Tool Steel Reference Graphs

[Larrin]

As far as the chart goes, it doesn't seem to correlate very well with my personal experience, either. 440C is as wear resistant as D-2? C'mon now, let's deal with reality in the knife world. D-2 is twice as wear resistant as O-1? Not for me, it isn't. The toughness part seems to trend correctly, but I haven't found the differences to be as great between some steels as the chart implies.

Wayne Goddard says that 440C, D2, and 154CM perform about the same in his rope cutting tests at the same hardness. However, 440C is usually around 58 Rc while D2 is usually at 60, hence the wear resistance is normally going to be higher for D2. D2 has a high percentage of chromium and other carbides, so I don't doubt that the wear resistance is considerably higher than O1.

 

[flatgrinder]

The only gripes I have with your graph are that A2 is tougher than O1, even on Crucible's charts. O1 is 30 ft. lbs. at 60 Rc and A2 is 41 at 60 Rc, and the second is you didn't list any hardnesses. It can be a little difficult to see what hardness they're saying it is at on their charts. My guess is most of them are 58-61 like it says (edit: like it says on Crucible's charts, not yours), but the CPM-M4 and M2 are probably closer to 63 Rc, and the 9V at 53-55 Rc.

A2 isn't tougher than O1. Here's some info:

http://www.timken.com/products/spec..._Files/air_melt/ColdWorkToolSteels/TLS O1.pdf

O1 is tougher, I chipped an A2 blade when hacking on redwood. The O1 blade was fine.

 

[flatgrinder]

Wayne Goddard says that 440C, D2, and 154CM perform about the same in his rope cutting tests at the same hardness. However, 440C is usually around 58 Rc while D2 is usually at 60, hence the wear resistance is normally going to be higher for D2. D2 has a high percentage of chromium and other carbides, so I don't doubt that the wear resistance is considerably higher than O1.

Agreed. 440C actually isn't as bad as some people say it is.

As a wise man once said: "It's all in the heat-treat."

 

[Larrin]

A2 isn't tougher than O1. Here's some info:

http://www.timken.com/products/spec..._Files/air_melt/ColdWorkToolSteels/TLS O1.pdf

O1 is tougher, I chipped an A2 blade when hacking on redwood. The O1 blade was fine.

This is a Crucible graph, and the Crucible graphs show A2 as tougher than O1, and I didn't just make up those Charpy-C numbers. Even though Timken's comparison graphs show the toughness as being higher for O1, if you look at the tempering graphs on the data sheets for O1 and A2 on Timken's site (you've obviously already seen the O1 data sheet) they show the Unnotched Izod value according to hardness, and A2 is considerably better than O1, about 80 vs. 50 ft. lbs., both at 60 Rc. Timken seems to be contradicting itself. I've found that the Timken comparison graphs are especially unreliable, they almost seem to make it however they want to.

Edit: As always, real world toughness might not correlate with the types of tests done by steel companies, but all of their testing I've ever seen shows A2 having higher toughness than O1, I still can't figure out why Timken is showing the toughness of O1 being better when it doesn't even make sense looking at the rest of their data.

 

[Cliff Stamp]

Looking at the numbers, though, it is hard to imagine S30V having any problems with toughness.

I really don't see what you are looking at, S30V has no resemblance to the composition of a tough steel.

It has about the maximum amount of molybdenum before it starts to form molybdenum carbides, for added toughness.

Molybdenum doesn't have a specific carbide type, it however will contribute to both the vanadium and chromium rich carbides this is why it isn't listed in the primary carbide fraction of the s30v pdf file from crucible. Wilson discussed the dissolution of the molybdenum carbides with Crucible in regards to his higher temperature soaking.

It has relatively low carbide volume, which equals higher toughness.

Compared to what and of what type? The carbide fraction is fairly standard for a high alloy stainless which are not known for toughness.

It has the minimum of chromium, chromium reduces toughness as the percentage gets higher. It has the minimum of carbon (it's still very high because of the vanadium carbides it has to form). It has some nitrogen added, which generally increases toughness.

You really need to have some internal numbers to make these arguements such as the carbon/chromum fraction in austenite, the size of the primary carbides (and the type of the chromium carbides) and the amount of carbide precipitates during quench (different for still vs moving air vs oil) and temper.

