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Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

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Old 12-10-06, 08:50 PM   #1
mezza
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Welded steel frame?

I may be asking an obvious question here... But why not weld steel frames?

As an ex welder myself I can't see why its not the done thing!!

Any explanation from those who know metals would be great.
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Old 12-10-06, 09:07 PM   #2
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It depends upon the alloy and process. Are you using oxy-acetylene? MIG or TIG? Carbide migration at the HAZ is a consideration with the traditional super-thin high-carbon tubing used (4130 @ 0.030"). I guess you could aleviate that somewhat with pre-heating before and post-weld annealing to avoid forming brittle martensite. You tend to end up using thick tubing with butted ends to help create stronger joints.

The newer stainless alloys can probably deal with welding better.

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Old 12-11-06, 10:28 PM   #3
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If your a good tig welder it shouldn't be an issue. lugs and tig are equally as strong.
lugs do look better. but i think the process takes longer
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Old 12-11-06, 11:44 PM   #4
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I'm warming (scuse the pun) towards TIG welding Stainless steel... Seems like the overall bests option for my needs

I'm not bothered about pretty lugs and I can weld like Errol Flynn swashbuckles with a sword. A bit of a skill transfer but should be do-able........

As long as tig'ed Stainless doesn't lose too much strength...
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Old 12-11-06, 11:52 PM   #5
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Some of my favorite bikes are welded steel.
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Old 12-11-06, 11:59 PM   #6
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With TIG welding, it pretty much is "the done thing" these days. But until fairly recently, the thinness of the walls of the tubes that went into top-notch frames meant that the heat from welding reduced the strength of the steel at the joints by too much for safety. Hence lower-temperature brazing, using brass on many good frame and silver (lower temps yet, but much expensive than brass, and often inaccurately called "silver soldering") on the best.

Oh, and if you see a lugless high-zoot frame from the 1970's made of Reynolds or Columbus tubes (or Ishiwata, or Super Vitus), I would bet the ranch that it was brazed without lugs and not welded.

In order to weld instead of braze, you had to do one of two things: thicken the walls of the tubes of the existing steels, or develop new steels that can take the higher heat of welding and still be really thin-walled. Both have been done. The old Schwinn Varsity's and Continentals are examples of thicker tubing walls - and they have the seriously increased weight to prove it. More recently, Reynolds, True Temper and others developed steel alloys that can take much higher temperatures than the previous top-of-the-line steel tubes as well as being much stronger, allowing for even thinner tube walls and even less weight. (Keep in mind that Reynolds 531 is/was 1930's technology - it was used in British Spitfire fighters in WWII.) The development of these new steel alloys is why high-end TIG-welded steel frames can exist at all, and it's why their advent has been comparitively recent.

Of course, there are some folks out there (hello, Rivendell) who believe that even the heat-treated steel tubes like Reynolds 853 should be brazed instead of welded. Aesthetically, I agree. As far as metalurigal properties, this is where I get off and leave it to the rest of you to fight out.
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Old 12-12-06, 12:18 AM   #7
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Quote:
Originally Posted by bikingshearer
Aesthetically, I agree. As far as metalurigal properties, this is where I get off and leave it to the rest of you to fight out.
Well, you've been a great help and your thoughts are much appreciated!
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