4130 welded frame anyone?!?!
Close
Login to Your Account
Page 1 of 2 12 LastLast
Results 1 to 20 of 38
  1. #1
    Join Date
    Mar 2004
    Location
    Granada Hills, CA
    Posts
    498
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Post

    Hey all,

    Well im gearing up for my senior project, which is basically a performance comparison of 4130 vs 1020 DOM steel tubing in the construction of space frames for ground vehicles. Here are some pictures of a dent test i am going to conduct, this is a preliminary test, so its not all aligned yet. But intersting results so far...These are all 4130N 1.25"0.065wall

    Basic Dent...125J of enery i believe...


    Same Energy, TIG weld with no filler



    Same Energy, TIG weld, filler


    Kinda makes ya wonder...

    Nick

  2. #2
    Join Date
    Sep 2004
    Location
    Fort Worth, TX
    Posts
    224
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Post

    It doesn't make me wonder at all. It is very typical behavior of 4130 after welding.

    What was the condition of the material before the welding? Was it Normalized (condition "N") 90 ksi steel?

    If so, then what were the cooling parameters after the welding heat input?

    My thought is that you are very close to the strain limits of the metal before the weld, and the application of heat changed the metallurgy enough to reduce the ductility. This is not surprising and it typically what happens when 4130 is welded....by any weld process.

    Also remember that the filler metal can influence the metallurgy in the joint. Using a lower carbon filler rod (RG 65...formerly known as Oxweld 32 CMS) will improve ductility throughout the joint without any substantial reduction in strength.

    Do the TIG weld again, and then conduct a post weld re-heat to 800 deg. F for about 15-30 mins. and see what happens.

    Interesting stuff!

  3. #3
    Join Date
    Nov 2002
    Location
    Burlington, NJ
    Posts
    1,339
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    96

    Post

    Don't make me wonder if there was no post heat treatment. It needs to be annealed to get it back to it's soft state again. You heated it smokin hot and the surrouning metal quenched it. It's brittle. I'm not a heat treater by trade, but I would never do something like that in industry. Read a text book on heat treating. There are more people here more versed on this subject then me, they will clue you in.
    Bill

  4. #4
    Join Date
    Apr 2003
    Location
    Portland, ME, USA
    Posts
    2,086
    Post Thanks / Like
    Likes (Given)
    3
    Likes (Received)
    3

    Post

    Team Fast -
    Always thought that the RG series (RG45,RG60) were recommended for O/A welding, but the ER series (ER70S3, etc) were the selection for TIG?

    Something to do with the oxygen content of the filler?

    Thoughts?

  5. #5
    Join Date
    Aug 2003
    Location
    Eureka, CA, USA
    Posts
    1,558
    Post Thanks / Like
    Likes (Given)
    274
    Likes (Received)
    223

    Post

    Nick, in addition to the issues already mentioned regarding lack of post heat treatment, consider this: since no filler metal was added to the welds, the wall thickness of the tubing varied, depending on the metal flow.

    Some sections will be thicker than the nominal .065 but some will be much thinner. (There will also be stress amplification at abrupt changes of section ...)

  6. #6
    Join Date
    Feb 2004
    Location
    peekskill, NY
    Posts
    23,397
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    3580

    Post

    Hey, how about a test piece with silver
    solder on it?

    Jim

  7. #7
    Join Date
    Feb 2004
    Location
    Macon, MO USA
    Posts
    282
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    5

    Post

    Damonfg, you are correct. I doubt if you could detect a difference between the two in his test results though as long as the basic composition and tensile strengths of the two rods are similar.

  8. #8
    Join Date
    Apr 2003
    Location
    Portland, ME, USA
    Posts
    2,086
    Post Thanks / Like
    Likes (Given)
    3
    Likes (Received)
    3

    Post

    Doc, thank you. Agreed on the test results.

    I think we ususally run 4140 filler when welding 4130 with TIG.

  9. #9
    Join Date
    Jun 2004
    Location
    San Francisco, CA
    Posts
    3,050
    Post Thanks / Like
    Likes (Given)
    5
    Likes (Received)
    62

    Post

    "a performance comparison of 4130 vs 1020 DOM steel tubing in the construction of space frames for ground vehicles"

    Since the modulus of elasticity for both steels is the same two frames made of identical tubing sizes will perform identically in re stiffness of the chassis.

    I've used 1018 in all the frames I've built. I'd consider using 4130 the exposed tubing in a dirt bike frame that could use the extra dent resistance over the mild steel.

    cheers,
    Michael

  10. #10
    Join Date
    Jul 2004
    Location
    Houston, TX USA
    Posts
    26,554
    Post Thanks / Like

    Post

    I suppose it is worth mentioning that thousands of gas (O/A)welded steel tube aircraft structures were/have been performing adequately since the process became popular following WW1. The majority were/are gas welded 4130, starting with normalized material. Up until around 1930, it was common to use 1025 tubing and fittings.

