidation, and scaling Large variety available and electrodes to weld them (both expensive – handle with care) Metallurgically, classified as martensitic, ferritic, precipitation-hardening, duplex, and austenitic

Martensitic Stainless Steel
Air-hardening steel containing chromium Principle alloying element in amounts ranging from 4–12% Normally hard and brittle Requires both preheating and postheating for welding

Ferritic Stainless Steel
Magnetic, straight-chromium steel Contains 14–26% chromium Normally soft and ductile, but brittle when welded Preheating and postheating necessary for successful welding

Precipitation-hardening (PH) Stainless Steel
Ability to develop high strength with reasonably simple heat treatment Promoted by one or more alloying elements Copper, titanium, niobium, and aluminum Do not require preheat SMAW electrodes not available E308 and E309 can be used where high-strength welds not required

Duplex Stainless Steel (DDS)
Characterized by low-carbon, body-centered-cubic ferrite, face-centered-cubic austenite microstructure Resist stress corrosion cracking and pitting Have yield strengths twice that of 300 series Easier to weld than ferrite types More difficult to weld than austenitic types Postweld heat treatment not recommended SMAW electrodes readily available

Austenitic Stainless Steel
Contains both chromium and nickel Nickel content usually ranges from 3.5–22% Chromium content from 16–26% Strong, ductile, resistant to impact Nonmagnetic when annealed but slightly magnetic when cold worked Heat treatment not necessary during welding

Welding Stainless Steel
Selection of proper type electrode for stainless steel welding critical Different welding method required for each type Weld must have tensile strength, ductility and corrosion resistance equal to base metal Problems of color matching and producing smooth bead with minimum amount of grinding

Stainless-steel Electrode Classifications
Different from those used in AWS system for carbon steel electrodes Based on American Iron and Steel Institute (AISI) classifications of metal alloys Table in text First three digits refer to AISI metal classification number Last two digits refer to position of welding and operating characteristics (AWS classification) E309-15

Stainless-steel Electrode Coverings
Three designations Lime type contains up to 8% titanium dioxide Chief mineral ingredients include limestone, fluorspar Titania type contains > 20% titanium dioxide Lime-titania type contains between 8 and 20%

Stainless-steel Electrode Coverings: Lime Type
Designed for DCEP only Welds have convex face and desirable for root passes in which full throat section prevents cracking Used in vertical and overhead positions Slag completely covers weld Provides rapid wetting action Produces welds with minimum amount of spatter Produces flux drives impurities from weld In E3XX-15 classification

Stainless-steel Electrode Coverings: Titania Type
Designed for either alternating current or DCEP Give smooth arc action, fine bead appearance, and very easy slag removal Produce slightly concave weld Require minimum of cleaning, grinding, and polishing time In E3XX-16 classification

Stainless-steel Electrode Coverings: Lime-titania Type
Used with DCEP or DCEN only or with Alternating current, DCEP, or DCEN All-position electrodes Weld straight chromium and chromium-molybdenus stainless steels Tend to eliminate hydrogen Manganese and silicon included to reduce oxidation Arc stability and easily removable slag

Hard-facing Electrodes
Deposition of alloy material on metal part by one of several welding processes to form a protective surface Depending on alloy, surface resists Abrasion: Wear from continuous grinding, rubbing Forces move parallel to surface of component Impact: Result of chipping, upsetting, cracking Action perpendicular to absorbing members Corrosion: Destruction of surface from oxidation, scaling, or atmospheric chemical contamination

Conditions that Classify Electrodes for Metal Arc Welding
Resistance to severe impact Resistance to severe abrasion Resistance to corrosion and abrasion at high temperature Resistance to severe abrasion with moderate impact Resistance to abrasion with moderate-to-heavy impact

Most cases single type of electrode needed Some conditions require two types: severe abrasion encountered with sever impact Class 1 electrode used for buildup metal Cushions impact loads and supports hard deposit Second type used to deposit material that has high abrasion characteristics Resists abrasion

Many different kinds of hard-facing materials General base of iron, nickel, copper or cobalt Alloying elements: carbon, chromium, molybdenum, tungsten, silicon, manganese, nitrogen, vanadium, and titanium Electrodes classified on basis of type of service they perform Divided between ferrous and nonferrous base alloys (See Table 12-15)

Ferrous Base Alloys: Austenitic Steel Electrodes
Two major types Those containing high percentage of manganese Provide metal-to-metal wear resistance, impact and surface protection, replacement of worn areas Widely used to resurface railway trackwork Those containing chromium, nickel, and iron Stainless steels Used for corrosion-resistance overlays and joining or buildup purposes Some good heat-resistant alloys and serve as surface protection against oxidation up to 2,000ºF

Ferrous Base Alloys: Martensitic Steel Electrodes
Carbon major determinant of characteristics Inexpensive and tough Can be built up to form thick, crack-free deposits of high strength and some ductility Moderate abrasion resistance Increases with carbon content and hardness Used for building up surfaces of shafts, rockers, and other machined surfaces

Ferrous Based Alloys: Iron Electrodes
Called irons (high carbon content) Characteristics of cast iron and used for facing heavy cast iron machinery parts Have moderate-to-high alloy content of chromium, molybdenum, or nickel Resists abrasion better than austenitic and martensitic steels Hard facing limited to one or two layer overlays Cracking often results Proper support important

Nonferrous Base Alloys: Cobalt-base Surfacing Metals
Rods and electrodes Usually contain 26–33% chromium, 3–14% tungsten, and 0.7–3.0% carbon Three grades available High resistance to oxidation, corrosion, and heat Often used in manufacture of exhaust valves for internal combustion engines

