SAMPLE. MEM05015D Weld using manual metal arc welding process. Learner guide. MEM05 Metal and Engineering Training Package.

Transcription

1 MEM05 Metal and Engineering Training Package MEM05015D Weld using manual metal arc welding process Learner guide Version 1 Training and Education Support Industry Skills Unit Meadowbank Product code: 5583

2 Acknowledgments The TAFE NSW Training and Education Support Industry Skills Unit, Meadowbank would like to acknowledge the support and assistance of the following organisations and people in the production of this learner guide. Standards Australia CIGWELD Australia Lincoln Electric Co (Australia) Pty Ltd The Fabricator Welding Industries of Australia (WIA) Writer Jim Miles (form existing TAFE Resources) Reviewer Ed Harkness (Illawarra Institute) Project Manager Stephen Davies Education Programs Manager TAFE NSW Enquiries Enquiries about this and other publications can be made to: Training and Education Support Industry Skills Unit, Meadowbank Meadowbank TAFE Level 3, Building J See Street MEADOWBANK NSW 2114 Tel: Fax: TAFE NSW (Training and Education Support, Industry Skills Unit Meadowbank) 2012 Copyright of this material is reserved to TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank. Reproduction or transmittal in whole or in part, other than for the purposes of private study or research, and subject to the provisions of the Copyright Act, is prohibited without the written authority of TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank. ISBN TAFE NSW (Training & Education Support Industry Skills Unit, Meadowbank) 2012

3 Table of Contents Introduction General introduction Using this learner guide Prior knowledge and experience Unit of competency overview Assessment Topic 1: Welding safety Review questions Topic 2: Basic electrical terms and definitions Review questions Topic 3: The manual metal arc welding process... (MMAW) Advantages Limitations Machines Accessories Types of current Open circuit voltage (OCV) Rating of power sources (Duty cycle) Review questions Topic 4: Electrodes and electrode classification Review questions Topic 5: Distortion control and weld joints Weld joints Review questions Practical jobs and projects Job 1: Fillet weld - vertical Job 2: Fillet weld - section to plate - vertical Job 3: Fillet weld - overhead TAFE NSW (Training & Education Support Industry Skills Unit, Meadowbank) 2012

4 Job 4: Fillet weld - section to plate - overhead Job 5: Butt weld - horizontal Job 6: Butt weld - section to plate - horizontal Job 7: Butt weld - vertical Job 8: Butt weld - section to plate - vertical Project 1: Fillet and butt welds - structural section Project 2: Fillet and butt welds - plate section Resource Evaluation Form TAFE NSW (Training & Education Support Industry Skills Unit, Meadowbank) 2012

5 Topic 1: Welding safety The Work, Health and Safety Act 2011 (WHS Act) and WHS Regulations are enforced throughout all Australian States and Territories. This legislation is aimed at providing consistency, certainty and clarity across Australia making it easy to understand workplace health and safety responsibilities. Consequently this act and its regulations requires both employers and employees to take every reasonable step to work safely and responsibly in the workplace. There are no short cuts to working safety, its everyone s responsibility to manage and minimise potential risks in the workplace, report faulty equipment as well as unsafe environments. Detailed information relating to the WHS Act and regulations can be found on: WorkCover Authority of NSW website or on Safe Work Australia Welding operators must know about the principles governing the welding operation, equipment used and workplace health and safety precautions required. The following points need to be taken into account when working in a welding environment. Hazards Working with electrical equipment can be hazardous. You must take proper precautions and follow set safety procedures. Electric shocks (low voltage) Electric shocks are possible from the secondary (low voltage) side of the welding circuit. They may be caused by: Working in very humid climates or wet/damp conditions - keep your gloves dry at all times Working on wet floors; a shock may be felt when putting an electrode in the holder Always stand on insulated mats or wooden boards to reduce the risk Wear rubber soled shoes for further insulation. Fumes Welding should be carried out in well ventilated areas When welding high fuming materials such as galvanized steel, use an exhaust fan to carry away the fumes If an exhaust fan is not available, an approved respirator should be used to filter the fumes. TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 19 of 84

