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Industry Grade Guide

Engineering Steel for Oil,
Gas & Energy.

Downhole, wellhead and surface processing equipment operates under extreme pressure, corrosive environments and demanding cyclic loading. Grade selection is driven by strength, toughness, sour service resistance and traceability requirements. EN 10204 3.1 material test certificates are not optional — they are mandatory for the majority of oil and gas procurement specifications. Parkside Steel supplies 3.1 certs as standard on all alloy grades.

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Sector Overview

What Oil & Gas Applications Demand from Steel Bar

The oil and gas sector operates at the demanding end of engineering steel specification. Downhole components experience combined tensile, torsional and bending loads at elevated temperatures in H₂S-containing environments. Surface processing equipment must meet pressure equipment directive (PED) requirements. Procurement teams require traceability back to the original mill and heat number.

This means grade selection alone is not sufficient — the supply chain must also provide documentation. A bar of EN24T from a certified stockholder with a 3.1 certificate and documented chain of custody is a fundamentally different product from the same grade bought without that paperwork, even if the steel itself is identical.

Key Grades

At a Glance.

EN19Valve bodies, actuator shafts, wellhead componentsEN24TDrill collars, tool joints, BHA — Q+T, 3.1 certsEN40BNitrided hydraulic rods, precision shaftsEN36High-nickel for toughness in sour service support equipment

Full grade list below ↓

Downhole Drill Collars, Tool Joints & BHA Components

EN24T (817M40T / 34CrNiMo6 / AISI 4340) is the primary grade for downhole drill collars and tool joints. Its combination of high tensile strength (900–1150 N/mm² in the T condition), excellent toughness and good hardenability in large sections makes it the most reliable choice for components that experience severe cyclic loading, impact and bending downhole.

The T suffix indicates supply in the quenched and tempered condition — giving guaranteed mechanical properties without further heat treatment. Available in black round bar to 350mm diameter from stock. EN 10204 3.1 material test certificates — with mill heat number, full chemical analysis and witnessed mechanical test results — supplied as standard. Parkside Steel holds one of the widest single-site UK ranges of large-diameter black round bar.

Recommended Grades
EN24T (817M40T / 4340) Q+T Ni-Cr-Mo. Drill collars, tool joints, BHA. 900–1150 N/mm². 3.1 cert. EN19 (708M40 / 42CrMo4) Cr-Mo alloy. MWD housings, non-mag alternatives, wellhead components.

Valve Bodies, Actuator Shafts & Wellhead Components

EN19 (708M40 / 42CrMo4) is widely used for wellhead valve bodies, actuator shafts and choke components machined from large-diameter round bar. Its high tensile strength, good machinability in the normalised condition and well-documented heat treatment response make it the most common valve body specification for non-sour service.

For sour service applications (H₂S-containing environments), hardness limits apply per NACE MR0175 / ISO 15156 — typically 22 HRC maximum for the bulk material. EN19 in the appropriate tempered condition meets these limits in most cases. Confirm with your company's materials engineer for critical sour service applications.

Recommended Grades
EN19 (708M40 / 42CrMo4) Valve bodies, actuator shafts, choke components. NACE-compatible when correctly tempered. EN24T (817M40T) High-pressure valve and manifold components. Pre-treated Q+T.

Hydraulic Cylinder Rods & Nitrided Components

EN40B (722M24 / 31CrMo12) is specified for subsea and topside hydraulic cylinder rods where nitriding is required to provide a hard, corrosion-resistant surface finish. The gas nitriding process produces a case of 700–850 HV (approximately 65–70 HRC equivalent) without dimensional change — essential for the precision tolerances that hydraulic seals require.

Supplied in the Q+T condition — core properties are established before nitriding and are not significantly altered by the process. EN40B's high chromium content (2.8–3.3%) ensures strong chromium nitride formation during nitriding, producing a dense, wear-resistant compound layer.

Recommended Grades
EN40B (722M24 / 31CrMo12) Nitriding grade. Hydraulic rods, precision shafts. 700–850 HV case. EN19 (42CrMo4) Pump shafts, actuator bodies where nitriding not required.

Pressure Vessel Studs & High-Tensile Bolting

Pressure vessel and flange studs for oil and gas service require high tensile strength (typically 860–1000 N/mm²) and guaranteed low-temperature Charpy impact values. EN19 in the T condition satisfies the majority of ASME and API bolting specifications. S355 J2 with its guaranteed Charpy impact at −20°C covers lower-specification structural bolting and flange applications.

The J2 sub-grade of S355 is specifically chosen for low-temperature environments — the Charpy V-notch impact test at −20°C gives engineers confidence for offshore and cold climate installations.

Recommended Grades
EN19T (708M40) High-tensile studs and bolting. ASME and API specification compatible. S355 J2 Structural bar. Guaranteed Charpy at −20°C. Offshore flanges and bolting. EN24T (817M40T) Premium bolting where maximum tensile and toughness required.
All Grades for Oil, Gas & Energy

Recommended Grades — Full List.

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

EN19 42CrMo4 Valve bodies, actuator shafts, wellhead components EN24T 817M40T / 4340 Drill collars, tool joints, BHA — Q+T, 3.1 certs EN40B 31CrMo12 Nitrided hydraulic rods, precision shafts EN36 655M13 High-nickel for toughness in sour service support equipment S355 S355J2 Structural bar — offshore flanges, −20°C Charpy EN8 080M40 General surface equipment, manifold supports

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 — 3.1 material test certificates are available as standard on all alloy grades. The certificate references the specific heat number, contains the full chemical analysis and mechanically witnessed test results. Request when ordering and we supply it with the delivery or electronically.
600mm diameter in black round bar (hot rolled). Parkside Steel holds one of the widest single-site ranges of large-diameter engineering bar in the UK.
EN24T in correctly tempered condition can meet NACE MR0175 / ISO 15156 hardness requirements. The maximum allowable hardness is typically 22 HRC (250 HB) for the bulk material. Confirm the tempering condition and hardness with your materials engineer for sour service.
Explore Further

Related Industries.

Defence & Aerospace ► Hydraulics & Pneumatics ► General Engineering ►
Operative loading 400mm EN3B black round bar — large diameter stock for oil and gas applications
Aisle between banks of large diameter black bar racking — oil and gas grade stock

Talk to Us About Your Oil, Gas & Energy Requirements.

3.1 certs standard — large diameter to 600mm — all alloy grades in stock. Our sales team understands engineering steel — not just the catalogue. Call with a grade, a component description, or a question.

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