Questions about: Prelaminated, forge-welded, HT and expectations on quality

[ModRQC]

Hello guys!

I'm not aiming to pierce the secrets of forging steel, only to realign my impressions of some aspects with reality. I'll make this simple, and will rather rely on knowledgeable replies to "open up" the discussion.

- Is a prelaminated steel forge-welded in similar ways as a maker would do it in house, or are there "other" ways? I saw a couple of videos on You Tube about the process "in house", and am wondering among other things if it can be done as an "automated" process?

- Are there "telltale signs" of a blade being prelaminated?

- Advantages/Disadvantages - for example, I seem to have gathered that forge-welding a stainless cladding, or a stainless core, is more difficult than say carbon/iron clad...

- Does it affect the range/possibility of HT to use a prelaminated blade, or is the heat treat not (necessarily) part of the equation?

- Any other considerations that make these questions look dumb because there's a big "in-between" chunk of possibilities and limitations that define the way in which those questions could be truthfully answered?

- Are there specific cases where using a prelaminated steel - or forge-welding in house - is sure to affect quality?

- And yes, the very obvious yet totally unknown to me: under what form does a maker receive a prelaminated steel?

Thank you very much!

 

[Kippington]

Objectively speaking, prelaminated steel is better than the stuff which is done in-house.

Small time makers can't compete with the specialised heavy machinery that steel mills have... plus the mills work in a market with tightly controlled parameters and high levels of quality control. The welds are done at lower temperatures - which is nicer to the steel - and likely in a controlled atmosphere. Quite frankly, the odds of inclusions and faulty welds/delaminations at the factory are much lower than something a guy in a shed can do with a hammer, but that's not to say you should always dismiss the stuff done in-house as inferior. You can think of it like a new Toyota car engine vs an engine designed and built from scratch by a small garage.

Pre-lam comes from the mill in sheets, which can also be cut into bars for sale.

Stock removal knives made from this stuff will have a noticeably 'controlled' look to them, although forging of the prelaminated steel will change the appearance into something essentially indistinguishable from something done in-house.

 

[Alder26]

As always Kippington proves to have an abundance of knowledge and aptitude for explaining things so that us lay people can understand it.

Like many things in this hobby there is a ceiling of practical benefit that you can get from traditional, smaller production, more esoteric methods. In practice, the benefits that a billet forged by the smith themselves provide have to do with provenance relating to skill, method, and ability. There is likely no difference in the ability of the knife to cut things (all other factors being equal).

However, I do see the discussion of "pre-lam" billets used as short hand in the case of some smiths that use slightly different steels in their lines of knives. TF is the main example that comes to mind. The cheapest line of knives they produced used pre-lam billets of shirogami #1, the next step up from there used in-house forged billets of shirogami #1A. In this case there was actually a difference in the steel being used, as well as the technique used to make it. This leads to confusion over the benefits of said billets being better or worse based on either technique, or the steels make up itself (i.e. people talk about pre-lam vs. in-house but the reason for the slight difference in benefit most likely comes from the difference in steels used.)

 

[Kippington]

The cheapest line of knives they produced used pre-lam billets of shirogami #1, the next step up from there used in-house forged billets of shirogami #1A. In this case there was actually a difference in the steel being used, as well as the technique used to make it.

You bring up an interesting point - the difference between shirogami #1 and shirogami #1A

The point of buying pre-laminated steel is to do away with the problems associated with in-house forge welding. One of those problems is that the very high temperatures required to successfully weld will also cause decarburization in the steel.
The whole idea of shirogami #1A is to add a little extra carbon to the original shirogami #1, which adds allowance for carbon to leave the core during the weld to end up at the same % carbon (post-weld) as the original shirogami #1.

So essentially, both knives you mentioned are designed to be the same core steel, even though the specification sheet might say otherwise.

"Shirogami 1A(Hitachi) - Special version of the Shirogami 1 steel for forgers, with slightly higher Carbon content, to compensate for the loss of the carbon during forging. Special thanks to Shinichi Watanabe for providing the info."​

- zknives​

 

[Alder26]

The whole idea of shirogami #1A is to add a little extra carbon to the original shirogami #1, which adds allowance for carbon to leave the core during the weld to end up at the same % carbon as the original shirogami #1.

This makes the discussion of whatever slight difference there may be in TF lines all the more hilarious.....and confusing hahaha. It should also be said in the case of TF that recently they have moved to using pre-lam billets for both lines with no discernible difference in steel quality.

Very interesting that steel manufacturers design specific steels for use cases that might arise in smaller scale production. I suppose also beneficial to makers that use specific cladding steels that cannot be made in a factory (i.e. damascus, wrought iron, etc.)

