ELECTROSLAG (ESW) AND ELECTROGAS (EGW) WELDING BASIC INFORMATION AND TUTORIALS

What Is Electroslag Welding? What is Electrogas Welding?

Electroslag welding (ESW) produces fusion with a molten slag that melts filler metal and the surfaces of the base metal. The weld pool is shielded by this molten slag, which moves along the entire cross section of the joint as welding progresses.

The electrically conductive slag is maintained in a molten condition by its resistance to an electric current that flows between the electrode and the base metal. The process is started much like the submerged-arc process by striking an electric arc beneath a layer of granular flux.

When a sufficiently thick layer of hot molten slag is formed, arc action stops. The current then passes from the electrode to the base metal through the conductive slag. At this point, the process ceases to be an arc welding process and becomes the electroslag process.

Heat generated by resistance to flow of current through the molten slag and weld puddle is sufficient to melt the edges at the joint and the tip of the welding electrode. The temperature of the molten metal is in the range of 3500 deg F.

The liquid metal coming from the filler wire and the molten base metal collect in a pool beneath the slag and slowly solidify to form the weld. During welding, since no arc exists, no spattering or intense arc flash occurs.

Because of the large volume of molten slag and weld metal produced in electroslag welding, the process is generally used for welding in the vertical position. The parts to be welded are assembled with a gap 1 to 1 1⁄4 in wide. Edges of the joint need only be cut squarely, by either machine or flame.

Water-cooled copper shoes are attached on each side of the joint to retain the molten metal and slag pool and to act as a mold to cool and shape the weld surfaces. The copper shoes automatically slide upward on the base-metal surfaces as welding progresses.

Preheating of the base metal is usually not necessary in the ordinary sense. Since the major portion of the heat of welding is transferred into the joint base metal, preheating is accomplished without additional effort.

Electrogas welding (EGW) is similar to electroslag welding in that both are automatic processes suitable only for welding in the vertical position. Both utilize vertically traveling, water-cooled shoes to contain and shape the weld surface. The electrogas process differs in that once an arc is established between the electrode and the base metal, it is continuously maintained.

The shielding function is performed by helium, argon, carbon dioxide, or mixtures of these gases continuously fed into the weld area. The flux core of the electrode provides deoxidizing and slagging materials for cleansing the weld metal.

The surfaces to be joined, preheated by the shielding gas, are brought to the proper temperature for complete fusion by contact with the molten slag. The molten slag flows toward the copper shoes and forms a protective coating between the shoes and the faces of the weld. As weld metal is deposited, the copper shoes, forming a weld pocket of uniform depth, are carried continuously upward.

The electrogas process can be used for joining material from 1⁄2 to more than 2 in thick. The process cannot be used on heat-treated material without subsequent heat treatment. AWS and other specifications prohibit the use of EGW for welding quenched-and-tempered steel or for welding dynamically loaded structural members subject to tensile stresses or to reversal of stress.

SHIELDED METAL ARC WELDING (SMAW) OF STEEL BASIC INFORMATION AND TUTORIALS

Shielded metal arc welding (SMAW) produces coalescence, or fusion, by the heat of an electric arc struck between a coated metal electrode and the material being joined, or base metal. The electrode supplies filler metal for making the weld, gas for shielding the molten metal, and flux for refining this metal.

This process is commonly known also as manual, hand, or stick welding. Pressure is not used on the parts to be joined. When an arc is struck between the electrode and the base metal, the intense heat forms a small molten pool on the surface of the base metal.

The arc also decomposes the electrode coating and melts the metal at the tip of the electrode. The electron stream carries this metal in the form of fine globules across the gap and deposits and mixes it into the molten pool on the surface of the base metal. (Since deposition of electrode material does not depend on gravity, arc welding is feasible in various positions, including overhead.)

The decomposed coating of the electrode forms a gas shield around the molten metal that prevents contact with the air and absorption of impurities. In addition, the electrode coating promotes electrical conduction across the arc, helps stabilize the arc, adds flux, slag-forming materials, to the molten pool to refine the metal, and provides materials for controlling the shape of the weld.

