Lesson 6 – Auto Welding – Part 2. Below are the videos included in this lesson. Click on the video to watch.
MIG Basics
Set-Up
Replace Bedside
Plug Weld
Butt Weld
How To Use Drill
Seam Buster
Repair Flanges
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MIG Basics
This video tutorial discusses the different parts of a MIG Welder. Starting with the gun,it consists of: gun, nozzle, contact tip, gun liner and welding wire. -
Set-Up
Students demonstrate how to replace a shielding gas cylinder and wire on a MIG Welding Machine -
Replace Bedside
This is a weld-on panel, which involves cutting or drilling out spot welds and welding the new part on. Below is a brief list of the steps we took for this procedure. -
Plug Weld
Students recorded for http://ABRN.com Our collision repair technology program partnered with ABRN to provide ABRN HOW2 Tip. This is a digital edition highlighting collision repair training tips. This ABRN How2 is how to performa plug weld using a MIG welder. -
Butt Weld
This DIY video demonstrates how to perform a butt weld on thinner metal, such as welding car panels in auto body repairs. Students demonstrate how to perform a butt weld, which is a student led demonstration. -
How To Use Drill
In this video we are demonstrating how to use a drill and drill bits to remove spot welds in this 1966 Mustang. We are removing a quarter panel and drilling all of the spot welds to remove it. There are other methods for removing spot welds, but this is an easy method to use and most people have a drill and drill bits. -
Seam Buster
This video demonstrates how to use a seam buster to remove weld on panels. In this video we were using it to remove quarter panel on a 1966 Mustang. -
Repair Flanges
This video demonstrates how to clean and repair flanges before installing a new panel
Welding Essentials: Mastering the Art and Science of Joining Metals
Learning Objectives
- Identify risks to computer components and glass during welding and appropriate precautions.
- Compare MIG welding with other methods (arc, oxy/acetylene, TIG) regarding advantages and skill requirements.
- Differentiate between reverse and straight polarity and determine the appropriate setting for tasks. – Explain the short circuit transfer technique and its application for thin sheet metals.
- Recognize the role of shielding gas and identify the recommended mixtures and pressure settings.
- Evaluate the impact of travel speed and angle on weld quality.
- Practice and assess push vs. pull welding techniques for personal preference.
Computer Components
Another consideration when working on cars is the computer components. Suppose they are within 12 inches of the area you are welding. In that case, you need to remove those components to prevent damaging them when welding.
Cover Glass
Before welding, cover glass or anything else that can become damaged during the welding process with a welding blanket or spark resistant paper. Even grinding can pit the glass, so keep the glass covered with welding blankets or some protective sheeting until the repairs have been completed.
Advantages of Using a MIG Welder
The advantage of MIG welding over oxy/acetylene welding is a smaller heat zone. It does not heat the metal as much as an oxy/acetylene torch does.
Skill Level
MIG welding requires fewer skills than arc, oxy/acetylene, or TIG welding and is a fast and effective welding process.
Polarity
MIG welders have two different polarities. You have a reverse polarity, which is used in auto body work. This is where the electrode that the wire is coming out of is the positive, and the work clamp is your negative. This setting uses welding wire and a shielding gas. The other type is straight polarity, which is used with flux core wire. This setting requires flux core wire, but no shielding gas is needed. Flux core wire is not recommended for thinner sheet metals and is not used in auto body repair. You need to be certain the welder is set on the correct polarity setting for the type of welding you will be performing.
Short Circuit Transfer
Different types of welding can be performed with a MIG welder, but we are going to focus on the short circuit transfer, as this works best on thinner sheet metals. When welding, the electrode (wire) coming out of the welding gun hits the metal being welded, which makes a circuit. When the circuit is made, it shorts out. This happens about 90 to 230 times per second when using .023 welding wire as used for welding thin metals. As mentioned, the recommended wire diameter is .023, and the recommended wire type is ER70S-6. The ER stands for electrode wire; the 70 is the tensile strength, which is approximately 70,000; and the S stands for solid wire. The “6” is the chemical makeup of the wire that you are using.
