DELTA SCHOOL OF TRADES pdf

CHAPTER TWO SHIELDED METAL ARC WELDING STICK INTRODUCTION DESCRIPTION THE ELECTRICAL CIRCUIT FOR WELDING THE WELDING MACHINE TYPES OF WELDING MACHINES ARC BLOW... Describe the weldin

DELTA SCHOOL OF TRADES

THIS TEXT WRITTEN AND PUBLISHED BY;

NORMAN J ASHLEY DELTA SCHOOL OF TRADES

First printing January 2000 Latest Printing March 2005 Revised September 1st, 2007

CHAPTER ONE

SAFETY FOR WELDING

SAFETY FIRST CLOTHING FOR WELDING WELDERS UNIFORM FOR DELTA SCHOOL OF TRADES

WELDING MACHINE SAFETY SHOP AND WELDING ENVIRONMENT SAFETY

HANDLEING GAS CYLINDERS

GENERAL SAFETY

STUDENT OBJECTIVES STUDENTS WILL BE ABLE TO:

1 List and describe the type of clothing appropriate for safely welding

2 List and describe the 8 items that make up the welders uniform used at Delta School of Trades

3 Describe the safety guidelines relevant to working with welding machines at Delta School of Trades

4 Describe safety rules relevant to the welding shop and environment

5 Discuss safety issues relevant to using gas cylinders in the welding industry

6 List and describe 4 items related to safely picking up loads in the shop

7 List and describe safety concerns for using hand grinders at Delta School of Trades

SAFETY FOR WELDERS

SAFETY FIRST Safety should be the first consideration when beginning any Trade Welding is an Industrial trade and as such has many hazards that can cause injury if the proper safety guidelines are not

followed

In addition to the safety guidelines for welding training there are many safety rules that apply to the welding field in general and to the particular company you will work for Students and

employees should continue to take an active interest in safety throughout their careers

CLOTHING FOR WELDING Since welding produces intense heat and hot sparks that may cause serious burns, it is important

to wear the proper work clothes The following describes the type of clothing appropriate for welding operations

The shirt should not have frayed edges that sparks from welding can easily ignite

The work shirt should not have any torn areas that allow hot sparks to penetrate

Matches, lighters, or paper materials should never be carried in shirt or pants pockets when welding

Like the shirts the pants should have no frayed edges or torn areas in them

It is advisable not to have metal keys or other devices dangling from the pants that could arc against the work surface

Wear heavy work socks not nylon or thinner socks for added protection against sparks

Safety boots with steel toe caps are advisable for welding shops and work to protect the feet Spats or leggings are leather pieces that fit over the top of the boot to prevent sparks falling into the boots and are available at welding supply stores

C APS

A cap or some form of head covering should be used for welding, especially in other than the flat position The cap must be compatible with the welding head gear called the welding helmet

Welder’s caps or welders beanies (cap with no peaks) are available from welding supply stores

WELDERS UNIFORM FOR DELTA SCHOOL OF TRADES Students or welders at the School need to have the proper welding protection equipment in

addition to wearing the proper welding work clothes

The protection equipment is used to safely view the arc and make the practice welds at the school

It is the same type of personal equipment all welders use on the job

The Welding Uniform is the individuals’ choice of manufacturers and styles, for the following items:

1 THE WELDING HELMET

(WITH SUPPLY OF LENSES)

2 LEATHER WELDING GLOVES

1 THE WELDING HELMET

The welding helmet is designed to protect the welders face and head from the ultraviolet and infrared rays of the welding arc, while allowing the welder to view the molten weld pool or puddle There are a variety of welding helmets and styles available, among them are the flip front, the wide lens, and the auto-darkening lens

The flip front allows the welder to view the weld area through a clear lens, while still wearing the helmet, to safely slag the work or use a grinder

The wide lens helmet offers a wider view of the weld area

(Approximately 4 X 5 instead of 2 X 4) A flip front model of the wide lens helmet is also available

The Auto darkening helmets have a lens that is clear to allow the welder to see the joint before striking the arc As soon as the welder strikes the arc, the lens darkens to the normal view of the welding puddle

The auto darkening lenses are very useful for; production welding where small

welds can be made without constantly lifting the hood; for precise restarting of the weld; for striking the arc without hitting the surrounding area or other parts; for grinding and oxy-fuel cutting

Auto darkening lenses may also be purchased to fit into a standard helmet The auto darkening style of helmet is a lot more expensive than the standard welding helmet and is not essential for use at the school

The welding helmet usually comes with a filter plate (dark plate) and a clear lens on the outer side The filter lens should be shade number 10 for most welding Check the documentation that comes with the helmet for information about the other lens shades that are available

