Chrome moly vs dom

[Bubstr]

I wonder if you guys know, that braising was the preferred method of joining chrome molly for years. From the time they started manufacturing different chrome molly in the 40s threw the 50s all your F1 cars and WW2 aircraft where braised and held up very well. There was no real problem till mass manufacturing needed a faster way to join them. The fact is you can weld them with a torch, FAA still approves this method on experimental aircraft. You can Mig and you can Tig even though NHRA won't let you Mig. Excessive heat is the culprit that weakens joints. Your heat settings rod or wire, how the joint fits and how fast you travel with your rod all enter in to a good weld. If you have any doubts about your weld, first look at the heat ring by the weld. If it extends more than the width of the weld, you may be too hot, too slow or using wrong rod or wire. Then cut a couple apart and see if your bead goes to the bottom of the joint. If the bead on the bottom of the joint is more than about 1/3 the width of the top, you may be too hot. If you see a line of the joint your too cold. If it was easy everyone would be willie the welder. I don't care for joining dissimilar metals especially if the wall thickness is different, but it can be done well. It just taxes your ability to direct the heat more. The Tig is a little easier to control the heat and run, but a good welder with an oxy acct torch can do it also and not impossible with a Mig. Beating a joint to test strength is probably not as effective as pulling them apart with your frame machine. Tensile strength is where they most likely fail. One other tip. Make sure your CM is of the normalized variety. usually has a N at the end of the number. This should not have to be annealed after a proper weld.

I'm not a chassis builder but I stayed in a Holiday Inn once.

[50j]

That's interesting information on the aircraft manufacturing. Be careful though, you provided too many facts and some mongoloid will probably want to argue. Since you mentioned aircraft they might think you're talking about "NASA space sh#$".

[rmrc]

I haven't been here for quite a while so I missed the goofy stuff.
First off, 1 foot of 1 1/2" x .083 Chromemoly and 1 foot of 1 1/2" x .083 DOM weigh the same. There is no weight savings with moly EXCEPT that moly is stronger and builders feel that can use a lighter gage tubing. I won't get into that debate right now.
I have built LM racecars since 1987. After seeing a chromemoly car severely break apart after a grinding crash, I vowed to NEVER build one. That changed in 1999 when a structural engineer at a local steel treating plant approached me about normalizing our racecars. Over almost 6 months we tested and destroyed and microscopically examined hundreds of welds. We found that welding moly with a normal mig welder, using normal, everyday .030 wire provided the best weld. There is a mixing of properties between the parent material and the filler. You wind up with a very elastic weld that picks up some of the strength of the moly. We also found that if the entire chassis is normalized at 1100 deg. F and allowed to slowly air cool, the welded material and adjacent tubing return to virtually virgin integrity. ( they used the number 98%) Our moly chassis racecars have been proven over the years to be extremely durable and very repeatable. We have never seen any tubing fractures adjacent to the welds. As far as I'm concerned this is the only economical way to normalize an entire racecar. Crash repairs can be done by post heating the welds and adjacent tubing with an oxy acetalene torch and a temp stick to verify the correct temperature. (should be available at your local welding store)
I've recently heard of normalizing by using vibration but have no first hand knowledge of it's use for our application.
One final thought, anyone who tells you that powder coating "sorta" normalizes the racecar is FOS.

[50j]

I haven't been here for quite a while so I missed the goofy stuff.
First off, 1 foot of 1 1/2" x .083 Chromemoly and 1 foot of 1 1/2" x .083 DOM weigh the same. There is no weight savings with moly EXCEPT that moly is stronger and builders feel that can use a lighter gage tubing. I won't get into that debate right now.
I have built LM racecars since 1987. After seeing a chromemoly car severely break apart after a grinding crash, I vowed to NEVER build one. That changed in 1999 when a structural engineer at a local steel treating plant approached me about normalizing our racecars. Over almost 6 months we tested and destroyed and microscopically examined hundreds of welds. We found that welding moly with a normal mig welder, using normal, everyday .030 wire provided the best weld. There is a mixing of properties between the parent material and the filler. You wind up with a very elastic weld that picks up some of the strength of the moly. We also found that if the entire chassis is normalized at 1100 deg. F and allowed to slowly air cool, the welded material and adjacent tubing return to virtually virgin integrity. ( they used the number 98%) Our moly chassis racecars have been proven over the years to be extremely durable and very repeatable. We have never seen any tubing fractures adjacent to the welds. As far as I'm concerned this is the only economical way to normalize an entire racecar. Crash repairs can be done by post heating the welds and adjacent tubing with an oxy acetalene torch and a temp stick to verify the correct temperature. (should be available at your local welding store)
I've recently heard of normalizing by using vibration but have no first hand knowledge of it's use for our application.
One final thought, anyone who tells you that powder coating "sorta" normalizes the racecar is FOS.

