Yellow Steel #2 - High Carbon Steel

Often we see discussion about carbon steels like White Steel and Blue Steel, especially their #2 variants - we have blogs on those topics too, for example. However, there is one more kind of #2 steel that is often overlooked. This blog will discuss Yellow Steel #2, where it’s used, its qualities and specialties of being inexpensive and easy to sharpen and maintain.

Yellow Steel #2 (Kigami 2) - An inexpensive High Carbon steel

Yellow Steel (Kigami) is a material commonly used in tough environments such as culinary schools and fish processing facilities. Made popular thanks to Hitachi Metals, a renowned kitchen knife steel manufacturer, this steel remains well-known and useful due to its price point, and just how easy it is to sharpen.


Steel Mapping Comparison

Steel material is crucial for indicating a knife's initial performance (amongst many other things related to craftsman ability and more). Below are some comparisons to give you some understanding showing what a particular step of the process does in terms of impacting sharpness, balance and maintainability.

Steel Material Heat Treatment/Forging Edge Sharpening Handle Attachment

Sharpness

Balance

Maintainability

Steel Material Heat + Forging Making Edges Handle Attach.

Sharp.

Bal.

Maint.

There’s three key pointers in the above chart to focus on.

  • Steel Material has a large impact on sharpness and maintainability (ease of sharpening and resistance to rust).

  • Apart from sharpness, heat treatment and the sharpening process in knife creation also have a large impact on sharpness.

  • Measuring a knife’s strengths is more than just its sharpness. Balance and maintainability also need to be considered.

Based on the above steel mapping chart, Yellow Steel #2 falls in this position on the graph below

Japanese Knife Steel Chart - Yellow Steel #2 (Kigami 2)

Despite Yellow Steel #2 being one of the cheaper metals to produce in Japan (thus making the knives cheaper to purchase), manufacturers who have been making knives using this steel for a long time have generally invested serious effort and funding into production processes specifically around this steel. Due to these efforts and appropriate quality control, Yellow Steel #2 knives are still popular today, and regarded as easy to sharpen and cheaper in comparison to other steels although they are prone to chipping.

A sharp cut and inexpensive price at the cost of brittleness


Composition Comparison

Let’s look at the tables below and explore the composition of Yellow Steel #2 more deeply. Pay attention closely to the Major Materials tab here:

Manufacturer Steel Name Carbon Silicon Cobalt Phosphorus Sulfur Manganese

Effect of Material

Hardness

Hardness (⅒ of Carbon)
Oxygen Removal

Decarburization Prevention
Toughness
Wear Resistance

Embrittlement

Embrittlement

Sulfur Removal
Toughness

Listed Value

Average

Maximum

Average

Maximum

Maximum

Average

Hitachi Metals

Yellow Steel #2

1.1

0.15

0.03

0.006

0.25

Hitachi Metals

White Steel #3

0.9

0.2

0.025

0.004

0.25

Takefu Special Steel

White Steel #2

1

Undisclosed

Undisclosed

Undisclosed

Undisclosed

Hitachi Metals

White Steel #2

1.1

0.15

0.025

0.004

0.25

Hitachi Metals

White Steel #1

1.3

0.15

0.025

0.004

0.25

Hitachi Metals

Blue Steel #2

1.1

0.15

0.025

0.004

0.25

Hitachi Metals

Blue Steel #1

1.3

0.15

0.025

0.004

0.25

Hitachi Metals

Blue Steel Super

1.45

0.15

0.025

0.004

0.25

JIS Standard

SK4

0.95

0.2

0.03

0.03

0.25

Hitachi Metals x Masahiro

ZCD-U

1.05

Undisclosed

Undisclosed

Undisclosed

Undisclosed

Manufacturer Steel Name Molybdenum Vanadium Nickel Tungsten Copper Chromium Hardness Rockwell Counter (HRC)

Effect of Material

Wear Resistance
Anti-Corrosion
Toughness

Wear Resistance
Decarburization Prevention

Toughness

Wear Resistance

Antibacterial Effects
Embrittlement

Anti-Corrosion

Changes in the quenching process

Listed Value

Average

Average

Average

Average

Maximum

Average

Hitachi Metals

Yellow Steel #2

56

Hitachi Metals

White Steel #3

55

Takefu Special Steel

White Steel #2

1

0.3

60

Hitachi Metals

White Steel #2

61

Hitachi Metals

White Steel #1

66

Hitachi Metals

Blue Steel #2

1.25

0.35

61

Hitachi Metals

Blue Steel #1

1.75

0.4

65

Hitachi Metals

Blue Steel Super

0.4

2.25

0.35

67

JIS Standard

SK4

0.25

0.3

55

Hitachi Metals x Masahiro

ZCD-U

Contains

Contains

59

Maker Steel Name Carbon Silicon Cobalt

Effect

Hard.

Hard. (⅒ Carbon)
Oxygen Rem.

Decarb Pvnt.
Tough.
Wear Res.

