Welding Types Procedures Parameters

7/30/2019 Welding Types Procedures Parameters

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PRESENTATION ON

WELDING



CONTENTS INTRODUCTION

Definition of welding Types of welding processes & applications

Power sources : SMAW, Electrode designation,coating, Orientation.

GTAW, shielding gases, Electrodes. Welding procedures,parameters.

Types of weld joints,positions,symbols andgeometry.

Arc blow. Relevant standards and codes.

Related processes

Welding and gas cutting safety



INTRODUCTION

Welding is the process of joining metals by melting the parts and then using a filler to

form a joint.

Welding can be done using different energy sources, from a gas flame or electric arc to a laser or ultrasound

The primary differences between the various welding processes are the methodsby which heat is generated to melt the metal.



A is a materials joining

process which produces coalescence of materials

by heating them to suitable temperatures with or

without the application of pressure or by the

application of pressure alone and with or without the use of filler material .

AWS DEFINITION



DEFINITION OF WELDING

Welding is a process of joining two metals.

To make a joint of two metals , immense heat is

required for melting the parts to be joined.





TYPES OF WELDING PROCESSES &

APPLICATIONS

• SMAW

• GMAW

• GTAW

• SAW

• FCAW

• PAW

• Flash welding• Seam welding

• Spot welding

• Upset welding

• Diffusion welding

• Explosion welding

• Friction welding

• Forge welding

• Hot pressure welding• Roll welding

• Ultrasonic welding

• Electron beam welding

• Electro-slag welding

• Induction welding

• Laser beam welding

• Percussion welding

• Thermit welding



TYPES OF WELDING PROCESSES

& APPLICATIONS

Arc welding is done through the use of an electricalcurrent, and can be performed by using inexpensiveequipment.

Gas Welding is widely used for repair work, especially in anything involving pipes and tubes. Gas welding is

common in the jewelry industry, as well as for the welding of plastics and other materials that cannotstand higher temperatures.

Resistance welding involves the use of additionalsheets of metal to encase the pieces to be welded together. It is the most environmentally-friendly of all

methods, but it requires costly equipment that cannotbe used in all situations.

Energy beam welding, also known as laser beam welding, is one of the most modern techniques used.Laser welding is fast and accurate, but the highequipment cost makes it prohibitive for many

industries



GAS WELDING

One of the most popular welding methods uses a gas flame asa source of heat.

In the oxy-fuel gas welding process ,heat is produced by burning acetylene, mixed with oxygen.

Gas welding is widely used in maintenance and repair work because of the ease in transporting oxygen and fuel cylinders.

Oxy-fuel process is adaptable to brazing, cutting, and heat treating all types of metals



ARC WELDING

Arc welding is a process that uses an electric arc to join themetals being welded.

A distinct advantage of arc welding over gas welding is theconcentration of heat.

This heat concentration also increases the depth of

penetration and speeds up the welding operation; All arc-welding processes have three things in common:

• a heat source,

• filler metal, and

• shielding.

The source of heat in arc welding is produced by the arcing of an electrical current between two contacts.



SHIELDED METAL ARC WELDING (SMAW)

, also known as Manual

, Stick Welding, Covered Electrode Welding or lectric Arc Welding, is the most widely used of the various arc weldingprocesses

is performed by striking an arcbetween a coated-metal electrode and the base metal.

Once the arc has been established, the molten metal from the tip of the electrode flows together with the molten metal from the edges of the base metal to form a sound joint. This processis known as

The coating (flux) from the electrode forms a covering over

the weld deposit, shielding it from contamination; therefore the process is called

This forms the gas and slag to shield the arc and molten weldpool.

The flux also provides a method of adding scavengers,

deoxidizers, and alloying elements to the weld metal.



In arc welding, the intense heat needed to melt

metal is produced by an electric arc

ARC WELDING FUNDAMENTALS



This shows how the coating on a coated (stick) electrode

provides a gaseous shield around the arc and a slag

covering on the hot weld deposit



DIFFERENCE BETWEEN GAS WELDING AND

ARC WELDING



SMAW WELDING EQUIPMENT

One reason for the wide acceptance of the SMAW process is the simplicity of the necessary equipment.

The equipment consists of the following items. Welding power source

Electrode holder

Ground clamp

Welding cables and connectors

Accessory equipment (chipping hammer, wire

brush) Protective equipment (helmet, gloves, etc.)



