What, precisely, is "special mild steel"?


Aug 8, 2004
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Hello all,

The title is self-explanatory, I am trying to determine what, exactly, this term means, and how it relates to the steel used in construction of the Olympic-type vessels.

Many thanks to all who speculate on this matter.

Colin Montgomery
 

Doug Criner

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Dec 2, 2009
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Mild steel is just another name for ordinary carbon steel - it is iron alloyed with carbon, which adds strength. There are various grades, but "special" doesn't mean anything unless the "specialness" is specified. For example, garden-variety carbon steel pipe that you can buy at the hardware store is grade A53, and there is an ASTM standard for it. What prompts your question?

Google is your friend.
 
Aug 8, 2004
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Doug,

A photograph prompts my question. One of Olympic, I believe. It is showing her stern frame, and, prior to assembly, the rudder post. Stamped upon the rudder post is "special mild steel".
 

B-rad

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I too have ran into this. Usually it reads, “The stern frame is of special quality mild steel and is of hollow or dished section, constructed in two pieces, 63ft and 37ft 4in, in length respectively.” From what I gathered this 'special mild steel', is of Siemens-Martin.

“All these castings are of Siemens-Martin mild cast steel with the exception of the rudder stock, which is of forged ingot steel.” Marine Review Vol. 41, 1911

Siemens-Martin:

It had considerable advantages over the Bessemer technique. Bessemer's conversion took place in half an hour, and quality control was imperfect. The Siemens-Martin process took fourteen hours to complete, allowed extensive chemical analysis, and therefore permitted precise control of quality. Moreover, since it worked ion the principle of mixing solid malleable iron into a molten bath of pig iron to produce cast steel, it also permitted the addition of scrap, and hence the re-utilisation of old malleable iron rails and plates for conversion to steel. - The Development of the West of Scotland

Hope this helps also.
steel.jpg

steel.jpg
 
Aug 8, 2004
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Brad,

My thanks for that. So, it would seem, that the "special" designation really does imply superior quality or of a better process.

Unfortunately, I cannot discern anything in your photograph. I am using a tablet, so perhaps that created a problem with the resolution.

Thanks, Colin
 

B-rad

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Sorry. something is up with the photo. It's not being posted to size. the photo is information from Marine Steam Engines: 1899.
if you google search 'Siemens-Martin special steel' it'll pop up.
 

Doug Criner

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"Siemens-Martin" is the just the old name for the open-hearth furnace process for making steel. The name "Siemens-Martin" faded away, and it just became know as open-hearth. Open hearths were used for many decades, but were retired in favor of the basic oxygen furnace. Open hearths emit a nasty amount of air pollution.
 

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