Steel Chart draft 1

[gscreely]

I am working on some steel charts to put on my website. Those of you into this sort of thing take a look and see if you think I am way off on any of the steels. Also let me know if I missed any substantial steels.

Any list like this is fraught with creating strong opinions, so try to point out things that seem really far off. I also grouped several of the steels into families because the formulas are so similar. I am of the opinion differences in heat treatment causes more observable differences than minor alloying tweeks, therefore steels that are close go together on the chart. To give you a sense of my MO I considered putting 440C in the 154 CM group, but with the chrome being lower, the addition of more Mo, and a pinch of Vanadium I separated them. On the other hand I did not separate powered steels from their ingot counterparts because those differences are not substantial enough to recategorize the steel (at least in my opinion).

Charts like this are rough guides at best, but can be helpful to folks who don't know the general trade offs of the wide array of steel options.

 

[knarfeng]

You grouped CPM steels with melt steels having the same elemental composition. I don't agree that they should be in the same group. Based on my experience, I consider them different. In some cases, significantly different.

 

[me2]

Where did you get the information to rank the steels? There are some that are a bit wonky.

 

[NJBillK]

And the scale on the bottom is 0-100, but what is that a measurement of?
27 what, 58 what?

On top of that, if the ingot vs cpm difference isn't vast enough, why would companies invest (possibly) millions of dollars to come up with the process, and continue to make the upgraded versions and discontinue the ingot versions?
That last part can be proven with items like CPM Cruwear, that was back around 2014 and is off the top of my head. If you would like for me to look up more instances, I will do so.

 

[gscreely]

Where did you get the information to rank the steels? There are some that are a bit wonky.

Good question. Well as a starting point I looked at a number of existing charts, some put out by steel manufacturers and others by knife web sites. I have personal experience with many of these steels as a user, and several as a knife maker. I also looked at the alloying metals as guide for steel I had not had experience with and could not find compared to others.

There are a few in there I was not super confident about, hence the request for additional opinions here.

I realize you could ask 100 knife guys there opinion on a chart like this and get 100 different opinions. As comments progress I am looking for general consensus on ones I may have placed wrongly here.

Which ones are most wonky?

 

[gscreely]

And the scale on the bottom is 0-100, but what is that a measurement of?
27 what, 58 what?

On top of that, if the ingot vs cpm difference isn't vast enough, why would companies invest (possibly) millions of dollars to come up with the process, and continue to make the upgraded versions and discontinue the ingot versions?

The point of the scale was to try to establish a relationship between the steels, so I am thinking of it of a percentile type of figure. There is no doupt that conjecture is at play here.

You just think they discontinue the ingot versions, I assure you that they still smelt the standard versions of many of these steels. For instance, Crucible makes ingot 154 CM as well as CPM 154. I believe the primary purpose of the powdered steel was to allow for the creation of very high alloy steels like 20CV or S90V ect.. The powdered version of standard steels are incremental improvemnts to there ingot bretheran (just my opinion).

That last part can be proven with items like CPM Cruwear, that was back around 2014 and is off the top of my head. If you would like for me to look up more instances, I will do so.

What would CruWear prove? Just not sure what you mean here?

 

[gscreely]

You grouped CPM steels with melt steels having the same elemental composition. I don't agree that they should be in the same group. Based on my experience, I consider them different. In some cases, significantly different.

Here is an interesting take on that. I am looking at all these comments closely. It seems like the big difference is in toughness, I think I will break out cpm154, and cpm d2 into their own. I will however stick 440C in the 154cm club since it is all there grand daddys.

3rd generation PM steels marketed as clean and fine grain. The 'clean' is true, while 'fine grain' is relatively speaks. M390 grain is ~1-2microns in size, which is quite large comparing to carbon grain of 50-200nm. PM processes prevent carbides seggregation and other lattice maladies, especially critical for high alloy steels. Without it, there won't be any usable steels with excess 1% of hard alloy carbides.

A year ago, I would readily agree with how PM edge quickly lose its crazy sharp - after head bricking s30v, sg2, etc.. Now, it's no longer the case, my s30v will stays crazy sharp even after cutting cardboard. It's about knowing steel's properties + abrasives + edge geometry.

Regular D2 grain size can be as large as 50microns but average out around 15microns. I do believe SKD11/D2 grain is around 10microns. While CPM-D2 grain is consistent/uniform about 5microns, which make it a lot cleaner and possibly avoid large grain fracture that lead to large chip. However micro-chip is still part of PM life and extra bad for super thin edge. btw - I used to hate my D2 blade and not too fond of skd11 but now I like D2 almost as much as cpm-m4.

 

[me2]

Maxamet, HAP 40, D2, M4, and 10V near the top of the toughness chart. H1, 420HC, BD1, and AUS 8 lower in toughness than S110V. AEB-L, AUS 8, 420HC, & BD1 likely should all be higher in the standing for corrosion resistance. The higher alloy steels, but not stainless, should be higher than O1, basically move HAP 40 above O1. If your basing edge holding off just wear resistance, the low alloy and plain carbon steels should be below the simpler stainless like BD1, AEB-L, etc. This is all highly dependent on hear treatment, in each ranking, so summer standard competent heat treatment must be assumed.

 

[me2]

Here is an interesting take on that. I have not ruled out seperating them, so I looking at all these comments closely.

That quote appears to be comforting grain size and carbide size. They are not the same. If anyone has any information on high alloy steel grain size, I'd be very interested.

