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Ag Mechanics, Ag Structures, Ag Powers, and Ag Technology AMI’s

Days 6-10

If you are working on a mechanical/structural project at home/work/or with family

that pertains to one of the above subject areas, you can take pictures of the

project throughout the process and email them to me and I will take this for a

grade.

All others, complete the assignments attached and email the answers to me.

Instructions:

Days 6-10: Define the vocabulary words at the first of the packet and answer the

questions at the end of the packet.

Email all answers or pictures to me

[email protected]

mailto:[email protected]

Applying Shielded Metal ArcWelding (SMAW) Techniques

ANCIENT WELDERS and tools have

been seen depicted on Egyptian

tombs. Welding may be viewed as an

ancient art, but the science of

shielded metal arc welding and other

welding processes is relatively new.

Developments in the welding process

and discoveries in metallurgy have led

to technological wonders and have

changed how we fabricate and build.

Objective:

� Explain the fundamentals and techniques of shielded metal arc welding.

Key Terms:

�

Arc Welding

Arc welding uses heat from an electrical source for the melting or fusion of metals. Weld-

ing is the melting, flowing together, and freezing of metals under controlled conditions. Arc

welding is a process that uses electricity to heat and melt the metal. A weldor is the person

E-unit: Applying Shielded Metal Arc Welding (SMAW) Techniques

Page 1 � www.MyCAERT.com

Copyright © by CAERT, Inc. — Reproduction by subscription only. 090046

alternating current

amperage

arc length

arc welding

conductor

crater

direct current

duty cycle

electricity

electrode

electrons

fillet weld

groove weld

padding

polarity

resistance

shielded metal arc

welding

surface welds

voltage

weaving

weld root

welder

welding

weldor

doing the welding, but a welder is the machine doing the welding. Shielded metal arc

welding is welding in which fusion is produced by heating with an arc between a consumable

stick electrode and the work piece. An electrode is a bare metal rod that is usually coated

with chemical compounds called flux. The flux coatings burn in the intense heat and form a

blanket of smoke and gas that shields the weld puddle from the air.

TERMS

The arc welding process and principles are based around the source of electricity. There-

fore, it is necessary to have a fundamental knowledge of electricity and how it is used for weld-

ing. Electricity is the flow of tiny particles called electrons through a conductor. Electrons

are negatively charged particles, and a conductor is something that allows the flow of elec-

trons. Voltage, meanwhile, is a measure of electrical pressure. Most welders operate on a 220-

volt source. A welder changes or transforms the 220-volt pressure to a much lower pressure at

the electrode, usually between 15 and 25 volts. Amperage is a measure of electrical current

flowing through a circuit and is an indication of the heat being produced. The amount of cur-

rent available is determined by the amperage setting on the welder.

Polarity is the direction in which the current is flowing, while resistance is the opposi-

tion to the flow of current in a circuit. Resistance is what causes the electric energy to be trans-

formed into heat. When electricity is conducted through a conductor, the movement of the

electric energy heats the conductor due to the resistance of the conductor to the flow of elec-

tric current through it. The greater the flow of current through a conductor, the greater the

resistance to it, and the greater the heat generated. Therefore, the higher the amperage setting,

the greater the heat produced. When electrical current alternates or reverses the direction of

electron flow, it is called alternating current (AC). The arc is extinguished every half-cycle

as the current passes through zero, usually at the rate of 120 times per second. Electron flow in

one direction is called direct current (DC), which is either straight polarity (DCSP) or

reverse polarity (DCRP).

HISTORY

The art of welding is ancient, but the science of shielded metal arc welding is relatively new.

In 1801, an English scientist discovered that an electric current would form an arc when forced

across a gap. A French inventor used the carbon arc in 1881. Then in 1887, a Russian improved

on the carbon arc and patented the process. In the same year, another Russian discovered that a

bare metal rod would melt off by the heat of the arc and act as a filler metal in a weld. In 1889,

an American experimented with the metallic arc and received a patent. A bare electrode was

difficult to use and resulted in a weld that was porous, brittle, and not as strong as the base

metal. A Swede found that welds were stronger and easier to make when a chemical coating

was put on the metal electrode in 1910. The coating was called flux because it cleaned the

metal and aided in mixing the filler metal with the base metal. However, it was difficult to

apply. In 1927, mass production methods developed to apply the flux to the bare metal rod.




CLASSIFICATION

Welding machines are classified in several ways. One common way is by the type of output

current produced by the welder: AC, DC, or AC/DC. Another way to classify welders is by

their service. Limited input welders provide satisfactory operation and are fairly inexpensive to

operate. The cost is about $1 per ampere of output. Limited service welders are used where

lower cost is desired because the operation is quite intermittent. Industrial welders have a high

duty cycle, but their price is much higher.

Welders are also classified by power source. An electric motor-driven welder is self-con-

tained and requires three-phase power. Electric power runs the motor, which turns a generator

to produce DC welding current. An internal combustion engine drives a generator that pro-

duces the power for the welder to

run. In contrast, line voltage welders

run on the power supplied by the

power company.

A fourth classification of welding

machines is how long the machine

can operate. A duty cycle is the per-

centage of a 10-minute period in

which a welder can operate at a given

current setting and is another way to

classify welders. A welder with a 60

percent duty cycle can be operated

safely for six minutes of a ten-minute

cycle, repeated indefinitely. The duty

cycle will be shorter if the welder is

used at higher settings. Likewise, if

the welder operates at lower settings,

the cycle will be longer.

When buying a new welder, con-

sider only one made by a well-known

manufacturer and distributed by a

reliable dealer. Check the nameplate

to see if the welder is National Elec-

trical Manufacturers Association

(NEMA) rated and is approved and

listed by Underwriters Laboratories

(UL). Compare prices of welders,

equal capacity, and the kinds of acces-

sories available. Read the guarantee

carefully, and ask questions.




