Short answer: EN47 is a chromium-vanadium spring steel. Its current designations are 51CrV4 (EN 10089, material no. 1.8159) and BS 970 735A51 / 735A50. The Indian Standard equivalent is 50Cr4V2, the American equivalent is AISI/SAE 6150, and the closest Japanese grade is JIS SUP10.
In this guide: What is EN47 · Equivalents · Annealed vs hardened · Applications · Forms & sizes · Buying checklist · FAQ
What is EN47 spring steel?
EN47 is a medium-carbon alloy steel with about 0.5% carbon, 1% chromium and a small, deliberate addition of vanadium. The chromium gives it hardenability, so thick sections harden right through in oil. The vanadium refines the grain, which improves fatigue life and resistance to softening when the part is tempered. The result is a steel that can be hardened to a very high strength and still flex millions of times without cracking or taking a permanent set — exactly what a spring needs.
| Element | Min % | Max % |
|---|---|---|
| Carbon (C) | 0.47 | 0.55 |
| Silicon (Si) | — | 0.40 |
| Manganese (Mn) | 0.70 | 1.10 |
| Chromium (Cr) | 0.90 | 1.20 |
| Vanadium (V) | 0.10 | 0.25 |
| Phosphorus (P) | — | 0.025 |
| Sulphur (S) | — | 0.025 |
Chemistry as per 51CrV4 (EN 10089). Full data — mechanical properties, transformation temperatures and heat-treatment cycles — is on our EN47 / 51CrV4 datasheet.
EN47 equivalent grades (India, Europe, US, Japan)
Buyers in India see this steel under many names on drawings and purchase orders. These are the designations you will meet most often:
| Standard | Designation | Note |
|---|---|---|
| BS 970 (old) | EN47 | Still the most common name in the Indian market |
| BS 970 (1970s onward) | 735A51 / 735A50 | Six-character BS codes |
| EN 10089 (Europe) | 51CrV4 / 1.8159 | Current European spring-steel standard |
| DIN (Germany, older) | 50CrV4 | Older name for the same steel |
| IS (India) | 50Cr4V2 | Indian Standard equivalent |
| AISI / SAE (USA) | 6150 | Chromium-vanadium steel |
| JIS (Japan) | SUP10 | Closest Japanese spring steel |
| SS (Sweden) | 2230 | — |
These are close equivalents, not identical specifications — carbon, manganese and impurity limits vary slightly between standards. If the part is safety-critical, order against the exact standard on the drawing and check the mill test certificate.
Annealed vs hardened & tempered EN47
EN47 bar is normally bought soft-annealed and hardened only after the part is made. Annealed EN47 is limited to a maximum of about 248 HB, so it can be machined, bent, forged or coiled without cracking tools or the part.
Once the part is formed, it is hardened (typically 830–860 °C, quenched in oil) and tempered (typically 380–680 °C, depending on the strength required). In the spring-temper range EN47 reaches a tensile strength of around 1350–1650 MPa with a 0.2% proof stress of 1200 MPa or more. Lower tempers give maximum spring strength; higher tempers trade some strength for toughness.
That is why we supply EN47 annealed: it lets you do all the shaping first and get the final properties from your own heat treatment.
Applications: where EN47 is used
| Component | Why EN47 | Usual starting form |
|---|---|---|
| Leaf springs (trucks, trailers, railway) | High fatigue strength under repeated bending | Flat bar |
| Coil springs and suspension springs | Hardens through in thick wire and bar sections | Round bar |
| Torsion bars and stabiliser (anti-roll) bars | Resists twisting fatigue | Round bar |
| Valve springs and clutch springs | Keeps its load at elevated temperature | Round bar |
| Clutch and brake components | Strength with good toughness | Round or flat bar |
| Hand tools (spanners, chisels, pliers) | Hard, tough and wear-resistant after heat treatment | Square or flat bar |
EN47 forms and sizes we stock in Mumbai
We keep annealed EN47 spring steel in ready stock at our Darukhana godown in Mumbai:
- Round bar: Ø16 to Ø205 mm
- Square bar: 16×16 to 55×55 mm
- Flat bar: 28×36, 36×45 and 45×55 mm
EN47 is the only grade we stock in square and flat as well as round; our other grades are stocked as round bar.
EN47 buying checklist
- Grade and standard: write the designation your drawing uses (EN47, 51CrV4, 735A51 or 50Cr4V2) so the certificate can be checked against it.
- Condition: annealed for parts you will machine or form; confirm if your heat treater needs anything else.
- Form and size: round, square or flat, section size and length.
- Mill test certificate: check the heat number, chemistry (especially C, Cr and V) and hardness.
- Quantity and terms: our minimum order is 100 kg. Cutting is available if the balance piece is also taken, and is charged extra. Prices are ex-Darukhana; loading, transport and cartage are extra at actuals.
EN47 spring steel: frequently asked questions
What is the Indian equivalent of EN47?
The Indian Standard equivalent of EN47 is 50Cr4V2. It is the same chromium-vanadium spring steel family as 51CrV4 (EN 10089) and BS 970 735A51.
Is EN47 the same as 51CrV4?
Yes, for practical purposes. EN47 is the old BS 970 name; 51CrV4 (material number 1.8159) is the current European designation for the same chromium-vanadium spring steel. Chemistry limits differ slightly between standards, so specify the one your drawing calls for.
What is the difference between 50CrV4 and 51CrV4?
50CrV4 is the older German (DIN) name and 51CrV4 is the name used in the current European standard EN 10089. They describe essentially the same steel and are traded as equivalents.
What is the hardness of annealed EN47?
Soft-annealed EN47 is typically limited to a maximum of about 248 HB, which makes it practical to machine, bend or form before the finished part is hardened and tempered.
What is EN47 used for?
EN47 is used for highly stressed springs and spring-like parts: leaf springs, coil springs, torsion bars, stabiliser bars, valve springs, clutch components and hand tools.
Do you stock EN47 spring steel in Mumbai?
Yes. We keep annealed EN47 in ready stock at Darukhana, Mumbai: round bar Ø16–205 mm, square bar 16×16 to 55×55 mm and flat bar 28×36, 36×45 and 45×55 mm. Minimum order is 100 kg and every dispatch comes with a mill test certificate.
Buy EN47 spring steel from Sai International
Send us the grade, size and quantity and we will confirm stock and price the same day. Every dispatch is accompanied by a mill test certificate.
Ask for EN47 sizes and price WhatsApp enquiry
Values above are typical figures for guidance under EN 10089 / BS 970 and are not a guarantee; actual properties depend on size, heat treatment and heat. Please confirm suitability for your application with our team.