And of course, it is made with the powder metallurgy process which makes the carbides uniform in shape and distribution, and much smaller than conventionally cast, and reduces the grain size as well.

Yes, however it isn't like you can CPM D2 and have it tougher than conventional A2. Where are the numbers supporting the extent that this process makes to toughness? How tough is RWL34 vs ATS-34?

Warren Osbourne, in his searches for a "chopper" steel, says that S30V was the best stainless that he used, but still didn't have the toughness that he could get out of a tool steel (which is only to be expected). By the way, his favorite is CPM-M4.

His favorite tough tool steel is M4? M4 is a high wear HSS used over M2 when you need wear resistance and not toughness.

I'd almost think that someone has made it "cool" to say that S30V has chipping problems, and that everyone is a bunch of hypochondriacs, or maybe heat treatment and edge geometry is somehow poor accross the board whenever the maker uses S30V.

Is it really more believable that there is some huge conspiracy than there could be a problem with a high wear steel in regards to toughness. Do some searching, the threads on S30V turn up in scads. You can find problems where individuals have bought several knives and have seen problems in 60% of them and multiple knives from different manufacturers all having problems, blades being returned and getting replaced and those having problems.
Pictures have been posted as well and the damage is large and visible.

I have seen solid performance from S30V in regards to slicing aggression edge retention and blades which are as durable as high alloy stainless in general. I have also seen several blades which would not sharpen, and others which both dented and chipped easily as well broke easily under light impact. Again, do some searches on other steels and find the same volume of complaints and keep in mind that toughness was a constant promotional aspect of this steel.

However, 440C is usually around 58 Rc while D2 is usually at 60, hence the wear resistance is normally going to be higher for D2.

D2 has a much higher wear resistance than 440C due to the carbides, the hardness isn't the critical factor. The wear resistance of D2 at 60 HRC is far beyond 1095 at a higher hardness, this doesn't of course mean the edge retention is greater. Edges cutting soft materials tend to deform as the main part of the edge retention which is why steeling can induce such a strong responce.

The only gripes I have with your graph are that A2 is tougher than O1, even on Crucible's charts. O1 is 30 ft. lbs. at 60 Rc and A2 is 41 at 60 Rc, and the second is you didn't list any hardnesses.

O1, like most low alloy steels has a toughness minimum at that hardness due to cementite precipitation. You really need to look at the temper responce graphs and not just numbers and torsional data is in general much prefered for impact toughness on hard steels. It also needs to be considered that the samples for toughness testing are large and depending on the steel you could be tested something which is just essentially case hardened so it won't apply directly to a knife edge which will be fully hardened. 1095 for example has an extreme torsional toughness because the core of the sample is spring drawn because it is a shallow hardening steel.

-Cliff

 

[Larrin]

I really don't see what you are looking at, S30V has no resemblance to the composition of a tough steel.

I gave all of the reasons why it should be a relatively tough steel, and I compared the toughness to D2, not A8 or a high toughness steel.

Molybdenum doesn't have a specific carbide type, it however will contribute to both the vanadium and chromium rich carbides this is why it isn't listed in the primary carbide fraction of the s30v pdf file from crucible. Wilson discussed the dissolution of the molybdenum carbides with Crucible in regards to his higher temperature soaking.

My information is from Dick Barber, who said that Molybdenum doesn't start to form carbides until percentages above 2%. It does have a specific carbide type, M6C.

Compared to what and of what type? The carbide fraction is fairly standard for a high alloy stainless which are not known for toughness.

Compared to 440C, 154-CM, D2, S90V, etc.

You really need to have some internal numbers to make these arguements such as the carbon/chromum fraction in austenite, the size of the primary carbides (and the type of the chromium carbides) and the amount of carbide precipitates during quench (different for still vs moving air vs oil) and temper.

14% chromium is very low, it is the minimum IMO, the amount in austenite isn't going to be very high.

Yes, however it isn't like you can CPM D2 and have it tougher than conventional A2. Where are the numbers supporting the extent that this process makes to toughness? How tough is RWL34 vs ATS-34?

