Why are some tool steels laminated and others not?

[sethwm]

Just curious. You see super blue and hap40 laminated with sus410. Steels like k390 and m4 aren’t. Is this an aesthetic choice? Or is there a reason some steels must be laminated and others not?

[Wartstein]

Not an expert at all.

- But I think if a steel is laminated, perhaps that limits what kind of heat treat can be done due to the properties of the "outer" laminate steel ( I seem to recall that HAP40 is run a bit softer than REX 45, despite they are pretty much the same steels, but HAP 40 is laminated with SUS 410)

- From an aesthetic point of view: I very much like patinas, and on a NON laminated tool steel the whole blade develops one, not only a narrow part above the apex.

[kennethsime]

Also no expert here, but I’ll add: Hitachi likes to laminate stuff.

[Bemo]

You could make an argument that the laminating increases toughness and improves corrosion resistance. ZDP, Hap40, V-toku are all laminated with stainless steels. Honestly that's not why I lie them. To me it just looks cool. I love how my Stretch in laminated V-toku has a patina just on the edge.

[vandelay]

I'd imagine the reason is that K390 and M4 are typically sold for industrial applications so the steel suppliers don't offer laminated stock

[p_atrick]

Also not an expert. There is a tradition in Japanese cutlery called san mai (cue the Cold Steel lawyers), which is why you tend to see laminated steels in Japanese steels. But Spyderco had a S90V/CPM154 laminated Manix (I think I got those details correct).

[Danke]

This limited-edition Sprint Run combines the proven features and benefits of the popular Delica 4 Lightweight with a laminated blade crafted from HAP40 and SUS410 steels. The center layer of the full-flat-ground blade is made from HAP40—an advanced high-speed tool steel produced by the powder metallurgy process. HAP40’s generous amounts of tungsten, molybdenum, vanadium, and cobalt give it exceptional toughness and high abrasion resistance, both ideal properties in a high-performance blade steel. The HAP40 core is sandwiched between layers of SUS410—a martensitic stainless steel that provide increased strength and improved corrosion resistance.

[Matus]

Laminated steel has advantages in production and user maintenace especially with larger knvies (read - kitchen knvies). Also - it is easier to bend (because the lamination is usually asutenitic stainless that does not harden and deforms plastically rather easily) - that is not necessary an advantage with pocket knvies (not only in use but also in production), although I do not recall discussions on people bending their laminated Spyderco knives, so this may not be an actuall issue or a weak point.

[Hopsbreath]

Just to throw more confusion to the mix, superblue has been released unlaminated as well. ZDP-189 is available both laminated and unlaminated also. Even VG-10 is laminated sometimes. I’ve used them all without noticing a difference.

[DavidNM]

This is an excellent question! I would love to know the answer. Hopefully an expert will chime in!

[Bemo]

I think Danke quoted the definitive source.

[Danke]

I think Danke quoted the definitive source.

Yeah hard to argue with the mothership.

[Wartstein]

All good points, but I understood the question of the op not like "why are some (tool-) steels laminated" but rather like "why are some NOT laminated (since lamination brings the mentioned advantages)".

IF this was the question, I still think lamination might limit what heat treat can be done , is more complex in production and might not be desired aestheticwise by some, since lamination steels like SUS 410 tend to scratch up easily (which I personally like).

[GarageBoy]

Does the zdp/hap40 come laminated from Hitachi, or is it done by a processor like takefu ?

[ovgcguy]

I am also interested in the answer. I am really enjoying CruWear, but for constant EDC it gets rust spots even though I silicone treat it and pay close attention in terms of water, sweat, caustics, and FM (food/adhesive/etc) remaining on the blade for any period of time.

assuming its possible, any non-stainless becomes better when laminated in stainless, IMO.

[Larrin]

All of the laminated steels were made by Takefu, they are a hot rolling and laminating company and make relatively affordable laminated steels. They use their own steels in addition to Hitachi grades. No comparable company exists in Europe or the USA, which is why steels like K390 or CPM-CruWear aren’t laminated. The one exception was the CPM-154/S90V laminate (made in the US) which seems to have been a one-off.

[Wartstein]

All of the laminated steels were made by Takefu...

Larrin, is it true that one disadvantage of laminated steels can be that the "outer" steel limits what kind of heat treatment can be done?

I seem to recall that they say that its SUS410 cladding steel is the reason why HAP 40 (laminated) can't be run as hard as REX45 (not laminated), despite the two are pretty much the same steel?

[Larrin]

All of the laminated steels were made by Takefu...

Larrin, is it true that one disadvantage of laminated steels can be that the "outer" steel limits what kind of heat treatment can be done?

I seem to recall that they say that its SUS410 cladding steel is the reason why HAP 40 (laminated) can't be run as hard as REX45 (not laminated), despite the two are pretty much the same steel?

I don’t know what limits they are setting for themselves but steels like 410 and 420 can’t be heated near as hot as those high speed steels without the grain being blown up to astronomical proportions.

[Wartstein]

All of the laminated steels were made by Takefu...

Larrin, is it true that one disadvantage of laminated steels can be that the "outer" steel limits what kind of heat treatment can be done?

I seem to recall that they say that its SUS410 cladding steel is the reason why HAP 40 (laminated) can't be run as hard as REX45 (not laminated), despite the two are pretty much the same steel?

I don’t know what limits they are setting for themselves but steels like 410 and 420 can’t be heated near as hot as those high speed steels without the grain being blown up to astronomical proportions.

Thanks, Larrin!

Now since I assume that the heat treat is done after, not before the cladding (so with the already "sandwiched" blade/steel) this would mean indeed that there are more options for heat treating REX 45 (higher temperatures) than for SUS410/HAP 40... just how a layman sees it.

[Larrin]

Now since I assume that the heat treat is done after, not before the cladding (so with the already "sandwiched" blade/steel) this would mean indeed that there are more options for heat treating REX 45 (higher temperatures) than for SUS410/HAP 40... just how a layman sees it.

It's not possible to heat treat the steel before laminating because the laminating occurs at high temperature so it would wipe out any prior heat treatment.