WELDING POWER SOURCES

STATICROTARY

Transformer Rectifier Motor

generators

Engine

driven

Single phaseinput ,

Constant current

Type AC

Single/ 3 phase

input

Constant current/

Voltage type DCHF (High frequency) unit

during GTAW.



WELDING POWER SOURCES Shielded metal arc welding may utilize either alternating current (AC) or direct

current (DC), but in either case, the power source selected must be of the constant

current type.

This type of power source will deliver a relatively constant amperage or weldingcurrent regardless of arc length variations by the operator

The amperage determines the amount of heat at the arc and since it will remain

relatively constant, the weld beads produced will be uniform in size and shape.

Whether to use an AC, DC, or AC/DC power source depends on the type of welding tobe done and the electrodes used. The following factors should be considered:

- Using a DC power source allows the use of a greater rangeof electrode types. While most of the electrodes are designed to be used on AC or

DC, some will work properly only on DC

- DC power sources may be used for welding both heavy sectionsand light gauge work. Sheet metal is more easily welded with DC because it iseasier to strike and maintain the DC arc at low currents.

While polarity affects the penetration and burn-off rate, the electrode coating also

has a strong influence on arc characteristics.



DC current vs AC current

Voltage drop occurs incable in DC welding.

Useful in low current andsmall electrode diameter.

Susceptible to arc blow.

Arc is smooth anduniform especially forsmall dia. Electrode.

Better suitable for welding sheet metal.

Not suitable for thick sections due to arc blow.

Voltage drop does not

occur in AC welding. Not useful in low currents

and small electrodediameters

In-susceptible to arc blow.

Arc is not smooth anduniform especially forsmall dia. Electrode.

Not suitable for weldingsheet metal.

Suitable for thick sectionsas arc blow is not serious



WELDING MACHINES



The electrode holder connects to the welding cable and conducts the welding current to the electrode.

The insulated handle is used to guide the electrode over the weld joint and feed the electrode over the weld joint and feed the electrode into the weldpuddle as it is consumed.

The ground clamp is used to connect the ground cable to the work piece.

It may be connected directly to the work or to the table or fixture upon which the work is positioned.

The electrode cable and the ground cable are important parts of the weldingcircuit.

They must be very flexible and have a tough heat-resistant insulation. Connections at the electrode holder, the ground clamp, and at the power

source lugs must be soldered or well crimped to assure low electricalresistance.





PROTECTIVE EQUIPMENT



WELDING GLASS



PROTECTIVE EQUIPMENT



COATED ELECTRODES

Various types of coated electrodes are used in shieldedmetal arc welding.

Electrodes used for welding mild or carbon steels arequite different than those used for welding the low alloysand stainless steels.

FUNCTIONS OF ELECTRODE COATINGS



The functions of the coating on covered electrodes are as follows:

Shielding of the Weld Metal (Cellulose, calcium carbonate. )

Stabilization of the Arc (Potassium titanate / sillicate. )

Alloying Additions to Weld Metal (Ferromanganese )

Concentration of the Arc Stream

Furnish Slag for Fluxing (Fluorspar, TiO2 (rutile) , Feldspar, Silica, Manganese oxide, Iron oxide.)

Characteristics for Welding Position

Control of Weld Metal Soundness

Specific Mechanical Properties to the Weld Metal

Insulation of the Core Wire.

FUNCTIONS OF ELECTRODE COATINGS







STICK WELDING BENEFITS

Equipment used is simple, inexpensive, and portable

Electrode provides and regulates its own flux

Lower sensitivity to wind and drafts than gas shielded welding

processes

All position capability



COMMON STICK WELDING CONCERNS

Weld discontinuities

Undercut

Incomplete fusion

Porosity

Slag Inclusions Cracks



ELECTRODE ORIENTATION AND

MANIPULATION IN SMAW





TYPE OF WELD BEADS



UNDER CUT



STICK WELDING PROBLEMS

Arc Blow

Arc Stability

Excessive spatter

Incorrect weld profile

Rough surface

Porosity



( )



GAS TUNGSTEN ARC WELDING (GTAW)

is a welding process performed using the heat of an arc

established between a non-consumable tungsten electrode and the work piece

The primary difference between shielded metal arc welding and gas shielded arc welding is the type of shielding used.

In gas shielded arc welding, both the arc and the molten puddle are covered by a shield of inert gas.

The shield of inert gas prevents atmospheric contamination , thereby producing a better weld.

