Welding something onto a heat treated chromoly structure

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I was thinking of tig welding some brake mounts to the forks on my BMX bike..The forks are 4130 Chromoly and heat treated..I believe the tubing is something like .049" thick...Would welding on the heat treated tubing be advisable? Or can I just heat them up and weld Thanks
Reply:use er70-2. No need for preheat just make sure the metal is room temp(70 degrees). ER70-2 doesnt require heat treatment after welding 4130.
Reply:Originally Posted by OverRaTeDuse er70-2. No need for preheat just make sure the metal is room temp(70 degrees). ER70-2 doesnt require heat treatment after welding 4130.
Reply:1-Posting some pics of the mounts, position, forks and type of weld joint intended would help. If the weld is transverse (across the fork tube) and not longitudinal, that can induce failure.In any case, this will require decent TIG welding on the first and only try. Can you say 'undercut', 'overheat' and 'lack of fusion'---Johnny?2-Concerning post weld normalize--I wouldn't be so dead certain that it's not required or a bad idea.The catch-all phrase of 'heat treat'--doesn't say squat as to 'what' heat treat was employed. Good idea to ask the manufacturer, at the same time query as to welding on their forks....I'll bet I know what they'll say.Last edited by dave powelson; 04-26-2011 at 01:47 AM.Reason: additionBlackbird
Reply:Just braze the mounts.  Many of the steel bike manufacturers will braze the connections in order to avoid tempering the tubes from the factory.  As a bonus, you won't burn through the steel.
Reply:Any weldment or braze weld will destroy the heat treatment at the point of your attachment. The more heat you apply, the larger the area that will be affected.You have no way of knowing what that heat treatment was, and if you did, you would have to reheat treat the entire unit, unless the treatment was simply a normalizing of the factory welds. In any case, if you weld on the forks, the material will still have the strength of 4130 in untreated condition. There may be a slight loss of integrity, but unless this bike is recieving a lot of abuse, there shouldn't be any issues. With thin wall tubing there is no need for preheat, just make sure that the metal has been properly cleaned first, and only weld along the fork, not around its diameter.
Reply:Originally Posted by ak4130I was thinking of tig welding some brake mounts to the forks on my BMX bike..The forks are 4130 Chromoly and heat treated..I believe the tubing is something like .049" thick...Would welding on the heat treated tubing be advisable? Or can I just heat them up and weld Thanks
Reply:4130 your are gonna get a lot of different opinions on what to do. Everybody is always right on this subject. lol. As others stated I would check to see what the heat treatment is. If its to normalize it- which was my assumption since that is the typical heat treatment on bicycles...then my advice is correct.
Reply:Thanks for all the replies.. The mounts would be like on the forks in this link.http://www.odysseybmx.com/catalog/forks/freestyle-fork/.The 2 studs sticking out..And this is actually the same  forks I want to weld onto-I just have the factory  brakeless versions of these.. Honestly they are not really going to be abused, I mainly just crusie around on my bike these days every now and then..I just dont want some kind of catastrophic failure where the fork leg breaks off 2 days after I weld them or something..
Reply:i wouldnt do it at all.  the front forks arnt somthing you want to skimp on.  i had a set of forks bend and almost brake, it was not fun, ended up on my face.  i would get the forks that were set up for the disk brakes.  yeah itll cost more but they wont brake.  and if you are putting disk braeks on just to tool around thats a waste also IMHO.  and all bikes made of cromeolly, aluminum are heat treated to equlizs the tensile straenthLast edited by USARMY44B; 04-27-2011 at 04:14 AM.WELD TO LIVE LIVE TO RIDEA bad welder blames his equipment, a good weldor can lay a perfect bead on any thing
Reply:Is the cost of the right forks worth a face plant?  You're going to distort the forks when you weld on them too.My name's not Jim....
Reply:The forks shown in the link look like a good design and excellent workmanship.I would just buy those and not worry.AWS certified welding inspectorAWS certified welder
Reply:Originally Posted by Donald BranscomThe forks shown in the link look like a good design and excellent workmanship.I would just buy those and not worry.
Reply:Also it would probably be best cope the lugs to fit the tube and weld them on rather than drilling any holes in the tube to mount them before welding if at all possible.
Reply:I used to ride a long time ago and they made plates for adapting brakes like the 990 onto the frames and forks. some of them with the big bolts were actually pretty decent and ridged. Not quite as good as the welded on studs but they were pretty solid and worked great. Just another option. Here is a link for what I am talking about. i am sure there are others. http://www.danscomp.com/489057.php?cat=PARTSMillermatic 252Lincoln 175 plusTA 185tswTA 161stlhypertherm pmax 45Victor torchHenrob torchAn S10 for each day of the week
Reply:Originally Posted by OverRaTeD I weld thin 4130 everyday down to .027 wall.