Q235: The Standard Mild Carbon Angle Grade
Q235 is a hot rolled mild carbon structural steel produced to GB/T 700, with a minimum yield strength of 235 MPa and a tensile range of 370 to 500 MPa. It is the default grade for angle iron in general construction because it combines adequate strength for secondary members, excellent weldability, and the lowest cost among structural grades. The B subgrade adds a guaranteed Charpy V-notch impact energy of 27 J at 20 degrees Celsius, which qualifies the steel for ordinary welded building structures.
Quality Indicators on the Bar Itself
A high-quality hot rolled angle bar has a consistent cross-section, straight legs, and a surface free of deep seams, cracks, and heavy scale. The ends are cut square, the leg and thickness dimensions fall within the tolerances of GB/T 706, and the weight per meter matches the theoretical table value within the allowed deviation. Visual inspection at receiving covers these points, and any doubt is resolved by measuring the dimensions and comparing them with the certificate.
What the Mill Certificate Must Show
The mill test certificate for Q235 angle steel should identify the standard, grade, and heat number, and report the chemical composition, yield strength, tensile strength, and elongation of the tested sample. For the B subgrade, the certificate also reports the Charpy V-notch impact energy. The certificate ties the delivered bars to the tested heat, and it is the document that the engineer and quality inspector check at material approval.
Size Range and Delivery Forms
Q235 angle bars are rolled from 20×20×3 mm to 200×200×24 mm in equal-leg sizes, with unequal-leg profiles from 25×16×3 mm to 200×125×16 mm, in lengths of 6 and 12 meters. Standard delivery is in bundles with painted end marks showing the size and grade, and bars can be supplied cut to length, with holes punched, or galvanized to the project specification. For large orders, sampling and testing can be arranged at the mill or at an independent laboratory.
Surface Treatment and Protection
Black angle bars are delivered with mill scale, and they are normally primed or painted soon after arrival to prevent rusting in storage. For outdoor and coastal service, hot-dip galvanizing to the applicable standard provides long-term protection, with vent and drain holes arranged before dipping. Where the bars are stored outdoors, they should be placed on dunnage with drainage, and the bundle strapping should be checked so that trapped water does not cause local corrosion.
Frequently Asked Questions
Q: What is the yield strength of Q235 angle steel?
Q235 has a minimum yield strength of 235 MPa and a tensile range of 370 to 500 MPa per GB/T 700.
Q: What should I check when receiving angle bars?
Check the dimensions, straightness, surface condition, end cuts, and the mill certificate against the order.
Q: What sizes are available?
Equal angles from 20×20×3 mm to 200×200×24 mm, plus unequal-leg sizes, in 6 and 12 meter lengths.
Q: Can Q235 angles be supplied galvanized?
Yes, hot-dip galvanizing is available, with vent and drain holes arranged before dipping.
Q: What documents come with the delivery?
Mill test certificates with heat number, chemical composition, and mechanical test results, plus packing lists.