Special Steel Sheets & Coils
Simplified Comparison Diagrams for Special Steels Material Properties Guide
Simplified Comparison Diagrams for Special Steels
The comparison diagrams below show carbon steels such as JIS S45C and carbon tool steels such as JIS SK-5 (SK85).
Click the name of a particular grade to see a detailed specifications page.
To see general properties, refer to the Material Properties Guide below.
Carbon Steels (S**C)
Carbon Tool Steels (SK**)
Material Properties Guide
1. Features |
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2. Workability |
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3. Heat treatment |
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1.1. Steel grade chart
Type |
Grade |
Property data |
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Carbon steel (JIS G 3311) (JIS G 4051) (JIS G 4802) |
S15C S45C S50C S55C S60C |
Carbon steels have lower carbon content than carbon tool steels, and have less-strict regulations on impurities. They are used in applications that require a certain amount of strength and toughness. Carbon steels with low carbon content offer better raw-material workability, but are susceptible to uneven quenching, so care must be taken with regard to temperature management, cooling methods, and the like. Carbon steel applications include office appliances, electrical and mechanical components, springs, washers, clutch parts, Thomson blades, and bearing parts. > See detailed specifications page for information on chemical composition and mechanical properties |
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Razor steel
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TE-2 (SKS81M) |
By adjusting the chemical composition and quality control in the manufacturing process, the hardenability of razor steel can be increased. Refining the carbide enables us to improve sharpness and wear resistance. Razor steel is used for razor blades, long edged tools, high-grade knives, etc. > See detailed specifications page for information on chemical composition and mechanical properties |
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Carbon tool steel (JIS G 3311) (JIS G 4401) |
SK2 (SK120) SK4 (SK95) SK5 (SK85) SK6 (SK75) SK7 (SK65) |
Due to their workability, hardenability, product performance, affordability, and other characteristics, carbon tool steels are the most widely used cold-rolled special steel strips. Carbon tool steel is used in a wide range of fields from hard applications including blades, cutting tools, and regular tools to applications that require elasticity and toughness including regular springs, spiral springs, knitting needles, horns, measuring tapes, and washers. > See detailed specifications page for information on chemical composition and mechanical properties |
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Alloy tool steel (JIS G 4404) |
SKS2 SKS51 SKS7 |
SKS2 and SKS7 are produced by adding tungsten and chromium to high carbon steel and scattering tiny, hard complex-carbides. Due to their excellent wear resistance and high-temperature strength, they are used for cutters, hacksaws, metal band saws, and similar products. SKS51 contains nickel and chromium for increased toughness, and is used for hand saws, utility knives, and other products. |
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High cleanliness steel |
M2 (Corresponds to SK4) |
M2 is high in carbon (C), manganese (Mn), and chromium (Cr) for increased wear resistance, and low in phosphorus (P) and sulfur (S) for a high degree of cleanliness and durability. M2 has good properties for heat treatment, a high degree of cleanliness, and a well conditioned surface. It is mainly used for knitting needle parts, where a high degree of reliability is required. |
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Chromium molybdenum steel (JIS G 4105) |
SCM415 |
Chromium–molybdenum steels are typically used for structural applications. They can be quenched and tempered to provide mid-level strength and toughness. They have low hardness and good workability. Moreover, their alloy content gives them good hardenability and allows them to be quenched even if cooled at a slower rate. They are also not very susceptible to deformation. SCM415 is case hardened steel, so it is usually used after the surface has been hardened via carburization. Chromium–molybdenum steel applications include office appliances, electrical and mechanical components, Thomson blades, and chain components. |
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1.2 Finish definitions and finish chart
Tokkin uses the following finishing definitions:
Finishing condition |
Finishing rolling reduction |
Annealed |
—— (As annealed) |
Skin passed (lightly rolled) |
Up to 5% |
Rolled |
15%–40% |
Full hardened |
35% or higher |
The table below is a finish chart for various steel grades.
