Spring steel bar (round, square and flat) is supplied for springs made by machining or hot-forming, and for axles and shafts. We stock 65Mn, 50CrV4, SUP9 and 9260, annealed or peeled, in straight lengths.
What Is Spring Steel Bar?
Spring steel bar is rolled or forged to round, square or flat section and supplied annealed so it can be machined to a spring component or hot-formed and then heat-treated. Larger diameters are forged for uniformity and freedom from centre porosity.
We keep the main spring grades as bar — 65Mn, 50CrV4 / 51CrV4, SUP9 / 55Cr3 and 9260 — and offer peeled-and-ground bar where a clean, decarburisation-free surface is needed before machining.
Spring Steel Grades Available as Bar
These spring grades are available as bar:
| Grade | Standard | Typical Use |
|---|---|---|
| 65Mn | GB/T 4357, GB/T 1222 | Light coil & flat springs, clips, washers |
| 50CrV4 / 51CrV4 | EN 10270-2 (1.8159) | Engine valve springs, heavy coils, warm service |
| 6150 | ASTM A229 / A401 | Valve & torsion springs (North America) |
| SUP9 / 55Cr3 | JIS G3521, EN 10089 | Heavy leaf and coil springs |
| 9260 | ASTM A229 | Large leaf, buffer and suspension springs |
Size Range and Tolerances
Bar is supplied from 8 mm up to 200 mm, in straight lengths. Tolerance and condition are set per grade and size:
| Diameter / Size | Length | Tolerance | Condition |
|---|---|---|---|
| 8 – 50 mm | 3 – 6 m | h11 | Hot-rolled / Annealed |
| 50 – 100 mm | 3 – 6 m | forged | Forged / Annealed |
| 100 – 200 mm | 3 – 6 m | forged | Forged / Annealed |
| Square / flat | per drawing | per drawing | Annealed / Peeled |
Surface Finish and Delivery Condition
Bar delivery conditions:
As-rolled bar for machining or hot-forming.
Softened bar for machining and subsequent heat treatment.
Forged large-diameter bar for sound centres in heavy springs.
Turned and ground bar with a clean, decarburisation-free surface.
Standards We Supply To
| Standard | Scope |
|---|---|
| EN 10089 | Hot-rolled spring steel |
| ASTM A29 | Carbon and alloy steel bars |
| ASTM A689 | Steel bars for springs |
| JIS G4801 | Spring steel (SUP grades) |
| EN 10278 | Bright steel bars (drawn/ground) |
Physical Properties of Spring Steel
| Property | Typical Value |
|---|---|
| Density | 7.85 g/cm³ |
| Elastic modulus (E) | ~200 GPa |
| Shear modulus (G) | ~79 GPa |
| Thermal conductivity | ~45 W/m·K at room temperature |
| Coefficient of thermal expansion | ~12 ×10⁻₆ /K (20 – 200 °C) |
Applications of Spring Steel Bar
Bar turned into precision coil-spring components.
Bar bent and quenched into large springs.
Spring-grade bar for spring-loaded shafts.
Large sections forged to spring shape.
Spring-grade bar used as tough tool stock.
Fatigue-rated bar for reciprocating parts.
Quality Control and Mill Certificates
Every Bar order ships with an EN 10204 3.1 mill certificate covering heat chemical analysis and the mechanical and dimensional checks on record. We add, on request: ultrasonic or magnetic-particle inspection, hardness mapping, straightness and flatness checks, decarburisation or surface-depth checks, and third-party inspection (SGS / BV) at the mill or before loading. Dimensions are verified to the relevant EN / ASTM / JIS standard or your drawing.
Frequently Asked Questions
Do you supply peeled-and-ground spring bar?
Yes, for diameters where a clean, decarburisation-free surface matters before machining.
What is the largest bar diameter?
Up to 200 mm rolled, and larger forged block on request.
Which grade for a machined high-fatigue spring?
50CrV4 / 51CrV4 gives the best cycle life; 65Mn for lighter duty.
Is the bar supplied annealed?
Annealed or normalized as standard, ready for machining and heat treatment.
Can you cut bars to length?
Yes, sawn or sheared to your required length and quantity.
Related Products
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