Nice to meet you. I have a question.
Normally, spring steels (SUP10, etc.) are used within the elastic range, but for some reason, we are thinking of using the material is its plastic range. Therefore, yield strength and tensile strength are required when modeling stress-strain curves. Although the minimum values of yield strength and tensile strength of spring steels are stated in the JIS, it seems that there is a big difference compared to the actual tensile test results.
So, if you have statistical data on the yield strength and tensile strength of spring steels, would you please share it with us? We only need to know the average value and standard deviation, but since the yield strength and tensile strength are listed on the spring steel’s mill sheets, I think that there is always statistical data (I’m not sure if I am right though…)
Thank you for writing to us, Mr. Guchi!
Yield strength and tensile strength vary depending on the heat treatment temperatures, materials, product shapes, and wire diameters. The tensile strength and yield strength stated in the mill sheets (certificate issued by the material manufacturer) obtained by heat-treating the test piece along with values in the statistical data, and the values of the actual products may differ.
In order to obtain accurate yield strength and tensile strength, I think that the product should be heat-treated under the heat treatment conditions used when manufacturing the actual product, and then yield strength and tensile strength can be measured after that!
Thank you for your prompt response.
We are investigating how much variation there is rather than finding the accurate values of yield strength and tensile strength. I think that they are calculated by using the test piece (JIS test piece), but is there any data that shows the variation in the tensile test results of the test piece by heat treatment temperatures, for example?
Dear Guchi, probably, the material manufacturer may have the data that you requested, but I think maybe it is not possible to publish the data.
I am sorry for asking so many questions. The strength of the spring seems to affect the tempering temperature, but is it possible to specify the strength of the spring (tempering temperature?)? That’s all, thank you very much.
Hello! The strength of spring steel after heat treatment is controlled by the hardness after heat treatment. Therefore, the hardness range can be specified! For example, HB388-461 or HRC43-50!
Spring steel is controlled by its hardness, isn’t it? I did not know this! Is the relationship between the hardness and strength described in JIS, etc.? For example, in the case of SUP10, what range can be specified?
Dear Guchi, the relationship between the hardness and strength (tensile strength) is described in JIS (SAE J 417) as a reference.
Regarding the hardness management, we use HB388-461 for compression springs and HRC43-50 for disc springs!
