|
|
Hi all, first post here so I'll try and make it memorable (in a good way).I started welding aluminum cylinder heads 16 years ago and in an auto machine shop there wasnt much steel to be welded. I have worked in a few shops that did nothing but steel but 80+ percent of my experience is aluminum, both TIG and Mig.The economy has me looking at other avenues. one of which is TIG of chromoly. I have built chromoly chassis for a little over a year but it was strictly MIG. I have recently found a place that is considering employing me after i pass a test. Failure is not an option here so I am getting all my ducks in a row before I pull the trigger on this one and only test I've already recieved in the mail. The test basically consists of welding a cluster of .049 x 1" x 6" long 4130 condition N tubing and I was hoping that some of the more experienced welders who do this type of thing day in and day out would kindly offer some insight as to setup, technique, etc. I will be using a Miller 180 borrowed from a friend. I am looking for the best possible results so to be considered for certification. I would really appreciate some direction from the pros here on welding web as the intimidation factor is high for someone who has only prepared for a certification but didnt get the chance to follow through.
Reply:first thing i want to know is what does this cluster look like? and what are the testing requirments? does it have to be full pen? and what kind of testing are tehy doing? biggest thing i can tell you having done aircraft work that is similar to that is to start your tie in twice as far back as you think you need to so you can get the previous weld nice and hot before you start to continue it. might not be a bad idea to mock the same test up in aluminum and see how it goes.
Reply:all testing is in accordance with AWS D17.1non-destructive and destructive testing[IMG][/IMG]
Reply:Move quickly, and don't undersize your welds.
Reply:thanks guys,i plan to mock this thing up more than once before i send it in. thanks, Supe. i figured as thin as the material is you would want to move fairly fast to avoid any burn through. any thoughts on what cup would work best? ive seen, what my lack of knowledge, would call a diffuser with a screen built in. would that help?the filler material is 1/16th. like i said... i want to have every possible base covered before i strike an arc.
Reply:Clean, clean, clean, post flow, post flow, post flow!!!!!!!!Go hot, or go home!
Reply:If you want to really impress them, leave a 1/16" gap and weld with 100% penetration per the old FAA test. What kind of company is this for?
Reply:Originally Posted by sal1220fthanks guys,i plan to mock this thing up more than once before i send it in. thanks, Supe. i figured as thin as the material is you would want to move fairly fast to avoid any burn through. any thoughts on what cup would work best? ive seen, what my lack of knowledge, would call a diffuser with a screen built in. would that help?the filler material is 1/16th. like i said... i want to have every possible base covered before i strike an arc.
Reply:Originally Posted by deucedj22Clean, clean, clean, post flow, post flow, post flow!!!!!!!!
Reply:Originally Posted by SupeIt's not just to prevent burn through, it's to minimize heat input and reduce the heat affected zone to reduce the risk of cracking. If the part is not to be PWHT'd, then odds are you'll be using mild steel filler, and sizing the welds properly will ensure proper dilution and also minimize excessive hardness and cracking.
Reply:PWHT = Post Weld Heat Treatment (Reheating to a modest temperature and slow cooling after finishing the weld)ER80S-D2 is a mild steel filler rod; a bit higher strength than standard TIG rod, but more compatible with Cr-Mo steel.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Originally Posted by sal1220fthanks guys,i plan to mock this thing up more than once before i send it in. thanks, Supe. i figured as thin as the material is you would want to move fairly fast to avoid any burn through. any thoughts on what cup would work best? ive seen, what my lack of knowledge, would call a diffuser with a screen built in. would that help?the filler material is 1/16th. like i said... i want to have every possible base covered before i strike an arc.
Reply:Originally Posted by A_DAB_will_doPWHT = Post Weld Heat Treatment (Reheating to a modest temperature and slow cooling after finishing the weld.
Reply:i see it now....
