EN45 is a silico-manganese spring steel with about 0.55% carbon and 1.5–2% silicon. Hardened in oil and tempered, it becomes springy and tough, able to bend and return many times. It is widely used for leaf springs, coil springs and spring clips.
Quick facts
- Type
- Silico-manganese spring steel
- Carbon
- About 0.50–0.60%
- Silicon
- About 1.5–2.0%
- Working hardness
- About 42–50 HRC for springs
- Hardening
- Oil quench, then temper
- As supplied
- Hot rolled or annealed
Equivalent grades
| Standard | Grade |
|---|---|
| BS 970 | 250A58 (EN45), 250A61 (EN45A) |
| EN / DIN | 55Si7, 1.5026 |
| AISI / SAE | Close to 9255 |
| IS | 55Si7 |
Equivalents are close, not identical. Name the grade and standard on the drawing.
Typical chemical composition
| Element | % |
|---|---|
| Carbon (C) | About 0.50–0.60 |
| Silicon (Si) | About 1.5–2.0 |
| Manganese (Mn) | About 0.7–1.0 |
| Sulphur, phosphorus | Low |
Values are typical. The exact limits depend on the standard and supplier; ask for the mill test certificate when it matters.
Heat treatment
- Harden at about 840–870 °C
- Quench in oil
- Temper at about 400–500 °C, depending on the hardness needed
- Spring hardness is usually about 42–50 HRC
- Avoid decarburising the surface; it shortens spring life
Typical uses
- Leaf springs for vehicles and trailers
- Coil springs and disc springs
- Spring clips, washers and retaining parts
- Scraper and agricultural blades
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Questions
- What is EN45 used for?
- Mainly leaf springs and coil springs, and other parts that must flex and return without taking a set, such as clips and blades.
- EN45 or EN47?
- EN45 is a cheaper silico-manganese spring steel for general springs. EN47 (chromium-vanadium) has better fatigue strength and toughness, used for heavily loaded and critical springs.
- What hardness should a spring be?
- Usually about 42–50 HRC. Harder springs can break; softer ones take a permanent set.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 16 October 2026.