Duplex steel

[hoppercar]

There was a story in the july/august 2012 issue of live steam, about using a type of stainless steel for boiler construction called duplex steel. Although this article is centered in austrailia, was wondering if anyone here in the u.s. Has had any experience with it ?...

[Asteamhead]

Hello hoppercar,
Don't worry about!
The name "Duplex Steel" was posted by the manufacturer (from Sandvik Sweden) to promote it's special sort of stainless steel with lower content of nikle (that's less expensive!). In Newsealand this steel had been used for a small locomotive boiler and had bee accepted by the boiler inspector. Pretty good resistance regarding corrosion by cloride - ions had turned out to be slightly better compared to standard qualities. Welding qualities were fine, too. Most important were the lower costs, yet.
For us modelers still austenite steels like 1.4571 (Europe) or equivilant 316Ti (US) are still fine and easy to get in all dimensions!

Asteamhead

[Harlock]

Hi Hoppercar,

I wrote that article.

Since that time it's become wildly popular in Australia, with many engines completed to the AMBSC Part 4 specifications regarding the use of 2205 duplex steel. No problems have come up with the material or the design since then, it's been a total success. No one's yet built or imported one to the US. I would like to do so to replace my current marine boiler on the MEG at some point. It's just a matter of being able to afford a new boiler. It's not any more expensive than a conventional boiler, although if it is built overseas there is a shipping expense involved. Any 2205 certified welder here can put one together as well. The material can be ordered from Sandvik USA as a kit of laser cut parts. If the main tube is not available in a standard size, it can be rolled and welded together as was my friend John's boiler for his B-Class featured in the article. (the very first duplex boiler.)

AMBSC boiler codes may be ordered here: http://www.smex.net.au/Store/Store_AALS-Codes.php

[William234]

Hi, hopper car,
I wrote this because I also haven't any idea about the actual news comes from us but one of my friends also tell me the exact story. so I decided to ask him and tell you further news and telling him your concern. maybe it would help you an others in the future. and if I'm not wrong so it may also concern with the tig welder but I m not sure about this. if anybody have any idea about that so tell me because I want to know that it impacts the welders on not.

[Berkman]

I thought duplex 2205 was much more expensive than traditional steel w/copper flues.

What about the weight issue with it. I remember reading that boilers built with 2205 are built with thinner material due to its reduced heat transfer. but this would create a lower amount of weight on the drivers.

[Harlock]

I thought duplex 2205 was much more expensive than traditional steel w/copper flues.

What about the weight issue with it. I remember reading that boilers built with 2205 are built with thinner material due to its reduced heat transfer. but this would create a lower amount of weight on the drivers.

If you get it as a laser cut kit, weld prep time is greatly reduced, and in Australia and New Zealand at least, they've found it's about a wash to get a new build boiler with either material at this point. I got a quote for one that was competitive minus shipping as it was to be built in Australia at the time. I've identified a few 2205 capable shops here, the material is very popular in dairy plumbing.

2205 is not built thinner due to reduced heat transfer, it is thinner because the material is many many times stronger than mild steel. Any small difference in thermal transfer is way more than wiped out by the thinner firebox and tube walls, and the resulting increase in fire grate area that comes from both the firebox wall and the outer wall of the boiler being thinner. They fire so well that you need a much smaller fire for the same given amount of power, a little spot fire most of the time. Since there is no internal corrosion, it always fires like a 'like new' boiler. This is first-hand experience with my firing of John Heald's boilers on the Darjeeling B-Class locomotive and his "Tamar II" locomotive for many days while traveling around with them in New Zealand. As an experiment, we stopped feeding the fire towards the end of the day and continued to run the Tamar II for another 40 minutes before it really started to die. Next time I intend to make a time lapse video with a stopwatch in the image. Firing up, if you give it the same amount of fire as a mild steel boiler, it will come to pressure in about half the time. That pretty much says everything about firing capability.

Regarding welding, a duplex boiler does need to be TIG welded by someone familiar with duplex 2205 in a controlled environment. It is not a boiler you can weld at home. Temperature control is critical to preventing a phase change embrittlement during welding.

The weight issue is an issue, a typical duplex boiler will weigh about 2/3rds that of a standard steel boiler. To make up for it, you need to add weight elsewhere. Usually not too difficult with most locos. John tends to overbuild his engines with heavy plate frame and heavy wall steel for tanks so it's not a problem for him. I don't see it as any kind of showstopper at all, especially with a new build engine where you can take that into account.

Cheers,

-Mike

[Marty_Knox]

After meeting Dave Giles, John Heald, and Paul Newton at Train Mountain in 2012,I investigated building Duplex 2205 steel boilers. Sandvik quoted over $2600 for a kit of parts for an Allen Ten-Wheeler boiler. That works out to about $20 a pound. Granted, if I were a regular customer the price would probably be less, but that was the quote. I estimated my cost of qualifying to weld Duplex 2205 to be around $9000, with another $6000 to get a second weldor qualified. I made the business decision not to build Duplex steel boilers. Since then I have had a total of 4 people ask about them.