Stainless Steels
Precipitation Hardening
SUS631 (17-7PH) | Precipitation Hardening Stainless Steel
Overview & Features
From the softest solution-treated to the hardest full hard rolled, depending on the processing and application, it is possible to have a strength second only to high-carbon martensitic quenched materials by applying various heat treatments.
In the solution heat-treated state, more than 30% elongation allows for strong processing such as drawing.
Please note that the material is weakly magnetic in the solution heat-treated state, but becomes quite strongly magnetic after precipitation hardening treatment.
This material is hard to obtain due to its relatively small distribution volume, and most of the materials distributed in stock sales are 3/4H finish. However, we can provide from the softest material in solution heat-treated condition (A material) to the hardest material with full hard finish (EH) per your use and processing method in small lot.
TOKKIN supplies a variety of stainless steels for springs as specified in JIS G4313.
Please refer to this page for the features and comparison of each grade of stainless steel for springs.
Examples of Applications
Diaphragms, Reed Valves, CPU/GPU Springs, Tire Mold Side Blades, Chains, Dental Equipment, Springs
Available Shapes
Manufacturable Range (COIL, SHEET)
Thickness
0.030-3.0mm
Width
3.0-300mm
Length
COIL or SHEET less than 2000mm
This is the manufacturing range of coils and sheets we manufacture.
For inquiries regarding procurement items, please contact us.
Standards
We manufacture in accordance with JIS G4313 standards.
Overseas standards are listed as equivalent or similar to our materials, so please use them as a reference.
JIS
SUS631 (G4305, G4313)
UNS
S17700
AISI/ASTM
631
EN
1.4568
ISO
X7CrNiAl17-7
Chemical Composition
Physical Properties
Density
7.81 g/cm³
Specific Heat
420 J/(kg・K)
Electrical Resistivity
79 μΩ・cm
Young's Modulus
200 GPa
Thermal Expansion
15.3×10-6/K（0～100℃）
Thermal Conductivity
16.3 W/(m・K)
Melting Range
1414-1447 ℃
Magnetism
It is weakly magnetic in the solution heat-treated state, but becomes quite strong after precipitation hardening treatment.
Mechanical Properties
Unless otherwise specified, we manufacture in accordance with JIS standards (table below), but you can also specify stricter standards or custom specifications.
The mechanical properties of C materials and materials after CH treatment are shown in the figure below.
Heat Treatment
Age hardening(Precipitation Hardening) can be performed on SUS631 after precipitation hardening.
*Typical steel grades that precipitation hardened are stainless steels in the 600 series (SUS631, SUS632J2, TOKKIN 350, etc.) as well as maraging steels.
The method of precipitation hardening of SUS631 is shown in the figure below.
■TH1050、RH950 Treatmen
It is hardened by repeating two types of heat treatments. The first, T and R treatments are primary hardening heat treatments to martensitize the metastable austenite phase A material, like quenching in steel, while the second, H treatment is for complete hardening by causing precipitation hardening, the most distinctive feature of this steel grade.
*Precipitation hardening is not possible even if only H treatment is performed in the solid solution state (A material).
■CH(900) Treatment
Instead of martensitization by heat treatment, cold working is used for hardening. We provide cold-rolled C-materials with appropriate hardness, so customers only need to perform one more precipitation hardening heat treatment.
＜Note＞
・The numbers TH1050, RH950, and CH(900) represent the precipitation hardening treatment temperature in degrees Fahrenheit.
・We can provide A and C materials.
(Customers are requested to perform the hardening heat treatment of TH and RH.)
・Please refer to this article for more information on heat treatment.
Corrosion Resistance
The corrosion resistance of precipitation hardened stainless steels is generally inferior to that of austenitic stainless steels.
(Superior) Austenitic > Precipitation hardening > Ferritic > Martensitic (Inferior)
*It depends on the temper and environment, so please consult us first if you have specific issues.
Related Pages
Stainless Steels for Springs
This materials are possible to increase their hardness by rolling, they can be used as spring parts.
Precipitation Hardening Stainless Steels
These grades were developed with the concept of steels that are easy to form like austenitic stainless steels, and provide high strength like that of martensitic stainless steels.
Stainless Steels Foils (Under t0.10mm)
We offer not only thin stainless steel foils, but also propose the appropriate steel grade and temper depending on specific application and use requirements, such as strength, workablility, magnetism, and corrosion resistance.