In some cases, the coating also adds alloying elements. As the arc moves along, the molten metal left behind solidifies in a homogeneous deposit, or weld. The electric power used with shielded metal arc welding may be direct or alternating current. With direct current, either straight or reverse polarity may be used.

For straight polarity, the base metal is the positive pole and the electrode is the negative pole of the welding arc. For reverse polarity, the base metal is the negative pole and the electrode is the positive\ pole.

Electrical equipment with a welding-current rating of 400 to 500 A is usually used for structural steel fabrication. The power source may be portable, but the need for moving it is minimized by connecting it to the electrode holder with relatively long cables.

The size of electrode (core wire diameter) depends primarily on joint detail and welding position. Electrode sizes of 1⁄8, 5⁄32, 3⁄16, 7⁄32, 1⁄4, and 5⁄16 in are commonly used. Small-size electrodes are 14 in long, and the larger sizes are 18 in long.

Deposition rate of the weld metal depends primarily on welding current. Hence use of the largest electrode and welding current consistent with good practice is advantageous.

About 57 to 68% of the gross weight of the welding electrodes results in weld metal. The remainder is attributed to spatter, coating, and stub-end losses.

Shielded metal arc welding is widely used for manual welding of low-carbon steels, such as A36, and HSLA steels, such as A572 and A588. Though stainless steels, high-alloy steels, and nonferrous metals can be welded with this process, they are more readily welded with the gas metal arc process.

EFFECTS OF WELDING ON STEELS BASIC INFORMATION AND TUTORIALS

Failures in service rarely, if ever, occur in properly made welds of adequate design. If a fracture occurs, it is initiated at a notchlike defect. Notches occur for various reasons.

The toe of a weld may form a natural notch. The weld may contain flaws that act as notches. A welding-arc strike in the base metal may have an embrittling effect, especially if weld metal is not deposited.

A crack started at such notches will propagate along a path determined by local stresses and notch toughness of adjacent material.

Preheating before welding minimizes the risk of brittle failure. Its primary effect initially is to reduce the temperature gradient between the weld and adjoining base metal.

Thus, there is less likelihood of cracking during cooling and there is an opportunity for entrapped hydrogen, a possible source of embrittlement, to escape. A consequent effect of preheating is improved ductility and notch toughness of base and weld metals, and lower transition temperature of weld.

Rapid cooling of a weld can have an adverse effect. One reason that arc strikes that do not deposit weld metal are dangerous is that the heated metal cools very fast. This causes severe embrittlement.

Such arc strikes should be completely removed. The material should be preheated, to prevent local hardening, and weld metal should be deposited to fill the depression.

Welding processes that deposit weld metal low in hydrogen and have suitable moisture control often can eliminate the need for preheat. Such processes include use of low-hydrogen electrodes and inert-arc and submerged-arc welding.

Pronounced segregation in base metal may cause welds to crack under certain fabricating conditions. These include use of high-heat-input electrodes and deposition of large beads at slow speeds, as in automatic welding.

Cracking due to segregation, however, is rare for the degree of segregation normally occurring in hot rolled carbon-steel plates. Welds sometimes are peened to prevent cracking or distortion, although special welding sequences and procedures may be more effective.

Specifications often prohibit peening of the first and last weld passes. Peening of the first pass may crack or punch through the weld.

Peening of the last pass makes inspection for cracks difficult. Peening considerably reduces toughness and impact properties of the weld metal. The adverse effects, however, are eliminated by the covering weld layer (last pass).

(M. E. Shank, Control of Steel Construction to Avoid Brittle Failure, Welding Research Council, New York; R. D. Stout and W. D. Doty, Weldability of Steels, Welding Research Council, New York.)

WELDED-WIRE FABRIC (WWF) BASICS AND TUTORIALS

WELDED-WIRE FABRIC (WWF) BASIC INFORMATION
What Are Welded Wire Fabric?


Welded-wire fabric is an orthogonal grid made with two kinds of cold-drawn wire: plain or deformed. The wires can be spaced in each direction of the grid as desired, but for buildings, usually at 12 in maximum.

Sizes of wires available in each type, with standard and former designations, are shown in Table 9.6.