That's interesting too. I do have a couple of questions though. Other than the obvious advantage of being able to speed up production by mig welding them, why would you rather do it that way than tig weld it where you have more control over the heat as you weld a joint? I'm assuming that when you say "everyday wire" you're referring to ER70-S2 or ER70-S6, and if you are using the same filler material but have less control what would the advantage be? Also, how was the tig welding done? What shielding gas? Was the welder experienced at welding 4130? You didn't see better penetration with the tig? Having done a lot of both I'm curious but not arguing with your procedure.

[fastford]

I haven't been here for quite a while so I missed the goofy stuff.
First off, 1 foot of 1 1/2" x .083 Chromemoly and 1 foot of 1 1/2" x .083 DOM weigh the same. There is no weight savings with moly EXCEPT that moly is stronger and builders feel that can use a lighter gage tubing. I won't get into that debate right now.
I have built LM racecars since 1987. After seeing a chromemoly car severely break apart after a grinding crash, I vowed to NEVER build one. That changed in 1999 when a structural engineer at a local steel treating plant approached me about normalizing our racecars. Over almost 6 months we tested and destroyed and microscopically examined hundreds of welds. We found that welding moly with a normal mig welder, using normal, everyday .030 wire provided the best weld. There is a mixing of properties between the parent material and the filler. You wind up with a very elastic weld that picks up some of the strength of the moly. We also found that if the entire chassis is normalized at 1100 deg. F and allowed to slowly air cool, the welded material and adjacent tubing return to virtually virgin integrity. ( they used the number 98%) Our moly chassis racecars have been proven over the years to be extremely durable and very repeatable. We have never seen any tubing fractures adjacent to the welds. As far as I'm concerned this is the only economical way to normalize an entire racecar. Crash repairs can be done by post heating the welds and adjacent tubing with an oxy acetalene torch and a temp stick to verify the correct temperature. (should be available at your local welding store)
I've recently heard of normalizing by using vibration but have no first hand knowledge of it's use for our application.
One final thought, anyone who tells you that powder coating "sorta" normalizes the racecar is FOS.

you are absolutely correct and i made a statement like this somewhere earlier in this post, i have been looking into a sonic vibration table my self, i think it may be helpful, but there is no need to say to much about it on here because some dumb a$$ nasa engineer may try to argue with you LOL

[rmrc]

That's interesting too. I do have a couple of questions though. Other than the obvious advantage of being able to speed up production by mig welding them, why would you rather do it that way than tig weld it where you have more control over the heat as you weld a joint? I'm assuming that when you say "everyday wire" you're referring to ER70-S2 or ER70-S6, and if you are using the same filler material but have less control what would the advantage be? Also, how was the tig welding done? What shielding gas? Was the welder experienced at welding 4130? You didn't see better penetration with the tig? Having done a lot of both I'm curious but not arguing with your procedure.

Well, let's quote Mr. Obvious "Other than the obvious advantage of being able to speed up production by mig welding them"....... Realizing that most chassis builders build more than a couple cars a year, why would you want to spend 2-3 days tig welding a complete LM when you can mig one in 3-4 hours. Time is money! At the end of the day you MIGHT wind up with a product that didn't break on impact by using either method. BUT, and I believe that it's a big BUT, when you normalize a chassis using the method that I described, the car comes out of the furnace with absolutely no memory. It is completely free of any welding induced stress. It's a process that we suggested to a couple of Cup teams. They decided to keep making cars that varied from one to another. Even NASCAR teams will tell you that they weld in a specific pattern, attempting to make the cars consistent. I hope that answers your questions!

[rmrc]

BTW
All of our testing was done with standard S7 welding wire from Lincoln Electric. We still use that wire today for mild steel or moly welding.

[50j]

Check your pm rmrc.