FIGURE 1. Welding machines.

EQUIPMENT AND SUPPLIES

Several other pieces of equipment and supplies are necessary to operate the shield metal arc

welder.

� Two cables: No. 2 gauge

� An electrode holder that grips the electrode during welding and should be completelyinsulated, have a spring-grip release, and jaws that hold rods in 60-, 90-, 120-, and 180-degree positions in relation to the handle

� A ground clamp fastened to the work or to the welding table

� A chipping hammer, with a straight peen and a straight cone with a spiral wire-grip that isnecessary to remove slag from the weld bead

� A wire brush used to clean dirt, rust, and slag from metal

� Pliers needed for handlinghot metal

� Safety glasses or goggles

� Full gauntlet leather gloves

� Upper body protection

� A head shield to offer pro-tection from the rays of theelectric arc, heat, and spatterof the molten metal

� Filter lenses (No. 10 lensmeets applications up to 200amps)

� Electrodes

Electrodes

Electrodes convey electric current from the welding machine into a hot arc between its tip

and the metal being welded. Electrodes are covered with flux. Because there are two classifica-

tions of electrodes, the American Welding Society (AWS) and the American Society for Test-

ing Materials (ASTM) have set up standard numerical classifications for most electrodes. Every

electrode has been assigned a specific symbol, such as E7014. The “E” indicates the electrode is

used for electric welding. The first two digits of a four-digit number indicate tensile strength

in thousands of pounds per square inch. For instance, an E7014 electrode produces a weld

with 70,000 psi of tensile strength, and an E6011 electrode produces a weld with 60,000 psi of

tensile strength. If the number has five digits, the first three digits indicate tensile strength.

The next-to-last digit indicates welding position for which the electrode is recommended. The

last digit indicates the operating characteristics of the electrode. NEMA has adopted color

marking for some classes.




Welding machineBead

Electrode

Electrode holder

Arc

Ground clamp

Electrode cable

Groundcable

FIGURE 2. Components of an ARC welding system.

PREPARATION

One of the most important and most often neglected parts of the welding job is preparation

of the metal for welding. The metal must be free of dirt, grease, rust, paint, and other impuri-

ties that may combine with a molten weld bead and cause it to be weakened. Metal should be

cleaned by grinding, brushing, filing, or cutting before welding occurs.

COMMON WELDS

Preparing the correct type of joint for each kind of metal is crucial for securing strong

welded structures. The basic types of joints are the butt, lap, tee, corner, and edge. These joints

may be applied to the different types of welds: fillet, groove, plug, slot, and surface. A tee weld

is a type of fillet weld.

� The fillet weld has twosurfaces at right angles, andthe bead is triangular inshape.

� The groove weld is a weldmade in a groove betweenthe two pieces of metal to bejoined.

� The plug and slot welds areused to join pieces that over-lap. The welds are placed inplug or slot holes. Thesetypes of welds commonlytake the place of rivets inwelded structures.




BROADENING AWARENESS…

AMAZING ASPECTS: Flux

The flux coating on electrodes provides several important functions. Flux protects the molten

metal from the atmosphere. The flux covering burns in the intense heat of the arc, forming a

blanket or shield of gas around the bead. Air contains oxygen and nitrogen which would combine

with the metal, making it brittle and weak.

In addition, flux mixes with the weld metal, floating the impurities to the top in the form of

slag. Slag covers the bead to protect it from the air and slows the rate of solidification and cool-

ing. Flux also stabilizes the arc. After the arc is started, current flows across the gap between the

end of the electrode and the work. Flux is designed to yield a stable arc with low spatter and to

reduce fuming.

Butt Joint

Corner Joint

Edge Joint

Lap JointTee (Fillet) Joint

FIGURE 3. Common welds.

� Surface welds are beads deposited on a metal surface for the purpose of building upthe base metal.

Butt Joint

The square butt joint is used

on metal sections no thicker than3/16 inch. This joint is strong in

tension loads, but it is not good

for repeated loads and impact

forces. The single V butt joint is

often used on plate steel 3/8 inch

to ¾ inch in thickness. The joint

is strong in loads with tension

forces but is weak in loads that

bend at the weld root, which is

the bottom of the weld groove

opposite the weld face. The sin-

gle-bevel butt joint is used on

metals from 1/8 inch to ½ inch in

thickness, and the bevel is 45

degrees. The double V butt joint

is excellent for all load conditions

and is often used on metal sec-

tions of more than ¾ inch in

thickness.

Lap Joint

The lap joint is a type of fillet weld. Its strength depends on the size of weld bead. The sin-

gle lap joint is one of the stronger weld joints. It is used on metal up to ½ inch in thickness.

The double lap joint is almost as strong as the base metal.

Tee Joint

The tee joint is a fillet weld and can be used on metals up to ½ inch in thickness. It can

withstand strong longitudinal shear forces. The tee joint can be square, beveled, or double

beveled.

Corner Joint

A corner joint can be flush, half-open, or full-open. The flush corner joint is primarily used

on sheet metal. The half-open joint can be used on metals heavier than sheet metal and for

joints that will not have large fatigue or impact loads. This joint can be welded from one side.




3/16" to 3/8"

1/16" to 1/8"

Square butt joint with a 1/16" to 1/8" root gap.

Single-V butt joint.

Single-bevel butt joint.

Double-V butt joint.

FIGURE 4. Common butt joints used in welding.

Yet the full-open corner joint is used for metals that will carry heavy loads, so it must be able

to withstand large fatigue and impact loads. It can be welded on both sides.

Edge Joint

An edge joint is used for metals less than ¼ inch in thickness and can only sustain light load

applications.

PROCEDURES AND TECHNIQUES

Good welds can be attributed to correct selection and manipulation of the electrode and

welding current. The weldor must use proper amperage, maintain arc length, angle and speed,

and perform proper welding techniques. Making good flat welds on steel is not difficult. The

welding process requires attention, practice, and patience.

