Cold Drawn Square Steel – Sizes, Grades and Tolerances

We draw square steel bar from 4×4 up to 120×120 mm on our 8-ton to 120-ton cold drawing lines. Compared to hot rolled square bar, the cold drawn version holds a tighter section, sharper corners, and a clean bright surface. If your part is cut or machined from square stock, this is the bar that keeps your blanks consistent from bundle to bundle.

Available sizes and grades

What buyers use it for

Square cold drawn bar is used for construction machinery pins, wear parts, keys, guide bars, and automation frames. The straightness and consistent section matter more here than in round bar because square blanks are often stacked, machined, or welded into assemblies where a wobbly bar shows up immediately.

What to specify when you ask for a quote

Send us the section size (width × width), the grade, and the quantity in tons. If you need a specific corner condition, machined ends, or a special length, add it to the order notes. Standard sizes ship from stock in 3–7 working days; custom runs 15–35 days depending on the heat schedule.

Request a quote: send us your square bar size, grade and quantity via the contact form, or check our cold drawn steel size guide for reference. We reply with price and lead time within one working day.

Related pages: Cold Drawn Flat Steel · Cold Drawn vs Hot Rolled · About Our Factory

Strength Grades on Square Bar

Square bar is available from structural grades up to hardenable alloy grades, and the grade is the main driver of price and performance. Q235 yields at 235 MPa – a general structural grade for keys, spacers and lightly loaded parts. Q275 and Q345B (S275JR / S355JR equivalents) step up the yield to 275 MPa and 345 MPa for load-bearing sections. 45# is a medium-carbon grade yielding around 355 MPa with 600–800 MPa tensile, used where strength and wear resistance are needed without heat treatment. 40Cr and 42CrMo are alloy grades for parts that are quenched and tempered to 28–40 HRC after machining. If the part is hardened, the grade choice is decided by the required core strength and case hardness, not by the section.

Square Bar Under Load

A square section carries load differently than a round one: the flat faces distribute bearing load evenly and give a larger contact area than a round bar of the same cross-section. That is why square bar is the standard for construction machinery pins, guide bars and sliding wear parts – the load sits on a flat face, not on a line contact. The drawn tolerance also matters here: a consistent section means predictable contact and even wear across the length of the bar.

Hardening Alloy Square Bar

When the part must take wear or impact, 40Cr and 42CrMo square bar is drawn to size and then quenched and tempered at your end or ours. The drawn bar machines cleanly in the annealed or as-drawn condition, then hardens to a uniform case after the finished part is machined. Because the drawn surface is scale-free and dimensionally consistent, hardening distortion is easier to predict than on hot rolled stock. Tell us the final hardness target and we confirm the grade and condition that gets you there.

Corner and Edge Condition

Square bar corners are the dimension that hot rolling cannot control well. Rolling rounds the corners, which makes a rolled square unreliable where the corner is part of the fit – a keyway, a guide groove, a vise datum. Drawing brings the corners to a sharp 90° ± 0.5° and keeps them consistent along the bar. If the part seats against the corner or uses it as a reference, specify the corner condition at ordering; we confirm the achievable radius before production.

Machining High-Strength Square

Machining advice follows the grade. Q235 and Q275 cut freely with standard tooling. Q345B and 45# need slightly heavier feed and a positive rake insert, but no special coolant. 40Cr and 42CrMo in the as-drawn condition machine well; after hardening, plan finishing passes with carbide tooling. If the square is fed to a CNC, the sharp corners and straight sides give a stable datum in the vise or feeder – the bar seats once and every face references the same corner.

Common Questions About High-Strength Cold Drawn Square Bar

What grades are available? Q235, Q275, Q345B, 45#, 40Cr, 42CrMo, 65Mn, plus your specified grade. Structural grades ship from stock; alloy grades are drawn to order against heat availability.

Can you supply hardened square bar? We supply 40Cr and 42CrMo as drawn or annealed for machining, and can arrange quenched and tempered delivery at your specified hardness. Tell us the target HRC and we confirm the route.

What corner tolerance can you hold? 90° ± 0.5° across the drawn length, which suits keyways and guide grooves that seat against a sharp corner.

Do you provide mill certificates? Yes, EN 10204 3.1 per batch, with third-party inspection arranged on request.

What is the MOQ? 500 kg per size, combined across a mixed order. Stock sizes ship within 3–7 working days.

Can you cut square bar for machining blanks? We cut to length with ±2 mm tolerance and deburr the ends, so bars arrive ready for the saw or CNC line.

Where High-Strength Square Bar Is Specified

Construction machinery pins. Excavator and loader pins are typical 40Cr or 42CrMo square bar jobs: the bar is drawn to the pin blank size, machined, then quenched and tempered to 28–38 HRC. The drawn tolerance means the blank is already straight and to size, so the pin length is the only critical cut. Common blanks are 25×25, 30×30, 40×40 and 50×50 mm, depending on the machine model.

Guide bars and rails in automation. Square drawn bar in Q345B or 45# runs as guide bars in pick-and-place units, sliding tables and press feeding systems. The flat faces slide against linear bearings or bronze bushings, and the h11 section tolerance keeps the slide clearance predictable over long runs. Straightness ≤ 0.5 mm/m means a 3 m guide bar needs no corrective machining before mounting.

Keys and key stock. Square bar is cut directly into parallel keys. The sharp 90° corners are the working surfaces – they seat fully in the keyway and stop the key from rocking under torque reversal. Q235 and Q275 cover most key applications; for heavily loaded shafts, 45# or 40Cr is specified and the key is hardened after cutting.

Wear strips and slide blocks. 65Mn square bar serves spring and wear applications, while 40Cr wear strips are hardened after machining. Both are supplied as drawn for machining, with the hardening done at your end or arranged by us at a specified HRC.

Inspection and Certificates

Each lot is checked on the drawing line for section size, corner angle, straightness and surface defects before cutting. Orders can carry an EN 10204 3.1 mill test certificate with chemical composition and mechanical properties, and third-party inspection such as SGS is arranged on request. Hardened deliveries include hardness test reports against the target HRC range.