Cold temperatures induce blade chipping?

[Twindog]

...




Anyway, here's another chart with numbers. A36 steel of course isn't used for making blades, save for maybe some homemade stuff, but it does illustrate that the transition temperature can be high enough for steel to be of (SOME) concern for certain demographics. It's plainly obvious that there is a dramatic decrease in ductility.

The chart appears to suggest that a knife blade will lose most of its ability to withstand impacts when it drops from room temperature to 32 degrees F. Hard for me to believe that.

 

[upnorth]

I have almost destroyed the edge of my Gransfors axe this winter. I was just chopping 5 inch thick pine and blade gain rolled and chipped.

I rolled the edge of an old Becker Brute a few years back. It was around -30 and the live trees were frozen like granite......I've always wondered why gun barrels don't burst\shatter when frozen outdoors all day ?

 

[The Mastiff]

The gun barrels are fairly tough steels like 4140, heat treated in the 40's and they aren't the pressure containing parts unless blocked, plugged, or stuffed with the wrong bullet. Another secret is the powder pressure goes down a good amount with very low temps. Depending on caliber, bullet, powder, etc., you may get up to 300 fps lower velocities in very cold temps. Different powder shapes, sizes and how much it's packed can all change things a bit.

I'd be more worried about it bursting ( the brass, primer, next the bolt parts and receiver) with bullets that have been sitting in my car here in North Carolina in the summer. Try shooting a bullet left in the fridge overnight compared ( not given too much time to heat back up of course) to one at 90 degrees temp ( mild summer day in Raleigh). You will notice the difference. I will no longer shoot bullets right out of the hot car ( 120 degrees or more). I've learned my lesson and it didn't take a burst barrel. There was primer extrusion and some flowing and one guy got a black eye from recoil.

 

[Jastab]

Fracture toughness of a steel is definitely decreased at cold temperatures. How much this affects chipping strength I don't really know.

The Titanic suffered significant steel fracturing, in very cold water. Samples of the hull plating have been tested and shown to have poor fracture toughness, and the cold water would have made that even worse.

The steel used on the titanic was 7x weaker than todays steel. I watched some crazy documentary on it a few days ago. I don't believe cold would do anything. Wouldn't cryo treatments royally mess it up if cold did matter?

 

[zeroed4x]

Wouldn't cryo treatments royally mess it up if cold did matter?

Cryo treatment helps to remove stress and improve wear. My gunsmith had my match competition rifle barrels cryo treated before he installed them on my completed rifles. It really works. It extends the barrel life for about an additional 1000 rounds.

 

[JustSomeGuy]

Cryo treating metal is a very controlled metal treatment process intended to produce an intended effect. It should be obvious to everyone that the cold conditions outdoors are very uncontrolled, so this is a red herring at best in this discussion.

ETA, also, we are talking about USING the knife at these temperatures. You aren't trying to cut things with a knife DURING cryo treating.

 

[me2]

Note this is an impact toughness issue, so if one is just cutting, it wont be a problem. The transition temperature is greatly influenced by alloying and carbon. The higher carbon steels can have transitions that start at just below room temperature. However, the drop is not as sharp, and in any case doesnt drop to zero. Alloys with nickel are better at lower temps, as are blades that are quenched after tempering. The transition applies to being used at the low temperature. Leaving your knife outside in Alaska and then warming back up wont embrittle it. Same for a liquid nitrogen bath. Well, that can, but not because of the ductile to brittle transition.

 

[Shotgun]

Metals can and do experience an increase in brittleness when exposed to prolonged cold temperatures.

I have almost destroyed the edge of my Gransfors axe this winter. I was just chopping 5 inch thick pine and blade gain rolled and chipped.

Cold does have an effect on steels. That's why you'll here guys saying that before they cut wood with their axe they'll stick the head in their armpit for a while to warm it up.

 

[outdooredge]

I rolled the edge of an old Becker Brute a few years back. It was around -30 and the live trees were frozen like granite......I've always wondered why gun barrels don't burst\shatter when frozen outdoors all day ?

When I chipped and rolled my Gransfors axe it was around -3 but it was morning and night temperature was around -16 so trees were still almost frozen.

