ENHANCING THE RELIABILITY OF THE SCREW – NUT FRICTION
COUPLE OF A FRICTION SCREW PRESS FOR REFRACTORIES
B. R. Kiselev
Translated from Novye Ogneupory, No. 12, pp. 33 – 35, December, 2005.
Original article submitted June 27, 2005.
Tribological techniques for enhancing the operational reliability of the screw – nut assembly of a 4KF-200
friction screw press for shaping refractory materials are considered. Economic and engineering effects due to
the design modifications proposed are discussed.
Semidry pressing is known to be the most conventional
technique for shaping refractory components that allows the
use of various molding mixes irrespective of their chemical
and phase composition . In this work, we consider the
semidry pressing technique using a screw press whose prin-
ciple of operation is based on the transformation of drive
energy into useful work by means of a screw-driven operat-
ing mechanism .
The screw in the 4KF-200-type friction screw press has
two kinds of thread. The upper thread is in contact with a
bronze nut mounted in the stationary cross-arm. In the lower
section of the screw, an iron nut is mounted in the travelling
cross-arm. The two couples are antifrictional. The 4KF-200
press, as shown by numerical analysis and testing, can pro
duce a maximum pressing force F
as high as 593.6 kN when
shaping a periclase-carbon raw material at a working screw
stroke H = 130 mm.
However, problems arise when refractory materials of
periclase-corundum or corundum composition with the co
rundum powder concentration reaching 90% and apparent
raw density of 3.38 g/cm
are to be shaped. One problem is
the frequent failure of the screw and the rapid wear of the up
per nut operating under heavy-load conditions. To remedy
the situation, the performance of 4KF-200 press was put un
der close scrutiny with a view to selecting appropriate mate
rials and types of thread that might enhance the operational
reliability of the screw – nut assembly. Selection of a mate
rial proved to be an arduous task considering that the
screw – nut couple operates under heavy dynamic conditions
and it is subject to cyclic impact loading which generates a
complex stress in the thread. Under these conditions, the
sliding friction increases significantly, and the friction coeffi-
cient develops sensitivity to a range of factors such as the
material of friction couples, class of finish of the friction sur-
face, sliding speed, pressure, the type of lubricant, etc.
As is known, the normal use of antifriction iron is regu-
lated by the State Standard GOST 1585–85. For the Tr 160´72
( p24)-type screw, the linear speed is v = 0.883 m/sec and the
thread pressure is p = 6 MPa, in conformance with GOST
24739–81; the product of these two values is
pv = 5.3 MPa × m/sec. An iron with such value of pv is not
readily available; for examples, for AChS-2-grade iron,
[pv ] = 2.5 MPa × m/sec and for AChS-3-grade iron, [pv ]=
5 MPa × m/sec. Tests that were conducted on nuts made of
these materials failed to give satisfactory results.
Bronze is a good antifriction material, and a bronze nut
with a steel screw forms a friction couple with a low sliding
friction coefficient. Its value varies from 0.07 to 0.14 de
pending on the bronze grade, lubricant used, and loading
conditions. Bronzes are capable of sustaining sufficiently
high thread pressure. Based on engineering and economic
figures, the use of bronzes for pressing refractory materials
seems quite justified despite their rather high cost.
Use of the steel nut requires solution of a number of en
gineering and tribological problems considering that the as
sembly steel nut – steel screw is no longer an antifriction
Typical threads and their geometric parameters are given
in Table 1.
The square thread is not a standard type, technically it is
rather difficult to cut, and its final finish (polishing) is still
more difficult (if possible at all) to achieve. However, the
Refractories and Industrial Ceramics Vol. 47, No. 1, 2006
1083-4877/06/4701-0021 © 2006 Springer Science+Business Media, Inc.
Ivanovo State University of Chemical Technology, Ivanovo,