The processes used in gas shielded arc welding are knownas "TIG" (Tungsten Inert Gas) welding

If filler wire is used, it is added to the weld pool separately.



GAS TUNGSTEN ARC WELDING (GTAW)







EQUIPMENT AND OPERATION

Gas tungsten arc welding may be accomplished with relatively simple

equipment, or it may require some highly sophisticated components.

Choice of equipment depends upon the type of metal being joined, theposition of the weld being made, and the quality of the weld metal necessary

for the application.

The basic equipment consists of the following:

• Constant current type power source

• High frequency unit ( HF unit)

• Electrode holder (torch)

• Shielding gas

• Tungsten electrode• Filler wire

• Water supply when necessary

• Ground cable

• Protective equipment



POWER SOURCE

Both AC and DC power sources are used in gas tungsten arc welding.

They are the constant current type with a drooping volt-ampere curve.

This type of power source produces very slight changes in the arc current when the arc length (voltage) is varied.

The choice between an AC or DC welder depends on the type and thicknessof the metal to be welded.

Distinct differences exist between AC and DC arc characteristics, and if DCis chosen, the polarity also becomes an important factor.

In GTAW where no flux coating exists, heat distribution between theelectrode and the work is controlled solely by the polarity.



HIGH FREQUENCY UNIT (HF)

HF unit is required in GTAW process to initiatearc between electrode and work piece without touching the electrode.

This eliminates contamination of tungstenelectrode and weld deposit

High frequency voltage at low current issuperimposed on the welding current to producearc.

HF unit is switched off after initiation of arc in

DC welding. HF unit is continued after initiation of arc in AC

welding.



TIG TORCH



Shielding Gases

Argon

Argon + Hydrogen

Argon/Helium





ARGON GAS REGULATOR

/ FLOW METER



TUNGSTEN ELECTRODES

Electrodes for gas tungsten arc welding are available in diameters from.010" to 1/4" in diameter and standard lengths range from 3" to 24".

The shape of the tip of the electrode is an important factor in gas tungstenarc welding.

When welding with DCEN, the tip must be ground to a point.

The included angle at which the tip is ground varies with the application, the electrode diameter, and the welding current.

Narrow joints require a relatively small included angle.

Properly ground electrodes will assure easy arc starting, good arc stability,and proper bead width.

When welding with AC, grinding the electrode tip is not necessary.



TUNGSTEN ELECTRODE



ELECTRODES USED IN GTAW

FILLER METALS/ELECTRODES



FILLER METALS/ELECTRODES

The material that you add to fill space during the weldingprocess is known as the filler metal, or material.

Two types of filler metals commonly used in welding are welding rods and welding electrodes.

The term welding rod refers to a form of filler metal that does not conduct an electric currentduring the welding process.

The only purpose of a welding rod is to supply filler metal to the joint.

In electric-arc welding, the term electrode refers to the component that conducts the current from the electrode holder to the metal being welded.

Electrodes are classified into two groups: consumable and non-consumable.

Consumable electrodes not only provide a path for the current but they also supply filler metal to the joint.

An example is the electrode used in shielded metal-arc welding.

Non-consumable electrodes are only used as a conductor for the electrical current, such asin gas tungsten arc welding.

The filler metal for as tun sten arc weldin is a hand fed consumable weldin rod.

FILLER WIRE DESIGNATION-ER70S2



FILLER WIRE DESIGNATION ER70S2

ER- Electrode Wire 70- Tensile strength of deposited weld metal in 1000 PSI

S- Solid wire

2- Chemistry of electrode

EXAMPLE OF S.S. ELECTRODE

ER308 , ER308L , ER309 , ER310,

ER316,ER316L

WELDING OF DISIMILAR METALS

C.S To S.S. ---- ER309

ELECTRODE POLARITY



ELECTRODE POLARITY

Electrode gets more heated.70% heat generated atelectrode,30% heat generated at work piece.Shallow,widepenetration.Has oxide cleaning action in Al & Mg.(Reversepolarity)

Work piece gets more heated.70% heat generated at work piece,30% heat generated at electrode.Deep,narrow penetration.Does not have oxide cleaning action.(Straightpolarity)

.

Work piece and electrode get equally heated.Used for welding aluminium for breaking the oxide layer duringevery half cycle.



