Er70s-2 on 4130

[mattfx81]

I have a couple of small dinks on a 4130 Chromoly bicycle frame that I intend to fill by means of tig welding before the frame goes to powder coat. So far with a a quick google search I have come up with ER70S-2 being the filler rod to go with. Is their any pre-treatment of the weld area ie heating required before welding?
Also is ther a supplier here in theUK that holds these type of rods, as I cant find a stockist online anyway.

Matt

 

[chunkolini]

That might be a dodgy move, some of the higher end Cro/Mo frames were heat treated you might be making the damage worse by welding the affected area. If it is a purely cosmetic repair I would be inclined to use a bit of filler.

There are some highly knowledgeable droids on this site who will know what to do.

Chunko'.

 

[TechnicAl]

Id do as chunko says .

If you are intent on welding it the s-2 is ok and I wouldnt bother with the preheat, but there are circumstances where this is not good advice. You need to know the heat treated condition of the tube to be certain.

 

[hotrodder]

ER70s-2 is generally known as 'A15' in the UK and is the most commonly used mild steel TIG wire (er70s-6 / A18 being the other common flavour) and is available from any welding supplier

As said depending on the location of the dinks and quality of the frame it's very possible to cause more damage by welding i.e. many frames use butted tubing (variable wall thickness) to take into account the 'damage' caused by welding

In the case of heat treated steel frames they are generally constructed from pre tempered tubing rather than heat treated after fabrication. Welding a heat treated frame away from the thicker walled butted sections (where they're designed to be welded) is definately a bad idea.

Someone here will probably know of a filler that's compatible with the powdercoating process, could always ask your chosen powdercoaters. Or silver solder it (high end frames used for bottle bosses, cable guides etc) / braze it (if it's not a real high end light weight jobby)

 

[graffian]

A suitable filler that comes to mind, I have a couple of tubes ready to fill some gouges in my primary case, is JB weld. I am told it has to be Classic, not the quick setting one[that doesn't stand the temp]. I bought the tubes I have in JC Pennies in 1989, not checked it to see if it's still any good yet. I haven't the faintest idea where you get it on the right side of the moat though.

There are plenty of other fillers, you will find mentioned, but they tend to be none too cheap. Something I read the other day, which might be worth looking into, some lead free solders are said to work? The coating temp with my powder is 185ºC, so it has to remain hard above at that temp.

There are several coating forums, columbia coatings and powder by the pound are probably the best of the ones I have seen. Plenty of posts on them mention filler. Or ask the coater, they might well give you some of whatever they use. If you get given something common let me know, The only filler I have used so far is bronze;-)

 

[Nimbus]

If it's a butted tube it could be 0.6mm thick (or less). Use something like chemical metal or if you really have to then silver solder it. (The butting is to increase the metal thickness in the heat affected zone to maintain structural integrity)

 

[mattfx81]

Good advice, cheers. I will look for a suitable filler.

Matt