Proper Amperage

The proper amperage setting for any welding job is necessary for adequate penetration with

minimum spatter. Correct amperage can be identified somewhat by sound. When the amper-

age is correct, a sharp crackling sound can be heard. A humming sound will indicate an amper-

age setting that is too low. As a result, the deposited electrode will pile up, leaving a narrow,




Square

Single Lap

Double Lap

Single Bevel

TYPES OF FILLET WELDS

LAP JOINTS

CORNER AND EDGE JOINTS

Edge Joint

Full-Flush

Corner Joint

Flush

Corner Joint

Half-Open

Corner Joint

Double Bevel

FIGURE 5. Common joints used in welding.

high bead that has poor penetration and little strength. A popping sound will indicate too high

of an amperage setting, and the bead will be flat with excessive spatter. The electrode will

become red hot, and the metal along the edge of the bead will be undercut. The correct amp

setting depends on the thickness of the base metal and the diameter of the electrode.

Arc Length, Angle, and Speed

Learning to maintain the correct arc length for the electrode you are using is necessary to be

successful. Arc length is the distance from the tip of the bare end of the electrode to the base

metal. Arc length is equal to the diameter of the bare end of the electrode.

The correct angle of the electrode will depend on the type of weld to be completed. Hold

the electrode at a 90-degree angle to the work as viewed from the end of the two plates being

joined and 5 to 15 degrees in the direction of travel. The correct speed of travel affects the

amount of electrode deposited and the uniformity of the bead. It should produce a bead that is

1.5 to 2 times the diameter of the bare end of the electrode.

Striking the Arc and Welding

Following proper procedures when preparing to weld and striking the arc will develop con-

fidence in your abilities.

1. Prepare the work area so everything is ready and convenient before you start.

2. Make a final check to see that flammable materials are out of the way and unnecessary

tools are not lying around.

3. Be sure the machine is turned off.

4. Set the machine to the desired amperage.

5. Insert the bare end of the

electrode in the electrode

holder, and hold the end

of the electrode about 1

inch above the metal at the

point where the weld is to

be started.

6. Turn on the welder.

7. Lower the helmet over

your eyes, bring the elec-

trode in contact with the

work, and withdraw it

slightly. Current jumps

the small gap and creates

the electric arc. The




Core

Coating Projection

Arc Length

Slag

Electrode

Gaseous Shield

Molten Pool

Direction of Travel

Base Metal

Penetration

Crater

Fusion Metal

Flame

15° to 30°

FIGURE 6. Shielded metal ARC welding.

moment the arc is struck, the concentration of intense heat, estimated between 6000°

and 9000°F, melts the base metal and the end of the electrode and forms a molten metal

pool called a crater.

8. There are two methods used in starting the arc. A striking movement is similar to strik-

ing a match. A tapping movement involves the electrode being quickly tapped on the

surface of the metal to prevent it from sticking to the base metal. If the electrode is not

instantly pulled away, it will fuse with the base metal and stick. If the electrode is pulled

too far away, the arc will be extinguished.

9. Raise the tip of the electrode to about 3/16 inch above the base metal to form a long arc

that is held for a three count to preheat the base metal.

10. Lower the electrode to the correct arc length.

Movements

To make a wider bead or when doing out-of-position welding, use a motion of weaving or

oscillating movements. Weaving is running a bead with a sideways or oscillating motion. It is

a process used when covering a wide area with weld metal; it can also be used to maintain a

large molten weld crater. Pad-

ding is the process of building

up several layers of weld deposit

by running overlapping passes.

Padding is used to rebuild worn

pieces by building up the piece to

an oversized condition and

grinding or machining it to the

correct size. These movements

usually require more time, and

the beads are shorter per inch of

electrode used.




Whipping Motion

Back and Forth, or “N” Motion

Semicircular Motion

“U”-Shaped Motion

“V”-Shaped Motion

Circular Motion

FIGURE 7. Electrode movement.

FURTHER EXPLORATION…ONLINE CONNECTION: Welding Safety

Safety is extremely important with hot metal. Protective clothing should be worn always.

Attention to safe handling of hot metal is critical. Once you have read through the welding safety

practices and tips, develop an outline of how you would promote welding safety in your school

shop. Develop a poster to help weldors avoid accidents. Use the following link to provide you

with suggestions:

http://www.lincolnelectric.com/

Positions

There are four positions used

when welding: flat, horizontal,

vertical, and overhead. The flat

position produces the strongest

welds.

Controlling Distortion

Controlling distortion, warp-

ing, and cracking are major con-

cerns when welding because of

forces that cause their shape or

position to change. During the

welding process, the arc heats the

area being welded, causing it to

become larger or to expand. As

heat is removed, the surrounding

metal and air causes a cooling

effect upon the heated area, which

results in the metal becoming

smaller or contracting. The laws

of expansion and contraction

cannot be avoided.

Several methods can be used to control distortion. The first method is to use a tack weld,

which is a short bead placed at the edge of the end to which you are welding. The length of the

tack weld should be twice the thickness of the base metal. Avoid over-welding by using as little

weld metal as possible for the necessary strength. Another common method is to practice

intermittent welding in which short beads are run and spaces are skipped between them. Run

short passes and allow them to cool before running the next pass. You can also use the back

step method to control distortion. It can be used when a short pass is started ahead and is run

back into the previous weld.

Other common methods to help control distortion are the following examples:

� Balance the contraction of one bead by the contraction of another.

� Carefully hammer or peen a weld deposit to stretch the weld and to make up for contrac-tion due to cooling.

� Clamp material in a jig or to other rigid support during welding and cooling.

� Preheat the materials being welded. Preheating makes welding easier and lessens the pos-sibility of cracks.




Horizontal

Vertical Up

Vertical Down

Overhead

Flat

FIGURE 8. Basic welding positions.

