Hot-rolled Hexagonal Steel and Octagonal Steel (GB/T705-1989)
Hexagonal steel and octagonal steel are components produced through hot rolling. Hot-rolled hexagonal steel and octagonal steel are carbon-structural steel, which are mainly used in mechanical structure parts and fasteners. The standard of the hot-rolled hexagonal steel and octagonal steel is GB/T705-1989, which was released in 1989 by the Standardization Administration of China (SAC). The scope of application of the standard covers carbon-structural hot-rolled hexagonal steel and octagonal steel products of grade Q215, Q235, and Q275.
Hexagonal steel and octagonal steel mainly for mechanical structure parts and fasteners have relatively high strengths and good plasticity, low cold-bend rate and good mechanical properties. The microstructure of hot-rolled hexagonal steel and octagonal steel mainly consists of ferrite, bainite and a small amount of pearlite. Hot-rolled octagonal steel and hexagonal steel are mainly used in machinery manufacturing, transportation tools, construction and other industries areas. They are mainly used for manufacturing machinery parts, general machinery parts and so on.
Hot-rolled hexagonal steel and octagonal steel are hot-rolled shaped steel whose cross-sectional area is a regular hexagon or octagon. Hot-rolled hexagonal steel and octagonal steel are mainly divided into two categories by their grades: Q215 and Q235. The chemical composition of the two steels is shown in Table 1.
Table 1 Chemical composition of hexagonal steel and octagonal steel
Steel Grade C Si Mn P S Q215 ≤0.20 ≤0.35 ≤1.40 ≤0.045 ≤0.045 Q235 ≤0.22 ≤0.35 ≤1.80 ≤0.045 ≤0.045
The mechanical properties of the steel shall conform to the requirements of Table 2.
Table 2Mechanical properties of hexagonal steel and octagonal steel
Steel Grade Elongation (%) Yield Strength (MPa) Tensile Strength (MPa) Q215 ≥30 ≥205 ≥330 Q235 ≥24 ≥225 ≥370
Hot-rolled hexagonal steel and octagonal steel products shall have superior surface conditions and good internal quality. The surface roughness of the steel should conform to the requirements of the finishing (the minimum surface roughness Ra shall not exceed 1.6 μm). The surface inspections of the hexagonal and octagonal steel shall conform to the requirements of level S2 as stipulated in GB/T912-1989, which specifies the standards of steel surface quality. In addition, higher requirements shall be met with regard to the shape and dimension of the components.
The hot-rolled hexagonal steel and octagonal steel products should be inspected and accepted before dispatch. The type and number of the components to be inspected shall be decided in accordance with the relevant provisions of GB/T2975-1998. The controlling method for the inspection and acceptance of hot-rolled hexagonal steel and octagonal steel is GB/T2975-1998. The inspection and acceptance should be conducted in accordance with the acceptance criteria specified in the GB/T2975-1998.
To conclude, the standard of the hot-rolled hexagonal steel and octagonal steel is GB/T705-1989 released in 1989 by the Standardization Administration of China. The scope of application of the standard covers carbon-structural hot-rolled hexagonal steel and octagonal steel products of grade Q215, Q235, and Q275. The components for mechanical structure parts and fasteners have relatively high strengths and good plasticity, low cold-bend rate and good mechanical properties. The inspection and acceptance of hot-rolled hexagonal steel and octagonal steel should be conducted in accordance with the provisions of GB/T2975-1998.
