GOST 12501-67

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  ГОСТ 12501-67

GOST 12501−67 Pipe. Test methods torque (with Change No. 1)

GOST 12501−67

Group В62*
__________________________
* In pointer «National
standards» 2007 В69. -
Note the manufacturer’s database.

INTERSTATE STANDARD

PIPE

Method of test torque

Tubes. Twisting moment test method

ISS 23.040.10
AXTU 1909

Date of introduction 1967−04−01

The decision of the State Committee of standards, measures and measuring instruments of the USSR from 04.01.67 date of introduction is established 01.04.67

Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)

EDITION (September 2010) with amendment No. 1, approved in may 1986 (IUS 8−86).


This standard applies to steel seamless-rolled, dragged and welded pipe and establishes the method of static tests torque to determine the temperatures of 15−30 °With the following characteristics:

a) the moment of the elasticity limit (conditional);

b) limit of proportionality (conditional);

C) the moment the yield point (physical);

g) the moment of the yield strength (conditional);

d) the maximum torque.

Application of the method provided for in the standards and specifications that establish technical requirements for steel pipe.

1. DEFINITIONS AND NOTATION

1.1. When testing steel pipes torque, provides the following denitions and notation:

a) the working length of the sample , mm — the part of the sample between stations for capturing;

b) gauge length of the specimen , mm — section of the sample used for determining deformation values;

in) outside diameter of pipe , mm;

d) the wall thickness of pipe , mm;

d) torque , N·m (kgf·m) acting on the sample at the moment.

e) the angle of twist , in degrees, the relative angle between the cross sections at the ends of the calculated length;

g) residual shear  — plastic deformation of the sample after removal of an applied torsional moment.

1.2. The characteristic properties of the steel pipe, which is determined when the test torque, have the following designations and definitions:

a) the time limit of elasticity (conditional) N·m (kgf·m) the torque value at which a sample receives a residual shift of 0.05%.

Note. If the standards or specifications for steel pipe special instructions are allowed to determine the value of the torque limit of elasticity (conditional) with smaller tolerances on the magnitude of the residual shift (to 0.02%). The amount used tolerance needs to be specified in the designation, e.g. ; , etc.

b) the time limit of proportionality (conditional) , N·m kgf·m torque value at which the deviation from a linear relationship between torque and angle of twist on the surface of the sample reaches a value at which the tangent of the angle which the tangent to the curve and deformation axis points exceeds its original value by 50%.

Note. If the standards or specifications for steel pipe specific instructions, are allowed to determine the value of the torque limit of proportionality , N·m (kgf·m), with some tolerance for increase in specified tangent angle tangent.

The tolerance percentage must be specified in the designation, for example: , , etc.

C) the moment of yield stress (physical) , N·m (kgf·m) — lowest value of the gray point at which the sample is deformed without noticeable changes of the load;

d) the moment of the yield strength (conditional) , N·m (kgf·m) the torque value at which a sample receives a residual shift is equal to 0.3%.

Note. If the standards or specifications for steel pipe specific instructions, are allowed to determine the magnitude of the moment of the conditional yield strength at the different tolerances on the magnitude of the residual shift. The amount used tolerance must be specified in the designation, for example: ; .

d) the maximum torque , N·m (kgf·m) — torque, prior to the buckling of the pipe (wrinkling).

2. THE SHAPE AND DIMENSIONS OF SAMPLES

2.1. For testing pipes torque used pieces of pipe of total cross section.

2.2. The production of samples by the segments of pipe lengths necessary produce cutting equipment.

It is necessary to take precautions against possible changes in the metal properties of the samples due to heating or cold working. Surface samples (except the ends) mechanical treatment subjected to.

Sharp burrs on the ends of the samples remaining after the segments have to be removed by zapilovku or turning.

2.3. The tests do not allow for samples having on the surface of the working part dents, nicks and other physical damage.

2.4. The outer diameter of the samples is measured with an accuracy of 0.1 mm.

2.5. The estimated length of the samples corresponds to the basis used strain gauge and incubated with the error not more than 1.0 mm.

Note. The application of the estimated lengths less than 500 mm is not recommended.

2.6. Total sample sizes set by the devil.1.

Damn.1. The overall dimensions of the samples

Damn.1

2.7. For the implementation of deformation in twisting the ends of the samples (tubes) are tightly inserted a metal tube, preventing the sample from crumpling when mounted in the grips of the machine.