6 Dangerous fumes Gases, dusts and vapours are given off during welding. In extreme circumstances they can cause the following: Asphyxiation due to the oxygen depletion in the work area (common in confined spaces) A build up of poisonous metals in the body, such as lead, cadmium, zinc, beryllium or mercury Respiratory ailments from wheeziness to serious lung disorders. Causes of fumes The production of oxides and nitrous gases in the arc Incomplete combustion or oxidation of nitrogen from the atmosphere Elements, compounds and gases in the melting electrode flux coating Metal coatings and surface contaminants vapourising in the arc. Surface coatings on steel Sometimes operators will need to weld steel surfaces that have been coated to preserve a corrosion resistance appearance. Typical coatings include: Galvanizing Cadmium plating Chrome plating Paints and solvents (such as red oxide coated parts and de-greasing solvents). Elements within the parent metal Elements of steel Iron/manganese fumes. Hot metal, heat and arc radiation Molten droplets have a way of getting onto boots. You can avoid harm by wearing proper protective clothing and footwear. When welding out of position, for example in the vertical or overhead position, wear spats over your boots and under the legs of your overalls to prevent hot metal sparks or droplets burning your skin. Page 20 of 84 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

7 Review questions These questions have been included to help you revise what you have learnt in Topic 1: Welding safety. 1. List three (3) precautions welding operators must take to avoid an electric shock. 2. List five (5) items of protective clothing and equipment (PPE) MMAW operators are expected wear. 3. Other than electric shock, list two (2) hazards associated with working in a welding environment. 4. Name the two (2) harmful rays emitted from an electric arc. 5. Briefly explain the harmful effects the above arc rays can have on the welding operator. TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 23 of 84

8 Multiple choice questions (Tick the box with the correct answer) 6. Welding over galvanized steel will produce: o rust resistant welds o stronger welds o poisonous fumes o more ductile welds 7. Welding filter lens must be: o shade 13 minimum o approved and identified to Australian Standards o made in Australia o green 8. Ensuring a safe working environment is the responsibility of the: o employer and employee o welding supervisor o owner of the business o chief engineer 9. The legislation governing the safety of Australians in the workplace is the: o Work, health and safety act of 2011 o AS 1796 certification of welding operators and supervisors o NSW OHS act of 2000 o Metal and engineering award. Page 24 of 84 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

9 Topic 2: Basic electrical terms and definitions The heat energy required for manual metal arc welding is generated by an electric arc struck between a flux covered electrode and the workpiece. The application of electricity means it is important that welding operators have a basic understanding of electrical terminology an principles associated with MMAW process. Electricity Electricity is a form of energy associated with movement of electrons which create a magnetic field and heat energy. Voltage Voltage is the unit of electrical pressure. This electrical pressure (or force) is responsible for the current flow in a welding circuit. Voltage is commonly referred to as electro motive force (EMF). Current Current is the measure of the electron flow through a conductor. An ampere can be described as a measure (quantity) of electricity passing through a given point per second. This is similar to the rate water flows through a pipeline. Conductor In welding, an electrical conductor is a metal through which electricity will easily flow. Copper is the most used conductor followed by brass and then aluminium. Resistance Electrical resistance is a measure of how strongly a material opposes the flow of electric current. The unit of resistance is called ohms (Ω). The electric arc An arc is generated by electrons flowing across a gap between an electrode and a metal workpiece, the electrical energy being changed (converted) into heat and light. The arc is started by momentarily touching or scratching the electrode on the workpiece then withdrawing it about 3 or 4 millimetres to form a gap. The flow of electrons, that is the welding current, continues to flow across the small gap first formed as a spark, or arc. The small gap becomes electrically charged or ionized and current is able to continue to flow across the gap in the form of an arc. Power source V Ammeter A Welding lead Arc Electrode holder Electrode Voltmeter Basic power circuit for MMAW Workpiece TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 25 of 84

10 Review questions These questions have been included to help you revise what you have learnt in Topic 2 Basic electrical terms and definitions 1. Define the following electrical terms: Voltage: Current: 2. Label the parts indicated below associated with a basic MMAW power circuit. Power source V 3. Briefly explain how an electric arc is generated when MMAW. Multiple choice questions (Tick the box with the correct answer) 4. The unit of resistance in an electrical circuit is called: o ion o high frequency o ohm o electron 5. A material used as a conductor in MMAW electrode and return leads is: o carbon fibre o carbon steel o copper o reinforced rubber 6. Electricity is a form of energy associated with: o gravitational forces o arc radiation o expansion of resistors o movement of electrons A Page 26 of 84 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012