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LESSON I, PART Acreate welding difficulties.1.7.3Manganese-Manganese in contents up to 1% is usually present in all low alloysteels asa deoxidizer and desulphurizer. That is to say, it readily combines withoxygenand sulphur to help negate the undesirable effect these elementshave when in their natu-ral state. Manganese also increases the tensilestrength and hardenability of steel.1.7.4Chromium- Chromium, incombination with carbon, is a powerful hardeningalloying element. Inaddition to its hardening properties, chromium increasescorrosionresistance and the strength of steel at high temperatures.Chromium is the primary alloyingelement in stainless steel.1.7.5Nickel-

The greatest single property of steel that is improved by the presenceofnickel is its ductility or notch toughness. In this respect, it is the mosteffective of all alloy-ing elements in improving a steel's resistance to impactat low temperatures. Electrodeswith high nickel content are used to weld

cast iron materials. Nickel is also used in combi-nation with chromium toform a group known as austenitic stainless steel.1.7.6Molybdenum-Molybdenum strongly increases the depth of the hardeningcharacteristic ofsteel. It is quite often used in combination with chromium to improvethestrength of the steel at high temperatures. This group of steels isusually referred to aschrome-moly steels.1.7.7Silicon- Silicon is usuallycontained in steel as a deoxidizer. Silicon will addstrength to steel butexcessive amounts can reduce the ductility. Additional amounts ofsiliconare sometimes added to welding electrodes to increase the fluid flow of

weld metal.1.7.8Phosphorus- Phosphorus is considered a harmfulresidual element in steelbecause it greatly reduces ductility and toughness.Efforts are made to reduce it to its verylowest levels; however, phosphorus

is added in very small amounts to some steels toincreasestrength.1.7.9Aluminum- Aluminum is primarily used as a deoxidizer insteel. It may also beused in very small amounts to control the size of thegrains.1.7.10Copper- Copper contributes greatly to the corrosionresistance of carbon steelby retarding the rate of rusting at roomtemperature, but high levels of copper can causewelding difficulties.

1.7.11Columbium- Columbium is used in austenitic stainless steel to act as a stabi-lizer. Since the carbon in the stainless steel decreasesthe corrosion resistance, a meansof making carbon ineffective must be found. Columbium has a greater affinity for carbonthan chromium,leaving the chromium free for corrosion protection.1.7.12Tungsten- Tungsten is used in steel to given strength at hightemperatures.Tungsten also joins with carbon to form carbides that are exceptionally hard, and thereforehave exceptional resistance towear.1.7.13Vanadium- Vanadium helps keep steel in the desirable fine grain condition afterheat treatment. It also helps increase the depthof hardening and resists softening of thesteel during tempering treatments.1.7.14Nitrogen- Usually, efforts are made to eliminate hydrogen,oxygen and nitrogenfrom steel because their presence can cause brittleness. Nitrogen has the ability to formaustenitic structures; therefore,it is sometimes added to austenitic stainless steel to reducethe amount of nickel needed, and therefore, the production costs of thatsteel.1.7.15Alloying Elements Summary- It should be understood that the addition ofelements to a pure metal may influence the crystallineform of the resultant alloy. If a puremetal has allotropic characteristics (the ability of a metal to change its crystal structure) at aspecifictemperature, then that characteristic will occur over a range of temperatures withthe alloyed metal. The range in which the change takesplace may be wide or narrow,depending on the alloys and the quantities in which they are added. The alloying elementmay also effect thecrystalline changes by either suppressing the appearance of certaincrystalline forms or even by creating entirely new forms. All these

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transformations inducedby alloying elements are dependent on heat input and cooling rates. These factors areclosely controlled at the steelmill, but since the welding operation involves a nonuniformheating and cooling of metal, special care is often needed in the welding of lowand highalloy steel.

