What was 'K.M. Steel'?

Discussion in 'The War at Sea' started by Mike L, Jan 17, 2011.

  1. Mike L

    Mike L Very Senior Member

    In research into Mk1 LCTs I have come across references to 'KM' steel but can find no definition or specification for this material.
    Most of the steelwork is noted as (eg) 5lb or 10lb mild steel, which is the gauge or to be more specific the weight of steel plate per square foot.
    The references are on shipyard detail drawings and the 'KM' steel relates to certain parts of the superstructure. From the location of the details I suspect 'KM' steel is some sort of armour.
    I have asked various steel suppliers, manufacturers and even found a couple of steel 'historians' but nobody could find any further information on this material.
    Given the depth of knowledge of WW2Talk members I thought I would pose the question here. All suggestions gratefully received Ladies and Gentlemen!

    Mike
     
  2. von Poop

    von Poop Adaministrator Admin

    Speculating...

    K = Potassium
    M(n) = Manganese

    Some kind of Manganate (hardened) Steel?
     
  3. Rich Payne

    Rich Payne Rivet Counter Patron 1940 Obsessive

    Mike, I don't know about the 'K' but Manganese steel was frequently used for armouring. It's hard (try drilling it !) and non-magnetic. It was used for steel helmets etc.
     
  4. Mike L

    Mike L Very Senior Member

    Adam, Rich, many thanks for those ideas - seems to support my idea it could be a spec for armour. Seems strange that a few 'experts' I have spoken to didn't make the same link.
    I will try to post a couple of details from the drawings for illustration.

    M
     
  5. Mike L

    Mike L Very Senior Member

    Couple of illustrations from the drawings attached - hope they are legible.
    I can understand the 'manganate' or Manganese steel spec but where would the possible K for Potassium come into it? (Chemistry is not my strong point).
    I wondered if the K could relate to Kinetic?
     

    Attached Files:

  6. spidge

    spidge RAAF RESEARCHER

  7. kfz

    kfz Very Senior Member

  8. kfz

    kfz Very Senior Member

    Where LCT's made from Armour plate?

    I think it probably some sort of marine grade of mild steel.

    Completely guessing of course.

    Kev
     
  9. Mike L

    Mike L Very Senior Member

    Hmmm, all rather confusing!
    The Manganese Steel (12 - 15% Manganese, known as Hadfield grade) certainly seems to fit with the armour plate theory (many sources on Google) but I still can't get to the bottom of the Potassium bit.
    Googling Potassium Manganate seems to throw lots of medical/agricultural uses but no reference to steel or steel production.
    Kev, as for LCT construction the structural framework was generally mild steel angle/plate of various gauges and all rivetted construction. The KM steel is generally noted as being used on the outside surfaces of the superstructure and much of the outer skin of the tank hold - exactly where I would expect to see armour.
    Interesting to note that the LCTs I am studying were manufactured in what appears to be 5 sections and transported to the Middle East where they were assembled 'in theatre'. Most accounts I have read state 4 sections but I have some evidence that the whole upper superstructure formed the 5th section for transportation.
     
  10. phylo_roadking

    phylo_roadking Very Senior Member

  11. Mike L

    Mike L Very Senior Member

    Hi Phil, thanks for that, another strong possibility.
    I did wonder about 'marinising' the steel alloy but apparently the Manganese Steel has quite good performance in that environment due to the high surface strength.
    I will have to double check the drawings but as far as I can recall the internal surfaces of the tank hold etc are not KM steel, which I would expect if it were mainly a corrosion prevention measure. Could it possibly be that just the external plating was Manganese alloy AND Potassium Nitrate treated?
    Both interesting ideas for further investigation - I will have to go over all 11 drawings now to check EXACTLY where the KM steel was specified!
     
  12. phylo_roadking

    phylo_roadking Very Senior Member

    I have asked various steel suppliers, manufacturers and even found a couple of steel 'historians' but nobody could find any further information on this material.

    Both interesting ideas for further investigation - I will have to go over all 11 drawings now to check EXACTLY where the KM steel was specified!


    Mike, watch for an "EN" number, the actual steel grade ;)
     
  13. Rich Payne

    Rich Payne Rivet Counter Patron 1940 Obsessive

    The drawing refers to "K M Quality" which doen't suggest a composition to me so much as an abbreviation for a particular application.

