GB/T 3632-2008 Torsion-Shear High-Strength Bolting Assemblies (M16–M30)

This is the GB/T 3632 torsion-shear high-strength bolting assembly product page. GB/T 3632-2008 is the Chinese standard for the twist-off (tension-control) assembly used in structural steelwork — one torsion-shear bolt with a spline end, one large hexagon nut and one plain washer, matched from the same batch, supplied and tested as a set. Sizes covered by the standard: M16–M30.

A torsion-shear assembly reaches its preload by having the spline end twisted off. The tightening axial force is taken as the peak recorded on the load cell at the moment the spline end shears (clause 6.5.4 of GB/T 3632-2008). Installation therefore needs no torque wrench and no on-site torque-coefficient measurement — the tool keeps turning until the spline end breaks. A large hexagon assembly to GB/T 1231 works the opposite way, by the torque-control method: the assembly is supplied with a guaranteed torque coefficient (K = 0.110–0.150, coefficient of variation VK ≤ 0.077) and the final tightening torque is calculated with the measured K of the batch actually delivered. Both are preloaded assemblies for steel structures; the difference is how the preload is reached on site.

Assembly composition and performance: one bolt + one nut + one washer per set; bolt property class 10.9S (materials 20MnTiB / ML20MnTiB up to M24, and 35VB / 35CrMo for M27 and M30), nut class 10H, washer hardness 329HV30–436HV30 (35–45 HRC). Batch tightening axial force follows Table 12 of the standard — for example M20 nominal 171 kN (range 155–188 kN) and M24 nominal 248 kN (range 225–272 kN), with batch standard-deviation limits of 15.5 kN and 22.5 kN respectively. Thread tolerance bands: bolt 6g, nut 6H.

Sizes made to order cover M16–M30 (M16, M20, M22, M24, M27, M30 — six diameters, 114 listed SKUs), lengths about 40–220 mm; alloy steel, black oxide, supplied per set. Sizes below M16 are not covered, and unlisted diameters and lengths are quoted to your drawing. For large hexagon assemblies under the torque-control method see GB/T 1231 high-strength large hexagon bolting assemblies, and for single-piece bolts see the GB/T 1231-2024 page (formerly GB/T 1228-2006, withdrawn and merged into GB/T 1231-2024).

International standard relationships are entry points for buyers only: the corresponding part in the European series is EN 14399-10 (System HRC, calibrated-preload tension-control assemblies). Our alias registry does not register GB/T 3632 as equivalent to it, and we claim no third-party certification. On an inquiry quoting that standard number we supply complete sets to GB/T 3632 and confirm dimensions and classes item by item against your drawing.