 

[Kippington]

Very interesting that steel manufacturers design specific steels for use cases that might arise in smaller scale production. I suppose also beneficial to makers that use specific cladding steels that cannot be made in a factory (i.e. damascus, wrought iron, etc.)

To make it even more confusing, there's a chance that Hitachi use #1A in their pre-lam billets and sell them as #1, having already predetermined the carbon loss from their factory processes. There would be nothing wrong or misleading by doing that.

But I'm only saying this as a thought experiment. It's unlikely they do it, although not impossible.

 

[MarcelNL]

I saw pieces of sanmai Shirogami 2 , and various types of Dmascus at a knife shop recently. Make your own, the thought crossed my mind for a sec...

 

[parbaked]

It should also be said in the case of TF that recently they have moved to using pre-lam billets for both lines with no discernible difference in steel quality.

You are incorrect. What TF stated is that Hitachi no longer produces Shirogami 1A, so the core steel in the Nashiji and Maboroshi are now the same
The manufacturing process is still different. They said nothing about switching to pre-laminated steel.

This makes the discussion of whatever slight difference there may be in TF lines all the more hilarious.....and confusing hahaha.

The differences between Maboroshi and Nashiji are clearly evident when you handle both knives.
Maboroshi knives are made from thicker billets and treated differently.

 

[ModRQC]

Objectively speaking, prelaminated steel is better than the stuff which is done in-house.

Small time makers can't compete with the specialised heavy machinery that steel mills have... plus the mills work in a market with tightly controlled parameters and high levels of quality control. The welds are done at lower temperatures - which is nicer to the steel - and likely in a controlled atmosphere. Quite frankly, the odds of inclusions and faulty welds/delaminations at the factory are much lower than something a guy in a shed can do with a hammer, but that's not to say you should always dismiss the stuff done in-house as inferior. You can think of it like a new Toyota car engine vs an engine designed and built from scratch by a small garage.

Pre-lam comes from the mill in sheets, which can also be cut into bars for sale.

Stock removal knives made from this stuff will have a noticeably 'controlled' look to them, although forging of the prelaminated steel will change the appearance into something essentially indistinguishable from something done in-house.

Wow... way to answer about 7 questions out of 8 seemingly answering just a couple and also making it into an insight on the whole thing and providing additional elements I wouldn't have thought about - and pictures! Thank you very much for taking some precious time to enlighten me - as I'm sure, many others.

Reading your explanation, and looking at the pic, makes me wonder that if they "machine weld" it on such a large scale, there are surely other applications than... aaah let's say blades... for the use of prelaminated steel?

 

[HSC /// Knives]

some answers based on my experience working with prelaminated and making my own with other bladesmiths. As a student of Murray Carter, I use primarily his steel which is prelam. I also buy prelam from other sources. I dont have the equipment, and at this point dont want to make the investment for making my own laminated steel, so I prefer to work with other bladesmiths at their shop making what i need.

- Is a prelaminated steel forge-welded in similar ways as a maker would do it in house, or are there "other" ways? I saw a couple of videos on You Tube about the process "in house", and am wondering among other things if it can be done as an "automated" process?

rolling mills, already answered above.

- Are there "telltale signs" of a blade being prelaminated?

not really... once it's been forged out and processed into a knife, it would be difficult to tell them apart...however special combinations of core and cladding would be a sign that it's not common and therefore not prelaminted.
One way you can sort of tell in my experience is that in-house made laminated steel tends to have the core exposed too much, (but not always)

- Advantages/Disadvantages - for example, I seem to have gathered that forge-welding a stainless cladding, or a stainless core, is more difficult than say carbon/iron clad...

advantages of prelam - known core thickness and consistency of core thickness for blade processing.
disadvantages of prelam - limited standard sizes available...general availability to makers

advantages of forge weld- ... availability of different core/cladding combinations, ability to make custom sizes...tall nakiri etc.
disadvantages of forge weld - uneven and shifted to one side core thickness depending on what machine was used to draw out the bar.

- Does it affect the range/possibility of HT to use a prelaminated blade, or is the heat treat not (necessarily) part of the equation?

not part of the equation.
however the ease of workability and processing relative to HR is definitely part of the equation for me.

- Are there specific cases where using a prelaminated steel - or forge-welding in house - is sure to affect quality?
both can have quality issues from time to time. I have rec'd 2 batches of prelam material over the last few years that delaminated on end forging.

- And yes, the very obvious yet totally unknown to me: under what form does a maker receive a prelaminated steel?

I receive them in bars of various lengths and thicknesses and widths depending on availability and what is produced.

