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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 244-2008 Metallic materials-tube - Bend test, and the following main technical changes have been made with respect to GB/T 244-2008:
——The description of the “Scope” is modified in accordance with the preparation requirements of national standards (see Clause 1; Clause 1 of Edition 2008);
——The symbol of tube wall thickness is changed from "a" to "t", and the note of the symbol of tube wall thickness in Table 1 is modified (see Table 1 and Figure 1; Table 1 and Figure 1 of Edition 2008);
——The "bending center" in the full text are changed to "bending die";
——The specimen with special requirements may be subjected to bend test according to Annex A (see 4.3);
——"The test required to be carried out under controlled conditions" is modified to "the test with strict requirements on temperature" (see 6.1; 6.1 of Edition 2008);
——The "welded tube" is modified to "straight seam welded tube" [see 6.3 and 7e); 6.3 and 7e) of Edition 2008];
——The informative annex "Special elbow tester and test method” is added (see Annex A).
This standard has been redrafted and modified adoption of ISO 8491:1998, Metallic materials - Tube (in full section) - Bend test.
Technical differences between this standard and ISO 8491:1998 are marked with perpendicular single line (|) in the outside page margin of the provisions concerned. Technical differences and their reasons are as follows:
——The symbol of tube wall thickness is changed from "a" to "t", so as to coordinate with the national standards (see Table 1; Table 1 of ISO 8491:1998);
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——The content of “the specimen with special requirements may be subjected to bend test according to Annex A” is added, so as to conform to China's national conditions (see 4.3);
——The "welded tube" is modified to "straight seam welded tube” to avoid ambiguity [see 6.3 and 7e); 6.3 and 7e) of ISO 8491:1998];
The following editorial changes have been made in this standard:
——The standard name is modified;
——The "ISO 7438" cited in the Note of Clause 1 is replaced by "GB/T 232" which is modified in relation to the international standard (see Clause 1; Clause 1 of ISO 8491:1998);
——The titles of Table 1 and Figure 1 are added (see Table 1 and Figure 1);
——The note on the symbol of tube wall thickness in Table 1 are modified (see Table 1; Table 1 of ISO 8491:1998);
——The informative annex "Special elbow tester and test method” is added (see Annex A).
This standard was proposed by China Iron and Steel Industry 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 244-1963, GB 244-1982, GB/T 244-1997, and GB/T 244-2008.
Metallic materials - Tube - Bend test method
1 Scope
This standard specifies the test principle, test equipment, specimen, test procedures and test report for the bend test of the metallic tube.
This standard is applicable to the determination of the full-section bending plastic deformability of the circular cross-section metallic tube with an outer diameter of not greater than 65mm. The outer diameter range of the metallic tube applicable to this standard may be specified in more detail in relevant product standards.
Note: The bend test of the transverse strip metallic tube specimen is carried out according to GB/T 232[1] to increase the original bending rate of the specimen.
2 Symbols, names and units
See Table 1 for the symbols, names and units applied in this standard.
Table 1 Symbols, names and units
Symbol Name Unit
ta Tube wall thickness mm
D Original outer diameter of metallic tube mm
L Original length of specimen mm
r Bending die radius mm
α Bend angle (°)
a This parameter is also expressed by other symbols in the metallic tube standards.
3 Test principle
A straight metallic tube with full section is bent around a bending die with a specified radius and groove until the bending angle reaches the value specified by the relevant product standard (see Figure 1).
Figure 1 Schematic diagram for test principle
4 Test equipment
4.1 The test shall be conducted on the elbow tester, which shall be able to prevent elliptical deformation of the cross section of the tube during the test.
4.2 The bending die of the elbow tester shall be provided with a groove suitable for the outer diameter profile of the tube. Bending die radius is specified by relevant product standards.
4.3 After negotiation between the supplier and the demander, specimens with special requirements may refer to Annex A for bend test.
Note: Deviation of the bending die radius, depth of the groove and ellipticity all have influence on test results.
5 Specimen
The specimen shall be a part of the straight metallic tube and can be tested on the elbow tester.
6 Test procedures
6.1 In general, the test is carried out at a room temperature of 10℃~35℃. For tests with strict requirements on temperature, the test temperature shall be 23℃±5℃.
6.2 The specimen without filler is bent by the elbow tester. During the test, make sure that the bending deformation section of the specimen is in close contact with the bending die of the metallic tube until the specified bending angle is reached.
Foreword I
1 Scope
2 Symbols, names and units
3 Test principle
4 Test equipment
5 Specimen
6 Test procedures
7 Test report
Annex A (Informative) Special elbow tester and test method
Bibliography
