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/
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!
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.
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
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. Hmmmm.
it's days like this that I miss some input from Gaston ; ) Thank you Larrin, for sharing your vast depth of steel knowledge again
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 .
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.
That is some skill right there. Working from a mirror you have to retrain your brain to process the visual input backwards.
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.
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 !
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)
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.
