THE PLASMA WELDING HANDBOOK

THEPLASMAWELDINGHANDBOOK

PlasmaThe FourthState ofMatterpage 2

ContentsPAGEIntroduction to Plasma Welding4-7ULTIMA 150 Plasma Welding System8-9Modular Plasma Welding Systems10-13System Layout10Power Supply and Welding Console11Coolant Recirculators12System Component Ordering Information12Plasma Welding Torches13Plasma Welding Torch Parts and Consumables14-17PWH/M 2A Parts and Consumables14PWH/M 3A Parts and Consumables15PWH/M 4A Parts and Consumables16PWM 300 Parts and Consumables17PWM 6A Parts and Consumables17Plasma Welding Controller18Cold Wire Capstan Feeder18-19Modes of Operation - Melt-in Fusion Welding20Modes of Operation - Keyhole Welding21Gas Selection22Troubleshooting23Service Test Procedures23page 3

PlasmaThe term Plasma, refers to a gas that hasbeen sufficiently ionized to conduct anelectrical current. As we see matter in theworld around us, we are usually consciousof its existence in three states . solid, liquidand gas. We are all aware of the differencebetween solids, liquids, and gases, and thefact that increasing the temperature changesa material from one state to another. Whenenough energy is applied to a gas, this willcause an ionization of the gases atomicstructure. This process is visible to us in theform of fluorescent lighting in our homes andoffices, lightning in the night sky, or even ourvery sun. Most of the visible universeis a type of plasma.When energy (heat) is added to a materialin a gaseous state, the temperature of thegas keeps increasing. If enough energy isadded, the temperature becomes high enoughthat the gas no longer exists as individualmolecules. The molecules come apart and thematerial made up of individual atoms, if thetemperature is further increased, the atomswill then lose electrons and become ions. Thismaterial then consists of a combination of ions(with a positive charge) and free electrons.Under these conditions, the matter now existsin a fourth state. the PLASMA state.Plasma has many properties that are similarto those of a gas but also some specialproperties that make it unique. The mostimportant property of the plasma, as faras welding is concerned, is that it containsfree electrons which allows it to easily carryan electrical current. The plasma weldingprocess does not have an exclusive on theuse of plasma as it also exists in all other arcwelding processes. Plasma welding utilizesthe developed hot gases to provide uniquebenefits to the welding operation.page 4

Plasma Arc Welding (PAW)PlasmaOUTPUTArc Welding(PAW) is a weldingprocess that heatsan inert gas to anextremely highPLASMA temperature so thatthe gas becomesionized and electrically conductive. Thisplasma gas is constricted into a columnby an orifice placed downstream of theelectrode which is protected inside thenozzle of torch. The plasma is used totransfer an electric arc to the workpieceto obtain the melting and coalescence ofmost metals and to constrict the arc duringthe welding process.PAWProcessAdvantagesOUTPUTMAX OUTPUTDC CC 150AMPSVOLTAGEAllmetalsINPUTamenableor TIGPOWER to GTAWHERTZwelding can be welded with the plasmaPHASEarc welding showsarc process. Plasmaits greatest advantages in the weldingof high volume repetitive productionoperations. These applications normallydemand repeatable welds on a nearcontinuous basis using the melt-in fusionmode and include spot fusion welds,corner edge welds, lamination welds andcircumferential / seam welds.208460VPlasma now has proven its value in thearea of highly repetitive automated welds.The process provides increased reliabilityand repeatability to meet today’s highstandards of productivity. It is frequentlyused as an alternate to the gas tungstenarc welding process (GTAW).5060For most applications, the plasma arcprocess offers increased electrode life,reliable arc starting, improved arc stability,better penetration control and reducedcurrent levels. In some cases plasmaoffers increased travel speeds, improvedweld quality, and less sensitivity tooperating variables.Plasma welding is not a new process tothe industry, but only in the past few yearshas it gained significant acceptance. Untilrecently, the process was consideredexotic and difficult to understand. Thiswas mainly due to the applications it wasbeing adapted to.Features & Benefits - The Protected ElectrodeOne of the most important features ofthe plasma arc welding process is theProtected Electrode which provideshigher efficiency and reduces downtime inmost applications.The tungsten electrode, which is securedinside the plasma torch and behindthe orifice, is protected from outsideimpurities that would normally attackits hot surface. With this protection, theelectrode is shielded from materials thatcan constantly attack an “exposed”electrode. The protected electrode in theplasma welding torch normally requires achange only once every 8 hours for mostoperations. This reduction in electrodechange allows for increased productivity.The electrode is secured externallyin the TIG welding process (GTAW).This exposes the electrode to thecontaminants (stamping and forming oils,degreasers, oxides, etc.) present on thesurface of the base material to be welded.These contaminants, under intensetemperatures, will attack and erode thetungsten electrode requiring the frequentchanging of the electrode on a repetitivebasis.It is not uncommon in many applicationsfor the electrode in the GTAW torch torequire replacement changes 1 to 2 timesper hour depending on part cleanlinessand production levels. The time requiredto change the electrode depends on theaccessibility of the torches on the fixtureapparatus. Five minutes or more may bespent on each electrode change in somecases, eating away costly productiontime.Multiplying the number of electrodechanges required in an 8 hour shift bythe time required for each change, anddividing by the total amount of productiontime available, will yield the percentageof lost production time. Based on thatnumber, it is now easy to figure parts lostdue to frequent electrode changes. Thisreduction in electrode change allows forincreased productivity.(See chart below)Typical Plasma/TIG Welding Productivity Benefit AnalysisCOMPARISIONTimeTIGHourDayPLASMA2081Minutes ToChangeElectrodes54,99224120Total Parts@ 100% CapacityTIG ElectrodeChanges17PlasmaElectrodeChanges04163Parts LostWith TIGParts LostNet GainWith Plasma Plasma Over 08,16078013,52094,640Value per PartProduction Parts/Financial Gain with Plasma194,640YearShift Hours per WeekDays Worked per WeekApplication: Outside corner welds home appliance245NOTE: 4 welds required on each part. For more information, contact Victor Technologiespage 5WA3YE

