Perform routine manual metal arc welding (MMAW)

Perform routine Manual Metal Arc Welding • Routine MMAW in this unit is intended to apply in a manufacturing or maintenance environment where welding is not required to meet Australian Standards or other welding codes, licensing requirements, Occupational Health and Safety regulations relating to certificatedcoded welding. • Fillet and butt welds in all positions would typically be performed on low carbonmild steels. • Weld preparation would be minimal and generally restricted to cleaning, using files and grinders. • In circumstances where welding is required to meet Australian Standard 1554 General Purpose or equivalent codes, Occupational Health and Safety regulations andor licensing requirements then Unit 5.15A (Weld using manual metal arc welding process) should be selected.

5.12A Perform routine

Manual Metal Arc Welding

Pre-requisites: Nil

• Routine MMAW in this unit is intended to apply in a manufacturing or

maintenance environment where welding is not required to meet

Australian Standards or other welding codes, licensing requirements, Occupational Health and Safety regulations relating to

certificated/coded welding

• Fillet and butt welds in all positions would typically be performed on low carbon/mild steels

• Weld preparation would be minimal and generally restricted to

cleaning, using files and grinders

• In circumstances where welding is required to meet Australian

Standard 1554 General Purpose or equivalent codes, Occupational

Health and Safety regulations and/or licensing requirements then Unit 5.15A (Weld using manual metal arc welding process) should be

selected.

5.12A Perform routine MMAW

Range statement

Element 5.12A.1 Identify weld

requirements

In this element you will be required to achieve competency in the following areas:

presentation we will look at:

• weld requirements.

1.2 Location of welds are identified in accordance with standard

operating procedures and job specifications In this

presentation we will look at:

• basic weld symbols.

5.12A Perform routine MMAW

Weld requirements

• Weld requirements for a project can be given in a number

of ways.

• They can be in the form of a:

- work instruction or job sheet

tion

WELDE

N

ENG

AS 1210

Unfired Pressure Vessels

at io n

o f

W eld er

s &

W eld

in g

S u er vis o r

AS 1554 AS 1

796

5.12A Perform routine MMAW

Weld symbols

• Welding symbols enable the engineer/draftsperson to communicate important detailed information regarding the weld, to the welder.

10mm fillet weld other side of arrow

MMAW

Basic weld symbol

10 6

6mm fillet weld arrow side

Weld on siteWeld all roundUse the Manual Metal Arc Welding Process

5.12A Perform routine MMAW

Basic weld symbols

Fillet weld

Fillet weld both sides

6mm leg length (arrow side)

12mm leg length (other side)

12 6

Fillet weld (both sides)

8mm leg lengths

8 8

5.12A Perform routine MMAW

Basic weld symbols

Fillet weld

6mm leg length

Weld all round

6

Single ‘V’ butt joint (arrow side)

Weld arrow side

Butt joint – Open square

Welded arrow side

5.12A Perform routine MMAW

Basic weld symbols

Weld 6mm fillets Both sides of the plate Top and bottom of the project

Weld 10mm fillets Both sides of the plate

Weld 6mm fillets Both sides of the plate

Weld 6mm fillet Both sides of plate

Weld all round 10mm fillet On-site

Weld 10mm fillet Arrow side On-site

Generally as welding is being conducted these areas are welded to provide a neat

finished project

Element 5.12A.2 Prepare materials

for welding

In this element you will be required to achieve

competency in the following areas:

2.1 Materials are cleaned and prepared for welding In

this presentation we will look at:

5.12A Perform routine MMAW

Plain Carbon Steel

• It is necessary to ensure that the

material to be welded is clean and

free from:

– oil and grease

– paint

– metallic coatings such as galvanised

and chrome plating

– moisture

– corrosion - rust and mill scale

• These impurities can readily be

removed by wire brushing, grinding,

solvents, linishing or abrasive

blasting.

• If left on, they may cause weld

defects.

5.12A Perform routine MMAW

5.12A Perform routine MMAW

5.12A Perform routine MMAW

Weld terminology – fillet welds

Heat effected zone

Fusion zone

Weld metal

Leg lengthReinforcement

Toe

PenetrationParent metal

5.12A Perform routine MMAW

Weld terminology – butt welds

Parent metal

Weldmetal

Fusion zoneHeat effected zone

Penetration

ReinforcementRoot face

ThroatIncluded angle 60 - 70°

Root gap

5.12A Perform routine MMAW

Reproduced with the kind permission of

– Grinders are used for fast plate removal.

– By holding the wheel on the edge, fast removal of material is possible.

– Using the flat of the wheel allows for removal of uneven surfaces.

• FLAME CUTTING

– Can be utilised on straight plates or pipes.

– Grinding may be necessary if uneven surfaces

(nicks) are the result of this process.

• MACHINING PREPARATION

– Nibblers are by far the quickest method of removal:

• material thickness from 3 to 40mm possible

• angles of 22 o to 45 o possible.

– Pipe bevelling machines can be used for preparation of pipes:

• machines are very expensive to purchase.

