Re: What is the proper way to weld a roll cage in a car?
[Re: lancer493]
#2838650
10/29/20 09:12 AM
10/29/20 09:12 AM
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Joined: Nov 2015
Posts: 875 Missouri
jwb123
super stock
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super stock
Joined: Nov 2015
Posts: 875
Missouri
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Mig welding chrome moly makes it brittle, too much heat. Lot of the older guys that build airplanes welded chrome moly with an acetylene torch, makes welds like a tig if you know how to do it. But they had to heat the joints to keep them from cracking. I acetylene gas weld headers when I build them, had an old air craft mechanic watch me one time and he asked if I used to build airplanes.
MIG Welding 4130 Chrome-Moly By Galen White, welding engineer, Miller Electric Mfg. Co.
Grade 4130 steel, while containing both chromium and molybdenum as strengthening agents, is considered a heat treatable low alloy (HTLA). Generally referred to as chrome-moly, this HTLA is used largely for aviation, racing and welded tube structure applications.
When welding 4130, preheating to 300°F is strongly recommended by the American Welding Society (AWS) to relieve stresses in the metal. When choosing a wire, most people opt for ER80S-D2 or ER70S-2. ER80S-D2 will provide the most weld strength. The ER70S-2 is easier to find and provides a strong weld, but you’ll be sacrificing some strength by choosing this filler metal over ER80S-D2. When it comes to shielding gas, 75/25 (Ar/CO2) is recommended for most applications and 98/2 (Ar/CO2) for anything over 3/16 in.
Wire Size-Amperage Range- WFS Range Relationships for Short Circuit Transfer on Steel Wire Size Amperage Range Wire Feed Speed Range .023" 30-90 100-400 .030" 40-145 90-340 .035" 50-180 80-380 .045" 75-250 70-270
Cleanliness is critical when welding 4130. Make sure that all mill scale and oils are removed using mild abrasives and/or acetone. When you strike an arc, keep your heat input low to reduce stresses in the metal.
Post-weld heat treatment of 4130 varies from one application to another. If ductility and toughness are your goal, post-weld heat treatment is recommended up to 1,200°F. If the material you are welding is thinner than .120 in., stress relief through heat treatment is not as critical.
WFS Rule of Thumb: 1 ampere for every .001 thickness 1/8" material=.125=125 Amperes Wire Burn Off: .023-3.5" wire/amp - 125 amps=437 IPM .030 - 2" wire/amp - 125 amps=250 IPM .035 - 1.6" wire/amp - 125 amps=200 IPM .045 - 1" wire/amp - 125 amps=125 IPM
Welding 4130 is a lot like welding mild steel and is easy if you know how. These are just some of the reasons 4130 is considered so flexible and is used on everything from airplane engine mounts to bicycle frames
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Re: What is the proper way to weld a roll cage in a car?
[Re: jwb123]
#2838679
10/29/20 10:21 AM
10/29/20 10:21 AM
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Joined: Jan 2004
Posts: 8,236 fredericksburg,va
cudaman1969
master
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master
Joined: Jan 2004
Posts: 8,236
fredericksburg,va
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I might add, when welding MS, unlike CM, leave a 1/16 gap between the pieces. The wire will penetrate and not ‘bubble gum’ up on the joint. Next time you’re at the races look at each cars ‘welds’ then ask yourself would you feel safe in there? I would only use .125 DOM tube also, doesn’t have to be .134 because it’s uniform. Just a hoop 1.3/4, cage can be 1.625
Last edited by cudaman1969; 10/29/20 10:22 AM.
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Re: What is the proper way to weld a roll cage in a car?
[Re: cudaman1969]
#2838691
10/29/20 11:03 AM
10/29/20 11:03 AM
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Joined: Jan 2003
Posts: 19,361 Las Vegas
Al_Alguire
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 19,361
Las Vegas
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Per NHRA rules moly MUST be tig welded so it does not really matter IF it can be welded with a mig welder for the purposes of this discussion. As for attachment of bars in a unibody car it is acceptable by rule to weld the bars to 6"x6" plates to the floor.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: What is the proper way to weld a roll cage in a car?
[Re: cudaman1969]
#2838726
10/29/20 12:09 PM
10/29/20 12:09 PM
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Joined: Jan 2011
Posts: 4,785 Utah and Alaska
astjp2
master
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master
Joined: Jan 2011
Posts: 4,785
Utah and Alaska
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Mild steel will give and bend (absorb) when hit. CM will crack over time, the reason for the X-ray requirements. My first car was MS but was hard to sell, the two I have now are CM because that’s what the racers want. Remember the number one rule, triangulation. Your 50 pound head in a 5 pound helmet flopping around to close to a bar in a wreck is not good. I don’t think 2” is far enough away, remember Dale Earnhardt. these are just my opinions. That is almost true, aircraft of yesteryear were mostly chromoloy and were welded with a torch, the heat affected zone was a lot larger back then and a 3/4" .049 wall tube in a cluster weld could survive an impact at 100 mph plus. Modern welding uses TIG and the HAZ is a lot smaller, if you pre and post heat and not contaminate the weld with the tungsten, it will last just as long as mild steel and look as beautiful as a modern weld. Tim
1941 Taylorcraft 1968 Charger 1994 Wrangler 1998 Wrangler 2008 Kia Rio 2017 Jetta
I didn't do 4 years and 9 months of Graduate School to be called Mister!
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Re: What is the proper way to weld a roll cage in a car?
[Re: lancer493]
#2838788
10/29/20 01:53 PM
10/29/20 01:53 PM
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Joined: Dec 2005
Posts: 11,530 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,530
Fulton County, PA
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There seems to be two different opinions in this post on welding CM tubing. One implies it must be Tig welded, the other implies it can be Mig welded. Never tried Mig welding CM but was wondering if it was acceptable in the welding of smaller, lighter duty brackets. Not trying to hi-jack this thread, but hope someone might clear this up. Seems like an important issue here. Bill Not sure whose information you are seeing, but as far as NHRA and SFI are concerned - ANY weld on CM to CM joints or that affect a CM chassis structure part, i.e. welding a mild steel tube, tab, etc onto a CM tube, must be done with the TIG process. Period. There may be other places, or industries where MIG on 4130 is acceptable. Pipelines, etc., with a person trained and skilled doing it. But NOT on a piece of .083 tubing where heat needs to be tightly controlled. Mild steel is not all the same. DOM, ERW, 1010, 1020, etc. DOM - Drawn Over Mandrel is much more accurate thickness wise than ERW - electric welded seam. This is why kits and tubing made from ERW need to be .134" wall to ensure it passes a .118" sonic check for cert. This obviously adds 10% to the weight of it. DOM will pass and is typically within .0005". I've seen .120 ERW as thin as .113-.114. Years ago, when chassis certs became a thing, a lot of cars that guys had been racing for years and built from kits using .120 welded seam material, became junk. Cut it off at the frame rails and start over. DOM is typically 1020 where ERW is usually 1010. This indicates the amount of carbon in the alloy which affects the hardness among other things. The difference is easily seen by running an 1/8" drill through pieces of 1010 and 1020 material of similar thickness. CM is 4130. The last 2 digits indicate the percentage of carbon. The price difference between DOM and 4130 is minimal. ERW is cheap s***. It may be okay for a cheap 8 point in an 11 - high 10 second car. I won't use it.
If the results don't match the theory, change the theory.
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Re: What is the proper way to weld a roll cage in a car?
[Re: Al_Alguire]
#2838794
10/29/20 02:02 PM
10/29/20 02:02 PM
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Joined: Dec 2005
Posts: 11,530 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,530
Fulton County, PA
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Per NHRA rules moly MUST be tig welded so it does not really matter IF it can be welded with a mig welder for the purposes of this discussion. As for attachment of bars in a unibody car it is acceptable by rule to weld the bars to 6"x6" plates to the floor. Both true. Specs and construction techniques in the rule book are understood to be minimum acceptable. Fabing a frame structure in the floor, and building the cage on that rather than the thin sheet metal, will greatly add to the strength of the car. Safer, more consistent and responsive to chassis tuning.
If the results don't match the theory, change the theory.
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Re: What is the proper way to weld a roll cage in a car?
[Re: jwb123]
#2838806
10/29/20 02:26 PM
10/29/20 02:26 PM
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Joined: Dec 2005
Posts: 11,530 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,530
Fulton County, PA
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Mig welding chrome moly makes it brittle, too much heat. Lot of the older guys that build airplanes welded chrome moly with an acetylene torch, makes welds like a tig if you know how to do it. But they had to heat the joints to keep them from cracking. I acetylene gas weld headers when I build them, had an old air craft mechanic watch me one time and he asked if I used to build airplanes.
MIG Welding 4130 Chrome-Moly By Galen White, welding engineer, Miller Electric Mfg. Co.
Grade 4130 steel, while containing both chromium and molybdenum as strengthening agents, is considered a heat treatable low alloy (HTLA). Generally referred to as chrome-moly, this HTLA is used largely for aviation, racing and welded tube structure applications.
When welding 4130, preheating to 300°F is strongly recommended by the American Welding Society (AWS) to relieve stresses in the metal. When choosing a wire, most people opt for ER80S-D2 or ER70S-2. ER80S-D2 will provide the most weld strength. The ER70S-2 is easier to find and provides a strong weld, but you’ll be sacrificing some strength by choosing this filler metal over ER80S-D2. When it comes to shielding gas, 75/25 (Ar/CO2) is recommended for most applications and 98/2 (Ar/CO2) for anything over 3/16 in.
Wire Size-Amperage Range- WFS Range Relationships for Short Circuit Transfer on Steel Wire Size Amperage Range Wire Feed Speed Range .023" 30-90 100-400 .030" 40-145 90-340 .035" 50-180 80-380 .045" 75-250 70-270
Cleanliness is critical when welding 4130. Make sure that all mill scale and oils are removed using mild abrasives and/or acetone. When you strike an arc, keep your heat input low to reduce stresses in the metal.
Post-weld heat treatment of 4130 varies from one application to another. If ductility and toughness are your goal, post-weld heat treatment is recommended up to 1,200°F. If the material you are welding is thinner than .120 in., stress relief through heat treatment is not as critical.
WFS Rule of Thumb: 1 ampere for every .001 thickness 1/8" material=.125=125 Amperes Wire Burn Off: .023-3.5" wire/amp - 125 amps=437 IPM .030 - 2" wire/amp - 125 amps=250 IPM .035 - 1.6" wire/amp - 125 amps=200 IPM .045 - 1" wire/amp - 125 amps=125 IPM
Welding 4130 is a lot like welding mild steel and is easy if you know how. These are just some of the reasons 4130 is considered so flexible and is used on everything from airplane engine mounts to bicycle frames Good information. The old guys running a welding class I attended many years ago made you learn to gas weld before touching a TIG torch. A very good idea even today. Learn how to work your hands before adding the foot (or thumb) control. Plus they had a tight budget and didn't want all the class time used up ruining and grinding tungsten. I like to use a propane torch to warm a joint before welding but mostly to burn off any contaminates or moisture. You can see the crap come out of it. Preheat on 083 or 058 is debatable. Another technique I've seen recommended is starting a weld at the thin part of an intersecting tube on a notched joint. This is where the minimum heat is needed and working the weld to the corner or the thickest point of the joint serves to preheat that area. I like ER-70 over 80. Either wire will mix with the base and the resulting weld will a higher strength (tensile) than the wire by itself. 80 will be stronger and harder. I think 70 provides a bit more ductile weld with some give that can help with not cracking the tube in the HAZ over time. The expected use and lifespan of the chassis will effect this decision.
If the results don't match the theory, change the theory.
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Re: What is the proper way to weld a roll cage in a car?
[Re: jlatessa]
#2838830
10/29/20 03:06 PM
10/29/20 03:06 PM
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Joined: Jan 2004
Posts: 8,236 fredericksburg,va
cudaman1969
master
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master
Joined: Jan 2004
Posts: 8,236
fredericksburg,va
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Wow, a 50 pound head! Not to be a smart a$$, but you have to have a LOT of Gold fillings. LOL
Joe 20% of your body weight last heard, take yours off put it on the scale to see what it weighs
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Re: What is the proper way to weld a roll cage in a car?
[Re: cudaman1969]
#2839002
10/29/20 09:03 PM
10/29/20 09:03 PM
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Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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Wow, a 50 pound head! Not to be a smart a$$, but you have to have a LOT of Gold fillings. LOL
Joe 20% of your body weight last heard, take yours off put it on the scale to see what it weighs That "20%" sounds more like the energy consumed, rather than weight, but I am sure some do use more or less then others. "Despite this, even at rest, the brain consumes 20% of the body's energy. The brain consumes energy at 10 times the rate of the rest of the body per gram of tissue. The average power consumption of a typical adult is 100 Watts and the brain consumes 20% of this making the power of the brain 20 W" https://hypertextbook.com/facts/2001/JacquelineLing.shtml#:~:text=Despite%20this%2C%20even%20at%20rest,of%20the%20brain%2020%20W.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: What is the proper way to weld a roll cage in a car?
[Re: cudaman1969]
#2839022
10/29/20 09:22 PM
10/29/20 09:22 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
master
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master
Joined: Apr 2006
Posts: 4,220
West Plains, MO
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Wow, a 50 pound head! Not to be a smart a$$, but you have to have a LOT of Gold fillings. LOL
Joe 20% of your body weight last heard, take yours off put it on the scale to see what it weighs A human head weighs about 12-15 lbs. Unless the brain is made of iron. Or lead.
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Re: What is the proper way to weld a roll cage in a car?
[Re: DrCharles]
#2839051
10/29/20 10:32 PM
10/29/20 10:32 PM
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Joined: Dec 2013
Posts: 4,669 Wichita
GY3
master
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master
Joined: Dec 2013
Posts: 4,669
Wichita
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Wow, a 50 pound head! Not to be a smart a$$, but you have to have a LOT of Gold fillings. LOL
Joe 20% of your body weight last heard, take yours off put it on the scale to see what it weighs A human head weighs about 12-15 lbs. Unless the brain is made of iron. Or lead. My wife would argue that mine is empty...
'63 Dodge 330 11.19 @ 121 mph Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs. 10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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Re: What is the proper way to weld a roll cage in a car?
[Re: GY3]
#2839087
10/29/20 11:22 PM
10/29/20 11:22 PM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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Hang on, I’ll go throw one on the scale. Be back in a minute.
"use it 'till it breaks, replace as needed"
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