GB/T Translated English of Chinese Standard: GB/T NATIONAL STANDARD OF THE

Transcription

1 Translated English of Chinese Standard: GB/T GB ICS H 44 NATIONAL STANDARD OF THE PEOPLE S REPUBLIC OF CHINA GB/T Replacing GB/T , GB/T , GB/T and GB/T Hot-rolled Steel Bars Dimensions, Shape, Weight and Tolerances 热轧钢棒尺寸 外形 重量及允许偏差 (ISO :1980, ISO :1980, ISO :1980, ISO :1980, MOD) Issued on: August 5, 2008 Implemented on: April 1, 2009 Issued by: General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ); Standardization Administration (SAC) of the People's Republic of China. Page 1 of 22

2 Table of Contents Foreword Scope Cross-sectional Shape Sectional Dimension, Weight and Tolerance Length and Tolerance Shape Marking Example Appendix A Page 2 of 22

3 Foreword Modification for the dimensions of round steel bars in this Standard adopts ISO :1980 "Hot-rolled Steel Bars - Part 1: Dimensions of Round Bars"; for the dimensions of square bars, it adopts ISO :1980 "Hot-rolled Steel Bars--Part 2: Dimensions of Square Bars; for the dimensions of flat bars, it adopts ISO :1980 "Hot-rolled Steel Bars - Part 3: Dimensions of Flat Bars"; and for the dimension tolerance of round steel bars, square bars, flat bars, hot-rolled hexagons and hot-rolled octagon steel, it adopts ISO :1982 "Hot-rolled Steel Bars--Part 4: Tolerances". The main technical differences between this Standard and ISO :1980 are as follows: The international standard has two diameter series of round steel bars, while this Standard has only one; For the diameter range of the round steel bars, this Standard extends it from 8mm~220mm of the international standard to 5.5mm~310mm. The main technical differences between this Standard and ISO :1980 are as follows: The international standard has two side length series of square bars, while this Standard has only one; For the side length range of the square bars, this Standard extends it from 8mm~120mm of the international standard to 5.5mm~200mm; This Standard does not specify the minimum diameter of the square bar fillet. The main technical differences between this Standard and ISO :1980 are as follows: The international standard has dimension series of flat bars, while this Standard has only one; As for the dimension range of the flat bars, the international standard has flat bars in width of 20mm~150mm and thickness in 5mm~50mm; while this Standard has flat bars in width of 10mm~200mm and thickness in 3mm~60mm. The main technical differences between this Standard and ISO :1982 are as follows:: For the application scope of this Standard, hot-rolled tool steel flat bars are added; Page 3 of 22

4 Add dimensional tolerance with hot-rolled round steel bars and square bars in sectional dimensions of 135mm, 145mm, 155mm, 165mm, 260mm, 270mm, 280mm, 290mm, 300mm and 310mm; The length tolerance of the round steel bars and square bars is not classified, and the provisions of this Standard are equivalent to L3-level of the international standard; Out-of-roundness of the round steel bars is more strict in this Standard than that specified in the international standard. This Standard replaces GB/T "Hot-rolled Round and Square Steel Bars - Dimension, Shape, Weight and Tolerance", GB/T "Dimensions, Shape, Weight and Tolerances for Hot-rolled Flats", GB/T "Hot-rolled Hexagonal and Octagonal Steel Bars - Dimensions, Shape, Weight and Tolerance" and GB/T "Dimensions, Shapes, Weight and Tolerances for Hot-rolled Tool Flat Steels". Compared with GB/T , GB/T , GB/T and GB/T , this Standard has the main changes as follows: Add hot-rolled round and square bars in sectional dimension of 135mm, 145mm, 155mm, 165mm and hot-rolled round steel bars in sectional dimension of 260mm, 270mm, 280mm, 290mm, 300mm and 310mm; Add dimensional tolerance and theoretical weight for the hot-rolled round and square bars in sectional dimension of 135mm, 145mm, 155mm, 165mm, 260mm, 270mm, 280mm, 290mm, 300mm and 310mm; Adjust usual length of the hot-rolled round steel bars; Add dimension, shape, weight and tolerance of the hot-rolled flat bars, hot-rolled hexagons, and hot-rolled octagon steel and hot-rolled tool steel flat bars; The width of the hot-roll flat bars is changed from 10mm~150mm to 10mm~200mm; and the thickness of the hot-rolled tool steel flat bars is changed from 6mm~100mm to 4mm~100mm; For the hot-rolled flat bars, add under-gauge length requirement and curvature requirement for width of more than 150mm. Appendix A of this Standard is normative. This Standard was proposed by China Iron & Steel Association. This Standard shall be under the jurisdiction of National Steel Standardization Technical Committee. Page 4 of 22

