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     Simplified Comparison Diagrams for Stainless Steels     Material Properties Guide   

 Simplified Comparison Diagrams for Stainless Steels

This comparison diagram explains the relationships between austenitic steels (such as SUS304), ferritic steels (such as SUS430), martensitic steels (such as SUS420J2), and precipitation hardening steels (such as SUS631).

Click the name of a particular grade to see a detailed specifications page.

To see general properties for stainless steels, refer to the Material Properties Guide below.

 

Click a steel grade to learn more

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Material Properties Guide

1. Features

1.1. Steel grade chart

1.2 Differences in workability due to type of material

2. Finishes

2.1 Overview of various finishes

2.2 Surface finishes

3. Heat treatment

3.1. Annealing conditions

 

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1.1 Steel grade chart

Type

Category

Grade

Description

Austenitic

Stainless steel for springs

SUS301

(JIS G 4305)

(JIS G 4313)

SUS301 has a chromium–nickel ratio of 17–7, which is slightly lower than that of 18–8 stainless steel.

Since the material's austenitic structure is not stable, the cold rolling process will cause martensitic transformation to occur. SUS301 demonstrates the largest increase in magnetism due to work hardening of any austenitic stainless steel.

> See detailed specifications page for information on chemical composition and mechanical properties

SUS304

(JIS G 4305)

(JIS G 4313)

Often referred to as "18–8 stainless," SUS304 is a popular steel grade, and is the most commonly used austenitic stainless steel.

> See detailed specifications page for information on chemical composition and mechanical properties

SUS304L

(JIS G 4305)

SUS304L has a lower carbon content than SUS304 and provides excellent resistance to intergranular corrosion. It has low hardness and low work hardenability when annealed, making it suitable for deep drawing.

> See detailed specifications page for information on chemical composition and mechanical properties

Non-magnetic stainless steel

305M

SUS305

(JIS G 4305)

Austenitic stainless steels are typically non-magnetic when solution heat treated and magnetic when cold rolled. 305M is a non-magnetic stainless steel in which these tendencies have been reduced.

> See detailed specifications page for information on chemical composition and mechanical properties

Highly-corrosion resistant stainless steel

SUS316

(JIS G 4305)

SUS316 has higher Ni content and contains Mo, for good corrosion resistance.

It is often used for drawing applications, but due to its low carbon and high Ni content, it exhibits low hardness and work hardenability when annealed.

SUS316L

(JIS G 4305)

SUS316L has a lower carbon content and better drawability than SUS316.

Precipitation hardening

Precipitation hardening stainless steels

SUS631

(JIS G 4305)

(JIS G 4313)

Maintaining the superior properties of 18–8 stainless, SUS631 is the most common precipitation hardening stainless steel capable of being strengthened through heat treatment.

> See detailed specifications page for information on chemical composition and mechanical properties

SUS632J1

(JIS G 4313)

Although SUS631 becomes soft and can be processed in a variety of ways when solution heat treated, it requires an intermediate heat treatment to harden.

Even when solution heat treated, SUS632J1 is hard at normal temperature, and the only heat treatment subsequently required is a single precipitation hardening operation, which makes it simple to process.

> See detailed specifications page for information on chemical composition and mechanical properties

Ferritic

Ferritic stainless steel

SUS430

(JIS G 4305)

As SUS430 has a higher chromium content than 13Cr stainless steels, it provides better corrosion resistance. At the same time, it is easy to process because it does not undergo transformation when worked like other austenitic steels, and is the most widely used stainless steel grade.

High-performance ferritic stainless steel

FS-1

(Proprietary grade)

FS-1 is harder than SUS430 by far and has good formability. As it is not prone to press cracks, it can also be pressed quickly and accurately.

Martensitic

Stainless steels for blades

SUS420J2

(JIS G 4305)

(JIS G 4313)

SUS420J2 is quench hardened and then tempered to varying degrees to obtain an impressively wide range of mechanical properties. When shipped, the structure of Tokkin SUS420J2 contains completely spheroidized carbides, making it one of our more easily processed annealed-finish materials.

> See detailed specifications page for information on chemical composition and mechanical properties

RB-S

(Proprietary grade)

RB-S has an even higher carbon content than SUS420J2, giving it good quench hardening properties. It provides one of the highest levels of hardness of any stainless steel, and is used for blades and other applications.

