This standard is identical to ISO 8491:1998 "Metallic Materials — Tube (in Full Section) — Bend Test" (English edition).
This standard is identical to the translation of ISO 8491:1998 "Metallic Materials — Tube (in Full Section) — Bend Test" (English edition).
The following editorial changes are made in this standard:
a) "This International Standard" was changed to "this standard";
b) Replace decimal comma "," with decimal ".";
c) The foreword of the international standard was deleted and the one of this standard was added;
d) In the note of Chapter 1 of the original standard, "in accordance with ISO 7438" was changed to "in accordance with GB/T 232";
e) In the Chapter 7, a) of the original standard, "reference to this International Standard, i.e. ISO 8491" was changed to "series number of this standard".
This standard supersedes GB/T 244-1997 "Determination of Depth of Decarburization of Steel", and the following modifications had been made on the base of original standard:
1) Application scope was extended;
2) The requirements of test specimen were redefined;
3) Specifies more detail requirements on test procedures and test conditions;
4) Bibliography was added.
This standard was proposed by China Iron and Steel Association.
This standard is under the jurisdiction of the National Technical Committee 183 on Iron and Steel of Standardization Administration of China.
Drafting organizations of this standard: Changshu Entry-Exit Inspection and Quarantine Bureau and China Metallurgical Information and Standardization Institute.
Chief drafting staffs of this standard: Wang Weizhong, Gu Wei, Yuan Jianliang, Dong Li and Yi Haiqing.
The previous editions of the standards superseded by this standard are as follows:
GB 244-1963, GB 244-1982, GB/T 244-1997.
Determination of Depth of Decarburization of Steels
1 Scope
This standard specifies a method for determining the ability of full-section metallic tubes of circular cross-section to undergo plastic deformation in bending. It is intended for tubes with an outside diameter no greater than 65 mm, although the range of the outside diameter for which this International Standard is applicable may be more exactly specified in the relevant product standard.
Note: Bend tests of the test pieces taken from tubes in the form of transverse strips should be made in accordance with GB/T 232 so as to increase the original curvature of the test piece.
2 Symbols, Designations and Units
Symbols, designations and units for the bend test of tubes in full section are given in Table 1 and are shown in Figure 1.
Table 1
Symbol Designation Unit
a a Wall thickness of the tube Mm
D Mm
L Mm
r Mm
a (°)
a The symbol T is also used in steel tube standards.
3 Principle
Bending a straight tube in full section around a grooved former of a specified radius r until the angle of bend a (see Figure 1) reaches the value specified in the relevant product standard.
Figure 1
4 Testing Equipment
4.1 Tube-bending machines, designed to prevent the section of the tube from becoming oval.
The tube bend former of the machine shall have a groove corresponding in profile to the outside diameter of the tube. The radius at the bottom of the groove shall be specified in the relevant product standard.
Note: The tolerance of radius r, the depth and ovality of the groove, all have an effect on the test result.
5 Test Piece
The test piece shall be a portion of a straight tube of any length which will allow the test to be carried out on the tube-bending machine.
