4130 should have no issues with brazing. If you are having issues, it is purely from the technique, process and skill of the person doing the work. Overheating is the usual culprit.
4130 should have no issues with brazing. If you are having issues, it is purely from the technique, process and skill of the person doing the work. Overheating is the usual culprit.
Do think there are some applications on steel fuselages where brazing would be just fine. Those long brackets for attaching skins, to avoid bending the longerons from heat, etc.
Gday to continue this thread,Can I tack weld the frame with the mig? The wire is the er70s and is this compatible with the mild steel filler rod used with the oxy?
You can tack with Mig. Be careful not to make the tack too big because you'll need to go over it during the final welding.
I was reading this thread and am intrigued by the suggestion/interest of/in brazing an airframe. I have to wonder why? Brazing is an unproven process for airframes. Also, in my experience it has been a more difficult process to produce. I've found it much easier to control heat affected areas, filet size and, all other aspects of a weld joint versus a brazed joint. Torch rigs and No. 7 rod are cheap. I'd stick with what we've been flying on for 100 years. I do like brazing for repairing cracks in castings such as boat exhausts, blocks, etc. Anyway, just my opinion and experience.
I aggree 100%. However I do have to argue with you on a point of brazing not being "proven". Back in the WW1 timeframe you do see brazed structures in airframes. Typically they used "lugs" common to bicycle manufacturing at the time. The Wrights used braze welding on the 1903 and later flyers (bicycle guys ya know). The extensive use of brazing vs. welding in the pre 1925 period seems to have been directly related to the steel manufactures ability to control some of the alloying elements in their tubing and sheet....mainly sulphur. Once the root cause of welding failures was found to be in the steel itself, the manufacturers changed the steel to be applicable to welding....and welding thus took off ( no pun intended ). Back to the present though.....cant beat RG-45 and a nice safe, sound and comfortable system of welding.
Aaron's advice is spot on; RG-45 is likebutter. You'll love it! It's worth asking and paying extra for. AndI've found it will flow into a make-your-mother-proud fillet ifre-heated with a slightly carburizing torch flame. Anybody know ifsuch a re-heat significantly affects the strength of the weld? Surelydon't want a weld to become brittle and the additional carbon has tobe changing the character of the metal in some way.
For what it's worth, although I'llcontinue to experiment with ways brazing might make building quicker,easier or better, I have found a couple of problems with the process.It's the flux. The MSDS brings up some significant issues for asmall space with less than industrial ventilation. And, after thebraze has cooled, the flux must be completely removed or the residual acidswill cause corrosion. Corrosion is bad.
The journey is the reward.