Welded-wire fabric usually is designated WWF on drawings. Sizes of WWF are designated by spacing followed by wire sizes; for example, WWF 6 12, W12/ W8, which indicates plain wires, size W12, spaced at 6 in, and size W8, spaced at 12 in. WWF 6 12, D-12/D-8 indicated deformed wires of the same nominal size and spacing.

All WWF can be designed for Grade 60 material. Wire and welded-wire fabric are produced to conform with the following ASTM standard specifications:

ASTM A82, Plain Wire

ASTM A496, Deformed Wire

ASTM A185, Plain Wire, WWF

ASTM A497, Deformed Wire, WWF

Epoxy-coated wire and welded wire fabric are covered by the ASTM specification A884/A884M. Applications of epoxy-coated wire and WWF include use as corrosion-protection systems in reinforced concrete structures and reinforcement in reinforced-earth construction, such as mechanically-stabilized embankments.

WELDING AND BRAZING OF ALUMINUM BASICS AND TUTORIALS

WELDING AND BRAZING OF ALUMINUM BASIC INFORMATION
How Welding and Brazing Of Aluminum Works?


Weldability and brazing properties of aluminum alloys depend heavily on their composition and heat treatment. Most of the wrought alloys can be brazed and welded, but sometimes only by special processes.


Finishes for Aluminum and Aluminum Alloys
Types of finish Designation*
Mechanical finishes:
As fabricated M1Y
Buffed M2Y
Directional textured M3Y
Nondirectional textured M4Y
Chemical finishes:
Nonetched cleaned C1Y
Etched C2Y
Brightened C3Y
Chemical conversion coatings C4Y
Coatings:
Anodic
General A1Y
Protective and decorative (less than 0.4 mil thick) A2Y
Architectural Class II (0.4–0.7 mil thick) A3Y
Architectural Class I (0.7 mil or more thick) A4Y
Resinous and other organic coatings R1Y
Vitreous coatings V1Y
Electroplated and other metallic coatings E1Y
Laminated coatings L1Y
*Y represents digits (0, 1, 2, . . . 9) or X (to be specified) that describe the
surface, such as specular, satin, matte, degreased, clear anodizing or type of coating.


The strength of some alloys depends on heat treatment after welding. Alloys heat treated and artificially aged are susceptible to loss of strength at the weld, because weld is essentially cast.

For this reason, high-strength structural alloys are commonly fabricated by riveting or bolting, rather than by welding. Brazing is done by furnace, torch, or dip methods. Successful brazing is done with special fluxes.

Inert-gas shielded-arc welding is usually used for welding aluminum alloys. The inert gas, argon or helium, inhibits oxide formation during welding.

The electrode used may be consumable metal or tungsten. The gas metal arc is generally preferred
for structural welding, because of the higher speeds that can be used.

The gas tungsten arc is preferred for thicknesses less than 1⁄2 in. Butt-welded joints of annealed aluminum alloys and non-heat-treatable alloys have nearly the same strength as the parent metal.

This is not true for strainhardened or heat-tempered alloys. In these conditions, the heat of welding weakens the metal in the vicinity of the weld. The tensile strength of a butt weld of alloy 6061-T6 may be reduced to 24 ksi, about two-thirds that of the parent metal.

Tensile yield strength of such butt welds may be only 15 to 20 ksi, depending on metal thickness and type of filler wire used in welding.

Fillet welds similarly weaken heat-treated alloys. The shear strength of alloy 6061-T6 decreases from about 27 ksi to 17 ksi or less for a fillet weld.

Welds should be made to meet the requirements of the American Welding Society, ‘‘Structural Welding Code—Aluminum,’’ AWS D1.2.

BOLTS AND WELDS : STRUCTURAL FASTENERS BASIC AND TUTORIALS

STRUCTURAL FASTENERS BASIC: BOLTS AND WELDS
What Are Structural Fasteners?


Steel sections can be fastened together by rivets, bolts, and welds. While rivets were used quite extensively in the past, their use in modern steel construction has become almost obsolete. Bolts have essentially replaced rivets as the primary means to connect nonwelded structural components.

Bolts
Four basic types of bolts are commonly in use. They are designated by ASTM as A307, A325, A490, and A449. A307 bolts are called unfinished or ordinary bolts. They are made from low carbon steel.

