1. GMAW (MIG Welding) SECTION OVERVIEW:
Section Overviews are provided on the introductory slides at the front of each topical area to explain the intended use for the slides included in the section.
Slide numbers are included on the Section Overview slides for easy reference when preparing for delivery of the slide content.
TEACHER NOTES:
Teacher Notes are included on the Section Overview slides as a reference tool when making class preparations.
Suggested Activities are included as ideas for teachers to use to help students gain practical experience with the welding content. However, these are designed to be supplemented by each teacher based on local program needs.
Slides have been developed to incorporate content information regarding performance standards from the American Welding Society (AWS) and the National Academic Standards for English, Science, and Math.
INDIVIDUAL LESSON NOTES ARE AVAILABLE IN LESSON PLAN FACILITATOR’S GUIDE
GMAW
(MIG Welding)

2. GMAW Unit Topics
During this overview, we will discuss the following topics:
Safety
GMAW Basics
Equipment Set-Up
Welding Variables
Process Advantages and Limitations
AWS Connection
National Academic Standards Connection
SECTION OVERVIEW:
This slide is meant to start generating conversation and thoughts about content to be covered in this lesson.
TEACHER NOTES:
Bulleted information on topical areas is provided to lead class discussion on areas which are to be covered in the training.

3. Unit Objectives
Upon successful completion of the GMAW Unit of Study, you will have learned about:
Properly protecting yourself and others while welding
Setting up and operating GMAW equipment
Striking and maintaining an arc
Welding in four positions using various electrodes
Weld Inspection
The AWS electrode classification system
Taking the next step to becoming a certified welder
SECTION OVERVIEW:
This slide is included to explain the objectives of this unit of study.
TEACHER NOTES:
Teachers could use this opportunity to give a high-level overview of the importance and application of GMAW welding in today’s society.

4. GMAW Safety SECTION OVERVIEW:
The next few slides are meant to point out safety requirements when using the GMAW process.
TEACHER NOTES:
Slides 4-7: Bulleted information on topical areas is provided to lead class discussion on important areas of safety to be practiced in the GMAW welding environment.
To download your own copy of ‘Safety in Welding, Cutting and Allied Processes’ (ANSI Z49.1) go to:
To download your own copy of Lincoln Electric’s Arc Welding Safety (E205) document go to:
To order copies of Lincoln Electric’s Arc Welding Safety (E205) document and poster (E201) go to: (Quick Link: Literature Request)
MSDS can be obtained from Lincoln Consumable packaging, online at (Quick Link: MSDS) or by calling
For a free DVD on Welding Safely, submit order form in the back of the Lesson Plan Facilitator’s Guide (shipping and handling charges apply).
See Facilitator’s Guide for more information on welding hazards such as Fumes and Gases and Electrical Shock.

5. GMAW Safety
‘GMAW Safety’ is supplemental and does not replace the information found in ‘Arc Welding Basics’
Understand and follow all safety precautions listed in ‘Safety in Welding, Cutting and Allied Processes’ (ANSI Z49.1), and Arc Welding Safety (E205)
Understand and follow all warning labels found:
On welding equipment
With all consumable packaging
Within instruction manuals
Read Material Safety Data Sheets (MSDS)
If you ever have a question about your safety or those around you,
PLEASE ASK YOUR INSTRUCTOR!

6. GMAW Safety Fumes and Gases can be dangerous
Keep your head out of the fumes
Use enough ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and the general area
Local exhaust and mechanical ventilation can be used without reducing weld quality
Electric Shock can kill – to receive a shock your body must touch the electrode and work or ground at the same time
Do not touch the electrode or metal parts of the electrode holder with skin or wet clothing
Keep dry insulation between your body and the metal being welded or ground
The coil of wire is ‘electrically hot’ when the trigger is pulled
Arc Rays can injure eyes and skin -Choose correct filter shade (See chart below)
** Information taken from ANSI Z49.1:2005**

7. GMAW Safety
REMEMBER – Gas Cylinders require SPECIAL safety precautions
Cylinders must be secured in an upright position
Cylinders should be located in an area away from arc welding, cutting, heat, sparks, and flame
Refer to ‘Safety in Welding, Cutting, and Allied Processes’ (ANSI Z49.1) or Arc Welding Safety (E205) for more information on the handling of gas cylinders

8. GMAW Principles SECTION OVERVIEW:
These slides are meant to lead into the discussion on the components involved with GMAW welding.
TEACHER NOTES:
Slides 8-16: When using these slides, discussion could include:
With semi-automatic MIG welding, the electrode wire is fed through a welding gun controlled by the operator. The operator starts the arc and controls the puddle. In automatic MIG welding, a robot or automated machine makes the weld.
An arc digs into the base metal much like water from a nozzle on a garden hose digs into the earth. (The flow of the water is like welding current and water pressure is similar to voltage)
Molten metal forms a molten pool or crater and tends to flow away from the arc while cooling and solidifying.
A continuous even flow of shielding gas is needed to protect the molten weld metal from atmospheric contaminants such as oxygen and nitrogen. The shielding gas comes from a gas cylinder and flows through the gun and cable assembly, through the gas nozzle, and into the welding zone.

9. GMAW is the most widely used arc welding process in the United States
GMAW Definition
GMAW stands for Gas Metal Arc Welding
GMAW is commonly referred to as MIG or Metal Inert Gas welding
During the GMAW process, a solid metal wire is fed through a welding gun and becomes the filler material
Instead of a flux, a shielding gas is used to protect the molten puddle from the atmosphere which results in a weld without slag
GMAW is the most widely used arc welding process in the United States

10. GMAW Circuit Three things happen when the GMAW gun trigger is pulled:
The wire electrode begins to feed
The circuit becomes electrically ‘hot’
Current flows from the power source through the gun cable, gun, contact tip to the wire and across the arc. On the other side of the arc, current flows through the base metal to the work cable and back to the power source
Shielding gas flows through the gun and out the nozzle

11. GMAW Components Let’s look a little closer at the GMAW process 4 5 2 1
Travel direction
Generally, drag on thin sheet metal and push on thicker materials
Shielding Gas 4
Solidified Weld Metal
Electrode 5 2
Arc 1 3
Weld Puddle

12. 1 - Electrode A GMAW electrode is: A metal wire
Fed through the gun by the wire feeder
Measured by its diameter
GMAW electrodes are commonly packaged on spools, reels and coils ranging from 1lb to 1000lbs

13. 2 - Arc
An electric arc occurs in the gas filled space between the electrode wire and the work piece
Electric arcs can generate temperatures up to 10,000°F

14. This is what the welder watches and manipulates while welding
3 - Weld Puddle
As the wire electrode and work piece heat up and melt, they form a pool of molten material called a weld puddle
This is what the welder watches and manipulates while welding
.045” ER70S-6 at 400 ipm wire feed speed and 28.5 Volts with a 90% Argon/ 10% CO2 shielding gas

15. GMAW welding requires a shielding gas to protect the weld puddle
Shielding gas is usually CO2, argon, or a mixture of both
The gauges on the regulator show gas flow rate and bottle pressure

16. 5 - Solidified Weld Metal
The welder “lays a bead” of molten metal that quickly solidifies into a weld
The resulting weld is slag free
An aluminum weld done with the GMAW process

17. Application Activity SECTION OVERVIEW:
This slide reviews what has been learned about the GMAW process.
TEACHER NOTES: (Explanation of Activity)
Slide 17-18: After having discussed the parts included on this slide, students will take a quiz as an application activity.
For the activity, have participants work individually and mark 1-5 on a piece of paper.
Explain that this activity is meant to check student understanding of GMAW before beginning to apply the process in the lab.
Project slide on the screen and have each student fill in the blanks on a piece of paper to be turned in. Collect papers and discuss.
Answers to the Application Activity are:
1. Electrode
2. Arc
3. Weld Puddle
4. Shielding Gas
5. Solidified Weld Metal

18. GMAW Components Application Activity
Let’s review the GMAW process
1 __________
2 __________
3 __________
4 __________
5 __________
Travel direction
Generally, drag on thin sheet metal and push on thicker materials 4 5 2 1 3

19. Equipment Set Up SECTION OVERVIEW:
These slides explain how to set-up the equipment for GMAW and covers process variables.
TEACHER NOTES:
Slides 19-21:
For welding procedure recommendations see:
The Lesson Plan Facilitator’s Guide
Lincoln Electric’s GMAW Welding Guide -
The inside of a Lincoln Electric combination wire feeder/ welder.
Check the gas nozzle. Turn the gas supply on. If adjustable, set for cubic feet per hour (7 to 10 l/min.) under normal conditions increasing to as high as 35 CFH (17 l/min) in drafty and/or slightly windy conditions. The liner and contact tip should match that of the electrode diameter being used.
The work clamp must be grounded to the work piece. Be sure to make a good connection.

