Spring wire can be supplied in three grades according to tensile strength.
The grade of spring wire used depends on the stress level and the nature of the duty.
Where springs are subjected to static stresses or infrequent dynamic loading a wire grade for static duty (S) shall be used. In the other cases with frequent or predominantly dynamic loading and where small coiling ratios or severe bending radius is required, a wire grade for dynamic duty (D) shall be used.
Depending on the stress level, spring wire is manufactured in 3 tensile strength grades:
Overview of the different grades:
| Tensile strength | Static | Dynamic |
| Low tensile strength | SL | - |
| Medium tensile strength | SM | DM |
| High tensile strength | SH | DH |
| For specific applications, custom tensile strength may be agreed. | ||
Chemical Composition of Cold Drawn Spring Steel Wire of Different Grades
The chemical composition according to the heat analysis shall comply with the limit values shown in Table below or similar.
The permissible deviation of the product analysis from the heat analysis is in accordance with EN 10016-2 and EN 10016-4 or similar.
| Grade | Ca | Si | Mnb | P | S | Cu |
| max. | max. | max. | ||||
| SL, SM, SH | 0,35-1,00 | 0,10-0,30 | 0,50-1,20 | 0,035 | 0,035 | 0,20 |
| DM, DH | 0,45-1,00 | 0,10-0,30 | 0,50-1,20 | 0,020 | 0,025 | 0,12 |
Such a wide range is stipulated to accommodate the whole range of sizes. For individual sizes the carbon range is substantially more restricted. The range of manganese content in the table is wide to cope with various processing situations and the broad size range. The actual figures per size shall be more restricted. |
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NOTE
Some diameter ranges require particular attention for residuals. Therefore no figures are mentioned for chromium, nickel, molybdenum, tin, etc. leaving room for special arrangements between purchaser and supplier, dependent on their mutual processing conditions. This is also the case for the aluminium content.