SS parts that turn green in an furnace Braze cycle??
SS parts that turn green in an furnace Braze cycle??
(OP)
We have had a few furnace over the years that haved turned green after the furnace braze cycle. The heat treat facility thinks it is moisture but I am not sure. He says he pulls a hard vacuum and has good atmosphere. he does a furnace clean prior to our runs. He is mainly a Heat treater, not a brazer. Can it be the alloys??? The alloy is 18-FM Chrome core. In the brazement the crabon steel and nickel filler are "clean" but the 400 ss is tinted. Any suggestions?





RE: SS parts that turn green in an furnace Braze cycle??
18-FM Chrome???
Do you have a standard designation for the alloy?
RE: SS parts that turn green in an furnace Braze cycle??
0.015 C, 0.40 Mn, 0.90 Si, 0.02 P, 0.30 S, 17.5 Cr, 0.2 Ni, 1.75 Mo, 0.25 Cb, Bal. Fe
Chrome Core 18-FM stainless is a soft magnetic ferritic material designed for operation in more corrosive environments than tolerated by 18 percent Cr-Fe Type 430 stainless. This new alloy has corrosion resistance superior to that of Type 430 FR stainless with generally similar magnetic properties.
RE: SS parts that turn green in an furnace Braze cycle??
RE: SS parts that turn green in an furnace Braze cycle??
RE: SS parts that turn green in an furnace Braze cycle??
If the corrosion is water-soluble, this will ~verify.
If not, the flux may be extracting Cr at high temperature, but then the corrosion decomposes to Cr2O3 on cooling with trace amounts of oxygen present.
RE: SS parts that turn green in an furnace Braze cycle??
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Rust never sleeps
Neither should your protection
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RE: SS parts that turn green in an furnace Braze cycle??
The vacuum furnace setup can be made to alarm-out when a cleanup cycle hasn't been performed in "X" number of runs. Our cleanup cycle goes rather high (around 2500 degrees F) at 300 microns, but it does an excellent job of blasting scale and buildup out of the furnace.
Here we use continuous brazing furnaces under dissociated ammonia atmosphere. I'm normally only getting green oxide layers on the parts or belt when someone has a genius idea to place a fan near the exit end of the furnace and blows air down through (despite the doors and angel hair).
RE: SS parts that turn green in an furnace Braze cycle??
(zzz, we have an overhead door at one end of our bright anneal furnace. Some days I just want to kill someone for that)
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm