Framebuilders - Q for Falanx re mixing grades of SS.

Assuming the lower corrosion resistance is not an issue, are there obvious downsides to using a ferritic steel, say 436, with a martensitic steel, say KVA's MS2 (which I believe is similar to 410)?

The joints between them would be silver brazed not welded.

What's the application?

Basically I'm looking for something stronger than 304 with which to reinforce tube joints. The easiest explanation would be to think of the 436 as forming lugs into which the KVA MS2 tubes are brazed.

If you're looking to prefab a lug-like assembly, then ferritic isn't the way to go. Its grain growth is bloody horrendous with multiple heat inputs. You're better off with cast stainless lugs. Or even, a high carbon, high nitrogen austentic stainless wrought tube. thinks like the Nitronics.

If you want me to try to find you some tubing of the right dimensions in a more amenable material and post them to you, I can do that.

Yes please.

I need 38.1 OD x 1.6 WT and 25.4 OD x 1.6 WT. I Probably only need a metre of each at this stage but if I have to buy more I will.

I'll pay all costs of course. I have a Fedex account but Royal Mail is generally far better from UK to Aus.

I'll see what I can find :-)

If you're going to essentially make lugs - what are you doing about the BB shell?

I'm not going to make lugs.

I'm not sure how to describe what I'm trying to do except that it's basically the reverse of what Tom Kellog at Spectrum does, which is to fillet braze "lugs" into which the tubes are then brazed. What I'm trying to do is to tack a thicker section on to the end of the tube, mitre the whole thing then braze it together.

I have no idea if it will work. If it doesn't, I'll go back to plan A which was to TIG lugs together and then braze tubes into them. I'm well aware that this sounds crazy, unnecessarily complex and that I'm rapidly getting out of my depth. I'm primarily concerned with investigating the acoustic behaviour of the joined tubes. Neither straight TIG nor standard fillet brazes achieve what I'm looking for.

BTW the 25.4mm x 1.6 tube was for the chainstay joints, if I go to 23.5mm chainstays I'll need 26.7 or thereabouts. One of the local suppliers carries that in 304, is it available in the higher strength tubing?

'Lugs' was perhaps the wrong word, but in principle that's as close as I could describe them.

304's only strengthened by cold work, and deep-freezing and cold work, both of which are undone by the heat cycle of welding or brazing.

I'm still wondering if cast stainless lugs wouldn't be better for what you're attempting. They are readily available, in a number of simple and ridiculous geometries, which would give you some degree of acoustic modulation.

I'm casting around offcut holders for 414, 415, 422, 431 stainless tubing, and maybe even random tubes in 15-5, 13-8 kinda thing. I'll see what they're coming back to me with. Might see if there's any ludicrously small bits of APX4 around.

What if you were to go loco and do this the other way round from some road frame manufacturers and make these brazed on 'luggettes' from nont-stainless, higher strength steel and have them painted, with polished tubes? I wonder how that would look...

While I'm on the subject, what about monel? I know it's ridiculously expensive but that might actually work in my favour making it easier to purchase small lengths of tubing.