Spring Steel Coil / Strip Overview
Applications
Spring steel strip finds its way into any component that needs to flex, retain or grip, across a wide range of industries:
- Automotive components. Retaining clips, seat springs, contact strips, shims, clutch plates
- Saw blade and cutting tool manufacture. Blade backs, hacksaw blades, band saw stock, scraper blades
- Appliance and electrical. Contact springs, terminal clips, switch components
- Hand tools. Measuring tape stock, blade components, spring clips, tensioning parts
- Furniture and fittings. Seat suspension springs, catch mechanisms, formed hardware
- General stamping. Washers, spacers, snap rings, formed spring components
Choosing the Right Temper Condition
Three conditions are available, and each shifts the trade-off between formability and finished-part readiness.
- Annealed strip is soft and fully formable. You form the component, then harden and temper it. This suits complex shapes with tight bends that could not be formed in hard material. The cost is an extra heat treatment operation and the distortion that comes with it.
- Hardened and tempered strip arrives at working hardness, already quenched and tempered by the mill to a specified range. You form it directly and the component is finished. Forming is restricted to gentler bends because the material is already hard, but there is no heat treatment, no distortion and no scale to remove.
- As-rolled tempered strip takes its strength from cold work rather than heat treatment. It is economical and adequate for lightly stressed components, but it loses temper if heated, which rules it out wherever welding or brazing follows.
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Condition
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Formability
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Post-forming treatment
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Best suited to
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Annealed
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Highest, tight bends possible
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Harden and temper required
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Complex clips, deep formed parts
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Hardened and tempered
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Limited, generous radii needed
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None
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Flat springs, blades, contact strips
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As-rolled tempered
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Moderate
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None, but heat sensitive
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Shims, washers, lightly stressed parts
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What Hardness Does to Bendability
Flat spring components are almost always bent, and bend performance in hardened strip is far more restrictive than most designers expect.
Minimum bend radius is expressed as a multiple of thickness, and it rises steeply with hardness.
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Condition
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Approximate hardness
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Minimum bend radius
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Annealed
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Under 250 HV
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0 – 1 × thickness
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Tempered, low
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380 – 420 HV
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2 – 3 × thickness
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Tempered, medium
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420 – 480 HV
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3 – 5 × thickness
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Tempered, high
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480 – 550 HV
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5 – 8 × thickness
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Grain direction compounds this. Rolling elongates the grain along the strip length, so bending across that direction is considerably more forgiving than bending along it. Lay the blank out so the bend line runs across the rolling direction wherever nesting permits. On components with bends in two directions, orient the tighter bend favourably and accept the gentler one along the grain.
Springback also increases with hardness. Hard strip springs back substantially further than annealed material, so tooling must overbend, and tooling proved on one temper will not produce correct angles on another.
Choosing the Right Edge Finish for Fatigue-Loaded Springs
Edge condition is the most underspecified characteristic in spring strip, and on fatigue-loaded components it determines service life.
A slit edge carries a burr and a work-hardened zone from the slitting knives. On a component stressed in bending, the edge sits at peak stress, so a rough or burred edge becomes a crack initiation site in exactly the wrong place. Fatigue failures in flat springs originate at the edge far more often than at the surface.
- Mill slit edge – Economical, adequate for shims, washers and static components
- Deburred edge – Burr removed mechanically. Suits general flat spring work
- Rolled or dressed edge –Profiled to a radius, removing the work-hardened zone. Specified for fatigue-critical springs and saw blade backs
- Ground edge – Highest quality, where the edge is functional or maximum fatigue life is required
Burr orientation matters separately. Bending with the burr on the outside of the bend concentrates strain at the burr and initiates cracking, so blank layout should account for slitting direction.
