shielded metal arc welding.ppt

Shielded Metal Arc Welding

(SMAW)

Shielded Metal Arc Welding

(SMAW)

Tech ConnectWeldingTech ConnectWelding

SMAW Safety PrecautionsSMAW Safety Precautions

Electrical SafetyElectrical Safety

•Make sure all electrical equipment has an Make sure all electrical equipment has an earth ground.earth ground.

•Keep electrical connections tight, clean, and Keep electrical connections tight, clean, and dry.dry.

•Keep work area, equipment, and clothing Keep work area, equipment, and clothing dry.dry.

SMAW Safety Precautions (continued)


Electrical Safety Electrical Safety (continued)(continued)

•Never dip an electrode holder in water.Never dip an electrode holder in water.

•Never touch hot parts of the electrode Never touch hot parts of the electrode holders.holders.

•Remove the electrode from the electrode Remove the electrode from the electrode holder when the work is complete.holder when the work is complete.



Electrical Safety Electrical Safety (continued)(continued)

•Always check the work area for any Always check the work area for any electrical hazards before starting a project.electrical hazards before starting a project.

•Keep welding cables free from conduits, Keep welding cables free from conduits, motors, and other equipment that can cause motors, and other equipment that can cause a short circuit.a short circuit.

•Keep the ground as far away from the arc Keep the ground as far away from the arc as possible.as possible.



Handling welding cablesHandling welding cables

•Never pull a welding cable to force it over an Never pull a welding cable to force it over an obstruction.obstruction.

•Never drag a welding cable through oil.Never drag a welding cable through oil.

•Only use clean, dry rags to clean a welding Only use clean, dry rags to clean a welding cable.cable.

•Properly store welding cables when not in Properly store welding cables when not in use.use.



Handling welding cables Handling welding cables (continued)(continued)

•Never drape a welding cable over any type of Never drape a welding cable over any type of gas cylinder.gas cylinder.



Handling hollow castings and containersHandling hollow castings and containers

•Vent hollow castings before beginning any Vent hollow castings before beginning any heating, cutting, or welding activities.heating, cutting, or welding activities.

•Do not heat, cut, or weld any tanks, drums, or Do not heat, cut, or weld any tanks, drums, or containers.containers.



Working with arc raysWorking with arc rays

•Wear appropriate personal protective Wear appropriate personal protective equipment.equipment.

•Shield work areas to prevent an arc flash from Shield work areas to prevent an arc flash from injuring nearby workers.injuring nearby workers.



Environmental concernsEnvironmental concerns

•Make sure the work area is properly Make sure the work area is properly ventilated.ventilated.

•Wear a respirator when necessary to protect Wear a respirator when necessary to protect from breathing dangerous fumes.from breathing dangerous fumes.

•Wear earplugs during periods of continuous Wear earplugs during periods of continuous loud noise.loud noise.

•Make sure the lighting is bright and free of Make sure the lighting is bright and free of glare.glare.

Personal Protective Equipment for SMAW

Personal Protective Equipment for SMAW

HoodsHoods

Personal Protective Equipment for SMAW (continued)


Hoods Hoods (continued)(continued)



LensesLenses

•Electrode size and amperage determine the Electrode size and amperage determine the level of lens protection.level of lens protection.

•Use the lens manufacturer’s selection chart to Use the lens manufacturer’s selection chart to select the appropriate shade.select the appropriate shade.



Protective clothingProtective clothing

Principles of SMAWPrinciples of SMAW

•SMAW is the most common form of welding.SMAW is the most common form of welding.

•An arc welding machine supplies electric An arc welding machine supplies electric current to an electrode wire.current to an electrode wire.

•The electric current travels through the air gap The electric current travels through the air gap between the end of the electrode wire and the between the end of the electrode wire and the base metal.base metal.

•As the electric current flows through this air As the electric current flows through this air gap, an electric arc is formed.gap, an electric arc is formed.

Principles of SMAW (continued)Principles of SMAW (continued)

•The electric arc produces heat that heats the The electric arc produces heat that heats the base metal to its melting temperature.base metal to its melting temperature.

•The heat from the base metal produces a The heat from the base metal produces a shielding gas that protects the base metal, arc, shielding gas that protects the base metal, arc, electrode, and weld from the atmosphere electrode, and weld from the atmosphere during the welding process.during the welding process.

•As the flux covering on the electrode wire As the flux covering on the electrode wire melts, a shielding gas is created.melts, a shielding gas is created.

Principles of SMAW (continued)Principles of SMAW (continued)

•When the flux cools, it solidifies and forms a When the flux cools, it solidifies and forms a protective slag over the weld bead.protective slag over the weld bead.

• As the electrode wire melts, it becomes the As the electrode wire melts, it becomes the filler metal to the weld.filler metal to the weld.

Advantages and Disadvantages of SMAW


AdvantagesAdvantages

•Equipment is inexpensive.Equipment is inexpensive.

•Equipment is portable.Equipment is portable.

•Applications are simple and adaptable to job Applications are simple and adaptable to job requirements.requirements.

•Can be used with several types of filler Can be used with several types of filler metals.metals.



DisadvantagesDisadvantages

•Requires slag removal.Requires slag removal.

•Harmful gases can be produced when the flux Harmful gases can be produced when the flux melts.melts.

•Changing the electrodes can slow down the Changing the electrodes can slow down the process.process.