The numbers are in the Crucible handbook. I never said that making a CPM D2 would make it tougher than A2. The toughness differences for stainless CPM are unavailble; however, theoretically, there is at least some toughness increase. Crucible does give toughness differences in transverse toughness between S30V and 154-CM and 440C. Transverse toughness increases are the biggest with CPM.

His favorite tough tool steel is M4? M4 is a high wear HSS used over M2 when you need wear resistance and not toughness.

I said his favorite tool steel is CPM-M4, not M4, which has quite a bit higher toughness than M2. He also heat treats it closer to 60 Rc than the 63-65 that they heat treat to for high speed. At 60 Rc it should have toughness close to A2. He likes it for a very good balance of toughness and edge retention, both are very high in his testing.

Is it really more believable that there is some huge conspiracy than there could be a problem with a high wear steel in regards to toughness. Do some searching, the threads on S30V turn up in scads. You can find problems where individuals have bought several knives and have seen problems in 60% of them and multiple knives from different manufacturers all having problems, blades being returned and getting replaced and those having problems.
Pictures have been posted as well and the damage is large and visible.

I have seen solid performance from S30V in regards to slicing aggression edge retention and blades which are as durable as high alloy stainless in general. I have also seen several blades which would not sharpen, and others which both dented and chipped easily as well broke easily under light impact. Again, do some searches on other steels and find the same volume of complaints and keep in mind that toughness was a constant promotional aspect of this steel.

I've read the threads. My only guess is that the heat treating of S30V has been poor. My use of S30V (in a small sebenza) hasn't shown any chipping, even with abrasive materials such as plastic and carboard, I haven't, of course, been chopping with it. Also, looking at all of the numbers (testing and composition) like I've been talking about, I see no reason why it would have problems with chipping, other than the high wear resistance; however, it has a low carbide volume compared to steels like 154CM to minimize this detriment as much as possible.

D2 has a much higher wear resistance than 440C due to the carbides, the hardness isn't the critical factor. The wear resistance of D2 at 60 HRC is far beyond 1095 at a higher hardness, this doesn't of course mean the edge retention is greater. Edges cutting soft materials tend to deform as the main part of the edge retention which is why steeling can induce such a strong responce.

If you read the rest of my post, you'd see that my information is from Wayne Goddard, who found the 154CM, 440C, and D2 could make a similar number of cuts at the same hardness.

O1, like most low alloy steels has a toughness minimum at that hardness due to cementite precipitation. You really need to look at the temper responce graphs and not just numbers and torsional data is in general much prefered for impact toughness on hard steels. It also needs to be considered that the samples for toughness testing are large and depending on the steel you could be tested something which is just essentially case hardened so it won't apply directly to a knife edge which will be fully hardened. 1095 for example has an extreme torsional toughness because the core of the sample is spring drawn because it is a shallow hardening steel.

I have looked at the temper response, it also shows A2 as having higher toughness than O1.

 

[Cliff Stamp]

I gave all of the reasons why it should be a relatively tough steel, and I compared the toughness to D2, not A8 or a high toughness steel.

I would agree it would be similar in toughness to D2, but in general it is very difficult to take a complex blend of alloys and predict material properties let alone try to predict physical behavior when this is a complex dependance on the properties.

My information is from Dick Barber, who said that Molybdenum doesn't start to form carbides until percentages above 2%. It does have a specific carbide type, M6C.

Thanks, I got differnet from Crucible who noted Moly won't change the carbide type just diffuse into existing. The 2% cutoff seems odd as you can see a secondary hardening as low as 0.5% Moly and that is from carbide precipitation. It is really strong at 2% so I would expect it to be in the primary carbides since they cool through that temperature to anneal it. You can find all of this in standard references. I'll drop Barber and email and show him the graphs and get his responce.

14% chromium is very low, it is the minimum IMO, the amount in austenite isn't going to be very high.

The minimum needed is 11/12 in the ferrite, considering the effect on the volume fraction you can achieve this with much lower than 14% in total because the volume you need to protect doesn't include the carbides.

Crucible does give toughness differences in transverse toughness between S30V and 154-CM and 440C. Transverse toughness increases are the biggest with CPM.

This is not overly significant in general because you don't load a blade significantly along that line, you are essentially trying to split it from point to pommel. Have you ever seen a blade break in that manner even in the steels for which it is really low like 440C?