Two grades (A and B) are available. They are available in diameters from 1/4 in. to 4 in. in 1/8 in. increments. They are used primarily for low-stress connections and for secondary members. A325 and A490 bolts are called high-strength bolts. A325 bolts are made from a heat treated medium carbon steel.

They are available in three types: Type1—bolts made of medium carbon steel; Type 2—bolts made of low carbon martensite steel; and Type 3—bolts having atmospheric corrosion resistance and weathering characteristics comparable to A242 and A588 steel. A490 bolts are made from quenched and tempered alloy steel and thus have a higher strength than A325 bolts.

Like A325 bolts, three types (Types 1 to 3) are available. Both A325 and A490 bolts are available in diameters from 1/2 in. to 1-1/2 in. in 1/8 in. increments. They are used for general construction purposes.

A449 bolts are made from quenched and tempered steel. They are available in diameters from 1/4 in. to 3 in. A449 bolts are used when diameters over 1-1/2 in. are needed. They are also used for anchor bolts and threaded rod.

High-strength bolts can be tightened to two conditions of tightness: snug-tight and fully tight. Snug-tight conditions can be attained by a few impacts of an impact wrench, or the full effort of a worker using an ordinary spud wrench.

ARC WELDING TYPICAL PROCESSES BASICS AND TUTORIALS

TYPES OF ARC WELDING BASIC INFORMATION
What Are the Types of Arc Welding?


Shielded metal arc welding (SMAW): 
Shielded metal arc welding, which is also known as stick welding, is the most widely used process. The arc is struck between the metal to be welded and a flux coated consumable electrode.

The fluxes are mostly made from mineral components and cover the hot weld deposit and protect it from the environment. The solidified glassy product, slag should be removed by chipping or with a wire brush.

Gas metal arc welding (GMAW):
This process is also referred to as metal inert-gas (MIG) welding uses an uncoated continuous wire. The weld area is shielded from contamination by the gas that is fed through the welding torch.

The mode of metal transfer (spray, globular, short-circuiting, pulsed-arc) is varied by adjusting the amperage and the shielding gases used depending on the welding position and the type of joint.

Flux-cored arc welding (FCAW):
The shielding gases and slag are provided by the decomposing flux that is contained within the electrode. Auxiliary shielding is also used in certain instances where deeper penetration is needed.

Gas tungsten arc welding (GTAW): 
Also known as tungsten inert-gas (TIG), the process uses a non-consumable electrode. The shielding gas is again fed through the welding torch.

Welding may be accomplished without the addition of filler metal, which is advantageous especially for thin walled parts.

WELDING RODS QUESTIONS AND ANSWERS

TUTORIALS ON WELDING RODS
Welding Rod Info


1. The E7018 welding rods I've been buying are now marked E7018 H4R. What does the H4R mean? Are these rods different than the E7018 rods I've used before?

H4R is an optional supplementary designator, as defined in AWS A5.1-91 (Specification for shielded metal arc welding electrodes). Basically, the number after the "H" tells you the hydrogen level and the "R" means it's moisture resistant.

"H4" identifies electrodes meeting the requirements of 4ml average diffusible hydrogen content in 100g of deposited weld metal when tested in the "as-received" condition.

"R" identifies electrodes passing the absorbed moisture test after exposure to an environment of 80ºF(26.7ºC) and 80% relative humidity for a period of not less than 9 hours.

The H4R suffix is basically just additional information printed on the rod, and does not necessarily mean a change in an electrode previously marked E7018.

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2. Why is hydrogen a concern in welding?

Hydrogen contributes to delayed weld and/or heat affected zone cracking. Hydrogen combined with high residual stresses and crack-sensitive steel may result in cracking hours or days after the welding has been completed.

High strength steels, thick sections, and heavily restrained parts are more susceptible to hydrogen cracking. On these materials, we recommend using a low hydrogen process and consumable, and following proper preheat, interpass, and postheat procedures. Also, it is important to keep the weld joint free of oil, rust, paint, and moisture as they are sources of hydrogen.

