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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);
——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
ICS 77.040.10 H 23 中华人民共和国国家标准 GB/T 244—2020 代替GB/T 244—2008 金属材料 管 弯曲试验方法 Metallic materials—Tube—Bend test method [ISO 8491：1998，Metallic materials—Tube(in full section)— Bend test，MOD] 2020-06-02发布 2020-12-01实施 国家市场监督管理总局 国家标准化管理委员会 发布 前言 本标准按照GB/T 1.1—2009给出的规则起草。 本标准代替GB/T 244—2008《金属管 弯曲试验方法》，与GB/T 244—2008相比，主要技术变化如下： ——按国家标准编写要求修改了范围的表述(见第1章，2008年版的第1章)； ——将管壁厚度符号由“a”修改为“t”，并修改了表1中管壁厚度符号的注(见表1、图1，2008年版的表1、图1)； ——将全文的“弯心”修改为“弯模”； ——增加了特殊要求的试样可参照附录A进行弯曲试验(见4.3)； ——将“对要求在控制条件下进行的试验”修改为“对温度要求严格的试验”(见6.1，2008年版的6.1)； ——将“焊接管”修改为“直缝焊管”[见6.3及7e)，2008年版的6.3及7e)]； ——增加了资料性附录“专用弯管试验机及试验方法”的内容(见附录A)。 本标准使用重新起草法修改采用ISO 8491：1998《金属材料 管(全截面) 弯曲试验》。 本标准与ISO 8491：1998相比存在技术性差异，这些差异涉及的条款已通过在其外侧页边空白位置的垂直单线(|)进行了标示，具体的技术性差异及其原因如下： ——管壁厚度符号由“a”更改为“t”，以便与我国标准协调统一(见表1，ISO 8491：1998的表1)； ——增加了特殊要求的试样可参照附录A进行弯曲试验，以符合我国国情(见4.3)； ——将“焊接管”修改为“直缝焊管”，避免产生歧义[见6.3及7e)，ISO 8491：1998的6.3及7e)]。 本标准做了下列编辑性修改： ——修改了标准的名称； ——将第l章注中引用的“ISO 7438”用修改采用国际标准的“GB/T 232”代替(见第1章，ISO 8491：1998的第1章)； ——增加了表1和图1的表标题和图标题(见表1、图1)； ——修改了表1中管壁厚度符号的注(见表1，ISO 8491：1998的表1)； ——增加了资料性附录“专用弯管试验机及试验方法”的内容(见附录A)。 本标准由中国钢铁工业协会提出。 本标准由全国钢标准化技术委员会(SAC/TC 183)归口。 本标准所代替标准的历次版本发布情况为： ——GB 244—1963、GB 244—1982、GB/T 244—1997、GB/T 244—2008。 金属材料 管 弯曲试验方法 1 范围 本标准规定了金属管弯曲试验方法的试验原理、试验设备、试样、试验程序和试验报告。 本标准适用于测定外径不大于65 mm的圆形横截面金属管的全截面弯曲塑性变形能力。本标准适用金属管的外径范围可在相关的产品标准中做更详细的规定。 注：金属管横向条状试样的弯曲试验根据GB/T 232[1]来进行，以增加试样的原始弯曲率。 2符号、名称和单位 本标准使用的符号、名称和单位见表1。 表1 符号、名称和单位 符号 名称 单位 ta 管壁厚度 mm D 金属管原始外径 mm L 试样原始长度 mm r 弯模半径 mm α 弯曲角度 (°) a 在金属管标准中也用其他符号表示此参数。