LESSON I, PART B

Lesson 1The Basics of Arc Welding

Lesson 2Common Electric

Arc Welding ProcessesLesson 3

Covered Electrodes for Welding

Mild SteelsLesson 4

Covered Electrodes for Welding Low Alloy SteelsLesson 5

Welding Filler Metals for Stainless SteelsLesson 6

Carbon & Low AlloySteel Filler Metals -GMAW,GTAW,SAW

Lesson 7Flux Cored Arc Electrodes Carbon Low Alloy Steels

Lesson 8Hardsurfacing Electrodes

Lesson 9Estimating & Comparing Weld Metal Costs

Lesson 10Reliability of Welding Filler Metals

1.8ELECTRICITY FOR WELDING1.8.1Principles of Electricity- Arc welding is a method of joining metals accom-plished by applying sufficient electrical pressure to an electrode to maintain a current path(arc) between the electrode and the work piece. Inthis process, electrical energy ischanged into heat energy, bringing the metals to a molten state; whereby they are joined.The electrode(conductor) is either melted and added to the base metal or remains in itssolid state. All arc welding utilizes the transfer of electrical energyto heat energy, and tounderstand this principle, a basic knowledge of electricity and welding power sources isnecessary.1.8.1.1The threebasis principles of static electricity are as follows:1. There are two kinds of electrical charges in existence - negative and positive.2. Unlikecharges attract and like charges repel.3. Charges can be transferred from one place to another.1.8.1.2Science has established that allmatter is made up of atoms and each atomcontains fundamental particles. One of these particles is the electron, which has the abilitytomove from one place to another. The electron is classified as a negative electricalcharge. Another particle, about 1800 times as heavy asthe electron, is the proton andunder normal conditions the proton will remain stationary.1.8.1.3Material is said to be in an electricallyuncharged state when its atoms contain anequal number of positive charges (protons) and negative charges (electrons). This balanceisupset when pressure forces the electrons to move from atom to atom. This pressure,sometimes referred to as electromotive force, iscommonly known as voltage. It should benoted that voltage that does not move through a conductor, but without voltage, there wouldbe nocurrent flow. For our purposes, it is easiest to think of voltage as the electricalpressure that forces the electrons to move.1.8.1.4Since weknow that like charges repel and unlike charges attract, the tendency isfor the electrons to move from a position of over-supply (negativecharge) to an atom thatlacks electrons (positive charge). This tendency becomes reality when a suitable path isprovided for the movementof the electrons. The transfer of electrons from a negative to apositive charge throughout the length of a conductor constitutes an electrical

current. Therate that current flows through a conductor is measured in amperes and the word ampereis often used synonymously with theterm current. To give an idea of the quantities ofelectrons that flow through a circuit, it has been theoretically established that oneampereequals 6.3 quintillion (6,300,000,000,000,000,000) electrons flowing past a fixed point in aconductor every second.

1.8.1.5Different materials vary in their ability to transfer electrons. Substances, such aswood and rubber, have what is called a tight electronbond and their atoms greatly resistthe free movement of electrons. Such materials are considered poor electrical conductors.Metals, on theother hand, have large amounts of electrons that transfer freely. Theircomparatively low electrical resistance classifies them as goodelectrical conductors.1.8.1.6Electrical resistance is primarily due to the reluctance of atoms to give up theirelectron particles. It may also bethought of as the resistance to current flow.1.8.1.7To better understand the electrical terms discussed above, we might comparethe closedwater system with the electrical diagram shown in Figure 8. You can see that asthe pump is running, the water will move in the direction ofthe arrows. It moves becausepressure has been produced and that pressure can be likened to voltage in an electricalcircuit. The pump canbe compared to a battery or a DC generator. The water flowsthrough the system at a certain rate. This flow rate in an electrical circuit is a

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unit ofmeasure known as the ampere. The small pipe in the fluid circuit restricts the flow rate andcan be likened to a resistor. This unitresistance is known as the ohm. If we close thevalve in the fluid circuit, we stop the flow, and this can be compared to opening a switch inanelectrical circuit.1.8.2Ohm's Law- Resistance is basic to electrical theory and to understand thisprinciple, we must know the Ohm's Law,which is stated as follows: In any electrical circuit,the current flow in amperes is directly proportional to the circuit voltage applied and in-versely proportional to the circuit resistance. Directly proportional means that even thoughthe voltage and amperage may change, the ratioof their relationship will not. For example,if we have a circuit of one volt and three amps, we say the ratio is one to three. Now if weincreasethe volts to three, our amperage will increase proportionately to nine amps. Ascan be seen, even though the voltage and amperage changedin numerical value, theirratio did not. The term "inversely proportional" simply means that if the resistance is

