GB/T 1228 Heavy Hex Structural Bolts (EN 14399-3 HR)

This is the GB/T 1228 heavy hex structural bolt product page. GB/T 1228 is the Chinese standard for heavy hexagon head high-strength bolts used in structural steelwork — a high-strength bolt with an enlarged across-flats head (single piece). DIN 6914 (German) and ISO 7412 (international) are the same-family heavy hex bolt standards, registered as equivalents in our standard-alias registry.

Relationship to EN 14399: EN 14399 is a European standard for high-strength structural bolting assemblies for preloading — a set of bolt + nut + washer, not a single bolt. It consists of several parts (e.g. -3 HR hexagon bolt and nut assemblies, -4 HV, -10 HRC calibrated-preload tension-control bolts). EN 14399-3 (System HR) covers hexagon bolt and nut assemblies whose bolt dimension system matches the GB/T 1228 heavy hex bolt. We supply single pieces to GB/T 1228, with set requirements confirmed per drawing, and we do not claim to provide EN 14399-certified complete connection sets. For non-preloaded connections, see EN 15048 non-preloaded structural bolting assemblies.

Why preloaded sets must be matched: a preloaded joint is tightened by stretching the bolt to create preload, which requires the bolt, nut and washer to be matched from the same batch with a consistent torque coefficient — mixing bolts and nuts from different batches or suppliers scatters the torque coefficient and makes the preload uncontrollable. This is the single most important point for buyers. We supply single pieces; if you need a complete assembly (same-batch matching, consistent torque coefficient), confirm it per project and drawing.

Sizes made to order cover M12–M30 (partially threaded, all property class 10.9S); alloy steel, black oxide finish. M36 and class 8.8 are not covered, and unlisted sizes are quoted to your drawing. For general-purpose hex bolts, see GB/T 5783 / DIN 933 hex bolts.