– Lathe machining can be used:

• time consuming

• plate set up as well as machine set up is required.

Element 5.12A.3 Prepare equipment

for welding

In this element you will be required to achieve competency in the following areas:

3.1 Welding equipment is set up correctly In this

presentation we will look at:

• definition

• MMAW line diagrams

• equipment.

3.2 Settings and consumables are selected to suit application

In this presentation we will look at:

• welding fundamentals.

Reproduced with the kind permission of the

Australasian Welding Journal

• Is a fusion welding process.

• Uses the heat of an electric arc

between a consumable electrode

and the work piece.

• The molten pool and arc is protected

by a gaseous shield generated by the

decomposition of the flux covering

on the electrode.

• The operator must maintain a

constant arc length and travel speed

as the electrode is consumed into

the weld pool.

5.12A Perform routine MMAW

The process

5.12A Perform routine MMAW

The basic MMAW plant layout

Electrode holder

Return clamp

Return lead Electrode lead

The electrode lead is connected to the

electrode terminal on an

AC transformer machine and

ACDC transformer rectifier

The electrode holder grips the electrode in place

They are fully insulated and should be rated for at

least the maximum current of the power source

Electrode Work

The welding current is conducted to the

electrode holder with copper or aluminium

multi strand insulated cables

An arc is struck between a flux covered

electrode and the work piece

The return clamp is connected to

the work piece and work terminal

via the return lead which

Work piece

5.12A Perform routine MMAW

Electrode lead and Electrode holder

Return lead and Return clamp

Reproduced with the kind permission of ESAB

Reproduced with the kind permission of ESAB

Reproduced with the kind permission of ESAB

Chipping hammer and Wire brush

Welding shield with correct lens

Personal protective equipment

Reproduced with the kind permission of ESAB Australia Pty Ltd

Welding Helmet Leather Scull Cap Safety Glasses

Recommended Minimum Protective Filters for MMAW

Approximate Range of Welding Current

Up to 100 amps

100 – 200 amps

200 – 300 amps

300 – 400 amps Over 400 amps

Filter Recommended

8 10 11 12 13

To produce a quality weld the operator must

consider the following fundamentals:

Material preparation

5.12A Perform routine MMAW

Fundamentals of MMAW

Preparing material incorrectly may lead to weld failure.

Electrode manipulation is impeded if the edges are not prepared correctly Material should be cleaned and free from paint, grease, oil, heavy oxidation and mill scale.

60 o –70 o

0 to 3mm

0 to 3mm

Up to 12mm

Gouge marks need to be ground smooth or if too deep, may require filling with weld and dressed.

• The type of electrode to be used on a

particular job may be specified on a:

• work instruction or job sheet within an organisation

• a welding code

• an engineering drawing

• a weld procedure sheet.

• It may be the responsibility of the

operator to select the appropriate

electrode for the job.

5.12A Perform routine MMAW

Fundamentals of MMAW

Type of electrode

• There are four basic types of electrodes.

• Classified according to their flux compositions:

• Forms a gaseous shield around the molten weld pool,

electrode tip and molten droplets protecting it from the

atmospheric contamination

• Controls penetration, surface finish of the weld and arc

stability

• To form a molten slag which floats to the surface to provide a

protective cover whilst the weld cools

• Acts as a cleanser by dissolving impurities and surface rust

• Controls the bead shape

• Controls the chemical and mechanical properties by

replacing lost elements as required

5.12A Perform routine MMAW

Fundamentals of MMAW

Function of the flux coating

Type of electrode continued

5.12A Perform routine MMAW

Fundamentals of MMAW

Reproduced with the kind permission of CIGWELD

Reproduced with the kind permission of WIA

Rutile - Exx12 and Exx13

• Medium penetration

• Smooth running

• General purpose electrode

• 12’s have viscous slag

• 13’s have a fluid slag

Cellulose - Exx10 and Exx11

• Paper pulp coating

• Forceful deep penetrating arc

• Large volume of shielding gas

• Produces considerable amounts

of spatter

Type of electrode continued

5.12A Perform routine MMAW

Fundamentals of MMAW

Reproduced with the kind permission of WIA

Hydrogen controlled - Exx15 and Exx16

• Produces very little hydrogen gas.

• Must be used dry.

• Fluid slag.

• Medium penetration.

• Moderate amounts of spatter.

• Used on low alloy steels, restrained joints.

• Produces a superior quality weld.

Iron powder - Exx24 and Exx27

• Used in the flat position

• High deposition rates

• Medium penetration

• Smooth running

Reproduced with the kind permission of CIGWELD

Size of electrode

5.12A Perform routine MMAW

Fundamentals of MMAW

The size of electrode is dependant on the section being welded.

The heavier the section the larger the diameter of electrode.

Consideration needs to be given to the type and size of joint.

Good root access is required to achieve penetration.