Shielding Gas
Whenever using solid wire, you will need a shielding gas. You can use CO2 straight for some of the thicker metals. Still, in auto body, a mixture of 75% argon and 25% CO2 is recommended and provides the smoothest weld for the thinner metals.
Shielding gas helps protect the weld, keeps the oxygen out, and helps to create a nice, clean weld. Without the shielding gas, the weld will have a lot of pinholes, called porosity, and will not have good penetration.
The shielding gas should be set anywhere from 20 to 30 psi at the regulator. 20 psi works well for indoors, such as a body shop or garage.
First, the wire feeds through the liner from the welding machine. Then the wire feeds through the gun, and through the tip, which is attached to the end of the gun. The liner is covered with a hose, which provides a path for the shielding gas to pass through. At the end of the gun, a nozzle covers the tip and directs the shielding gas to the surface being welded.
Chart Showing Recommended Supplies For Sheet Metal
Download This Chart in PDF For Print at www.CollisionBlast.com/MIGWeldingChart
Travel Speed
Travel speed is the speed at which you move the gun when welding. Travel speed is essential, as this can affect the quality of the weld produced. If the travel speed is too fast, you will not achieve proper penetration. To visually identify this problem, the weld will sit on top of the metal in a narrow bead. Again, the weld will not have proper penetration.
If the travel speed is too slow, you are going to burn holes in the metal, which is not hard to do when working with thin metals, such as metal used on cars and pickups.
Travel Angle
It is also essential to have the correct travel angle. The travel angle is the angle at which the gun is angled towards the direction of gun travel. The recommended travel angle is usually between 5 – 30 degrees depending on the type of weld being performed. Travel angle greater than 25 degrees may lead to more spatter, less penetration, and general arc instability.
Work Angle
The work angle is the angle at which the gun is to the joint being welded. The recommended angle is usually between 45 and 90 degrees. Depending on the type of weld being performed.
Push and Pull Techniques
The gun can be pushed towards or pulled away from the weld location during welding. There is no right or wrong method when it comes to push or pull. The push method can produce better penetration; however, I prefer the pull method. Most students prefer this method as well. Try both push and pull methods and determine which one works best for you.
Stick Out
Stickout is the distance between the contact tip and the metal being welded. When welding thin metal with .023 wires, as used for auto body repair, the recommended stick out is 1/4 inch to 1/2 inch. Stickout can also affect the penetration of the weld. The closer the contact tip is to the weld surface, the more penetration you will gain, and the further away the contact tip is from the metal, the less penetration the weld will have.
This is what is referred to as chicken scratch, where the weld splatter is balled up all over the weld area.
Three Weld Positions
When welding on cars, you may find yourself in many different positions. For instance, you may have to weld in a flat, vertical, or overhead position. Flat welds are generally the easiest welds to produce. Therefore, try to position yourself or the piece being welded so that a flat weld can be performed flat. However, this cannot always be done, so other positions need to be practiced. The vertical or horizontal weld is the second easiest weld to perform, but there will be some gravity to deal with. The puddle will try to fall, which makes this a little more complicated. The overhead weld is the most challenging position to weld. With this position, gravity is working against you, as the puddle tends to drop straight down. This weld also creates more sparks and slag that can fall and burn you and clog your nozzle. Personal Protective Equipment should always be worn to prevent burns, but an overhead weld requires additional safety concerns.
To reduce the amount of slag and splatter clogging your nozzle, you may need to decrease your heat setting slightly.
Securing the Parts Being Welded
Before you start welding, you will need to secure the parts tightly together. This can be done using self-tapping screws, vice grips, c-clamps, tack welds, etc. It may even be necessary to hammer any gaps together to ensure that you are not trying to weld gap edges together.
Setting the Welding Machine
The setting will depend on the wire size you are using and the thickness of the metal being welded. If you are unsure of the metal thickness, you can use a thickness gauge to measure it. Once you know these factors, look at a chart for the welder you are using to determine the correct setting. For example, .023 wire, 20 gauge steel, and the shielding gas may recommend the heat to be set at D and the wire speed to be set at 3. Every brand of welding machine will have different indicators for setting heat and wire speed, but this will all be detailed on the chart. Once the settings are set to the recommended settings, you are ready to start fine-tuning the welding machine to fit your specific welding technique. The recommended settings are a good starting place, but every person will need to fine-tune the machine when performing weld tests.
How To Fine-Tune a Welding Machine
There are three basic ways to fine-tune a welding machine to fit your specific welding techniques. The first and most popular is to adjust the welder by sound. If the sound is inconsistent and poppy, your wire feed is probably too fast or the heat setting is too low. If the sound is hissing and there is no buzz at all, the wire feed is too slow or the heat is too high. The correct sound is a consistent buzz, much like bacon frying.
You can also look at the light the welder produces (of course, with a welding helmet on). If the light is inconsistent or looks like a strobe light, your wire speed is too fast or your heat is too low. As with sound, you want the light to be more constant.
The third way to adjust the welding machine is by feel. If you feel the gun pushing away from the surface being welded, this is a hint that the wire speed is too fast. Therefore, many minor adjustments are needed to fine-tune the welding machine.
Bird Nest
One problem you may have when welding is called a bird nest. This is when the wire becomes balled up and tangled inside the machine. This may be due to the wire accidentally being welded to the contact tip. As the rollers continue to move the wire through, it becomes balled up in the machine instead of coming out of the contact tip. The only way to correct this problem is to stop, unplug the welder, remove the wire from the liner, and run the new wire through the rollers and liner again. As mentioned, this may be caused by the wire welded to the tip, too much tension on the rollers, the liner becoming clogged, the wrong diameter contact tip, or other reasons.
Heat Management
A concern we have in working on thin metals that is not a concern with other types of welding is heat management. Thin metals will become warped when overheated. If metal becomes warped, it can be tough to repair. Therefore, every effort should be taken to prevent the metal from becoming warped. Not only is warping a concern, but many of the metals used on cars are high-strength steel. Suppose some of these types of metals are overheated. In that case, the metal will be severely weakened, which will result in safety issues.
Triggering
Triggering is a technique used to prevent overheating the metal. This is the process of holding the trigger to create a weld nugget, then letting off the trigger to allow the metal to cool off. Once the metal has cooled, the trigger is pulled again, repeating the process.
Skip Welds
Skip welding is the process of making a 1/2 inch to 3/4 inch weld and then moving to an alternate area and making another 1/2 inch to 3/4 inch weld. This cycle is repeated until the entire weld has been completed and all of the welds meet together, much like a continuous weld.
No Pretty Welds
There is no such thing as a continuous weld when welding thinner metals. By using the triggering and skip welding methods, you can achieve welds with good penetration and eliminate overheating the metal; however, the welds will be choppy-looking compared to a long continuous weld, especially when welding thicker metals. That is all right, as most of the welds performed will need to be ground down anyway.
Penetration
Achieving proper penetration is the most crucial concern when welding. If there is not enough penetration, the weld will not hold together. Penetration is the process of fusing two pieces of metal, which will make one piece.
Too much or too little penetration can weaken the weld, which can result in safety issues. Therefore, learning how to weld with the correct amount of penetration is the key to becoming a good auto body welder.
Poor Penetration
A few of the causes for poor penetration are not having the heat set high enough or traveling too fast. Both of these mistakes will result in poor penetration. The stickout can also produce poor penetration. If the gun is held too far away, the weld is going to be too cold, resulting in chicken scratch. This will also reduce the amount of shielding gas directed to the weld, which will create a porous weld.
How To Know If You Have Proper Penetration
When proper penetration is achieved, you should be able to see and feel ripples on the back side of the weld. However, if the backside looks like it has been welded due to penetration, then you have too much penetration. If you cannot feel any ripples at all on the backside, then there is not enough penetration.
Two Hands on the Wheel
When practicing welding, practice with both hands, just like driving a car or playing pool. If you walk up to the pool table and try to use the pool stick with one hand, you won’t be as accurate. Welding is the same way. Use one hand to hold the gun and pull the trigger, and the other hand to help position the gun. Practicing proper techniques like this will help you be more accurate and produce better welds.