Reply:Originally Posted by sal1220fall testing is in accordance with AWS D17.1non-destructive and destructive testing[IMG][/IMG]
Reply:I always use 70-S2 TIG wire on those drag motor cycle and race car chassis, made of chrome steel. Usually called chrome-molly steel. But I weld slow and hot, I let the puddle mix it up a while, while it is molten. Then cool it fast, then move on just a tiny bit, and melt half of it again. So I want the very soft material in the 70-S2 wire.The strength you gain from the new structure you create with that weld, will be so much stronger then the material. That is why I want the flexibility and give of the 70-S2 rod. And nothing any more brittle. You will not need it in my opinion.Welds almost always tend to break next to the weld. http://www.Rockwelder.com/Welding/St.../SteelTIG.html Sincerely, William McCormick
Reply:Originally Posted by William McCormick JrI always use 70-S2 TIG wire on those drag motor cycle and race car chassis, made of chrome steel. Usually called chrome-molly steel. But I weld slow and hot, I let the puddle mix it up a while, while it is molten. Then cool it fast, then move on just a tiny bit, and melt half of it again. So I want the very soft material in the 70-S2 wire.The strength you gain from the new structure you create with that weld, will be so much stronger then the material. That is why I want the flexibility and give of the 70-S2 rod. And nothing any more brittle. You will not need it in my opinion.Welds almost always tend to break next to the weld. http://www.Rockwelder.com/Welding/St.../SteelTIG.html Sincerely, William McCormick
Reply:Also a good preheat. Slowly by heating them with low power till they fuse with the smallest tack you can make. Sincerely, William McCormick
Reply:I has not been said here yet(I think), but you may consider it to be equally as bad to put so much heat to it as to distort the main piece at the bottom. Depends on the test parameters I suppose. Someone here will know.
Reply:Originally Posted by WHughesI has not been said here yet(I think), but you may consider it to be equally as bad to put so much heat to it as to distort the main piece at the bottom. Depends on the test parameters I suppose. Someone here will know.
Reply:that shouldn't be to hard for you to do. i will side with the slow and hot method. i would also start in the tightest spot between the angled sections and the upright in the center and work my way out. when you go to tie in for the other half start back about 3 dips worth and then go. a gas lens is definitely a good idea if not a necessity i would get a number 5 and a number 8 if you are using the common wp-20 torch.
Reply:Ok here are some hints from the airplane world. Weld the middle tube first, then then fit and weld the outer tubes. Always weld with the "grain" , this means from the "tee" portion to the "lap" portion of a tube cluster. This is a particular oddity with 4130 as its actually known to form tiny cracks if welded against the "grain". This can be more or less critical depending on the percentages of certain alloying elements in the metal. As far as the gap and D17.1 , I doubt they mention anything of fitment, its a pretty loose standard. General rule of thumb is to use a gap thats the same as your filler thickness. ER80 series filler is a bit overkill, but its race guys......usually they dont know any better , but if thats what they want, its their sandbox. Keep the fillets larger, small fillets are for OCC motorcycles that never run.
Reply:Originally Posted by quasi that shouldn't be to hard for you to do. i will side with the slow and hot method. i would also start in the tightest spot between the angled sections and the upright in the center and work my way out. when you go to tie in for the other half start back about 3 dips worth and then go.
