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Coating Tube with Fusible Alloy

Coating Tube with Fusible Alloy

Coating Tube with Fusible Alloy

(OP)
I need to coat steel tubing with a low-melt temp (220F to 230F) non-eutectic alloy. Does anyone know a vendor that does or can do this?   

RE: Coating Tube with Fusible Alloy

Non-eutectic alloy of what? 220F-230F is going to restrict you to exotics like 45Bi-23Pb-19In-5Cd-8Sn. Which melts at 117F.

Infact my GEM lists the next highest melting point at 281F 58Bi-42Sn. Which might be a eutectic alloy.

good luck.

you might be able to search MatWeb to figure what you are going to coat with.

RE: Coating Tube with Fusible Alloy

(OP)
It's a two part question. First I need to know if a non-eutectic alloy exists (or can exist) that melts in the range listed and then a vendor experienced with such a material.

RE: Coating Tube with Fusible Alloy

NickE,
Bi-Sn has a eutectic at 46 at% Bi (~60 wt%) composition & 138.5C; the liquidus at 58 wt% Bi is ~10F higher.  
Probably all common solder alloy systems have eutectics. 45Bi-23Pb-19In-5Cd-8Sn maybe melt at a quinternary eutectic, but my books don't go that far!

cbert,
Does "non-eutectic alloy" mean a composition a bit away from the eutectic in order to give a 10F melting range?  I.e., either a hypo- or hypereutectic alloy with a liquidus at 230F & a solidus (or eutectic) at 220F. Preferable to say 'off-eutectic.'
Giving a melting range makes it redundant to say 'non-eutectic;' a eutectic defines a single temperature.
[If looking for a alloy system w/o any eutectic (like Cu-Ni), probably SOL.]

Search for "solder melting range" & low-temperature “fusible alloys,” then look at temperatures. e.g., Alloy 16 in the 'Table of Specialty Alloys and Solders,' of composition 44.7Bi-22.6Pb-16.1In-11.3Sn-5Cd, has a liquidus at 126F & solidus at 119F.
http://www.indium.com/products/physicalproperties.php

For application, first Ni-plate the steel tube to improve solderability (not Cu, it may build up in the liquid metal & change the melting range). Then apply by soldering (for a small quantity) or hot-dip (large quantity) technique. Maybe necessary to have a surface layer of flux atop the liquid metal bath owing to easy oxidizability of In. Can also find a non-In-containing alloy.

Good luck,
Ken



RE: Coating Tube with Fusible Alloy

Oops, looked in a book with temperatures in C and forgot to switch my mind back to F.

Maybe try Alloy 52, 54.5Bi-39.5Pb-6 Sn, melting range 216-226 F.

RE: Coating Tube with Fusible Alloy

kenvlach- I was trying to ge the poster to provide more information. The alloy's I mentioned were just pulled out of the Guide to Engineered Materials that sits on my desk. I didn't realize this was a solder alloy question, but then again that makes sense.

To do an alloy designe like this wouldnt it be effective to search for an alloy system that has a eutectic around the min melting point needed. Then shift the composition either way about the eutectic composition to increase the liquidus to the max melting temp required?

RE: Coating Tube with Fusible Alloy

cbert,
can you tell us more about the non-eutectic requirement?

NickE,
I don't think there's necessarily a difference between solder alloys & low temp fusible alloys except for application.  Solders are tailored for wettability and some for electronic applications.

Nice description of 'off-eutectic'
Ken

RE: Coating Tube with Fusible Alloy

(OP)
Thanks to all of you for your detailed replies. I've received more info on the requirement from our customer. Heavy metals cannot be a part of the composition. I had previously said that the material must "melt" between 220F and 230F. A better description of what's truely needed is a metal that will weaken in the temperature range so that it fails catostrophically thus releasing pressurized gas. I've got a 10 foot hollow steel tube, 1/8" to 1/4" in diameter that's pressurized to about 100 psi. I need to release the gas charge in the event of a fire. I was envisioning small holes, approx. .020 in. diameter, drilled every 6 inches. One idea was to coat the tube with a low melt-temp material which would cover the .020 holes. Another idea was to have small "plugs" spaced every 6 inches. Any ideas?   

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