1. Manuals
  2. Brands
  3. TECH A V Manuals
  4. Welding System
  5. GMAW
  6. Learner manual

TECH A V GMAW Learner Manual

Gas metal arc welding
Hide thumbs
Table of Contents

Advertisement

Quick Links

Download this manual
GAS METAL ARC WELDING
(GMAW)
Learner Guide

Advertisement

Table of Contents
loading
Need help?

Need help?

Do you have a question about the GMAW and is the answer not in the manual?

Questions and answers

Summary of Contents for TECH A V GMAW

  • Page 1 GAS METAL ARC WELDING (GMAW) Learner Guide...

  • Page 2: Table Of Contents

    TABLE OF CONTENTS INTRODUCTION PAGE 1 LEARNERS INSTRUCTIONS (HOW TO USE THIS PROGRAMME) PAGE 2 PROGRAMME 1 - THE GMAW PROCESS INTRODUCTION PAGE 3 RESOURCE NOTES PAGE 4 SELF-TEST NO. 1 PAGE 12 GLOSSARY OF TERMS PAGE 14 PROGRAMME 2 - EQUIPMENT PARTS AND FUNCTIONS...

  • Page 3: Introduction

    OBJECTIVES: (PURPOSE OF THIS MATERIAL) This series serves to assist you, the "Learner", in achieving a "Learnership" in any of the engineering fields where GMAW welding is stated as being a "unit of learning". PURPOSE STATEMENT (WHAT YOU WILL LEARN) During this learning programme you will learn: o To describe basic GMAW welding processes.

  • Page 4: Learners Instructions (How To Use This Programme)

    LEARNERS INSTRUCTIONS (HOW TO USE THIS LEARNING AID) Step 1 - Read the Resource Notes and follow any written instructions. Step 2 - View the relevant video section (where applicable). Step 3 - Complete any "Self-Test Exercise" (as applicable). Step 4 - Perform a practical exercise (as applicable).
  • Page 5 In this section you will learn: o To describe the concept I principles of Gas Metal Arc Welding processes. o Describe/Identify by name, typical equipment constituting a GMAW system. o Explain in basic terms how MIG/MAG/FCAW processes operate. o Explain in basic terms the modes of metal transfer (Short arc, globular, spray and pulsed).

  • Page 6: Resource Notes

    (Shielded Metal Arc) will find the GMAW process a "pleasure" to use! Although the term GMAW has been used several times already in this text, you will rarely hear this in the "work-place". Other common terms used to describe this process include: o MIG or Metal Inert Gas.
  • Page 7 HOW DOES GMAW WORK? It is important that you understand the operating principles of your GMAW equipment as this knowledge will assist you to set-up and operate your equipment more efficiently. In any arc welding process metal parts are locally heated to "melting temperatures"...
  • Page 8 metal, and for the weld-process, is vital as a mistake could result in catastrophic damage, and possible loss of life. For this reason the "responsible welder" will seek advice on the correct wire type for any given task if he or she is in any doubt. As a rule the wire type is provided in a "welding specification"...
  • Page 9 Some flux-cored wires, known as "self-shielding electrodes", do not require additional shielding during the welding process. The most usual (common) gases used in GMAW processes are: o Argon -a fully inert gas -commonly used for welding aluminium.
  • Page 10 a weld-pool. This gas is used only with "ferrous metals" and, with the exception of FCAW welding, is mixed in small quantities with inert gases. o Oxygen -a reactive gas and used only in minute quantities for purposes of improving arc stability and heat transfer when welding steel using "spray transfer".
  • Page 11 INDUCTANCE CONTROL With short circuit transfer, the current rise, at the time of the short circuiting occurring may take place too quickly causing the electrode tip to explode. Some power sources include "inductance control" in the form of "tapings" to which the "work lead"...
  • Page 12 It is however difficult to weld steel "out of position" with spray transfer owing to the "excessive fluidity" of the weld-pool and the risk of "spill over". Metals with good heat dissipation ("conductivity") such as aluminium, can be welded out of position using spray transfer.
  • Page 13 Type or mix of welding gas. SAFETY AND PPE For most practical applications you must take the same precautions with GMAW welding processes as you would with SMAW (Stick welding) namely: o Always wear a welding helmet (mask or hood) when welding or when observing a weld in progress.

  • Page 14: Selftest No. 1

    What is "FCAW"? ___________________________________________________________ What makes a GMAW process different from Shielded Metal Arc welding? ___________________________________________________________ What is the "primary reason" for a "welding gas" in most GMAW processes? ___________________________________________________________ Which part of the welding equipment supplies the "welding current"? ___________________________________________________________...
  • Page 15 What 3 main types of "shielding gases" are used with MIG and MAG processes? i) _________________________________________________________ ii) _________________________________________________________ iii) _________________________________________________________ 10. What are the 3 modes of metal transfer? i) __________________________________________________________ ii) _________________________________________________________ iii) _________________________________________________________ 11. List 3 items of "personal protective equipment" that you should always use when welding.

  • Page 16: Glossary Of Terms

    Active Gas: A gas that will combine easily or readily with molten weld material. Carbon Dioxide and Oxygen are active gases. Air Cooled Gun: A GMAW welding gun used mainly for light duty work, The nozzle and contact tip are cooled by the flow of air and "shielding gas" surrounding them, These guns are rarely used where the welding current exceeds 200 amps.
  • Page 17 Flash: The bright intense arc, generated in Arc-welding processes, as seen by the human eye. Gas Metal Arc Welding (GMAW): the arc welding process that uses a continuously fed, consumable electrode in conjunction with a "shielding gas". (Also called MIG/MAG welding).
  • Page 18 Insulation: Any material that will not permit an electric current to pass through it. The handle surrounding the welding gun is made of "insulative-material". Lead: The cable, wire or "conductor" that carries electricity. In welding terms this is usually the "work lead" that returns the electricity from the work back to the "power source". Liner: The flexible tube through which the electrode passes between a "wire feeder"...
  • Page 19 Pull Gun: A welding gun that has an in-built wire-feeder that pulls the electrode-wire through the gun cable. Rated Output-Current: The maximum current or "load" that can be generated from a welding machine. Resistance: In electrical terms, the property of a material to "resist" (slow down) the flow of electricity through it.
  • Page 20 Wire: In GMAW terms this is the name used, by most "Welders", for the electrode-wire. Wire-Feeder: The device used to deliver the electrode-wire in a continuous action, to the weld area. Work piece: The material to be (being) welded. NOW MOVE ON TO PROGRAMME 2: EQUIPMENT - PARTS, FUNCTIONS AND PREPARATION".

  • Page 21: Part 1 - Equipment Parts And Functions

    EQUIPMENT - PARTS, FUNCTIONS AND PREPARATION PART 1 - EQUIPMENT PARTS AND FUNCTIONS In this section you will learn to identify by name, and describe the function/operation of: o A GMAW power source (Typical). o A Wire feeder (Typical). o A welding gun (Typical).

  • Page 22: Resource Notes

    DC output, and are of the CONSTANT VOLTAGE type. The welding current is most commonly set to "Reverse Polarity" or DCEP (electrode positive). There are many and various makes, types and sizes of GMAW machines available and the selection of a machine is normally based on the nature of the work to be performed.
  • Page 23 The most "conventional" (non-digital) feeders offer speed ranges between 2 M/min (70 inches/min) and 20 M/min (700 inches/min). There are two basic types of controllers namely, step type and infinite control. • A step type normally has 10 positions (notches or clicks) and (turning the dial clockwise) each notch increases the feed speed by 2 metres per minute.
  • Page 24 SPECIALISED EQUIPMENT Aluminium wire is very soft and is prone to sticking or jamming in a standard wire feeder. To get over this problem a second set of drive-rollers may be situated at the "gun end" of the cable. This design effectively provides a "push and pull" effort to the electrode-wire. WELDING GUN (INCLUDING CABLE) The purpose of the welding gun is: o Make electrical contact with the electrode.
  • Page 25 The electrode cable is connected to the power source output-connector. When the trigger is depressed on the gun the system is activated. Upon action the electrode wire is fed, from the wire-feeder, through a wire-liner and on through the gun via a "contact tip". The contact-tip, itself an electrical conductor (copper), makes contact with the "electrode cable"...
  • Page 26 ELECTRODE WIRE (TYPES AND SIZES) As earlier mentioned there are many and various types of electrode wires used in GMAW processes. Selection of a suitable electrode is usually based on factors such o Base metal type and composition. o Cleanliness of the base metal.
  • Page 27 TABEL 1 GMAW (Solid Wire for MIG and MAG) BASE METAL ELECTRODE TYPE Aluminium. ER1100, ER4043, ER5356. Copper and copper based alloys. ERCu, ERCuSi-A, ERCuAI-A1. Carbon steel. ER70S-3, ER70S-6. Low alloy steel. ER80S-B2, ER80S-D2. Stainless steel. ER308, ER308L, ER316, ER347.
  • Page 28 SELF TEST NO. 2.1 GENERAL EQUIPMENT AND CONSUMABLES INSTRUCTIONS Complete the following exercise without reference to your notes or the video. When you have completed the exercise check your answers/responses by: o Referring to the notes. o Reviewing the video material. o Asking your Instructor/Mentor.

  • Page 29: Part 2 - Welding Equipment Preparation

    What is the main purpose of "post flow"? ________________________________________________________ NOW MOVE ON TO PART 2 OF THE PROGRAMME: "WELDING EQUIPMENT PREPARATION". Back to Table of Contents...
  • Page 30 PROGRAMME 2 EQUIPMENT - PARTS, FUNCTIONS AND PREPARATION PART 2 - WELDING EQUIPMENT PREPARATION In this section you will learn how to: o Connect the power source to the wire feeder. o Prepare the gas supply to the welding station. o Prepare a welding gun and gun liner.
  • Page 31 IMPORTANT SAFETY NOTE: Make sure the machines' power switch is in the OFF position and that the machine is ISOLATED FROM THE MAIN SUPPLY before attempting any electrical connections or mechanical connections where rotating parts are involved! CONNECT THE POWER SOURCE AND WIRE FEEDER No matter which equipment you use, an external wire feeder unit must be connected to the power source in some way.
  • Page 32 o Attach the "supply hose connector" to the "outlet connector-nipple" on the regulator assembly. Again, use only the correct fitting spanner for this. If the hose has a "hose clamp" attached, then, using a screwdriver, check that the hose is secure by tightening the clamp-screw.
  • Page 33 Disconnect the welding gun cable (conduit) from the wire feeder and lay the cable onto a clean surface. Remove the wire-liner retainer nut and withdraw the liner from the conduit. (If you intend to retain the liner then coil it neatly and store it in a protective packet). Select the new liner according to type and length.
  • Page 34 The wire-reel, along with an adapter, is fitted onto the spindle in such a way that the wire is pulled off from the bottom of the reel. Take note of the precise mounting instructions offered by the machines' manufacturer. Make sure that the "reel retainer" is properly positioned to prevent the reel from working its way off the spindle.
  • Page 35 ALIGNMENT AND ADJUSTMENT OF ROLLS AND GUIDES. CORRECT PRESSURE & ALIGNMENT. CORRECT ALIGNMENT OF ROLLS AND GUIDES. MISALIGNED ROLLS. WIRE BENT DOWN - ADJUST HOUSING - DOWN. WIRE LOOSE. WIRE BENT UP - ADJUST HOUSING - UP. Back to Table of Contents...
  • Page 36 TENSIONING THE DRIVE ROLLS This step involves adjusting the top roll (pressure roll) to press against the electrode wire in order to provide a "slip free" feed of wire to the gun. Pressure is exerted onto the wire when the "pressure adjusting screw(s)", situated on the top roll(s) are tightened.
  • Page 37 NOW VIEW PART 2 OF VIDEO GMAW 2. THEN COMPLETE SELF -TEST NO. 2.2 ON THE NEXT PAGE. Back to Table of Contents...
  • Page 38 SELF TEST NO. 2.2 EQUIPMENT PREPARATION INSTRUCTIONS o Complete the following exercise without reference to your notes or the video. o Perform the tasks on the MIG/MAG equipment allocated to you by your Instructor: Connect the wire feeder to the power-source ensuring that all connections are made correctly according to the manufacturers' recommendations.