> See detailed specifications page for information on chemical composition and mechanical properties

RB-Z

(Proprietary grade)

RB-Z features a higher carbon content than SUS420J2, and better quench hardening properties.

Moreover, it has a higher chromium content, and also contains nickel and molybdenum for significantly improved corrosion resistance.

> See detailed specifications page for information on chemical composition and mechanical properties

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1.2 Differences in workability due to type of material  

Finish

Description

Austenitic

Austenitic stainless steels with an annealed finish offer markedly lower yield strength relative to tensile strength, and have a high degree of elongation.

Austenitic stainless steels are excellent materials that are capable of withstanding a variety of complex processes. However, as they are tough and have an extremely high degree of work hardening and spring back, special considerations are required with regard to processing machinery, dies, lubrication, operating methods, and other factors.

Except for the soft materials described above, austenitic steels with a rolled finish have stronger directional properties as their strength increases. It is therefore important to select the correct orientation when processing, particularly when bending.

Precipitation hardening

Precipitation hardening stainless steels can be strengthened by heat treatment.

One such steel, SUS631, is a soft metastable austenite phase when annealed (solution heat treated), which allows it to withstand complex processes just like austenitic stainless steels.

By performing the precipitation hardening (heat treatment) process after processing, it is possible to obtain good workability and strength.

Ferritic

The mechanical properties and workability of ferritic stainless steels are approximately equivalent to those of medium carbon steels.

As products with an annealed finish are susceptible to the stretcher-strain marks seen in soft steels, it is necessary to use products with a skin-passed finish to avoid such problems.

Martensitic

Martensitic stainless steels with a low carbon content are easier to work than ferritic stainless steels. Martensitic products with a higher carbon content are hard even if given an annealed finish, making complex processing difficult.


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2.1 Overview of various finishes    

 

Finishing condition

Finish

Description

Annealed

BA (Bright Annealed)

Bright annealed after cold rolling. Materials with a BA finish are the softest, and are suited to sophisticated and complex processing.

 

Skin passed

Skin passed

Materials with a skin-passed finish are lightly rolled after annealing to create a suitable sheen and smoothness. Rolling increases hardness a little, but workability is about the same as for the BA finish. Useful in preventing the stretcher-strain marks that annealed ferritic stainless steels in particular are susceptible to.

2B (Bright)

2D (Dull)

Rolled

Rolled

(Determined by degree of rolling)

R

Uses more rolling force than a skin-passed finish to produce a deep sheen and smoothness.

 

Can provide extensive strength depending on the degree of rolling. However, higher rolling reductions result in stronger directional properties and shorter elongation, making complex processing difficult.

 

For SUS301/304/631 and other materials, degree of rolling reduction is stipulated as 1/4H, 1/2H, 3/4H, H, etc.

> SUS301/304 page (Mechanical and Physical Properties tab)

> SUS631/632J1 page (Mechanical and Physical Properties tab)

1/4H

1/2H

3/4H

H

EH

SEH

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2.2 Surface finishes

Surface finish

Description

Bright

The material is cold rolled using a roll with a sheen to create a glossy surface finish.

Dull

The material is cold rolled using a roll with a rough surface to give a matte finish.

No. 4 polish

(400 grit finish)

In most cases, material is polished with equivalent of 400-grit sandpaper. Material can be polished on one side or both sides. Workability is almost the same as for the BA finish.

No. 7 polish

(Semi-mirror finish)

Uses a finer polishing material than that used for No. 4 polish. Produces a finish with continuous buff marks.

HL

(Hairline)

Grade of polishing material used is determined by application and desired results. Produces a finish with continuous buff marks.

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3.1. Annealing conditions

Annealing

Annealing is performed for the following reasons:

 

1. To soften a material that was hardened through cold working or another process.
2. To prevent intergranular corrosion
3. Solidification of precipitate, necessary components, etc.
4. To remove magnetism caused by austenitic processing

 

 

Standard annealing conditions are indicated below.

Austenitic

1010°C–1150°C

Rapid cooling

Martensitic

750°C–850°C

Slow cooling

Ferritic

780°C–850°C

Rapid or slow cooling

 

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