 

[HSC /// Knives]

side note on the costs. prelaminated steel is expensive, but not costly. That is important to note.
custom forge welded steel is generally more expensive per lb than the prelam.

 

[Alder26]

You are incorrect. What TF stated is that Hitachi no longer produces Shirogami 1A, so the core steel in the Nashiji and Maboroshi are now the same
The manufacturing process is still different. They said nothing about switching to pre-laminated steel.



The differences between Maboroshi and Nashiji are clearly evident when you handle both knives.
Maboroshi knives are made from thicker billets and treated differently.

My mistake. Gaku had said that the materials were the same, but if he was referring to only core steel that makes sense.
The difference in design, finish, manufacture, etc. are obviously all different. I'm not sure if I have ever been able to tell a significant difference in heat treat between the two lines though.

 

[Kippington]

The whole idea of shirogami #1A is to add a little extra carbon to the original shirogami #1, which adds allowance for carbon to leave the core during the weld...

To help illustrate this post, I should show a picture (from this thread) that clearly shows carbon migrating out of the core steel and into the surrounding cladding. This would've mostly happened during the forge welding heat, and to a lesser extent during forging of the blade into shape (which generally happens at lower temperatures, decreasing the migration speed of the carbon).

"When forging steel at 1150 °C (2100 °F), the time to diffuse a carbon atom 0.25 mm (250 μm, or 0.01 in.) is roughly only 1 minute."​

- John D. Verhoeven, Steel Metallurgy for the Non-Metallurgist​

 

[Eloh]

That's why i believe that a lot of san mai knives have way less carbon in the core steel than the difference between shiro 1a and 1b ...

 

[dafox]

To help illustrate this post, I should show a picture (stolen from this thread) that clearly shows carbon migrating out of the core steel and into the surrounding cladding. This would've mostly happened during the forge welding heat, and to a lesser extent during forging the blade into shape (which generally happens at lower temperatures).

"When forging steel at 1150 °C (2100 °F), the time to diffuse a carbon atom 0.25 mm (250 μm, or 0.01 in.) is roughly only 1 minute."​

- John D. Verhoeven, Steel Metallurgy for the Non-Metallurgist​

Are Hiromotos AS's made from in house laminated steel or pre laminated?

 

[billyO]

prelaminated steel is better than the stuff which is done in-house.

Sorry Kip, but I'm going to have to disagree with your blanket statement above, while noting that you did provide a disclaimer.

but that's not to say you should always dismiss the stuff done in-house as inferior.

the odds of inclusions and faulty welds/delaminations at the factory are much lower than something a guy in a shed can do with a hammer,

This might be true, but it depends on the ethics of both/either party in the comparison and their attention to quality control. There are plenty of makers out there whose pattern welded steel is as good, if not better, quality than some of the mass-produced laminated stuff out there. I recently saw a site online that was advertising that their pre-made billets could reach HRC 55-56. IMO that's pretty lousy stuff. I'd get my billets to 55-56 only if I temper them at 600F.

I just don't want someone to read this thread and rule out a smaller/local maker on the assumption that what they do is of inferior quality to the mass-produced, factory stuff.

 

[HSC /// Knives]

Sorry Kip, but I'm going to have to disagree with your blanket statement above, while noting that you did provide a disclaimer.



This might be true, but it depends on the ethics of both/either party in the comparison and their attention to quality control. There are plenty of makers out there whose pattern welded steel is as good, if not better, quality than some of the mass-produced laminated stuff out there. I recently saw a site online that was advertising that their pre-made billets could reach HRC 55-56. IMO that's pretty lousy stuff.

I just don't want someone to read this thread and rule out a smaller/local maker on the assumption that what they do is of inferior quality to the mass-produced, factory stuff.

How about this- it’s better (the pre lam) for a maker who purchases their laminated steel.

a forge welded bar is most useful to the maker who made it, to complete as a knife.

 

[Eloh]

There are definately certain custom makers who do a near perfect job of forge welding (and forging for that matter) , but I think that's more the exception than the rule...

 

[ModRQC]

Are Hiromotos AS's made from in house laminated steel or pre laminated?

That's where, for all the splendid answers I got here, that it becomes hard to tell from my point of view. And I guess even metallurgists would have a hard time unless they KNOW that the process is done in house.

My questions arise from receiving a Yoshikane SKD. I found the lamination line to be so "straight", and the whole thing looking so neat, that I had an impression it was prelaminated. That and the stainless clad on low alloy steel. Could be dead wrong. It's not as if my impressions made much sense to begin with.

