Low Temp Structural Steels

[dakers]

Hello,

I am working on a project and I am having difficulty finding structural steel to be used on the job. The final location for the heater is in Siberia and the customer has asked that we use low temp carbon steel and that all steel be rated for -56degreesF. Currently we are purchasing structural shapes of A572 GR50 and having them heat treated and some of the steel is still failing our Charpy Impact Test requirements. We cannot afford to keep purchasing material and simply hoping that it passes. I have found other grades such as A203, A537, A533 that would seem to work fine but I cannot find a steel distributor in the U.S. that has structural shapes of these grades. I am currently looking into A588 as I was told it is very similar to A572 but has a better history of passing impact test and is readily available.

Currently we are purchasing A572, sending it to be heat treated, and sending a sample of the heat treated material to a test facility to be impact tested. For example we call out 10" x 25# channel to be tested at -56F with three test specimens to meet an average of 15ft-lbs, with no one test below 10 ft-lbs, and no two tests below the average. The 10" channel failed to meet those requirements but 6" x 8.2# channel of the same material passed. According to our steel supplier, once the steel has been heat treated we have purchased it, pass or fail. I need a grade of steel that is available in structural shapes and will consistently pass these requirements. If anyone could please offer any insight or alternative material it would be greatly appreciated. Thank you! -Dakers

 

[RobertHale]

In regards to that third requirement, are you saying that no two tests are below the 15 lb-ft limit or the average of the three tests?

 

[dakers]

RobertHale - The average of all three tests needs to be above 15lb-ft but two of them cannot be below that.

For example, 20, 14, 14 would give us an average of 16lb-ft which would pass but since there were two 14 values, we would fail.

17, 17, 14 would give us the same average of 16lb-ft with only one value below the requirement so we would pass.

I hope this isn't too confusing.

-Dakers

 

[TLHS]

I'd try calling around Canadian suppliers looking for 350WT or 300WT shapes (The standard that defines these is CSA-G40.21). The T indicates that it's impact tested to a given temperature depending on the category.

You'd be looking for Category 4, which is impact tested at -50F with 20ftlb. Plate is reasonably easy to find, shapes might be possible but I can't say I've bought them. Even for exterior structures in places that go down to the temperatures you're talking about we'd generally only bother with impact tested steel on items that would see significant impact, fatigue or lifting forces high in their stress range. Everything else would be normal W grade.

BC Ministry of Transport seems to use 300AT/350AT for critical steel shapes, so take a look at that as well. I don't know what the A grades are, off the top of my head and don't have anything to look it up in with me at the moment.

It'll still be an adventure, but at least they might know how to deal with you. Most of the steel you get out of Canada will really be US steel that isdual classified to Canadian standards.

Have you tried Russian suppliers? Basically, Canada and Russia are the two most likely countries to be able to give you steel for this use, because they're two of the only countries that would need to use it.

 

[dakers]

TLHS - Contacting Russian suppliers was an idea of mine but seeing as how the job has fallen behind due to the original order of A572 not performing as well as we had thought it would, we cannot afford to wait for steel to be imported from Russia. The Canadian grade sounds like a good idea with a much shorter lead time so I think I will spend the rest of the day exploring that option. Thank you! -Dakers

 

[TLHS]

I was going to scan in the pages from the steel handbook about Canadian steel grades, but a quick google search showed that someone already had.

http://files.engineering.com/downlo...4e40-90fc-eb6a0884c014&file=steel_grades.pdf.

 

[TLHS]

Skimmed a couple of places. Nucor-Yamato looks like they'll roll WT grades as shapes if you're looking to go straight from a mill.

 

[concretemasonry]

Going to a "300" series of steel, might be an option.

Back in the dark ages (1960's), I worked in the aerospace industry (rocket engines and test facilities) and 316 was our normal alloy for structural shapes (columns, base plates, angles, channels, tees) and even for grating and stair treads. The cryogenic piping, valves and tanks (LH, LOX and even FLOX) was eventually supported by additions to the main structure that was originally built with cryogenics in mind.

It was designing, modifying and building on the go (rough, cowboy-style). Some jobs were 1 or 2 two weeks form field measurements and observations to start of starting site construction. (new rocket engines were in a rapid state of change almost monthly) Somehow out purchasing department was able to source out most structural shapes and get quick delivery. - A very fun and valuable experience.

Going to 304 or 316 might be cost-prohibitive, but it can be done be done if you can go outside of the typical channels for specifying and purchasing.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[dakers]

Hi all, just wanted to follow up and share our results. We had A588 and A709 structural shapes tested at -56F.

The A709 was untreated as their metallurgist said heat treating this particular grade would not help our cause but in the end it failed to meet our requirements of 15ft-lbs.

The A588 was normalized at 1700F for approximately 20 minutes before the charpy testing at -56F. These samples performed excellently showing averages of 45ft-lbs up to 142ft-lbs on some of the heavier shapes.

Again, just wanted to share our results in case anyone comes across something like this in the future. Thank you again for all your help and suggestions!

-Dakers

 

[Archie264]

Thanks for sharing the results.