Making the Pieces Fit
There is a lot to welding, but the key to making all of the pieces fit together and produce proper welds is to get the right amount of penetration without overheating the metal. You can read all about how to weld, but the final and most crucial piece of the puzzle is practice. It takes a lot of practice to master welding.
Plug Weld
A plug weld is the process of using a MIG welder to reproduce a factory spot weld. When using a MIG welder to reproduce a spot weld, it is called a plug weld. When plug welding, one piece of metal is lapped over another piece of metal. The top piece of metal has a hole drilled or punched into it using a drill or hole punch. Using a MIG welder, the hole is welded solid, which will also weld the top piece of metal together. The gun is held at 90 degrees to the metal.
Corrosion Protection For Plug Welds
The same rules apply for corrosion protection with any other type of weld. Before securing the metal together, it needs to be sprayed with weld-thru primer to protect it. Once the backside of the metal has been sprayed with weld-thru primer, the two pieces of metal can be secured and welded together.
Some technicians experience difficulty when welding on weld-thru primer. While weld-thru primer can be welded, you can remove any exposed weld-thru primer by using a wire brush, spot blaster, or small belt sander. This will only remove the exposed weld-thru primer, as the back sides of the repair have already been secured together. All remaining exposed weld-thru primer should be removed before using fillers, seam sealer, primers, etc., as these materials will not adhere well to the weld-thru primer.
What Size of Hole To Drill
Some manufacturers may recommend a specific hole diameter to drill or punch to prepare for welding. However, if there are no recommendations, drill or punch an 8 mm or 5/16 inch hole. There may also be times when more than two pieces of metal are being welded together, such as with a pinch weld. In this case, the top piece of metal will have a larger diameter hole, and the middle piece of metal will have a smaller diameter hole, which will allow all three pieces of metal to be welded together.
The Number Of Plug Welds To Use
You may be wondering how many plug welds to use when welding a new panel on. Just weld the same number of plug welds as there were factory spot welds; therefore, when preparing the new panel, drill or punch the same number of holes in the same locations. If a bedside had 10 spot welds along the top rail, then drill 10 holes 8 mm in diameter, apply weld-thru primer to the back sides of the repair area, secure the panel, remove the exposed weld-thru primer if you desire, and weld the holes.
Making The Weld
Once the panel is secure, use a MIG welder to fill the 8 mm hole, which will weld the two panels together. There are two ways to do this. You can start from the outside edge and spiral towards the center as you weld, filling in the hole. The second way is to start in the center spiral towards the outside while welding.
Once welded, there should not be any holes, gaps, or exposed edges visible.
Dressing The Plug Weld
Once the plug welds have been performed, grind the plug weld smooth to produce a level repair area that can be filled and primed to provide an invisible weld location. With this in mind, try to limit the height, thickness, or bulk of the weld. The bulkier the weld, the more grinding is required to clean the repair area to prepare for refinishing.
Gun Angle
This is the only weld type where the gun should be angled 90 degrees to the area being welded. This allows the proper amount of shielding gas and penetration to reach the weld surface.
Skip Welding
When plug welding, a skip technique should be used. This is the process of using alternate locations when welding. This is for heat management to eliminate overheating the metal in one location. If the first weld is made in the middle of the panel, move to one end to make the next weld, followed by welding the opposite end. Alternate welds until all plug holes have been welded.
A car consists of mostly spot welds. Therefore, spot welds will be used more than any other weld when welding on vehicles. Butt and lap are used when sectioning and structural repairs are needed.
Butt Weld
Butt welds are probably the second most common weld used in auto body repair. This weld is used when sectioning parts together. For example, when sectioning a quarter panel to the roof area, a butt weld will provide a weld that can be ground smooth and finished out without the weld location being visually noticeable after being painted.
Gap Between The Welds
When butt welding, a gap is required between the two pieces of metal being welded. This will provide proper penetration and allow the metal to expand and extract without binding up.