 

[ModRQC]

Sorry Kip, but I'm going to have to disagree with your blanket statement above, while noting that you did provide a disclaimer.



This might be true, but it depends on the ethics of both/either party in the comparison and their attention to quality control. There are plenty of makers out there whose pattern welded steel is as good, if not better, quality than some of the mass-produced laminated stuff out there. I recently saw a site online that was advertising that their pre-made billets could reach HRC 55-56. IMO that's pretty lousy stuff. I'd get my billets to 55-56 only if I temper them at 600F.

I just don't want someone to read this thread and rule out a smaller/local maker on the assumption that what they do is of inferior quality to the mass-produced, factory stuff.

So a "blanket negation" to a "blanket statement". Not sure it makes the negation truer, or even useful to begin with... What Kipp said about not dismissing in house on this basis pretty much covered your point in a simple way.

 

[RDalman]

Keep in mind smaller makers/manufacturers these days can still use machines that border to the "factory" image supplied... There are smaller scale rolling mills/presses etc that can be used in smaller settings as well. Indeed not every "bladesmith" today forges with coal and hammer. Just to throw in there. If you as customers care and want transparency, ask for it. Be it "western" or japanese.

 

[ModRQC]

Thank you sir! All info is welcomed especially from skilled makers.

To help illustrate this post, I should show a picture (from this thread) that clearly shows carbon migrating out of the core steel and into the surrounding cladding. This would've mostly happened during the forge welding heat, and to a lesser extent during forging of the blade into shape (which generally happens at lower temperatures, decreasing the migration speed of the carbon).

"When forging steel at 1150 °C (2100 °F), the time to diffuse a carbon atom 0.25 mm (250 μm, or 0.01 in.) is roughly only 1 minute."​

- John D. Verhoeven, Steel Metallurgy for the Non-Metallurgist​

So the darker grey is carbon diffusion... something we can also look at as a telltale sign of being forge-welded in house. I know carbon diffusion is not (necessarily) desirable, but also not the end of the world in the hands of someone who works it out righteously. I must admit I find the diffusion very beautiful.

 

[RDalman]

Thank you sir! All info is welcomed especially from skilled makers.



So the darker grey is carbon diffusion... something we can also look at as a telltale sign of being forge-welded in house. I know carbon diffusion is not (necessarily) desirable, but also not the end of the world in the hands of someone who works it out righteously. I must admit I find the diffusion very beautiful.

Imo it usually shows in mill prelam also. Angle of grind on the joint makes alot also, worth keeping in mind. So a very low angle grind (thin) will show it more even if it's very small diffusion area. Also like in a warikomi I'm currently working on, where the core steel inserted was round as start, the core steel geo makes the transition to be a very low angle.

 

[DanielC]

I have to disagree with the opinion that prelam is higher quality than inhouse. I think it depends on the smith like a few have mentioned.

I have spent a lot of time focusing on keeping carbon at bay with sanmai, and have employed many techniques that mimic what makers in Japan expect. You just have to watch time, temp and atmosphere to ensure this. The trick is to forgeweld at the lowest possible temps, forge at the lowest possible temps and HT using the process before to your advantage. Used in a system like many of the shops in Japan had developed over the decades, one still has pretty much the starting chemistry at the very core.

I always use Verhoeven to reference this like you have, but the example picture shown looks to have a nickle barrier between the cladding and core. Nickle barriers stop diffusion altogether. However with stainless cladding, there still appears a ghosting as if it did pull carbon, but metallurgy says it's not possible. To this day I havent peered down at that particular phenomena with my scope, but it shouldnt be due to carbon diffusion. Usually you will see the accompanying ghost in the core if the nickle barrier wasn't present.

 

[DanielC]

The use of prelam saves time and money though. I've just never been one thrilled to use someone elses billets.

Though with bigger machines you can make up for other requirements. With more force you can weld at lower temps to a degree. With O2 free environments you can weld at a oower temp as well. I'm not saying they dont have the potential to do it best, but at what point are you splitting hairs? They may save a few tenths if a millimeter in diffusion by the end, but I find the most diffusion occurring after a billet is thinner than most prelam billets any way as the speed is exponential as thickness is reduced, and it doesnt seem to really take off until you are under .125" in my experience.

 

[Beau Nidle]

I've only used a couple of bars of prelam (stainless clad super blue), and both of them delaminated on forging down tangs. I had no problems when forging out the blades, but the tangs were an issue.

 

[ModRQC]

I have to disagree with the opinion that prelam is higher quality than inhouse. I think it depends on the smith like a few have mentioned.