doubled, the current will be reduced to one-half. Ohm's Law can be stated mathematicallywith this equation:I = E RorE = I RorR = E I(E = Volts, I = Amperes, R = Resistance (Ohms))1.8.2.1The equation is easy to use as seen in the following problems:1)A 12 volt batteryhas a built-in resistance of 10 ohms. What is the amperage?12 10 = 1.2 amps2)What voltage is required to pass 15 amps through aresistor of 5 ohms?15 5 = 75 volts3)When the voltage is 80 and the circuit is limited to 250 amps, what is the valueof the resistor?80 250= .32 ohms1.8.2.2The theory of electrical resistance is of great importance in the arc weldingprocess for it is this resistance in the air spacebetween the electrode and the base metalthat contributes to the transfer of electrical energy to heat energy. As voltage forces theelectronsto move faster, the energy they generate is partially used to overcome theresistance created by the arc gap. This energy becomes evidentas heat. In the weldingprocess, the temperature increases to the point where it brings metals to a molten state.1.8.3Electrical Power- The

word"watt"is another term frequently encountered inelectrical terminology. When we pay our electrical bills, we are actually paying forthepower to run our electrical appliances, and the watt is a unit of power. It is defined as theamount of power required to maintain a currentof one ampere at a pressure of one volt.The circuit voltage that comes into your home is a constant factor, but the amperage drawnfrom theutility company depends on the number of watts required to run the electricalappliance. The watt is figured as a product of volts timesamperes and is stated math-ematically with the following equation:W =E IE= W II= W E(W = Watts, E = Volts, I = Amperes)1.8.3.1Theamperage used by an electrical device can be calculated by dividing thewatts rating of the device by the primary voltage for which it is

designed.

1.8.3.2For example, if an appliance is designed for the common household primaryvoltage of 115 and the wattage stamped on the appliancefaceplate is 5, then theamperage drawn by the appliance when in operation is determined as shown:5 115 = .04 amperes1.8.3.3Kilowatt isanother term common in electrical usage. The preface "kilo"is ametric designation that means 1,000 units of something; therefore, onekilowatt is 1,000watts of power.1.8.4Power Generation- Electrical energy is supplied either as direct current (DC) oralternating current (AC).With direct current, the electron movement within the conductor isin one direction only. With alternating current, the electron flow reversesperiodically. Al-though some types of electrical generators will produce current directly (such as batteries,dry cells, or DC generators), mostdirect current is developed from alternating current.1.8.4.1Through experimentation, it was discovered that when a wire is moved throughamagnetic field, an electrical current is induced into the wire, and the current is at itsmaximum when the motion of the conductor is atrightangles to the magnetic lines of force. The sketchin Figure 9 will help to illustrate this principle.1.8.4.2If the conductor is moved upwardsinthe magnetic field between the N and S poles,the galvanometer needle will deflect plus (+).Likewise, if the conductor is moveddownwardsthe needle will deflect minus (-). With thisprinciple of converting mechanical energy intoelectrical energy understood, we canapply it tothe workings of an AC generator.1.8.4.3Figure 10 is a simplified sketch of an ACgenerator. Starting at 0 rotation, the coil wire ismovingparallel to the magnetic lines of force and cutting none of them. Therefore, no current isbeing induced into the winding.1.8.4.4From 0to 90 rotation, the coil wire cuts an increasing number of magnetic linesof force and reaches the maximum number at 90 rotation. Thecurrent increases to themaximum because the wire is now at right angles to the lines of force.