Grade |
Finishing condition |
Hardness test |
Tensile test |
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HV |
Tensile strength N/mm2 |
Elongation % |
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TE-2 SK-2 |
Annealed |
170–210 | 520–685 | 20–32 | |
Skin passed | 190–230 | 570–715 | 10–28 | ||
Rolled | 250–290 | 735–980 | 2–15 | ||
Full hardened | 280–320 |
835–1080 |
1–3 | ||
See also detailed specifications pages for high carbon steels and stainless steels for blades. > High carbon steels and stainless steels for blades (TE-2, SK-5, RB-S, & SUS420J2) |
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SK4 M2 |
Annealed |
160–200 |
490–645 | 24–35 | |
Skin passed | 175–215 | 540–695 | 12–32 | ||
Rolled | 245–285 | 725–970 | 2–15 | ||
Full hardened | 270–310 | 825–1040 | 1–4 | ||
See also detailed specifications pages for carbon tool steels and high cleanliness steels. > Carbon tool steels (SK2, SK4, SK6, & SK7) > High cleanliness steel (M2) |
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SK5 | Annealed | 150–190 | 460–625 | 26–37 | |
Skin passed | 170–210 | 510–685 | 15–35 | ||
Rolled | 240–280 | 725–930 | 3–16 | ||
Full hardened | 260–300 | 805–1000 | 1–5 | ||
See also detailed specifications pages for carbon tool steels and gauge steel plates. > Carbon tool steels (SK2, SK4, SK6, & SK7) > Gauge steel plates (SK5) |
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SK6 S70C |
Annealed |
145–185 | 440–615 | 27–38 | |
Skin passed | 160–200 | 490–665 | 15–35 | ||
Rolled | 235–275 | 715–920 | 3–16 | ||
Full hardened | 255–295 | 795–990 | 1–5 | ||
See also detailed specifications page for carbon tool steels. |
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SK7 S60C S55C S50C S45C S15C |
Annealed | 140–180 | 410–610 | 28–39 | |
Skin passed | 155–195 | 460–655 | 16–36 | ||
Rolled | 230–270 | 705–900 | 3–17 | ||
Full hardened | 250–290 | 775–970 | 1–5 | ||
See also detailed specifications pages for carbon tool steels and carbon steels. | |||||
SKS2 |
Annealed |
190–230 |
615–715 |
20–30 |
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Full hardened |
280–320 |
835–1080 |
1–3 |
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SKS7 |
Annealed |
200–240 |
645–735 |
20–28 |
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Full hardened |
300–340 |
880–1125 |
1–3 |
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SCM415 |
Annealed |
125–165 |
335–540 |
28–50 |
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Full hardened |
200–240 |
655–735 |
1–8 |
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Grade |
Finishing condition |
Hardness test |
Tensile test |
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HV |
Tensile strength N/mm2 |
Elongation % |
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2.1 Bending
1. While a rolled finish is sometimes used for bent products, we normally use an annealed or skin-passed finish for such products.
2. Steel strips generally have directional properties. As products with a rolled finish in particular have strong directional properties, it is better to avoid bending parallel to the rolling direction. It is therefore necessary to think of a layout that will ensure that the bending direction is perpendicular or cross to the rolling direction.
3. After cutting, shearing, or processing, if a bend is made so that the burred surface is on the outer face of the bent section, cracks may propagate from the burred edge. Therefore, the burred surface should be positioned so that it is on a section that will not be bent, or the burrs should be removed before bending.
4. When bending, spring back differs according to the extent of processing and finish of the material. It is necessary to make appropriate corrections depending on the shape and processing method.
5. Bendability differs according to grade and processing conditions, but it is possible to process materials with different finishing conditions as shown below.
(These conditions mainly apply to low carbon steel strips of grade SK5 or below)
Finishing condition |
Thickness of under 1 mm |
Thickness of 1 mm or greater |
Annealed |
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Skin passed |
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Rolled |
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Note: t = thickness, R = internal bend radius
Reference: Approximation of bending power
V-shaped die |
P = 0.6bt2σB/L |
U-shaped die |
P = 0.6bt2σB (1 + t/L) |
Note: t = thickness, b = width, L = width of die channel, σB = tensile strength of material
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2.2 Drawing
- Except for minor drawing processes, the product usually needs to have the same drawability for all directions. For this reason, products with an annealed or skin-pass finish are used.
- Even though cold rolled special steel strips are not susceptible to significant stretcher-strain marks in the way that soft steels are, they have a low drawing limit. Therefore, when deep drawing, we perform intermediate annealing, and then re-draw the product.
We use a drawing rate of 0.4 for drawing a regular flat sheet and 0.6 for re-drawing.
