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lvzhiyong
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Join Date: Dec 2006
Posts: 29
Good Answers: 1

Brazing Pinhole Reasons

04/09/2012 9:39 PM

Hello everyone, we have a product that brazed by tunnel furnace. The base metal is brass and stainless steel. The filler metal is brazing pastes: Ag55%Cu Zn sn.Recently, we find some product with pinhole in the brazing joint. The pinhole is bigger and only in the brazing surface of fillet but no in the brazing clearance. You could find it in the photoes. Could you help us analysis the reasons and thanks in advances.
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Pathfinder Tags: brazing pinhole
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dvmdsc
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Join Date: Mar 2010
Location: In the pool because it is too hot.
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#1

Re: Brazing pinhole reasons

04/09/2012 11:12 PM

Can you re- attach the photos please?

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lvzhiyong
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Join Date: Dec 2006
Posts: 29
Good Answers: 1
#2

Re: Brazing pinhole reasons

04/10/2012 1:07 AM

Sorry for forgotting upload the photo.
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welderman
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Hobbies - DIY Welding - New Member

Join Date: Sep 2007
Posts: 1601
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#3

Re: Brazing Pinhole Reasons

04/11/2012 9:41 AM

It looks like a gas blow hole. I suspect that you are heating the joint too quickly and a component of the flux is not volatilizing before the braze metal has melted.
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generalee82
Member

Join Date: Jan 2012
Posts: 5
#4

Re: Brazing Pinhole Reasons

04/12/2012 7:20 AM

Try a copper braze ring? Slow the belt speed down? What type of gasses are you using in the furnace?
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lvzhiyong
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Posts: 29
Good Answers: 1
#5
In reply to #4

Re: Brazing Pinhole Reasons

04/12/2012 9:04 PM

Could we braze brass with copper? Maybe we should slow the belt speed down. Our protect gas is mixture of 30% H2 and 70% N2.
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welderman
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#6
In reply to #5

Re: Brazing Pinhole Reasons

04/12/2012 11:29 PM

Since you are using a reducing atmosphere, you may be able to use a solid preform (washer) instead of the paste. It sounds as though you are using AWS-BAg-7 (56Ag-22Cu-17Zn-5Sn) 1145-1205 degrees f as the braze metal and that should be available in washer form. The advantage of a solid preform is that you won't need to drive off the paste binder.
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lvzhiyong
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Join Date: Dec 2006
Posts: 29
Good Answers: 1
#7
In reply to #6

Re: Brazing Pinhole Reasons

04/13/2012 12:56 AM

Our filler material is Ag103(EN1044, 55Ag-21Cu-20Zn-2Sn) 1166-1220 defrees f . It is available in washer form but we have use paster for many years. There is seldom have such problems before. Do you think this reasons is filler metal or brazing process.
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welderman
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#8
In reply to #7

Re: Brazing Pinhole Reasons

04/13/2012 8:34 AM

It could be several things including contamination on your piece parts, but my first guess is that some liquid part of your paste is not completely vaporized before the braze metal melts, and the vaporizing paste forces its way through the liquid braze leaving a blow hole. If you replace the paste with a wire preform of braze metal and the problem goes away, you will have solved the problem and lowered cost.
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durtieduck
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Join Date: Jan 2011
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#9

Re: Brazing Pinhole Reasons

04/25/2012 5:22 PM

sorry for the late post. does the metal have the same properties? the flux?
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durtieduck (1); dvmdsc (1); generalee82 (1); lvzhiyong (3); welderman (3)

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