I said his favorite tool steel is CPM-M4, not M4, which has quite a bit higher toughness than M2.

Crucible has a published temper responce comparing powder M4 to ingot M2? Can I see it?

He also heat treats it closer to 60 Rc than the 63-65 that they heat treat to for high speed.

I like HSS, but not there. I would really be interested in data which supports M4 vs A2 at 60 HRC, powder or otherwise. You are looking at a much higher cost in steel, that is an odd steel to try to blend properties including toughness considering it is a high wear replacement to M2.

I've read the threads. My only guess is that the heat treating of S30V has been poor. My use of S30V (in a small sebenza) hasn't shown any chipping, even with abrasive materials such as plastic and carboard, I haven't, of course, been chopping with it.

Your last sentance is a glaring problem commonly used to defend the performance. Why would you expect that to be a problem given this was one of the promotions of the steel and it is heavily used in tactical knives? Chipping generally isn't caused by wear and thus I don't see why you would say "even with abrasive materials" chipping is a fracture issue so it going to be either impact or high loading. Plastic isn't in general abrasive, it can however be demanding from a strength perspective when thick as it loads edges laterally.

As noted I have seen some decent and not so decent performance out of S30V, but others have seen much worse and you simply can't ignore them. It would be just as problematic for the people having problems to ignore the positive reports. Writing it off as a heat treatment issues just raises more issues since this was a steel specifically designed for ease of heat treatment by knife makers and powder steels are in general supposed to give more consistent heat treatment responce so this really raises questions.

I have looked at the temper response, it also shows A2 as having higher toughness than O1.

Yes, in general, I was just pointing out that you don't want to compare O1 at 60 HRC in regards to toughness, nor other steels of similar composition, nor in general do one shot thoughness comparisons because of the nonlinear dependance of the temper responce.

-Cliff

 

[Stacy E. Apelt - Bladesmith]

Just to throw some more wood on the fire -
It has been my observation that many(most) of those who complain that their S30V (or other tough steel) chips easily have reshaped the blade geometry from the original edge to make it sharper.(or the maker made it with the wrong angle and shape). A chopper with an 11 degree hollow grind will chip easily regardless of how good the steel is.The desire for scary sharp edges and hairless left arms leads many to mis-match the edge to the job.The quest for super hard steels can cause the wrong steel to be used,or an improper HT, in the same way.
There is no need for all knives to be Rc 63. Many old timers just knowingly smile at those who tout their high hardness blades.( I have seen boasts of finished blades at Rc67).They have learned through experience that a 1095 blade with a 17 degree flat grind and a good HT to Rc 56-58 will most likely outlast and outcut a specialty steel knife made too hard and with the wrong angles.Hardness and toughness are products of the HT - Cutting and durability are products of the design (which includes the HT).
Stacy

 

[Larrin]

Just to throw some more wood on the fire -
It has been my observation that many(most) of those who complain that their S30V (or other tough steel) chips easily have reshaped the blade geometry from the original edge to make it sharper.(or the maker made it with the wrong angle and shape). A chopper with an 11 degree hollow grind will chip easily regardless of how good the steel is.The desire for scary sharp edges and hairless left arms leads many to mis-match the edge to the job.The quest for super hard steels can cause the wrong steel to be used,or an improper HT, in the same way.
There is no need for all knives to be Rc 63. Many old timers just knowingly smile at those who tout their high hardness blades.( I have seen boasts of finished blades at Rc67).They have learned through experience that a 1095 blade with a 17 degree flat grind and a good HT to Rc 56-58 will most likely outlast and outcut a specialty steel knife made too hard and with the wrong angles.Hardness and toughness are products of the HT - Cutting and durability are products of the design (which includes the HT).
Stacy

Heat treat and edge geometry are definitely key. Those that are saying that S30V itself is a steel that isn't tough enough to use is just ridiculous. If there are problems with S30V chipping, there is either a problem with heat treat and/or edge geometry, or they are using it for things that it wasn't intended for, such as chopping. If the problem is that people are chopping with their S30V knives, than I'm definitely convinced that there isn't a problem, most of the problems with chipping were by people with folders, folders are not made to chop with, they're hard and thin.

