Discussion on D2 Impact Resistance.

[bill_zeng]

Today, I had a disagreement with a friend on the forum about the strength of D2 steel.

D2 steel is a type of steel with relatively poor impact toughness. Many people are familiar with this statement.

Many people know that its impact resistance is not strong, but few know how weak it is.

I have repeatedly expressed to my friends that D2 (SKD11, SLD) at HRC 60 has much better toughness than Japanese knives made of SG2, such as those from Tojiro, Sakai Takayuki, JIKKO, and Kurosaki Yu

But, many people think I'm joking.

I am a serious person. I used to be a certified aircraft powerplants engineer by the Transport Canada.

So today I conducted a test. I used a 15 to 16-degree edge angle to cut chicken wing bones to compare the edge strength of SG2 and D2 steel.

Both are gyutos with almost the same edge angle and almost the same edge thickness.

This point is very important, extremely important.
Only with the same edge angle and thickness can the cutting performance be accurately compared.


Test conditions:
Materials: TAKEFU SPECIAL STEEL CO LTD SG2 AND LIAONING FUSHUN SPECIAL STELL CO LTD D2
HRC: SG2 62 D2 60
Knife maker: SG2 TAKAYUKI D2 me
Edge angle: 15~16 degrees

The result is that SG2 chipped, while D2 remained almost intact. Below are the test vedios and pictures.

The purpose of this test is not to compare SG2 and D2, but to highlight a phenomenon. Many people claim that D2 is fragile, but in reality, it is still tougher than many other knife steels.

Those of us who are into cars often say that the Dodge Challenger V6 version is weak.

But the "weak" V6 Challenger is still more powerful than a Toyota Corolla.

 

[bill_zeng]

 

[Troopah_Knives]

Just to clarify are you saying that D2 has better strength (yield strength) or toughness then SG2?

 

[bill_zeng]

Just to clarify are you saying that D2 has better strength (yield strength) or toughness then SG2?

I prefer to say that the edge can withstand higher impact energy without damage.

 

[azn_knives_4l]

I prefer to say that the edge can withstand higher impact energy without damage.

Words are so challenging but your videos help. Thanks so much

 

[bill_zeng]

Words are so challenging but your videos help. Thanks so much

Haha, yes, the text can be dull. But videos and pictures are much more intuitive. Seeing the edge chip after cutting is easier to understand than any words.

 

[Redwax]

I don't think it is a big surprise that D2 at 60HRC is slightly tougher than SG2 at 62-63 HRC.

If you look at the tests Larrin has done on knifesteelnerds.com he has data that indicates that D2 at just over 60 HRC has a charpy impact result of around 5 ft-lb, and SG2 at around the same hardness came in at around 7 ft-lb. If you look at the trend of reduced toughness as you increase hardness you could estimate that at 62-63 HRC that SG2 would be below 5 ft-lb.

Overall SG2 appears to be a tougher steel generally, but the hardness that you commonly find in Japanese kitchen knives means that toughness isn't the desired strength or priority. If you used a similar philosophy with SLD/D2 and went for 62-63 HRC it would most likely be more prone to chipping than SG2.

 

[Jville]

Yeah imho having one steel at 60 and another at 62 creates a variable of HRC that is not controlled.

 

[azn_knives_4l]

Yeah imho having one steel at 60 and another at 62 creates a variable of HRC that is not controlled.

I don't think that matters. OP clearly stated these parameters in his description and made no broad claim that D2 is generally tougher than SG2. His claims are appropriately limited to the experimental design presented.

 

[jedy617]

I don't think that matters. OP clearly stated these parameters in his description and made no broad claim that D2 is generally tougher than SG2. His claims are appropriately limited to the experimental design presented.

"I have repeatedly expressed to my friends that D2 (SKD11, SLD) at HRC 60 has much better toughness than Japanese knives made of SG2"

 

[azn_knives_4l]

"I have repeatedly expressed to my friends that D2 (SKD11, SLD) at HRC 60 has much better toughness than Japanese knives made of SG2"

Correct. This is exactly his statement, your statement, and the demonstration. OP made no statement to 'D2 is tougher in general than SG2'.

