GOST 3728-78
GOST 3728−78 Pipe. Test method for bend (with Amendments No. 1, 2)
GOST 3728−78
Group В69
INTERSTATE STANDARD
PIPE
Test method for bend
Tubes. Method of bend-over test
ISS 23.040.10
AXTU 1309
Date of introduction 1979−07−01
The decision of the State standards Committee of the USSR Council of Ministers No. 474
Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)
REPLACE GOST 3728−66
EDITION (September, 2010) with Changes No. 1, 2 approved in April 1980 and April 1985 (ICS 5−80, 7−85)
This standard covers metal pipe of circular cross section and sets the test method for bend to specified size and shape at a temperature of (20)°C.
The standard fully complies ST SEV 480−77 in terms of test bends.
(Changed edition, Rev. N 1).
1. SAMPLING METHOD
1.1. Testing bend pipe with outer diameter to 60 mm inclusive of selected samples in a segment of pipe of total cross section (Fig.1), tubes with external diameter over 60 mm, the samples in the form of transverse or longitudinal stripes.
(Changed edition, Rev. N 1).
Damn.1. Bend pipe sections
Bend pipe sections
1 — sample-nozzle; 2 — cylindrical mandrel; — the bending radius of the pipe on the middle line
Damn.1
1.2. The sample in the form of a tube segment cut from the end of a pipe length sufficient for it to bend in a predetermined angle and radius.
1.3. When the thickness of the tube wall is 5 mm wide longitudinal strips and transverse specimens shall be 10 mm When the wall thickness of pipe
5 mm sample width must be 2
.
At mass control testing pipes with wall thickness more than 5 mm to facilitate fabrication of samples to groups of samples of different thickness are allowed to set the same width equal to twice the maximum thickness of this group. By thickness is recommended with an interval of 5 mm.
(Changed edition, Rev. N 1).
1.4. Samples in the form of longitudinal strips and transverse samples from welded pipes cut outside the heat affected zone of the weld. Longitudinal strips should be cut out from a portion of the base metal angle of at least 90° from the position of the weld.
2. TESTING
2.1. The test is carried out by a smooth continuous bend of the sample around a grooved roller or mandrel of a given radius to a certain angle. The profile of the groove or of the mandrel must match the outside diameter of the test sample. If a normative-technical documentation for pipe requirements to limit the magnitude of the ovalization of the cross section of the pipe during the test is allowed to test with the use of an internal mandrel or filler.
2.2. The bend angle of the sample taken as equal to 90°, if in the normative-technical documentation for pipe not installed another angle.
2.3. The bending radius of sample in a segment of pipe pointing in the normative-technical documentation on the pipe. In the absence of such instructions, the bending radius of pipes from steels with elongation not less than 21% determined according to the table.1.
Table 1
Ratio of pipe wall thickness |
Outer diameter of pipe |
Bending radius |
| 0.1 and more | Up to 50 | 2 |
| SV. 50 | 3 | |
| Less than 0.1 |
Up to 60 incl. | 3 |
, mm(Changed edition, Rev. N 2).
2.4. When testing welded pipes the position of the weld must be specified in normative and technical documentation for the product. If this instruction corresponds to, the weld should be in compression and positioned at an angle of 45° to the plane of bending.
2.5. Testing of the weld metal and metal of the heat affected zone of the bend is carried out according to GOST 6996−66.
2.6. Test longitudinal bend specimens is carried out according to GOST 14019−2003.
Test transverse bend specimens (Fig.2) (strip in the form of the ring) is carried out according to GOST 14019−2003.
Damn.2. Transverse bend specimens
Transverse bend specimens
1 — mandrel; 2 — cross pattern; 3 — bearing; — distance between the supports
Damn.2
2.7. The mandrel radii for bend longitudinal strips and transverse specimens depending on the wall thickness of the pipe shall be as specified in table.2. While stretching efforts should be subject to the sample side, which is the outer surface of the pipe.
Table 2
| Wall thickness of pipe, mm |
The radius of mandrel, mm |
| 1,0−1,2 |
2,5 |
| 1,4−1,5 |
3,0 |
| 1,6 |
3,5 |
| 1,8−2,0 |
4,0 |
| 2,2 |
4,5 |
| 2,5 |
5,0 |
| 2,8 |
5,5 |
| 3,0 |
6,0 |
| 3,2 |
6,5 |
| 3,5 |
7,0 |
| 4,0 |
7,5 |
| 4,5 |
8,5 |
| 5,0 |
9,0 |
| 5,5 |
9,5 |
| 6,0 |
10,5 |
| 6,5 |
11,0 |
| 7,0−7,5 |
12,0 |
| Over 7.5 |
2 |
The transverse bend samples produced thus, to increase the initial curvature of the sample.
(Changed edition, Rev. N 1).
2.8. A sample is considered satisfactory if, after bending it will not be visually detected violation of the integrity of metal with metallic luster.
The inadmissibility of the corrugations should be specified in the normative-technical documentation for pipe.
(Changed edition, Rev. N 2).
3. TEST REPORT
In the test report indicate:
— material and size of pipe;
— the results obtained.
(Added, Rev. N 1).
