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Welding Rods | Manual Metal Arc Welding [MMA]

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Manual Metal ArcWelding (MMA)

Tungsten Inert GasWelding (TIG)

Oxy-AcetyleneWelding

Welding Rods

Welding RodsWhilst there are many types of welding rods it is firstnecessary to understand the welding processes involved sothat these can be related to the welding materials which fallunder this heading.

There are 3 common processes for the deposition of weldingrods:-

1. Manual Metal Arc Welding[MMA]

2. Tungsten Inert Gas Welding [TIG]

3. Oxy-Acetylen Welding

Manual Metal Arc Welding [MMA]In MMA the welding rods are more commonly calledelectrodes. An electric arc is formed when an electric arcpasses between two electrodes separated by a short distancefrom each other. In MMA welding the electrodes is connectedto the positive + pole and the material to be welded [nowcalled the base plate] to the negative [please note that thispolarity may be changed based on the welding electrodemanufacturers recommendations. This will be dealt withadditional technical information, on this site, in the future].Thearc is started by momentarily touching electrode onto thebase plate and then withdrawing it to about 3mm from theplate. When the electrode touches the plate a current flows,and as it is withdrawn the current continues to flow in theform of a spark across the gap first formed. This causes theair gap to become ionized, or made conductive, and as aresult the current is able to flow across the gap, in the formof an arc. The electrode must always be touched down, orscratched on the plate before the arc can be started, sincethe smallest air gap will not conduct a current unless it is firstionized.

If a bare wire is used as an electrode it is found that the arcis difficult to control and the arc stream will wander over themolten pool formed in the base material. The metal globulesprojected across the arc [ionized] gap are exposed to theatmosphere and the absorption of oxygen and nitrogen takesplace, even when a short arc is held.

The arc can be rendered easy to control and the absorption ofatmospheric gases reduced to a minimum by shielding thearc. This can be done by extruding a coating onto theelectrode and as a result gases, such as hydrogen and carbondioxide are released from the coating as it burns down inconjunction with the melt rate of the rod[core wire]. Thisforms a covering around the arc and molten pool, thusexcluding the detrimental effects from the atmosphere. Underthe heat of the arc chemical compounds in the electrodecovering also react to form a slag which in its liquid form islighter than the molten metal. This rises to the surface, coolsand solidifies, forming a protective cover of the welded joint,as it solidifies and also slow down the cooling rate. Some



slags are self releasing whilst others my need to be lightlychipped with a welders chipping hammer.

The electrode coatingnormally melts at aslightly slower ratethan the core wire sothat it extends a littlebeyond the core,concentrating anddirecting the arcstream, making thearc stable and easierto control.

[drawing courtesy of TWI]

When an arc is struck between the metal and the plate, theheat generated forms a molten pool in the plate and at thesame time the electrode begins to melt, this metal beingtransferred from the metal to the plate.

Which Electrode?Welding electrodes are selected based on their compatibilitywith the base materials and the more common ones are listedbelow:-

A] Mild & Low Alloy SteelsB] Stainless SteelsC] Cast IronD] MetalworkingE] Wear facing [Hardfacing]F] AluminiumG] BronzesH] Copper

A] Mild and Low Alloys Steels

AWS A5.1: E6013EN.ISO 2560:E 42 0 RR 12**

Normally a general purpose mild steel electrode for joints inbase materials of similar composition, having Tensile strengthsof around 450 520 N/mm2.

These can be for down hand [flat] welding or for all positionalwelding of mild steel, in the vertical and horizontal positions.

AWS A5.1: E7018-1EN.ISO 2560: E 46 4B 32 H5

These are known as Low Hydrogen, or Hydrogen controlledelectrodes and are normally used in steel construction, wherecomponents are subject to higher degrees of stress and assuch would have a Tensile strength in the range of 530 580 N/mm2

AWS A5.1: E7024EN.ISO 2560: E 42 0 RR 53

Classed as a High recovery electrode based on the fact thatthis type of mild Steel electrode is highly efficient in that byincorporating metal powder in the electrode coating it will



deposit weld metal equivalent to up to 160% of the electrodecore wire weight. This electrode is very popular in fabricationshops for rapid welding of sheet steel.

** Electrode Classification [British]Abridged classification to cover carbon and carbonmanganese steel electrodes for manual arc welding.BS639 [1986]

This classification is for deposited weld metal having a tensilestrength not greater than 650N/mm2. The classification isnoted by a code consisting of 2 parts: [a] a general code,followed by [b] an additional code in parentheses, for exampleE 43 2 2 RR [21]

[a] General Code

[1] The letter E indicating a covered electrode formanual arc welding[2] Two digits indicating the strength [Tensile, yield andelongation properties] Of the base material.[3] One digit for a minimum average impact value of 28Jules.[4] One indicating the temperature for a minimumaverage value of 47 Jules.[5] Either one, or two letters indicating the type ofelectrode coating e.g.B basic; BB basic, high efficiency; C cellulosic; R rutile etc

[b] Additional Code

A digit recommended welding positions for the electrode.

