Detail of GB/T 41747-2022

Introduction of GB/T 41747-2022

1 Scope This document specifies the dimensions, shape and weight, technical requirements, test methods, inspection rules, classification and designation, packaging, marking and quality certification of structural and high-strength continuous hot-dip galvanized thin steel sheets and strips produced by the double-spoke casting and rolling process of the substrate, and the content of the order. This document corresponds to the application of products for internal and external coverings and structural parts with requirements for corrosion resistance. This document applies to structural grade and high strength steel continuous hot-dip galvanized double-mixed cast and rolled thin steel sheets and strips of a thickness not greater than 2.0 mm (hereinafter referred to as "thin steel sheets and strips"). 2 Normative references The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, the date of the cited documents, only the date of the corresponding version applies to this document; do not note the date of the cited documents, the latest version (including all the revision of the list) applies to this document. 3 Terminology and definitions The following terms and definitions apply to this document. 3.1 Twin-roll cast steel sheet and strip Thin steel sheet and strip made by casting steel directly to a final thickness using a double-roll casting and rolling process and subsequently hot-rolled with a small press down. 3.2 Continuous hot-dip zinc-coated steel sheet and strip Products obtained by hot-dip plating of hot-rolled sheet and strip after descaling in a continuous galvanizing line, either by double-mix casting (3.1) or by subsequent cold-rolling of the sheet and strip. 3.3 Normal spangle coating A coating layer with an obvious zinc flower shape in which the zinc grains grow freely during the normal solidification process. Note; Normal spangle has a metallic lustre and is widely used. It can be supplied as a plating bar or N (see 8.5); however, it can be variable in appearance and is not suitable for decorative coating. and is not suitable for decorative painting. 3.4 Minimised spangle coating A small zinc spangle coating in which the zinc grains formed during the solidification process are artificially interrupted. Note: The surface appearance of the product may have some unevenness in the coating on individual rolls or between rolls. 4 Size, shape, weight 4.1 Thin steel sheets and strips are not thicker than 2.0 mm and not wider than 1 800 mm. 4.2 Thin galvanised steel sheets with a width of less than 900 mm may be cut from a wide sheet. 4.3 The thickness of thin steel sheets and strips is the sum of the thickness of the substrate and the plating. 4.4 The size, shape, weight and permissible deviation of thin steel sheets and strips should be in accordance with the provisions of GB/T25052. 5 technical requirements 5.1 The chemical composition of steel 5.1.1: The chemical composition of steel (melting analysis) should be consistent with the provisions of Table 1 and Table 2. 5.1.2 The allowable deviation of the finished steel composition should be consistent with the provisions of GB/T222. 5.2 Mechanical properties Structural grade, high strength grade thin steel plate and steel strip mechanical properties should be in accordance with the provisions of Table 3, Table 4 respectively. Unless otherwise specified, tensile specimens with plating specimens. 5.3 Plating 5.3.1 Plating weight The plating weight and the corresponding plating code shall conform to the provisions of Table 5. The weight of the coating refers to the total weight of the zinc layer on both sides of the thin steel plate, expressed in g/m2. The plating weight of a differentially thick plated steel plate shall be in accordance with the agreement between supply and demand. If the demander requires a maximum coating weight, this shall be specified in the order contract. 5.4 Welding properties Thin galvanised steel sheets are suitable for welding if a suitable welding method is selected and attention is paid to the use of heavily coated thin steel sheets. 5.5 Coating properties Hot-dipped galvanised double-rolled cast and rolled steel sheets and strips provide a good base coating for painting, but the initial treatment may be somewhat different from that on mild steel. Pre-treatment primers, chemical conversion films (chromate, phosphate or oxide types) and some specially formulated coatings for direct application to zinc surfaces are all suitable for the initial treatment of hot dip galvanised sheets. It is advisable to consider whether or not to passivate the hot-dip galvanised sheet ordered when drawing up the painting programme. 5.6 Surface treatment 5.6.1 Passivation Passivation of the galvanised layer reduces rusting (white rust) that occurs under wet storage conditions. However, the corrosion protection of this treatment is limited and hinders the adhesion of most coatings. 