三徳 牛刀 パラダイス -SANTOKU GYUTO PARADISE- (サンパラ -Sanpara-)
本刃付け研究所(日本の包丁と砥石と研ぎの考察)Honbazuke TOGI Lab for Japanese Kitchen Knives & Whetstones
包丁の鋼材「黄紙・白紙・青紙・青紙スーパー」の違いと成分・性能の進化 - Japanese Knife Steel: Understanding Kigami, Shirogami, Aogami, and Aogami Super - Composition, Performance, and Evolution -
この記事では、「黄紙 → 白紙 → 青紙 → 青紙スーパー」の進化の流れや成分変化、そして個々の鋼材の特徴や使い道をわかりやすく解説します。
🔶 黄紙 → 白紙 → 青紙 → 青紙スーパー：成分と性能の進化
・除去された成分： リン・硫黄（不純物） ・得られたメリット： 純度向上、焼入れ性の向上、切れ味の向上 ・失われた要素： 加工のしやすさ、コストの安さ
・添加された成分： 炭素量の増加 ・得られたメリット： 硬度・刃持ちの向上 ・失われた要素： 靭性の低下、研ぎやすさの低下
・添加された成分： クロム（Cr）、タングステン（W） ・得られたメリット： 耐摩耗性・焼戻し耐性の向上 ・失われた要素： 熱処理の難易度上昇
・添加された成分： 炭素・クロム・タングステンのさらなる増加 ・得られたメリット： さらに高い硬度・耐摩耗性 ・失われた要素： 脆さの増加、加工・研磨性の低下
・添加された成分： モリブデン（Mo）、バナジウム（V） ・得られたメリット： 最高クラスの刃持ち、耐摩耗性、焼戻し耐性 ・失われた要素： 非常に研ぎにくい、高価
・主な成分： C 0.8–0.9%、Mn、微量P・S ・硬度： HRC 58–60 ・特徴： 安価・扱いやすい・初心者向き ・用途： 一般的な包丁や工具 ・作りやすさ： ◎（非常に容易） ・研ぎやすさ： ◎（非常に研ぎやすい） ・耐摩耗性： △ ・靭性： ○
・主な成分： C 0.8–0.9%、不純物除去済み ・硬度： HRC 58–61 ・特徴： 粘りに富み、欠けにくく扱いやすい ・用途： 初心者向け和包丁、木工用刃物 ・作りやすさ： ◎（容易） ・研ぎやすさ： ◎（非常に研ぎやすい） ・耐摩耗性： △ ・靭性： ◎
・主な成分： C 1.0–1.1%、不純物除去済み ・硬度： HRC 60–62 ・特徴： 切れ味良く、バランスが良い ・用途： 和包丁、木工用刃物 ・作りやすさ： ○（普通） ・研ぎやすさ： ○ ・耐摩耗性： △ ・靭性： ○
・主な成分： C 1.2–1.3% ・硬度： HRC 61–63 ・特徴： 刃持ちが良いがやや脆い ・用途： 高級包丁、鑿（のみ） ・作りやすさ： △（やや難） ・研ぎやすさ： △ ・耐摩耗性： ○ ・靭性： △
・主な成分： C 1.0–1.1%、Cr、W ・硬度： HRC 62–64 ・特徴： 耐摩耗性・焼戻し耐性が高い ・用途： 高級和包丁、鉋（かんな） ・作りやすさ： △（やや難） ・研ぎやすさ： △ ・耐摩耗性： ◎ ・靭性： △
・主な成分： C 1.3–1.4%、Cr、W強化 ・硬度： HRC 63–65 ・特徴： さらに高い刃持ちと硬度 ・用途： 超高級刃物 ・作りやすさ： ×（難しい） ・研ぎやすさ： × ・耐摩耗性： ◎◎ ・靭性： ×
・主な成分： C 1.4–1.5%、Cr、W、Mo、V ・硬度： HRC 64–67 ・特徴： 最強クラスの刃持ち・耐摩耗性・焼戻し耐性 ・用途： プロ用鉋・包丁 ・作りやすさ： ××（非常に難しい） ・研ぎやすさ： ××（非常に研ぎにくい） ・耐摩耗性： ◎◎◎ ・靭性： ×
近年は日本鋼安来鋼に負けない日本製のステンレスも増えました。ステンレス刃物鋼材に関しては 「ステンレス系刃物鋼材の性能について-Performance of Stainless Steel Blade Materials-」 https://santoku-gyuto-paradise.hatenablog.com/entry/2025/06/07/020426
研ぎに関しては 「サンパラ流包丁研ぎの基本手順（見極めから仕上げ判断まで） - Sanpara-Style Knife Sharpening: From Assessment to Finishing (The Basics) -」 https://santoku-gyuto-paradise.hatenablog.com/entry/2025/06/17/180251
本文中のkigami・shirogami・aogamiはそれぞれyellow paper steel・white paper steel・blue paper steelの事で日立金属が刃物の鋼材の種類を示すのに黄・白・青の色紙を印とした事からその様に呼ばれるようになりました。それぞれに1号・2号・3号やスーパー等のグレードがあります。グレードはスーパーが一番上でaogamiのみに存在し、aogamiに3号は有りません。shirogamiは1号と2号と3号が流通しています。kigamiは現在黄紙2号のみ流通しており、kigamiと言えば黄紙2号の事です。プロの料理人になってshirogami2号を手にして仕事ができるようになると一人前として認められた証だったとの歴史があります。shirogami2号は研ぎやすさや切れ味のバランスが秀逸なため、これを基準にshirogami1号は研ぎにくいが切れ味が鋭く永切れするなどと評価することが多いです。aogamiは永切れ向き、shirogamiは切れ味研ぎやすさ重視、kigamiは家庭向けなどで分かれており、どれが一番という区分けでは有りません。