1 all positions2 all positions except vertical down3 flat an for fillet welds4 flat5 flat, vertical down and for fillet welds9 any other positions not classified above.

Also a letter H, indicating a hydrogen controlled electrode.

B] Stainless Steels

AWS A5.4 E308L-17E 19 9 LR 32

For the welding of stainless steels such as Types 304L, 321 &347. This alloy has maximum carbon content of 0.03% whichincreases the resistance to intergranular corrosion.

AWS A 5.4 E316L-17E 19 12 3 LR 12

Used primarily for welding molybdenum bearing low carbonaustenitic alloys. Also available as ER316H for elevatedtemperatures.

AWS A5.4 E307-16 [mod]E 18.8.Mn LR53



For the joining and overlaying of alloy steels and can also beused as a buffer layer prior to the depositing of a wearresistant [hard facing] coating.

AWS A 5.4 E309-17E 23.12 LR32

For the welding of corrosion and heat resistant stainlesssteels. The low carbon content [0.03% maximum] increasesresistance to inter granular corrosion. 309L superior to 309for the cladding of carbon or low alloy steels.

AWS A 5.4 E310-16E 25.20. LR26

For joining heat resisting stainless steels up to an operatingtemperature of 1200C. High oxidation resistance and strengthat elevated temperatures.

C] Cast Iron

AWS E Ni-BG11DIN 8573 E Ni-BG11

High nickel content electrode for the welding of grey,malleable and cast irons. Suitable for contaminated cast ironcomponents, such as cylinder blocks, pump housings andelectric motor casings.

AWS E Ni Fe -1-BG11DIN 8573 E Ni Fe C1

A nickel iron electrode for repairs to nodular, spheroidalgraphite and malleable cast iron components. Suitable forjoining cast iron to steel and where an oil tight joint isrequired.

D] Metal Working

CUTTING ELECRODES

Cutting electrodes have a special flux coating which producesa forceful non metal depositing arc. This will cut, or pierce, allferrous and non ferrous materials.

GOUGING ELECTRODES

Use for grooving, gouging or otherwise preparing metal priorto welding. This electrode is particularly suitable for sealingthe oil contaminated surface of cast iron components beforedepositing either a Nickel, or Nickel Iron welding material.

E] Wear facing [Hard facing]

Use for protection from components subject to wear whilst inservice, from abrasion, impact and other medium. The alloysfall into three common groups.

E1] High carbonE2] Complex carbidesE3] Tungsten carbides



E1] For wear facing components subject to both impact andabrasion with a hardness of up to 57RC being achieved after 3passes. Applications include coatings on steels, cast steels andmanganese steels, such as crusher rings, earth moving plantand screw conveyors.

E2] Depending on the complexity and percentages of carbidessuch as chromium and tungsten in these alloys a hardness ofup to 70RC can be achieved. Whilst some of these alloys canbe used for resistance to impact and abrasion the upperhardness values are for resistance to abrasion with minorimpact. Applications include: wear resistant coatings oncrusher hammers, bucket lips, chutes, liners and screwconveyors

E3] Consisting of up to 70% Tungsten carbides in a complexcarbide matrix, with an approximate hardness of 70RC. This isthe hardest of the more popular wear resisting coatings and isused in applications where extreme abrasion is experienced.Applications include mixer paddles, sinter fan, mineral drillingtools, ceramic and glass process plant.

F] Aluminium

DIN 1732 EL-Al Si 12AWS A 5.3 E 4047

Whilst there are a number of alloys suitable for joiningaluminium and most of its weldable alloys the most commonand successful is the aluminium, 12% silicon alloy.Applications include: engine casings, sumps, aluminiumframework etc.

DIN 1732 EL-Al 99.8

Coated electrode, 99.8% pure aluminium, for welding pureand cast aluminium alloys.

DIN 1732 EL-Al Si 5AWS A 5.3 E4043

Coated electrode containing 5% silicon, for the welding ofwrought and cast aluminium alloys.

G] Bronzes

AWS A 5.6 E Cu Al-A2DIN 1733 EL-Cu A19

For the joining of aluminium bronzes with an aluminiumcontent of up to 10%

AWS A 5.6 E Cu Sn-CDIN 1733 EL-Cu Sn 7

A tin bonze alloy for repair and reclamation of tin andphosphor bronzes.

AWS A 5.6 E Cu Mn Ni AlDIN 1733 EL-Cu Mn 14 Al

For joining and wear surfacing of brass, bronze and cast steel.



This alloy has a low coefficient of friction which makes it anideal alloy for sliding surfaces.

H] Copper

AWS A 5.6 E CuDIN 1733 EL-Cu Mn 2

A 97% copper electrode for the joining and coating of copperand copper alloys.

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