Size Range and Tolerance
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Parameter
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Annealed strip
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Hardened and tempered strip
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Thickness
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0.10 – 6 mm
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0.10 – 3 mm
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Width
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4 – 600 mm
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4 – 400 mm
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Thickness tolerance
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±0.01 to ±0.05 mm by gauge
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±0.01 to ±0.04 mm by gauge
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Width tolerance
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±0.10 mm on slit width
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±0.10 mm on slit width
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Hardness
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Under 250 HV
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380 – 550 HV to specification
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Surface
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Bright or polished
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Blue tempered or polished
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Coil weight
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25 – 500 kg
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25 – 400 kg
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Physical Properties and Spring Rate
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Property
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Typical value
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Density
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7.85 g/cm³
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Elastic modulus
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200 – 210 GPa
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Tensile strength, tempered
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1200 – 1900 MPa
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Elastic limit
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70 – 85% of tensile strength
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Thermal expansion
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11 – 12.5 µm/m·K
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Spring rate in a flat spring depends on modulus, thickness and geometry, not on hardness. Hardness sets how far the spring can deflect before taking a permanent set; it does not change the force required for a given deflection. Designers wanting a stiffer spring must change the section or the geometry, since a harder temper will not do it.
Spring Steel Coil Stockists in India
The value delivered by capable Spring Steel Coil Stockists in India lies in width availability rather than gauge. Mills roll to standard widths, and a stamper needs strip slit to suit the blank layout, because on a high-volume job the width that minimises skeleton scrap is worth more than any difference in the coil rate.
Slitting is therefore central to what we do, along with holding both temper conditions, since a stamper working in a hardened strip cannot substitute annealed material and vice versa.
TSB Global LLP holds and supplies rather than rolls, and coordinates slitting and edge dressing through qualified processors.
- Slitting to customer width, improving blank utilisation and reducing scrap
- Annealed and hardened-and-tempered conditions both held
- Part-coil quantities released, removing the mill tonnage minimum
- Coil weights matched to the customer's decoiler and press feed capacity
- Edge condition supplied to requirement, from mill slit through to dressed edge
- Heat continuity maintained within an order, keeping press setup stable through a run
Testing and Certification
Strip is released against chemical analysis, hardness, tensile strength and, on hardened and tempered material, the tempering condition achieved.
- Bend testing to a specified radius in both grain directions, confirming forming behaviour before production commits
- Decarburisation depth to ISO 3887, which affects fatigue life in strip as it does in bar
- Surface inspection for rolled-in defects, scratches and scale
- Thickness profile measurement across the width and along the coil
- Edge condition verification including burr height on slit material
- Third-party inspection through TUV, SGS, BV or a nominated agency
Certification is EN 10204 3.1 as standard, with 3.2 where automotive approval requires it.
Spring Steel Coil Exporters in India
As Spring Steel Coil Exporters in India, we ship to stampers, spring makers and blade manufacturers across the Gulf, Southeast Asia, Africa and Europe.
Strip is delicate in a way heavier coils are not. Thin hardened strip damages easily, and the edges are both the most vulnerable part of the coil and the most functionally important. Coils are fitted with edge protectors, bound with tension sufficient to hold the wrap without indenting the outer laps, and packed supported rather than resting on their own edge.
Corrosion is more acute here than on heavy coil, because a pit on 0.3 mm strip represents a far greater proportion of the section. Strip is oiled, wrapped in VCI film with a moisture barrier, and desiccant added on tropical routes. Coil tags state temper condition and hardness range prominently, since annealed and hardened strip look similar and using the wrong one destroys a production run.
Why Choose Us
Sourcing spring steel strip has more variables than most suppliers account for — temper, edge quality, slit width, grain direction. Here's why stampers and spring makers choose TSB Global LLP:
- Both tempers stocked — annealed and hardened-and-tempered, no forced substitutions
- Custom slitting — widths matched to your blank layout, less skeleton scrap
- Edge to spec — mill slit through to dressed and ground, for fatigue-critical parts
- Part-coil quantities — no mill tonnage minimums
- Heat continuity — stable press setup across a full run
- Fully tested & certified — hardness, tensile, decarburisation to ISO 3887, EN 10204 3.1/3.2
- Export-ready packing — edge-protected, VCI-wrapped coils
- Stockist, not roller — sourced from established Indian producers, slitting coordinated through qualified processors
Get the Right Strip, in the Right Temper
Send us your thickness, width and application, and we'll confirm the temper condition, edge finish and coil specification that suits your forming process — before it reaches your press. Request a quote from TSB Global LLP today.
About This Page
Bend radius and hardness figures are typical values for guidance and vary with grade, temper, tooling and forming method. They should be confirmed by trial before tooling is committed. Property ranges vary between grades and producers, and the mill certificate governs. Spring design should be carried out by a qualified engineer rather than derived from general material data.