SAFETY PRACTICES

Arc welding creates many dangers to the eyes and body. The brightest of the light can cause

severe burns and injury to the eyes and skin. Read the following suggested practices and tips to

minimize and/or eliminate shop accidents when arc welding.

Protective Wear

Always wear a welding helmet with an approved lens that is in good condition. A welding

helmet protects from the rays of the electric arc as well as the heat and spatter of the molten

metal. Use only filter lenses that are clearly labeled with standard shade numbers. Be sure they

meet the specifications of the welding you are performing.

Upper body protection is necessary to protect against rays, heat, spatter, and slag while

welding. Wear leather or special fabric gloves at all times to protect from hot electrodes, parti-

cles of spatter and slag, and the metal being welded. Wear high-top shoes to protect your feet

and ankles from burns caused by weld spatter. Do not wear clothing with turned up cuffs, and

keep your collar and pockets buttoned. Oily, greasy, and/or ragged clothing should not be

worn. If leather clothing is not available, wear wool clothing rather than cotton. Wool does not

ignite as readily, and it provides better protection from heat.

Equipment and Material Safety

Welding cables should be inspected for broken insulation and frayed conductors. Also, elec-

trode holders and ground clamps should be checked for positive connections before beginning

to weld. Loose connections and grounds may prove to be dangerous. In addition, the work area

should be dry. If floors are damp, protective shoes should be worn (e.g., rubber-soled shoes).

All combustible materials should be cleared away from the welding area before beginning to

weld. It is important to keep matches, lighters, papers, and cellophane wrappers out of pockets

as these items ignite quickly and/or may explode. It is possible for flying sparks from the spat-

ter to reach several feet from the welding operation. Sparks could ignite combustible materials,

so the welding area should be cleared of rags, straw, paper, shavings, and other combustible

items before starting to weld.

An exhaust system should be turned on before you begin. Welding fumes can spread to all

parts of the shop and may result in injuries if inhaled. Special measures need to be taken to

avoid noxious fumes that occur when welding or cutting metals containing zinc. Inhaling zinc

fumes will cause you to feel ill for several hours after welding.

Work Environment Safety

Protect other workers by using a welding screen to enclose your area. Warn people standing

nearby, by saying “cover,” to cover their eyes when you are ready to strike an arc. You should

never look directly at the arc without protecting your eyes. The rays can penetrate through

closed eyelids if you are welding at close range. Do not wear contact lenses while welding or




around a welder. Do not chip slag from a weld unless your eyes and those of others near you

are protected by safety glasses.

A weldor should be on alert for fires. The operator’s helmet is lowered, so clothing may

catch fire without being noticed. In case of a clothing fire, strip off the article, if possible. Wrap

yourself in a fire blanket, or improvise with a coat or a piece of canvas. If there is nothing at

hand to wrap in, drop to the floor and roll slowly. In case of eye or skin burns, get first-aid

treatment. All burns and injuries should be reported immediately to the instructor.

Hot metal should be handled with tongs or pliers to prevent burning your hands or gloves.

Hot metal needs to be placed where no one will come in contact with it. An important habit to

develop is feeling all of the metal cautiously before picking it up. Hot metal should not be left

where it may be picked up or stepped on.

The welder should be disconnected when repairing or adjusting it. At the end of the work

day, welders and equipment should be unplugged, and all equipment should be put away. Pro-

tect fuel tanks and fuel lines with wet sheet asbestos when welding near motors or power

units. Clean accumulations of dry trash, husks, lint, and chaff off of farm machinery before

welding. The paint on machinery may start to burn from the heat of welding.

Summary:

� Shielded metal arc welding is welding in which fusion is produced by heating withan arc between a consumable stick electrode and the work piece. Arc welding useselectricity to generate heat. Common knowledge of basic electrical functions is nec-essary.

Welding machines are classified in several ways. One common way is by the type ofoutput current produced: AC, DC, or AC/DC. They can also be classified by theirservice or by their power source. Another classification is how long the machine canoperate.

Arc welding requires several other pieces of equipment and supplies. Preparation isone of the most important parts. Part of preparation is expressing the knowledge ofcommon welds and joints. Once preparation is successfully completed, proper pro-cedures and techniques need to be used and followed. Arc welding poses great dan-gers to eyes and skin, so it is important to wear a proper helmet, protective clothing.Also, welders should follow safety measures and should be attentive to others.

Checking Your Knowledge:

� 1. What is an advantage of using shielded metal arc welding?

2. How are welding machines classified?

3. What equipment is needed in order to operate the shield metal arc welder?




4. What do the digits on an electrode indicate?

5. How can distortion, warping, and cracking be controlled?

Expanding Your Knowledge:

� How do you store electrodes? Can electrodes just sit out on the work station untilneeded? Can moisture or humidity cause damage to electrodes? Research theproper storage practices for electrodes. Use the following article for assistance:http://www.keenovens.com/articles/store-rods.htm

Web Links:

� Arc Welding Safety

http://nasdonline.org/document/1087/d000873/arc-welding-safety.html

Welding Electrodes

http://www.metalwebnews.com/howto/weldrod.html

Guidelines for Shielded Metal Arc Welding

http://www.millerwelds.com/pdf/guidelines_smaw.pdf

Agricultural Career Profiles

http://www.mycaert.com/career-profiles




Applying Fuel Gas Welding (FGW)Processes and Techniques

UNDER A SPECIFIC HEAT PROCESS, two pieces of material

can be fused or joined together. This is the principal

function of welding. Metal is commonly used in the

welding process. However, other materials, such as

plastics, can be welded. Materials are fused together

once a melting point is achieved. The bond is completed

as the materials cool. The bond will be as strong as the

original material if the process is accomplished properly.

Objective:

� Explain the fundamentals and techniques of

fuel gas welding.