 

[jedy617]

right but that statement is just false lol (and uhh it does seem to be what he is getting at) Who cares if the knife is japanese or not? He is saying d2 is "much tougher" which could not be farther than the truth

 

[Redwax]

Correct. This is exactly his statement, your statement, and the demonstration. OP made no statement to 'D2 is tougher in general than SG2'.

He did say in the other thread that D2 at the same hardness of VG10 and SG2 is tougher. It isn't.

The main reason you would use D2 over SG2 would be cost. SG2 can be heat treated at 60 HRC if you wanted to increase toughness, and would be more corrosion resistant with similar wear resistance.

 

[jedy617]

I was looking for that thread, just realize he didn't post that.

Edit: " However, compared to commonly used steels like VG10, AUS10, and SG2, D2 steel's edge impact resistance is not inferior. Additionally, it is more wear-resistant and its cutting feel is closer to that of carbon steel."

No, it is in fact inferior in impact resistance and wear resistance.

Compiled data by Larrin, this is not a perfect comparison I will admit, but literally the only high alloy tool steels with worse toughness is Rex121 and Maxamet which is like pure carbide, and ZDP with 3% carbon... D2 is just a relic of the past at this point. Cost is the only reason to use it.

 

[blokey]

Honestly D2 at 60 HRc is tougher makes sense, per Larrin's graph D2 at 60 HRc is 5ft-lbs, SG2 at 60.5 is barely 6-7 ft-lbs, but at 62 or higher in usual Japanese knife is gonna be lower, tho they are all bottom of the bunch in toughness
https://knifesteelnerds.com/2021/10...ness-edge-retention-and-corrosion-resistance/

 

[Redwax]

I was looking for that thread, just realize he didn't post that. Is @azn_knives_4l an alt account? asian knives for less?

?

I was talking about what the OP said

 

[azn_knives_4l]

I was looking for that thread, just realize he didn't post that. Is @azn_knives_4l an alt account? asian knives for less?

Edit: " However, compared to commonly used steels like VG10, AUS10, and SG2, D2 steel's edge impact resistance is not inferior. Additionally, it is more wear-resistant and its cutting feel is closer to that of carbon steel."

No, it is in fact inferior in impact resistance and wear resistance.

Compiled data by Larrin, this is not a perfect comparison I will admit, but literally the only high alloy tool steels with worse toughness is Rex121 and Maxamet which is like pure carbide, and ZDP with 3% carbon... D2 is just a relic of the past at this point. Cost is the only reason to use it.
View attachment 327619

Please describe the heat treat protocol underlying this table otherwise it is not applicable to the demonstration from OP in this thread.

 

[jedy617]

?

I was talking about what the OP said

Yeah I know, I thought OP said that D2 was tougher and had more edge retention here, forgot it was in the SLD thread

 

[blokey]

We are getting bit hot headed here, just calm down, OP shared his experience and I think it is valid, SG2 and D2 are both pretty low in toughness, any factor could change in one’s favor

 

[blokey]

I think we also might be missing that melting process for ingot steel does matter, example like Nitro-V and 14C28N, they should be close in toughness but 14C28N comes quite bit ahead in Larrin’s test, SLD is Electro Slag Remelted if I remember correctly, that extra bit of cleanliness might contribute to slightly higher toughness

 

[blokey]

No, I couldn't find the misinformation from the OP in this thread, it was in the SLD thread that directly countered "OP clearly stated these parameters in his description and made no broad claim that D2 is generally tougher than SG2."

Wasn't really an attack on integrity, just wondering if you were an alt account. Your name is azn knives 4 less, OP sells cheaper asian knives, you are a newer account, saying weird stuff like: "words are so challenging but your videos help. Thanks so much" ? (what does that even mean) and you are passing on bad info from him lol

I think that’s bit unwarranted… His name is more likely Asian knife for life

 

[jedy617]

I think we also might be missing that melting process for ingot steel does matter, example like Nitro-V and 14C28N, they should be close in toughness but 14C28N comes quite bit ahead in Larrin’s test, SLD is Electro Slag Remelted if I remember correctly, that extra bit of cleanliness might contribute to slightly higher toughness