Nonferrous Base Alloys: Composite Tungsten Carbine Materials
Supplied in form of mild steel tubes filled with crushed and sized granules of cast tungsten carbide (60% carbide, 40% tungsten) Very hard, tough, and abrasion resistant More resistant than any other welded overlay Highest abrasion resistance achieved with oxyacetylene welding Molten metal dissolves some of tungsten carbide to form matrix of high tungsten steel

Nonferrous Base Alloys: Copper-base Surfacing Metals
Rods and Electrodes Used for corrosion resistance as well as wear applications Alloys with aluminum contain 9–15% aluminum and up to 5% iron Hardest of copper-surfacing alloys 380 on Brinell scale Used extensively to minimize metal-to-metal wear

Nonferrous Base Alloys: Nickel-base Surfacing Metals
Rods and electrodes Contain relatively high degree of chromium and less of carbon, boron, silicon, and iron Hardness and abrasions resistance increase with carbon, boron, silicon, and iron Hard and have satisfactory resistance to abrasion, oxidation, corrosion, and heat Hot strength and resistance to high-stress abrasion lower than cobalt-base group

Aluminum Most widely fabricated metal after steel
Wide availability, strength, light weight, good workability, and pleasing appearance More than two dozen major welding processes Gas metal arc and gas tungsten arc used frequently Welded throughout thickness range of inch in foil to 6 inches in plate Electrodes use alloying elements of magnesium (with/without zinc) and silicon (with/without copper) See Table 12-16

E1100 and 4043 Alloys Covered electrodes generally available
E1100 commercially pure aluminum giving weld deposit with minimum tensile strength of 12,000 p.s.i. Alloy contains 95% aluminum and 5% silicon with tensile strength of 30,000 p.s.i.

Aluminum Electrodes When corrosive factors important, electrode selected with composition close to base metal Presence of moisture in coating major cause of porous weld structure Advisable to bake all doubtful electrodes and those from previously opened packages 350–400ºF for hour before welding Store in heated cabinet until used Ductility and cracking (hot-shortness) problem in welding of aluminum

Specialized Electrodes
Large variety of specialized electrodes to meet conditions presented by various metals Nickel and high nickel alloys Copper and copper alloys Magnesium and magnesium alloys Titanium and titanium alloys

High Nickel Electrodes
Developed for welding of gray iron castings, ductile iron, malleable iron, and other iron-base metals Special alloy capable of welding dissimilar metal combinations Number of electrodes that contain 50% or more nickel used in welding of nickel and its alloys

Combinations of Alloys in Electrodes
Nickel-copper alloys Monel®-nickel-copper alloys Age-hardenable Monel®-nickel-copper alloys Age-hardenable Inconel® Inconel®-nickel-chromium-iron alloys High nickel alloy filler metal

Copper Electrodes Contain tin and silicon in addition to copper
Classified with prefix E plus chemical abbreviation of metal they contain ECuAl E = electrode, Cu = Copper, Al = Aluminum Copper-silicon alloys referred to as silicon bronzes Core wire has 3% silicon Weld copper-silicon metal and copper-zinc (brass)

Copper Electrodes Copper-tin alloys known as phosphor bronzes
Contain about 8% tin Weld copper, bronze, brass, and cast iron Used for overlaying steel Require preheat and used with DCEP Copper-nickel Contain 70% copper, 30% nickel Must not be preheated or allowed to overheat Used with DCEP

Copper Electrodes Copper-aluminum of two types
ECuAl used with gas welding Weld aluminum bronzes, manganese bronzes, some nickel alloys, ferrous metals and alloys, dissimilar metals Used with DCEP ECuAl-A2 65 to 90% aluminum, 0.5 to 5.0% iron Produce deposit with higher tensile strength, yield strength, hardness, and lower ductility than other type Used for repairing castings, joining nonferrous metals

Copper Electrodes Nickel-aluminum bronze (ECuNiAl) and Manganese-nickel-aluminum-iron (ECuMuNiAl) alloys Used to weld similar base metals for ship propellers and ship fittings Used with DCEP See Table for list of AWS filler metal specifications for SMAW process

Standard Sizes and Lengths
Standard size refers to diameter of core wire Exclusive of coating Center gripping of electrode is standard 18-inch and 36-inch lengths End gripping of electrode is standard All other lengths See Table for standard sizes and lengths of end-gripping electrodes

Packing Electrodes suitably packed to protect against damage during shipment or storage Bundles of 50 pounds net weight Boxes of 25 or 50 pounds net weight Coils, reels, or spools of 200 pounds or less

Electrode Drying Ovens
Capacities varying from 12 to 1,000 pounds and temperature control to 1,000ºF Electrodes packed in moisture-proof containers Absorb moisture from air Sometimes up to 26 times allowable content Portable Phoenix International Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Portable Holding Oven Used to protect flux or flux cored wire from picking up moisture Also offer good protection after current turned off Welders also protect electrodes by carrying them in small leather carrier Table covers typical storage and conditioning recommendations Phoenix International Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Marking All bundles, boxes, coils, and reels usually contain following information Classification Manufacturer’s name and trade designation Standard size and length Weight instead of length in case of reels and coils Guarantee Manufacturer’s recommendations concerning heat settings, type and preparation of joint, base metal, welding technique, position, and current

Moisture Control Perfectly dry electrode needed when job requires moisture-prone electrodes Moisture leads to increased arch voltage, spatter loss, undercutting, poor slag removal Deposit may suffer from porosity, underbead cracking, and rough appearance All mineral-covered electrodes thirsty Absorb moisture from air Require antimoisture protection

Electrode Ovens Mandatory for storage of:
Low hydrogen and hard-facing electrodes Others made from special alloys Iron powder Stainless steel Aluminum Inconel® Monel® Brass Bronze

Shielded Metal Arc Welding Electrodes

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