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Q/BQB 425-2014 English PDF (QBQB425-2014)

Q/BQB 425-2014 English PDF (QBQB425-2014)

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Q/BQB 425-2014: Hot dip galvanized steel sheet and strip

This Technical Conditions specifies the terms and definitions, classification and code, dimension, shape, technical requirements, inspection and test, packaging, marking and inspection documents of hot-dip aluminum-zinc alloy coated steel plates and steel strips. This Technical Conditions applies to hot-dip aluminum-zinc alloy coated steel plates and steel strips with a thickness of 0.22 mm ~ 2.0 mm produced by Baoshan Iron and Steel Co., Ltd., hereinafter referred to as steel plates and steel strips.
Q/BQB 425-2014
Supply Technical Conditions of Baoshan Iron and Steel Co., Ltd.
Hot-dip aluminum-zinc alloy coated steel plates and steel strips
Replacing Q/BQB 425-2009
1 Scope
This Technical Conditions specifies the terms and definitions, classification and code, dimension, shape, technical requirements, inspection and test,
packaging, marking and inspection documents of hot-dip aluminum-zinc alloy coated steel plates and steel strips.
This Technical Conditions applies to hot-dip aluminum-zinc alloy coated steel plates and steel strips with a thickness of 0.22 mm ~ 2.0 mm produced by Baoshan Iron and Steel Co., Ltd., hereinafter referred to as steel plates and steel strips.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 222-2006 Permissible tolerances for chemical composition of steel
products
GB/T 223 Methods for chemical analysis of iron, steel and alloy
GB/T 228.1-2010 Metallic materials - Tensile testing - Part 1. Method of test at room temperature
GB/T 232-1999 Metallic materials - Bend test
GB/T 1839-2008 Test method for gravimetric determination of the mass per unit area of galvanized coatings on steel products
Steel plates and steel strips are usually delivered after hot-dip (annealing) or hot-dip (annealing) and flattening.
7.4 Mechanical properties
7.4.1 Tables 6 and 7 specify the direction of the tensile specimen applies to steel plates and steel strips. The tensile specimen is the coated specimen. 7.4.2 For steel plates and steel strips of the grades DC51D+AZ and DC52D+AZ in Table 6 and steel plates and steel strips of all the grades in Table 7, it shall be ensured that the mechanical properties of steel plates and steel strips comply with the requirements of Tables 6 and 7 within 1 month from the date of completion of manufacture. For steel plates and steel strips of other grades in Table 6, it shall be ensured that the mechanical properties of steel plates and steel strips comply with the requirements of Table 6 within 6 months from the date of completion of manufacture.
NOTE. The date of issue in the product inspection document is usually specified as the date of completion of the manufacture of the product.
7.4.3 When steel plates and steel strips are supplied according to the specified parts, the supply and demand parties may agree on a range of mechanical properties that meet the processing needs of the part as the acceptance criteria. At this time, the mechanical properties specified in Tables 6 and 7 will no longer be used as the basis for delivery and acceptance.
7.4.4 Due to the influence of aging, the mechanical properties of steel plates and steel strips will deteriorate with the prolongation of storage time, such as the increase of yield strength and tensile strength, the decrease of elongation after break, formability deteriorates, tensile strain marks appear, etc. It is recommended that users use it as soon as possible.
7.5 Stretcher strain marks
7.5.1 The requirements for stretcher strain marks apply only to steel plates and steel strips with surface quality level FC.
7.5.2 The requirements for stretcher strain marks do not apply to steel plates and steel strips of the grades DC51D+AZ and DC52D+AZ in Table 6 and steel plates and steel strips of all the grades in Table 7.
7.5.3 For steel plates and steel strips of other grades specified in Table 6, stretcher strain marks shall not appear when used within 6 months from the date of completion of manufacture.