1.6 or 3.2 Ø3.2

5.12A Perform routine MMAW

Fundamentals of MMAW

Selection of the correct amperage in Manual Metal Arc

Welding is extremely important

The correct amperage for particular electrode and size is

generally specified by the manufacturer on the packet

with a range, eg: recommend 85-140 amps for 3.2 Ø

The operator must select an amperage within a range

that will be suitable for the thickness and type of joint

being welded

Too low a welding current will cause:

Too high a welding current will cause:

angle will cause a high weld

bead and with less

penetration.

An increase in electrode angle will cause a flatter bead of weld and possibly cause the slag to flood the weld pool This can cause slag inclusion and a reduction in the arc’s penetration.

Arc length, ie: the distance from the tip of the electrode to the work piece.

5.12A Perform routine MMAW

Fundamentals of MMAW

Too short an arc length will cause the electrode to stick in weld pool and cause a narrow, uneven bead

Too long will cause a

decrease in penetration and

an increase in weld

spatter.The weld will be flat

and have a coarse ripple

pattern

The correct arc length is dependent on the type of

electrode, size of electrode and position of

welding A guide would be approximately the

diameter of the core wire in the electrode you are

using

Ø

Ø

Travel Speed, ie: the rate at which the welder moves the electrode

across the joint to deposit the weld

5.12A Perform routine MMAW

Fundamentals of MMAW

of weld and possibly cause the slag to flood the weld pool This can cause slag inclusion and a reduction in the arc’s penetration.

cause a reduction in

penetration and produce a

narrow and shallow bead.

With the correct arc length, the travel speed should be determined

by producing a bead width of 1½ - 2 times the diameter of the

electrode.

Element 5.12A.4 Perform routine welding

using Manual Metal Arc Welding

In this element you will be required to achieve competency in the following areas:

4.1 Safe welding practices are applied In this presentation we will

look at:

• welding safety.

Practical - to be carried out in the workplace/training organisation

4.2 Materials are welded to job requirements In this presentation

we will look at:

• MMAW weld faults and causes

Practical - to be carried out in the workplace/training organisation

4.3 Welds cleaned in accordance with standard operating

procedures In this presentation we will look at:

• weld cleaning.

Practical - to be carried out in the workplace/training organisation

5.12A Perform routine MMAW

Personal protective equipment

Reproduced with the kind permission of WIA

Reproduced with the kind permission of BOC

• Helmet shade 10 - 13 filter lens.

• Flame proof clothing (woollen or cotton):

• The welding process produces many hazards that the

operator must be aware of in order to eliminate or

minimise the risk of injury to themselves or others.

• Welding hazards are as follows:

• Fumes.

• Electrocution.

• Radiation.

• Heat.

• Fire and/or explosion.

5.12A Perform routine MMAW

Welding hazards

Are harmful if breathed in.

• Causes:

– production of oxides and nitrous gases

• incomplete combustion or oxidisation of nitrogen from atmosphere

– paint and solvents

– composition of parent metal.

5.12A Perform routine MMAW

Welding safety - fumes

• Dangerous fumes are given off during the welding

process They can cause:

– gassing or asphyxiation because oxygen has been depleted

– respiratory ailments - from wheeziness to serious lung disorders.

5.12A Perform routine MMAW

Welding safety - fumes

• Always use ventilation wherever possible, such as :

• Fume extraction – portable units

H0T 2pm

5.12A Perform routine MMAW

Welding safety – heat and burns

• Burns

– protect yourself by wearing gloves and using tongs to carry hot material

– if your leaving your job which has involved welding or thermal cutting, write ‘HOT’

on it and the time Protect your fellow workers.

• Conduction

– travels through a solid:

• copper and aluminium are good conductors

• cast iron and stainless steel are poor conductors they localise heat.

• Radiation

– travels through air by wave motion:

• no physical contact necessary – during intensive welding such as pad welding.

• Caution

– Also, due to the equipment which is required to be worn, it is necessary to keep up your fluid intake to avoid dehydration, especially if working outside.

5.12A Perform routine MMAW

Welding safety - radiation

welding process

• These rays can cause:

• Flashes:

– takes 4 - 8 hrs to develop

– feels like sand in eyes

– rays very deep penetrating

• Ray burns:

– Like sun burn

– Can cause blisters and sores

• Protect yourself from these rays by wearing the correct equipment and lens filters shade 10 minimum and safety glasses.

• Protect others by using welding screens around your area.

5.12A Perform routine MMAW

Welding safety – hazardous locations

• A hazardous location is an area where flammable or

explosive substance are present or have been.

• No oxygen equipment can be taken into these areas

unless a permit is obtained from a safety officer.

Hazardous locations

• Alcohol distilleries, oil refineries,

paint factories, explosive plants,

coal crushers, flour mills,

saw mills, wheat silos, paper mills.

5.12A Perform routine MMAW

Welding safety – hazardous locations

Procedure for hazardous locations:

Inform safety officer of work and equipment to be used.

Officer must inspect site and make safety recommendations Safety officer must issue a work permit.

When cutting, welding or heating you must know

the nearest fire brigade’s phone number.

Have on hand the correct fire extinguishers.

Wait 1 hour minimum after you have

finished cutting, welding or heating.