Key Terms:

�

Understanding Gas Welding

Several forms of gases will burn. Acetylene and propane are commonly used for heating,

cutting, and welding metals. These gases are compressed and are stored in cylinders. The fun-

damentals and techniques available for fuel gas welding allow for using the gases safely. The

process is built upon two fundamental principles. Acetylene burned with oxygen produces a

flame so intensely hot that it can be used to melt and fuse metals. A stream of oxygen directed

against a piece of iron or steel, which has been heated to its kindling temperature, causes the

metal to burn away so it can be used to cut or shape the metal as desired.

FUEL GASES

Acetylene, C2, H2, is a fuel gas made of carbon and hydrogen that is produced from the

chemical reaction between calcium carbide and water. Acetylene is colorless, but it has a dis-

E-unit: Applying Fuel Gas Welding (FGW) Processes and Techniques



acetylene

blowpipe

carburizing flame

flash arrestors

flashback

neutral flame

oxidizing flame

oxygen

regulator

tinct odor. The flame produced by acetylene can generate a theoretical temperature of 6300°F

and a measurable temperature of 5800°F. It is stored in a free state under pressure greater than

15 psi.

Methylacetylene propadiene (MAPP) is a stabilized methylacetylene. It combines the high

energy characteristics of acetylene with the handling and storage features of liquefied petro-

leum gases. MAPP gas is more stable than acetylene, making it safer. C3H4 has a flame tem-

perature of 5300°F. The bushy flame makes welding difficult with MAPP gas.

Propane, C3H8, has a maximum flame temperature of 5300°F. The volume of oxygen

required for that temperature produces an oxidizing flame unacceptable for iron and steel

welding.

Oxygen

The oxygen used in the oxyacetylene process is manufactured from liquid air and is stored

in hollow steel cylinders. Oxygen is a nonflammable, tasteless, colorless, and odorless gas that

is slightly heavier than air. When combined with other elements, it will support combustion.

Commercial oxygen is supplied to users in seamless steel cylinders charged with oxygen to a

pressure of about 2200 psi at 70°F. The pressure will increase and decrease as the temperature

changes. The oxygen cylinder has a valve made of tobin bronze. Since bronze is soft, protec-

tion must be provided to prevent it from being broken or knocked off.

EQUIPMENT AND SUPPLIES

Several pieces of equipment are used for fuel gas welding. Cylinder tanks, regulators, hoses,

and an appropriate torch provide a basic framework. The equipment should be provided in

good condition and from a reliable dealer who guarantees service on all equipment and

supplies.




BROADENING AWARENESS…

AMAZING ASPECTS: Be Safe

Because of the intense heat and other opportunities for accidents, safety is of extreme

importance in fuel gas welding. This form of welding can cause metal to spark, drop, or fly. As a

result, serious injuries can occur. The following are some suggested practices for proper protec-

tive clothing.

• Wear goggles or a face shield approved for fuel gas welding.

• Wear leather welding gloves when welding or cutting. Do not touch hot metal with gloves.

• Wear protective clothing, such as material that will resist flames and heat.

• Wear leather shoes that will resist burns and provide protection from heavy pieces of

metal.

Oxygen and acetylene fittings are

not interchangeable. Oxygen fittings

have right-handed threads, while

acetylene fittings have left-handed

threads or a smaller size right-hand

connection. A regulator is attached

to each of the tank valves. A regula-

tor is a device used to vary line pres-

sure on a tank. Each regulator has a

diaphragm adjusting screw to vary

the line pressure and two gauges:

one showing cylinder pressure and

one showing line pressure.

The hoses used are colored: one

green and one red. The green hose is

used for oxygen and has fittings with

right-handed threads. The red hose

is used for the fuel gas and has left-

handed fittings. The hoses connect

the blowpipe to the regulators. The

blowpipe is a mixing chamber. The two gases are mixed and delivered to the tip ready to

burn. The blowpipe has a valve to control the oxygen and a valve to control the acetylene.

A variety of tips are attached to the blowpipe for different tasks. A welding tip is used for

welding pieces together, and a cutting attachment with a tip is used to cut metal. Special tips

are available to perform other tasks, such as heating.

TABLE 1. Other Pieces of Fuel Gas Welding Equipment

Type of Equipment Purpose

Welding goggles or face

shields

They filter out ultraviolet and infrared rays to protect the operator’s

eyes. A No. 4 lens should be used.

Friction lighter It is used to light the blowpipe.

Gauntlet gloves They are worn when welding or cutting to protect skin.

Cart Cylinders should be chained in an upright position when used and

stored.

Safety caps They should be positioned on top of the cylinders and should not be

removed until the cylinders are secured.

Flash arrestors are

devices that will extinguish

any flame that attempts to

go through them due to a

flashback.

They should be mounted on the oxygen and acetylene lines at the

regulators. A flashback is a fire inside the blowpipe. When a

flashback occurs in an oxyacetylene unit, flame physically travels up

the welding tip and through one or both of the hoses to the

regulator.




Oxygen pressuregauges

Oxygen cylindershut-off valve

Acetylene pressuregauges

Acetylene cylindershut-off valve

Cart

Chain tosecure cylinders

Acetylene cylinder

Oxygen cylinder

Acetylene pressureregulator

Oxygen pressureregulator

Oxygen hose

Acetylene hose

FIGURE 1. Major parts of an oxyacetylene welding and cutting outfit.

SET-UP

Following proper procedures when setting-up the fuel gas welding equipment will insure

that there are no gas leaks. Therefore, accidents can be minimized and, hopefully, avoided.

General procedures are as follows:

1. Place the cylinders in a cart. Fasten them together with a chain, or fasten the cylinders

in some other manner to prevent them from being tipped over during use or storage. If

an acetylene cylinder is tipped on its side, it should be set upright for at least 30 minutes

before it is used.