Listed Value

Average

Max

Average

Hitachi Metals

Yellow Steel #2

1.1

0.15

Hitachi Metals

White Steel #3

0.9

0.2

Takefu Special Steel

White Steel #2

1

Not Stated

Hitachi Metals

White Steel #2

1.1

0.15

Hitachi Metals

White Steel #1

1.3

0.15

Hitachi Metals

Blue Steel #2

1.1

0.15

Hitachi Metals

Blue Steel #1

1.3

0.15

Hitachi Metals

Blue Steel Super

1.45

0.15

JIS Std.

SK4

0.95

0.2

Hitachi Metals x Masa-
hiro

ZCD-U

1.05

Not Stated

Maker Steel Name Phos. Sulfur Mang.

Effect

Embrittlement

Embrittlement

Sulfur Rmvl.
Tough.

Listed Value

Max

Max

Average

Hitachi Metals

Yellow Steel #2

0.03

0.006

0.25

Hitachi Metals

White Steel #3

0.025

0.004

0.25

Takefu Special Steel

White Steel #2

Not Stated

Not Stated

Not Stated

Hitachi Metals

White Steel #2

0.025

0.004

0.25

Hitachi Metals

White Steel #1

0.025

0.004

0.25

Hitachi Metals

Blue Steel #2

0.025

0.004

0.25

Hitachi Metals

Blue Steel #1

0.025

0.004

0.25

Hitachi Metals

Blue Steel Super

0.025

0.004

0.25

JIS Std.

SK4

0.03

0.03

0.25

Hitachi Metals x Masa-
hiro

ZCD-U

Not Stated

Not Stated

Not Stated

Maker Steel Name Molyb. Vanad. Nickel

Effect

Wear Res.
Anti-Corrosion
Tough.

Wear Res.
Decarb Pvnt.

Tough.

Listed Value

Average

Average

Average

Hitachi Metals

Yellow Steel #2

Hitachi Metals

White Steel #3

Takefu Special Steel

White Steel #2

1

Hitachi Metals

White Steel #2

Hitachi Metals

White Steel #1

Hitachi Metals

Blue Steel #2

Hitachi Metals

Blue Steel #1

Hitachi Metals

Blue Steel Super

0.4

JIS Std.

SK4

Hitachi Metals x Masa-
hiro

ZCD-U

Has

Maker Steel Name Tung. Copper Chrom.

Effect

Wear Res.

Antibac.
Embrittlement

Anti-Corrosion

Listed Value

Average

Max

Average

Hitachi Metals

Yellow Steel #2

Hitachi Metals

White Steel #3

Takefu Special Steel

White Steel #2

0.3

Hitachi Metals

White Steel #2

Hitachi Metals

White Steel #1

Hitachi Metals

Blue Steel #2

1.25

0.35

Hitachi Metals

Blue Steel #1

1.75

0.4

Hitachi Metals

Blue Steel Super

2.25

0.35

JIS Std.

SK4

0.3

Hitachi Metals x Masa-
hiro

ZCD-U

Has

When compared to the popular White Steel #2 also made by Hitachi Metals, we see a higher concentration of materials like phosphorus and sulfur, which can contribute to brittleness so these knives must be handled with care.

An interesting point is that the carbon content of Yellow Steel #2 is still approximately 1.1 (or above.) This actually puts the steel’s hardness (sharpness) as comparable to White Steel #2 and Blue Steel #2 despite the reduced HRC - indicating that it isn’t lacking in the sharpness department and will still cut well.


Buying a Yellow Steel #2 Knife

Making of Japanese Knife

Firstly, much like any carbon steel knife, Yellow Steel knives are subject to rusting. As this is a carbon steel knife as well it almost goes without saying, but once you finish using the knife, immediately wash it with detergent and dry it very well. This is absolutely crucial for adding longevity to any carbon steel kitchen knife, and ultimately all kitchen knives in general.

Due to the brittleness from phosphorus and sulfur as mentioned earlier, knives using this steel at first can be very susceptible to chipping from tasks like cutting into materials it's not meant to (such as frozen foods or bone,) using the wrong chopping boards or even dropping the knife - so be sure to use it safely.

This is because attempting to ensure a thorough heat treatment throughout the core of the steel leads to excessive and drastic temperature variations on the surface side of the knife. If you do chip the knife though, don’t worry! Sharpening the knife after such a chip can reveal a shockingly good edge, rendering the knife useful for an extended period of time even if the shape or blade form have been modified.

And remember, these knives are easy to sharpen and inexpensive - so they can be good for someone who wants to experience the sharpness that Japanese kitchen knives possess before investing into something more long lasting. Getting the right whetstones will be important in order to maintain the knife well after usage, though. We have a blog all about whetstones to help you find the right ones.


Conclusion

Let’s recap the three key points related to Yellow Steel #2

  • Yellow Steel is used in applications where knives are used extensively in tough environments (like schools and factories), requiring frequent sharpening.

  • The carbon content is similar to White and Blue Steel #2.

  • The surface is prone to chipping, but after the first sharpening, a reliable and sharp edge lies underneath.

You may notice that we don’t sell Yellow Steel knives online. We do carry them in-store however, so please contact us if you are interested and we can tell you what our range is.