 

[Concat]

The chart appears to suggest that a knife blade will lose most of its ability to withstand impacts when it drops from room temperature to 32 degrees F. Hard for me to believe that.

A36 is a cheap structural steel; it's not suitable for knives.

 

[Big Mike]

A YouTuber told me he likes the softer steel (HRC55-56) of Marttiini knives because they don't chip in cold weather as easily as harder blades. I told him I don't believe cold weather has an impact on blade performance, and edge geometry is more what he should be concerned about when it comes to chipping. So, can cold conditions (let's say well below zero) increase chipping?

Joe, the answer to you question is YES, cold conditions will make a knife blade more brittle.

The amount of change has a lot to do with how cold it gets, and how tough the steel is.


I would suggest using a tougher steel is a better solution to cold weather conditions the just using a knife with a lower hardness level.

But, in most conditions you're likely to be out using a knife in, the effect will be minimal.




Big Mike

 

[me2]

The chart appears to suggest that a knife blade will lose most of its ability to withstand impacts when it drops from room temperature to 32 degrees F. Hard for me to believe that.

Its difficult to describe how much tougher A36 is than vitually any cutlery steel heat treated as such. They are less tough at room temperature than A36 at below freezing. That chart is intended to show the difference between modern steel and Titanic steel. It also shows the ductile/brittle transition. I wouldnt recommend drawing any knife related conclusions from it. Even the Titanic steel is tougher than hardened cutlery steel.

 

[Frisky]

It does make sense to go with a tougher steel in cold temps, rather than a lower hardness. However, look at Roselli and some of the other arctic circle knife makers. I've seen hardnesses between HRC63 and HRC67 on some of their knives. They usually stay around 57-59. I've also read tests that claimed VG10 getting brittle at about any temp if hardened over HRC59.

Joe

 

[upnorth]

The gun barrels are fairly tough steels like 4140, heat treated in the 40's and they aren't the pressure containing parts unless blocked, plugged, or stuffed with the wrong bullet. Another secret is the powder pressure goes down a good amount with very low temps. Depending on caliber, bullet, powder, etc., you may get up to 300 fps lower velocities in very cold temps. Different powder shapes, sizes and how much it's packed can all change things a bit.

I'd be more worried about it bursting ( the brass, primer, next the bolt parts and receiver) with bullets that have been sitting in my car here in North Carolina in the summer. Try shooting a bullet left in the fridge overnight compared ( not given too much time to heat back up of course) to one at 90 degrees temp ( mild summer day in Raleigh). You will notice the difference. I will no longer shoot bullets right out of the hot car ( 120 degrees or more). I've learned my lesson and it didn't take a burst barrel. There was primer extrusion and some flowing and one guy got a black eye from recoil.

Very interesting. Thank you.

 

[upnorth]

When I chipped and rolled my Gransfors axe it was around -3 but it was morning and night temperature was around -16 so trees were still almost frozen.

Actually I was going off on a loosely related tangent. I believe that the O.P. meant chipping when a blade was exposed to extreme temps for an extended period. I did that but I didn't chop with my big blade as the frozen rock hard trees stopped that in my ptarmagan hunting romps. Thanks for the info on your Granfors axe. I have Granfors and Wetterlings. I surely do not want to mess up such fine tools. This looks like another reason to bring a saw. The natives up north always use chain saws and just bring an axe back up. I apologize for going off topic. No, I have never chipped a frozen knife blade. But extreme cold does ugly brittle things to many materials, indeed.

 

[bdmicarta]

This chart is pretty much what I thought I remembered. I am a structural engineer and I took a class in fracture mechanics in graduate school. We talked about this kind of thing but that was a long time ago and I might have forgotten a few details since then, but certainly you can find reduced toughness in common weather conditions. We also talked about the problems with the liberty ships splitting in the ocean but that issue was aggravated by welding of the plates. (welding and stress concentrations are other factors that can affect fracture toughness and fatigue life)

This chart is showing the impact toughness of the steel, not the tensile strength, and they aren't related. There may be some high strength knife steels with less impact toughness than even the titanic hull plating.

There is some question here about time- stick your knife in a glass of icewater and it can reach 0 degrees C in just a few minutes. That's all it takes to reduce its impact toughness, it doesn't have to sit there for a prolonged time.

