January 18th 2006 (last update 26th Oct. '06)

Important note:

regarding the hardening, tempering and quenching of the High Carbon (HCS) and Extra Hard High Carbon Steel (XHCS)

 
I became aware today about a crucial product criteria which is important you know: the real hardening and tempering of the HCS and XHCS steel blades is only performed in the front half (lengthwise from the middle to the tip) of the blade, together with the carbon enriching. The back half (from the guard to the middle of the sword) thus is to consider quenched only.
I was told this is done for two reasons:
- the first is that while giving the blade its wanted shape using the glow, the tempering and hardening occurs meantime - (understandable) -,  and then of course the quenching that is here generated for the entire blade. The blade is also thinner in the front than towards the guards area.
- Further, and here I have to take the smith's word for it, if the entire blade was hardened, the steel structure would become brittle and a crack risk during utilization is real in this case.

The front part is thus the only one where standard steel could really been cut with without damaging the sharp edge. The used XCHS steel being still a modern hard high carbon spring steel, it remains in the sturdy, resilient class to my opinion.

 

Test of the used steels, in unprocessed state and on finished blades, to define and analyze the hardness are planned.

 

Now, about the steel compositions used and their characteristics

 

The HCS steel is:

 

Standards: AISI D6 ; W nr. 1.2436 ; JIS SKD2

Elements and composition

Iron = about 83%

Carbon = 2.05%

Chromium = 12.7 %

Manganese = 0.8%

Silicon = 0.3%

Others = 1.1%

 

High performance tool steel with high wear resistance and toughness.

Hardness approx. HB = 240

 

The stainless steel is:

 

Standards: 304 18/8

Elements and composition

Iron = about 68.67%

Carbon = 0.08%

Chromium = 19 %

Nickel = 9.25%

Manganese = 2%

Silicon = 1%

 

Widely used and oldest of the stainless steels.

Called 18/8 for its Chromium and Nickel contents.

Possesses an excellent combination of strength and corrosion resistance.

 

The used modern XHCS steel is:

 

Grade: SUP9 (spring steel)

Standard: JIS G4801; DIN 1.7176 or 55Cr3 ; chemically similar to 5160
Country: Japan
Elements and composition
Iron = 96.78% min ; 98.03% max
Carbon = 0.52% min ; 0.60% max
Chromium = 0.65% min ; 0.95 max
Manganese = 0.65% min ; 0.95 max
Silicon = 0.15% min ; 0.35% max
 

The material is used as leaf springs for locomotives - get the picture?

 

Hot forming: 1050 - 850ºC

Hot deformation: 920 - 830ºC

Normalising: 850 - 880ºC / air

Soft annealing: 640 - 680ºC / furnace

Hardening: 830-860ºC / oil

Tempering: 450 - 500ºC / air

 

Mechanical properties (additional code):

- treated for cold shearability (+S): max. 280 HB

- Soft annealed (+A): max 248 HB

- Spheroidized annealed - GKZ (+AC) max 200 HB

 

Core hardness after quenching: min 54 HRC

 

cozun@cozun.com