55Si7 spring steel

Introduction

We manufacture forging ingots, billets, and blooms in alloy steel specifically for 55Si7, designed for high-strength and spring applications where excellent elasticity, fatigue resistance, and toughness are required.

55Si7 is a medium to high carbon silicon spring steel known for its outstanding resilience, high yield strength, and excellent fatigue life. The presence of silicon significantly improves elastic limit and spring performance, making this grade ideal for dynamic and cyclic loading conditions.

This steel grade shows excellent response to quenching and tempering, providing a reliable combination of hardness, toughness, and long service life in demanding spring and automotive applications.

Chemical composition

Element Content (%) Function / effect
Carbon (c) 0.52 – 0.60 Provides high strength, hardness, and fatigue resistance
Silicon (si) 1.50 – 2.00 Increases elastic limit and spring performance
Manganese (mn) 0.70 – 1.00 Improves hardenability and toughness
Phosphorus (p) Max 0.035 Controlled to maintain toughness
Sulphur (s) Max 0.035 Controlled to avoid brittleness

Mechanical properties (typical – quenched & tempered)

  • Tensile strength: 1270 – 1570 MPa
  • Yield strength: High
  • Hardness: 44 – 52 HRC
  • Elongation: Moderate
  • Fatigue resistance: Excellent

(properties may vary depending on section size and heat treatment conditions)

Heat treatment

  • Annealing – improves machinability and softens structure
  • Quenching – heating to approx. 830 – 870°c followed by oil quenching
  • Tempering – controlled reheating to achieve optimum spring properties
  • Stress relieving – used after forming to reduce residual stresses

Key features and benefits

  • Excellent elasticity and resilience
  • High fatigue and shock load resistance
  • Superior spring performance
  • Good hardenability and wear resistance
  • Reliable heat treatment response
  • Long service life under cyclic loading

Typical applications

  • Leaf springs and coil springs
  • Automotive suspension components
  • Valve springs
  • Agricultural springs
  • Industrial spring applications
  • Heavy-duty mechanical springs

Equivalent steel grades

  • En 10089 – 55Si7
  • Din 55Si7
  • Is 3195 – 55Si7 type
  • Jis sup9 (approximate)

Why Choose 55si7 For Your Application?

55si7 Is Specifically Designed For Applications Involving Dynamic Loads And Repeated StreSS Cycles. Its High Silicon Content Ensures Excellent Elasticity, While Its Strength And Fatigue Resistance Make It Ideal For Long Service Life In Demanding Environments. Proper Heat Treatment Enables This Grade To Deliver Consistent And Reliable Spring Performance.

Comparison table for similar grades

Grade Carbon (%) Silicon (%) Key applications Comments
55Si7 0.52 – 0.60 1.50 – 2.00 Leaf & coil springs High elastic limit
60si7 0.56 – 0.64 1.50 – 2.00 Heavy springs Higher strength
51crv4 0.47 – 0.55 0.15 – 0.40 Heavy-duty springs Better hardenability
Sup9 0.52 – 0.60 1.50 – 2.00 Automotive springs Japanese equivalent

Summary

55Si7 is a high-performance silicon spring steel that delivers excellent elasticity, high fatigue strength, and reliable performance under cyclic loading. It is a preferred choice for automotive, agricultural, and industrial spring applications where long service life and consistent Mechanical properties are critical.