C55 carbon steel

Introduction

We manufacture forging ingots, billets, and blooms in carbon steel specifically for C55, designed for high strength and good wear resistance engineering applications. C55 is a medium-high carbon, unalloyed steel grade that offers a strong balance between strength, hardness, and toughness. With a lower carbon content than C65, C55 provides better toughness and improved machinability while still delivering excellent hardness after heat treatment.

C55 exhibits good response to quenching and tempering and is suitable for components subjected to moderate to high mechanical loads and wear conditions. This grade is widely used in automotive, machine building, and general engineering applications where both strength and reliability are required.

Chemical composition

Element	Content (%)	Function / effect
Carbon (c)	0.50 - 0.60	Provides high strength, hardness, and wear resistance
Manganese (Mn)	0.60 - 0.90	Improves hardenability and toughness
Silicon (si)	0.15 - 0.35	Increases strength and acts as deoxidizer
Phosphorus (p)	Max 0.050	Impurity; limited to maintain toughness
Sulphur (s)	Max 0.050	Improves machinability when controlled
Chromium (cr)	Nil	Not intentionally added
Nickel (ni)	Nil	Not present
Molybdenum (mo)	Nil	Not present
Other elements	—	No significant alloying additions

Mechanical properties

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

• Tensile strength: 650 - 850 MPa
• Yield strength: 400 - 600 MPa
• Hardness: 230 - 280 HB (up to ~45–50 hrc after hardening)
• Impact toughness: moderate to good
• Wear resistance: high

Heat treatment

• annealing: performed to soften the steel and improve machinability before final machining.
• normalizing: refines grain structure and improves mechanical uniformity.
• quenching: heating to approximately 800 - 850°c followed by oil or water quenching to achieve high hardness.
• tempering: reheating to a controlled temperature to reduce brittleness and adjust the required balance between hardness and toughness.

Proper heat treatment allows C55 to achieve optimum mechanical performance for demanding applications.

Key features and benefits

• high strength with better toughness than higher carbon grades
• good hardness and wear resistance after heat treatment
• good response to quenching and tempering
• suitable for forging and machining applications
• cost-effective high-performance carbon steel
• reliable and consistent mechanical properties

Typical applications

• shafts and axles
• gears, couplings, and pinions
• springs and wear-resistant components
• automotive and machine components
• forged parts and general engineering components

Equivalent steel grades

C55 has several comparable and equivalent grades, including:

• EN8 /  EN9 (BS standard)
• c55 / 1.1203 (DIN / EN 10083)
• AISI 1055 (american standard)
• IS 1570 (part 2) - indian standard

Why choose C55 for your application?

C55 offers an ideal balance between strength, hardness, and toughness, making it suitable for components that require high mechanical performance without excessive brittleness. Its excellent heat treatment response and cost-effective nature make it a practical choice for a wide range of engineering and automotive applications.

Comparison table for similar grades

Grade	Carbon (%)	Key applications	Heat treatment	Comments
C55	0.50 - 0.60	Shafts, gears, springs	Quenching & tempering	Good balance of hardness and toughness
C45	0.40 - 0.50	General engineering parts	Q&t	Lower hardness than C55
C65	0.60 - 0.70	Blades and wear parts	Q&t	Higher hardness, lower toughness
AISI 1055	0.53 - 0.60	Automotive & machine parts	Q&t	American equivalent

Summary

C55 is a medium-high carbon steel designed for applications requiring high strength and good wear resistance with improved toughness compared to higher carbon grades. With reliable performance and economical pricing, C55 remains a popular choice for heavy-duty engineering components.