 

[Wolf_HR]

I'm by no means an expert (but mech. eng. nevertheless), so I hope noone minds me butting in on this discussion... One thing I've seen mentioned is cryo treatment- FWIW, I do not think it's relevant for this discussion because I would venture a guess that cryo treatment is all about exposure of the metal to the huge temperature difference after the heat treatment, rather than to expose the steel to prolonged sub-zero temperature. In a nutshell, thew bigger the temp. difference the more rapidly steel will cool, allowing it to retain more carbides than it would if it was cooling more slowly (with lesser temperature difference). I believe the correct term is the quench (we all like to see it in movies when they dip the sword in cold water/oil/snow, &c)- and the bigger the temp differential (and Cf of the quenching medium), the more quickly the steel will cool, and hence more carbon and carbides will be retained in the steel...

And to answer a previous post- I do not believe carbon/less alloyed steels will be inherently less prone to chipping/brittleness at lower temperatures. My opinion is based on the fact that construction steels (low-alloy carbon steels) complying to standards (ranking them according to strength) have special formulations* when exposed to either too hot or too cold temperatures. I wouldn't trust the standards/norms of my country worth a damn, but I'm almost 100% sure they are rip-off of German DIN norms, so there might be a bit of deep understanding of the processes involved).

* from what I've gleaned in my hdbk, low temperature alloys have slightly lower carbon content, but also in the same proportion lower content of impurities (most notably, sulphur and phosphorus- latter of which is added to balance carbon in regards to machineability, if reputable sources are to be believed)

 

[Cynic2701]

The chart appears to suggest that a knife blade will lose most of its ability to withstand impacts when it drops from room temperature to 32 degrees F. Hard for me to believe that.

Just how often do you baton (or do other rough things) with a knife that is at 100 degrees Celsius?

 

[me2]

This chart is pretty much what I thought I remembered. I am a structural engineer and I took a class in fracture mechanics in graduate school. We talked about this kind of thing but that was a long time ago and I might have forgotten a few details since then, but certainly you can find reduced toughness in common weather conditions. We also talked about the problems with the liberty ships splitting in the ocean but that issue was aggravated by welding of the plates. (welding and stress concentrations are other factors that can affect fracture toughness and fatigue life)

This chart is showing the impact toughness of the steel, not the tensile strength, and they aren't related. There may be some high strength knife steels with less impact toughness than even the titanic hull plating.

There is some question here about time- stick your knife in a glass of icewater and it can reach 0 degrees C in just a few minutes. That's all it takes to reduce its impact toughness, it doesn't have to sit there for a prolonged time.

One thing to keep in mind is that the chart above is most likely made with a Charpy V notch test. Cutlery steel toughness is measured typically using the C notch or un-notched samples. A value of 100 J in a V notch sample is much tougher than 100 in a C or un-notched sample. This is still a SWAG, but the Titanic steel at 25 C in a C notch test would probably be close or slightly tougher than many modern cutlery steels with cutting tool appropriate heat treatments. FWIW, modern bridge girder plate used in VDOT work has to meet 15 ft-lbs. at -40 deg. F., just as a comparison.

 

[The Mastiff]

Very interesting. Thank you.

You're welcome upnorth. I grew up in the upper midwest, and have lived in places with very cold winters like Ohio, Michigan, Nebraska, as well as in the mountains in Colorado and in Europe in the Alps and parts of north central Germany ( before the reunion). I have stayed outside in the winter with nothing but a piece of canvas and a sleeping bag with no fires allowed for weeks at a time. In addition I was an armorer, have extensive weapon training and have done a lot of reloading so I know when something is showing signs of pressure being high. If the ammo is very hot to the touch don't shoot it until it cools off. Put it in the shade for a while before using if at all possible. If you are in Iraq in the summer that's not really possible but you do the best you can. Military ammo is tested in conditions like that and has a bit of leeway built in. Not so some older kinds of Surplus ammo if you are into old rifles. There is 7.62X54R ammo from Russia meant to be shot in MG's that is too hot for Mosin Nagants ( same caliber) as it is. Use it on too hot of a day and you are lucky if you ONLY lose the rifle. Always know what you are stuffing in your... Yeah. ok. I'll shut up.



Joe