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Ref. No. : ISO/R 204 -1961 (E)
I
l I
IS0
I N T ERN AT I O N A L O R G A N I Z AT I O N FOR S TA N DARD I Z AT I ON
IS0 RECOMMENDATION
R 204
NON-INTERRUPTED CREEP TESTING OF STEEL
AT ELEVATED TEMPERATURES
1st EDITION
June 1961
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards belongs
to IS0 Member Bodies. Reproduction of these documents, in any
country, may be authorized therefore only by the national standards
organization of that country, being a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 204, Non Interrupted Creep Testing of Steel at Elevated
Temperatures, was drawn up by Technical Committee ISO/TC 17, Steel, the Secretariat of which
is held by the British Standards Institution (B.S.I.).
Work on this matter, which was begun by the Technical Committee in 1955, was com-
pleted in 1958, with the adoption of a proposal as a Draft IS0 Recommendation.
On 4 November 1959, the Draft IS0 Recommendation (No. 293) was distributed to all
the IS0 Member Bodies and was approved, subject to some editorial amendments, by the following
Member Bodies :
Australia Finland Netherlands
Austria France Norway
Belgium Germany Portugal
Romania
Brazil Greece
Bulgaria Hungary Spain
Burma India Sweden
Chile Israel Turkey
Czechoslovakia Italy United Kingdom
Japan
Denmark U.S.S.R.
One Member Body opposed the approval of the Draft: Poland.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in June 1961, to accept it as an IS0 RECOMMENDATION.
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IÇO/R 204 - 1961 (E)
IS0 Recommendation R 204 June 1961
NON-INTERRUPTED CREEP TESTING OF STEEL
AT ELEVATED TEMPERATURES
1. SCOPE
This IS0 Recommendation applies to those tests in which the strain is measured under tensile
creep stress and lies between 0.1 and 1.0 per cent, and in which the period of testing does not
exceed 10 O00 hours.”
It applies to tests in single machines and to each test in multiple testing machines.
2. PRINCIPLE OF TEST
The test consists of heating a test piece to a uniform temperature and subjecting it to constant
tensile load at that constant temperature without interruption, and determining the strain as a
function of time under load.
3. DEFINITIONS
3.1 Gauge length. At any moment during the test, the prescribed part of the cylindrical or pris-
matic portion of the test piece on which elongation is measured. In particular,
Original gauge length (Lo). Gauge length measured at ambient temperature, before
applying the load.
At any moment during the test, load divided by the
3.2 Stress (actually “nominal stress”).
original cross-sectional area of the test piece (at ambient temperature).
3.3 Percentage permanent elongation. Variation of the gauge length of a test piece subjected to
a prescribed stress (see clause 3.2) and, after removal of same, expressed as a percentage of
the original gauge length.
* This limit of 10 000 hours is fixed as a function of the conditions of test, and in particular of the temperature limits specified in section 7.
For tests of more than 10 O00 hours, the tolerances should he agreed between the parties.
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IÇO/R 204 - 1961 (E)
4. SYMBOLS AND DESIGNATIONS
Symbol Designation
Number
d Diameter of a circular section test piece
a Thickness of a flat bar
Width of a fiat bar
b
Original gauge length measured at ambient temperature, before
Lo
applying the load
Parallel length
Total length
Gripped ends
Original cross-sectional area of the gauge length
The form of end
of test piece os shown is
only intended os O guide.
5. TEST PIECES
5.1 The cross-section of the test piece may be circular, square, rectangular, or, in special cases,
of other form.
5.2 There should be transition curves between the gripped ends and the parallel length; the
gripped ends may be of any shape to suit the holders of the testing machine.
5.3 The tolerances on the preparation of the test pieces should be in accordance with those
given in the table, page 5.
5.4 As a rule, the diameter of the parallel length of machined cylindrical test pieces should be
not less than 4.0 mm (0.16 in).
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I
ISO/R 204 - 1961 (E)
TABLE
Tolerances on dimensions of test pieces
Tolerance on form
Machining tolerance.
Nominal dimensions on nominal dimensions
Designation
ISA
(ISA j 12)
Values
Symbols
Diameter of machined over 3 mm
f 0.06 mm 0.03 mm
circular-section test to 6mm
piece
(metric units)
over 6 mm
f 0.075 mm 0.04 mm
to 10mm
over 10 mm
=t 0.09 mm 0.04 mm
to 18 mm
over 18 mm
+ 0.105 mm
0.05 mm
to 30 mm
IT 9
over 0.1 19 in
Diameter of machined
f 0.002 5 in 0.001 in**
to 0.237 in
circular-section test
piece
(inch units) over 0.231 in
& 0.003 in 0.001 in **
to 0.394 in
over 0.394 in
+ 0.003 5 in 0.002 in **
to 0.709 in
over 0.709 in
i 0.004 in 0.002 in **
to 1.182 in
.-
Dimensions of cross-
section of rectangular-
Same tolerances as for diameter of
section test piece,
circular-section test pieces
machined on the four
faces
Dimensions of cross- over 6 mm
0.22 mm
section of rectangular- 10mm
to
section test piece,
unmachined on two
over 10 mm
0.27 mm
opposite faces
to 18mm
(metric units)
over 18 mm
0.33 mm
to 30 mm
over 30 mm
0.39 mm
to 50mm
____
IT 13
~~~~
Dimensions of cross-
over 0.237 in
0.009 in
section of rectangular-
to 0.394 in
section test piece,
unmachined on two
0.394 in
over
0.010 in
opposite faces
to 0.709 in
(inch units)
over 0.709 in
0.012 in
to 1.182 in
over 1. I82 in
0.016 in
to 1.969 in
* The machining tolerance applies when it is desired to use the nominal cross-section without measurement or calculation.
** Rounded off to 0.001 in.
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ISO/R 204 - 1961 (E)
6. DETERMINATION OF ELONGATION
6.1 The measurement represents the strain on the axis
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