SUP-Series Spring Steel

Introduction

We manufacture forging ingots, billets, and blooms in alloy steel covering the complete SUP-Series, designed for high-performance spring applications requiring excellent elasticity, fatigue resistance, and strength under cyclic loading conditions.

The SUP-Series (Japanese Industrial Standard spring steels) includes grades such as SUP6, SUP9, SUP9A, SUP10, and SUP11, each engineered for specific load-bearing and dynamic applications. These steels offer a balanced combination of strength, toughness, and resilience, making them highly suitable for automotive, agricultural, and industrial spring systems.

SUP grades exhibit excellent response to heat treatment, ensuring consistent performance, long service life, and reliability in demanding operating conditions.

Chemical Composition

Element Content (%) Function / Effect
Carbon (C) 0.50 – 0.65 Provides strength, hardness, and fatigue resistance
Silicon (Si) 0.15 – 2.00 Improves elasticity and spring performance
Manganese (Mn) 0.50 – 1.00 Enhances hardenability and toughness
Chromium (Cr) 0.50 – 1.20 Improves wear resistance and hardenability
Phosphorus (P) Max 0.035 Controlled to maintain toughness
Sulphur (S) Max 0.035 Controlled to prevent brittleness

Mechanical Properties

(Properties depend on grade and heat treatment condition)

  • Tensile Strength: 1200 – 1600 MPa
  • Yield Strength: High to Very High
  • Hardness: 45 – 58 HRC
  • Elongation: Moderate
  • Fatigue Resistance: Excellent

Heat Treatment

  • Annealing: Improves machinability and refines grain structure.
  • Quenching: Heating to approximately 800 – 880°C followed by oil quenching.
  • Tempering: Performed to achieve desired hardness and toughness balance.
  • Stress Relieving: Reduces internal stresses after forming or machining.

Key Features and Benefits

  • High elastic limit and resilience
  • Excellent fatigue strength for long service life
  • Good wear resistance and toughness
  • Consistent performance under cyclic loading
  • Versatility across multiple spring applications
  • Good hardenability, especially in chromium-alloyed grades

Typical Applications

  • Automotive leaf springs and coil springs
  • Suspension system components
  • Agricultural equipment springs
  • Industrial springs and mechanical components
  • Torsion bars and heavy-duty load-bearing parts

Equivalent Steel Grades

SUP-Series has several international equivalents, including:

  • JIS – SUP Series (SUP6, SUP9, SUP9A, SUP10, SUP11)
  • EN – 55Si7, 60Si7, 65Si7 (Approximate equivalents)
  • DIN – 55Si7 / 60Si7
  • IS – 3195 Spring Steel Grades

Why Choose SUP-Series for Your Application?

SUP-Series steels are specifically developed for spring applications where reliability under repeated loading is critical. Their optimized chemical composition ensures high strength, excellent elasticity, and superior fatigue life. With strong heat treatment response and consistent performance, SUP grades are ideal for automotive and industrial spring systems operating under severe conditions.

Comparison Table for SUP-Series Grades

Grade Carbon (%) Key Alloying Key Applications Comments
SUP6 0.55 – 0.65 Low Alloy Light Springs Basic Spring Steel
SUP9 0.52 – 0.60 High Silicon Automotive Springs Most Common Grade
SUP9A 0.56 – 0.64 High Silicon Heavy Springs Higher Strength than SUP9
SUP10 0.50 – 0.60 Cr-Si Alloy High-Stress Springs Better Hardenability
SUP11 0.55 – 0.65 Cr-Mn Alloy Heavy-Duty Springs Superior Toughness

Summary

SUP-Series spring steels are high-performance materials designed for demanding spring applications. They offer excellent elasticity, high fatigue resistance, and strong mechanical properties, making them suitable for automotive, agricultural, and industrial uses. With multiple grades available, the SUP-Series provides flexibility to select the right material for specific load and performance requirements, ensuring long service life and reliable operation.

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