2.8. The marked samples outside the estimated part.

3. TESTING EQUIPMENT

3.1. As the testing machine permitted to use machines for all torsion systems, providing:

— the accuracy of the readings of torque value ±1%;

— smooth static load (without shocks);

a reliable centering of the specimen and absence of bending loads;

— the possibility of suspending the load with a precision of one smallest division of the scale siloizmeritelya;

free longitudinal movement of one of the grippers;

— smooth unloading.

3.2. In determining the quantities of limit moments by means of strain gauges or tensiometers the price of division of the latter must not exceed 10'.

4. THE TESTS AND CALCULATION OF RESULTS

4.1. Torque during the test count up to one smallest division of the scale siloizmeritelya.

4.2. In determining the quantities of limit points of the test pipe load shall be not less than 0.1 applicable scale siloizmeritelya, but not less than 0,04 of the maximum load of the testing machine.

4.3. The time limit of elasticity (conditional) is determined using strain gauges or tensiometers in the following way.

Calculate the magnitude of the residual shift () in degrees by the formula

,

where  — base strain gauge used to measure the residual shear strain (gauge length of the specimen) mm;

 — outer diameter of pipe, mm;

 — the tolerance on the magnitude of the residual shift, %.

The obtained value is rounded up to 5'.

On the sample after fixing it in the grips of the testing machine and load torque not exceeding 10% of the expected value of the moment of the elasticity limit, set the strain gauge.

Next, the sample load time, constituting 70% of the expected moment of elasticity, and relieve to the starting point. Produce the following loading steps corresponding to not more than 10% of the expected ultimate moment. After each stage of loading and unloading produce to the starting point with the definition of residual shift.

The test is stopped, when the residual shear will reach or slightly exceed the computed value .

According to test results to determine the value of moment corresponding to a fixed residual offset.

In those cases when it is necessary to clarify the numerical value of the designated features allowed the use of linear interpolation.

Example determine the moment of the elasticity limit .

Sample — pipe 51х2,5 mm initial gauge length and the base strain gauge 750 mm, the expected time limit of elasticity 2450−2548 N·m (250−260 kgf·m).

The amount of residual offset equivalent

.

The initial time is 196 N·m (20 kgf·m). The price of division of the strain gauge 10'.

The first stage of loading taken as equal to 1760 N·m (180 kgf·m), further loading is carried out in steps of 196 N·m (20 kgf·m) to until the residual shear reaches or slightly exceeds the set tolerance 0°50'. The results of the tests recorded in table.1.

Table 1

According to test results find the value of moment corresponding to a fixed residual offset. The time limit of elasticity (conditional) 2548 N·m (260 kgf·m). The precise moment is found by linear interpolation:

2548−2352=196 N·m (20 kgf·m); 60' — 25' = 35'.

Extra point () is determined from the proportions of 196 N·m — 35'

,

where is the difference between the calculated residual shear 0°50' and received (1°) after removal of an applied moment 2548 N·m (260 kgf·m);

* N·m (to 5.7 kgf·m).

________________
* Formula conforms to the original. — Note the manufacturer’s database.

Sharpen the point of elastic limit equal 2548−56=2492 N·m (254,3 kgf·m).

(Changed edition, Rev. N 1).

4.4. You can define the time limit of elasticity (conditional) for the diagram test (Fig.2), built according to the readings siloizmeritelya testing machine (torque) and strain gauge (deformation). The scale of the chart must comply with 1 (mm) x-axis not more than 0.1% residual shift of 1 mm and the vertical axis is not more than 1.0% of the value determined by the torque.

Damn.2. Chart test

Damn.2

To determine when to calculate the magnitude of the residual shear according to the formula given in claim 4.3.

From a point distant from the origin at a distance equal to the magnitude of the specified tolerance on the residual shear, draw , parallel to the line . Point (the intersection of the curve with twisting) determines the height of the ordinates, i.e. the amount of time that meets the time limit of elasticity for a given tolerance on the magnitude of the residual shift.

4.5. The time limit of proportionality (conditional) is determined using strain gauges or tensiometers in the following way.

The sample after its fastening in the grips of the testing machine and load torque not exceeding 10% of the expected time limit of proportionality, set the strain gauge.

The holding time under load for the readings at each stage of loading shall be not more than 5−7 C.

The sample is loaded with large steps to the magnitude of the moment of 70% of the expected time limit of proportionality . Further loading produced by small steps (5% of the expected time limit of proportionality). When the angular deformation from loading at a low stage will exceed by 2−3 times the average value of the increment of deformation (at the same level of load) in the initial linear elastic portion, the test is stopped. On the elastic portion, determine the average angle of twist at a low level of loading and the magnitude increased by 50% (in accordance with the given tolerance).