    Improvements in filler material have occured over the years, but almost all were welded with mild steel welding rod.

    John

  11. #11
    Join Date
    Mar 2004
    Location
    Granada Hills, CA
    Posts
    498
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Post

    Alright heres the thing guys. Im trying to replicate what our teams are actually doing to 4130 tubing when they "just weld it". ER70S-2 filler is used becuase its whats available, since we dont have a heat treater locally who can stick an entire space frame in an oven. And yes, the composition of TIG rods are different from gas rods, in that they contain de-oxidizers.

    Team FAST - Yes it was 4130N, aircooled. Near yield point stresses were probably reached, after the weld. I plan on trying out some "shop normalizing" and maybe some true furnace normalizing, depends on the facilities available.

    Randy, filler was added to the weld in the last picture. Stress concentration plays a factor, but when a weld unzips right next to the pass. HAZ cracking should be suspect.

    Mr. Bridgeport, you are correct, but many have claimed that air cooling is sufficient for thin wall 4130 tubing. Some claim that heating the tube to red hot and air cooling is fine also. The other interesting thing is that 4130 actually reduces in toughness when annealed, when compared to a normalized state. If a true annealing were done the impact absorbtion is less than half of 1020 Annealed.

    Michael Moore - Heres the thing about 4130 and dent resistance. Based on charpy impact testing, 4130 takes more energy to initally deform, called resiliance. But after deformation, it requires MUCH LESS energy to fail, as compared to 1020 steel, about 60% less.

    Thanks for the comments all, i have around 360 feet of this stuff to dent....so ill have PLENTY of data!

    Nick

  12. #12
    Join Date
    Mar 2004
    Location
    Granada Hills, CA
    Posts
    498
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Post

    Johnoder,

    I didnt catch your comments till just now. Im aware that many aircraft were OA welded 4130, and Ive been considering that lately. The OA process is much less dense energy wise. So there is a greater energy input, therefore a much larger HAZ. Since the base material is getting much hotter, the cooling rates are depressed causing the material to form less martensite and be more ductile.

    This would by my first guess, and I am thinking about welding some tubing with OA and performing the same test. Well see what happens!

    Nick

  13. #13
    Join Date
    Jun 2001
    Location
    downhill from Twain\'s study outside Elmira, NY
    Posts
    10,685
    Post Thanks / Like
    Likes (Given)
    3857
    Likes (Received)
    3590

    Post

    after completely welding a cluster, (OA or TIG) you're supposed to go back and play an OA torch "all over" it. Bring to a dull red heat, keep playing the torch but gradually withdrawing it, and then slowly let it cool down.

    Those photos are real eye openers. Hope to see further ones with OA, including plain old mild steel gas rod, "torch annealed" after welding, as that is what most people use for aircraft in the field.

    Thanks! Please keep posting.

    smt

  14. #14
    Join Date
    May 2002
    Location
    South Central PA
    Posts
    12,177
    Post Thanks / Like
    Likes (Given)
    1368
    Likes (Received)
    2447

    Post

    Tig with ER70S-2 rod is generally how it's done in the race car industry, at least in drag race and oval cars, because it's 'good enough' and fairly quick to do. If the joint is not overheated it will be ductile enough for 99% of the crashes experienced. A little overheat by an inexperienced welder will drasticly increase the brittleness in the HAZ, however.

    French Grimes did an extensive test welding 4130 in the early '80s that showed ER70S-2 with out preheat was the best compromise in a joint that did not receive a lot of flex. The best from a ductility standpoint was 308 stainless steel filler rod with a pre weld preheat of the joint to 300°F, with no post weld heating, cooling in open air. The 308 SS had slightly less tensile strength than the ER70S-2. 4130 filler rod was the strongest but by far the most brittle.

    The drag cars I've examined after crashes usually showed more joints separated by being pulled apart in tension rather than bent and cracked which has led me to believe that tensile strength is the more important quality. Something like a sprint car with a ladder frame that has little diagonal bracing would logically need more ductility.

    The welds in your 3rd photo are not real consistent, show evidence of electrode contamination, and possibly overheat. I'd suggest trying the test again, and also with 308SS with a 300°F preheat.

    Another point is that your test of a weld over uninterrupted tubing is not a 'real world' test. A more realistic test would be to butt weld 2 pieces together. And make sure you are not using too large of a filler rod. 1/16" is the smallest ER70S-2 that is easy to find in normal welding supply houses, and in my opinion is too big to use on .065 wall 4130 tubing. Order some in .045 and you will find that using the correct heat is much easier to accomplish.

  15. #15
    Join Date
    Feb 2005
    Location
    Posts
    8
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Post

    SLOEIT please keep pursuing this. I think there are many of us who could use some concrete examples of roll cage welding and failures.