 

[Cliff Stamp]

It has been my observation that many(most) of those who complain that their S30V (or other tough steel) chips easily have reshaped the blade geometry from the original edge to make it sharper.(or the maker made it with the wrong angle and shape).

The majority of the problems reported with S30V chipping are with the initial edge bevels. There have been some regrinds and some have lowered the edge angle but they have also done the same with other stainless which hold at more acute angles such as Mat who noted that his Buck in 425mod held a lower angle than his Sebenza :

http://www.bladeforums.com/forums/showpost.php?p=3700522&postcount=5

This isn't the only example of such a comparison, there are many others VG-10 is a common reference.

A chopper with an 11 degree hollow grind will chip easily regardless of how good the steel is.

I don't know what a 11 degree hollow grind means because a hollow grind doesn't have one angle, but most of my chopping blades have edges at about 11 degrees per side and they don't chip out because the steel is very tough. If you undercut the angle enough the edge will eventually ripple but the failure mode will actually switch away from fracture to deformation at lower angles because steels can flex much mor readily when thinner.

I have seen boasts of finished blades at Rc67

There are many reasons that having a high hardness in a blade is of benefit. It can make the blade more durable because they are stronger and allow lower edge angles and cutting of materials which can not be cut with softer blades. I have several knives which are of similar hardness, including this :

That is a hollow ground blade, 1095, 66 HRC, edge is 3/6 degrees per side, primary/secondary. It was used to cut away the sod in the picture, it didn't chip either. The temper responce of steels isn't linear, some of them have toughness peaks at a high hardness and drawing the temper makes them both weaker and more brittle. If you are not chopping, but cutting, in general you want strength more than impact toughness so lower hardness tends to mean a less durable blade. Hardness really isn't the issue with chipping though as most people hardening S30V are actually running it *softer* than the steels it replaced, not harder, and at the hardness that Crucible advocates usually.

Those that are saying that S30V itself is a steel that isn't tough enough to use is just ridiculous.

Why is it ridiculous when that is what their use has seen and their reports are not contended aggressively by the makers. It is the obvious and reasonable conclusion especially when excuses start to be made for the steel which only adds support to the fact there is a problem.

If there are problems with S30V chipping, there is either a problem with heat treat and/or edge geometry, or they are using it for things that it wasn't intended for, such as chopping.

It was promoted for that and how do you then explain that they are doing the same things with other knives, there are many direction comparisons against VG-10 for example. Some of the problems have been with :

-cutting cardboard
-cutting plastics
-cutting corn stalks (yes, corn stalks)
-cutting plywood
-removing bark
-cutting fuzz sticks

and the list goes on. You can find all of these public complaints on the forums and it isn't uncommon to find people with problems with multiple knives, repeat problems with knives returned, and problems across multiple manufacturers, and these are not inexpensive knives either. As for the arguements, how can it be simply wrote off as a heat treatment issue when S30V was designed specifically for ease of heat treatment by knifemakers, promoted specifically as being superior to 440C in regards to heat treatment and in general CPM is supposed to be superior in that regard?

If the problem is that people are chopping with their S30V knives, than I'm definitely convinced that there isn't a problem, most of the problems with chipping were by people with folders, folders are not made to chop with, they're hard and thin.

First off all the edges on the folders that people are talking about are far more obtuse than actual wood cutting blades. Read Cook's book on axes to see how actual chopping axes are supposed to be ground or Lee's book on sharpening. I have yet to see a folding knife which came with an edge which was more acute than what I run on my large chopping knives which obviously impact wood far harder than a light pop with a folding knife. Secondly S30V was again promoted by Crucible for large blades as a tactical knife steel. It is in no way then excusable to critize someone who does light chopping with a small knife with the same steel, especially when the same folders are being sold as "survival" and "tactical" folding knives. Thirdly the majority of complaints are about cutting not chopping.

-Cliff

 

[Cliff Stamp]

I have spoke to Barber about the molybdenum carbide issue. After S30V is heat treated according to Crucible specifications the primary carbide will be dominated by vanadium rich and chromium rich types of carbides, rich meaning the majority of those types is vanadium and chromium. Carbides are in general combinations, how much of each will depend on the alloy content. Molybdenum is a strong carbide former, so much so it will induce a secondary hardening reponce at 0.5%, however in S30V there are four vanadium to every one molybdenum (moly is twice as heavy) and vanadium is a stronger carbide former and combines to form carbide in a lower ratio with carbon. Moly does form carbides, just not enough to dominate the forms.