DCEP, DCEN, AC

AC-Medium

penetration

DCEN-Deep penetration

DCEP: Shallow penetration.Also called

Reverse polarity. Electrode gets more

heated.70% heat generated at

electrode,30% heat generated at

work piece.Shallow,wide penetration

AC:Medium penetration.

DCEN: Also called straight polarity.Work piece gets more heated.70%

heat generated at work piece,30%

heat generated at electrode.Deep,

narrow penetration.

PROCEDURE FOR TIG WELDING



PROCEDURE FOR TIG WELDING







GTA welding vertical downward

GTA welding vertical upward

GTA welding overhead

GTA welding in the horizontal position

TIG WELDING BENEFITS



TIG WELDING BENEFITS

Superior quality welds

Welds can be made with or without filler metal

Precise control of welding variables (heat)

Free of spatter

Low distortion



GTAW WELDING LIMITATIONS

Requires greater welder dexterity than MIG or stick welding

Lower deposition rates

More costly for welding thick sections

COMMON GTAW WELDING CONCERNS



COMMON GTAW WELDING CONCERNS

Undercutting

Tungsten inclusions

Porosity

Weld metal cracks

Heat affected zone cracks

GTAW WELDING PROBLEMS



GTAW WELDING PROBLEMS

Erratic arc

Oxidized weld deposit

Arc wandering

Porosity

Difficult arc starting



SOLDERING AND BRAZING

Soldering and Brazing are joining processes where parts are joined without melting the base metals.

Soldering filler metals melt 840 °F.

Brazing filler metals melt 840 °F.

Soldering is commonly used for electrical connection or

mechanical joints, but brazing is only used for mechanical joints due to the high temperatures involved



OXY FUEL GAS WELDING SET-UP



OXYGEN AND DA CYLINDER SPECIFICATION



GAS REGULATORS



GAS REGULATORS



GAS CUTTING TORCHES



GAS CUTTING TORCHES



GAS CUTTING BRAZING NOZZLES



CHECK VALVES , FLASH BACK ARRESTORS

TORCHES WELDING AND CUTTING TIPS



SOLDERING AND BRAZING BENEFITS

Economical for complex assemblies

Joints require little or no finishing

Excellent for joining dissimilar metals

Little distortion, low residual stresses

Metallurgical bond is formed

Sound electrical component connections

SOLDERING AND BRAZING JOINING



SOLDERING AND BRAZING JOINING

PROBLEMS

No wetting

Excessive wetting

Flux entrapment

Lack of fill (voids, porosity)

Unsatisfactory surface appearance

Base metal erosion

WELD JOINT GEOMETRY POSITIONS AND WELDING



WELD JOINT GEOMETRY,POSITIONS AND WELDING

SYMBOLS

As per ANSI/AWS A3.0,Standard

welding terms and

definition,

• BUTT

• CORNER

• TEE

• LAP

• EDGE

• SQUARE

• SINGLE BEVEL

• DOUBLE BEVEL

• SINGLE-J

• DOUBLE-J

• FLANGE EDGE

• ROUND EDGE

TYPE OF JOINTS



TYPE OF JOINTS







FILLET JOINT / LAP JOINT



FILLET JOINT / LAP JOINT









The edges of the metal to be welded (base metal) are oftenprepared for welding by cutting, machining, or grinding.

This preparation is done to ensure that the base metal is welded through its entire thickness.

Edge preparation is also done on thick metal to open up the joint area. This provides a space large enough to permit welding at the bottom of the joint.

EDGE PREPARATION



JOINT DESIGN & PREPARATION

Work piece thickness: For thin materials, low heat input andlesser penetration is required. Thick material requires highheat input and deeper penetration.

Depth-width ratio: Large depth-width ratio may cause crackingduring solidification if volume of deposited metal is large.

Cleanliness of base metal is very important.

Preheating reduces residual stresses, drives off moisture,reduces quench hardening and gives gases and slag (if any)more time to reach the surface of the weld before solidificationoccurs.





SYMBOLS

• Groove welds

• Fillet welds

• Plug or slot welds

• Stud welds

• Back or backing welds

• Surfacing welds

• Flange welds

• Spot or projection

welds

• Seam welds

EDGE PREPARATION



EDGE PREPARATION





PARTS OF JOINTSThe of a joint is that portion of the joint where the metals



The of a joint is that portion of the joint where the metalsare closest to each other.

A is an opening or space provided between the edges

of the metal parts to be welded. The is that surface of a metal part included in the

groove

The is the portion of the prepared edge of a part tobe joined by a groove weld that has not been grooved.