7.6 Coating adhesion
7.7.1 The available range of available coating mass is 30/30 g/m2 ~ 90/90 g/m2. 7.7.2 The recommended nominal coating masses are listed in Table 8. If the demand party has special requirements, other coating masses may be provided by agreement between the supply and demand parties.
NOTE. As the coating mass increases, the formability and weldability of the product may deteriorate. Therefore, when determining the coating mass, the formability requirements and weldability requirements during product processing shall be considered. 7.7.3 The average test value of the coating mass of the three points on each side shall not be less than the nominal coating mass of the corresponding surface. The test value of one single point shall not be less than 85 % of the nominal coating mass of the corresponding surface.
Table 8
Coating type Recommended nominal coating massa g/m2
Aluminum-zinc alloy coating 30/30, 40/40, 50/50, 60/60, 75/75, 90/90
a The coating thickness of 50 g/m2 hot-dip aluminum-zinc alloy coating is about 13.3 ??m. 7.8 Surface quality
7.8.1 There shall be no defects such as skipping coating, coating peeling and cracking on the surface of steel plates and steel strips.
7.8.2 The classification of steel plates and steel strips according to surface quality shall comply with the requirement of Table 9.
Table 9
Surface quality level Code Characteristics
Relatively advanced
finishing surface FB
The surface is allowed to have imperfections such as small zinc
particles, dents, scratches, pits, uneven color, black spots, streaks,
slight passivation spots, zinc undulations.
Advanced finishing
surface FC
The better side is allowed to have small imperfections such as
smooth dents, slight scratches, fine spangles, zinc undulations and
slight passivation spots. The other side is at least of the surface
quality FB.
7.8.3 For steel strips, the strip is allowed to be delivered with defects due to unwilling to cut the defective part, but the defective part shall not exceed 6 % of the total length of each coil.
7.9 Surface structure
The surface structure of steel plates and steel strips shall comply with the requirements of Table 10.
the contract. The supply party will not bear the corresponding product quality responsibility for surface defects such as black rust, scratches and friction marks generated during handling, storage and use of this type of product. 7.10.9 The available surface treatment options are as follows.
7.10.9.1 Chromic acid passivation (C) and chrome-free passivation (C5). This surface treatment reduces black rust on the surface of products during
transportation and storage. In the case of chromic acid passivation, there is a risk of frictional black spots on the surface. In the case of chrome-free passivation, the hexavalent chromium substances that are harmful to human health in the passivation film are restricted.
7.10.9.2 Chromic acid passivation + oiling (CO) and chromium-free passivation + oiling (CO5). This surface treatment further reduces black rust on the surface of products during transportation and storage. In the case of chrome-free passivation, the hexavalent chromium substances that are harmful to human health in the passivation film are restricted.
7.10.9.3 Ordinary fingerprint resistance (N) and chromium-free fingerprint resistance (N5). This surface treatment reduces black rust on the surface of products during transportation and storage, while the fingerprint resistant film improves the sweat and stain resistance of electronic or electrical products. The chrome-free fingerprint-resistant film restricts the hexavalent chromium substances that are harmful to human health.
7.10.9.4 Oiling (O). This surface treatment reduces black rust on the surface of products during transportation and storage. The rust preventive oil applied is generally not used as rolling oil and stamping lubricant for subsequent processing.
7.10.9.5 No treatment (U). The surface treatment without chemical passivation, oiling and application of fingerprint-resistant film, etc. This type of product tends to have surface defects such as white rust, scratches and friction marks that are easily generated during handling, storage and use.
8 Inspection and test
8.1 The appearance of steel plates and steel strips shall be visually inspected. 8.2 The dimension and shape of steel plates and strips shall be measured with suitable measuring tools. The thickness measurement portion is any point not less than 20 mm from the edge.