Plasma ArcWeldingAdvantages and DisadvantagesReliable, easy-to-operate Thermal Arc PlasmaWelding Systems boost profits and productivityby helping you achieve consistently high qualityrepeatable welds – manually or automatically.Whatever your application needs, the broad,versatile line of Thermal Arc consoles, torches,power supplies, and accessories provide theright tools for the job.Plasma arc welding is measurably the lower costprocess with savings gained through increasedproductivity, reduced scrap, reduced downtime andfewer electrode changes.Plasma arc welding offers many advantages over TIGWelding (GTAW - Gas Tungsten Arc Welding):ADVANTAGES: Reliable Arc Starting Protected Electrode Less Sensitive to Stand-Off Changes Improved Arc Stability at Low Current Lower Current Levels Required Reduced Heat Input or Distortion Arc is More Directional (Less Arc Wander) Improved Weld Geometry and Penetration Control Less Filler Material Required Reduced Current Levels Single-Pass Welds Minimized Weld Preparation Narrower Weld Beads Visual Proof of 100% Weld Penetration Improved Weld GeometryDISADVANTAGES: Limited to Flat, Horizontal, and Vertical-Up Positions More Sensitive to Variable Changes Limited to Automated Operationspage 6

What Is Plasma Arc Welding?Simply stated, Plasma Arc Welding(PAW) is a superior variation to TIGwelding (GTAW) that encloses thetungsten electrode in a protectedenvironment (Figure 1) and deliversthe arc through a cooled copper tip.Enclosing the electrode protects itfrom contamination, thus substantiallyextending its life.The constant stable arc shape ofplasma results in consistent welds foreight hours or more of operation ascompared to automated TIG welding,where deterioration of the exposed TIGelectrode (Figure 2) can result in weldarc variations (Figure 3) in one hour orless of operation. Plasma arc weldinguses a pilot arc (Figure 4) to consistentlytransfer the arc to the work without therepeated use of high frequency current.PROTECTED ELECTRODEELECTRODESUsed TIG ElectrodeNew ElectrodeUsed Plasma ElectrodeFigure 1Figure 2TIG WELD SAMPLEPILOT ARCFigure 3Figure 4Pilot ArcAnother outstanding feature of thePlasma arc welding process is the PilotArc which provides reliable arc startingand contributes to the repeatabilityand increased productivity of plasmawelding.The Pilot Arc is a low current DC arcthat is sustained in the tip area of thetorch to ionize a gas as it passes aroundthe electrode and through the orifice.Arc initiation is provided by the pilotarc that transfers between the tungstenelectrode and the tip. It is started byimposing high frequency (from a smallhigh frequency generator or C.D. arcstarter inside the control console) ona low DC current for a short duration oftime to ionize the gas. Once the pilot archas been established, the requirementsfor high frequency are no longer needed.The pilot arc now remains on to reliablyassist the starting of the main transferredwelding arc from a separate DC powersource.Without the need for high frequencyused in TIG welding (GTAW), the erosionof the electrode by constantly etchingits surface is diminished. This eliminatesthe phenomena of inconsistent arcstarting, resulting in the loss of arcdirectability. The use of a pilot arcinstead of conventional high frequencycircuitry provides extremely reliable arcstarting. This repeatable arc initiationnearly eliminates significant downtimeand minimizes the number of rejectsor reworks due to poor welds thusreducing scrap.Constricted ArcAn orifice (also called a nozzle or a tip)which is inserted into the front end of thetorch body provides for the laminar flowof the plasma gas and constriction of thearc. The magnitude of this constriction isnormally controlled by three variables . theorifice diameter, the plasma gas flow rate,and the electrode setback (the distancethe electrode is recessed within the tip).The arc will be most constricted when thetorch is operated at higher plasma gas flowrates and the electrode placed at maximumsetback. This type arc is typically usedwhen trying to achieve keyhole single passwelds requiring maximum penetration,narrower weld beads, minimized heataffected zone, and reduced base materialdistortion. Keyhole welding is generallyused on material thickness ranging from.090” (2.3 mm) to .250” (6.4 mm).By reducing the electrode setback andplasma gas flow rates, a softer, lessconstricted arc will occur. This type arc istypically used for the melt-in fusion (nonkeyhole) mode and allows for faster travelspeeds on reduced base material thickness.010” (.3 mm) to .187” (4.7 mm).page 7