SYMPTOM'S
1. What causes SPATTER?
2. What causes VOIDS/ HOLES and “SPUTTER”?
3. What causes POROSITY?
4. What causes INCORRECT WELD PROFILE?
5. What causes ARC BLOW?
6. What causes POOR FUSION?
What are the RECOMMENDED CORRECTIVE ACTIONS for each of the above.
RECOMMENDED CORRECTIVE ACTION
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david58
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RECOMMENDED CORRECTIVE ACTION
Hot, humid air is less dense than cooler, drier air. This can allow a golf ball to fly through the air with greater ease, as there won't be as much resistance on the ball.
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bugdust69
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Re: RECOMMENDED CORRECTIVE ACTION
david58 wrote:SYMPTOM'S
1. What causes SPATTER?
2. What causes VOIDS/ HOLES and “SPUTTER”?
3. What causes POROSITY?
4. What causes INCORRECT WELD PROFILE?
5. What causes ARC BLOW?
6. What causes POOR FUSION?
What are the RECOMMENDED CORRECTIVE ACTIONS for each of the above.
Mig welding
1. wire speed too high for voltage, bad ground, dirty weld surface, rusty wire, etc.
2. holes can be caused by an impurity (especially grease, oil, etc) among other things. The "hole" or wire dimple at the end of a weld is usually from pulling out of the puddle too quick. A crater at the end of a weld is from stopping to quick and not allowing the weld to build up to size.
3. Porosity can be from impurities on the weld surface but is usually the shielding gas set incorrectly or too much wire stick-out. keep the wire stick-out less than 3/4" max depending on conditions. I prefer 1/2" or so. Most home applications will be using 75/25 gas and you will read all kinds of recommendations about settings...I keep mine around 20 cfh, sometimes a little higher if near the door. I never go above 25-30. Too little gas and your weld will be dark grey, almost black, may have porosity and larger globs of silica. Too much gas will cause turbulence in the puddle, cause porosity, undercut and your welds will be shinier with little silica on the surface. Find the balance.
4. Incorrect weld profile is actually technically a couple different defects. The leg lengths being different are usually gun position. The throat being concave is either machine settings, travel speed too fast or you are pushing the puddle at too much angle. The throat being convex is too much wire, too slow travel speed or you are dragging the puddle with too much angle. Inconsistent travel speed can cause roughness.
5. arc blow? I'm guessing you mean undercut. See above. Gun angle, pushing the puddle, too fast travel or too much shielding gas are the main causes.
6. Lack of fusion is generally incorrect machine settings (too "cold" for wire speed), dragging the puddle too fast or poor surface quality. Steel often has mill scale on it that must be cleaned off with a grinder, sander or needle gun before welding.
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craigvwdude
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167luckycharm
- Posts: 2
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#5 Arc Blow
Hey all, first post on this site for me...
As a welder from '87 until '02, I've experienced arc blow when using steel welding electrodes (E6011, 7018, etc) to join steel plates that have a bit of residual magnetism in them. Typically, when welding angle iron and other structural shape together, the pieces are cut with a torch or cutoff saw...not much magnetism involved. But take a steel plate or sheet that has been picked up with a electromagnetic crane during transport, and try to butt-weld it to another sheet, you'll find that the flux coating on the tip of the rod just above the welding puddle will blow outwards in any direction. Steel in liquid condition has unpredictable magnetic properties, making it difficult to follow the welding pattern that the welder is trying to manipulate during the weld. The end result is a weld bead that zig-zags across the joint. It's not pulling the welding rod toward the plate, it's pulling the molten metal in uncontrollable surges. Even when trying to tack-weld the plates together, the welds are hard to control. Steel plate (1/2" thick for example) that had the mill scale removed by grinding, will have enough magnetism to create arc blow.
Just my tidbit of info!
Aloha!
John
As a welder from '87 until '02, I've experienced arc blow when using steel welding electrodes (E6011, 7018, etc) to join steel plates that have a bit of residual magnetism in them. Typically, when welding angle iron and other structural shape together, the pieces are cut with a torch or cutoff saw...not much magnetism involved. But take a steel plate or sheet that has been picked up with a electromagnetic crane during transport, and try to butt-weld it to another sheet, you'll find that the flux coating on the tip of the rod just above the welding puddle will blow outwards in any direction. Steel in liquid condition has unpredictable magnetic properties, making it difficult to follow the welding pattern that the welder is trying to manipulate during the weld. The end result is a weld bead that zig-zags across the joint. It's not pulling the welding rod toward the plate, it's pulling the molten metal in uncontrollable surges. Even when trying to tack-weld the plates together, the welds are hard to control. Steel plate (1/2" thick for example) that had the mill scale removed by grinding, will have enough magnetism to create arc blow.