5.6.2 Phosphating Phosphating treatment enables various types of galvanised sheet steel and strip to be coated without further treatment (except for routine cleaning), which improves the adhesion and corrosion resistance of the coating and reduces the risk of corrosion starvation during storage and transportation. After phosphating with a suitable lubricant, the forming properties can be improved. 5.6.3 Oiling Oiling can reduce the wet storage conditions of the thin steel plate pounds Kuai, after passivation of the thin steel plate and steel strip and then oiling can further reduce the wet storage conditions of rust. The oil layer should be able to be removed with a degreaser that does not damage the zinc layer. 5.7 Surface quality 5.7.1 Sheet steel delivered in coils shall be free from delamination, surface cracks and other defects that are detrimental to the finished product or to the corresponding subsequent processing. 5.7.2 For thin steel strip, delivery with defects is permitted as there is no opportunity to remove the defective part, provided that the length of the defective part does not exceed 3% of the total length of the strip. For slit products delivery with defects is not permitted. 6 Test methods 6.1 The chemical composition of steel is generally tested according to GB/T4336, GB/T 20123, GB/T 20124, GB/T 20125 or other common chemical analysis methods, and in case of arbitration according to GB/T 223.12, GB/T 223.14, GB/T 223.18, GB/T 223.23, GB/T 223.26, GB/T 223.37, GB/T 223.37, GB/T 223.38. 223.37, GB/T 223.40, GB/T 223.60, GB/T 223.62, GB/T 223.63, GB/T 223.69, GB/T 223.72, GB/T 223.84 and GB/T 20125. 6.2 Each batch of thin steel plate and strip inspection items, the number of samples, sampling methods and test methods should be consistent with the provisions of Table 7. 6.3 Plating adhesion bending test specimen from the side edge of the distance should be not less than 25 mm. the minimum width of the specimen should be 50 mm. 7 test rules 7.1 The inspection and acceptance of thin steel plates and strips shall be carried out by the quality inspection department of the supplier. 7.2 Thin steel plates and strips should be accepted by batch, each batch should be the same grade, the same furnace number, the same specification and the same delivery state of steel composition. 7.3 Thin steel plates and strips of the re-inspection and determination rules should be consistent with GB/T 17505. 7.4 thin steel plate and steel strip of the test and check the measured value by comparing the revised value of the method of repair, repair rules should be consistent with the provisions of GB/T8170. 8 classification and code 8.1 Grade naming methods 8.1.1 General Sheet steel and steel strip grades by the use or characteristics of steel code, steel grade code, steel characteristics, hot plating code (D) and plating type code, which hot plating code (D) and plating type code between the "+" connection. 8.1.2 Steel use code 8.2 Examples of grade designations Example 1; SU390GD+Z Indicates a structural steel with a specified minimum yield strength of 390 MPa, pure zinc plated and hot plated. Example 2: HU460IAD+Z Indicates a product type of high strength steel with a specified minimum yield strength of 460 MPa, pure zinc plated and hot plated. See Appendix C for a comparison of similar grades. 8.3 Grades and steel properties Sheet steel and steel strip grades and steel characteristics should be consistent with the provisions of Table 8. 9 packaging, marking and quality certification The packaging, marking and quality certification of thin steel plates and strips should be in accordance with the provisions of GB/T 247. If the demander has special requirements for the packaging, it can be negotiated at the time of order. 10 Order content At the time of ordering, the following information shall be provided by the customer and stated in the contract: a) The document number; b) Name of the product c) Grade; d) type of coating and coating weight code. e) dimensions and their accuracy (including thickness, width, length, inner diameter of the strip, etc.); f) Surface treatment g) weight h) Packaging method; i) Special requirements. Appendix A (informative) Structural changes in this document compared to ISO 15211:2012 Appendix B (Informative) Technical differences between this document and ISO 15211:2012 and the reasons for them Appendix c (informative) Comparison table of approximate grades

Contents of GB/T 41747-2022

1 Scope 2 Normative references 3 Terminology and definitions 4 Size, shape, weight 5 technical requirements 6 Test methods 7 test rules 8 classification and code 9 packaging, marking and quality certification 10 Order content Appendix A (informative) Structural changes in this document compared to ISO 15211:2012 Appendix B (Informative) Technical differences between this document and ISO 15211:2012 and the reasons for them Appendix c (informative) Comparison table of approximate grades