Original Posted By: "walter evans"
High-end bicycle frames are chrome moly tubes brazed together (usually but notalways into forged terminals) and they see a lot more stress than our fittings.I doubt that brazing is more prone to alter the make-up of the metal than weldingwhich requires a much higher temperature.f"http://explorer.msn.com">http://explorer.msn.com________________________________________________________________________________
Pietenpol-List: WELDING/BRAZING
Re: Pietenpol-List: WELDING/BRAZING
Original Posted By: "Barry Davis"
Chris is right on this one - although there is a method of brazing 4130 thatprovides sufficient strength. You use a silicon bronze with a liquid fluxin the acetylene line. This has been used on (mainly) British racing carslike Lola and McLaren instead of actual welding. This provides tube joinsthat are just as tough and flexible as the parent 4130, but is much fasterthan welding. It also provides a bit of build up at the joins. DO NOTBRAZE 4130 without using the proper techniques!>> Guys,>> I will quote from Performance Welding by Richard Finch who is an expert in> welding, is in the aerospace industry, and wrote the parts of AC 43-1B> relating to welding. He says, and I quote without permission:>> "Brazing Steel>> Always avoid brazing 4130 steel. The reason to not braze chromemoly is> that the steel has a definite grain structure that actually opens up at> medium red brazing temperatures. When brazing alloy is melted onto the> steel surface, it flows easily into the many small cracks and crevices in> the chromemoly steeel. Then as the braze joint cools, the brass will not> compress and it forces MAJOR cracks to form in the 4130 steel. Often, a> brazed 4130 steel part will crack completely in two before your eyes as it> cools.>> Mild steel (1020, 1025, and so on) is ready made for> brazing..........Brazing, when done correctly, can last as long as any> other metal-joining method. And it can be as strong as fusion weldingwhen> it is done correctly.">> Chris Bobka> EAA Tech Counselor________________________________________________________________________________
Chris is right on this one - although there is a method of brazing 4130 thatprovides sufficient strength. You use a silicon bronze with a liquid fluxin the acetylene line. This has been used on (mainly) British racing carslike Lola and McLaren instead of actual welding. This provides tube joinsthat are just as tough and flexible as the parent 4130, but is much fasterthan welding. It also provides a bit of build up at the joins. DO NOTBRAZE 4130 without using the proper techniques!>> Guys,>> I will quote from Performance Welding by Richard Finch who is an expert in> welding, is in the aerospace industry, and wrote the parts of AC 43-1B> relating to welding. He says, and I quote without permission:>> "Brazing Steel>> Always avoid brazing 4130 steel. The reason to not braze chromemoly is> that the steel has a definite grain structure that actually opens up at> medium red brazing temperatures. When brazing alloy is melted onto the> steel surface, it flows easily into the many small cracks and crevices in> the chromemoly steeel. Then as the braze joint cools, the brass will not> compress and it forces MAJOR cracks to form in the 4130 steel. Often, a> brazed 4130 steel part will crack completely in two before your eyes as it> cools.>> Mild steel (1020, 1025, and so on) is ready made for> brazing..........Brazing, when done correctly, can last as long as any> other metal-joining method. And it can be as strong as fusion weldingwhen> it is done correctly.">> Chris Bobka> EAA Tech Counselor________________________________________________________________________________
Pietenpol-List: Piet List: welding
Original Posted By: Jack Phillips
In our EAA chapter, we have seen three failures of 4130 tubing onairplanes that were tig welded. one was a landing gear, motor mount, anda couple of main structure pieces. All on different aircraft, alldifferent manufactures, all tig welded. All welds failed or cracked veryclose to the weld. It seems that the weld caused a great amount ofstress ajdacent to the weld. The welds were not post weld heat treated(some call normalizing). At least when gas welding, it is a very simpleprocess to do the post heat treating.I own a tig rig, but I bought a Harris aviation torch ( around $110) andrented tanks. After a class with George Baing and about 20 hours ofpractice, welds are looking better that old Cub welds. ( have a welderlook over your shoulder from time to time and cut the welds to look atyour progress)I decided that investing the 20 hours was worth the piece of mind I getwhile flying.Barry DavisGN-1Jr. Ace________________________________________________________________________________Date: Sun, 04 Mar 2001 19:50:00 -0500
In our EAA chapter, we have seen three failures of 4130 tubing onairplanes that were tig welded. one was a landing gear, motor mount, anda couple of main structure pieces. All on different aircraft, alldifferent manufactures, all tig welded. All welds failed or cracked veryclose to the weld. It seems that the weld caused a great amount ofstress ajdacent to the weld. The welds were not post weld heat treated(some call normalizing). At least when gas welding, it is a very simpleprocess to do the post heat treating.I own a tig rig, but I bought a Harris aviation torch ( around $110) andrented tanks. After a class with George Baing and about 20 hours ofpractice, welds are looking better that old Cub welds. ( have a welderlook over your shoulder from time to time and cut the welds to look atyour progress)I decided that investing the 20 hours was worth the piece of mind I getwhile flying.Barry DavisGN-1Jr. Ace________________________________________________________________________________Date: Sun, 04 Mar 2001 19:50:00 -0500
Re: Pietenpol-List: Piet List: welding
Original Posted By: javier cruz
Subject: Re: Pietenpol-List: Piet List: weldingIn a message dated 3/4/01 5:27:34 PM Eastern Standard Time, bed(at)mindspring.com writes:>is this for oxy acetylene welding or for normallizing tig welds or what??Henry Williams--- gluing up some ribs tonight ________________________________________________________________________________Date: Sun, 4 Mar 2001 19:57:04 -0800 (PST)
Subject: Re: Pietenpol-List: Piet List: weldingIn a message dated 3/4/01 5:27:34 PM Eastern Standard Time, bed(at)mindspring.com writes:>is this for oxy acetylene welding or for normallizing tig welds or what??Henry Williams--- gluing up some ribs tonight ________________________________________________________________________________Date: Sun, 4 Mar 2001 19:57:04 -0800 (PST)
> Pietenpol-List: WELDING/BRAZING
Original Posted By: Christian Bobka