Drawing rate = d/D
d = diameter of product to be drawn, D = diameter of circular plate before drawing
Reference: Formula for approximate calculation of drawing power
P = ndtσBm
Note: t = thickness, m = correction factor (normally 0.4–1.0), σB = tensile strength of material
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3.1. Precautions regarding heat treatment
Almost all cold rolled special steel strips are quenched and tempered as appropriate depending on the application.
The most important considerations when performing these heat treatment processes are:
(1) to heat and cool the product evenly using suitable conditions,
(2) to prevent decarburization, scaling, and high temperature corrosion as much as possible, and
(3) to choose a quenching method that will minimize quenching deformation.
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3.2 Temperature of furnace and material
When performing heat treatment, the temperature of the heat treatment furnace is measured and used as the temperature to which the material is heated. However, sometimes there may be a large difference or variation between the material’s actual temperature and the measured furnace temperature. It is therefore necessary to thoroughly investigate temperature properties, and control the temperature and alter the heat treatment process accordingly.
3.3 Pre-treatment and atmosphere
When treating cold rolled special steel strips, the higher the carbon content, the easier decarburization occurs. In particular, the risk becomes greater in in high-temperature heating processes like quenching. If the material is contaminated with dirt or foreign substances then high temperature corrosion may occur. Therefore it is necessary to pre-treat material surfaces by cleaning them and adjust the atmosphere of the furnace before heat treatment. RX gas is used as a standard furnace atmosphere during quenching, NX gas during tempering, but N2, H2, AX gases, and others are also used. In some cases, neutral salt-bath furnaces, metal bath furnaces, furnace tubes, cases, and other equipment is used to ensure that the material does not come into direct contact with the air.
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3.4 Quenching
In most cases, a value around the midpoint of the quenching temperature range in the table above is used as the quenching temperature. This temperature is maintained for anywhere from several tens of seconds to several minutes depending on the material grade, dimensions, shape, required properties, and quenching method. Quenching conditions have a significant influence on the properties of the product. If the quenching temperature is too high or is maintained for too long, grains become larger, toughness is reduced, and the risk of decarburization increases. On the other hand, if the quenching temperature is too low or is not maintained for long enough, the product does not harden and soft spots may occur. It is therefore important to select appropriate quenching conditions.
Normally oil or water is used to cool materials down. Water-quenched products harden better than products oil-quenched products, but are more susceptible to problems such as quenching deformation and cracking. For this reason, except in some special cases, oil quenching is used for cold-rolled special steel strips.
To avoid quenching deformation, the oil temperature is increased and martempering is performed. In special cases, quenching is performed in a salt bath or metal bath (austempering). For ribbon shapes or simple shapes, stool quenching, press quenching, and other methods are employed.
Grade |
Quenching temperature (°C) |
TE-2 |
790–850 oil quenching (760–820 water quenching) |
SK4 |
790–850 oil quenching (760–820 water quenching) |
SK5 |
790–850 oil quenching (760–820 water quenching) |
SK6 |
790–850 oil quenching (760–820 water quenching) |
SK7 |
790–850 oil quenching (760–820 water quenching) |
SKS51 |
790–850 oil quenching (760–820 water quenching) |
SKS2 |
830–880 oil quenching |
SKS7 |
830–880 oil quenching |
S70C |
790–850 oil quenching |
S60C |
800–860 water quenching |
S55C |
800–860 water quenching |
S45C |
800–850 water quenching |
S15C |
800–860 water quenching |
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3.5 Tempering
In spite of their hardness, quenched materials lack toughness and are brittle. To be finished into materials that possess toughness and strength, they must therefore must be tempered. Tempering conditions are determined depending on the required properties of each material by considering test results, the steel grade's quenching and tempering properties, and other factors. For cold-rolled special steel strips, long tempering time is used for certain cases (particularly when toughness is required) because the amount of material used is small and tempering work is often carried out consecutively. However, it would seem that most manufacturers often use a short tempering time of no longer than a few minutes. Moreover, due to the nature of the consecutive tempering process, if time is short then the temperature is set a little higher and products are tempered repeatedly. However, as a general rule, materials that are tempered at low temperature for a long time have more toughness than those that are tempered at high temperature. Care is therefore taken to avoid making the tempering furnace shorter, the tempering temperature higher, and the tempering time shorter than necessary. Using an oil, metal, or salt bath for tempering makes it possible to reduce time compared to open-air tempering. Quenching and tempering properties for common steel grades are shown in the graphs below.