    Older engineering terms like this highlight just how modern the internet is. I can't find any reference to KM in any of the older engineering books that I've picked up either but I'm not focussed on shipbuilding.

    Are these British built vessels by the way ?
     
  14. Mike L

    Mike L Very Senior Member

    Phil, Rich, Can't recall seeing any EN refs, but I will check again.
    Yes, British RN Mk1 LCTs built 1941, the ones I am interested in were Clyde built.
    Might take a while to go over all the drawings, they are large and I don't have a hard copy, will have to check all details on screen
     
  15. Mike L

    Mike L Very Senior Member

    OK, checked the drawings and it gets both clearer and muddier!:(
    KM steel is noted for top and outboard sides ONLY for tank hold (not the inner tank hold walls), but all after top deck and superstructure (wheelhouse) outer walls. Not clear if the after/lower part of the vessel (engine room, machinery, crew accom etc) is KM or MS. All KM is 15lb/sq foot and is noted variously as 'KM steel', 'KM quality' or 'KM plate'.
    Strangely the section below (only one of many shown) appears to have KM above waterline but MS below, same notes on all sections.
    Appears to me that the KM (armour) is provided for protection of the cargo and crew, unclear if machinery is protected. Changing from KM to MS below waterline would tend to indicate armour rather than corrosion resistance? These vessels were often described as 'expendable' and I doubt if long term corrosion was a major consideration at design stage.:mellow:
    Any thoughts Gents?
     

    Attached Files:

  16. phylo_roadking

    phylo_roadking Very Senior Member

    Found something! I googled and found that Liele were using it as a prefix for their stainles steel kitchen products....I thought that was a dead end....then I found THIS mention...

    Electromagnetic stainless steel(K-M material) l NIKKOSHI CO., LTD

    That started me looking...

    electromagnetic stainless steels, K-M35FL, K-M31 and K-M38 are listed in Table 1. K-M35FL, containing Pb, is a free-cutting steel

    Could it be as simple as that, its an alternative/proprietary name for a range of grades of easy-welded stainless steel?
     
  17. Mike L

    Mike L Very Senior Member

    I spoke to a very useful and helpful chap at UK steel (again - he remembered my call last year!) who has come up with another interesting idea. Apparently there is a process in steel alloying/forging known as 'killing', which reduces the gas content in the internal structure of steel if I undertand it correctly.
    His best guess is that 'KM' could be a 'killed' Manganese steel, possibly Hatfield Grade (12 - 15% Manganese). He also mentioned that Manganese steel was used in WW1 steel helmets (well remembered Rich!) and that it would be a type of armour plate in the 15lb/sq foot (approx 3/8inch) gauge mentioned on the shipyard drawings. He thought the Stainless Steel theory was unlikely due to the high Nickel/Chrome content of Stainless that would have been in short supply in wartime. Probably such supplies as were available would have been used in the aircraft or engine building industry rather than for ship plating. He also put me in touch with World Metal Index in Sheffield, where archives of steel specifications are held and a very helpful Lady there is looking through those for references. I should hear something by phone or email soon.
    Even better - if I can get hold of a couple of small samples of the Mild and KM steel he has offered to get them analysed free of charge as he has become interested in this enquiry! Not as easy as it sounds though - the only known sources of samples are underwater, and not in this country - but there is a chance I might get hold of some if a long term project comes to fruition.
    So it appears we might be getting somewhere!

    Mike
     
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  18. At Home Dad (Returning)

    At Home Dad (Returning) Well-Known Member

  19. Mike L

    Mike L Very Senior Member

    AHD, I too was surprised by what showed up in a Google search for KM steel, many company names appeared.
    Phil (Phylo Roadking) also came up with the K-M Stainless reference, see post#16. Thanks for the ref but for the reasons stated in post #17 I have all but discounted the use of Stainless in LCTs in 1940/41.
    The Lady at WMI (World Metal Index) has already sent me a few pdfs and links to search through (I only spoke to her this afternoon) and she is looking for references to KM spec in their archives and Hadfield records, so fingers crossed she might come up trumps.

    Mike
     

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