20. GMAW Equipment Set Up Connect work clamp Select electrode a. Type
b. Diameter
3. Select shielding gas
4. Turn power supply on
5. Adjust machine output
a. Wire feed speed
b. Voltage
6. Adjust gas flow rate
Why would GMAW be a better choice than SMAW for this job?

21. GMAW Process Variables
Welding variables
Wire Feed Speed (WFS)
Voltage
Operator controlled variables
Travel speed
Gun angles
Contact tip to work distance (CTWD)
Gas flow rate
What is the relationship between WFS and amperage?

22. Striking an Arc and Making a Weld
SECTION OVERVIEW:
These slides discuss striking an arc and making a weld using the GMAW process.
TEACHER NOTES:
Slides 22-26: Teacher might want to discuss …
Once the arc has been established, maintaining the correct contact tip to work distance (CTWD) becomes extremely important. The CTWD should be approximately 3/8 to ½ inch (10-12 mm) long. The easiest way to tell if CTWD is right length is to listen to the sound.
If the CTWD is too short the wire electrode can fuse to the contact tip. It also causes the arc voltage to raise resulting in a flat bead shape, increase in spatter and possible undercut.
If the CTWD is too long the electrode can stub out. It also causes the arc voltage to drop resulting in a ropey and convex bead, increase in spatter and possible loss of gas shielding.

23. Position the gun over joint
Striking an Arc
Position the gun over joint
Position the face shield to protect eyes and face
Pull the gun trigger and begin welding
What are some things to consider before striking an arc?

24. Laying a Bead
Maintain a Contact Tip to Work Distance (CTWD) of 3/8” to 1/2”
Use a uniform travel speed
Most Importantly – Watch the Puddle!
The appearance of the puddle and ridge where molten metal solidifies indicates correct travel speed. The ridge should be approximately 3/8” (10 mm) behind the wire electrode.
Most beginners tend to weld too fast resulting in a ropey bead which means SLOW down!

25. Fill the Crater Fill the crater by pausing or using a slight back step
Release gun trigger and pull gun away from the work after the arc goes out
Large craters can cause weld cracking
Crater cracks cannot be tolerated on NASCAR radiators.

26. Restarting a Bead
Restart the weld bead by back stepping into the last weld’s crater and then continue moving forward
This technique should result in a seamless transition from one weld to the next 1
2 Back step

27. Modes of Metal Transfer
SECTION OVERVIEW:
These slides discuss two conventional modes of metal transfer: short arc and spray arc
TEACHER NOTES:
Slides 27-31:
Short Arc Transfer
The wire shorts to the base material, the molten metal is pinched off and transferred to the weld puddle.
Common gas mixtures for short arc: 100% CO2 or 75% Argon/ 25% CO2
Typical applications include thin materials, out of position welding, joints with poor fit up, root pass on pipe and when using 110V welders.
Axial Spray Arc Transfer
Very high currents are used in axial spray arc transfer (or spray arc).
The current level must be above the transition level and the shielding gas must contain at least 80% Argon.
A point forms at the end of the electrode and fine droplets of molten metal ‘spray’ across the arc. The droplets are equal to or smaller than the electrode diameter and are directed axially in a straight line to the weld puddle.
Typical applications include thick materials, flat and horizontal welding, structural fabrication, heavy machinery and aluminum welding.
For more information on the conventional modes of metal transfer see the GMAW Lesson Plan Facilitator’s Guide and Lincoln Electric’s free GMAW Welding Guide (

28. Modes of Metal Transfer
GMAW is a process that features several distinctive, individual methods and types of metal transfer
The mode of metal transfer is determined by a number of welding variables
Voltage
Amperage
Shielding Gas
By changing one or more variables, you can go from one metal transfer mode to another

29. Modes of Metal Transfer
Two common conventional modes of metal transfer are:
Short arc
Axial spray arc
The application, joint design, base material thickness, and properties determine the appropriate mode to use
Typical short arc application
Typical axial spray arc application

30. Short Arc Transfer In short arc transfer…
The arc is initiated and a droplet is formed on the end of the wire
The wire touches the work piece and produces a short circuit
The droplet is then transferred to the weld puddle

31. Axial Spray Arc Transfer
In axial spray arc transfer …
Very high currents are used
A point forms at the end of the electrode and the fine droplets
The puddle is very fluid making out of position welding difficult