Torque corresponding to the point of this single strain, which is in the region of the low stage load is the desired value.

In those cases when it is necessary to clarify the numerical value of the designated features allowed the use of linear interpolation.

Example determine when the limit of proportionality (conditional)

Tolerance to the increase of the tangent of the angle formed tangent to the curve deformation with the axis of the loads, 50% of its value in the linear range.

Sample — pipe 51х2,5 mm initial gauge length and the base strain gauge 750 mm, the expected point of limit of proportionality 2450 N·m (250 kgf·m).

The initial moment 10% of the expected 2450 N·m (250 kgf·m) will amount to 245 N·m (25 kgf·m) (rounded accept 196 N·m (20 kgf·m). The moment that meets 70% of the expected time limit of proportionality, equal to 1715 N·m (175 kgf·m) (rounded accept 1760 N·m (180 kgf·m).

To obtain at least four samples in the interval loads of the large level of loading is determined by the formula

392 N·m (40 kgf·m).

Further loading is carried out by small steps at 98 N·m (10 kgf·m) (which corresponds to the increment of the value of time not more than 5% from the expected ) to noticeable deviations from the law of proportionality.

The average value of the increment of the shear angle on the small stage of the applied torque 98 N·m (10 kgf·m) is

.

Found the increment of the shear angle on the small stage of the applied moment on the linear plot, in accordance with established tolerance increase 50%. The desired magnitude to the degree of applied torque will be

.

The desired time, corresponding to the limit of proportionality , find on the basis of the obtained results. In this case 2450 N·m (250 kgf·m).

The found point can be refined using linear interpolation

2548−2450=98 N·m (10 kgf·m); 20−10=10.

Additional moment , N·m (kgf·m), determined from the proportions of 98 N·m — 10'

,

where 5' is the difference between the specified shift angle 15' and the resulting difference of the readings on the strain gauge 10' at 2450 N·m (250 kgf·m);

49 N·m (5 kgf·m).

Clarified the time limit of proportionality (conditional) is

2450+49=2499 N·m (255 kgf·m)

The results of the tests recorded in table.2.

Table 2

___________________
* Scale strain gauge 10'.


(Changed edition, Rev. N 1).

4.6. The moment the yield point (physical) is determined by the diagram obtained on the test machine if the scale of the graph ensures compliance of 1 mm to the x-axis not more than 0.1% of the relative shift of 1 mm and the vertical axis is not more than 1% of the value determined by the torque.

At a mass testing time can be determined by an explicit stop arrows siloizmeritelya of the testing machine due to the deformation of the sample without an appreciable increase in the magnitude of the moment.

4.7. The moment the yield strength (conditional) define:

— with the help of strain gauges according to the method of determining the time limit of elasticity;

— accelerated method (for mass testing). This method allows you to set a matching torque characteristics of conditional yield point of the standards prescribed standards or specifications for the pipe. The exact value of the conditional moment yield point by this method is not defined.

The essence of the method consists in the determination of residual shear at the point corresponding to the standard requirements or technical specifications, and comparing it with the coefficient of the corresponding checklists.

Checklists can be obtained from the result of the calculation of the residual shift, depending on the specified tolerance of the pipe dimensions and strain gauge.

Example of the control table to determine using strain gauges with the database 500, 750 and 1000 mm are shown in Annex 1.

If the readings of the strain gauge when a predetermined amount of time is less than or equal to the values of the control tables for the appropriate pipe size, the pipe tested to meet the requirements.

4.8. To determine the magnitude of the limiting torque, the test specimen is subjected to torsion under the action of gradually increasing the time before the buckling (collapse) of the pipe.

The greatest amount of time preceding the loss of stability of the tube, taking the limit torque .

4.9. The values of torque recorded in the test report, a recommended form is given in Appendix 2.

4.10. The test will be considered invalid:

— at failure of the specimen in the grips of the testing machine or outside the calculated length;

— with the destruction of the sample for defects of metallurgical production (rassai, blisters, slivers, etc.);

— the disclosure of the weld;

— when errors are detected in testing or record the results.

In these cases, the test may be repeated on new samples of the same batch or heat.

APPENDIX 1. Checklist for pipe diameters from 50 mm to 114 mm

ANNEX 1

__________________
* Scale strain gauge 10'.

APPENDIX 2. Proforma of test report of steel pipes torque

ANNEX 2

PROTOCOL N