As an example, I was looking for specific carbide breakdown, and didn't find something similar to S30V, but to give you an idea of the intermixing and complication of carbide types in general, here are some details on a HSS, specifically 2.0C, 5.0V, 3.0Mo, 1.5W, 6.5Cr. This steel after hardening will contain MC, M2C and M7C3 carbide, the breakdown percentages for Vanadium will be 74,9,11 and for Moly, 5, 38 and 8, and for Chromium 8,11, 37, there is still iron carbide in those as well at 4,7, 40. The volume fraction of M2C is also very low compared to the others and it forms alongwith M7C3 and is included in its volume fraction. Thus basically you have a vanadium and chromium rich primary carbide, but all of the alloys and even the iron form carbides. There is also M23C6 carbide precipitated during the tempering and it also has an influence on how properties of the steel during wear. This is from a paper by Jung Ho Lee et al. in ISIJ International on wear in HSS. If you are interested specifically on the physics of moly carbide (M2C) there has been research done specifically on it as well, interesting reading but not from a practical knife/steel viewpoint. You can just look at a steel under magnification and determine the carbide forms, that is where Crucible got the numbers in the PDF file on S30V for example.


-Cliff

 

[Larrin]

I spoke again to Scott Devanna about the investigated knives with chipping problems. All of them had untempered martensite. All steels are brittle with untempered martensite. Except for one that they investigated, somebody had decided to regrind it and ruined it.

 

[Cliff Stamp]

So Buck, Chris Reeve, Benchmade, Camillus, and Spyderco (all have seen reports of such issues) are forgetting to temper some of the S30V blades but have no such issues with ATS-34, VG-10, 420HC, etc. . I would have assumed that the same general quality control procedures are on on the steels and since untempered martensite is brittle in general, all the steels would therefore have similar problems. Now maybe he meant retained austenite transforming into martensite at the edge through strain, but is this again a specific problem inherent to S30V more so than other similar stainless? This is the question of course, why is there a much higher report of problems with S30V, not that problems are found because they will be with all steels.

-Cliff

 

[Larrin]

So Buck, Chris Reeve, Benchmade, Camillus, and Spyderco (all have seen reports of such issues) are forgetting to temper some of the S30V blades but have no such issues with ATS-34, VG-10, 420HC, etc. . I would have assumed that the same general quality control procedures are on on the steels and since untempered martensite is brittle in general, all the steels would therefore have similar problems. Now maybe he meant retained austenite transforming into martensite at the edge through strain, but is this again a specific problem inherent to S30V more so than other similar stainless? This is the question of course, why is there a much higher report of problems with S30V, not that problems are found because they will be with all steels.

-Cliff

S30V would be affected more by using only one temper than those other steels. If you look at the data sheets, all of the steels you mentioned only require one temper (though that isn't to say that two or three isn't better), but S30V needs at least two tempers. I don't want to say that those steel (edit: knife) companies are bad, but companies taking shortcuts in heat treatment isn't unheard of.

Do you really think that S30V cannot be heat treated into a good, tough, working knife? Gayle Bradley and Warren Osbourne have made choppers out of S30V and they both say that it holds up very well. Each said that it is the toughest stainless that they tried. How can you refute that?

 

[DGG]

I'm jumping in on this one. From experience it appears to me that certain owners have had problems with s30v. I don't think they are all imagining this. It is sort of where there is smoke there is fire. However, the majority seem more than happy with the performance so in the overall scheme of things it seems to be a decent knife steel. I thinks you guys can argue until the cows come home and neither will convince the other.

What does my knife hero Mr. Joe Talmadge say about it?

 

[Cliff Stamp]

S30V would be affected more by using only one temper than those other steels.

If you are continuing with the untempered martensite arguement proposed, austenite to untempered martensite transformation will only happen in the high temperature tempers from austensite conditioning due to carbide precipitation which changes the composition of the austenite and raises the Ms point.