32. Troubleshooting Welds
SECTION OVERVIEW:
The next slide explains about troubleshooting welds.
TEACHER NOTES:
Slide 32-33: Corrective actions for common GMAW problems:
Porosity
Check for proper gas flow/ block any winds or drafts
Clean joints from moisture, paint, etc.
Check for proper WFS and Voltage settings
Decrease CTWD, drag angle, and travel speed
Ropey and Convex
Check or reset WFS & Volts (increase voltage first)
Decrease CTWD, travel speed, and drag angle (push angle)
Excessive Spatter
Check and reset WFS and Volts
Increase drag angle
Decrease CTWD and travel speed
Eliminate Stubbing
Check or rest WFS & Volts (increase voltage first)
Decrease CTWD

33. Troubleshooting Welds
GOAL - Make Good Welds
Eliminate Porosity
Eliminate Ropey Convex bead
Eliminate Excessive Spatter

34. Advantages and Limitations
SECTION OVERVIEW:
This section is meant to lead into a discussion regarding the advantages and limitations of the GMAW welding process.
TEACHER NOTES:
Slides 34-36:
Advantages
High operating factor: The welder does not have to stop and clean slag or change electrodes.
Easy to learn: GMAW is easier to learn than Stick welding
Clean process with little or no slag and spatter - High efficiency (93-98%)
Welds can be made on a wide variety of metals and alloys.
Can be done in all welding positions
Disadvantages:
Less portable – Gun lengths are often only 15 feet long.
More expensive due to higher equipment price than SMAW and the need for a gas bottle.
Shielding gas can be blown away by winds so GMAW may require special precautions when welding outdoors or in drafty areas.
In spray arc transfer - the process radiates a lot of heat
Difficult to use in out of position joints
For more information on GMAW consumables and gases, see the Lesson Plan Facilitator’s Guide or GMAW Welding Guide available through Lincoln Electric

35. Advantages of GMAW High operating factor Easy to learn Limited cleanup
Use on many different metals: stainless steel, mild (carbon) steel, aluminum and more
All position
Great for home use with 115V and 230V units

36. Limitations of GMAW
Less portable with shorter gun lengths (15 foot guns)
GMAW equipment is more expensive than SMAW equipment
External shielding gas can be blown away by winds
High radiated heat
Difficult to use in out of position joints

37. AWS Classification of GMAW Electrodes
SECTION OVERVIEW:
This section is meant to lead into a discussion about the AWS Classification of GMAW Electrodes
TEACHER NOTES:
Slides 37-38
For more information on the AWS classification of GMAW electrodes see Lincoln Electric’s free ‘GMAW Welding Guide’ -

38. AWS Classification of GMAW Electrodes
ER70S-X
Electrode
Rod
70,000 psi Min. Tensile Strength
Solid
Chemistry, Amount of Deoxidizers (Silicon, Manganese and/or Aluminum, Zirconium and Titanium) X=2,3,4,6,7 or G

39. Lesson Plans SECTION OVERVIEW:
These slides are used for practicing lesson content in the lab setting.
TEACHER NOTES:
Slides 39-48: When using these slides, reference information included in the Facilitator’s Guide.
Recommended equipment – Only one of the single process or multi-process machines is required to complete the lesson.

40. GMAW Lesson #1
Objective: To run a stringer (straight) bead using short arc transfer and to fill the crater
Equipment:
Single Process - Constant Voltage Power Source & Wire Feeder
Power MIG 215 or Power MIG 255C
Multi-Process
Composite: Power MIG 350 MP
Combination: V-350/ LF-72 package
Material:
Mild Steel Plate – 3/16” or thicker
.035” SuperArc L-56 (ER70S-6)
100% CO2 or 25% CO2/ 75% Argon blend shielding gas

41. GMAW Lesson #2
Objective: To make a fillet weld on a lap joint in the horizontal position (AWS position 2F)
Equipment:
Single Process - Constant Voltage Power Source & Wire Feeder
Power MIG 215 or Power MIG 255C
Multi-Process
Composite: Power MIG 350 MP
Combination: V-350/ LF-72 package
Material
Mild Steel Plate – 10 gauge
.035” SuperArc L-56 (ER70S-6)
100% CO2 or 25% CO2/ 75% Argon blend shielding gas 2F

42. GMAW Lesson #3
Objective: To make a fillet weld on a tee joint in the horizontal position
(AWS position 2F)
Equipment:
Single Process - Constant Voltage Power Source & Wire Feeder
Power MIG 215 or Power MIG 255C
Multi-Process –
Composite: Power MIG 350 MP
Combination: V-350/ LF-72 package
Material:
Mild Steel Plate – 10 gauge
.035” SuperArc L-56 (ER70S-6)
100% CO2 or 25% CO2/ 75% Argon blend shielding gas 2F