For sure, but he said he was testing with "LIAONING FUSHUN SPECIAL STELL CO LTD D2"

 

[jedy617]

Honestly D2 at 60 HRc is tougher makes sense, per Larrin's graph D2 at 60 HRc is 5ft-lbs, SG2 at 60.5 is barely 6-7 ft-lbs, but at 62 or higher in usual Japanese knife is gonna be lower, tho they are all bottom of the bunch in toughness
https://knifesteelnerds.com/2021/10...ness-edge-retention-and-corrosion-resistance/

The problem was in this thread: https://www.kitchenknifeforums.com/threads/sld-steel-any-good.72306/

he flat out said: "" However, compared to commonly used steels like VG10, AUS10, and SG2, D2 steel's edge impact resistance is not inferior. Additionally, it is more wear-resistant and its cutting feel is closer to that of carbon steel." which is just really wrong. No mention of HRC differential or anything

 

[blokey]

For sure, but he said he was testing with "LIAONING FUSHUN SPECIAL STELL CO LTD D2"

Yeah miss that part but they might still be difference in melting contribute to it, even in standard D2, 60HRc could potentially be tougher than high hardness SG2 as shown in Larrin’s graph, it’s more that SG2 has surprisingly low toughness for a PM steel at that range

 

[blokey]

The problem was in this thread: https://www.kitchenknifeforums.com/threads/sld-steel-any-good.72306/

he flat out said: "" However, compared to commonly used steels like VG10, AUS10, and SG2, D2 steel's edge impact resistance is not inferior. Additionally, it is more wear-resistant and its cutting feel is closer to that of carbon steel." which is just really wrong. No mention of HRC differential or anything

That might be an overstatement without additional information, but he’s hardly the only maker to do that

 

[jedy617]

That might be an overstatement without additional information, but he’s hardly the only maker to do that

For sure, just strange to see here where it's not the norm when we got guys like larrin, troopah, miscard, etc etc who don't make false statements like that. And the fact that he is trying to sell D2 knives....(for the record, I think they look nice, and the price is right)

 

[blokey]

Weirder things have happened. I'm not like offended if someone has 2 accounts on a forum, not sure why wondering that is "gross" lol. Was just a guess.


For sure, just strange to see here where it's not the norm when we got guys like larrin, troopah, miscard, etc etc who don't make false statements like that. And the fact that he is trying to sell D2 knives....(for the record, I think they look nice, and the price is right)

Honestly, grouping him with OP because they are both Asian is bit unsettling for me too because I don’t want to be assumed to be someone else just im Asian, it’s a sensitive topic

Yeah they are great technical guys but most makers make over statement especially when you got to Japanese side of things…

 

[jedy617]

No. I passed no misinformation. My statements and references are contained in this thread and substantiated by @Redwax , @blokey , and the work of Larrin Thomas. Your statements are only meaningful in your head.

How many times do I have to post both of your quotes:

"made no broad claim that D2 is generally tougher than SG2" -you


However, compared to commonly used steels like VG10, AUS10, and SG2, D2 steel's edge impact resistance is not inferior -him

so uhh yeah he did pass along that wrong info, and you are saying he did not? Lol

 

[azn_knives_4l]

How many times do I have to post both of your quotes:

"made no broad claim that D2 is generally tougher than SG2"

However, compared to commonly used steels like VG10, AUS10, and SG2, D2 steel's edge impact resistance is not inferior

Lol. Why do you exclude OP's explicit statements and qualifications to HRC and heat treat??? Why so belligerent over your own confusion? It's been clarified by @Redwax , @blokey , and myself and yet you only target me with your nonsensical argumentation. You're on ignore. Have a good night.

 

[jedy617]

Lol. Why do you exclude OP's explicit statements and qualifications to HRC and heat treat??? Why so belligerent over your own confusion? It's been clarified by @Redwax , @blokey , and myself and yet you only target me with your nonsensical argumentation. You're on ignore. Have a good night.

Right, because saying harder sg2 in here is less tough, makes the information in his previous posts correct lol. Ah who cares. It's a crap steel anyway. Good night