2. All oxygen and some acetylene cylinders have iron caps to protect the cylinder valves.

Remove the caps. Stand to one side so you are not directly in line with the tank valves.

“Crack” the cylinder valves slightly. Then close them quickly, which will blow out all

dust and other foreign matter.

3. Connect the acetylene regulator to the acetylene cylinder and the oxygen regulator to

the oxygen tank. It should not be possible to interchange the regulators. To avoid con-

fusion, the regulator with the larger numbers belongs on the oxygen tank.

4. Connect one end of the green hose to the outlet connection on the oxygen regulator

and the other end to the oxygen connection on the blowpipe. Be sure the flash arrestor

is attached to the regulator and the hose is attached to the arrestor. If the unit does not

have a built-in check valve, be sure one is put between the hose and the blowpipe.

5. Connect one end of the red hose to the outlet connection on the acetylene regulator

and the other end to the acetylene connection on the blowpipe. Repeat the flash

arrestor step in the same manner as conducted for the oxygen regulator.

6. Close both regulator valves by turning the regulator diaphragm screw counterclockwise

until the screw is loose. Always close the regulator valves before opening the cylinder

valves to prevent the tank pressure from damaging the regulator.

7. While standing to one side, not directly in front of the regulator, open the oxygen cylin-

der valve slowly. Wait until the cylinder pressure has registered on the high-pressure

gauge before completely opening the valve. The oxygen tank valve is double seated, and

it should be opened completely to prevent loss of the high-pressure oxygen around the

tank valve.

8. Standing to one side, not directly in front of the regulator, open the acetylene valve

slowly. This valve should never be opened more than one turn so it can be shut off

quickly. Always leave the T-wrench on the valve while you are working in case the fuel

gas needs to be shut off quickly.

9. Open the oxygen valve on the blowpipe about one-eighth of a turn. Turn the screw on

the oxygen regulator clockwise until the desired pressure is reached on the oxygen low-

pressure gauge. Close the oxygen valve on the blowpipe.




10. Open the acetylene valve on the blowpipe about one-eighth of a turn. Turn the screw

on the acetylene regulator clockwise until the desired pressure is reached on the acety-

lene low-pressure gauge. Close the acetylene valve on the blowpipe.

Testing for Leaks

A good shop maintenance practice should include testing for leaks on fuel gas welding

equipment. This practice should be conducted when the equipment is first set up, when cylin-

ders are changed, and when an odor is present (when the equipment is not being used).

Test for leakage by applying soapy water around the valves and connections. If a bubble

appears at a valve or a connection, a leak has been detected. It should be corrected before using

the equipment. It is important to use grease-free soap.

OPERATING

Fuel gas welding requires precise settings on gauges and valves. These settings assist the

operator in achieving proper lighting of the torch and a neutral flame. The correct lighting and

shutting down procedures should be followed at all times.

TABLE 2. Lighting Procedure for Welding or Cutting Torch

Correct Lighting Procedure

1. Place goggles or safety glasses and face shield on your forehead.

2. Be sure regulator adjusting screws are turned out. The screw should turn freely.

3. Standing to one side, not directly in front of the regulator, open the oxygen cylinder valve

slowly. Then open it all the way. Set the regulator at the correct working pressure. Open the

oxygen blowpipe valve, and fine tune the operating pressure. Close the oxygen blowpipe valve.

4. Standing to one side, not directly in front of the regulator, open the acetylene cylinder valve

slowly. Only open the tank valve ½ to ¾ of a turn. Set the regulator at the correct working

pressure. Open the acetylene blowpipe valve, and fine tune the operating pressure. Close the

acetylene blowpipe valve.

(Continued)




Acetylenehose

connection

Oxygenhose

connection

Acetylenecontrol valve

Oxygen andacetylene mixture

Oxygencontrol valve

Oxygen

Tip

Tip connectionto mixer

Torch body

Acetylene Mixer

FIGURE 2. Blowpipe detail.

TABLE 2 (Continued)

5. Put on gloves, and lower the goggles or face shield over your eyes.

6. With the friction lighter in your left hand at the tip of the blowpipe and the blowpipe in your

right hand, open the acetylene blowpipe valve, with your right thumb and forefinger, one-

eighth to one-quarter turn. Strike the friction lighter, and adjust the acetylene level.

7. Adjust the acetylene by opening the blowpipe valve until the flame leaves the tip about ¼

inch. Close the valve very slowly until the flame is pulled back to the end of the tip. Open the

valve slowly again, stopping just before the flame leaves the tip. This is the proper adjustment

for most welding.

8. Open the oxygen blowpipe valve, and set the desired flame type.

Flames

There are three types of oxyacetylene

welding flames: neutral, oxidizing, and

carburizing. The neutral flame is usually

used for welding. A neutral flame is a

flame that will produce a smooth, shiny

bead of the best quality. Meanwhile, the

oxidizing flame is a flame caused by

an excessive amount of oxygen, which

produces a short white inner cone and a

short envelope flame. An oxidizing

flame will produce sparks that shower

the weld area with droplets of metal and

slag, leaving the weld zone weak and

porous. In contrast, the carburizing

flame is a flame caused by an excessive

amount of acetylene and has a long, blu-

ish outer flame. A carburizing flame will

cause the puddle to foam and boil, leav-

ing a brittle, porous, and scaly weld area.

The carburizing flame is used for hard-

surfacing.

TECHNIQUES

The techniques of fuel gas welding include setting the proper flame, preparing the pieces to

be welded, knowing the common weld types, holding and using the blowpipe and rod, and

completing the different weld types by using braze or fusion welding. Braze welding (formerly

referred to as bronze welding) referred to the use of a bronze filler rod. In braze welding, as




Carburizing Flame

Oxidizing Flame

Neutral Flame

FIGURE 3. Flames.

the melting point of the filler rod is achieved, the metal surfaces are joined together. Fusion

welding allows for the base metal to be melted and mixed together; it forms a joining. Fusion

welding can be completed with or without a filler rod.