Japanese Knife Steel: Understanding Kigami, Shirogami, Aogami, and Aogami Super - Composition, Performance, and Evolution
When selecting Japanese knives, you'll often encounter steel names like "Shirogami" (white paper steel) and "Aogami" (blue paper steel). These are all part of the Yasuki Hagane (安来鋼) product line from Hitachi Metals (now Proterial Corporation).
These names originate from the colored wrapping paper used to package each steel type. Each grade has distinct compositions and characteristics, representing an evolutionary progression in performance enhancement.
Yasuki Hagane is premium blade steel developed based on traditional steelmaking techniques from Yasugi City, Shimane Prefecture, following the lineage of tamahagane production for Japanese swords. Manufactured with impurities minimized to the extreme and precisely controlled carbon content, it's considered an ideal material that allows craftsmen to fine-tune the balance of "sharpness, ease of sharpening, toughness, and durability."
This article explains the evolutionary progression from "Kigami → Shirogami → Aogami → Aogami Super," their compositional changes, and the characteristics and applications of each steel grade.
🔶 Evolution: Kigami → Shirogami → Aogami → Aogami Super - Composition and Performance Development
■ Kigami (Yellow Paper Steel)
Official Name: Kigami #2 Steel (SK steel series)
Composition (Representative values): Carbon 0.8-0.9%, Manganese 0.2-0.5%, trace impurities including phosphorus and sulfur
Characteristics: Affordable and easy to work with, suitable for beginners. Widely used in household knives and tools.
Evolution Point: By removing impurities (phosphorus, sulfur, etc.) from this base, it evolves into Shirogami steel.
■ Shirogami (White Paper Steel) - Grades #2, #1, #3
Composition: Carbon 1.0-1.1%, Manganese ~0.2%, impurities thoroughly removed
Characteristics: Sharp cutting edge with excellent forgeability. Ideal for Japanese knives. The most widely used standard type with exceptional balance of ease of sharpening and sharpness.
Composition: Carbon 1.2-1.3%, Manganese ~0.2%, minimal impurities
Characteristics: Higher hardness and edge retention than Shirogami #2, but somewhat more difficult to sharpen and tends to be more brittle.
Composition: Carbon 0.8-0.9%, Manganese ~0.2%, minimal impurities
Characteristics: Rich in toughness, chip-resistant, and easy to handle. Also suitable for beginners.
Evolution Point: Carbon content adjusted to optimize the balance of hardness, edge retention, and toughness.
