Specifications

Nominal composition of common grades

Phosphorus and sulphur limits, and the full A105 requirements, are given in each standard; see the carbon steel flanges page for the A105 table. Actual values for each heat are shown on the mill test certificate.

Choosing the grade

ASTM A105 bars are used where the finished part is a pressure-retaining forging, such as a flange, fitting, valve body or nozzle machined from bar, so that the material carries the same specification as forged A105 parts. A350 LF2 is used for the same parts in low-temperature service, with impact testing at −46 °C.

AISI 1018 and 1020 are low-carbon steels with good machinability and weldability, used for pins, spacers, bushes, light shafts and parts that are case hardened. AISI 1045, C45 and EN8 are medium-carbon steels with higher strength, used for shafts, axles, spindles, studs, gears and machine parts; they can be flame or induction hardened for wear resistance. IS 2062 and A36 are structural grades for anchor bolts, tie rods and general fabrication.

Black and bright bars

Black bars are supplied as hot rolled or forged, with mill scale on the surface and wider diameter tolerances; they are used where the bar will be fully machined or forged. Bright bars are peeled, turned, ground or cold drawn to a clean surface and a close diameter tolerance, which reduces machining and allows the bar to be used directly for shafts and pins. Cold-drawn bars also gain some strength from the drawing. Please state the tolerance class required – such as h9, h10 or h11 – and any straightness requirement.

How we manufacture round bars

We manufacture carbon steel round bars from certified billets and bars. Black bars are hot rolled or forged to size and, where specified, normalised to refine the grain. Bright bars are produced from black bars by peeling or turning to remove the scale and decarburised layer, followed by straightening and, for close tolerances, centreless grinding and polishing. Bars are cut to length, marked with grade and heat number, and inspected for diameter, straightness and surface before dispatch. Ultrasonic testing is carried out on request to check for internal defects, especially for bars that will be machined into pressure parts.

Machining and heat treatment

Low-carbon grades machine freely in the as-rolled or cold-drawn condition. Medium-carbon grades such as 1045 and EN8 are often supplied normalised for machining and then hardened and tempered, or surface hardened, after machining. A105 bars for pressure parts are machined in the as-supplied or normalised condition; any heat treatment required by ASTM A105 for the finished part should be stated in the order. For welding medium-carbon bars, preheat may be needed to avoid hard zones and cracking.

Ordering carbon steel round bars

Please give the grade and standard, diameter and tolerance, black or bright condition, heat treatment, length (random or cut length), quantity, and any ultrasonic testing or inspection requirement. Bars are bundled and strapped, with bright bars protected by rust-preventive oil and wrapping, and each bundle is tagged with grade, size and heat number.

Applications and related products

Carbon steel round bars are used for flanges and fittings machined from bar, valve bodies and stems, shafts and axles, pins and bushes, studs and bolts, hydraulic cylinder parts, couplings and general engineering components. Matching products include carbon steel flanges, carbon steel pipe fittings and carbon steel fasteners, as well as carbon steel seamless pipes, carbon steel ERW pipes and carbon steel plates. Other bar materials are on the round bars, rods and wires page, and grade guidance on the carbon steel page.