5 > In case of indicated in the contract made and entered into by and between the parties concerned, steel bars in length unspecified in the table may also be supplied; the cut or double length shall be indicated in the contract, and its length tolerance is +50mm (excluding hot-rolled flat bars). 4.6 The delivery volume of the steel bars in under-gauge length shall not exceed 10% of the total bars weight in that batch. 5 Shape 5.1 Hot-rolled Round and Square Bars The hot-rolled round and square bars are delivered in vertical bars, and they may be delivered in pony rolls in case of negotiated by and between the parties Out-of-roundness of the round steel bars and the diagonal line length of the square bars shall be in accordance with those specified in Table 9. The out-of-roundness of the round steel bars hereof refers to the difference between the maximum diameter and the minimum diameter of the same cross section. Table 9 Out-of-roundness of Hot-rolled Round Steel Bars and Diagonal Line Length of Square Bars In: mm Nominal diameter d of round steel bars Out-of-roundness Nominal side length a of the square bars Diagonal line length 50 50% of the nominal diameter tolerance < times of the nominal side length >50~80 65% of the nominal diameter tolerance times of the nominal side length >80 70% of the nominal diameter tolerance All of the specifications of the tool steel 1.29 times of the nominal side length The out-of-squareness of the square bars shall be on the same cross section; difference of any two sides shall not be greater than 50% of the nominal side length tolerance; difference of any two diagonal line lengths shall not be greater than 70% of the nominal side length tolerance The curvature of the hot-rolled round and square bar shall be in accordance with those specified in Table 10, the curvature groups shall be indicated in the corresponding product standard or purchase contract, and that unspecified in the contract complies with group 2. In case of indicated in the contract made and entered into by and between the parties concerned, the curvature not indicated in Table 10 may also be supplied. Page 11 of 22

6 Groups Table 10 Curvature of Hot-rolled Round and Square Bars Curvature Curvature per meter Total curvature in: mm Group % of the steel bar length Group % of the steel bar length The hot-rolled round and square bars shall not be significantly reversed The shearing slant on both ends of the hot-rolled round and square bars shall not be greater than 30% of the nominal diameter of the round steel bars and the nominal side length of the square bars, while the ends of the hot-rolled round and square bars shorn by shearing machine is allowed to be with local deformation. 5.2 Hot-rolled flat and hot-rolled tool steel flat bars The curvature of the hot-rolled flat bars shall be in accordance with those specified in Table 11, the curvature of hot-rolled tool steel flat bars and hot-rolled flat bar in width >150mm per meter shall not exceed 5mm, and the total curvature shall be not greater than 0.50% of the total length. The lateral curvature (rocker) shall not exceed 5mm per meter, and the total lateral curvature shall not be greater than 0.50% of the total length. Accuracy level Table 11 Curvature of Hot-rolled Flat Bars Curvature in: mm Curvature per meter Total curvature Group % of the steel bar length Group % of the steel bar length Note: For the flat hot rolled bar with width of >150mm, the curvature per meter is no greater than 5mm and the total curvature is no greater than 0.50% of the steel bar length The ends shall be shorn straightly, and the burr on both ends of the hot-rolled tool steel flat bars shall be removed, but burr in size of no greater than 5mm may be allowed to existing. The both ends of the hot-rolled tool steel flat bars shorn by contractor are allowed with local deformation; the shearing slant of the hot-rolled flat bar shall not be greater than those specified in the following: the hot-rolled flat bars with width of 100mm shall not be greater than 6mm, and that with width of >100mm shall not be greater than 8mm The hot-rolled flat and hot-rolled tool steel flat bars shall not be significantly reversed. The difference between the two diagonal line lengths of the hot-rolled tool steel flat bars on the same section shall not be greater than the width deviation of the flat bars, and the hot-rolled tool steel flat bars are allowed with blunt edges The cross-sectional shape of the hot-rolled flat and hot-rolled tool steel flat bars is Page 12 of 22

7 corresponding product standard or purchase contract. Table 14 Curvature of Hot-rolled Hexagon and Octagon Steel in: mm Groups Curvature per meter no greater than Total curvature no greater than % of the steel bar length % of the steel bar length % of the steel bar length Ends of the hot-rolled hexagon and octagon steel shall be shorn straightly, while the shearing slant length shall not be greater than 30% of the across flats distance of the steels, and the ends shorn by shearing machine are allowed with local deformation The hot-rolled hexagon and octagon steel shall not be significantly reversed. 6 Marking Example 6.1 Hot-rolled round, square bar, hexagon and octagon steel Round or square bars rolled by 40Cr steel with nominal diameter or side length of 50mm, and belonging to tolerance group 2, the marking is: 50 2 GB / T XX 40Cr GB / T XX round, square bars, hexagon and octagon steel 6.2 Hot-rolled Flat and Hot-rolled Tool Steel Flat Bars Hot-rolled hexagon and octagon steel rolled by 45 steel or hot-rolled (tool steel) flat bars in size of 10mm 30mm and belonging to group 2, the marking is: 22(10 30) 2 GB / T XX XX flat bars and tool steel flat bars 45 GB / T Note: The tool steel flat bars don t have groups. Page 14 of 22

8 Appendix A (Normative) Dimension and Theoretical Weight of Hot-rolled Steel Bar Table A.1 Dimension and Theoretical Weight of Hot-rolled Round and Square Bars Nominal diameter d of the round Theoretical weight Nominal diameter d of the round Theoretical weight steel bars and nominal side /(kg/m) steel bars and nominal side /(kg/m) length a of the square bars Round Square length a of the square bars Round Square /mm steel bars bars /mm steel bars bars Page 15 of 22

9 Table A.3 Dimension and Theoretical Weight of Hot-rolled Hexagon and Octagon Steel Across flats distance s/mm Sectional area A/cm 2 Theoretical weight /(kg/m) Hexagon steel Octagon steel Hexagon steel Octagon steel Note 2: The theoretical weight listed in the table is calculated by density of 7.85g/cm 3. Page 19 of 22

10 Calculation formula for the sectional area (A) shown in the table: Hexagon: Octagon: A S tg s A 2s tg s Where: n Side number of the n-regular-polygon; 1 2 A ns 4 tg The average central angle of the inscribed polygons: 360 / n Page 20 of 22