■ Aogami (Blue Paper Steel) - Grades #2, #1
Composition: Carbon 1.0-1.1%, Chromium 0.3-0.5%, Tungsten 1.0-1.5%, Manganese 0.2%
Characteristics: Chromium and tungsten added to white paper steel. Strong resistance to tempering, improved wear resistance. A balanced type that achieves both sharpness and ease of sharpening.
Composition: Carbon 1.3-1.4%, Chromium 0.5-0.6%, Tungsten 1.5-2.0%, Manganese 0.2%
Characteristics: Enhanced performance version of Aogami #2. Further improved edge retention, but difficult to heat treat and can be hard and brittle.
Evolution Point: Alloy components strengthened, significantly improving edge retention, wear resistance, and tempering resistance.
■ Aogami Super (Blue Paper Super Steel)
Composition: Carbon 1.4-1.5%, Chromium 0.4-0.5%, Tungsten 2.0-2.5%, Molybdenum 0.3-0.5%, Vanadium 0.2-0.3%, Manganese 0.2%
Characteristics: Hitachi Metal's flagship premium steel. Extreme hardness and edge retention. Very hard, making it extremely difficult to sharpen. Often called the "ultimate weapon" for professional chefs.
Evolution Point: Addition of molybdenum and vanadium brings toughness, tempering resistance, and wear resistance to their ultimate levels.
■ Reference: SK Steel (Carbon Tool Steel)
SK steel (carbon tool steel) is a general steel material defined by JIS standards. While SK3, SK4, SK5, etc. exist, SK5 (formerly SK85) is mainly used for blades.
Hardness: HRC 58-62 approximately
Characteristics: Affordable and easy to sharpen but prone to rust
Applications: Carving tools, pruning shears, craft knives, etc.
✅ Performance Changes Through Steel Evolution Summary (Advantages and Disadvantages)
Removed Components: Phosphorus, sulfur (impurities)
Gained Benefits: Improved purity, better hardenability, enhanced sharpness
Lost Elements: Ease of processing, cost affordability
● Shirogami #2 → Shirogami #1
Added Components: Increased carbon content
Gained Benefits: Improved hardness and edge retention
Lost Elements: Reduced toughness, decreased ease of sharpening
● Shirogami → Aogami #2
Gained Benefits: Improved wear resistance and tempering resistance
Lost Elements: Increased heat treatment difficulty
● Aogami #2 → Aogami #1
Added Components: Further increase in carbon, chromium, and tungsten
Gained Benefits: Even higher hardness and wear resistance
Lost Elements: Increased brittleness, reduced workability and sharpenability
● Aogami #1 → Aogami Super
Added Components: Molybdenum (Mo), Vanadium (V)
Gained Benefits: Highest class edge retention, wear resistance, and tempering resistance
Lost Elements: Extremely difficult to sharpen, expensive
🔧 Performance Comparison of Each Steel (Characteristics, Applications, Ease of Use)
● Kigami #2 (Yellow Paper Steel)
Main Components: C 0.8-0.9%, Mn, trace P・S
Characteristics: Affordable, easy to handle, beginner-friendly
Applications: General knives and tools
Workability: ◎ (Very easy)
Sharpenability: ◎ (Very easy to sharpen)
● Shirogami #3 (White Paper Steel #3)
Main Components: C 0.8-0.9%, impurities removed
Characteristics: Rich in toughness, chip-resistant, easy to handle
Applications: Beginner Japanese knives, woodworking tools
Sharpenability: ◎ (Very easy to sharpen)
● Shirogami #2 (White Paper Steel #2)
Main Components: C 1.0-1.1%, impurities removed
Characteristics: Good sharpness, well-balanced
Applications: Japanese knives, woodworking tools
● Shirogami #1 (White Paper Steel #1)
Main Components: C 1.2-1.3%
Characteristics: Good edge retention but somewhat brittle
Applications: High-end knives, chisels
Workability: △ (Somewhat difficult)
● Aogami #2 (Blue Paper Steel #2)
Main Components: C 1.0-1.1%, Cr, W
Characteristics: High wear resistance and tempering resistance
Applications: Premium Japanese knives, planes
Workability: △ (Somewhat difficult)
● Aogami #1 (Blue Paper Steel #1)
Main Components: C 1.3-1.4%, enhanced Cr, W
Characteristics: Even higher edge retention and hardness
Applications: Ultra-premium blades
● Aogami Super (Blue Paper Super Steel)
Main Components: C 1.4-1.5%, Cr, W, Mo, V
Characteristics: Supreme class edge retention, wear resistance, and tempering resistance
Applications: Professional planes and knives
Workability: ×× (Very difficult)
Sharpenability: ×× (Extremely difficult to sharpen)
🔧 Knife Enthusiast Tips
Shirogami series have excellent compatibility with "Japanese whetstones." For enjoying the sharpening experience with natural stones, Shirogami #2 is recommended. Aogami series, due to their higher alloy content, respond somewhat differently to sharpening but offer superior edge retention.