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COPYRIGHT 1999 THE ESAB GROUP, INC.LESSON I, PART B1.8.4.5From 90 to 180 rotation, the coil wire cuts a diminishing number of linesofforce and at 180 again reaches zero.1.8.4.6From 180 to 270, the current begins to rise again but in the opposite directionbecause nowthe wire is in closer proximity to the opposite pole.1.8.4.7One cycle is completed as the coil wire moves from 270 to 0 and the currentagaindrops to zero.1.8.4.8With the aid of a graph, we can visualize the rate at which the lines of force arecut throughout the cycle. If we plot thecurrent versus degree of rotation, we get thefamiliar sine wave as seen in Figure 11.1.8.4.9With this sine wave, we cansee that one completecycle ofalternating current comprises onepositive and one negative wave(negative and positive meaningelectron flow in opposingdirections).The frequency of alternating current isthe number of such complete cyclesper second. For most powerapplications, 60 cycles persecond (60Hertz) is the standard frequency inNorth America.FIGURE 10CONTACTSNNNNSSS

1.8.4.10 Some welders use a three-phase AC supply. Three-phase is simply threesources of AC power as identical voltages brought in by

three wires, the three voltages orphases being separated by 120 electrical degrees. Ifthe sine wave for the three phases are plotted ononeline, they will appear as shown in Figure 12.1.8.4.11This illustrates that three-phase power issmoother than single-phase because theoverlappingthree phases prevent the current and voltage fromfalling to zero 120 times a second, thereby producing asmoother weldingarc.1.8.4.12 Since all shops do not have three-phase power, welding machines for bothsingle-phase and three-phase power areavailable.1.8.5Transformers- The function of a transformer is to increase or decrease voltageto a safe value as the conditions demand.Common household voltage is usually 115 or230 volts, whereas industrial power requirements may be 208, 230, 380, or 460

volts.Transmitting such relatively low voltages over long distances would require a conductor ofenormous and impractical size. Therefore,power transmitted from a power plant must bestepped up for long distance transmission and then stepped down for final use1.8.5.1As canbe seen in Figure 13, the voltage is generated at the power plant at13,800 volts. It is increased, transmitted over long distances, and thenreduced in steps forthe end user. If power supplied to a transformer circuit is held steady, then secondarycurrent (amperes) decreases asthe primary voltage increases, and conversely, secondarycurrent increases as primary voltage decreases. Since the current flow(amperes)determines the wire or conductor size, the high voltage line may be of a relatively smalldiameter.FIGURE 121201 CYCLETHREE PHASEAC2400FIGURE 13POWER TRANSMISSION13,800 VPOWERPLANTSTEPUP287,000VHIGH VOLTAGE300 MILESSTEPDOWN132,000 V34,000 V4,600V208V230V460VFINALUSE

Lesson 1The Basics of Arc Welding

Lesson 2Common Electric

Arc Welding ProcessesLesson 3

Covered Electrodes for WeldingMild SteelsLesson 4

Covered Electrodes for Welding Low Alloy SteelsLesson 5

Welding Filler Metals for Stainless Steels

Lesson 6Carbon & Low AlloySteel Filler Metals -GMAW,GTAW,SAW

Lesson 7Flux Cored Arc Electrodes Carbon Low Alloy Steels

Lesson 8Hardsurfacing Electrodes

Lesson 9Estimating & Comparing Weld Metal Costs

Lesson 10Reliability of Welding Filler Metals

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1.8.5.2The transformer in a welding machine performs much the same as a large powerplant transformer. The primary voltage coming intothe machine is too high for safewelding. Therefore, it is stepped down to a useable voltage. This is best illustrated with anexplanation ofhow a single transformer works.1.8.5.3In the preceding paragraphs, we have found than an electrical current can beinduced into a conductorwhen that conductor is moved through a magnetic field toproduce alternating current. If this alternating current is passed through aconductor, apulsating magnetic field will surround the exterior of that conductor, that is the magneticfield will build in intensity through the first90 electrical degrees, or the first cycle. From thatpoint, the magnetic field will decay during the next quarter cycle until the voltage orcurrentreaches zero at 180 electrical degrees. Immediately, the current direction reverses and themagnetic field will begin to build again untilit reaches a maximum at 270 electrical degreesin the cycle. From that point the current and the magnetic field again begin to decay untiltheyreach zero at 360 electrical degrees, where the cycle begins again.1.8.5.4If that conductor is wound around a material with high magneticpermeability(magnetic permeability is the ability to accept large amounts of magnetic lines of force)such as steel, the magnetic fieldpermeates that core. SeeFigure 14. This conductor is called the primary coil, and ifvoltage is applied to one of its terminals and the circuitiscompleted, current will flow. When a second coil is woundaround that same steel core, the energy that is stored inthis fluctuating magneticfield in the core is induced intothis secondary coil.1.8.5.5It is the build-up and collapse of this magneticfield that excite the electrons in thesecondary coil of thetransformer. This causes an electrical current of the same frequency as the primary coil toflow when the secondarycircuit is completed by striking the welding arc. Remember thatall transformers operate only on alternating current.1.8.5.6A simplified versionof a welding transformer is schematically shown in Figure 15.This welder would operate on 230 volts input power and the primary windinghas 230 turnsof wire on the core. We need 80 volts for initiating the arc in the secondary or weldingcircuit, thus we have 80 turns of wire in