If you use a second clear lens on the inside of the helmet it protects the filter plate when the helmet

is laid down

It is critical to clean welding lenses daily and change the outer lens when it gets pitted or

scratched, about weekly at the school If the inner clear lens is in good condition simply swap it for the front clear lens and place a new lens on the inside

The dark filter plate, if protected by the cheaper clear lenses should not need to be changed

Filter lenses and clear lenses are available as plastic or glass I prefer a Glass filter lens for better viewing and plastic clear lens

Make sure you have an ample supply of clear lenses

2 LEATHER WELDING GLOVES

The welding gloves required for welding are the gauntlet type gloves that cover the forearms Work gloves are not appropriate for arc welding

Lightweight gloves designed for TIG (Healy Arc) give the welder a better feel for manipulating the TIG torch and adding filler wire The TIG gloves are not designed for STICK or MIG

Gloves that are used to handle hot metal may become hard and brittle and crack Use only pliers

to handle hot weld coupons

Wet or damp gloves should never be used for electric arc welding

Gloves that develop even small holes should be discarded and replaced before continuing to weld The less expensive work gloves may be used for general shop work, but should not be used for welding

3 LEATHER JACKET, OR CAPE SLEEVES AND BIB

The leather jacket, worn like a coat, offers the best upper body and neck protection from sparks and hot metal globules typical of welding positions other than flat Most jackets have an inside pocket and snap all the way up to the collar

A lighter jacket made of fire retardant material may also be used in welding shops Some of these jackets have leather sleeves These jackets are good for light welding, but will wear and develop holes when doing a lot of vertical and overhead position welding

The Cape Sleeves and Bib outfit may be made of all leather or the fire retardant material shown above You can select either just the sleeves or the cape and sleeves or the cape and sleeves with a front bib

Although open in the back, the all leather cape sleeves and bib are a good less expensive substitute for the full leather jacket, and is practical for all welding positions

Note: the bib may be sold separately

Welders may get a condition known as an eye flash, either from striking an arc without the helmet

in place, or more likely, from other welders working in the area

People that work around welders, are also vulnerable to eye flash without the proper protection The safety glasses must have side shields to protect the corner of the eye when welders are

working close by

An eye flash occurs when the unprotected eye is burned in a similar manner to a sun burn on skin Painful problems from the flash usually start several hours after exposure (At Night) and may last all night into the next day The symptoms include: A feeling of sand or grit in the eye, an inability

to keep the eye open and focus, intense pain, redness swelling and watering, burning, and

headache

It is my experience that the flash will clear up without long term problems if you avoid further eye exposures Consult a doctor if problems persist more than 48 hours

IT IS CRUCIAL TO WEAR SAFETY GLASSES WHEN WELDING

If you wear prescription glasses, you should use side shields that slip on to the frames of glasses, to protect the sides of the eyes from exposure Many flashes come from other welders and can burn

the eye from the side Goggles that fit over glasses may also be used

A slag hammer or sometimes called a chipping hammer is used to remove the slag from the

completed stick weld The slag hammer may have one pointed and be shaped like a chisel on the other end or have two chisel shaped ends The two most common types are the wire frame and the wood handle

WELDER AND EQUIPMENT

SAFETY IN THE WELDING FIELD

In addition to wearing the proper welding uniform there are a number of safety issues that

welders must be aware of, make sure you understand the safety guidelines in effect at your

company The American Welding Society (AWS) has available several documents concerning safety for further review Of special interest is their safety Standard Safety in welding, Cutting and Allied Processes ANSI/AWS Z49.1

The following is a brief review of some of the guidelines for welding safety:

WELDING MACHINE SAFETY

Before doing any welding read the manual for the type and manufacture of the machine you will

be using

The welding machine is an electrical power source and should be installed by a qualified

electrician or properly trained personnel

Wear the proper clothing and safety uniform to prevent contact with live parts of the welding circuit that can cause severe electric shock or even death The clothing should be dry and free of grease or oil to prevent flash burning

When changing electrode holders, ground clamps, or otherwise working on the electrical circuit make sure the machine is turned off If the power source is in a remote place use a lock-out system

or have another employee watch to ensure no one turns on the machine

Frequently check the ground and electrode cables for bare spots or damage Check to ensure that insulated parts such as the electrode holder are not damaged exposing live parts Only qualified personnel should repair damaged cables, ground clamps or electrode holders

Always wear gloves to insert electrodes into the electrode holder Never leave electrodes in the electrode holder when not welding

Never drape the welding cable over your body to weld

Make sure the welding area is dry and do not weld in rain or wet conditions

Other safety issues apply to Motor generators; make sure you do not work alone, in case of shock the welding machine may need to be shut down quickly

Do not attempt to repair welding machines unless you have been trained and qualified to do so

