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Welding/brazing pin holes

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QUESTION: hi ernie

hi i use a silver brazing electrode ( TE 61 T 56% silver )and flux paste and lpg+oxygen gas torch brazing . i braze ss303 sheet part with ss303 solid base .  when i braze i find some pin  holes in my brazing . please suggest !

Regards

JP Singh.

ANSWER: The most common cause of pinholes in solder is insufficient cleaning beforehand.
Clean all your parts with a fine abrasive paper before soldering.

Another thing to watch out for is overheating your flux.
If the flux gets too hot it can often cause flow problems.

---------- FOLLOW-UP ----------

QUESTION: hi ernie

well i have ultrasonic cleaning machine . and i wash all the parts in that prior to brazing . so cleaning is not my problem . the flux is over heated sorry i dint get this the melting temp for flux is 400-500'c and of filler  is 650"c so we have to heat the thing upto 650 and the operating time is 12 seconds for my operation , my brazing length is 25-30 mm and sheet thicknes is 1.2 mm and filler is 1.0 mm dia .

plz suggest !

ANSWER: Still sounds like you are getting it too hot.
Is this furnace brazing?
Can you control the atmosphere in the furnace?

---------- FOLLOW-UP ----------

QUESTION: sorry i it is not furnace brazing , its fuel oxy torch brazing and there no temp sensors when the flux melts becums white puffy and part becomes red hot i apply the brazing rod ( silver )
i also have induction brazing there also i am gettintg the same problem
the joint has 0.005or less " fit tolerance it is u shape joint .

plz suggest !

Answer
If you are torch brazing you have to be very careful with your gas balance.
You need to run a slightly carburizing flame.
The carbon feather should be twice as long as the inner cone.
This reduces the oxygen in the flame and therefore reduces the oxidation of the metals when hot.

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Ernie Leimkuhler

Expertise

Questions about Oxy-Acetylene welding/cutting, MIG, TIG, Flux-core, Stick welding, brazing and soldering, bike frames, air frames, motorcycle frames, structural welding. Also questions about Welding Certifications and Inspections. All questions about fabrication of metals (stainless steel, steel , aluminum, brass, bronze, copper). Basic questions about underwater welding. TIG is my strongest subject.

Experience

Extensive background in most welding fields. 18 years fabrication of metal theatre scenery, 16 years structural steel, 2 years pipe welding, 9 years as a Welding Instructor at South Seattle Community College, and 5.5 years as a Welding Instructor at the Divers Institute of Technology. 16 years Industrial Welding Consultant for fabrication shops in the greater Seattle Area. 11 years Architectural Metal Fabrication. 8 years in Film/TV; SPFX/construction/set-deco/props/. 33 years Blacksmithing and Knifemaking. Currently a Field Welding Inspector for Otto Rosenau and Associates.

Organizations
American Welding Society - Certified Welding Inspector Washington Assoc of Building Officials (WABO) - Special Inspector - Structural and Reinforcing Steel.

Publications
Do a search on google groups for "Ernie Leimkuhler" in the rec.crafts.metalworking and sci.engr.joining.welding groups. http://www.stagesmith.com/ http://www.metalwebnews.com/ Blacksmith's Gazzette - Anvil Making

Education/Credentials
BA Theatre Technology - Purdue University.

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