Just my tidbit of info!
Aloha!
John
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bugdust69
- Posts: 217
- Joined: Tue Nov 26, 2002 12:01 am
Interesting. I don't think I've ever had a problem with residual magnetism as you described but I have seen similar occurences while using smaller electro magnets to hold plate in position while tacking. I've used a small 3500lb circular electro magnet to hold two pieces of 10mm plate flush. One plate had an 8mm bevel. As I would tack near the magnet the puddle would do just as you described and pull in different direction, not neccasarily towards the magnet. This was on mild steel (A572) plate using a mig in spray-transfer, 1/16" metal-core wire at about 320 amps.
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167luckycharm
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Bugdust,
My first experience with arc-blow was during the fabrication of a blast door for an explosives storage bunker. The 1/2" thick steel plate had a sticker with the "handled by electromagnet" inscription. Only after flipping the plate over did I see the sticker. The opposite side was exposed to the weather for several years and needed the mill-scale to be ground off. The hinges, lock-box, drawbar guides, and the door skin were all to be flame-cut from this one 6' x 12' sheet. There may have been a sticker on the topside at one time, but it was gone by the time I started the project. The mill-scale will flake off when cutting with a torch, taking the marked line with it. Trying to follow the line when cutting by hand becomes even more difficult when those hot flakes pop up into your face and arms. I used a 9" angle grinder to scrub off the mill scale and rusty areas before I did any of the layout lines.
You were experiencing arc blow in a sense. If you were welding with a stick electrode, the problem would have been much more pronounced, as you would see the flux break away just above the tip, and the arc jumping from the side of the rod toward the edge of the steel.
The remedy for this problem... On thick plates, typical procedure when butt-welding is to allow a gap between the ends to obtain good penetration. This gap allows both plates to opposing/attracting magnetic lines of force. You would see metal filings clinging between the two edges. Tack welding becomes difficult. Since the gap on my workpiece was 1/8", I placed welding rod stubs (the ends of consumed rods) between the plates at 6" spacing. They simply stood up between the plates allowing the magnetism to "cancel out" in the immediate area. I simply started the arc at the stub, melted the puddle into the joint and fused the plates together, making a 3/4" long tack weld. Kept doing it throughout the length of the joint until it was completely held together, flipped the project over and welded the back side's first pass, back-stitch method. Went back to topside and back-stitched between the tack-welds.
I'm convinced that the best way to overcome the arc-blow is to fit the joints without a gap, but bevel the ends either vee or U groove. As long as the ends make contact, the magnetism is minimized. It's been a long time since I've encountered this.
Good luck!
John
My first experience with arc-blow was during the fabrication of a blast door for an explosives storage bunker. The 1/2" thick steel plate had a sticker with the "handled by electromagnet" inscription. Only after flipping the plate over did I see the sticker. The opposite side was exposed to the weather for several years and needed the mill-scale to be ground off. The hinges, lock-box, drawbar guides, and the door skin were all to be flame-cut from this one 6' x 12' sheet. There may have been a sticker on the topside at one time, but it was gone by the time I started the project. The mill-scale will flake off when cutting with a torch, taking the marked line with it. Trying to follow the line when cutting by hand becomes even more difficult when those hot flakes pop up into your face and arms. I used a 9" angle grinder to scrub off the mill scale and rusty areas before I did any of the layout lines.
You were experiencing arc blow in a sense. If you were welding with a stick electrode, the problem would have been much more pronounced, as you would see the flux break away just above the tip, and the arc jumping from the side of the rod toward the edge of the steel.
The remedy for this problem... On thick plates, typical procedure when butt-welding is to allow a gap between the ends to obtain good penetration. This gap allows both plates to opposing/attracting magnetic lines of force. You would see metal filings clinging between the two edges. Tack welding becomes difficult. Since the gap on my workpiece was 1/8", I placed welding rod stubs (the ends of consumed rods) between the plates at 6" spacing. They simply stood up between the plates allowing the magnetism to "cancel out" in the immediate area. I simply started the arc at the stub, melted the puddle into the joint and fused the plates together, making a 3/4" long tack weld. Kept doing it throughout the length of the joint until it was completely held together, flipped the project over and welded the back side's first pass, back-stitch method. Went back to topside and back-stitched between the tack-welds.
I'm convinced that the best way to overcome the arc-blow is to fit the joints without a gap, but bevel the ends either vee or U groove. As long as the ends make contact, the magnetism is minimized. It's been a long time since I've encountered this.
Good luck!
John