SHOP AND WELDING ENVIRONMENT SAFETY The welding environment should be well ventilated using fans and extraction devices to remove fumes from the immediate breathing zone and welding area

Special precautions must be followed when welding in confined space, for example; use welding helmets with forced air or use respirators

Keep the welding area free of containers that contain combustible materials, paper, cloth, paint and oily or greasy materials

In case of fire; you should know where the closest fire extinguisher is located and that it is fully charged In special circumstances an assistant is posted to act as a fire watch

You should never weld on drums, tanks, or any closed containers unless properly trained and qualified personnel have authorized their safe use

Be aware of where co-workers are and what they are doing, sparks from welding can travel some distance from the welding area Falling objects may endanger you or co-workers Always warn co- workers when you are about to start welding

A hard hat may be required when welding on some applications Welding helmets that

incorporate a hard hat are available from welding supply stores

Some companies require employees and welders to wear ear plugs in noisy environments

Welding curtains may be used to contain welding activities

Make sure you are aware and understand the safety guidelines that apply to other shop equipment such as; grinders, saws, hand tools and machinery

When welding on galvanized or painted surfaces toxic fumes may be released Remove the coating

by grinding prior to welding Use a respirator in a well ventilated area or weld outdoors Certain types of metals also require the use of a respirator

Keep the welding area clean and free of clutter, metal, excess welding cables and anything that could fall or cause tripping accidents

Know where the first aid station is located and report all accidents regardless how small Burns require immediate treatment to prevent infection

HANDLEING GAS CYLINDERS Because of the shape, contents and weight of gas cylinders used in the welding field it is important they be handled with extreme caution and in a safe manner The following safety guidelines are suggested for safely handling and using gas cylinders

Gas cylinders should never be moved by carrying, dragging or rolling them They should only be moved by securing them in an approved cart The cylinders must have the metal caps in place to protect the valve stem assembly of the cylinder before moving them

If cylinders must be lifted they should be properly secured in an approved lifting cart or on a platform Chains, slings, magnets, and other devices where there may be a possibility of the

cylinder slipping and falling should never be used

Cylinders that are transported over the road should be secured in the upright position with their protective steel caps in place

Oil and grease should never come into contact with the oxygen cylinders, regulators or equipment, since a chemical reaction between the oil and the oxygen may cause a fire or explosion

Hammers pry bars and similar tools must not be used to open a stuck cylinder valve or remove valve caps If the cylinder valve is damaged the force of the escaping gas may cause high pressure cylinders to fly around uncontrolled and cause damage or serious injury

If a cylinder is leaking gas it should be moved outdoors and the gas supplier should be notified immediately

Cylinders must be chained or secured in the upright position secured on a cart or fastened into a welding machine cart When not in use they should have the regulators removed and the caps in place

Never weld on the cylinders, or allow the electrode to come into contact with them and establish

an arc

Use only the approved cylinder wrench to attach regulators and hoses to the cylinder The use of loose fitting wrenches on the soft brass connections may cause excessive wear by slipping on the connections Excessive wear may cause the edges of the connectors to become rounded and make it difficult to fit any wrench on them

Use only the approved regulator and hoses for the type of gas being used and never use the same regulator and hoses for different gas contents

The cylinder the cylinder valve must be cleaned before attaching the regulators Standing behind the cylinder quickly open then close the cylinder valve to allowing the high pressure gas to blow out trapped dirt This action is known as cracking the cylinder Make sure no one is in front of the cylinder when you crack the cylinder

Before attaching the regulator make sure the adjusting screw is backed out and loose Since

regulators are designed to blow out the front and back if they fail, stand to the side of the

regulator when opening or pressurizing the regulator

Fuel gas cylinders should only be opened about ¼ turn or until the gas registers on the regulator,

so they can be shut down quickly in an emergency The high pressure cylinders like the oxygen, argon and 75-25 have a double seating valve and should be opened all the way

GENERAL SAFETY

LIFTING

The following are suggestions for lifting objects in the shop:

1 For heavy items ask for help to lift and move them

2 Use gloves when moving metal or pieces with sharp edges

3 Use lifting devices for extremely heavy material

4 Use the stronger knees to bend and lift not the weaker back

GRINDERS

Metal hand grinders are used at the school for grinding edge preparations and cleaning up, or repairing weld passes Ask for instructions if you have never used a hand grinder

If you purchase a grinder, read the manufacturers handbook and safety recommendations

supplied with the grinder

The following suggestions apply to hand grinders:

• Never use a grinder that has bare wires or a damaged cord

• Do not leave grinders plugged in and unattended on the workbench

• Make sure the safety guard is on the grinder

• Use the handle supplied with the grinder

• Use the face shield and safety glasses when grinding

• Make sure the cord or extension cords do not present a tripping hazard

• Do not lay the grinder down until the wheel has completely stopped

• Never attempt to repair or work on grinders other than regular maintenance

• There are repair centers that specialize in safely repairing damaged grinders

• Use gloves when grinding

• Make sure the sparks from grinding do not present a hazard to co-workers or Cause a fire

threat

CONCLUSION There are many and varied safety guidelines that apply to particular Industries and companies not covered in this section Take an active interest in safety as it applies to your job and

environment to avoid personal injury Continually review safety guidelines and Material Safety Data Sheets that pertain to you and your company

Safety is everyone’s business, never compromise safety to get the job done Many Industrial accidents can jeopardize your career and future

CHAPTER ONE SAFETY FOR WELDING

KEY POINTS

1 Safety clothing must be worn at all times regardless of personnel comfort, for example do not remove leather protective sleeves or jacket in hot weather Always wear safety glasses on the job

2 Always use clean welding lenses They should be cleaned daily and replaced when scratched, pitted, or approximately weekly

3 Always seek first aid for minor burns or cuts

4 replace defective equipment such as, gloves with holes or other equipment with evident wear and tear

5 Read and follow all available safety guidelines for the shop environment and equipment you are using

6 Take an active interest in safety on the job and the rules and guidelines at your place of employment

CHAPTER TWO

SHIELDED METAL ARC WELDING

STICK

INTRODUCTION DESCRIPTION THE ELECTRICAL CIRCUIT FOR WELDING

THE WELDING MACHINE TYPES OF WELDING MACHINES

ARC BLOW

CHAPTER TWO

SHIELDED METAL ARC WELDING

STICK

STUDENT OBJECTIVES STUDENTS WILL BE ABLE TO:

1 Describe the Shielded metal arc welding (stick) process

2 Describe how to start an Electrode (rod) by tapping or scratching

3 Describe the welding machine, polarity and type of current used in Shielded metal arc welding

4 List and describe the 4 basic types of welding machines

5 List and describe the controls on typical welding machines used at Delta

6 Describe the problem of arc blow when using DC current and how to reduce the

effects

THE SHIELDED METAL ARC WELDING PROCESS

STICK INTRODUCTION

The shielded Metal Arc Welding Process (SMAW) is also widely known by the shop term Stick Welding The term stick is a reference to the electrode used to provide the filler metal for welding with this process

The Shielded metal Arc Welding process is one of the oldest and most widely used methods of joining metals by welding The process is popular because of the simplicity of equipment involved, its portability, reliability and adaptability to outdoor use

The process may be used to weld a variety of metal types and shapes in any position

DESCRIPTION

In the SMAW process, welding is done by setting up an electrical circuit using a welding machine

to produce the electricity, a welding cable with an electrode holder to hold the electrode and a ground cable with a clamp to fasten to the work-piece to complete the circuit The weld is made by touching the electrode to the work-piece closing the electrical circuit and causing the electrode to melt and form the weld

T HE ELECTRICAL CIRCUIT FOR WELDING

The electrode has a metal core with a covering referred to as the flux by welders

The metal core of the electrode is either the same as, or is compatible with, the metal being

welded

The main difference between the electrodes used to weld mild steel is the composition of the flux Manufactures add Ingredients to the flux to influence the characteristics (the way the electrode operates) of the electrode These characteristics include; the current and polarity, penetration, spatter, slag type and weld appearance

The covering on the electrode decomposes during welding to provide a gaseous shielding that protects the molten weld puddle from the nitrogen and oxygen in the air that can cause welds to become brittle or have holes (porosity) in them

The covering also aids in arc stability, cleaning (deoxidizing) the metal to be welded and forms the protective black slag that covers the weld metal

KEY POINTS: The slag should be removed before more welds are added to the joint when

multiple pass welding

Electrodes are classified by the American Welding Society based on their specific requirements and intended use

Electrode guidebooks (available at welding supply stores) are a good source of information

regarding appropriate choices of electrodes

To start the weld the electrode is tapped (or scratched like striking a match) on the work-piece then immediately a small gap is held between the electrode tip and work-piece

Since the gap creates an electrical arcing effect between the electrode tip and the work-piece, the gap is referred to as the welding arc

The distance from the tip of the electrode to the work-piece can be varied from lightly touching the work-piece at an angle sufficient to maintain an arc to a distance approximately equal to the electrode core

When viewed through the welding helmet’s filter plate the molten metal from the melting

electrode and work-piece is known as the weld puddle

THE WELDING MACHINE The welding machine (or power source) may vary in style and type but they all produce a steady flow of electrical current with relatively low voltage to maintain a welding arc

The type of welding machine used for stick welding is known as a constant current machine which means the current stays relatively constant as set by the operator while the voltage varies with the arc length

The machine may produce either Alternating Current; Direct Current; or offer a selection of either Alternating Current or Direct Current