Reply:No I mean the physical location and sequence of welding on the cluster. Each tube is typically welded in 4 segments, all starting at the "fillet" part of the weld, and ending at the "lap" part, I.E. ending where you just have a thin sliver of the vertical tube meeting the side of the bottom tube. So you have 4-90degree welds to complete the tube, got it? By doing this and alternating sides as you weld you limit distortion as well.Yep the instructions they gave you are exactly what I said.......gee we must have gotten it out of the same 1935 design handbook
Reply:Originally Posted by makoman1860 No I mean the physical location and sequence of welding on the cluster. Each tube is typically welded in 4 segments, all starting at the "fillet" part of the weld, and ending at the "lap" part, I.E. ending where you just have a thin sliver of the vertical tube meeting the side of the bottom tube. So you have 4-90degree welds to complete the tube, got it? By doing this and alternating sides as you weld you limit distortion as well.Now to me, I could not properly weld the other two pipes if I did the center pipe first. If my life depended on it, I would weld the outer two first. But you cannot fight city hall. Sincerely, William McCormick
Reply:Originally Posted by sal1220fsorry if i may seem a little slow here.... if i understand correctly you are saying to weld 2 starting from the joint of the "L" in the same direction(counter-clockwise for me)1/4 of the way and finishing the last 2starting in the same spot but in the opposite direction?
Reply:Honestly, I wouldn't make a big deal about this as you're thinking it will be. Most race shops are just going to give you a visual. They want to see that you can contort as needed to weld tubes and tube clusters, while having a good looking weld without blowing through thin materials or undercutting (that's why they're giving you such a thin wall rather than the .083 and heavier norm). Very few shops other than the big name guys do any sort of destructive testing whatsoever.
Reply:Originally Posted by Supe Very few shops other than the big name guys do any sort of destructive testing whatsoever.
Reply:Originally Posted by makoman1860Yep....1/4 mile at a time....tire shake is a really neat way to see how well your design and weldments are holding up......or arent. Seems like an expensive way to go about it though .
Reply:Originally Posted by SupeYour big name fuel car shops aren't so lax about their procedures, thankfully. They also do a fair bit of in-house tensile testing, etc. I was surprised to see just how in-depth they went with their process control.
Reply:Originally Posted by quasia gas lens is definitely a good idea if not a necessity i would get a number 5 and a number 8 if you are using the common wp-20 torch.
Reply:Originally Posted by makoman1860If you want to really impress them, leave a 1/16" gap and weld with 100% penetration per the old FAA test. What kind of company is this for?
Reply:Originally Posted by sal1220fone more(for now) question mako. if i were to leave a 1/16 root gap would you concur with Mr. McCormick about purging the tube?
Reply:Originally Posted by dave powelson ???As far as purging/root gapping, etc.--- what's wrong with asking the employer exactly how do they wish this coupon to be done??? Doing some prior practicing--as you've mentioned, will help much.
Reply:[QUOTE=dave powelson;277489] Pretty welds are the focus of race car stuff, to the expense of criteria that is functional.)QUOTE]Too true......Scary huh?I dont know about the gap causing distortion, I always noticed that ( on tubing clusters ) distortion followed penetration moreso than starting gap. I think the reason these car guys have almost zero distortion is that they are getting about 50% penetration ( on the welds ive sectioned ) and they had zero gap ( cant shrink if you have tight metal to metal contact with no melting ). Ive done test welds with varying gap and 100% penetration, and providing the weld width is the same in all cases, so was distortion. Just my observations
Reply:Originally Posted by makoman1860I dunno, maybe they have improved a lot in the last couple years. When I was seeing some of the designs/work on the force cars from 2 years ago, the detail of design construction just wasnt there. Lack of gussets, doublers, etc. etc. Lots of repaired cracks ( I would think that would be a red flag ). The guy that did welding in the pits for them had a hot-rod truck, and seemed to be more into "image" than "substance". Just my take on it. Maybe it depends what your used to as well.