8.3 The tensile test shall be in accordance with Method B of GB/T 228.1. In Table A.5 Unit. mm
Specified minimum
yield strength
MPa
Nominal width
mm
Flatness at the following nominal thicknesses, mm
Ordinary precision PF.A Advanced precision PF.B
< 0.70 0.70 ~ < 1.60 1.6 ~ 3.0 < 0.70 0.70 ~ < 1.60
1.6 ~
3.0
< 260 < 1200 10 8 8 5 4 3 1200 ~ < 1500 12 10 10 6 5 4
A.4.3 For steel plates with a specified minimum yield strength of not less than 260 MPa and less than 360 MPa, and steel plates of grades DX51D+AZ and
S550GD+AZ, the maximum flatness tolerance shall comply with the
requirements of Table A. 6.
Table A.6 Unit. mm
Specified minimum
yield strength
MPa
Nominal width
mm
Flatness at the following nominal thicknesses, mm
Ordinary precision PF.A Advanced precision PF.B
< 0.70 0.70 ~ < 1.60 1.6 ~ 3.0 < 0.70 0.70 ~ < 1.60
1.6 ~
3.0
260 ~ < 360 < 1200 13 10 10 8 6 5 1200 ~ < 1500 15 13 13 9 8 6
NOTE. According to the shape and position of the steel plate, the strain type of the steel plate may be divided into the following categories.
Bow. Curving along all directions of the steel plate, either longitudinal (along the rolling direction) or transverse (perpendicular to the rolling direction);
Wave. Waves, rippling along the longitudinal direction of the steel plate; Edge wave. Waves along the edge of the steel plate;
Center buckle, centre fullness; full centre. Waves at the center of the steel plate, also known as center folds.
A.4.4 The width [Translator note. this may be ?€?flatness?€?] tolerance requirements stricter than PF.B may be negotiated at the time of ordering and indicated in the contract.
A.4.5 For steel plates with a specified minimum yield strength of not less than 360 MPa, the maximum flatness tolerance may be negotiated between the
supply and demand parties at the time of ordering.
A.4.6 When the user has adequately leveled the steel strip, the values specified in Tables A.7 and A.8 also apply to the steel plates cut from steel strips by the user.
Annex B
(normative)
Weight calculation method in the calculation of theoretical weight
B.1 Calculation method for nominal coating thickness.
Nominal coating thickness = [nominal coating mass (g/m2)/50 (g/m2)] ?? 13.3 ?? 10-3 (mm)
B.2 In the calculation of theoretical weight, the nominal dimension of the substrate is usually used.
B.3 When the thickness tolerance of the substrate is a symmetrical tolerance, the thickness used in the calculation of theoretical weight is the nominal thickness; when the thickness tolerance of the substrate is a defined negative deviation or a positive deviation, the thickness used in the calculation of theoretical weight is the average value of the maximum thickness allowed and the minimum thickness allowed.
B.4 The calculation method for the theoretical weight of steel plates shall comply with the requirements of Table B.1.
Table B.1
Calculation order Calculation method Rounding off of result
Basic weight of substrate
(kg/mm ?€? m2) 7.85 (weight of 1 mm thickness ?€? 1 m
2 area) ???
Unit weight of substrate
(kg/m2)
Basic weight of substrate (kg/mm ?€? m2) ??
(thickness - nominal coating thickness a) (mm)
Rounded off to 4
significant figures
Unit weight of steel plate
(kg/m2)
Unit weight of substrate (kg/m2) + nominal coating
thickness (kg/m2)
Rounded off to 4
significant figures
Steel
plate
Area of steel plate (m2) Width (mm) ?? length (mm) ?? 10-6 Rounded off to 4 significant figures Weight of a piece of
plate (kg) Unit weight of steel plate (kg/m
2) ?? area (m2) Rounded off to 3 significant figures
Weight of a bundle (kg) Weight of a piece of plate (kg) ?? number of steel plates of the same specification in a bundle Rounded off to the
integer value of kg
Total weight (kg) Addition of the weight of each bundle (kg) Integer value of kg

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