Welding machines that utilize Direct Current usually have a method of changing the direction of current flow (polarity) in the welding circuit Some machines have a switch to change the polarity, while on others the welding cables must be switched from one terminal to the other To switch the cables it may be necessary to loosen the terminal bolts or plugs may be provided

When the electrode cable is attached to the positive + terminal and the ground clamp is attached

to the negative – terminal the polarity is Direct Current Electrode Positive (DCEP) or sometimes called Reverse polarity

When the electrode cable is attached to the negative terminal and the ground cable is attached to the positive terminal the polarity is Direct Current Electrode Negative (DCEN) or sometimes called Straight Polarity

KEY POINT; some electrodes are designed to work best on one polarity or the other

Alternating Current does not have a polarity (direction of flow) since the current constantly alternates from one direction to the other

The welding machines may be further classified by input line voltage which may be single phase

or three phase for example: 230 volts 460 volts or in some cases 110

One of the most important considerations may be the amount of amperage the machine is capable

of producing and the duty cycle The duty cycle may be given in a percentage for example: 60% duty cycle means the welder can run at capacity for 6 minutes out of ten Since with stick welding the welder must stop to change electrodes the duty cycle may not be as critical as with Mig

welding

The size of the electrodes to be used determines the amount of amperage the machine will need to produce

TYPES OF WELDING MACHINES

There are four basic types of welding machines that produce the required low voltage high

amperage constant current for stick welding

A transformer welding machine takes the high voltage low amperage line current and transforms

it to the low voltage high amperage current suitable for stick welding These machines are

relatively simple in construction with low power consumption and are economical to operate These machines produce only Alternating Current (AC)

The electrodes selection is limited to those designed to operate on AC current

These machines are often used by home hobbyists

AC Transformers or alternating current may be used to virtually eliminate the problems of arc blow when using Direct Current

(Arc blow is the deflection of the arc from its intended path caused by the magnetic effects of the direct current.)

A N AC TRANSFORMER MACHINE

LINCOLN AC 225 AMPS

2 TRANSFORMER – RECTIFIERS

The Transformer rectifier welding machines changes line current to suitable welding current similar to the transformer machine except that the addition of the rectifier changes the output current to Direct Current (DC) On some machines a switch is used to pass the current through only the transformer to produce AC current, allowing the operator the choice of AC or DC

TRANSFORMER RECTIFIERS MACHINE

LINCOLN IDEALARC AC DC 250 AMPS

A multi-process welding machine is one that may be used to weld with STICK, MIG or TIG, when the necessary components are added

MILLER MULTI – PROCESS MACHINE

3 MOTOR DRIVEN GENERATORS

In the motor driven generator, the motor turns a generator to produce the electric current for welding

The motor that turns the generator may be powered by electricity or by a fuel powered internal combustion engine driven by gasoline or diesel

The fuel gas types are the type of welding machine commonly seen on trucks and job sites These machines may also have components added for multi-process welding

MILLER TRAILBLAZER

4 INVERTERS

Relatively recent technology has allowed welding machine manufactures to take advantage of electronics to rectify and transform line current for the welding circuit in a much smaller size called inverters

Inverter models are available that produce either DC current or offer a choice of AC or DC current

Models available provide either constant current used for STICK and TIG or Constant voltage used for MIG or may combine both

The great benefits of this technology include the production of a line of machines that offer

smaller more portable multiple process machines that are capable of providing a range of

amperages and are less costly than traditional machines

The illustration below shows an invertec V 250 S which is a DC 250 amp stick welding machine used at the Delta School Of Trades

LICOLN INVERTEC 250 AMPS

WELDING MACHINE CONTROLS

There are a variety of welding machines produced by manufactures for stick welding, each with their particular arrangement of controls for selecting the variables for welding Although controls may differ with machine type and style, they serve the same basic functions

Two of the welding machines used at the school are the Lincoln Invertec V250-S and the Miller Dimension 400 These machines will be used to describe the welding machine controls

L INCOLN I NVERTEC V250-S C ONTROLS

(1) ON OFF SWITCH

The on off switch is pushed upwards to turn the machine on and down to turn the machine off

(2) THE NEGATIVE AND POSITIVE TERMINALS

The negative and positive terminals are used to change polarity between Electrode positive work negative or Electrode Negative and work positive

The work (ground) cable plug and the Electrode cable plug are twisted, pulled out and switched to change from one polarity to the other

(3) RUNNING LIGHT OR PILOT LIGHT

The pilot light is red when the machine is on and running

(4) HOT START

The hot start Control regulates the amount of starting energy when initiating the arc in Stick welding The higher setting may be used for esier arc starting with some electrodes