  • Page 39: Practical Evaluation - Exercise 2.2

    10. All "safety" precautions made before working with the wire feeder. 11. Work lead connected to machine and to welding bench. THIS CONCLUDES PROGRAMME GMAW-2. NOW MOVE ON TO PROGRAMME 3 ON THE NEXT PAGE. Back to Table of Contents...
  • Page 40 PROGRAMME 3 GAS METAL ARC WELDING PRACTICES AND PROCEDURES OBJECTIVES When you have completed this programme (module) you will be able to: Prepare and use a MIG/MAG power source to produce "Short-Circuit Transfer Mode" welds on steel work pieces. Prepare and use a MIG/MAG power source to produce "Spray Transfer Mode" welds on steel work-pieces.

  • Page 41: Resource Notes

    RESOURCE NOTES PROGRAMME 3 PART 1 - BASIC SKILLS In this programme you will be shown how to put your GMAW welding equipment to practical use. In practice the welder normally does not have to make too many decisions regarding the "welding procedure"...
  • Page 42 SHIELDING GAS PREPARATION Adjusting the shielding-gas delivery flow-rate and post flow. The following procedure is typical for most GMAW equipment. o Shut (close) the "flow-control valve" at the flow-meter. o Open the (cylinder) delivery-valve, slowly, by % turn maximum (see safety notes below).
  • Page 43 The next step will depend on your machine design. o Machines with a "Gas Purge Button" To activate (open) the gas control valve, push and hold in the "purge button". Gas will flow through the gun cable whilst the button is held.
  • Page 44 PREPARING THE WELDING GUN Prior to operating the welding gun there is one setting that needs to be made namely, the electrode-protrusion or "stick-out" as it is commonly known. Stick-out is the amount of electrode wire that should protrude from the contact-tip. This distance is important as it provides the correct conditions in which the electrode wire is pre- heated and it also produces the desired envelope of shielding gas over the weld-pool by ensuring that the gas-nozzle is maintained at the optimum distance from the work.
  • Page 45 Part 1 of the video. NOW VIEW PART 1 OF VIDEO GMAW-3 AND THEN PRACTICE HANDLING THE GUN IN YOUR WORK PLACE.

  • Page 46: Part 2 - Practical Exercises

    PROGRAMME 3 PART 2 - PRACTICAL EXERCISES EXERCISE NO.1 - SURFACE STRINGER-BEADS USING SHORT-ARC TRANSFER In this exercise you will be shown the following: o How to set the welding machines' parameters for "short-circuit transfer mode". o How to start the arc. o How to run a "surface bead".
  • Page 47 o Wire-feed speed, and o The type and mix of shielding-gas being used. For convenience sake the following guides will assist you to establish the "optimum settings". SETTING GUIDE FOR O.98MM WIRE. METAL THICKNESS WIRE SIZE mm WELD VOLTS WIRE FEED RATE APPROX.
  • Page 48 Therefore, as we require 18 volts to begin our exercise, we need only set the fine control to position number 2 (ADDING 1 VOLT TO THE MINIMUM) and leave the coarse control at its minimum (No.1) setting. SETTING THE WIRE-FEED SPEED Very simply, rotate the wire-feeder controller to the desired feed speed.
  • Page 49 RUN A SURFACE BEAD As soon as the arc is established, a weld-pool will form. The size of the weld pool is your main point of reference. The aim is to keep the weld pool diameter constant at about 3 to 4 times larger than the electrode diameter and this involves moving the gun along the "guide line"...
  • Page 50 SOME USEFUL TIPS One of the "difficulties" that most Learners experience when starting to use GMAW equipment is that of getting the two basic machine settings, voltage and wire feed speed, just right. As there are no "hard and fast rules" (as to the "correct settings") one has to rely on experience and, ones' natural senses.