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3. What is the maximum plate thickness which can be welded with Innershield® NR®-211-MP (E71T-11) wire?

NR®-211-MP is restricted to welding these maximum plate thicknesses:

Wire Diameter Maximum Plate Thickness
.030"(0.8mm) 5/16"(7.9mm)
.035"(0.9mm) 5/16"(7.9mm)
.045"(1.1mm) 5/16"(7.9mm)
.068"(1.7mm) 1/2"(12.7mm)
5/64"(2.0mm) 1/2"(12.7mm)
3/32"(2.4mm) 1/2"(12.7mm)
For thicker steels, look to Innershield® NR-212. It has similar welding characteristics to NR®-211-MP but is designed for use on materials up to 3/4" (19.1mm) thick.

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4. What electrode can I use to join mild steel to stainless steel?

Electrode selection is determined from the base metal chemistries and the percent weld admixture. The electrode should produce a weld deposit with a small amount of ferrite (3-5 FN) needed to prevent cracking. When the chemistries are not known, our Blue Max® 2100 electrode, which produces a high ferrite number, is commonly used.

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WELDING RODS, WELDING ELECTRODES BASIC INFO AND TUTORIALS

INFORMATION ABOUT WELDING RODS AND WELDING ELECTRODES
Welding Rods/ Electrodes Tutorials


A BASIC GUIDE OF ARC WELDING ELECTRODES
There are many different types of electrodes used in the shielded metal arc welding, (SMAW) process. The intent of this guide is to help with the identification and selection of these electrodes.
ELECTRODE IDENTIFICATION

Arc welding electrodes are identified using the A.W.S, (American Welding Society) numbering system and are made in sizes from 1/16 to 5/16 . An example would be a welding rod identified as an 1/8" E6011 electrode.
The electrode is 1/8" in diameter

The "E" stands for arc welding electrode.

Next will be either a 4 or 5 digit number stamped on the electrode. The first two numbers of a 4 digit number and the first 3 digits of a 5 digit number indicate the minimum tensile strength (in thousands of pounds per square inch) of the weld that the rod will produce, stress relieved. Examples would be as follows:

E60xx would have a tensile strength of 60,000 psi E110XX would be 110,000 psi

The next to last digit indicates the position the electrode can be use in. READ MORE...

A QUICK REFERENCE FOR WELDING

All positions
Deep penetration
DC reverse polarity
Rod is mild steel
Application – use medium arc, whipping or weaving on vertical and overhead to control bead sag.


Diameter

Flat amps

Vertical amps

Overhead amps

3/32

50 – 90

50 – 90

50 – 90

1/8

90 – 140

90 – 130

90 – 130

5/32

120 – 180

130 – 150

130 – 160

3/16

150 - 230

140 - 270

140 - 180 READ MORE...

GAS WELDING RODS

Gas Welding Rods come in different forms such as, Aluminum, Bronze Alloy, Carbon Steel, Copper Alloy, Hard Facing and Maintenance Alloy. Manufacturers include ESAB, Harris Welco and Radnor. You'll find all of your gas welding rod needs with Airgas.Aluminum gas welding rod comes in two varieties, bare and flux-cored. Bare is recommended for brazing thin sheets, extruded shapes and especially corner joints. Flux-cored has non-corrosive, non-hygroscopic flux inside a tubular rod; no separate flux required.

Silicon Bronze is a copper based filler metal primarily used for TIG and oxyacetylene welding of copper, copper-silicon and copper-zinc base metals to themselves and to steel. Silicon bronze can be used for on plain or galvanized steel sheet metal. It can also be used for surfacing areas subjected to corrosion. READ MORE...

WHAT ARE WELDING RODS?

There are a lot of different welding electrodes and wires out there. In the field, welding electrodes are usually referred to as "welding rods" so I will use that term here.

"Stick Welding" is also the term of choice in the field for SMAW, the acronym for Shielded Metal Arc Welding.

Stick welding used to be done with a bare welding rod. It was very difficult, and could only be used in the flat position. If you've ever stuck a rod with flux on it, you can only imagine how many times they stuck bare rods! If the rod gets too close to the base metal it will decrease the voltage causing the arc to go out. READ MORE...