Preparing the Metal

Metal should be cleaned before any form of welding is conducted. The cleaning procedure

allows for the removal of oxides or any other form of impurities. Using mechanical means

(e.g., a wire brush, grinder, file,

sander, or steel wool) allows for

the removal of oxides, such as

rust. A chemical could be used to

remove any remaining impurities.

The edges of metals over 1/8

inch should be cut to form a V,

with approximately a 45-degree

angle to permit complete fusion

of the pieces. If the pieces are 3/8

inch or more in thickness, it is

usually desirable to cut a V on the

top and bottom sides of the two

pieces of metal being welded. The

pieces to be welded should be




TABLE 3. Shutting Off Procedure for Welding or Cutting Torch

Correct Shut-Down Procedure

1. Close the acetylene blowpipe valve.

2. Close the oxygen blowpipe valve.

3. Close the acetylene tank valve.

4. Close the oxygen tank valve.

5. Open the acetylene blowpipe valve to drain the hose and to release all pressure from the

hose and regulator.

6. Turn out the pressure-adjusting screw on the acetylene pressure regulator by turning it

counterclockwise.

7. Close the acetylene blowpipe valve.

8. Open the oxygen blowpipe valve to drain the hose and to release all pressure from the hose

and regulator.

9. Turn out the pressure adjusting screw on the oxygen pressure regulator by turning it

counterclockwise.

10. Close the oxygen blowpipe valve.

11. Wrap up the hoses, and put the welding accessories in their proper place.

FIGURE 4. Forming a V in preparation of fuel gas welding.

placed about 1/16 inch apart to provide for the expansion and contraction of the metals and to

permit the weld to penetrate deeply, through the bottom, if possible.

Types of Welds

The two most common weld types are the butt weld and the fillet weld. Types of welded

joints frequently used are the butt joint, tee joint, corner joint, lap joint, and edge joint. The

common welding positions are downhand, horizontal, vertical, and overhead. The downhand

weld is used most frequently and is the easiest weld to make.

Position of Equipment

The blowpipe is usually held in the same say as a hammer or a fishing pole when the opera-

tor is welding while standing. It is held in the same manner as a pencil when the operator is

welding while seated. The operator should hold the blowpipe in a comfortable way.

The recommended blowpipe position allows for the tip to be inclined at a 45-degree angle

to the welded surface point directly along the line of the weld. Hold the tip so the inner cone

of the flame is about 1/8 to 1/16 inch above the surface of the metal.

Before lighting the blowpipe, practice holding it and moving it in the motion used in weld-

ing. The blowpipe may be moved in a straight line, in a zigzag, or in a circular motion. The cir-

cular motion is most frequently used. Move the blowpipe in a series of connected ovals in a

left-to-right direction and along the line of welding. Advance each successive oval about 1/16

inch. Make the oval about 1/4 inch wide and 5/16 inch long.




GROOVE JOINTS

FILLET JOINTS

Flat position

Horizontal position

Vertical position

Horizontal position

Vertical position

Overhead position

Overhead position

Flat position

Axis ofweld

Axisof

weld

Axisof

weld

Axisof

weldAxisof

weld

Axisof

weld

Axis ofweld

Axis of weld

FIGURE 5. Welding joints and positions.

Learning How to Form a Molten Puddle

To weld with oxyacetylene, learn how to melt the base metal and how to control the molten

puddle. Start the flame at the edge of the steel piece, and form a molten puddle about 1/4 inch

in diameter and about 1/8 inch from the edge of the piece of steel. The width of the puddle is

about twice the thickness of the metal.

After learning to control the molten puddle, learn how to make a bead. A welding rod is

added to the process. The rod melts as it is added to the molten metal. As it progresses across

the metal, it is called “making a bead.”

If you are right-handed, hold the welding rod in your left hand at a 45-degree angle so the

end of the rod will be within the outer envelope of the flame. Move the blowpipe in a circular

motion, and dip the rod into the center of the puddle each time the flame reaches the back of

the circle. Raise the rod out of the puddle slightly as the flame is passed toward the front to the

puddle, thus synchronizing the motions of the flame and the rod.

Maintain a molten puddle about 1/4 inch in diameter, and move the rod and blowpipe

slowly, straight ahead about 1/16 with each oval motion of the blowpipe. Raise the rod out of the

flame’s way to permit the flame to heat the metal ahead of the bead. Lower the rod so the

flame will melt it, causing the welding rod to flow into the molten puddle. The end of the

welding rod should touch the puddle on the downward stroke. The rod should not dip into

the puddle.

Fusion Welding

A fusion weld is the next step

after learning to make a bead.

Two pieces of metal are welded

together using a filler rod. Select

two pieces to be welded, and

space them so the edges of the

metal are 1/16 inch apart at one end

and approximately 1/8 inch apart at

the other. Make a tack weld at

each end of the pieces to hold

them together. Follow the same

procedure and motion used in

making a bead.

Braze Welding

Braze welding has some advantages over fusion welding. Brazing and soldering are con-

ducted at low temperatures, can be completed faster, show little damage to parts, can join dif-

ferent metals, and allow for easy disassembly.

Heat the base metal to a salmon red color. The bronze rod should not remain in the inner

cone of the flame. In addition, the inner cone of the flame should not stay in one spot of the




Direction of Travel

ConeFiller Rod

Welding Torch Tip

Acetylene Feather

Molten Weld Metal

Solidified

Weld Metal

FIGURE 6. Fuel gas welding structure.

molten bronze because the intense

heat will burn the bronze. The

same technique and movement

used with fusion welding should

be followed.

SAFETY PRACTICES

The following safety practices

should be conducted at all times

when working with fuel gas weld-

ing.

1. To prevent oxygen and fuel

cylinders from being tipped

over accidentally, fasten

them securely in an upright

position with a chain or a

similar device before

removing the safety cap.