If people are using high tempers this could be one of the causes of the problem because there are embrittlement issues with secondary hardening in general. But this doesn't match the reported pattern of problems. It also doesn't explain why some people are getting improved performance after significant sharpening.

Note as well, in general, the result of a second temper would *never* be argued to be so dramatic that it would take a steel from chipping out on cutting corn stalks to being the toughest stainless cutlery steel.

Do you really think that S30V cannot be heat treated into a good, tough, working knife?

I have several S30V blades that I consider as very high quality knives, but if someone asked me for a tough stainless steel I would point towards 12C27mod or similar. I have seen S30V work well in knives which are designed to cut well for a long time, especially on abrasive media. Wilson's knives are excellent examples of such a goal.

To clearify, I don't think the reported problems describe the optimal nature of the steel, a trivial conclusion since not everyone has problems obviously it can work well. What I do find problematic is the very high frequency of reported problems in stark contrast to the promotion of the steel which is often argued to be due to things which directly contradict the origional promotion.

Gayle Bradley and Warren Osbourne have made choppers out of S30V and they both say that it holds up very well. Each said that it is the toughest stainless that they tried. How can you refute that?

It can't be refuted as it is undefined. Which other steels were used and what work was done with S30V where it directly and significantly outperformed VG-10, ATS-34, 420HC, AEB-L, BG-42, 12C27mod, 440A, 440C, etc. in regards to resistance to fracture from impact and bending, meaning the other steels failed to do the same work.

In general, since you want to discuss makers and opinions, contrast that perspective to the work Landes and Verhoeven on stainless and specifically note the issue of edge stability of high carbide stainless steels. Note Landes arguement for 440A over 440C as a superior knife steel for several aspects as a striking contrast to how most makers would rate the steels.

-Cliff

 

[J.Marsillo]

The desire for scary sharp edges and hairless left arms .Stacy

LMAO what do you mean what happened to my left arm hair???

 

[Larrin]

If you are continuing with the untempered martensite arguement proposed, austenite to untempered martensite transformation will only happen in the high temperature tempers from austensite conditioning due to carbide precipitation which changes the composition of the austenite and raises the Ms point.

If people are using high tempers this could be one of the causes of the problem because there are embrittlement issues with secondary hardening in general. But this doesn't match the reported pattern of problems. It also doesn't explain why some people are getting improved performance after significant sharpening.

Note as well, in general, the result of a second temper would *never* be argued to be so dramatic that it would take a steel from chipping out on cutting corn stalks to being the toughest stainless cutlery steel.

Though the upper temper converts the most retained austenite, all tempering converts some austenite to fresh martensite. That's why double tempering is necessary. Also, one of the companies heat treating incorrectly was tempering once for one hour, too much fresh martensite.

I have several S30V blades that I consider as very high quality knives, but if someone asked me for a tough stainless steel I would point towards 12C27mod or similar. I have seen S30V work well in knives which are designed to cut well for a long time, especially on abrasive media. Wilson's knives are excellent examples of such a goal.

I don't doubt that 12C27 mod. has higher toughness than S30V because of lower carbide volume, lower carbon, and a little lower hardness; however, S30V was designed to have a balance of high wear resistance with high toughness.

To clearify, I don't think the reported problems describe the optimal nature of the steel, a trivial conclusion since not everyone has problems obviously it can work well. What I do find problematic is the very high frequency of reported problems in stark contrast to the promotion of the steel which is often argued to be due to things which directly contradict the origional promotion.

So what we need to push for is improvement in heat treatment rather than pushing for a removal of the steel altogether, that's mostly what I'm trying to get across.

It can't be refuted as it is undefined. Which other steels were used and what work was done with S30V where it directly and significantly outperformed VG-10, ATS-34, 420HC, AEB-L, BG-42, 12C27mod, 440A, 440C, etc. in regards to resistance to fracture from impact and bending, meaning the other steels failed to do the same work.

He made chopper knives and put them through a series of chopping 2X4's, aluminum and steel cans, hardwood dowels, rope, etc. He used about 30 steels, among them ATS-34, BG42, and 440C. I don't think he tested 440A or 420HC because he didn't feel a need. VG-10 is unavailable in the U.S. AEB-L is only in smaller thickness, though he has been asking my father to make some in a laminate for testing.