the secondary winding of the core. Before the arcis struck, the voltage between the electrode and the work piece is 80 volts. Rememberthatno current (amperage) flows until the welding circuit is completed by striking the arc.

APPENDIX ALESSON I - GLOSSARY OF TERMSAISIAmerican Iron and Steel InstituteAllotropicAmaterial in which the atoms are capable of transforming into twoor more crystalline structures at different temperatures.AlternatingAnelectrical current which alternately travels in either direction in aCurrentconductor. In 60 cycles per second (60 Hz) AC, the frequencyusedin the U.S.A., the current direction reverses 120 times everysecond.AmpereUnit of electrical rate of flow. Amperage is commonly referredto asthe current in an electrical circuit.ASMEAmerican Society of Mechanical EngineersASTMAmerican Society for Testing andMaterialsAtomThe smallest particle of an element that posses all of thecharacteristics of that element. It consists of protons, neutrons,andelectrons.Carbon Steel(Sometimes referred to as mild steel.) An alloy of iron and carbon.Carbon content is usually below0.3%.ConductorA material which has a relatively large number of loosely bondedelectrons which may move freely when voltage(electrical pressure)is applied. Metals are good conductors.Constant Current (As applied to welding machines.) A welding powersource whichwill produce a relatively small change in amperage despitechanges in voltage caused by a varying arc length. Used mostlyforwelding with coated electrodes.

Constant Voltage (As applied to welding machines.) A welding power source whichwill produce a relatively small change in voltagewhen theamperage is changed substantially. Used mostly for welding withsolid or flux cored electrodes.Direct CurrentAn electrical

current which flows in only one direction in aconductor. Direction of current is dependent upon the electricalconnections to the battery orother DC power source. Terminals onall DC devices are usually marked (+) or (-). Reversing the leadswill reverse the direction of currentflow.ElectronNegatively charged particles that revolve around the positivelycharged nucleus in an atom.FerrousContaining iron.Example: carbon steel, low alloy steels, stainlesssteel.HertzHertz (Hz) is the symbol which has replaced the term cycles persecond.Today, rather than saying 60 cycles per second or s imply60 cycles, we say 60 Hertz or 60 Hz.High Alloy Steels Steels containing in

excess of 10% alloy content. Stainless steel isconsidered a high alloy because it contains in excess of 10%chromium.Induced CurrentorInductionThe phenomena of causing an electrical current to flow through aconductor when that conductor is subjected to a varyingmagneticfield.IngotCasting of steel (weighing up to 200 tons) formed at mill from meltof ore, scrap limestone, coke, etc. InsulatorAmaterial which has a tight electron bond, that is, relatively fewelectrons which will move when voltage (electrical pressure) isapplied. Wood,glass, ceramics and most plastics are goodinsulators

Kilowatt1,000 wattsLow Alloy SteelsSteels containing small amounts of alloying elements (usually 1%to 5% total alloy content)which drastically improves theirproperties.Non-FerrousContaining no iron. Example: Aluminum, copper, copper alloys.OhmUnit of

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electrical resistance to current flow.PhaseTransformationThe changes in the crystalline structure of metals caused bytemperature andtime.ProtonPositively charged particles which are part of the nucleus of atoms.RectifierAn electrical device used to change alternatingcurrent to directcurrent.SAESociety of Automotive EngineersTransformerAn electrical device used to raise or lower the voltage andinverselychange the amperage.VoltUnit of electromotive force, or electrical pressure which causescurrent to flow in an electricalcircuit.WattA unit of electrical power. Watts = Volts x Amperes