Metal finishing Q&As since 1989
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Having trouble heating the flux bath
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Q. Currently I'm having trouble heating the flux bath. I am taking advantage of the heat from the zinc tank, but the steam pipe is often punctured when immersed in Flux solution (ZnCl2. NH4CL). Based on your experience, what method should I use to heat the flux to 60-70 °C?
The fluxing solution includes 2 salts ZnCl2 and NH4Cl. Excess hot air pipes from the zinc tunnel will be soaked in fluxing to make this solution up to 60-70 degrees Celsius. After a period of use, these pipes will be corroded by Fluxing and high temperatures from the hot air into the pipes.
The pipes used is the special stainless steel type UNS S31254 ( stainless steel grade 254 SMO) with Mo (molybdenum) content up to 6%
My goal is to heat Fluxing to 60-70 °C, above is how I do it. Can you advise me which option is more effective?
- SHANGHAI&SHANGHAI CITY/ CHINA
February 22, 2024
A. This is a common problem where the hot gas is inside a tube immersed in flux. The flux is very corrosive, especially where the metal of the pipe is at high temperature.
A better system is to use the zinc furnace exhaust gas t make hot water at about 90C, and then use the hot water to heat the flux with immersed pipe heat exchanger, often ptfe tubing exchanger.
If you must use hot gasses direct into tubes immersed in flux, then 316L can perform OK, but will still corrode.
Geoff Crowley
Crithwood Ltd.
Bathgate, Scotland, UK
A. Best solution will be use SS316L or SS316LTi pipe to circulate hot water from quenching tank in to flux tank.
Ilesh G VyasGunatit Builders
Manjalpur, Vadodara, Gujarat
Thanks a lot, I will try!!!
- Shanghai/Shanghai city
March 1, 2024
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