Detail of Q/BQB 408-2019

Introduction of Q/BQB 408-2019

This standard is developed in accordance with the rules given in G/T 1.1-2009 Directives for standardization - Part 1: Structure and drafting of standards. This standard is prepared with reference to JIS G 3141: 2017, EN 10130: 2006, and JFS A 2001: 2014. This standard replaces Q/BQB 408-2018. The following main changes have been made with respect to Q/BQB 408-2018: ——the expression of special control requirements for roughness is added; ——the comparison table between similar designations in this standard and relevant Chinese and foreign standards in Annex C is revised; Annex A to this standard is normative and Annexes B and C are informative. This standard was proposed by the Manufacturing Management Department of Baoshan Iron & Steel Co., Ltd. This standard is under the jurisdiction of the Manufacturing Management Department of Baoshan Iron & Steel Co., Ltd. This standard was drafted by the Manufacturing Management Department of Baoshan Iron & Steel Co., Ltd. Drafters of this revision are: Min YUAN and Mingxi MAO. The previous editions of this standard are as follows: Q/BQB 408-1988, Q/BQB 408-1994, Q/BQB 408-1999, Q/BQB 408-2003, Q/BQB 408-2009, Q/BQB 408-2014, and Q/BQB 408-2018. Low carbon cold-rolled steel sheet and strip for cold forming 1 Chemical composition Table 4 Designation Chemical compositiona (heat analysis), % (mass fraction) C Mn P S Alt SPCC\SPCC-Xb ≤0.15 ≤0.60 ≤0.10 ≤0.025 - SPCD ≤0.10 ≤0.45 ≤0.030 ≤0.025 ≥0.015 SPCE ≤0.08 ≤0.40 ≤0.025 ≤0.020 ≥0.015 SPCF ≤0.08 ≤0.30 ≤0.020 ≤0.020 ≥0.015 SPCG ≤0.06 ≤0.25 ≤0.020 ≤0.020 ≥0.015 a Addition of other alloying elements is permitted. b SPCC-X is a specific designation. Table 5 Designation Chemical composition (heat analysis), % (mass fraction) C Mn P S Alt Ti DC01a ≤0.10 ≤0.50 ≤0.035 ≤0.025 ≥0.015 - DC03a ≤0.08 ≤0.45 ≤0.030 ≤0.025 ≥0.015 - DC04a ≤0.08 ≤0.40 ≤0.025 ≤0.020 ≥0.015 - DC05 ≤0.008 ≤0.30 ≤0.020 ≤0.020 ≥0.015 ≤0.20b DC06 ≤0.006 ≤0.30 ≤0.020 ≤0.020 ≥0.015 ≤0.20b DC07 ≤0.006 ≤0.25 ≤0.020 ≤0.020 ≥0.015 ≤0.20b a Addition of Nb and/or Ti is permitted. b It is allowed to replace part of Ti with Nb, and the total content of Nb and Ti shall not be greater than 0.20%. Table 6 Designation Chemical composition (heat analysis), % (mass fraction) C Mn P S Alt Ti BLCa ≤0.10 ≤0.50 ≤0.035 ≤0.025 ≥0.015 - BLDa ≤0.08 ≤0.45 ≤0.030 ≤0.025 ≥0.015 - BUSD ≤0.010 ≤0.40 ≤0.025 ≤0.020 ≥0.015 ≤0.20b BUFD ≤0.008 ≤0.30 ≤0.020 ≤0.020 ≥0.015 ≤0.20b BSUFD ≤0.006 ≤0.30 ≤0.020 ≤0.020 ≥0.015 ≤0.20b a Addition of Nb and/or Ti is permitted. b It is allowed to replace part of Ti with Nb, and the total content of Nb and Ti shall not be greater than 0.20%. 2 Mechanical properties Table 7 Designation Tensile test Yield strength a, b, c MPa Tensile strength MPa ≥ Percentage elongation after fracturec A50mm % ≥ rmd, e ≥ Nominal thickness, mm Nominal thickness, mm <0.25 0.25~<0.30 0.30~<0.40 0.40~<0.60 0.60~<1.0 1.0.~<1.6 ≥1.6 0.5~1.0 >1.0~1.6 SPCC — 270 25 28 31 34 36 37 38 — — SPCD 140~220 270 27 30 33 36 38 39 40 — — SPCE 130~200 270 29 32 35 38 40 41 42 — — SPCF 120~190 270 — — 37 40 42 43 44 — — SPCG 110~180 270 — — — 42 44 45 46 1.5 1.4 a RP0.2 is adopted if the yield phenomenon is not obvious, otherwise, ReL is adopted. b In addition to SPCC steel, if the thickness is greater than 0.40 mm but not greater than 0.60 mm, the specified value for yield strength is allowed to increase by 20 MPa. For thickness not greater than 0.40 mm, the value is allowed to increase by 40 MPa. c No. 5 specimen specified in JIS Z 2241 is adopted, and the specimen is in longitudinal direction. d When the thickness is < 0.5 mm or >1.6 mm, no requirements are made on the value of r. e rm = (r90 + 2r45 + r0) ∕ 4.

Contents of Q/BQB 408-2019

Foreword i 1 Chemical composition 2 Mechanical properties 3 Inspection and test 4 Annex