Kurouchi Finish and Steel Materials
Aogami #2 and others are often given the traditional "kurouchi" (black-forged) finish, creating a distinctive appearance with character. Kurouchi is a traditional technique that covers the steel surface with an oxide film, also improving rust resistance.
Since none of these steels are stainless, they're all prone to rust. It's important to wipe them clean immediately after use and apply a light coat of oil before storage. Special attention is needed during humid seasons or in high-moisture environments.
📝 Summary and Selection Tips
🔰 Beginners and General Household Use → Kigami #2, Shirogami #3, Shirogami #2
🧑🍳 Cooking Enthusiasts and Professional-oriented → Aogami #2, Shirogami #1
👨🏭 Craftsmen and Supreme Performance Priority → Aogami #1, Aogami Super
Steel materials aren't simply "better if more expensive." The best choice depends on your intended use, sharpening skills, and usage patterns. However, there are also appeals beyond cutting performance and usability, such as Damascus patterns, surface textures, and black finishes, making the future of Japanese steel exciting.
When selecting steel, considering not just "performance" but also "sharpening enjoyment" and "maintenance characteristics" will greatly enrich your knife experience.
In recent years, Japanese-made stainless steels that rival the traditional Yasuki Hagane have also increased. For information on stainless blade steel materials, please refer to "Performance of Stainless Steel Blade Materials" and for sharpening techniques, see "Sanpara-Style Knife Sharpening: From Assessment to Finishing (The Basics)."
Note: Steel Name Explanations
The terms Kigami, Shirogami, and Aogami refer to yellow paper steel, white paper steel, and blue paper steel, respectively. These names originated from Hitachi Metals' use of yellow, white, and blue colored papers as identification markers for different blade steel types. Each has various grades including #1, #2, #3, and Super. Super is the highest grade and exists only for Aogami, while Aogami has no #3 grade. Shirogami is available in grades #1, #2, and #3. Currently, only Kigami #2 is in circulation, so "Kigami" typically refers to Kigami #2.
Historically, when professional chefs could handle Shirogami #2 in their work, it was considered proof of achieving full professional status. Due to Shirogami #2's exceptional balance of sharpenability and cutting performance, it serves as a benchmark - Shirogami #1 is evaluated as "harder to sharpen but sharper with longer edge retention" in comparison.
Generally, Aogami is oriented toward edge retention, Shirogami emphasizes sharpness and ease of sharpening, and Kigami is suited for household use. There's no absolute ranking of "best" - each serves different purposes.
I hope this blog helps someone in their knife journey.
「FZ-895 Tojiro·Pro tsubame ecoclean 三徳包丁170mm」の紹介… サンパラ流包丁研ぎの基本手順（見極めから仕上げ判断まで） -S… 包丁を研ぎ始めるにあたって必要な私の砥石選定の経緯について … ステンレス系刃物鋼材の性能について 包丁の性能を語る上で絶対… ブログ内のカテゴリータイトルの案など(ブログ構想説明) 以下は…- 包丁の選び方とレビュー - Knife Selection & Reviews - (2)
- 刃物鋼材の特性 - Blade Steel Characteristics - (2)
- 私の研ぎ遍歴-My Sharpening Story- (3)
- ニュース - News - (2)
- 私の砥石遍歴-My Whetstone Journey- (1)
- サイト案内・お知らせ - Blog Info & Updates (4)