43. GMAW Lesson #4
Objective: To make a fillet weld on a lap joint in the vertical position welding down (AWS position 3FD)
Equipment:
Single Process - Constant Voltage Power Source & Wire Feeder
Power MIG 215 or Power MIG 255C
Multi-Process –
Composite: Power MIG 350 MP
Combination: V-350/ LF-72 package
Material:
Mild Steel Plate – 10 gauge
.035” SuperArc L-56 (ER70S-6)
100% CO2 or 25% CO2/ 75% Argon blend shielding gas
3FD

44. GMAW Lesson #5
Objective: To make a fillet weld on a tee joint in the vertical position welding down (AWS position 3FD)
Equipment:
Single Process - Constant Voltage Power Source & Wire Feeder
Power MIG 215 or Power MIG 255C
Multi-Process –
Composite: Power MIG 350 MP
Combination: V-350/ LF-72 package
Material:
Mild Steel Plate – 10 gauge
.035” SuperArc L-56 (ER70S-6)
100% CO2 or 25% CO2/ 75% Argon blend shielding gas
3FD

45. GMAW Lesson #6
Objective: To make a butt weld with a gap in the vertical position welding down
Equipment:
Single Process - Constant Voltage Power Source & Wire Feeder
Power MIG 215 or Power MIG 255C
Multi-Process –
Composite: Power MIG 350 MP
Combination: V-350/ LF-72 package
Material:
Mild Steel Plate – 10 gauge
.035” SuperArc L-56 (ER70S-6)
100% CO2 or 25% CO2/ 75% Argon blend shielding gas 3G

46. GMAW Lesson #7
Objective: To make a fillet weld on a tee joint in the overhead position (AWS position 4F)
Equipment:
Single Process - Constant Voltage Power Source & Wire Feeder
Power MIG 215 or Power MIG 255C
Multi-Process –
Composite: Power MIG 350 MP
Combination: V-350/ LF-72 package
Material:
Mild Steel Plate – 10 gauge
.035” SuperArc L-56 (ER70S-6)
100% CO2 or 25% CO2/ 75% Argon blend shielding gas 4F

47. GMAW Lesson #8 2F Objective: To make a three pass fillet weld on a tee
joint in the horizontal position (AWS position 2F)
Equipment:
Single Process - Constant Voltage Power Source & Wire Feeder
Power MIG 215 or Power MIG 255C
Multi-Process –
Composite: Power MIG 350 MP
Combination: V-350/ LF-72 package
Material:
Mild Steel Plate – ¼”
.035” SuperArc L-56 (ER70S-6)
100% CO2 or 25% CO2/ 75% Argon blend shielding gas 2F

48. GMAW Lesson #9
Objective: To run a horizontal fillet weld on a tee joint using axial spray transfer (AWS position 2F)
Equipment:
Single Process - Constant Voltage Power Source & Wire Feeder
Power MIG 225C
Multi-Process –
Composite: Power MIG 350 MP
Combination: V-350/ LF-72 package Material:
Mild Steel Plate – ¼”
.045” SuperArc L-56 (ER70S-6)
90% Argon/ 10% CO2 blend shielding gas 2F

49. AWS Connection SECTION OVERVIEW:
The next few slides discuss the connection of this unit with AWS and the certification process.
TEACHER NOTES:
Slide 49-50: Content included in this unit of study is designed to be used by interested students as a building block in the learning process if interested in pursuing a certification program

50. American Welding Society (AWS) Connection
The GMAW unit of study covered information related to the following AWS requirements for certification:
Setting up for GMAW operations on carbon steel
Operating GMAW equipment on carbon steel
Making GMAW fillet welds on carbon steel

51. English, Math, and Science Connection
SECTION OVERVIEW:
The next slide discusses how the content covered in the welding unit is applicable to English, Math, and Science classes.
TEACHER NOTES:
Slides 51-52: This slide contains information regarding how this welding unit of study relates to the National Academic Standards.

52. National Academic Standards Crosswalk
This unit covered academic content listed in the National Academic Standards as follows:
NM-MEA : Understands measurable attributes of objects and the units, systems, and processes of measurement
NM-PROB.CONN.PK-12.3: Recognizes and applies mathematics in contexts outside of mathematics.
NS-PHYSICAL SCIENCE: (Understands) structure and property of matter
NS-PHYSICAL SCIENCE: (Understands) chemical reactions
NLA-STANDARD 3: Uses grammatical and mechanical conventions in written compositions
NLA-STANDARD 10: Understands the characteristics and components of the media