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Ref. No.: IS0 / R 528 - 1966 (E)
IS0
I N T E R N AT I O N A L O R G A N I ZAT I O N FOR STA N DARD I Z AT I O N
IS0 R ECOM MEN DATI O N
R 528
REFRACTORY PRODUCTS
DETERMINATION OF PYROMETRIC CONE EQUIVALENT
(REFRACTORINESS)
1st EDITION
November 1966
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 528, Refractory Products-Determination of Pyrometric
Cone Equivalent (Refractoriness) , was drawn up by Technical Committee JSO/TC 33,
Refractories, the Secretariat of which is held by the British Standards Institution (BSI).
Work on this question by the Technical Committee began in 1953 and led, in 1962,
to the adoption of a Draft IS0 Recommendation.
In March 1963, this Draft IS0 Recommendation (No. 567) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to a few modifications of an
editorial nature, by the following Member Bodies :
Australia Germany Rom ani a
Austria Hungary Spain
Chile Italy Sweden
Czechoslovakia Japan United Kingdom
Denmark Netherlands U.S.A.
France Portugal
Two Member Bodies opposed the approval of the Draft:
India
U.S.S.R.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in November 1966, to accept it as an IS0 RECOMMENDATION.
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IS0 / R 528 - 1966 (E)
R 528 November 1966
IS0 Recommendation
REFRACTORY PRODUCTS
DETERMINATION OF PYROMETRIC CONE EQUIVALENT
(REFRACTORINESS)
1. SCOPE
This IS0 Recommendation deals with the determination of the pyrometric cone equivalent
(refractoriness) of refractory materials. Its useful range of application depends on the availability
of suitable pyrometric cones.
2. PRINCIPLE
In this determination, test pieces of refractory materials or products are raised in temperature
alongside pyrometric cones, and their behaviour is compared under the conditions specified below.
NOTE. - Pyrometric cones are manufactured for estimating the effect of temperature on silica, aluminosilicate and
aluminous products having regard to their composition. Consequently, the refractoriness test described below is
only fully correct when these products are concerned.
3. APPARATUS
3.1 Vertical or horizontal furnace
The vertical or horizontal furnace to be used for this determination consists of a cylindrical
chamber of at least 80 mm useful diameter or a rectangular chamber having minimum dimen-
sions of 60 mm in height and 100 mm in width. This furnace should be capable of reaching a
test temperature in accordance with the rate specified in clause 5.2.1.
The atmosphere in the furnace should be such as to have no reducing action on the pyrometric
cones or the test pieces *.
In the test conditions, the difference in temperature between the coldest spot and the hottest
spot of the space occupied by the stand, the test pieces and the pyrometric cones should not
exceed 10 "C (approximately '/2 cone). The uniformity of temperature should be established
from time to time. (The uniformity can be measured by means of thermocouples, but it is
also possible to use pyrometric cones.)
In the case of a flame-heated furnace, the pyrometric cones and the test pieces should be
protected from any direct action of the flames and any turbulence from the hot gases.
3.2 Pyrometric cones
The pyrometric cones are blunt-tipped skew triangular pyramids with sharp edges, of the
shape shown in Figure 1. Their conventional temperatures of collapse at the rate of heating
specified in clause 5.2.1 and when mounted at the angle specified in clause 5.1.1 should be
indicated by the manufacturers.
,
Y
SEC TlON A-A
BASE
FIG. 1. - Pyromeîric cones
Certain furnaces (e.g. Tammann furnaces or certain types of furnaces fired with hydrocarbon gas and oxygen) are not
suitable for this test because of the high content of reducing gases or water vapouï in their atmospheres; the atmosphere
of the furnace should be such as not to attack the cones or the test pieces.
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IS0 / R 528 - 1966 (E)
3.3 Stand for the pyrometric cones and test pieces
The stand for the pyrometric cones and the test pieces consists, depending on the type of
furnace, of a rectangular plate or disk of refractory material having adequately plane and
parallel faces; the refractory stand and the refractory cement used should not react with
either the pyrometric cones or the test pieces at the test temperature.
In order to overcome any tendency to irregular temperature distribution in the furnace, it
may be convenient to arrange for relative motion to take place between the furnace walls
and the stand, e.g. by rotating the latter, during the determination.
4. TEST PIECES
4.1 The test pieces should have a geometrically similar shape to the pyrometric cones and an
equal or greater height, between the limits 29 and 35 mm. The ratio of the height to the edge
of base should be 3.55 0.15.
4.2 The test pieces from shaped or unshaped (see clauses 4.2.1 and 4.2.2) refractory products
should preferably be cut; alternatively, they should be moulded, if necessary. The test
pieces should be moulded when r
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