Johanning's Modified A-8

Cobalt

Cobalt

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Does anyone know what knifemakers have had experience with this steel?

His is modified a little, I think it has more Chromium in it, but not sure.

So who else uses this steel aside from Johanning? Custom or production?
I asked this question on shop talk and custom forum with no response.
 
The modified refers to 3% more Chromium, most people using air hardening steels use A2 and when they want something tougher they use 3V. The guys who forge tend to use 5160, L6 and such.

-Cliff
 
The modified A-8 is Chipper Knife, commonly used in wood chipping equipment. The legendary INFI is the same stuff.
 
Satrang said:
The modified A-8 is Chipper Knife, commonly used in wood chipping equipment. The legendary INFI is the same stuff.
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Interesting. However, Mod A8 is not INFI, that has already been discussed in the past. That was a myth. Both steels have different microconstituents. The only similarity is tha they both have about the same amount of Carbon and Chromium, the similarities end there. However, Johanning seems to have good luck with it and it appears to be much tougher than A2, so I was wondering who else has tried it, but it doesn't seem like anyone has aside from Johanning
 
Satrang said:
The modified A-8 is Chipper Knife, commonly used in wood chipping equipment. The legendary INFI is the same stuff.
Click to expand...

Johannings modified A8 :

0.55% Carbon
0.30% Manganese
0.95% Silicon
8.25% Chromium
1.25% Molybdenum
1.25% Tungsten

InFi :

0.5% Carbon
8.25% Chromium
1.3% Molybdenum
0.36% Vanadium
0.74% Nickel
0.11% Nitrogen
0.95% Cobalt

Not the same steel, and of course though several makers have kept propogating such rumors, none have actually made a knife out of modified A8 which could duplicate the live performance tests done by Busse.

-Cliff
 
There may be subtle differences but they both are Chipper Knife varieties, just produced by two different mills. Infi is Bohler's and Johannings is Viking by Uddeholm. Not identical but brothers.
 
Satrang said:
There may be subtle differences ...
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The composition of modified A8 is known as is the one for INFI I listed in the above which has been verified multiple times by independent people on the forums, which is where the above numbers come from, materials testing on Busse knives, there is no may.

As for "subtle differences", INFI has four elements modified-A8 does not, lacks several it has, and is the same in only one, and two more are likely within steel tolerances. The two steels also don't act the same, having used both of them.

Johanning also uses a very different hardness as well which is a significant influence on the performance.

-Cliff
 
You're splitting hairs on the alloys. The major elements, carbon, chromium and moly are identical. What you list is correct but not complete. Both alloys contain all the elements listed. I suggest you take a blade made of Infi, and a blade of A8 mod and have a local lab do a spectrographic test on the material. Do carbon and nitrogen also. They won't differ by that much. Same base alloys. I'm with you on the hardness point. These grades can and should be run on the high side to optimize their performance. They gain little toughness as the hardness goes down.
 
Satrang said:
What you list is correct but not complete.
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The composition of A8 comes from Bryson who cites ASM as his reference, matweb has the same, no Cobalt, Vanadium Nickel or Nitrogen, Johanning notes the difference in his modified version is the Cr. As for splitting hairs, do you have any ASM data which show that the elemental additions as noted make no significant difference in the heat treating and performance of the steel. What exactly is your conclusion based upon that Johanning's steel is the same as INFI?

-Cliff
 
Satrang said:
There may be subtle differences but they both are Chipper Knife varieties, just produced by two different mills. Infi is Bohler's and Johannings is Viking by Uddeholm. Not identical but brothers.
Click to expand...

yah brothers from different mothers and raised by different uncles.:jerkit:
 
I'm not saying they are identical. I'm saying they are the same parent alloy with slight modifications. ASM and Matweb are not complete references for the alloys contained in steels. They only list the elements required for reporting not the residuals or modified elements. Most of those sources also list only the nominal compositions and not actuals. Only the steel certifications from the mills and an actual test on the metal by a lab can give you the complete breakdown of what is in the actual steel. I've got some mill certfications on these materials in my office that I will post here next week when I get back in the office. The modifications do effect the steel more in the form of ease of heat treatment and attainable hardness. As for performance, the modifications typically don't change the alloys dramatically, hardness bumps and heat treat helpers.

One word of advice for anyone buying steel from a vendor is to ask for the mill certification on their steel. Even distributors have access to this information from the mills and it is worth having for reference. Otherwise you will only have rough nominal chemistries.
 