The is basically a root face of zero width, The is the angle formed between the prepared edge

of a member and a plane perpendicular to the surface of themember.

The is the total angle of the groove between the

parts to be joined. The is the radius used to form the shape of a J-

or U-groove weld joint. It is used only forspecial groove joint designs.

As a general rule, gas welding requires a larger groove

angle than manual metal-arc welding.

The refers to the separation between the parts to be joined at the root of the joint.

It i ti ll d th “ t g ”



It is sometimes called the “root gap.”

To determine the bevel angle, groove angle, and root opening for a joint, you must consider the thickness of the weld

material, the type of joint to be made, and the welding process to be used.

Having an adequate root opening is essential for rootpenetration.

refers to the depth that a weld extends into

the root of the joint. refers to the minimum depth that a groove

(or a flange) weld extends from its face into a joint, exclusiveof weld reinforcement.

Weld reinforcement is a term used to describe weld metal in

excess of the metal necessary to fill a joint. The root opening is usually governed by the diameter or the

thickness filler material.This, in turn, depends on theof the base metal and the welding position.

WELD JOINT GEOMETRY,POSITIONS AND



WELDING SYMBOLS

JOINT GEOMETRY

GROOVE FACE

ROOT FACE

ROOT EDGE

ROOT OPENING

BEVEL ANGLE

GROOVE ANGLE

NOMENCLATURE



NOMENCLATURE







NOMENCLATURE



TYPICAL EXAMPLE



TYPICAL EXAMPLE



BASE METAL PROPERTIES



High thermal conductivity of base metal requires morepre-heat and greater heat input.

High coefficient of thermal expansion will affect the

fit-up, required allowance for distortion and shrinkageand the amount of residual stress produced.

If the difference between solidus and liquidus temperature is high there are more chances of cracking during solidification.

Base metals having high hardness and low yieldstrengths are more difficult to join.

WELD JOINT GEOMETRY,POSITIONS AND

WELDING SYMBOLS



WELDING SYMBOLS

WELD POSITIONS 1G,1G rotated,1F

2G,2F,2FR

3G,3F

4G,4F 5G,5F

,6F





WELDING POSITIONS





ARC BLOW



Bending of the arc away from the intended path due tounbalance in magnetic field is called Arc blow.

Arc blow causes excessive weld spatter and weld defects.

Arc blow occurs at end of joints, corners , complex structuresand near ground clamp locations.

Arc blow is mainly caused in magnetic materials & DC currentbecause the induced magnetic fields are in one direction.

In AC current, arc blow does not occur because of creation anddestruction of magnetic field during each current cycle.

Forward arc blow and backward arc blow depending on

direction of welding. Methods to avoid arc blow include use of AC current, placement

of ground connection as far as possible from the joint to be welded, using shortest possible arc , reduce welding current.

ARC BLOW



WELDING SYMBOLS



WELDING SYMBOLS

WELDING SYMBOL ELEMENTS

Reference line

Arrow

Tail

Basic weld symbol

Dimensions and other data

Supplementary symbols

Finish symbols Specification,process or other reference.

WELDING SYMBOLS



WELDING PARAMETERS



Voltage

Current

Process type

Current polarity

Weld position

Progression

Backing

Material specification,group

no. Base metal thickness

Weld joint geometry

Welder qualification.

Pipe/plate Filler metal spec.,class,F-

no.

Gas flux,flow,purity.

Root/Filling/Final Pre-heat

Interpass temperature

Post weld heat treatment.

Back purging Travel speed

Weld deposition

technique.

ESSENTIALS FOR PROPER WELDING



PROCEDURES

o Correct electrode size

o Correct current

o Correct arc length or voltage

o Correct travel speed

o Correct electrode angle

ESSENTIAL VARIABLES INVOLVED IN THE

PROCEDURE USUALLY INCLUDE



PROCEDURE USUALLY INCLUDE

o The welding process and its variation

o The method of applying the process

o The base metal type, specification, or composition

o The base metal geometry, normally thickness

o The base metal need for preheat or post heat

o The welding position

o The filler metal and other materials consumed in making the weld

o The weld joint, that is, the joint type and the weld

o Electrical or operational parameters involved Welding technique

SELECTING WELDING PROCESS



This involves the type of metal, the thickness of the metal, the

position of welding, etc. This also leads into the question of filler metal to be used.