Reply:To me creating a gap to fill with a filler wire. Filler wire that is no where near the material to be welded makes no sense. I think that is just an engineer making stuff up. If you look at most critical parts in industry, they use no space, and often fuse the part. Using no filler wire. This has been the most successful type of weld in industry. Filler wire posses a problem no matter what it is made of. Even though many metals are strong, we often create or use a filler material very different then the material being welded. Because during the rather violent heating of a small area, the metal can breakdown, or disassociate from elements in the metal, or form new bonds that are not useful to strength. I have found that when you fuse the metal, it is the strongest of all welds, except for hardened aluminum and hardened magnesium. One of the most overlooked things about fusing metal, is that you have to properly, preheat the metal totally and perfectly, slowly in order to weld it. This saves the metal from harsh polarization, that can effect the metals structure. This is something most welders do not do. And because of that you get failure. So if you use a filler wire, the best thing to do is, fuse the metal to be welded. This would require zero gap, or a very small gap. Getting the metal to fuse without rod. While still there, if you want to bring the surface up to a certain level with filler rod, you can. Then, cool, and only move a small distance, and reheat half of the puddle you just did. Most people talk about undercut as if it is your enemy. I can undercut and destructively test to show that the undercut part actually in many cases is stronger then the filled in part. Because the weld is plenty strong, too strong in most cases. The thinner undercut weld often allows a bit of stretching and give, that allows the whole part better overall tenacity. Industry knows this, it is actually good engineering. Aluminum being one of the few exceptions. Partially due to the filler materials, partially due to the way aluminum bends and gives, and mostly due to the way aluminum anneals during welding. There is usually such a large difference in aluminum from its annealed state to its hardened state, that you have to either re harden, or re engineer the part to weld it. So you do not introduce weakness. If you weld annealed aluminum, the weld is plenty strong. But most of a welders aluminum material is hardened. Because annealed aluminum is almost like lead.One thing about the old 6061 T6 and the newer 6061 T6 511 is that you cannot totally anneal the material. The old 6061 T6 could be totally annealed and you could bend it into a pretzel without cracking. The newer 6061 T6 511 is ruined. Sincerely, William McCormick
Reply:I found that I really had to scrub the joint with scotchbrite before welding it. I also held the post flow for probably at least 10 seconds. Over kill? It didn't crack.Go hot, or go home!
Reply:Clean the inside of the tube as well as you do the outside. Chamfer/prep all fish mouths so all edges are the thickness of the tube. When the fitment is welded in the vertical position be carefull not to focus to much heat on the top side/vertical tube. In my fitments that I have cut apart, the inside of the vertical tube will show where it has sucked into the bead when doing full penetration actually undercutting from the inside. I was always taught that the strongest fitment in tube welding was when the fitment had zero gap. Tube welding is an art in itself and welding a test piece on a bench is no wheres close to welding on a frame. There is a lot of standing on your head welding. Wether it be right or wrong I prefer to fusion weld (no filler rod) the whole tube first. I always try to skip around all over the frame and hit a bunch of joints so as to not put to much heat into one weldment. I am not as skilled as most of the people on the board but these techniques have worked for me. I have cut apart dozens of my fitments and been thrashing **** since 1978. Good luck
Reply:Here are my thoughts on this.I've never actual welded tubing this thin before, but if I was you I would be fitting this up with barely any root gap. Reason being if you put abit too much heat into that, it's likely going to key hole on you and your likely to get some ugly grapes on the inside. (Oopps, hope they don't look in there.) So anyways, I'd fit it up as tight as possible, and run it slow and hot. I'd be willing to bet you will almost have 100 percent pen with tubing that thin. I know that when we do shd 40 stainless, we basically butt it up and run it, and if you look on the inside it looks perfect. Have fun, and get practicing.Matt
Reply:Originally Posted by Matt80Here are my thoughts on this.I've never actual welded tubing this thin before, but if I was you I would be fitting this up with barely any root gap. Reason being if you put abit too much heat into that, it's likely going to key hole on you and your likely to get some ugly grapes on the inside. (Oopps, hope they don't look in there.) So anyways, I'd fit it up as tight as possible, and run it slow and hot. I'd be willing to bet you will almost have 100 percent pen with tubing that thin. I know that when we do shd 40 stainless, we basically butt it up and run it, and if you look on the inside it looks perfect. Have fun, and get practicing.Matt |
|
发表于 2021-8-31 23:48:20