(7) GTAW SMAW SETTING

This control offers a choice of GTAW SMAW SOFT OR SMAW CRISP

The GTAW setting is used when the TIG (GTAW) equipment is attached and aids in touch

starting the arc

The SMAW SOFT setting is used to soften the arc for Electrodes like the E-7018 and E-7028 The SMAW CRISP setting allows a crisper arc when using Electrodes like the E-6010

(8) THE REMOTE CONTROL

The remote control switches control of the amperage between

(9) REMOTE RECEPTACLE

The remote receptacle has a cover that can be removed to attach a remote device to control the amperage from zero to the upper limit set on the machine This control is often utilized for adding

a foot pedal when TIG (GTAW) welding, or when a hand operated remote control is used

MILLER DIMENSION 400 MULTI-PROCESS WELDING MACHINE CONTROLS

(4) PROCESS SELECTOR

The process selector is used to switch from CC CONSTANT CURRENT used for Stick (SMAW) and Tig (GTAW) welding to CV CONSTANT VOLTAGE used for Mig (GMAW) welding

(5) ARC CONTROL

The arc control dial provides better arc starting for certain electrodes when Stick welding

Examples: When using 6010 Electrodes the higher range aids in striking the arc When using

E-7018 Electrodes the lower range is used to lessen the effects of arc blow

(6) AMPERAGE CONTROL

This control is a dial that is turned clockwise to increase the amperage when Stick welding or to increase the voltage when Mig welding There are two sets of numbers around the dial The lower numbers in white squares are read as voltage for Mig welding The higher numbers indicate the amperage level for stick welding

(7) REMOTE CONTROL SWITCH

The remote control switch is a toggle switch with two settings ON or OFF The switch position is off for stick welding and on when using a remote control device such as a foot pedal

(8) AMPERAGE METER

The amperage meter or AMMETER is a gauge that indicates the amount of amperage the welder

is using during welding The Ammeter setting will fall to zero when the welder stops welding

(9) VOLTAGE METER

The Volt meter acts in the same manner as the ammeter except it shows the voltage during

welding

(10) THE REMOTE CONTACT SWITCH

The remote contact switch is a toggle switch with two settings ON or OFF The switch position is off for stick welding and on for MIG welding or Tig welding with a foot pedal attachment

ARC BLOW

DESCRIPTION

A condition called arc blow may occur when using Direct Current (DC) to weld some joint designs with the stick welding process The direct current passing through the electrode and the base metal sets up a magnetic field around the electrode The force of this magnetic field can be strong enough to pull the arc from its intended path causing an unstable weld puddle resulting in a poor weld with excessive spatter Arc blow may become very severe at the ends of a joint for example; the top part of Vee groove or when welding the inside corners of a T joint

Severe Arc Blow may appear to the welder as if someone is blowing the arc with an air hose

REDUCING THE EFFECTS OF ARC BLOW

USE ALTERNATING CURRENT (AC)

Alternating current flow changes direction constantly and as a result the magnetic field does not build up enough to cause severe arc blow

When welding certain joint configurations, and arc blow prevents producing quality welds, if possible switch from Direct Current to Alternating Current

Although using AC current virtually eliminates the problems associated with Arc Blow it may not

be possible to switch current on the machine or use another machine Try one or more of the following tips to reduce the effects of Arc Blow

WORKING WITH THE GROUND CLAMP

Arc Blow usually occurs either forward or backward along the joint being welded If forward Blow occurs, place the ground connection at the edge of the joint to be welded If backward Blow occurs, place the ground connection at the start of the joint and weld towards a heavy tack, prior weld bead or run off tab If you are unsure whether forward or backward Blow is occurring, try moving the ground connection to another location

If the ground connection is very close to the workpiece, try moving it as far from the joint as possible

Try adding a connection to the ground clamp so that you have one ground lead, but two ground clamps Place one clamp on opposite ends of the section to be welded

Some welders wrap a short section of the ground cable around the workpiece to set up a magnetic field to counteract the effects of the magnetic field causing the Arc Blow effect Caution must be used to prevent burning the ground cable

Try uncoiling the ground cable and electrode cable and stretching them out

Place a weld at the opposite ends of long sections first

Instead of welding from one end to the other, use a series of shorter welds in staggered locations to completely weld the joint

Weld towards a heavy tack weld or prior weld Stop and change the direction of travel when Arc Blow occurs

Use a smaller diameter electrode if possible

TECHNIQUE

A change in technique will reduce the effects of Arc Blow Try the following:

Change the electrode angle Slight angle changes during welding, when arc blow occurs, helps to lessen the effects enough to finish the weld bead Try changing the angle to follow the direction of blowing, even if the electrode seems to burn down one side unevenly

Use the lowest amperage setting practical, especially on root passes when welding grooves Some electrodes, such as the E-7018, have iron powder in the flux and are more prone to Arc Blow If possible use an alternative electrode, such as the E-6010, for the root or first pass before using the E-7018 for the balance of the passes

Maintain a short arc length and decrease the length of arc if Arc Blow occurs

Turn the arc control settings on the machine to a lower value when welding joints that seem prone

to Arc Blow

WELDING THE ONE INCH VEE GROOVE One of the projects at the School is to weld a vee groove in the vertical up position When welding the first and second passes Arc Blow may occur at the top inch and a half Try the following to reduce the effects of Arc Blow:

Make sure you put a heavy weld on both sides of the backing strip in the flat position before welding the groove

Check the amperage is set correctly and not too high

Use the backing strip as a run off tab Start well below the joint on the backing strip and run the bead out past the joint at the top

If Arc Blow occurs on the first pass keep the arc length low and the electrode pushed against the backing strip Keep the electrode angle low and steep If the electrode burns down on one side, do not change the angle

SHIELDED METAL ARC WELDING

KEY POINTS

1 The stick welding electrical circuit is made up of the Welding machine, Electrode cable, Electrode holder, Electrode, Work plate, and Ground cable

2 The weld is started by tapping or scratching the electrode against the work piece

3 In reverse polarity the electrode cable is attached to the positive terminal of the welding machine and the ground cable is attached to the negative terminal

4 In Straight polarity the electrode cable is changed to the negative terminal and the electrode cable is changed to the positive cable

5 The polarity in AC (alternating current) changes constantly and requires no

adjustment

6 Learn about the type of machine you are using on the job and how to set the

controls for the specific job conditions

7 Recognize and reduce the effects of Arc blow when using DC machines or use Ac machine

CHAPTER THREE

THE FIVE ESSENTIAL VARIABLES OF SMAW

(STICK)

STUDENT OBJECTIVES STUDENTS WILL BE ABLE TO:

1 List and describe the five essential variables of Shielded metal arc welding

2 Set the correct current for a given application

3 Maintain the proper length of arc

4 Maintain the correct angles of electrode while welding

5 Control the proper speed of travel while welding

6 Select the correct electrode for a given application

7 Recognize and correct welding discontinuities

THE FIVE ESSENTIAL VARIABLES OF SMAW (STICK) WELDING

INTRODUCTION

Welding is a practical skill that requires continual practice and careful attention to the variables that the welder controls to improve The old golden rule “practice makes perfect” applies to welding in that the more you do, as long as you or someone evaluates your welds, the better you become

The term variable as used in this text means something the welder has control of either before welding or during welding

Review the following five essential variables and the weld discontinuities that may result if control

amperage on the welding machine prior to welding

The amperage is set from recommended ranges according to the size of the electrode, the type of electrode, and the type of current AC, DCEN or DCEP you are using

KEY POINT: AC means Alternating Current, DC means direct current and can be set for Direct Current Electrode Negative (Straight Polarity) or Direct Current Electrode Positive (Reverse Polarity)

Some electrodes are designed to work best on a given Current and Polarity, for example an

E-6010 should be used with DCEP (direct current electrode positive)

Some electrodes are designed to work best on DCEN while others allow a selection of Current to

be used

The chart below shows typical amperage ranges

Amperage may be referred to as the heat by some welders

An excellent place to find amperage ranges, recommended current and polarity and information

on electrode applications are the Electrode Selection Guidebooks available at any welding supply store

The amperage range is fine tuned by the welder to the correct amperage before welding on an actual workpiece or testpiece by running practice welds on a piece of scrap metal in the position

of welding as follows;

1 Run a practice weld at the lower recommended range setting

2 Run a second practice weld at the higher recommended setting

3 Compare the two welds for evidence of a well formed bead, good fusion, lack of defects, and a smooth transition into the base metal

4 If necessary reduce the amperage from lower to highest amperage until a satisfactory weld bead is produced

5 It is important to try different setting to avoid wasting time with a setting that is to low or

to high and will need to be changed later

The chart below gives an idea of the evaluation process;

In example A the E-6010 weld made with the correct amperage appears properly formed with the appropriate width and consistency

In example B the weld made with amperage setting too low appears thin and stringy

In example C the weld made with amperage setting too high appears wide and flat with excessive spatter and evidence of undercut

A B C

A) Amperage correct B) Amperage too low C) Amperage too high

KEY POINT: Remember conditions may change for example; if you are welding multiple passes

in the vertical position and using a weave technique you may need to increase the amperage when weaving over a prior weld bead

You may want to use higher setting for welding flat and horizontal than for welding in other positions

A setting used on one machine may need to be adjusted when using another machine, if the

machines are not calibrated the same

One welder (operator) may prefer to use a slightly higher setting and travel faster than you, so set the amperage for your technique

