GB /T 16270-1996 High Strength Structural Steel Heat Treatment and Rolling Steel Plate and Belt Grades and Chemical Composition
This standard applies to high strength quenching and tempering structural steel (hereinafter referred to as steel plate and steel belt) hot rolling, controlled rolling or normalizing plate, belt and its chemical composition.
The steel grades covered by this standard are Q460, Q500, Q550, Q620 and Q690 whose yield strength q of the steel plate and steel belt shall not be less than 460 N/mm2, 500 N/mm2, 550 N/mm2, 620 N/mm2, 690 N/mm2 respectively.
The comprehensive chemical composition of the steel plate and belt shall meet the requirements of Table 1. The total content of various non-metallic inclusions in the steel plate and steel belt shall not exceed the specified values in Table 2.
The low deoxidation mineral component of the steel plate and belt should not exceed the value specified in Table 3.
The values of sulfur, phosphorus and copper indexes for steel plate and belt shall meet the requirements of Table 4.
The results from the mechanical properties of the steel plate and belt shall meet the requirements of Table 5.
Superscript numbers in the heading of Table 1 and Table 2 are for identification of the component units of the table.
Table 1 Chemical composition of steel plate and belt（%） Grade C Si Mn P S Cu Q460 0.10-0.22 ≤0.50 1.50-2.60 ≤0.030 ≤0.020 ≤0.25 Q500 0.15-0.25 ≤0.55 1.70-2.60 ≤0.030 ≤0.020 ≤0.25 Q550 0.20-0.30 ≤0.60 1.80-2.70 ≤0.030 ≤0.020 ≤0.30 Q620 0.25-0.35 ≤0.60 1.90-3.00 ≤0.030 ≤0.020 ≤0.30 Q690 0.30-0.40 ≤0.65 2.00-2.50 ≤0.030 ≤0.020 ≤0.30
NOTE：
1 The total content of non-metallic inclusions in the steel plate and belt shall not exceed the specified values.
Table 2 Non-metallic inclusions and total content（mass fraction %） Grade Al N O2OFE Q460 0.011 0.012 0.0160.025 Q500 0.009 0.011 0.0130.020 Q550 0.008 0.009 0.0110.015 Q620 0.007 0.008 0.010 0.010 Q690 0.006 0.007 0.009 0.009
Table 3 The content of various low-deoxidation mineral components in steel plate and belt (mass fraction %) Grade AlN O2 TOTAL Q460 0.03 0.02 0.12 Q500 0.025 0.015 0.09 Q550 0.02 0.01 0.07 Q620 0.01 0.005 0.05 Q690 0.008 0.004 0.04
Table 4 Requirements of sulfur, phosphorus and copper indexes Grade S P Cu Q460 ≤0.035 ≤0.025 ≤0.25 Q500 ≤0.035 ≤0.025 ≤0.25 Q550 ≤0.035 ≤0.025 ≤0.30 Q620 ≤0.035 ≤0.025 ≤0.30 Q690 ≤0.035 ≤0.025 ≤0.30
Table 5 Mechanical properties of steel plate and belt Grade Rp0.2（MPa） Rm（MPa） Q460 ≥630 ≥760 Q500 ≥700 ≥880 Q550 ≥770 ≥980 Q620 ≥850 ≥1050 Q690 ≥920 ≥1130
Table 6 Heat treatment symbols of steel plate and belt Grade Heat treatment symbols Q460 BBR HR Q500 BBR HR Q550 BBR HR Q620 BBR HR Q690 BBR HR