This involves matching base metal composition, matching thebase metal properties, particularly strength, and providing

weld metal that will withstand the service involved.

In surfacing, the surface characteristics desired for the finished job depend entirely on the service to which the surface will be exposed.

When wear is involved, surfaces can be rebuilt many times without reducing the strength of the part and the service life

will be greatly extended. The repair procedure should be very similar to a procedure

developed for welding a critical part. It should include theprocess and filler metal and the technique to be used inmaking welds.

WELDING PROCEDURE



" The AWS definition for a welding procedure is "the detailed

methods and practices including all joint welding procedures

involved in the production of a weldment .“

The joint welding procedure mentioned includes "the materials,

detailed methods and practices employed in the welding of a

particular joint."

This is accomplished by writing a procedure which is simply a

"manner of doing" or "the detailed elements (with prescribed

values or range of values) of a process or method used to

produce a specific result





COMMONLY USED MATERIALS



Carbon Steel

Stainless Steel

Titanium

Nickel and its alloys

Low alloy steel

Copper , Brass, Bronze

ALLOY SELECTION



Base metal and filler metal alloy selection is critical toproducing good quality welds.

Proper alloy selection can reduce numerous welding problems

Base metal and filler metal alloy selection is critical toproducing good quality welds.

Proper alloy selection can reduce numerous welding problems

BENEFITS FROM PROPER ALLOY SELECTION



Increase weld quality and yield

Proper weld joint strength

Good corrosion and oxidation resistance

Reduction of weld and HAZ cracking

Eliminate reheat cracking

Eliminate stress corrosion cracking

Eliminate lamellar tearing

Improved weldability Optimize dissimilar metal joints

WELDING STEEL ALLOY



Steel Alloys can be divided into five groups :

Carbon Steels

High Strength Low Alloy Steels

Quenched and Tempered Steels

Heat Treatable Low Alloy Steels

Chromium-Molybdenum Steels

RELEVANT CODES,STANDARDS AND

SPECIFICATIONS



SPECIFICATIONS

Enforced by law,hence is mandatory.

• AWS D1.1-Structural welding code-Steel

• AWS D1.2-Structural welding code-Aluminum.

• AWS D1.3-Structural welding code-Sheet steel.

• AWS D1.4-Structural welding code-Reinforcing steel.

• AWS D1.5-Bridge welding code

• AWS D9.1-Sheet metal welding code.

• ASME Sec.II,part C-Specification for welding rods,electrodesand filler metals.

• ASME Sec.IX-Welding and brazing qualifications.

• ASME Sec.VIII-Rules for construction of ressure vessels.

RELEVANT CODES,STANDARDS ANDSPECIFICATIONS



STANDARDS

• “Something established for use as a rule or basis of comparison in measuring or judgingcapacity,quantity,content,extent,value,quality etc.”

Non-mandatory.

• API 1104-Standard for welding pipelines and related facilities.

• ASTM-American society for testing and materials.

SPECIFICATIONS

• “A detailed description of the parts of a whole;statement orenumeration of particulars, as to actual or requiredsize,quality,performance,terms etc.”

e.g AWS A5.1-Requirements for carbon steel covered electrodes forSMAW.

RELEVANT CODES,STANDARDS AND

SPECIFICATIONS



SPECIFICATIONS

D14.1-Specification for welding industrial andmill cranes.

D14.2-Specification for metal cutting machine tool weldments

D14.3-Specification for welding earthmoving andconstruction equipment.

D14.4-Classification and application of welded joints for machinery and equipment.

D14.5-Specification for welding presses andpress components.

D14.6-Specification for rotating elements of equipment.

DISTORTION AND DISTORTION CONTROL



OXY FUEL GAS CUTTING



is used to sever metals by means of thechemical reaction of oxygen with the base metal at elevated temperatures.

The necessary temperature is maintained by means of gas flames obtained from the combustion of a fuel gas and oxygen.

PLASMA ARC CUTTING



is an arc cutting process with a higher arc voltage which severs metal by melting a localized area with a constricted arc and removing the molten material with a high-

velocity jet of hot ionized gas.

Heat input at the plasma arc is so high that the metal is meltedand a hole is formed. The plasma gas at a high velocity helpscut through the metal. Plasma cutting is ideal for gouging and

for piercing.

