ASTM A36 S235JR Q235B Carbon Structural Steel Round Bar

Hot rolled and hot forged carbon structural round bar to ASTM A36/A36M, with S235JR (EN 10025-2) and Q235B (GB/T 700-2006) supplied as equivalent routes for European and Chinese drawings. Diameter 20 mm to 500 mm, EN 10204 3.1 certificates, cut to length on request.

This is the 250 MPa structural class: the steel behind base plates, anchor templates, machine frames, stair stringers, guard rails and the thousand welded parts that hold a plant together. It is not a heat-treatable grade and it is not sold on hardness. It is sold on weldability, price and the fact that every fabricator in the world can buy consumables for it.

Equivalent to: EN 10025-2 S235JR; GB/T 700-2006 Q235B; JIS G3101 SS400 (similar class); DIN 17100 St37-2

Q235B forged round bar

Specification at a Glance

• Product form: hot rolled round bar, hot forged round bar; peeled or turned on request

• Diameter range: 20 mm – 500 mm; lengths 3–6 m, cut to size

• Delivery condition: as-rolled / as-forged (+AR); normalized (+N) on request

• Production route: BOF or EAF melting, ladle refining, continuous casting or ingot, rolling or forging

• Standards: ASTM A36/A36M (bar), EN 10025-2 S235JR, GB/T 700-2006 Q235B

• Certificates: EN 10204 3.1 with ladle analysis and tensile results; 3.2 by arrangement

• Testing: tensile per heat; impact, grain size and UT only where specified on the order

• Lead time: stock sizes ex-warehouse; forged diameters typically 20–35 days

Chemical Composition

A36 is a performance specification before it is a chemistry specification. It fixes a minimum yield and a tensile band, then allows a chemistry window wide enough that mills can hit the mechanical result with whatever lean scrap mix the melt shop has available. That is why two A36 certificates can look quite different from each other and both be correct.

The one number worth reading closely is carbon. At 0.26 % maximum, A36 is firmly mild steel — weldable without preheat in normal thicknesses, machinable with ordinary tooling, and tough enough for static structures. Manganese at 0.80–1.20 % provides the strength, and phosphorus and sulfur are held low enough that the plate and bar do not crack during rolling. Note that ASTM A36/A36M tabulates carbon and manganese by product form and thickness, and editions have moved these figures; the value on the mill certificate is the one to check against the clause for the product you actually bought.

Read across the C and Mn rows and the reason A36 and S235JR are "equivalent but not identical" becomes obvious. S235JR holds carbon to 0.17 % and buys its strength with up to 1.40 % manganese; A36 allows more carbon and a narrower manganese band. In welding terms the European grade is the more forgiving of the two, and a fabricator working to an EN 1090 execution class will want the S235JR certificate even where an A36 drawing was issued.

Mechanical Properties

The 250 MPa yield is the floor for every thickness A36 covers — unlike the higher-strength structural grades, A36 does not step its yield down with section size, which is one of the reasons it stayed in service drawings for a century. The tensile band is deliberately wide at 400–550 MPa, and a mill certificate sitting near either end of that band is conforming.

The impact row is the one that decides winter projects. A36 carries no Charpy requirement at all, which is not a defect in the grade — it simply reflects that A36 was written for statically loaded structures in temperate service. If a drawing calls for A36 and the site is at −20 °C in January, the requirement needs a supplementary impact clause or a change of grade to the D / J2 level. The same bar shape and the same machining operations then come with a different certificate and a different price; the relevant cold-region grades are the Q235D / S235J2 round bar at −20 °C and the Q355D / S355J2 round bar where 355 MPa is also needed.

Equivalent Grades

Three of these appear on the same enquiry more often than any others: A36, S235JR and Q235B. They are close enough that a purchasing department will treat them as one item and different enough that the certificate may not satisfy the inspector. The safest approach is to name the standard the project is designed to and let the mill issue against that, rather than ordering "A36 or equivalent" and discovering at delivery which one arrived.

A36 vs S235JR vs Q235B in Practice

One practical note on machining: all three grades are soft, gummy and prone to built-up edge. They cut easily but not cleanly, and a turned finish on A36 will never look like a turned finish on 4140. Where a drawing shows A36 but the part is a machined shaft with a tolerance to hold, the grade is usually wrong rather than the cutting data — the wider article on how the structural grades map across EN, GB and ASTM covers where the 250 MPa class stops being the right answer.

Typical Applications

• Base plates, anchor templates, embedded items and holding-down bolts

• Machine frames, skids, brackets and welded fabrications

• Stair stringers, handrails, ladders, walkway supports and grating frames

• Pipe supports, hangers, clamps and structural bolting components

• Truck and trailer parts, agricultural implement frames, drawbars

• General turning stock for low-stress pins, spacers, bushes and shafts

• Storage racking, shelving uprights and workshop furniture

Fabrication and Delivery Condition

A36 forges and welds without ceremony. No preheat is needed below roughly 25 mm in normal workshop conditions, and any standard E43 / E70 electrode or G3Si1 wire will match the base metal. The two things that catch fabricators out are distortion and galvanizing appearance. Thin sections move when welded because the steel is soft and the heat input is high relative to the section; and silicon at the top of the permitted range can leave a dull, patchy galvanized coating on bar that otherwise meets every mechanical requirement.

Delivery condition is worth stating explicitly on the order. As-rolled (+AR) bar is the normal supply and what most stock lists mean. Normalized (+N) bar gives a more uniform grain structure and is sometimes asked for when a part is to be machined after welding, but it also raises cost and lead time, and A36 does not require it. If a drawing specifies "A36 normalized", confirm that the normalization is genuinely needed — the requirement is often inherited from an old St37-2 note rather than from a design calculation.

Surface condition matters more on this grade than on an alloy bar. Hot rolled A36 carries mill scale, and forged bar carries a heavier oxide skin with possible laps at the edges. Where the bar is to be machined all over, none of that matters; where it is used as-rolled in a visible application, specify pickled, shot-blasted or peeled, and expect the price to move accordingly.

What We Do In-House

• Cutting, peeling, turning and centreless grinding to h9 / h11 on request

• Sawing to fixed length with end squareness checked before packing

• Normalizing and stress relieving with recorded furnace charts

• Spectrochemical analysis of every heat, samples retained for two years

• Tensile testing per heat; impact testing where the order calls for it

• Third-party inspection (SGS, BV, TUV) arranged at order stage

• Export packing: seaworthy wooden cases, strapped bundles, edge protection, certificates in the case

Frequently Asked Questions

Q1: Is A36 the same as S235JR?

A1: Functionally yes, on paper no. A36 guarantees 250 MPa yield against S235JR's 235 MPa, allows nearly 0.10 % more carbon, and carries no Charpy requirement at all. For a statically loaded structure in a mild climate the two behave the same way. For a welded, CE-marked job under EN 1090, the S235JR certificate is what the execution class expects — order that grade rather than A36 with an equivalence note.

Q2: Can A36 be heat treated to raise its strength?

A2: It can be normalized or stress relieved, and it will respond a little to normalizing, but it is not a through-hardening steel — carbon at 0.26 % maximum is not enough to form a hard martensite on quenching, and quench-and-temper would simply produce a distorted bar with unpredictable properties. If the part needs 700 MPa or a hardness figure, the grade is wrong; the answer is a 4140-type alloy steel, not a heat treatment on A36.

Q3: What certificate comes with the bar?

A3: EN 10204 3.1 as standard, showing ladle analysis and tensile results for the heat, signed by our inspection representative. A 3.2 certificate countersigned by an independent inspector, charpy results, grain size and ultrasonic inspection are all available but must be on the order — they cannot be added after the bar has been rolled.

Q4: Do you supply A36 in forged diameters?

A4: Yes, up to 500 mm. Above roughly 250 mm the bar is forged from ingot rather than rolled from billet, and forged A36 needs a reduction ratio agreed in advance if the part is safety-related. For heavy sections we normally recommend confirming the reduction ratio and the ultrasonic acceptance level together, since both are decided before the forging is made.

Request a Quote

Send the diameter, length, quantity, surface condition and the standard the certificate must reference — A36/A36M, S235JR or Q235B — and we will quote the grade that will actually pass inspection rather than the nearest stock item. Third-party inspection, cutting to length and export packing are quoted with the material.