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| Turbo exhaust manifold https://www.slantsix.org/forum/viewtopic.php?t=18101 |
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| Author: | Matt Cramer [ Wed Jun 21, 2006 7:32 am ] |
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Sorry if I wasn't clear. I just wanted to know the melting temperature of the brazing rod. |
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| Author: | DionR [ Wed Jun 21, 2006 8:26 am ] |
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Quote: Sorry if I wasn't clear. I just wanted to know the melting temperature of the brazing rod.
Oh, sorry.From what I understand, brass or bronze melts at 1600-1800 degrees, bronze being the higher. I'm not sure exactly what brazing rod is made from, but wikipedia said that the temp range for brazing matched these numbers. Interestingly, they said that brazing brass has a strength and hardness close to that of mild steel. I'm glad you asked the question as I will have to make sure that he uses a higher temp rod so I don't run into problems. It's my understanding that exhaust temps can hit 1600 or 1650, so I had better make sure I have a factor of safety. Don't know if exhaust gas temps equal manifold temps, but I suppose I should be careful. |
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| Author: | Sam Powell [ Thu Jun 22, 2006 7:40 am ] |
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When I went to a local shop here that does custom fabrication using all kinds of systems, including welding, I asked the welder, who happens to be a Mopar guy, if he would weld on an old exhaust manifold. He said that the repeated heating over the years cooks the carbon out of the old cast iron, thus making it weak, and not a good candidate for welding. He made sense, and convinced me that welding on these old manifolds was a little risky. I thus went with Dutra manifolds, and welded up a set of steel tubes,two into one for my turbo. It is not particularly strong, and I suspect I might have to redo it some day in stainless, but it does work. I did jet coat it to hold down the external rust, but it will still get cooked pretty badly from the turbo heat, and eventualy weaken. They recommend supporting the turbo with a brace so the manifold does not do all the work of supporting the turbo. |
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| Author: | Matt Cramer [ Thu Jun 22, 2006 10:11 am ] |
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Quote: From what I understand, brass or bronze melts at 1600-1800 degrees, bronze being the higher. I'm not sure exactly what brazing rod is made from, but wikipedia said that the temp range for brazing matched these numbers.
Bringing a metal close to its melting point will also make its strength drop off rapidly. The classic example is a blacksmith's forge - the red-hot metal the blacksmith hammers on is well below its melting point, but it's much easier to hammer the metal into shape at those temperatures because its yield strength is lower. And exhaust can get as hot as the metal the blacksmith is pounding on. Interestingly, they said that brazing brass has a strength and hardness close to that of mild steel. I'm glad you asked the question as I will have to make sure that he uses a higher temp rod so I don't run into problems. It's my understanding that exhaust temps can hit 1600 or 1650, so I had better make sure I have a factor of safety. Don't know if exhaust gas temps equal manifold temps, but I suppose I should be careful. The exhaust manifold temperature is lower than the average exhaust temperature. However, the temperature at the inside of the manifold will get pretty close. The temperature then drops as it goes toward the outside surface, with the amount of temperature drop determined by the material thickness. But even thick cast iron manifolds can get hot enough to glow visibly. That's why I am a bit wary of brazing a flange on. Just because the rod is as strong as steel at room temperature does not mean it will be as strong as steel when heated to operating temperature. |
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