FABRICATION OF LARGE-SIZED COMPLEX-SHAPED COMPONENTS
FROM QUARTZ CERAMICS: RESEARCH AND PRACTICAL ASPECTS.
PART II. RELATIONSHIP BETWEEN TECHNOLOGICAL PARAMETERS
AND THE QUALITY OF PRODUCTS FROM QUARTZ CERAMICS
A. G. Romashin,
E. I. Suzdal’tsev,
and M. Yu. Rusin
Translated from Novye Ogneupory, No. 11, pp. 20 – 27, November, 2004.
Original article submitted June 22, 2004.
Based on many-years experience in developing products from quartz ceramics, a classification for technologi
cal defects has been proposed and factors responsible for their origination considered.
It has been reported in [1, 2] and [3; Part I] that most
technological operations in the production of fairings from
quartz ceramics are controlled operations which, in principle,
allows the output of engineering components with tailored
properties. Still, the manufacture of large-size complex-
shaped parts from quartz ceramics has never been a process
completely free of substandard (rejected) products. Relevant
data based on one-year statistics are shown in Fig. 1; here the
yield rate (the ratio of the total number of fabricated parts to
the number of quality parts) is shown for productive months
scheduled throughout one year. As can be seen, the yield of
suitable parts is far from satisfactory, except perhaps for the
June through October period. Therefore an analysis of the
factors, both objective and subjective, involved in the occur
rence of rejected parts and the corresponding remedial mea
sures to be taken remains an issue of serious concern.
Based on a survey of specimens rejected in different
technological operations, a classification for the rejects (de
fective products) was proposed: (i) cristobalitization of the
material during heat treatment; (ii) crack nucleation at differ
ent steps of the technological process; (iii) occurrence of
large pores because of air entrapment by the slip; (iv) acci
dental damage because of negligent handling, and (v) failure
to meet the prescribed standard specifications.
In a number of cases, these causative factors could be in
volved in combination, rather than singly; most commonly,
two main factors came into play — cristobalitization and
crack nucleation. In this context, it seems reasonable to con-
sider the involvement of individual technological parameters
in relation to a specific defect. Relevant data are given in Ta-
bles 1 – 9. As can be seen, some parameters (viscosity, stabi-
lization time, slip pH, molding time, sintering density) pro-
duced little effect on the product quality, whereas the role of
other parameters was significant: the rejection rate tended to
decrease with increase in slip density and grinding fineness
(Tables 1 and 3). We consider the involvement of these fac
tors in some detail.
Table 10 summarized the characteristics of products fab
ricated over a period of one year from a slip with the density
of 1.88 g/cm
and grinding fineness T of 4.2 – 6.0% (frac
Refractories and Industrial Ceramics Vol. 46, No. 1, 2005
1083-4877/05/4601-0063 © 2005 Springer Science+Business Media, Inc.
Tekhnologiya Research and Production Enterprise (Tekhnologiya
RPE), Obninsk, Kaluga Region, Russia.
01 02 03 04 05 06 07 08 09 10 11 12
Fig. 1. The yield rate for components fabricated from quartz ce
ramic on different productive months.