{"id":133,"date":"2026-09-22T10:23:43","date_gmt":"2026-09-22T10:23:43","guid":{"rendered":"https:\/\/nileshsteelco.com\/blog\/?p=133"},"modified":"2026-09-22T10:23:45","modified_gmt":"2026-09-22T10:23:45","slug":"en26-en30b-en39b-round-bars-a-complete-guide-for-engineering-buyers","status":"publish","type":"post","link":"https:\/\/nileshsteelco.com\/blog\/2026\/09\/22\/en26-en30b-en39b-round-bars-a-complete-guide-for-engineering-buyers\/","title":{"rendered":"EN26, EN30B & EN39B Round Bars: A Complete Guide for Engineering Buyers"},"content":{"rendered":"\n

When a component has to survive heavy shock loads, high torque and constant fatigue, ordinary carbon steel is rarely enough. Gearboxes, drive shafts, heavy machinery and oilfield tools rely on nickel-alloyed steels that combine strength, toughness and deep hardening. Three legacy British grades that still turn up regularly in engineering enquiries are EN26 round bars<\/a><\/strong>, EN30B round bars<\/strong> and EN39B round bars<\/strong>.<\/p>\n\n\n\n

This guide explains what each grade is, how they differ, where they are used, and what buyers should check before placing a bulk order.<\/p>\n\n\n\n

Understanding the EN Designation System<\/strong><\/h2>\n\n\n\n

The \u201cEN\u201d numbers come from the old British Standard BS 970, which is still widely used in trade and drawings even though newer European standards have replaced it on paper. Each grade also has a modern \u201cM\u201d number and, in most cases, a DIN or ISO equivalent. That is why one steel can appear under several names on different purchase orders.<\/p>\n\n\n\n

EN Grade<\/strong><\/td>BS 970 Designation<\/strong><\/td>Approximate Equivalent<\/strong><\/td>Type<\/strong><\/td><\/tr><\/thead>
EN26<\/td>826M40<\/td>40NiMoCr10-5 (1.6745)<\/td>Ni-Cr-Mo through-hardening steel<\/td><\/tr>
EN30B<\/td>835M30<\/td>High-nickel Ni-Cr-Mo grade<\/td>Through-hardening, air-hardening steel<\/td><\/tr>
EN39B<\/td>835M15<\/td>15NiCrMo16-5<\/td>Ni-Cr-Mo case-hardening steel<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Always confirm the exact standard on your drawing. Equivalents are close but not always identical in chemistry limits.<\/p>\n\n\n\n

EN26 Round Bars (826M40)<\/strong><\/h3>\n\n\n\n

EN26 round bars<\/strong> are a nickel-chromium-molybdenum alloy steel, supplied in the hardened and tempered condition for high-strength engineering parts. With medium carbon content and a balanced mix of nickel, chromium and molybdenum, EN26 offers good hardenability, high tensile strength and dependable toughness. It is often compared with the popular EN24 grade and with AISI 4340, and it falls into the same family of workhorse alloy steels. If you are weighing EN26 against EN24 or 42CrMo4<\/strong>, see our buyer\u2019s guide to 42CrMo4, EN19 and EN24<\/strong> forged round bars.<\/p>\n\n\n\n

Typical applications:<\/strong> crankshafts, connecting rods, axles, drive shafts, gears, pinions, high-tensile bolts, studs and heavy machinery components.<\/p>\n\n\n\n

Why buyers choose it:<\/strong> good strength-to-weight performance, reliable response to heat treatment, and strong fatigue resistance in dynamic loading.<\/p>\n\n\n\n

EN30B Round Bars (835M30)<\/strong><\/h3>\n\n\n\n

EN30B round bars<\/a><\/strong> sit at the high-performance end of this group. EN30B is a nickel-chromium-molybdenum steel with a high nickel content, which gives it very high hardenability. It can achieve through-hardened properties in large cross-sections and is known for exceptional toughness at high strength levels. Heat treatment is typically by hardening and tempering, and the steel\u2019s air-hardening tendency means it must be handled with care during heating, cooling and welding.<\/p>\n\n\n\n

Typical applications:<\/strong> heavy-duty shafts and rolls, downhole and drilling tools, rock-drilling components, heavy construction tools, aircraft and high-stress structural parts, and large gear shafts.<\/p>\n\n\n\n

Why buyers choose it:<\/strong> it delivers strength and impact resistance in thick sections where lower-alloy steels would not harden through to the core.<\/p>\n\n\n\n

EN39B Round Bars (835M15)<\/strong><\/h3>\n\n\n\n

EN39B round bars<\/strong> are different in purpose. EN39B is a case-hardening (carburising) steel, with low carbon content and a high nickel-chromium-molybdenum alloy level. After carburising and hardening, the part gets a very hard, wear-resistant surface layer while the core stays tough and shock resistant. Its high hardenability means the core can develop high strength even in large sections, with core strengths in the range of around 1300 MPa cited for properly treated components.<\/p>\n\n\n\n

Typical applications:<\/strong> heavy-duty gears and gear shafts, clutch plates, camshafts, flywheels, rocker components, heavy roller bearings and high-load transmission parts. It is widely used in automotive, aerospace, defence and general mechanical engineering.<\/p>\n\n\n\n

Why buyers choose it:<\/strong> it combines a hard, wear-resistant case with a tough core, ideal where surface wear and shock loads act together.<\/p>\n\n\n\n

EN26 vs EN30B vs EN39B: How to Choose<\/strong><\/h3>\n\n\n\n

Choose EN26<\/strong> when you need a strong, versatile through-hardening alloy for shafts, axles and general high-stress parts, and your section sizes are moderate to large.<\/p>\n\n\n\n

Choose EN30B<\/strong> when the component is very large, heavily loaded or shock loaded, and you need through-hardening capability with excellent toughness at high strength.<\/p>\n\n\n\n

Choose EN39B<\/strong> when the part needs a very hard surface and a tough core, such as gears, cams and heavy-duty transmission components, and your process includes carburising.<\/p>\n\n\n\n

A quick rule: EN26 and EN30B are through-hardening grades supplied for direct use after hardening and tempering, while EN39B is a case-hardening grade that needs carburising to reach its full surface hardness.<\/p>\n\n\n\n

Machinability and Heat Treatment Notes<\/strong><\/h3>\n\n\n\n