It will be interestng to see that. However, even slight percentages of microconstituents will change the property of a steel dramatically. Yes the base alloys are identical, however, it is a known fact that several of the extra ingredients in INFI make it that much better overall. Co and Ni are just two that make a huge difference in wear and toughness of this steel.

However, modified A8 appears to be a very good steel and I just wonder why it is that only Johanning that is using it.
 
These types of steels are hard to come by just due to the sizes. Most if not all of this type of alloy is used for the wood chipping industry. Very rarely is it rolled down below 1/2 inch in thickness. You could order it from the suppliers in thinner sizes but the mill minimums are quite big. Even though they have nice properties toughness wise, wear is limited and the heat treatment is borderline oil quench. Many of the major wood chipper knife manufacturers have their blades oil quenched for maximum hardness and structure. If you want to check out alloys beefed up for better wear and are in the same base alloy group, look at K340 by Bohler and Sleipner from Uddeholm.
 
Satrang,
Your posts in this thread are very informative. Jerry Hossom suggested that the two steels were very similiar as well.
Infi is Bohler's and Johannings is Viking by Uddeholm.
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Does Bohler sell INFI under another name as well?
 
Bohler never made INFI by name. Their brand name is K329. INFI was created by the knife manufacturer. Nice little marketing tactic to keep the competitors thinking.
 
Actual K329 chemistry
Carbon: 0.51
Silicon: 0.92
Manganese: 0.38
Phosphorus: 0.017
Sulfur: 0.003
Chromium: 7.80
Molybdenum: 1.29
Vanadium: 0.39

Comments on elements not reported on certification

Nickel: Kept below 0.40
Tungsten: Kept below 0.30

The first thing to notice is this actual chemistry does not match the above listed chemistries. I would be curious to see what the actual certified chemistries of those two materials are.
 
Satrang said:
I'm not saying they are identical.
Click to expand...

At first you did :

Satrang said:
The modified A-8 is Chipper Knife, commonly used in wood chipping equipment. The legendary INFI is the same stuff.
Click to expand...

Then you changed it to say they are not the same, but come from the same parent alloy which is very different .

ASM and Matweb are not complete references for the alloys contained in steels. They only list the elements required for reporting not the residuals or modified elements. Most of those sources also list only the nominal compositions and not actuals. Only the steel certifications from the mills and an actual test on the metal by a lab can give you the complete breakdown of what is in the actual steel.
Click to expand...

What was being compared was the composition of AISI A8 which is a specific tool steel vs INFI which has a specific composition as noted in the above from samples studied. You can't say INFI is AISI A8 modified with higher Cr because it doesn't match that composition.

Once you modify the specifications listed for the AISI designation of the tool steel which are given in the ASM references, it no longer is that tool steel. Just like Spyderco stopped called the Byrd steel 440C when they found out the Japanese version didn't match the AISI standard.

The modifications do effect the steel more in the form of ease of heat treatment and attainable hardness. As for performance, the modifications typically don't change the alloys dramatically, hardness bumps and heat treat helpers.
Click to expand...

They can be dramatic to the performance of the knife, in particular ease of heat treatment being a fairly obvious influence on the performance of the steel because of the ability to get consistent performance and attainable hardness is also fairly critical.

Some of the other elements can also be relevant in small amounts, much was made about the nitrogen in S30V for example for its effect on corrosion resistance and the same amount is in INFI but not in K329. However due to how INFI is tempered it likely isn't enhancing corrosion as much as wear.

K329 is closer to INFI than AISI A8 with extra Cr, but still lacks the Cobalt and Nitrogen found in INFI. Does the mill also have the relevant materials data for the steel. I would be very curious to know if the tempering responce is the same for one, and the impact/strength/ductility info is always useful.

-Cliff
 
The parent alloy is A-8. The major modifications to A-8 are Chromium and nickel additions. That becomes the parent alloy for the Wood Chipper family. Each mill makes subtle variations after that to form their proprietary mix. Johanning's and Infi are both Chipper Knife varieties. Uddeholm, Boher, Timken, and even the Chinese all tweak that parent somewhat afterwords to their own final mix. Performance wise they all fall within a narrow band of properties. In the wood industry, they can't tell the difference. If you can tell the difference in cutlery it's not the steel its the heat treatment, geometry, and hardness, etc. that's really affecting how it cuts. Do me a favor Cliff, ask Busse if they ever bought K329. That will end that part of your argument.

Cliff, as for what alloys do in steel and what has major or minor effects on steel, come to the Oregon Knife Collectors Show in April and I'll be glad educate you on what they do. Bring your ASM books, you'll need them.
 
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