For some operations air is used as the plasma gas. A higher arc voltage is normally used

CARBON STEEL (ASME P-1)



( )

the most commonly incorporated metal. Carbon steel is used to

produce structural steel, steel flanges, forgings (SA 105), piping

(SA53 and SA106), boiler tubes (SA178 and SA192), bars,

bolting and lower-temperature, and pressure-vessel plating

STAINLESS STEEL (ASME P-8)



( )

chromium and chromium nickel alloy are two comparable metals that are very resistant to high temperatures and corrosion.

Typically, these composites are used to fabricate process-piping

systems, storage tanks and pressure vessels.

HASTELLOY (ASME P-44, P-45)



( , )

a cobalt-based alloy that is highly resistant to corrosion andexcessive heat. It is often the material of choice when fabricating

products associated with acetic acids, acid etching, cellophane

manufacturing, chlorinating systems, electromagnetizing rolls,

expansion bellows, flue gas scrubbers, geothermal wells,

pesticide production, pickling systems, phosphoric acid

production, SO2 cooling towers, incineration scrubber systems,

sulforation systems and HF furnace scrubbers.

TITANIUM (ASME P-51, P-53)



a lightweight metal with a relatively high tensile strength. Due to

the fact that titanium is very sensitive to contamination and

embrittlement , it is often produced in alloy form and has

associated, determined grades of relation. For example: grades 1,

2 and 3 are unalloyed titanium, whereas grade 7 has a slight

palladium contribution. Since titanium is fragile, cleanliness andexactness are pertinent to its employment. Any weld performed on

this metal may only be implemented with a purge-trailing and

shielding gas. Most commonly, argon gas is utilized and may only

be substituted with an argon-helium mixture.

CHROME MOLYBDENUM (ASME P4-P5A)



a low-carbon, alloy steel implemented in high-temperatureservice. Grade 11 is preferred with moderate to high

temperature, general steam applications. For higher

temperatures, grade 22 is used. The percentage of manganese

ranges from 30-60%. The nominal tensile strength is 60KS.

STELLITE



is a cobalt-based alloy welded to internal and external surfaces to

provide corrosion-resistant alloy surfacing and erosion-resistant

hard facing.

BRONZE ALLOYS



BRONZE ALLOYS (Aluminum bronze, brass, nickel aluminumbronze, manganese bronze and nickel-manganese bronze) are

used primarily to repair condensers, pump casings, valve bodies,

and various other components

ALUMINUM (ASME P-21-25)



ALUMINUM (ASME P-21-25) may be supplied in many forms. Thelargest attribute of aluminum is that it provides a lightweight

material that has a moderate tensile strength, good heat-transfer,

corrosion-resistant properties, and is an acceptable electrical

conductor. Often aluminum is found in alloys that include

manganese, magnesium and titanium, which increase their

strength and diversify their applicable utility

COPPER ALLOYS



COPPER ALLOYS are a non-ferrous metal group that has excellentductile, thermal, electrical and corrosion-resistant properties.

Combining nickel with copper creates an alloy that has a superior

heat and corrosion resistance. Therefore, copper nickel (ASME P-

34) is more often used to make heat exchangers and condenser

tubing, as well as, chemical equipment.

NICKEL COPPER (MONEL)



NICKEL COPPER (MONEL) is a nickel alloy (ASME P-43, P-45).Inconel is one such alloy. These metals provide good corrosion

resistance combined with high strength at increased

temperatures. More commonly, nickel copper is a material of

choice when fabricating pump shafts, valves, springs, seamless

tubes and pipes, as well as, other applications necessitating these

property characteristics.



Safety in welding



Welding, cutting, and brazing areexceptionally dangerous.

Compressed gases are often used to create an extremely hot flame.

Different welding techniques cancause other hazards.

The welder can be injured orcause damage to the work area innumerous ways including fire,explosion, gas, and fume hazards.

Good work practices must be followed in all welding, cutting,and brazing techniques to prevent

injuries, fires, and explosions.



Before starting actual arc welding the student should be fully aware of the dangers involved. The high temperature arc

and hot metal can cause severe burns. In addition the electric

arc itself provides an additional safety hazard.



The electric arc emits large amounts of ultra violet and

infra-red rays.

Both types of rays are invisible to the naked eye just as the same

type of rays emitted by the sun are invisible. However they both

have the identical properties of causing sunburn on the human

skin, except that the arc burns much more rapidly and deeply.

Since these rays are produced very close to the operator they

can cause very severe burns to the eyes in a short exposure time.