2. Keep oil and grease away from oxygen cylinders and equipment.

3. Check equipment connections periodically for any leaks by using the soapy water

method.

4. Check regulator gauge operation pressures carefully, and follow recommendations.

5. Clear the area of all combustible materials before lighting the torch.

6. Cover your eyes with welding goggles or a colored face shield, and put on gauntlet

welding gloves before lighting the torch. Wear clothes suitable for the work being done.

7. Stand to one side, not directly in front of the regulator, when opening the cylinder

valve.

8. Do not open the blowpipe valves more than ½ turn when lighting the torch.

9. Never use a match to light the torch.

10. Always use a spark igniter or a friction lighter to light a welding torch. When lighting a

torch, keep the tip facing downward and away from you.

11. Light the acetylene first, and add oxygen to the flame. Make no attempt to relight a

torch from hot metal.

12. Be sure that other workers are in the clear before relighting a torch.




The correct position of a blowpipe and rod

when the rod is lowered.

FIGURE 7. Fuel gas welding position.

13. Do not walk with a lighted torch or lay down a lighted torch. Before you light the

torch, get into position for welding or cutting, and remove all obstacles between you

and the shut-off controls.

14. Before opening a cylinder valve, be sure the regulator valve is closed by turning it coun-

terclockwise until it is loose.

15. If a flashback should occur, turn off the torch immediately, close the cylinder valves,

and notify your instructor. A flashback has occurred when the flame disappears and

burns back inside of your equipment. There is a hissing, squealing sound. Smoke may

come out the torch tip, and the handle may become hot. If the torch is not turned off

promptly, fire may reach the hoses or the cylinder. Do not relight after a flashback until

the equipment has been inspected closely. The equipment may require repairs.

16. Never open the acetylene cylinder valve more than ½ to ¾ of a turn. Leave the T-han-

dle wrench in position at all times while welding. You should be able to turn off the

acetylene cylinder valve promptly in case of a fire.

17. Never do any welding on containers that may have held flammable substances.

18. When welding or cutting zinc or galvanized metals, make a special effort to avoid

breathing the fumes because they can make you feel ill.

19. Never use acetylene at a pressure greater than 15 psi. Follow the manufacturer’s recom-

mendations for the correct operating pressures for the metal being welded and for the

tip size being used.

20. Do not smoke or allow anyone else to smoke near the oxy-fuel gas welder.

21. Keep the flame and heat away from the cylinder, hoses, and people. Be alert for fires at

all times. Use the proper fire extinguisher or a fire blanket if necessary.

22. For most oxyacetylene welding, you will need a lens with shade No. 5.

23. Cylinders should not be stored near open fires, furnaces, or other heating devices or in

direct rays of the sun.

24. Keep cylinders away from electric wiring and away from the danger of striking an arc

on them with an electric welder.

25. Oxygen cylinders are equipped with a double seating valve. Open the valve all the way

to prevent oxygen from escaping around the valve stem.

26. Wear welding gloves to protect the hands against burns, sparks, and molten metal.

27. Wear flame-resistant clothing.

28. Low shoes are not recommended because sparks or slag may get into them.

29. Make certain that reverse flow-check valves and flash arrestors are installed on the oxy-

gen and acetylene lines.




30. Be sure the cylinder valves are closed and the pressure is relieved from the hoses before

you leave the work area.

31. Remove regulators and replace protective caps before transporting cylinders.

32. Store oxygen cylinders away from fuel gas cylinders.

33. Never use oxygen as compressed air to dust clothing because clothing saturated with

pure oxygen is highly combustible.

34. Handle hot metal with pliers or tongs. Do not leave hot metal on the welding table

because unsuspecting people may touch it and may be burned.

Summary:

� Oxyacetylene welding is a process by which two pieces of metal are joined. Acety-lene and propane are commonly used fuel gases. Oxygen is used to support com-bustion. Cylinders, regulators, hoses, a blowpipe, and tips are common equipmentused in the set-up of fuel gas welding.

Safety is extremely important during fuel gas welding. Materials used can damageeyes, skin, hands, and feet. Therefore, protective clothing and proper proceduresmust be followed and conducted during shop exercises.

Following proper procedures when setting up the fuel gas welding equipmentshould help avoid gas leaks and minimize accidents. A common way to test for leaksis to use soapy water around valves and connections. If a bubble appears, a leak hasbeen detected.

Using proper techniques (e.g., achieving a desired neutral flame) will ensure qualitywelding. Other techniques include cleaning metal surfaces, preparing edges, identi-fying weld types, and positioning of equipment. The final steps in fuel gas weldingare learning how to control the molten puddle and making a bead.

Checking Your Knowledge:

� 1. What are three advantages of acetylene?

2. What are the key safety factors when setting up cylinders?

3. What is a flashback, and what safety practices should be followed immediately?

4. What are the procedures for fuel gas welding equipment set-up?

5. What are the differences between neutral, oxidizing, and carburizing flames?




Expanding Your Knowledge:

� Practice fuel gas welding (FGW) processes and techniques. First, view the followingvideo: http://www.youtube.com/watch?v=YjwsKjqWiS8. Practice forming a beadon a piece of steel (1/8“ × 2" × 2"). Then watch the following video:http://www.youtube.com/watch?v=mMADiAMfe00&feature=related. Prepare ablowpipe/torch, two steel pieces (16 gauge × 11/2” × 6), flux, and a 1/16-inch weldingrod. Butt weld the two pieces by using the filler rod.

Web Links:

� Welding Technology Machines

http://www.welding-technology-machines.info/index.htm

Brazing/Welding Procedures and Techniques

http://www.brazing.com/techguide/procedureMain.asp

Braze Welding

http://www.tandtlanco.com/index_files/Page4045.htm

Agricultural Career Profiles

http://www.mycaert.com/career-profiles




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