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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 908-2008 Forged bars - Dimensions, shape, weight and tolerances. The following main changes have been made with respect to GB/T 908-2008:
——The maximum nominal diameter of round bars is increased from 400 mm to 1,000 mm, and the maximum nominal side length of square bars is increased from 400 mm to 1,000 mm, and the dimension tolerances are specified correspondingly (see Table 1; Table 1 of Edition 2008);
——The maximum nominal thickness and the maximum nominal width of flat bars are increased from 160 mm to 800 mm and from 300 mm to 1,500 mm respectively, and the dimension tolerances are specified correspondingly (see Table 2; Table 2 of Edition 2008);
——The requirements for dimensions, shape and tolerances of polished round bars are added (see Table 1);
——The requirements for dimensions, shape and tolerances of the machined bars are added (see Table 3);
——The requirements for curvature of bars are tightened (see 4.4; 2.5 of Edition 2008);
——The delivery requirement of sawing at both ends of bars and requirements for cutting obliquity of bars are added (see Table 5);
——The labeling examples are deleted (see clause 4 of Edition 2008);
This standard was proposed by China Iron and Steel Association.
This standard is under the jurisdiction of SAC/TC 183 National Technical Committee on Iron and Steel of Standardization Administration of China.
The previous editions of this standard are as follows:
——GB/T 908-1972, GB/T 908-1987 and GB/T 908-2008;
——GB/T 16761-1997.
Forged bars - Dimensions, shape, weight and tolerances
1 Scope
This standard specifies the cross-section shapes, cross-sectional dimensions, weight and tolerances, length and tolerances and shape of forged bars (round bars, square bars and flat bars).
This standard is applicable to forged round bars with a diameter of 40 mm~1,000 mm, forged square bars with a side length of 40 mm~1,000 mm, and flat bars with a thickness of 20 mm~800 mm and a width of 40 mm~1,500 mm.
2 Classification
Forged bars are classified into the following three categories by the surface condition at the time of delivery:
a) Hot forged bars: commonly known as black skin, which is delivered with original surface (or treated by pickling and sandblasting).
b) Polished bars: round bars whose surfaces are treated by grinding and which are delivered with a surface having metallic luster.
c) Machined bars: bars whose surfaces are treated by milling and which are delivered with a surface having metallic luster.
3 Cross-sectional shape
3.1 The cross-sectional shapes of forged round bar and square bar are shown in Figure 1.
Figure 1 Cross sections of forged round bar and square bar
3.2 The cross-sectional shape of forged flat bar is shown in Figure 2.
Figure 2 Cross section of forged flat bar
4 Sectional dimensions, weight and tolerances
4.1 Dimension and weight
4.1.1 The dimensions and theoretical weights of forged round bar and square bar shall meet the requirements of Annex A, Table A.1.
4.1.2 The dimension and theoretical weight of forged flat bar shall meet the requirements of Table A.2.
4.1.3 The theoretical weights of forged bars with dimensions exceeding the nominal dimensions specified in Tables A.1 and A.2 shall be determined through negotiation between the Supplier and the Demander.
4.1.4 Forged bars are generally delivered by actual weight. By mutual agreement between the Supplier and the Demander and specified in the contract, they may also be delivered by theoretical weight.
4.2 Dimension tolerance
4.2.1 Hot forged bar
4.2.1.1 The dimensions and tolerances of hot forged round bar and square bar shall meet the requirements of Table 1. The dimension tolerance groups shall be indicated in corresponding product standards or order contracts. Otherwise, those specified in Grope 2 shall prevail.
Table 1 Dimension tolerances of hot forged round bar and square bar In: mm
4.2.1.2 The dimension and tolerance of hot forged flat bar shall meet those specified in Table 2. The dimension tolerance groups shall be indicated in corresponding product standards or order contracts. Otherwise, those specified in Grope 2 shall prevail.
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Table 2 Dimension and tolerance of hot forged flat bar In: mm
4.2.1.3 By mutual agreement between the Supplier and the Demander and specified in the contract, hot forged bars all with a positive deviation in dimension may also be supplied. And the tolerance shall be the sum of the absolute values of the positive and negative deviations as specified in corresponding groups in Table 1 or Table 2.
4.2.1.4 By mutual agreement between the Supplier and the Demander and specified in the contract, hot forged bars with intermediate dimensions not listed in Tables 1 and 2 or a dimension exceeding the maximum nominal dimension specified in Tables 1 and 2 may also be supplied. The tolerance of hot forged bars with a dimension exceeding the maximum nominal dimension specified in Tables 1 and 2 shall be determined by the Supplier and the Demander through negotiation.
4.2.2 Polished bar
4.2.2.1 The dimension and tolerance of the polished round bar with a nominal diameter of 40 mm~200 mm shall meet the requirements of Table 1. The dimension and tolerance of the polished round bar with a nominal diameter greater than 200 mm~600 mm shall meet the requirements of Table 3. The dimension tolerance groups shall be indicated in corresponding product standards or order contracts. Otherwise, those specified in Grope 2 shall prevail.
Foreword i
1 Scope
2 Classification
3 Cross-sectional shape
4 Sectional dimensions, weight and tolerances
Annex A (Normative) Dimensions and theoretical weight of forged bars
