En351 alloy steel

Introduction

We manufacture forging ingots, billets, and blooms in alloy steel specifically for En351, tailored for heavy-duty case hardening applications.

En351 is a low carbon nickel–chromium alloy steel known for its excellent case hardening characteristics, high surface hardness, and exceptionally tough core. It is designed for components subjected to heavy loads, shock, and continuous wear, making it ideal for critical automotive and engineering applications.

The presence of nickel improves core toughness and fatigue resistance, while chromium enhances hardenability and wear resistance after carburizing. En351 offers good machinability in the annealed condition and maintains dimensional stability after heat treatment, making it suitable for forging and precision machining processes.

This steel provides an excellent combination of surface durability, core strength, and long service life for demanding industrial applications.

Chemical composition

Element	Content (%)	Function / effect
Carbon (c)	0.10 – 0.20	Ensures tough and ductile core
Manganese (mn)	0.40 – 0.70	Improves hardenability and strength
Silicon (si)	Max 0.35	Increases strength
Nickel (ni)	2.75 – 3.25	Improves toughness and fatigue resistance
Chromium (cr)	0.80 – 1.10	Improves hardenability and wear resistance
Phosphorus (p)	Max 0.035	Impurity; controlled for toughness
Sulphur (s)	Max 0.035	Impurity; controlled for machinability

Mechanical properties (typical, depending on condition & heat treatment)

• Core tensile strength: 700 – 900 MPa
• Core yield strength: 450 – 650 MPa
• Surface hardness (carburized): 58 – 62 HRC
• Core hardness: 180 – 220 HB
• Impact toughness: Very high
• Fatigue resistance: Excellent

Heat treatment

• annealing: improves machinability before carburizing.
• carburizing: introduces carbon at high temperature to achieve a hard, wear-resistant surface.
• quenching: rapid cooling to obtain a hard martensitic case.
• tempering: relieves internal stresses while maintaining surface hardness and core toughness.

The heat treatment cycle can be adjusted based on required case depth and application requirements.

Key features and benefits

• excellent case hardening response: hard surface with tough core
• high impact and fatigue resistance: suitable for shock-loaded components
• good wear resistance: long service life
• good machinability in annealed condition: ease of manufacturing
• dimensional stability after heat treatment
• suitable for forging and machining processes

Typical applications

• heavy-duty gears and pinions
• transmission and differential components
• camshafts and crankshaft gears
• automotive and tractor parts
• engineering components requiring high wear resistance

Equivalent steel grades

• En351 has several international equivalents, including:
• en36 – close equivalent
• din 1.5752 (approximate)
• 17CrNimo6 (application-based comparison)

Why choose En351 for your application?

En351 offers an outstanding combination of surface hardness, core toughness, and fatigue resistance. Its nickel–chromium alloying makes it ideal for components operating under heavy loads and repeated stress, while maintaining reliable performance and dimensional stability.

Comparison table for similar grades

Grade	Carbon (%)	Key applications	Heat treatment	Comments
En351	0.10 – 0.20	Heavy gears, transmission parts	Carburizing + q&t	High toughness ni-cr steel
En36	0.12 – 0.18	Heavy-duty gears	Carburizing	Very close equivalent
16MnCr5	0.14 – 0.19	Automotive gears	Carburizing	Lower ni, lower toughness
17CrNimo6	0.14 – 0.19	Heavy transmission parts	Carburizing	Higher alloy grade

Summary

En351 is a nickel–chromium low carbon alloy steel optimized for case hardening applications in automotive and heavy engineering industries. It delivers a hard, wear-resistant surface, a tough core, and excellent durability for high-stress components.