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Industry Grade Guide

Engineering Steel for
Defence & Aerospace.

Defence and aerospace applications demand premium grade steel with full traceability, 3.1 material test certificates and quality management systems capable of supporting customer approval processes. Parkside Steel holds BSI ISO 9001 certification (FS 86692) — the documented quality system that defence and aerospace supply chains require from approved material suppliers. EN 10204 3.1 certs are available as standard on all alloy grades.

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Sector Overview

What Defence & Aerospace Demands from a Steel Supplier

Defence and aerospace procurement operates differently from general commercial purchasing. Approved supplier lists, material traceability requirements, first article inspection processes and drawing-specific material approvals all add layers of documentation and process that the supply chain must support.

For steel bar supply, this means: material test certificates to EN 10204 3.1 at minimum (some specifications require 3.2 witnessed inspection — available by arrangement through our supply chain); full traceability from mill heat number through to delivery note; a certified quality management system; and the ability to provide documentation retrospectively if an audit requires it. Parkside Steel provides all of this as standard.

Key Grades

At a Glance.

Full grade list below ↓

Structural & High-Tensile Components

EN24T (817M40T / 34CrNiMo6 / AISI 4340) is one of the most widely specified materials in defence structural applications — used for aircraft undercarriage components, armoured vehicle drivetrain shafts, structural brackets in naval vessels and precision machined components in weapons systems. Its combination of very high tensile strength (up to 1150 N/mm² in small sections), excellent toughness and good deep-section hardenability makes it the premium alloy for stressed structural parts.

The T suffix indicates supply in the quenched and tempered condition — machined directly to drawing without further heat treatment for pre-treated bar. AISI 4340 is the widely recognised equivalent in US defence specifications (MIL-S-5000, AMS 6415 and similar). Parkside Steel supplies 817M40T from stock in bright bar to 150mm and black bar to 350mm, with 3.1 material test certificates as standard.

Recommended Grades

Defence Gearing & Power Transmission

Aerospace and defence gearing demands the very highest combination of case hardness and core toughness — components that must survive shock loads in service without either the case spalling or the core cracking. EN36 (655M13 / 14NiCr14) provides excellent performance for most applications with 58–63 HRC case hardness after carburising and a core toughness that plain carbon and lower-alloy case hardening grades cannot match.

For the most heavily shock-loaded applications — helicopter transmission gears, armoured vehicle final drives, aircraft accessory gearboxes — EN36C (832M13 / 15NiCrMo16-5) adds molybdenum for improved large-section core hardenability and temper embrittlement resistance.

Recommended Grades

Precision Shafts & Nitrided Components

EN40B (722M24 / 31CrMo12) is specified for precision nitrided shafts in aerospace actuators, gyroscopes and precision instrument housings — wherever a very hard, stable, corrosion-resistant surface is required without the dimensional change that conventional hardening would cause. The nitriding process applies compressive residual stresses that significantly improve fatigue life — a critical benefit for rotating shafts in cyclic service.

EN40B is supplied in the Q+T condition — no further core heat treatment is required before nitriding. This reduces processing steps and the risk of distortion in precision components.

Recommended Grades
All Grades for Defence & Aerospace

Recommended Grades — Full List.

Click any grade for full data sheet, chemical composition, mechanical properties and heat treatment guidance.

Not sure which grade is right? Call our sales team on 01623 687 660 — we can advise based on your component, loading and heat treatment requirements.

Common Questions

Frequently Asked.

Yes — Parkside Steel holds BSI ISO 9001 certification, certificate number FS 86692. Our quality management system covers purchasing, stockholding, sawing operations, material traceability and dispatch. Certificate copies available on request.
3.1 material test certificates (manufacturer's authorised inspector) are available as standard on all alloy grades. 3.2 witnessed inspection certificates are available by arrangement through our supply chain for applications requiring independent witness of testing at the mill.
EN24 (817M40) is the UK BS 970 equivalent of AISI 4340. In the quenched and tempered condition it is designated 817M40T (EN24T). The European equivalent is 34CrNiMo6 / 1.6582. These are all the same alloy composition.
Explore Further

Related Industries.

Combilift in orange racking aisle — defence and aerospace grade alloy bar stock
Mixed profile stock in blue racking — round, flat and square bar with colour-coded grades

Talk to Us About Your Defence & Aerospace Requirements.

ISO 9001 FS 86692 — 3.1 certs standard — full traceability. Our sales team understands engineering steel — not just the catalogue. Call with a grade, a component description, or a question.