EN19 vs EN24: How to Choose the Right Steel Grade for Shafts, Gears and Machined Components

Selecting the right alloy steel grade for a shaft, gear, or precision-machined component isn't just a matter of picking whatever's cheapest or most commonly stocked. For applications beyond what medium carbon steel can handle, alloy steels like EN19 and EN24 offer the added strength, hardenability, and fatigue resistance needed for demanding conditions. Two steels that sit at different points on the strength, hardenability, and cost spectrum. This guide breaks down what separates them and how to choose correctly for your application.

What Is EN19 Steel?

EN19 is a chromium-molybdenum alloy steel, offering strong strength, toughness, and hardenability. It responds well to heat treatment, allowing it to achieve high tensile strength while retaining good ductility — a combination that makes it a preferred choice for components under continuous mechanical stress.

EN19 is typically supplied as:

• Alloy Steel Round Bars
• Alloy Steel Flat Bars
• Alloy Steel Square Bars
• Alloy Steel Hex Bars
• Alloy Steel Shafts (Forged)

This grade is widely used for:

• Automotive and industrial shafts
• Gears requiring good fatigue strength
• Connecting rods, bolts, and high-tensile fasteners
• Components subject to shock loading and cyclic stress

EN19's chromium-molybdenum composition gives it a strong balance of strength and toughness, making it a common mid-to-high-performance choice across machined components in engineering and automotive sectors.

What Is EN24 Steel?

EN24 is a nickel-chromium-molybdenum alloy steel, positioned above EN19 in terms of strength, and resistance to fatigue under heavy, repeated stress. The addition of nickel improves toughness at both room and low temperatures, while chromium and molybdenum contribute to hardenability and wear resistance.

Just like EN19, EN24 is supplied across multiple product forms, including:

• Alloy Steel Round Bars
• Alloy Steel Flat Bars
• Alloy Steel Square Bars
• Alloy Steel Hex Bars
• Alloy Steel Shafts (Forged)

Typical applications include:

• Heavy-duty gears and gear shafts
• High-stress automotive and aerospace components
• Crankshafts, axles, and transmission parts
• Components requiring high tensile strength combined with good impact toughness, verified through tensile strength test procedures during quality checks

EN24 is generally reserved for applications where component failure carries a high cost — either in terms of safety, downtime, or replacement complexity — because its enhanced mechanical properties justify the higher material cost.

EN19 vs EN24: Key Differences at a Glance

How to Choose the Right Grade for Your Application

With the differences between the two grades clear, the actual selection comes down to a handful of practical checks against your specific application:

1. Assess the load and stress conditions — For components under continuous or shock loading, EN19 or EN24 offer strong fatigue resistance depending on severity.
2. Consider heat treatment requirements — Both EN19 and EN24 respond well to heat treatment to achieve specific hardness or strength targets, due to their alloying elements.
3. Factor in the operating environment — Components exposed to repeated impact, high torque, or extreme mechanical stress — such as gear shafts, crankshafts, or axles — benefit from EN24's superior toughness .
4. Balance performance against cost — EN24 delivers the best mechanical performance but comes at a premium. If your application doesn't demand that level of strength, EN19 often provides the right balance of performance and cost for machined components.
5. Match the product form to your manufacturing process — Depending on your fabrication method, these grades are available as Bright Bar, Forged, — for example, EN19 and EN24 are both commonly supplied as Alloy Steel Round Bars, Flat Bars, Square Bars, Hex Bars, and Forged Shafts, giving flexibility depending on whether you're machining from bar stock or working with a forged blank.

Why Getting the Grade Right the First Time Matters

Choosing the wrong steel grade isn't just a technical oversight — it's a business risk that can affect timelines, budgets, and safety.

• Rework Costs — premature failure often means redesigning, re-sourcing, and remanufacturing the component
• Project Delays — sourcing replacements and waiting on fabrication pushes back delivery schedules
• Safety Risks — for critical parts like crankshafts or high-stress gears, failure can endanger operators
• Reputational Impact — repeated material issues erode client trust, especially where reliability is critical
• Hidden Long-Term Costs — a cheaper, under-specified grade often costs more once failure and downtime are factored in

Common Mistakes When Choosing Between EN19 and EN24

Even experienced buyers occasionally get the grade selection wrong between these two — usually by defaulting to habit rather than matching the steel to the actual application.

• Over-specifying EN24 for moderately stressed components — paying a premium for superior toughness that a standard automotive shaft or gear will never fully utilize
• Under-specifying EN19 for heavy-duty applications — choosing EN19 for crankshafts, axles, or components under extreme repeated stress, risking premature fatigue failure where EN24's superior toughness is actually required
• Ignoring impact and low-temperature conditions — overlooking EN24's nickel content advantage in applications exposed to shock loading or low-temperature environments, where EN19 may fall short
• Assuming similar hardenability across both grades — treating EN19 and EN24 as interchangeable for heat treatment purposes, when EN24's excellent hardenability often allows for more demanding hardness targets
• Choosing based on cost alone — defaulting to EN19 purely to save on material cost, without accounting for the long-term cost of premature component failure in high-stress applications

Avoiding these mistakes comes down to one principle: match the grade to the application's real mechanical demands — load, impact, temperature, and hardenability requirements — rather than defaulting to whichever grade is more familiar or cheaper.

Final Thoughts

Choosing between EN19 and EN24 ultimately comes down to matching the steel's mechanical properties to the real-world demands of your shaft, gear, or machined component. EN19 offers a strong middle ground for moderate-to-high stress components, while EN24 is the go-to choice when maximum strength, toughness, and fatigue resistance are non-negotiable. Understanding these distinctions upfront helps avoid costly material mismatches down the line — whether you're sourcing Alloy Steel Round Bars, Flat Bars, or Forged Shafts for your next project.

Still Not Sure Which Grade Is Right for You?

Get in touch with our team to discuss your load, environment, and manufacturing requirements — we'll help you match the right steel grade to the job.