When welding with the electric arc, there is added danger



g , g

that the small globules or droplets of molten metal may leave the

arc and fly in all directions. These so called sparks range in temperature from 2000 ° to 3000° Fahrenheit and in size from

very small to as large as ¼ inch. They present a personal burn

hazard plus a fire hazard if they fall in inflammable material.



The welding operator needs to protect himself, by means of a helmet and other protective devices from the harmful rays of

the arc and flying sparks. The filter plates in the welding helmet

will remove 99% of the harmful rays if the proper shade lens is

used.



Other dangers associated with electric arc welding are:

a. -which may be caused by standing in

damp areas, welding without gloves, bare cables, uninsulated

holder, etc.

b. given off in welding process especially

when welding on galvanized or other coated materials.



The operator should be familiar with all safety precautions

and take care to adequately protect himself at all times against

any hazards associated with arc welding by wearing protective

clothing and equipment, working in dry conditions, providing

adequate ventilation and in general using good common sense.



1. Make sure machine is properly grounded.

2. Never permit “live” parts of the electric welder to touch bare

skin or wet clothing.

3. Do not cool electrode holders by emersion in water.

4. Turn off power supply when welder is not in use.

5. Do not stand on wet areas while welding.

6. Wear leather gloves.7. Make sure cable are covered and in good condition.

8. Make certain that electrode holders are properly insulated.



1. Protect eyes and face from flying particles of slag by use of safety glasses or face shield.

2. Wear adequate protective clothing.

3. Always wear leather gloves.

4. Wear high top shoes.

5. Keep collar, shirt pockets, etc buttoned.

6. Do not touch the electrode or metal where welding has takenplace.

7. Handle hot metal with pliers or tongs.

8. Keep electrode stubs properly disposed of.





1. Work only in well-ventilated areas.

2. Use great care when working on metals covered with lead or

zinc.

3. If working in a confined area use respirator or other approvedbreathing devices.



1. Keep shop clean in areas where welding is to be done.

2. Do not weld near combustible materials of any kind.

3. Never weld on covered containers which may have heldcombustible materials without first taking adequate safety

precautions. For example, fill them with water, steam clean or

fill with an inert gas.



1. Be familiar with location and types of fire extinguishers.

2. Report any unsafe conditions that might start a fire.

3. Do not weld near inflammable materials.

4. Do not weld on containers that have held inflammable

materials.

5. Do not weld near electrical fittings or lines.

Compressed Gases



Many welding and cuttingoperations require the use of compressed gases.

To understand these hazards, wemust understand that compressed

gases are stores of potentialenergy.

It takes energy to compress andconfine the gas. That energy isstored until purposely released toperform useful work or until

accidentally released by container failure or other causes.

Compressed Gases



Some compressed gases,acetylene for example, have high

flammability characteristics.

Flammable compressed gases, therefore, have additional stored

energy besides simplecompression-release energy.

Other compressed gases, such asnitrogen, have simple asphyxiatingproperties. Some compressedgases, such as oxygen, can

augment or compound firehazards.

Compressed Gases



Compressed gases are regulated by

many standards. Two primary standards are:

29 CFR 1910 Subpart Q – Welding,Cutting, and Brazing – covers thehandling, storage, and use of compressed gases, such as oxygen-

fuel gas, when they are consumed in the welding process.

29 CFR 1910 Subpart H – Hazardous Materials, 1910.101 -1910.105 – covers the generalrequirements for the handling,storage, and use of compressed

gases other than those consumed in the welding process

General Requirements



In addition to the Occupational

Safety and Health Administration(OSHA) regulations found inSubparts Q and H of 29 CFR 1910

there are other applicableregulations and information.

These include the Department of

Transportation (DOT) regulations,and the Compressed Gas

Association (CGA) pamphlets.

These sources provide therequirements for the generalcategory of compressed gases andcertain specific compressedgases.

General Requirements



An important aspect of theseregulations is the safety of compressed gas storagecontainers.

Specific requirements are made of

employers for the inspection of the compressed gas cylinders.

Visual inspections are required toensure that the cylinders are safe.

The next page will go into moredetail regarding visualexaminations of compressed gasstorage containers and the safety of these containers.

The American Welding Society (AWS) was founded in 1919 as a

multifaceted, nonprofit organization with a goal to advance the

science technology and application of welding and related joining



science, technology and application of welding and related joining

disciplines



Welding Types Procedures Parameters

Documents