  • Page 51: Practical Exercise No. 1

    PRACTICAL EXERCISE NO. 1 LAYING A BEAD ONTO STEEL PLATE USING "SHORT CIRCUIT TRANSFER MODE" INSTRUCTIONS o Obtain a piece of 3mm mild steel plate approximately 70mm x 150mm. o Clean both surfaces to remove all surface deposits, including rust and mill scale. o Scribe parallel "guide-lines", length-wise, onto the plate.

  • Page 52: Exercise No. 2

    Inspecting your weld. INTRODUCTION The purpose of this exercise is to offer you the experience in using your GMAW equipment to join two pieces of metal using "dip transfer". This is probably the commonest type of operation you will experience in the work place.
  • Page 53 INSPECT THE WORK A "satisfactory weld" will have the following features: o Even and consistent width along the full length. o No undercutting on the edges (toe) of the bead. o Evenly spaced "C-shaped ripples". o A 1.5 - 2mm "raised weld-face" (Convex reinforcement). o On the reverse side there will be a thin and even bead of "penetration filler".

  • Page 54: Practical Exercise No. 2

    PRACTICAL EXERCISE NO. 2 WELDING A "BUTT-JOINT" USING "SHORT-CIRCUIT TRANSFER" INSTRUCTIONS For this exercise you will require: o 2 x Pieces of 3mm mild-steel flat plate cut to approximately 70mm x 150mm. o O.98mm (E70S-3) Electrode wire Procedure. o Set up your MIG machine as you did for exercise No.1 (Use same optimum settings). o Clean the weld-zone of both plates, including the root faces.

  • Page 55: Exercise No. 3

    EXERCISE NO. 3 SET UP MACHINE TO DELIVER "SPRAY TRANSFER MODE" AND RUN SURFACE BEADS In this exercise you will be shown the following: o How to set the welding machines' parameters for "spray-transfer mode". o How to produce surface beads on thick mild-steel plate using the "spray-transfer mode".
  • Page 56 o Set your machines' voltage and wire feed speed, initially, to the "lower end" of the suggested figures given above (relative to the wire size). o Use Welding Chart -1 (at end of this book) if you wish to check "amps / wire -feed" relationship.

  • Page 57: Practical Exercise No. 3

    PRACTICAL EXERCISE NO. 3 RUN SURFACE BEADS WITH "SPRAY TRANSFER MODE" For this exercise you will require the following: o Pieces of 8 mm mild-steel plate approximately 50mm x 150mm. o 1.2mm (E70S-3) Electrode wire. o Shielding gas mix containing at LEAST 80% Argon. INSTRUCTIONS Follow the typical procedure to produce surface beads on your work-pieces: o Set up your MIG machine to obtain "spray transfer".

  • Page 58: Exercise No. 4

    EXERCISE NO. 4 FILLET WELD WITH SPRAY TRANSFER INTRODUCTION For purposes of demonstration we will use Spray Transfer mode to perform a "fillet weld". The primary reason for this exercise is to offer you experience in using spray transfer to effect an actual join.

  • Page 59: Practical Exercise No. 4

    PRACTICAL EXERCISE NO. 4 FILLET WELD USING "SPRAY TRANSFER" MODE INSTRUCTIONS Follow the procedure below to produce a fillet-weld in a Lap -Joint. MATERIAL (CONSUMABLE) o 2 Pieces of 8mm m/s plate, 50mm x 150mm (approximately). o Use 1 ,2mm solid filler wire (ER 70S -3). o Shielding gas -Argon (min 80%).

  • Page 60: Conclusion

    IN CONCLUSION SHUTTING DOWN To conclude this basic GMAW series we must spend a few moments on the topic of how to correctly close down your equipment. The main focus is upon safety, however it is also a matter of "good working practice" to ensure that you leave your equipment in proper working condition and ready for the next operator who needs to use it.

  • Page 61: Some Useful Gmaw Tips

    THAT COMPLETES THIS MODULE ON THE SUBJECT OF GMAW. ALWAYS WORK SAFELY AND REMEMBER "PRACTICE MAKES PERFECT".

  • Page 62: Welding Chart

    WELDING CHART-1 WELDING CURRENTS / WIRE - FEED SPEEDS FOR CARBON - STEEL ELECTRODES Back to Table of Contents...

Table of Contents