Butt Weld With a Backing Plate
A backing plate can also be used when performing a butt weld. This is a piece of metal behind the two pieces of metal being welded. This may be a recommended length when making structural repairs, such as creating a sleeve to fit inside the pieces being sectioned. A backing plate may also include plug welds in addition to butt welding the two pieces of metal together. A gap of about one to two times the metal thickness being welded is recommended for a butt weld with a backing plate to provide the needed penetration.
Gun Angles
The work angle on a butt weld should be 90 degrees. The travel angle should be between 5 and 15 degrees.
Weld-Thru Primer
Weld-thru primer should be applied to the back side of the weld location, as with all weld types. Once the new part or patch is secured and aligned, exposed weld-thru primer can be removed before welding.
Stitch Weld
Heat management is a concern when making a butt weld. Therefore, 1/2 inch to 3/4 inch should be the maximum length that should be welded at one time. Alternating to weld another area will allow each area to cool. If making a small butt weld, it may be necessary to stop and let the welds cool naturally between welds. Repeat the stitch welds until all welds are connected.
Making The Weld
When performing a butt weld, the best way I have found is to move the gun in a circular motion, while melting both edges of the metal together. I have also welded one nugget at a time, triggering the trigger to allow the metal to cool while making the 1/2 inch to 3/4 inch weld. Triggering is another way of heating the metal to the point of fusion, without overheating it.
Sealing The Weld Location
Since a butt weld is usually used on a visible location, a seam sealer will not be used to prevent moisture from entering. Therefore, once the weld has been ground, a fiberglass or aluminum filler should be applied over the weld location to seal the weld properly. Once the fiberglass or aluminum filler has been used and rough sanded, the repair can be finished with body filler. However, body filler alone will not seal the repair area, and corrosion can attack it.
Lap Weld
A lap weld is the process of lapping one piece of metal over another piece of metal and welding the two pieces together. This type of weld may be used on structural parts when an invisible weld location is not required. Therefore, a lap weld generally does not work well when sectioning panels together.
Weld-Thru Primer For Lap Welds
As with the other weld types, weld-thru primer must be applied to the back side of the weld locations. Once the part has been aligned and secured, the remaining weld-through primer can be removed.
Stitch Welding Lap Welds
Stitch welds are required for heat management, as with the other types of welds. However, depending on the recommended procedures, you may not have to weld the entire joint location. For example, there may be four 1-inch welds. They may or may not be spaced like the plug welds are spaced.
Performing The Weld
When performing a lap weld, it is essential to consider both edges of the metal and to provide equal heat and penetration to them. This requires angling the gun to heat both pieces of metal equally. As with a butt weld, I have found the circular motion to work best. However, some people prefer a zigzag motion. A triggering technique can be used with this type of weld, as with butt welding. Although burning through the metal on a lap weld is not as common as with a butt weld, heat management should still be observed as with other welds when working on cars.
Gun Angles
The gun work angle should be between 60 and 70 degrees when welding a lap weld. Travel angle should be between 5 and 25 degrees.
Cleaning A Lap Weld
Often, when performing a lap weld, it is not necessary to make an invisible repair. However, it is still essential to provide adequate corrosion protection. To seal the weld area, a seam sealer can be used to seal out moisture from entering the weld and creating rust.
There is a lot to welding, but this should give you the basic ideas of what to do. Now one thing is left….that is to put it all to use. Use the tips provided in the lesson and go practice.
1. **What are the key differences between MIG and TIG welding?**
– A) Welding technique
– B) Types of electrodes used
– C) Materials they can weld
– D) All of the above
2. **Which safety gear is essential when performing welding operations?**
– A) Safety glasses
– B) Welding helmet
– C) Fire-resistant gloves
– D) All of the above
3. **What is the significance of proper welding technique in achieving joint strength?**
– A) It doesn’t matter as long as the metal is joined
– B) It ensures uniform heat distribution and penetration
– C) It only affects the appearance of the weld
– D) It is only important for decorative welding
4. **What role does a filler material play in welding?**
– A) It cleans the metal surfaces
– B) It reinforces the joint and adds strength
– C) It cools down the weld area
– D) It prevents rust formation