In general, since you want to discuss makers and opinions, contrast that perspective to the work Landes and Verhoeven on stainless and specifically note the issue of edge stability of high carbide stainless steels. Note Landes arguement for 440A over 440C as a superior knife steel for several aspects as a striking contrast to how most makers would rate the steels.

-Cliff

Does Landes make knives? We are big AEB-L fans, but the problem is, more and more people are looking for high weare resistance in their knives. AEB-L has a very good balance of corrosion resistance, toughness, and ease of sharpening, with good edge retention. These days though, people expect their blades to hold an edge for an extremely long period of time, and then take a little longer to get it back. I believe that for its level of corrosion resistance and edge holding, the toughness could not be improved very much for S30V. Where is the Landes information? I've never seen it before.

 

[Cliff Stamp]

Though the upper temper converts the most retained austenite, all tempering converts some austenite to fresh martensite.

Lower tempers can reduced retained austenite in some steels (it depends on the TTT curves) but it will convert it to bainite. Tempering is isothermal so martensite won't form significantly as it is an athermal (or strain induced) process. Allen covers the four stages of tempering well in his book, but doesn't include the effect of the TTT curves. I have seen better treatments in some other more recent works, but they start getting fairly math heavy and without a solid background in thermodynamics (graduate level) it reads really dense. The best source of use information is in Krauss book on tool steels where you will find levels of retained austensite and other such properties discussed in detail.

So what we need to push for is improvement in heat treatment rather than pushing for a removal of the steel altogether, that's mostly what I'm trying to get across.

Though some people are complaining about the steel to this extent, and if I have bought multiple knives and seen defects, returned knives and still saw problems I think I would be looking elsewhere as well, based on what I have seen I regard it well for an aggressive slicer. The real problem is that we as users don't know in general how the knives are being heat treated and there is little information on the pieces returned about what is causing the problem which leads to a really bad image really quickly. It also doesn't help when the arguements start to be contradictory to the promotion of the steel which looks really bad as then it starts being more of an excuse and defence rather than explanation.

He made chopper knives and put them through a series of chopping 2X4's, aluminum and steel cans, hardwood dowels, rope, etc. He used about 30 steels, among them ATS-34, BG42, and 440C. I don't think he tested 440A or 420HC because he didn't feel a need.

That is interesting, and the other stainless saw fracture in similar geometries and S30V didn't? Any independent baselines such as Paul Bos ATS-34 for a reference?

Does Landes make knives?

Yes he has made them, don't know if he makes his living as a knifemaker. You can read the same conclusions found on rec.knives years ago. Alvin Johnston made a bunch of knives and compared edge holding on steels on blades he heat treated as well as done by Bos. At low angles, and looking for high sharpness, the coarse grained steels did poorly regardless of the level of wear resistance, 1095 for example easily outcut Bos ATS-34. He used mainly working professionals as his R&D group, butchers, cowboys, etc. . Mike Swaim did a bunch of quantitative work as well and showed similar effects.

We are big AEB-L fans, but the problem is, more and more people are looking for high weare resistance in their knives.

I don't know as much if they are looking for this or it is just being promoted as the goal. Bark River for example uses 12C27 and they generally get praise for edge retention and it isn't a high wear steel. Much of the benefits of the high wear steels can also be found with lower carbide steels by adjusting edge geometry and choice of finishing grit. The finer grained steels can also be in general made harder and ground more acute. I would wonder how much of it is perception of performance.

I believe that for its level of corrosion resistance and edge holding, the toughness could not be improved very much for S30V.

In general high wear and high toughness tend to be in opposition, but in general there is little use for high wear in knives which see high impact anyway. If you are chopping woods and metals and bone, the edge will deform/fracture long before it wears. I think it may be more of people looking in the wrong place for solutions to problems. Consider for example how long axes were used and did anyone look to the high wear steels which were long since available. In large chopping blades I tend to sharpen to repair damage rather than an actually worn blade and thus to me the lower grindability of the steel would be a serious problem. Without accidental overloading by smashing the edge into a rock, or cutting really dirty bark, it takes a massive amount of wood to be cut before an axe will just wear dull.

Where is the Landes information? I've never seen it before.

Published in books, he is fairly free with it though if you ask him.

-Cliff