The correct amperage is one that provides a good weld and is not based on a specific number on the machine

2 LENGTH OF ARC

When electricity is made to jump across a gap it is said to arc across the gap In Shielded Metal Arc Welding (Stick) it is this arcing effect that creates the intense heat required for melting the electrode and the base metal together

The Arc is the term used to describe the distance from the tip of the electrode to the base metal and can be varied from lightly touching the metal at an angle sufficient to maintain an arc to a distance far enough from the base metal to extinguish the arc

If the electrode is held in contact with the work using the slight angle to maintain the arc it is referred to as the drag technique This technique is often used to weld in the flat and

horizontal positions, especially with larger or iron powder electrodes If contact with the base metal is made too quickly however; the electrode will stick or freeze to the metal

Another method to employ is to allow a slight gap between the electrode tip and the base metal The length of the arc gap affects the appearance of the weld

The welding machines used in Shielded Metal Arc Welding are known as Constant Current

machines which mean that the current stays relatively constant through changes in the voltage The machine increases the voltage as the arc length is increased to maintain current flow at the amperage level set on the machine If the voltage is increased too much the arc may become

unstable and result in a poor quality weld

The correct arc length may vary according to the type of electrode and the position of welding When production welding flat or horizontal the drag method is often used for ease in welding and faster travel speeds

When a slight gap is maintained the force of the arc provides a weld bead with a slightly flatter appearance with less chance of slag inclusions and better joint penetration

KEY POINT: make sure you are maintaining a proper arc length before adjusting the amperage

on the welding machine If the arc length is too long and the voltage increases it may seem as though the amperage is too high or the sticking caused by too low an arc length with some

electrodes may seem as though the amperage is too low

3 ANGLE OF ELECTRODE

In the Shielded Metal Arc Welding (STICK) process there are two electrode angles that the

welder must control The first angle is the one formed between the electrode and the base metal, called the work angle The second angle is the angle the electrode is held at relative to the direction

of travel, called the travel angle

The travel angle for the flat, horizontal and overhead can be either pulled or pushed and

the travel angle for the vertical can be either upward or downward

welding flat and horizontal When welding in the vertical upward position a more extreme angle using the side of the electrode seems to produce a flatter weld with tighter ripples

KEY POINT: because of the high deposition rat of an E-7018 electrode it is more difficult to weld vertical downward

of the joint

Since the travel speed is not timed in stick welding, the welder must be able to read the molten weld pool as the electrode is manipulated across the joint A weld speed that is too fast results in a thin stringy weld with poor strength A weld bead that is too slow a speed will result in a heavy weld that has too much convexity

5 SELECTION OF ELECTRODE

There are a variety of electrodes available for welding a wide range of metals The electrode for a given application must be selected carefully to provide the strength characteristics required for the weld joint One of the most useful tools for electrode selection is the Electrode Handbooks available from welding supply outlets These handbooks provide information from electrode classification to application and usability

In general the electrode weld metal must be matched to the type and composition of the base metal being welded Further some electrodes within the available scope are designed for specific

purposes

Some of the most widely used Electrodes are those used for welding carbon Steel

The following is a brief description of the most commonly used electrodes for welding Carbon Steel

The electrodes are classified by a letter and numbering system as follows:

The E-6010 and E-6011 Electrodes are similar with only a slight change in the electrode covering

to enable the E-6011 to be used with AC current

These electrodes have a deep penetrating and forceful arc with quickly solidifying weld metal They may be used in all positions including Vertical Downward Because of the arc characteristics they may be used on dirty or rusty metals and for root passes in open root grooves and pipe These electrodes have a certain amount of moisture content to enable the forceful arc and should not be stored in ovens

The E-6012 and E-6013 electrodes are also similar with some variations in the electrode covering These electrodes have shallow to medium penetration making them useful for welding thinner

sections, sheet metal and for welding gaps due to poor joint fit up Trapping slag may be a

problem when using E-6013 at lower amperages or on dirty metal surfaces

Both the E-7018 and E-7028 electrodes are Iron powder Low hydrogen electrodes The E-7028 is used for flat and horizontal position only and may be used with a drag technique to produce a smooth weld with good appearance

The addition of Iron powder to these electrodes covering adds to the available weld metal

resulting in heavier convex welds

These electrodes are classified as low hydrogen meaning they are low in moisture content and should be stored in ovens or moisture free environment once the container is opened

Because these electrodes are low hydrogen they are the choice for welding higher carbon steels

A short arc length should be maintained especially when striking the arc to avoid surface porosity (tiny holes)

When the five essential variables are properly controlled the weld profile should be properly

formed and free of discontinuities

Weld Profiles

Note: In the above diagrams the size of the fillet weld is shown in dotted lines and the throat is

from the root of the joint to the face of the weld