SAE 4135 alloy steel

Introduction

We manufacture forging ingots, billets, and blooms in alloy steel specifically for SAE 4135, designed for higher-strength engineering applications where excellent toughness, hardenability, and fatigue resistance are required. SAE 4135 is a medium carbon chromium-molybdenum alloy steel that offers higher strength and hardness than SAE 4130, while maintaining good toughness and machinability. It is widely used in automotive, heavy engineering, and mechanical applications subjected to moderate to high mechanical loads. The addition of chromium improves hardenability and wear resistance, while molybdenum enhances toughness, fatigue strength, and tempering stability. SAE 4135 responds well to quenching and tempering and provides consistent mechanical performance across various section sizes. This grade delivers a reliable balance of strength, durability, and cost-effectiveness for demanding engineering applications.

Chemical composition

Element	Content (%)	Function / effect
Carbon (c)	0.33 – 0.38	Provides higher strength and hardness
Manganese (mn)	0.40 – 0.60	Improves hardenability and toughness
Silicon (si)	0.15 – 0.35	Increases strength and elasticity
Chromium (cr)	0.80 – 1.10	Enhances hardenability and wear resistance
Molybdenum (mo)	0.15 – 0.25	Improves toughness and fatigue resistance
Phosphorus (p)	Max 0.035	Impurity; controlled to maintain toughness
Sulphur (s)	Max 0.040	Impurity; controlled for machinability

Mechanical properties (typical – quenched & tempered)

• Tensile strength: 700 – 950 MPa
• Yield strength: 550 – 750 MPa
• Hardness: 22 – 32 HRC
• Impact toughness: Good
• Fatigue resistance: Very good

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

Heat treatment

• annealing: performed to improve machinability and soften the material before final processing.
• normalizing: refines grain structure and improves mechanical uniformity.
• quenching: heating to approximately 830 – 870°c followed by oil quenching to achieve high strength.
• tempering: reheating to a controlled temperature to reduce brittleness and achieve the desired balance of strength and toughness.Heat treatment parameters can be adjusted based on specific application requirements.

Key features and benefits

• higher strength than SAE 4130
• good toughness and fatigue resistance
• excellent response to quenching and tempering
• good machinability in annealed condition
• dimensional stability after heat treatment
• cost-effective for medium to heavy-duty applications

Typical applications

• gears and pinions
• shafts, axles, and spindles
• automotive and truck components
• forged parts for machinery
• connecting rods and mechanical components
• general engineering applications

Equivalent steel grades

• SAE 4135 has several international equivalents, including:
• EN34crmo4 – european standard
• din 34crmo4 – german standard
• is 1570 (part 3) – 34crmo4 type – indian standard

Why choose SAE 4135 for your application?

SAE 4135 is ideal for applications requiring higher strength than SAE 4130 while retaining good toughness and machinability. Its excellent hardenability and stable heat treatment response make it suitable for components subjected to cyclic loads and moderate impact, ensuring long service life and reliable performance.

Comparison table for similar grades

Grade	Carbon (%)	Key applications	Heat treatment	Comments
SAE 4135	0.33 – 0.38	Shafts, gears, forged parts	Quenching & tempering	Balanced strength and toughness
SAE 4130	0.28 – 0.33	Structural and tubular parts	Normalizing / q&t	Better weldability
SAE 4140	0.38 – 0.43	Critical automotive components	Quenching & tempering	Higher strength and hardenability

Summary

SAE 4135 is a medium carbon chromium-molybdenum alloy steel that provides an optimal combination of strength, toughness, and fatigue resistance. It is a trusted material for automotive, machinery, and engineering applications where consistent performance and durability are required.