Why Cold Steel is Brittle

Discussion in 'General Knife Discussion' started by Larrin, Dec 24, 2018.

  1. Larrin

    Larrin KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jan 17, 2004
    An article for those of you using knives out in the cold weather. Steel has lower toughness at low temperatures. I describe why that is, which steel properties lead to superior low temperature toughness, and how heat treatment can help or hinder low temperature toughness. https://knifesteelnerds.com/2018/12/21/why-cold-steel-is-brittle/
  2. hugofeynman

    hugofeynman Gold Member Gold Member

    Jan 18, 2011
    That’s one of the reasons I like K600 steel (4% Nickel) in my hard use knives. And 4340 seems a good steel for a big chopper, also!
    Another great article, Larrin!
    stonproject and Larrin like this.
  3. 007Airman


    Dec 23, 2018
    Very informative
    Larrin likes this.
  4. LG&M


    Dec 19, 2005
    You will be hearing from Lynn.;)
  5. Mo2


    Apr 8, 2016
    It first appears the title is talking about "Cold steel brand. It would be idea to Edit title to say...

    Why "Cold" Steel is Brittle.

    In any case its an interesting topic. Thanks for the write up! and Happy holidays everyone.
    DocJD, FullMetalJackass and cbrstar like this.
  6. Larrin

    Larrin KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jan 17, 2004
    I knew confusion with Cold Steel was inevitable. I liked the short punchy title too much.
  7. John A. Larsen

    John A. Larsen

    Jan 15, 2001
    If you are ever in a harbor where large ocean going ships are looking on the bow and you will see painted lines and letters. That is a Plimsoll line that indicates how deeply can you safely load the ship depending on the ocean and time of year. The shallowest line is for "WNA" Winter North Atlantic, because of the effect that the cold water of the North Atlantic has on the strength of the ship's steel hull. John
  8. Wowbagger


    Sep 20, 2015
    That is freekin' fascinating ! I never realized.
    I even thought people were kiidding or exagerating about knives for winter use.
    Gosh I figured the ambient had to get well below zero F to make the slightest dif.
    GlockMonster30 and Larrin like this.
  9. dirc


    Jan 31, 2018
    it's days like this that I miss some input from Gaston ; )

    Thank you Larrin, for sharing your vast depth of steel knowledge again
  10. BigKurtHaze


    Aug 2, 2015
    I can't believe you guys chased him off! :D
    DocJD, sharp thoughts and ns2190 like this.
  11. mete


    Jun 10, 2003
    WWII made the wake up call ! Ships quickly built with less than ideal knowledge . The big numbers were the Liberty Ships .Reinforcement of the hulls was needed . I saw a photo of a ship that broke in two -- calm water , tied to a pier, 70F ! Much or the ships welded rather than riveted. I knew a fellow who 's LST broke [ main deck side to side ]in the middle of the Pacific. They welded up that one at sea ! In later years special tough steels were developed like HY 80 and HY 120 for subs .
    Mecha, hugofeynman and FortyTwoBlades like this.
  12. FortyTwoBlades

    FortyTwoBlades Baryonyx walkeri Dealer / Materials Provider

    Mar 8, 2008
    I've been told that during WW2 my great grandfather did welding on ships at Bath Ironworks. He wanted to enlist, but he was one of the only welders able to do good work in some of the cramped spaces assembly dictated, and they told him they needed him building ships more. Apparently in some of the tighter spots he had to weld over his shoulder with the aid of a mirror.
    Mecha, Gary W. Graley, Larrin and 3 others like this.
  13. Bill1170


    Dec 20, 2007
    That is some skill right there. Working from a mirror you have to retrain your brain to process the visual input backwards.
    FortyTwoBlades and Larrin like this.
  14. John A. Larsen

    John A. Larsen

    Jan 15, 2001
    My father was in the Merchant Marine prior to WWII and served as a Captain all thru the war. As mentioned above he saw a Liberty ship break in two during a storm during the Winter in the North Atlantic and no survivors. He drank his coffee so hot and he would be done and my Mother would still be blowing on hers. I asked him why he had it so hot and his answer was when you were on an open bridge of a Liberty ship during the Winter in the North Atlantic, it had to be hot and you had to drink it fast or it would soon be cold. When he died we found a Canadian issued Life Insurance policy which he had kept up. I wondered why and my Mother said he was sailing Land Lease to England prior to the USA entering the war after 7 Dec 1941, and could not get a US Insurance company to issue a policy. John
    PS The Canadian company paid up what he was owed.
  15. ns2190


    Nov 21, 2012
    Well, it's only Tuesday, but I'm comfortable in saying that's the best story I'll read this week!
    Pilsner, Larrin and Pomsbz like this.
  16. mete


    Jun 10, 2003
    I used to certify welders for the nuclear subs and was very strict. That's because during the certs everything was nice . During reburbishing it's a mad house . Welding under all conditions up side down etc .I figured if they can pass under calm conditions they might make a decent weld under duress !

    During the war my grandfather worked in a shipyard and he had to sign off on jobs before they went out to sea. On one job he refused. So his boss signed for him. The ship sailed and the repairs collapsed when the ship reached open sea ! :D:D:D
    Larrin likes this.
  17. dirc


    Jan 31, 2018
    excellent story mete, that always happens when mgmt is allowed to override subject matter experts, it happens in my line of work to this day ; )

    back to steel... Larrin's excellent write up reminds me why construction steel is often 0.2% carbon and has nickel :)
    (and also why good structural steel usually specifies less than 0.007% sulphur, in some cases even lower, which is amazingly precise composition control)
    Last edited: Dec 25, 2018
  18. Mecha

    Mecha Titanium Bladesmith Knifemaker / Craftsman / Service Provider

    Dec 27, 2013
    Never heard of the WNA line being concerned with steel getting brittle in the cold. I thought Plimsoll lines were are only concerned with water density and how much buoyancy it gives a ship, for loading purposes and sea conditions, not because the hull will get brittle in the cold. In the North Atlantic winter I'm sure the water is usually warmer than the air, at any rate.
  19. Pilsner

    Pilsner Platinum Member Platinum Member

    Oct 28, 2017
    Agreed. Thanks, John, for sharing that.
  20. deltaboy


    Jul 6, 2014
    Great story of ships, steel and a Honest Insurance company!

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