Steel Extension Spring Extended Tension Spring Wire Diameter 2.0-5.0

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1. Performance
   • High-Carbon Spring Steel Core – Coiled from ASTM A228 music-wire or EN 10270-1 grade SH with tensile strengths of 1 400–1 900 MPa (wire Ø2.0–5.0 mm). Oil-tempered and stress-relieved at 250 °C for outstanding elasticity and minimal permanent set after repeated elongation.
   • Precise Force Characteristics – Outer diameters Ø20–30 mm and active‐coil counts tailored to deliver spring rates from 10 N mm⁻¹ to 80 N mm⁻¹, with built-in initial tension up to 15 % of maximum working load to ensure tight closure in the neutral position.
   • Shot-Peened Surface – Introduces compressive residual stresses that boost fatigue life by 40 % and increase resistance to micro-crack propagation under cyclic loading.
   • Broad Operating Window – Maintains linear force output from −40 °C to +120 °C; modulus variation <3 % across this range guarantees predictable behavior in outdoor, automotive, and industrial environments.
2. Application Scenarios & Assembly Requirements
   • Industrial Mechanisms – Counterbalances for access hatches, conveyor take-ups, and vibratory feeders rely on the Ø3–5 mm series for high stored energy and compact packaging.
   • Automotive & Transport – Door checks, seat recliner linkages, and trailer ramp assists use medium-diameter springs to offset panel weight and provide controlled rebound.
   • Agricultural & Construction Equipment – Tensioners for chain drives and belt systems benefit from corrosion-protected variants when exposed to dust, slurry, or de-icing agents.
   • Assembly Guidelines:
   – End Style Selection: choose machine loops or extended hooks for general duty; swivel or threaded inserts for precise preload adjustment.
   – Maximum Extension: limit travel to 85 % of elastic range (≈ L₀ + 0.8 × ΔL_solid) to prevent loss of initial tension.
   – Safety Cables: when installed overhead, route a secondary cable through the coil to retain fragments if failure occurs.
   – Loop Alignment: maintain ≤ 5° angular misalignment between spring axis and attachment pins to avoid side loading.
3. User-Friendly Operation
   • Pre-Set & Color-Coded – Factory scragging removes early relaxation; epoxy color bands on hooks identify spring rate and free length, simplifying on-site matching.
   • Ready-to-Install Finish – Lightly oiled black-oxide or zinc-phosphate coating protects against rust during storage and handling without flaking or contaminating adjacent parts.
   • Tool-Lite Replacement – Installation requires only basic hand tools (combination wrench or locking pliers); hooks engage standard eye bolts or clevis pins in seconds.
   • Low-Maintenance Service – No lubrication needed after assembly; periodic visual inspection for coil stretch or surface corrosion suffices for multi-year deployments.
4. Quality & Longevity
   • ISO 9001 / IATF 16949 Production – Statistical process control on wire drawing, coiling pitch, and heat treatment keeps load tolerance within ±7 % and free-length tolerance within ±1 mm.
   • Endurance Validation – Sample springs cycled 500 000 times at 60 % of maximum rated extension show <4 % load decay and no hook deformation, meeting stringent fatigue criteria for safety-critical applications.
   • Protective Coatings & Compliance – Optional epoxy-powder topcoat extends salt-spray resistance to >144 h; all variants are RoHS & REACH compliant, free from hexavalent chromium and heavy-metal additives.
   • Full Traceability – Each spring carries a laser-etched batch code linking to 3.1 material certificates and load/deflection curves, ensuring reliable documentation for OEM and maintenance records.