I have spent a lot of time focusing on keeping carbon at bay with sanmai, and have employed many techniques that mimic what makers in Japan expect. You just have to watch time, temp and atmosphere to ensure this. The trick is to forgeweld at the lowest possible temps, forge at the lowest possible temps and HT using the process before to your advantage. Used in a system like many of the shops in Japan had developed over the decades, one still has pretty much the starting chemistry at the very core.

I always use Verhoeven to reference this like you have, but the example picture shown looks to have a nickle barrier between the cladding and core. Nickle barriers stop diffusion altogether. However with stainless cladding, there still appears a ghosting as if it did pull carbon, but metallurgy says it's not possible. To this day I havent peered down at that particular phenomena with my scope, but it shouldnt be due to carbon diffusion. Usually you will see the accompanying ghost in the core if the nickle barrier wasn't present.

View attachment 98554

Good point and accompanying theory. I think @Kippington was talking "absolute" - where a tighter control and more advanced tech CAN "regulate" and repeat an outcome better.

There is also the mid-tier point that to me enters in the equation. On one hand you have prelam mills and heavy production, on the other makers like yourself who work solo/small crew and dedicate their entire knowledge and skill, knife by knife. But then the mid-tier is a lot of J-makers who don't have the heavy equipment, or cannot regulate so many parameters as the mill can, and have so high a number of units to put out that surely there are much wider variations to their stuff.

Of course, dedication is always key to the end product of forge-welding in house. Prelams - well they're just produced the same, day after day.

Does this make sense at all? I'm not trying to speak in place of Kipp or speak against your idea. Just following my inner monologue as all of what you guys said is percolating down.

 

[DanielC]

Good point and accompanying theory. I think @Kippington was talking "absolute" - where a tighter control and more advanced tech CAN "regulate" and repeat an outcome better.

There is also the mid-tier point that to me enters in the equation. On one hand you have prelam mills and heavy production, on the other makers like yourself who work solo/small crew and dedicate their entire knowledge and skill, knife by knife. But then the mid-tier is a lot of J-makers who don't have the heavy equipment, or cannot regulate so many parameters as the mill can, and have so high a number of units to put out that surely there are much wider variations to their stuff.

Of course, dedication is always key to the end product of forge-welding in house. Prelams - well they're just produced the same, day after day.

Does this make sense at all? I'm not trying to speak in place of Kipp or speak against your idea. Just following my inner monologue as all of what you guys said is percolating down.

That makes perfect sense, and he is indeed correct with that, and mentioned speaking objectively, which it is an objective opinion.

If there is a lack of diffusion barrier then all of these nuances to retain carbon can always be improved upon, but there is a range in many makers heads of what is acceptable and what isnt.

As far as diffusion is concerned, even though you are bringing the steel to a high temperature for a short period of time, the initial weld done by most that keep tight controls anyway is relatively nill. I havent seen much diffusion until the billet starts to reduce in size and each second of time at heat is that much more detrimental to the diffusion coefficient. The latter stages of forging and the HT itself in my experience have been the biggest factors in this.

Some of my first tries of stainless sanmai caught the eye of Shosui Takeda. He brought some of these things to my attention and told me that when he first switched to stainless cladding, he went through 300kg of steel before he realized he got part of their process wrong. They buy prelaminated billets and forge them to knife shape.

His pile looked just like my examples at the time, which he was surprised and that's what brought him to respond on my post (it's a rare occassion). He told me to scrap the blades and rethink part of my process. He then told me I would be a great blacksmith one day, lol. It was a good conversation and beckoned more questions, but as I've come to learn, craftsmen in Japan can be guarded, especially over the internet with western makers, but in this he was candid and enjoyed sharing his experience. He never once told me to switch to laminated billets to solve the problem though.

 

[DanielC]

I will also add that I have a lot of respect for Kipp. Its just a subject that I am very passionate about and have invested a lot of time and energy into improving.

 

[ModRQC]

Let’s state my assumption before I ask you further questions: I think that yes, between dedicated hands, with time taken to improve and control the process, I’m sure in house can come out as good than prelams. My assumption - agreement to it not worth discussing or necessary for the next part.

That being said you also include latter stages of forging and HT as most crucial. I’m sure we can all agree on that.

So in the spirit of aligning things said so far, wouldn’t the point of Kipp come out as independent of any further process: that the prelam, as sent to the maker, and in house laminating, as done to the best abilities by a good maker before any further process, will tend to match in quality at best - where indeed the prelam would take home a trophee for absolute consistency, while the apt maker would take home the trophee of matching in house such quality without as much consistency?

Or would your point rather be that the apt maker, to best abilities, would take home the trophee of surpassing quality of a prelam and do so perhaps with commendable consistency?