What is the difference between SWP-A and SWP-B?

You are asking about SWP (piano wire), right?

JISG3522 (piano wire) is available in three types, SWP-A type, B type, and V type, and the tensile strength, winding property, twisting property, bendability, flaw, surface condition, etc. are standardized.

In terms of applications, Class V is used for springs with high repetition rates, especially for various valve springs such as in automobiles and ships.

Class A and B are used for important parts such as automobile clutch springs and brake springs, as well as high-grade springs such as measuring instrument springs and exercise equipments.

Class A also has a fairly high maximum allowable stress, and has favorable characteristics for fatigue against repeated loading.
Class B is suitable for springs that require high tensile strength and sag resistance by design, but it is slightly inferior to Class A in terms of toughness, which is a problem in severe molding.

Also, it is said that the spring constant is different due to the material change, but it is possible if you select a material with a different lateral elastic modulus (G), which is a calculation element of the spring constant.
For example, SWP-A and SUS304WPB (stainless steel).

Dear Spring Newbie,
The density, modulus of elasticity and Poisson’s ratio of SUS304-WPB are as follows.
8.0[g/cm^3] / 186000[N/mm^2] / 0.30

・Shear strength varies depending on the wire diameter. It is also stated in JIS B2704.
・Yield strength is not specified in JIS G 4314.
・Tensile strength is described in JIS G4314, but it depends on the wire diameter as well as shear strength.
・Regarding the thermal conductivity and specific heat capacity, the data of SUS304-WPB is unknown, but the values of SUS304: 16.3 W/m・K・0.50 J/g・K is taken into consideration here.
・For the coefficient of thermal expansion, the data for SUS304-WPB is unknown, but the values of SUS304 at 0-100°C = 17.3 × 10^-6/°C is taken into consideration here too!

Dear Spring Newbie,
SWP-C is not in JIS standard, so the mechanical properties will be the standard of the material manufacturer!
There is detailed information of SWP-C’s tensile strength from here: JFE Techno Wire Co., Ltd.

The yield strength (yield stress) of SWP-A and SWP-B is not specified in JIS standard, but it is estimated that it is about 90% of the tensile strength.

Regarding analysis (depending on the material lot), I think that it depends on the content of the analysis, but if the stress analysis at room temperature is possible, the generated stress might be analyzed by the elastic modulus and Poisson’s ratio?
If the yield strength is taken into account when evaluating the stress, it seems certain that the material will actually be subjected to a tensile test.
In this case, you may want to check the mill test report.

Thank you for your inquiry!

Thank you for your inquiry, Spring Newbie! !
SUP2 and SWP-A have different chemical components. Therefore, different materials will be used. If you have a question about durability, it can be confirmed by comparing the mechanical properties of SUP2 and SWP-A, but in theory, it is thought that SWP-A has higher durability.
Spring steel type 2 (SUP2) C: 0.60-0.75; Si: 0.15-0.35, Mn: 0.30-0.60; S: 0.035 or less; P: 0.035 or less
Tensile strength: 1128 N/mm^2 or more
SWP-A (typical: SWRS82A) C: 0.80-0.85; Si: 0.12-0.32; Mn: 0.30-0.60; S: 0.025 or less; P: 0.025 or less
Tensile strength: 1420-1570 N/mm^2 (wire diameter φ10)
Once again, thank you for your inquiry! !

Dear Allah Razi,

Thank you for your question.

Tensile strength is used to determine the dynamic fatigue life of a spring. JIS (Japanese Industrial Standards) defines the standard hardness range (tensile strength range) that satisfies the optimum mechanical properties after the spring materials go through the optimum heat treatment and processing stages.

Stress is used to determine the static usable range of a spring. As for stress, based on the differences in the components of the materials and mechanical properties, the allowable stress is defined as the elastic limit of the material.
Therefore, we need to select the suitable material and try to maintain the desired spring properties with the stress that matches with that material.

If you have any other questions, please let us know anytime.

Dear ROOKIE01,

Thank you for your question!
SUS304WPB is more expensive and the unit price is about twice that of SWP. ( and SUS316 is even more expensive)
However, if the wire diameter becomes smaller, the difference between the price of SWP and SUS304WPB seems to be smaller.

Best regards,

Dear ROOKIE01,

Thank you very much for your question!
Since they are not materials for springs, we have never dealt with them and therefore we do not know the actual performance or cost of these materials.

For more information about ZAM, please check the below link.
https://www-zam.nipponsteel.com/en/

We hope it helps.

Best regards,
Tokai Spring’s Support Team

Thank you for your question!
Please find below the chemical compositions of SUS316 for your reference.

C: Less than 0.08%
Si: Less than 1%
Mn: Less than 2%
P: Less than 0.045%
S: Less than 0.03%
Ni: 10-14%
Cr: 16-18%
Mo: 2-3%

Best regards.
Tokai Spring’s Support Team

Dear Vetrov,

Thank you for your question!
As per JIS B 2704 – 1994, the temperature limit of piano wire (SWP-A) can be up to 130℃.
However, with springs, we would recommend a maximum temperature of less than 100℃.

If you have any other questions, please let us know anytime!

Best regards,
Tokai Spring’s Support Team