    5X fpt W fidia control
    Powershape & Powermill

  16. #16
    Join Date
    Dec 2000
    Location
    Bremerton WA USA
    Posts
    10,522
    Post Thanks / Like
    Likes (Given)
    40
    Likes (Received)
    3782

    Post

    SLOEIT. You illustrate the need for post weld heat treatment (a long slow draw is a heat treatment) in high confidence welded steel structures. There are several parts to the vehicle structure problem: driver protection, driver containment, energy loss crumple zones etc.

    Naturally this requires a systems approach. A good design will limit the driver/passenger space to 30g's in a hard impact at the maximum anticipated speed and the balance of the structre collapes around the occupants absorbing the collision energy. The usual passenger vehicle structure incorporates all protection/energy-loss etc features in a single package whose elements are difficult to separate by eyeball inspection of the undamaged structure.

    Your 125 Joule penetration experiments are an excellent start for the shade-tree designer. They point up the need for care in welded joint design and post-weld metallurgy in terms that even a technically challenged builder can understand.

    I recall an incident from my drag racing days in a late '60's. A local yokel (no other words fit) brought his proudly home-built dragster into the pits for tech inspection. I was standing 30 feet away but I could still see "EMT" stamped on every visible piece of the roll cage. No, he was not passed to go racing.

    Some things you just can't cut corners on and driver/passenger collision protection is only part of it.

  17. #17
    Join Date
    Aug 2004
    Location
    So. California
    Posts
    293
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Post

    1020 DOM is usually safer for a roll cage because of its greater elongation properties. The 1020 will continue to bend after the 4130 has ruptured. Sometimes 4130 is used because it is processed in a more controlled envoirment and certified for aircraft use compared to commercial grade 1020. But you must always stress-relieve the HAZ on tubes with .065 wall and thicker.

    I tend to use 4130 on high-stress light-weight weldments like suspension arms. The weldments are heat-treated to increase tensile strength and resist bending or yielding (parts flex and spring back to shape). This takes better advantage of the material. If you don't heat treat for greater strength, then just use 1020 DOM to reduce costs, not just in material but tools wear out faster with 4130.

    I do destructive tests on weld samples and you can learn a lot from them. As others have noted, the welds in the pictures above would never pass aircraft certification.

  18. #18
    Join Date
    Mar 2004
    Location
    Granada Hills, CA
    Posts
    498
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Post

    Thanks for all the responses all, Im glad to see some people are interested. Here is a picture of one of the finished cars weve built. As you can see there is little room for a "crumple zone" so a balance needs to be obtained between energy absorbtion and yielding. Our current FEA numbers show minimal distortion of the space frame under severe loading. But that brings up a good question, there is no spec. in the competition for acceleration of the driver. Im still looking for where all this should fit in. But I believe It will yield some good data.



    Nick

  19. #19
    Join Date
    Jul 2004
    Location
    South East FL/NYC
    Posts
    645
    Post Thanks / Like
    Likes (Given)
    9
    Likes (Received)
    3

    Post

    Is that a mini baja? Pretty neat.

    We always use er70s-s with chromoly. I know this is repetetive but you want that ductility in your joints, those are your weak points in the structure.

    here's my two cents..
    I'd have to agree with the others about the heat treating. When welding, I bet there was a phase change in the haz. Several things can happen when welding...upon cooling residual stresses can form, but what I think could have happened in your case, is the air cooling could have hardened the 4130. Alloy steels can be hardened in air. There are a lot of variables in this case. Hopefully I gave a little insight.

    Chad

  20. #20
    Join Date
    Nov 2004
    Location
    Birmingham, AL
    Posts
    12,714
    Post Thanks / Like
    Likes (Given)
    5543
    Likes (Received)
    2238

    Post

    As has been stated, this is why the FAA certified aircraft welding procedure for 4130 is OA. TIG is allowed, but must be heat treated. The FAA reccommends heating to a dull red with a rosebud to a few inches out from the weld. This allows the tubing to cool more evenly, helping to eliminate hardening, and distributes any bound up stresses. You might want to look up the Airframe repair book (AC-4330 I think) at the local Gov't printing office. It has a lot of good info on 4130 welding, acceptable repairs, splices, etc... Might be a good thing.

    I have heard of MANY homebuuilders who do not follow the post-heat TIG technique (no requirement unless the work is on an airplane that is certified by a manufacturer) and simply TIG up the whole frame, claiming that it makes no real difference. I wish I could show all of them these pictures. That's striking to say the least. Good scientific test.

    As has already been mentioned, I would also like to see a similar test with 4130 on a silver soldered and/or brazed joint. Add to that a straight OA weld test (already mentioned) and one done with a LC1OHM(laquer-coated one hour martinizong rod...coat hanger), just for kicks on both 4130 and 1020.


Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •