TE/TC Stock pipes cracking at the spring

Crack will develop at the undercut on the thinner material when welding the thicker brackets to the thinner material everytime.
Hydrogen embrittlement is much worse if the pipe has been electroplated. Then attempting to do a repair makes it even worse.

Hydrogen embrittlement is even worse in harder alloy's and stronger steels. Stainless steel being one of these. S/S filler rod material being introduced to carbon steel has no benefit and can make the material brittle itself from simple contamination of the parent metal. It will be less ductile... There is no doubt about it.

Brazing is not welding and therefore no actual melting of the steel takes place, thereby avoiding any possible weld or trapped hydrogen embrittlement.

"Scalvini" is known for some of the highest quality workmanship there is and they weld there pipes with a small acetylene torch (A triple 000 size tip works fine) A jewelers torch works even better.

Owned a Tig since 1977 and have made over 200 or so expansion chamber exhaust systems since 1974 or 75. I've only Tig welded a few of those as it's just not necessary. 95% of them over the last 40+ years were welded with one of my tiny Victor torches that has 1/4" inch hose fittings.

Look at the mounts and header flange on the pipe pictured. The thicker sections and mounts are brazed. Scalvini likely wouldn't even think about dipping a pipe to electroplate it, as electroplating can lead to increased cracking from Hydrogen embrittlement.

Just a few more thoughts about using Stainless filler rod on mild steel.

I do realize we were just talking about thin expansion chambers cracking but these few posts below should shed a little light on welding with Stainless filler on your mild steel exhaust pipe or any other mild steel or Chromoly project made out of good quality materials.

My thoughts are, and this is offered for general information. I personally use "ER80S-D2" filler on my Chromoly tube chassis race car projects and minor repairs on my dirt bike parts as well if needed if its made or composed of any high strength alloys. It (ER80S-D2) has an 80psi tensile strength where as mild steel is usually 70,000psi tensile strength. So is the "ER70S"series of more common Mild steel filler rods, they are the best for doing any mild steel welding. 4130 Chromoly on the other hand is upwords of about 90,000psi tensile strength. The ER80S-D2 leaves a more ductile weld in the weld joint which will be closer to that of the 4130 alloy itself.

You do not at anytime weld 4130 chromoly with a 4130 filler rod because it will make the welds too brittle (close to 90,000 psi tensile strength) and would not allow the chassis to flex without cracking at the weld joints or adjacent to the welds in the heat affected zone. During flex the welds themselves would allow for little or no elongation. Costly stress relieving of the welded structure would be needed if this is done.

Its a good idea to always use a filler rod that's softer or at least one level down in tensile strength then the material being welded. Doing this type of welding with filler rod materials that are of higher strength alloys than the parent metal limits the fatigue life of the chassis or any other fabricated assembly considerably.

Including exhaust systems in all types of common motorsports.

For example, any quality set of mild steel race car headers will have the thicker cylinder head flanges Tig welded or actually Tig brazed with silicon bronze to connect the tubes to those flanges.

The silicon bronze Tig brazing process is what keeps the thin walled tubes from cracking away at the thicker flanges over there many vibration cycles during there intended lifespan. This should always be done instead of welding them directly with a steel filler rod to the thicker flanges. Same goes with the mounts. Exhaust systems can vibrate and fatigue faster than many other parts on an engine as they become somewhat like a tuning fork during use.

So what about doing that weld with Stainless filler rod on your next mild steel repair when it's needed? Not the best idea !!

Please read below. From the "Miller welding website". in a few very costly applications.
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Thread: stainless filler rod with mild steel

1. 02-27-2004, 07:42 AM #1
   jjense15
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   stainless filler rod with mild steel
   
   
   I am tig welding mild steel tubing with stainless filler rod (was told by a welding engineer that I could do this). I had been getting some contamination using mild steel filler rod, and was told that the stainless sort of acts like a cleaner. Does this make sense? The welds look perfect, but I am wondering if there are any structural issues when using the stainless. I talked with another experienced welder and he never heard of doing this.
   
   Thanks,
   Jason
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2. 02-27-2004, 09:25 AM #2
   
   ASKANDY
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   Jason,
   Kind of depends on the use of your weldment. There are better ways to assure good welds. In short, you are trying to mix an apple and an orange. Yes they are both fruit but the resulting bead integrity will give you a lot of strength and little or no elongation %. Normally you would want to match base metal characteristics to the filler. Tensile and Elongation requirements. Your SS filler has a much higher Tensile and may cause cracking under load. I most definitely would NOT use this filler for any chassis or roll cage construction. Those items need to have higher elongation %s(stretch) incase of impact. The bead must stretch with the basemetal. Your beads will look great with the SS, but we are after performance, not looks. Or maybe your applications is strictly visual. You will need to evaluate that.
   
   Thanks for the question and welcome!
   