 

[Cobalt]

Here is a big problem with charts. Most are taken out of context. First, there is no way that you took the toughness of all those steels at the exact same Rc. Each steel should have the Rc in paranthesis so that people understand that the numbers may not be so easy. Some steels get real tough when you drop the Rc a bit, others seem not to change as much. too many factors there for a simple chart. I would provide mfg data for each steel with listed Rc. Even the method of testing can be different. Most steel industries used V-notch, while I think cpm used C-notch(I am not certain on this however). So even testing methods vary.

The edge retention chart suffers from the same issue. Edge geometry is a huge part of the performance of an edge. It isn't just the steel and it's HT. So when someone compares 100 knives from different manufacturers with completely different blade profiles and edge geometries, thickness and widths, it is nearly impossible to get accurate data. In fact even coatings make a difference. Unless every steel on that chart was a spyderco mule team, and every blade was Rc'd the same to remove the hardness out of the equation, there is no accuracy in the chart.

just my 2 cents

 

[gscreely]

Maxamet, HAP 40, D2, M4, and 10V near the top of the toughness chart. H1, 420HC, BD1, and AUS 8 lower in toughness than S110V. AEB-L, AUS 8, 420HC, & BD1 likely should all be higher in the standing for corrosion resistance. The higher alloy steels, but not stainless, should be higher than O1, basically move HAP 40 above O1. If your basing edge holding off just wear resistance, the low alloy and plain carbon steels should be below the simpler stainless like BD1, AEB-L, etc. This is all highly dependent on hear treatment, in each ranking, so summer standard competent heat treatment must be assumed.

Lots of good info here, I made some changes.

 

[jpm2]

Here's some data from crucible on their stuff. They have a few graphs comparing toughness, wear resistance, and corrosion resistance. Sometimes hardness is listed. You have to pick through it to get an idea of their rankings. According to their data and my own experience, there are a few in this thread that are way out of whack.

Take for instance this data sheet of D2.

 

[Cyrano]

"CTS Maxamelt" ???

Sounds good for queso; less so for blades.

 

[gscreely]

Here is a big problem with charts.

You are correct, lots of problems with such a chart. All the ones you mentioned would be possible pitfalls. I think the chart has to be taken for what it is, which is a starting point. It is not so say that all knives of this steel will perform to their steels potential in all cases. But this chart, (once it is dialed in), would be a great reference tool for the person who is trying to decide between a Spyderco PM2 in 52100 or S30V or S110V. The chart is meant to show a steels relative attributes.

Unless every steel on that chart was a spyderco mule team, and every blade was Rc'd the same to remove the hardness out of the equation, there is no accuracy in the chart.

Actually if the blades were RC'd at the same spot that would not be a fair or accurate test, because every steel have a sweet spot where it achieves the best balance of attributes. The hope for the chart is that it helps a person select a steel that performs strongly in the attributes that the blade will be used for. So if you work on a boat, don't get a knife made of 1095, ect... In fact when CPM compares their own steels they do so at different RC.

 

[Cobalt]

Actually if the blades were RC'd at the same spot that would not be a fair or accurate test, because every steel have a sweet spot where it achieves the best balance of attributes. The hope for the chart is that it helps a person select a steel that performs strongly in the attributes that the blade will be used for. So if you work on a boat, don't get a knife made of 1095, ect...

I was only speaking of edge retention. You are correct that having the same Rc for all tests would be unfair as all steels have optimal Rc. But for edge wear testing alone, the same Rc would be necessary. If we are to compare how a steel wears then you need to remove all factors that make a difference and Rc is a huge one.

Overall I agree that a basic chart is a good basic guideline.

 

[ATJ999]

The same Rc for edge retention might not be the best idea. If you put 440C and ZDP-189 at 58 Rc., it might not be the most accurate. Same with a lot of the steels, S90V vs 10V at 59Rc. The same could be said for toughness and corrosion resistance. There are too many variable for all three, IMHO

 

[The Mastiff]

There are puzzlers here. For example Maxamet. Not exactly tough as used when it's commonly as high as rc 67 or even higher with that carbide fraction. As you are probably already aware steels/alloys can vary greatly in these attributes due to the method of heat treat used to get to the hardness selected. High austenitizing or high tempers can change things as can cryo. These same things also affect corrosion resistance and a pretty substantial change is noted in steels. Some more so than others, like 154cm, for instance. The finish really affects corrosion resistance. Two knives with both at rc 61-62 can very greatly in performance when measuring abrasive wear resistance, toughness and corrosion resistance if just tempered differently.

BTW, H1 is pretty tough.

joe

 

[Fanglekai]

Charts are worthless without actual data. There aren't even any units of measurement. 0-100 what?

 

[mete]

Where's CPM3V ? I assume here that the best is considered 100 and others compared to that . As I've mentioned in other threads actual impact values should be taken as guides not absolutes.

the CPM process has been around since about 1970. Smaller carbides of the 'powder steels' have inherently better toughness.

 

[gscreely]

Ok, So it seemed like the toughness chart had the most issues. Here is the updated version. I dug into a lot of crucibles data sheets and moved things around, as well as adding a few of the suggested steels. In general it seems toughness is the most difficult attribute to pin down.

I also broke out the CPM steels because of the substantial variation in toughness specifically.

My questions: is maxamelt too high on the chart? Are 1095 and 5160 in the right spot (the most common steels seem to be the most difficult to get comparative data on).

How does the stainless order look?