440c Problem child or just misunderstood

[me2]

Note, however, that edge retention is largely a function of wear resistance rather than hardness. Increasing hardness CAN increase wear resistance, but this is only one of a few ways to achieve that effect. Steel capable of forming carbides can often be run a little on the tougher side while retaining good wear resistance.

That being said, I'm not a metallurgist. The above is based on my personal experience and readings so take it as you will.

That depends on the kind of edge you want. Makers such as Goddard have found the opposite to be true. For best edge holding, hardness, toughness, and wear resistance all need to be high.

 

[Buck_110]

not poor heat treat, but higher temperature tempering to precipitate more carbides and increase wear resistance at the expense of corrosion resistance.

Tempering is a part/step of the heat treat process.

 

[hardheart]

I... kinda know that. lots of heat treating books and papers and ten years here helped

my point is that it is not a poor heat treat when it is planned and done on purpose

 

[Gator97]

You are content to argue that 440C should be thrown in the garbage, I am willing to accept that it is more than acceptable for many people. If you read what I wrote, I am not a fan of 440C, but that doesn't mean that it shouldn't be used for knives- which is all I can infer that you are talking about.

Not at all. As the OP phrased, or as I understood it, it was more about "440C is still top notch steel, just misunderstood", which was what I was arguing against. Other than that, for majority it'll do, just like 420 or other budget stainless does.
In other words, if you care about steel performance and want good results, then there are many alloys that outperform 440C, if one doesn't care and maintain this knife, then I see no reason to pick 440C specifically... Whatever will be cheaper will do the same.

 

[Buck_110]

my point is that it is not a poor heat treat when it is planned and done on purpose

I agree, but more often than not, poor heat treatment, and not the desire for greater precipitation is the culprit. If it weren't, carbon steel might as well be employed initially.

The point is, comparing steels soley by composition is often pointless; unless they are employed as received from the foundry.
The "all things considered equal" adage equates to zip, as it will never be the case. The finished product is the only true testament. Some manufacturers will make 440C sing and dance. Others will produce knives worthy of little more than spreading butter.

 

[me2]

my point is that it is not a poor heat treat when it is planned and done on purpose

That's highly debatable.

 

[hardheart]

What is debatable? Taking advantage of the secondary hardening response would be something done on purpose, to generate a desired set of properties. If it is not the properties the end user wants, that doesn't make it a poor heat treat. A good heat treat is one that gives the intended results for the person that choose those results among the possibilities.

 

[FortyTwoBlades]

That depends on the kind of edge you want. Makers such as Goddard have found the opposite to be true. For best edge holding, hardness, toughness, and wear resistance all need to be high.

Yes, exactly. My point was rather that you could have two knives of the same design and hardness, but different steels, and one could have better edge retention while maintaining decent impact resistance.

 

[me2]

My point is that I've seen a few heat treatments carried out according to plan and they were what I'd call poor.

42, that can also be true of two knives of the same hardness, design, and steel.

 

[FortyTwoBlades]

Yes, if heat treatment cycles were poor on one and not the other. The above was under the assumption that heat treatment was proper in both pieces.

 

[me2]

Yes, if heat treatment cycles were poor on one and not the other. The above was under the assumption that heat treatment was proper in both pieces.

There is sort of a paradox that happens in the situation you're referring to. More carbides generally means higher wear resistance, and you can indeed run these steels softer in an attempt to get better toughness. However, higher carbide steels are generally less tough in the first place. You can get into a bit of a downward spiral. There is also the tendency of various steels to have peaks in toughness at unexpectedly high hardness. If you can find it, and consistently hit the peak, you can get the best of both. I personally don't see a point in softening a high wear steel for the sake of toughness, unless a different steel is not available.

 

[hardheart]

If the steel is homogeneous, and your equipment accurately measures temperature across the chamber, then the same steel heat treated with the same protocol will return the same results. I am a broken record, but tool steels are used in applications well beyond sporting knives. They have to be heat treated in thick sections, in intricate designs, for parts that are much more dependent on wear, corrosion resistance, and toughness.

Most knife users would not be able to tell the difference between 440C and S30V, but volume manufacturers have to see a difference to justify the expense, meet production expectations, and maintain safety. If S30V, or any steel, could not be heat treated reliably and repeatedly, it wouldn't be on the market very long. Heating with a blowtorch and dunking in used motor oil makes a usable knife, but does not make very good hardened steel. The varying levels of quality in heat treat equipment that can make a knife, and the low demands on most of them, means that there could be poor heat treats all around. But those who use properly designed, calibrated, and maintained equipment should be getting similar results in every batch.