Welding Electrical CurrentWelding Electrical Current

Direct current electrode negative (DCEN)Direct current electrode negative (DCEN)

•Electric current that flows from the electrode Electric current that flows from the electrode to the base metal.to the base metal.

•When the electrical current flows in this When the electrical current flows in this direction, the electrode has a negative polarity direction, the electrode has a negative polarity and the base metal has a positive polarity.and the base metal has a positive polarity.

Welding Electrical Current (continued)

Welding Electrical Current (continued)

Direct current electrode positive (DCEP)Direct current electrode positive (DCEP)

•Electric current that flows from the base metal Electric current that flows from the base metal to the electrode.to the electrode.

•When the electric current flows in this When the electric current flows in this direction, the electrode has a positive polarity direction, the electrode has a positive polarity and the base metal has a negative polarity.and the base metal has a negative polarity.

Different Types of Welding Machines

Different Types of Welding Machines

AC transformerAC transformer

•Changes high-voltage, low-amperage AC to Changes high-voltage, low-amperage AC to low-voltage, high-amperage AC.low-voltage, high-amperage AC.

•Used with a 220/240 volt input current.Used with a 220/240 volt input current.

Different Types of Welding Machines (continued)


AC or DC transformer-rectifierAC or DC transformer-rectifier

•Changes high-voltage, low-amperage AC to Changes high-voltage, low-amperage AC to low-voltage, high-amperage AC or DC.low-voltage, high-amperage AC or DC.

•Ideal for adjusting to different materials and Ideal for adjusting to different materials and welding positions.welding positions.



CD generator (motor or engine)CD generator (motor or engine)

•Current varies with the speed that the Current varies with the speed that the armature turns.armature turns.

•Polarity changes can be made by flipping a Polarity changes can be made by flipping a switch or reversing weld connections.switch or reversing weld connections.

•Some machines are powered with AC motors Some machines are powered with AC motors and some machines are powered with gas or and some machines are powered with gas or diesel engines.diesel engines.



Inverter power sourcesInverter power sources

•Utilizes solid-state components to change the Utilizes solid-state components to change the incoming 60 Hz power to a higher frequency.incoming 60 Hz power to a higher frequency.

•Changing the frequency results in greatly Changing the frequency results in greatly reducing the size and weight of the reducing the size and weight of the transformer.transformer.

•This machine can be used with all processes.This machine can be used with all processes.

Characteristics of ElectrodesCharacteristics of Electrodes

Electrode coveringElectrode covering

•Adds filler metal to the weld.Adds filler metal to the weld.

•Creates a protective gas shield around the arc Creates a protective gas shield around the arc and molten metal.and molten metal.

•Creates a flux to clean impurities from the Creates a flux to clean impurities from the molten metal.molten metal.

•Creates a hard slag covering to protect the Creates a hard slag covering to protect the molten weld bead as it cools.molten weld bead as it cools.

Characteristics of Electrodes (continued)


Electrode covering Electrode covering (continued)(continued)

•Improves mechanical and chemical properties Improves mechanical and chemical properties of the weld by adding alloying elements to the of the weld by adding alloying elements to the weld metal.weld metal.

•Determines the current type and polarity Determines the current type and polarity specifications of the electrode.specifications of the electrode.



Electrode sizeElectrode size

•Available in a variety of lengths and Available in a variety of lengths and diameters.diameters.

•Diameter of the electrode refers to the Diameter of the electrode refers to the diameter of the uncovered wire.diameter of the uncovered wire.

Factors that Affect Electrode Selection

Factors that Affect Electrode Selection

•Type of base metalType of base metal

•Metal thicknessMetal thickness

•Groove designGroove design

•Joint alignmentJoint alignment

•Available welding currentAvailable welding current

•Skill level of the welderSkill level of the welder

Factors that Affect Electrode Selection (continued)

Factors that Affect Electrode Selection (continued)

•Welding positionWelding position

•Rate of the weld depositRate of the weld deposit

•Depth of penetrationDepth of penetration

•Weld bead finishWeld bead finish

Causes and Effects of a Good or Bad Weld

Causes and Effects of a Good or Bad Weld

Causes and Remedies for Common SMAW ProblemsCauses and Remedies for Common SMAW Problems

Causes and Remedies for Common SMAW Problems

(continued)

Causes and Remedies for Common SMAW Problems

(continued)

Procedure for Striking and Maintaining an Arc

Procedure for Striking and Maintaining an Arc

Scratch methodScratch method

•Move the electrode across the base metal at Move the electrode across the base metal at an angle like you would use to strike a match. an angle like you would use to strike a match.

•When the arc starts, raise the electrode When the arc starts, raise the electrode slightly to make a long arc, and then return to slightly to make a long arc, and then return to normal arc length.normal arc length.

Procedure for Striking and Maintaining an Arc (continued)

Procedure for Striking and Maintaining an Arc (continued)

Tap methodTap method

•Move the electrode downward in a vertical Move the electrode downward in a vertical direction until it just taps the base metal.direction until it just taps the base metal.

•Slightly raise the electrode to form a long arc.Slightly raise the electrode to form a long arc.

•Return to normal arc length.Return to normal arc length.

Different Bead PatternsDifferent Bead Patterns

Different Bead Patterns (continued)Different Bead Patterns (continued)