   Andy
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3. 02-27-2004, 10:38 AM #3
   jjense15
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   stainless on mild steel
   
   
   Thanks Andy. I'm concerned now, since my project is a back half on a drag car and the work is just completed. Is there anything I can do now, grind the stainless and then go back over with the correct filler? The last thing I need is to have ladder bar brackets breaking off the rear end, etc.
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4. 02-27-2004, 11:29 AM #4
   
   ASKANDY
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   It was definitely mild steel right? Not Chrome-moly? If it was CM and not mild steel, the SS filler might work. It's still not the best but at least the base metals would be a better mix. Otherwise, I too would be concerned. Here'a a little story about a major NASCAR team that TIG welds their chassis. Not naming anyone but they thought the same as you. Welded 4 new chassis with a SS blended filler cause it looks great and flowed nice. Went to test at a track and after teardown later in the week found stress cracks. Hence, 4 scrap chassis and a change back to ER70S-2 and ER80S-D2 fillers. This race team was given the proper filler recommendations by me but decided to take the advice of the shop forman who was hired from an INDY car team. Indy cars do not use mild steel on anything. They performed destructive tests and came to the conclusion that I was right all along. Sometimes "looks good" doesn't perform good.
   
   You may be fine on some of the chassis points but I would rather you remake the ladder bar and attachments as that will see a regular amount of fatigue and impact with the race track.
   
   Sorry.
   
   Anyone else with EXPERIENCE on this might offer an additional view or alternative fix. At the very least, Stress relieve the welded areas.
   
   Andy
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5. 02-27-2004, 11:50 AM #5
   jjense15
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   Yes, mild steel. Looks like I am going to cut everything up and start over. Makes me sick to my stomach! I know who I WONT be going to advice from now on. Better to get right though. Thanks for the education

timmy, i always have the er70s wire in my lil 110 120amp gas welder, would it be worth me finding some of the er80s wire for repairing crmoly? like on old husky frames and such? er70s still best for things not crmoly?
i know a 110 unit is not ideal but for thinner stuff (like almost everything i do) it seems dialed in well and does a great job for me.

we have big 480 miller units at work using .045 wire, those have some power! they are alot of fun to use. welding is not my main job at work but i have learned the solid basics on welding overhead..enough to weld key parts to truck frames.

You say, ER70S in your Lil 110 120amp "gas welder"? You meant lil 110 120amp "mig" welder with shielding gas right? ER70S series of the solid wires is great for any general mild steel applications.

ER80S D2 is primarily a Tig filler rod. Its pretty hard to find in any diameter's for mig "GMAW" applications under .030. in 2lb spools. but it does come in spools from .030 all the way up to 1/16" solid wire diameters for specialty alloys.

It's a common low alloy filler rod for aircraft and specialty welding but is usually more commonly used in Tig welding aaplications.

I would not recommend mig welding thinner sections of a chromoly frame with any mig welder. Regardless of type filler rod used.

The ER80S series of filler rods contain just (0.50%) molybdenum for strength in these low alloy welding applications. It allows for 21% to 22% elongation in the weld area before breaking, this being closer to the Low alloy steel itself. It's not too brittle. It has a yield strength of about 71000 psi. and Tensile strength of as much as 85000 psi. when welded in a (GMAW) mig application. This filler rod also contains de-oxidizers such as manganese and silicon for use with straight CO2 shielding gas often used in production shops. This would be the way to go in heavy thick material applications only when necessary.

In Tig welding applications it can reach Tensile strengths of as much as 90000 psi. if properly done.
If you are going to repair or add a bracket or tab to your 4130 Chromoly frames, I would stick to use of a tig welder only using a ER80S-D2 series of filler rod. simple as that.

thanks timmy, i will maybe let a shop handle it then. we have a tig set up at work but they only work with aluminum building large toolboxes, they have done some nice repairs for me. one of these gays ill get a 220v mig

Saw a guy with a 14 KTM who's pipe had cracked however he got KTM to warranty this.... Ever seen a two stroke Red bike pipe crack????????????????????

NO !!

ive seen some swede pipes crack but they were semi-uncommon, down by the spring area...then again those werent in the first 5 years they were made either..

I am not welding my stock pipe. I tried a PC pipe, works good, but the stocker is better. I am putting on a Scalvini this week, I will post a pic and review. Now if anyone has a stock, uncracked pipe they are willing to get rid of--cheap--send me a PM.
I am pretty sure the misplaced exhaust springs were the original culprit of my cracking pipe. I am glad that is figured out now.

Scalvini,,Yaa.
There's nothing like there workmanship.
I would like to see some of the guys welding stamped production pipes all day, try to do the quality of work that Scalvini does.

My stock pipe cracked on the left side of the bike. Hairline crack. Replaced it with a FMF fatty. Gas welded the old one and intend to use it as a spare.