 

[Ed Fowler]

"But those who use properly designed, calibrated, and maintained equipment should be getting similar results in every batch." Providing the quality control of the steel available to knife makers insures the steel is the same in each batch.

 

[Noctis3880]

If the steel is homogeneous, and your equipment accurately measures temperature across the chamber, then the same steel heat treated with the same protocol will return the same results. I am a broken record, but tool steels are used in applications well beyond sporting knives. They have to be heat treated in thick sections, in intricate designs, for parts that are much more dependent on wear, corrosion resistance, and toughness.

Most knife users would not be able to tell the difference between 440C and S30V, but volume manufacturers have to see a difference to justify the expense, meet production expectations, and maintain safety. If S30V, or any steel, could not be heat treated reliably and repeatedly, it wouldn't be on the market very long. Heating with a blowtorch and dunking in used motor oil makes a usable knife, but does not make very good hardened steel. The varying levels of quality in heat treat equipment that can make a knife, and the low demands on most of them, means that there could be poor heat treats all around. But those who use properly designed, calibrated, and maintained equipment should be getting similar results in every batch.

I thought S30V was one of very few steels specifically designed for use in cutlery? Thus I'm not so sure volume manufacturing applies to S30V.

 

[hardheart]

Yes, S30V was reportedly tweaked for cutlery with input from makers like Chris Reeve. It also doesn't cost as much as the "Killer V" CPM steels. It is more commonly used in knives than S90V, 9V, 10V, etc, so I chose it as an example. It is listed in Crucible's publications for mold & tool steels for the plastics industries and sold by suppliers for these applications.

Ed - That's why I opened with the point that the steel needs to be homogeneous. You have to know what steel you are working with first.

 

[FortyTwoBlades]

There is sort of a paradox that happens in the situation you're referring to. More carbides generally means higher wear resistance, and you can indeed run these steels softer in an attempt to get better toughness. However, higher carbide steels are generally less tough in the first place. You can get into a bit of a downward spiral. There is also the tendency of various steels to have peaks in toughness at unexpectedly high hardness. If you can find it, and consistently hit the peak, you can get the best of both. I personally don't see a point in softening a high wear steel for the sake of toughness, unless a different steel is not available.

Cool--didn't know about whole peaks in toughness thing. Thanks for that! My main point was just illustrating that hardness isn't everything in determining edge retention.

The biggest thing I've noticed that affects edge retention, though, is how you actually use the knife! If you cut resistant materials with poor technique you can cause greater edge wear than if you approached the same task differently. I think this is possibly why many folks comment on machetes not holding an edge very long. I rarely, if ever, have to field sharpen my machetes and many of them are the same ones that folks complain of not holding an edge well. If you botch a cut on a knot, for instance, your edge is likely to suffer.

 

[Ankerson]

Yes, S30V was reportedly tweaked for cutlery with input from makers like Chris Reeve. It also doesn't cost as much as the "Killer V" CPM steels. It is more commonly used in knives than S90V, 9V, 10V, etc, so I chose it as an example. It is listed in Crucible's publications for mold & tool steels for the plastics industries and sold by suppliers for these applications.

Ed - That's why I opened with the point that the steel needs to be homogeneous. You have to know what steel you are working with first.

Yeah Crucible already had the steel that was to become S30V before Reeve even thought about it.

 

[Ankerson]

"But those who use properly designed, calibrated, and maintained equipment should be getting similar results in every batch." Providing the quality control of the steel available to knife makers insures the steel is the same in each batch.

How often does that happen.

 

[Ankerson]

There is sort of a paradox that happens in the situation you're referring to. More carbides generally means higher wear resistance, and you can indeed run these steels softer in an attempt to get better toughness. However, higher carbide steels are generally less tough in the first place. You can get into a bit of a downward spiral. There is also the tendency of various steels to have peaks in toughness at unexpectedly high hardness. If you can find it, and consistently hit the peak, you can get the best of both. I personally don't see a point in softening a high wear steel for the sake of toughness, unless a different steel is not available.

That's why the high carbon V steels that can be taken to high HRC hardness seem to do better toughness and strength wise than the ones that can't be taken as high.

 

[Ed Fowler]

It has been stated since the days of Webster Marble that over 90% of those who purchase knives will never use them, (reportedly his quote) most will never know.

I have only made one knife out of 440C and that was from a ball bearing, we did not get a chance to test it completely, but the blade was tough and cut well. I know very little of the history or properties of 440C, how many outfits have made it and the variables involved.

Every batch of steel will vary, sometimes a lot, sometimes insignificantly. When I lucked into two steels developed to meet high quality control, tested the blades and noted the true joy of working with steel was close to the same or from the same pour I was very thankful for the lack of unknown variables we did not have to attempt to work with. This is the reason I mentioned quality control.