Note: Descriptions are shown in the official language in which they were submitted.
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OUTOKUMPU Oy, Ou-tokumpu
790678
Wearing surface for a crusher and a method for manufacturing
th same
The present invention relates to a wear- and shock-resistant
~earing component intended to be attached to the backing
surface in a crusher and having a machined fitting surface,
~nd to a method for manufacturing -the same, and this invention
relates in particular to a method for manufacturing jAW
plates and crusher coatings.
T~e replaceable wearing components in jaw crushers include the
coating plates of the fixed jaw and the ;swinging jaw, as
well as the plates protec-ting the sides of the chamber. The
wearing components in gyratory crushers ,include the respective
coatings of the moving crushing cone and the fixed crushing
bowl.
The material which has been used as coating material in crusners
is a hard manganese steel which contains carbon approx. 1.2 %
by weight and manganese approx. 14 % by weight and has a
Brine~ Hardness Number of approx.200 after casting and heat
treatment. Hard manganese steel is also characterized in that
it is tough and shock-resistant and that its backing surfaces
can be machined after casting. However, such manganese cast-
steel is not resistant to abrasive wear.
Furthermore, coating components made from so-called martensi~ic
~hite cast-iron have been used in smal] jaw crushers (Delonge,
~.A., Abrasion-resistant alloy reduces milling costs,
Engineering Mining Journal 147 (1946):10, 60-62). Such
martensitic white cast-iron usually contains carbon 2.9-3.9 ~,
silL~on 0.5-1.0 % by weight, man~anese 0.4-1.2 % by weight,
chromium 1.5-3.0 %, nickel 2.5-4.75 ~ by weight, and possibly
also molybdenum, copper and vanadium. Such martensitic white
cast-iron is highly resistant to abrasion and is also resistant
~o shocks, provided -that it is not subjected -to bending stress.
The proper-ties of martensi-tic white cast-iron, i.e. so-called
Ni--hard, have been described in the publication of International
~ickel Co.: Engineering Properties and Applications of Ni-hard,
~ulletin, New York 1954.
The use of white martensitic cast-iron ior wearing components
subjected to shocks and especially for t:he wearing components
vf crushers has been prevented by the fact that such cas-t-iron
cannot be machined to the precision required by the backing
su~faces. The machining problems result in that wearing
components made from martensitic white cast-iron do not fit
ti~htly against the backing surfaces at all points, and so, when
~h~y are sub~ected to shocks in crushers, they bend and break
easi~Ly. I~ the publication Vuoriteollisuus, issue 1 (1960) 1-39,
the ~roperties of martensitic white cast-iron are compared with
t~se of various steels. It is noted in this publication that
martensitic white cast-iron can be used advantageously as
coating material in mills. In mills the coating material is not,
however, subjected to bending stresses o~E the same magnitude as
in crushers. Nevertheless, it is also polnted out in this
publiLcation that problems have been encountered in the dry
millin~ machine of a vanadium factory owi.ng to -the brittleness of
martensitic white cast-iron but that the wear was minimal
compared with that of hard manganese stee!l. The great wear of
the latter was due to the fac-t that -the coating was smooth and
that the milling load slid along the coating.
It can be seen from the above that hard ~ n~se steel has
been used for the manufacture of the wearing componen-ts of
crushers because after casting its backing surfaces can be
machined but its poor resistance to ab:rasive wear constitutes
a disadvantage. It can also be seen from the above -that
martensi-tic white cas-t-iron would be a more advantageous
~a~erial than hard manganese steel for the wearing components
of crushers because it is highly resistant -to abrasive wear and
also to shocks, provided it :is not subjected to bending
s~resC3es. However, in order to preven~ a crusher wearing
c~mponent made from martensitic whi-te cast-iron from being
s~jected to bending stresses it must be possible to machine
this component to the precision required by the backing
surface. This has proved -to be very di:Eficult since a casting
~ade from martensi-tic white cast-iron .is very hard, its Brinell
~ardness ~umber is approx. 500-600.
~he object of the present invention is -therefore to elimina-te
the above problems and to provide a crusher wearing component
the fi-tting surface of which can be machined to -the precision
r~uired by the backing surfaces, the wearing surface of the
c~ponent heing as resistant to abrasive wear as is martensitic
~it~ cast-iron.
~'he ~ear- and shock-resistant wearing component according to
the invention, intended to be attached to the backing surface
of a crusher and having a machined fi-tting surface, is
c~ar~cterized in that the fitting surface is of sof-t steel
whic~ ~an be machined and the wearing surface is of martensitic
white cast iron.
The crusher woaring cornponen-t according to -the presen-t invention
is manufactured by attaching the soft steel constituting the
machinable fitting surface and -the martensitic white cast-iron
COnStitUtillg the wearing surface to each other by hot welding
and by machining the fittiny surface to the shape of the
backing surface. The hot welding of the machinable fitting
surface and the wearing surface to each other can be achieved
by casting the mar-tensitic whi-te cast-iron onto a possibly
4 ~ 7
pre-heated soft-s-teel plate, depressions or spigots having
possibly been formecd on one side of the soft steel plate beEore
the casting of the martensitic white cast-iron on the said
side.
Alternatively, the martensitic white cast-iron can be cast
first, whereafter soft steel is cast onto the still hot
~earing surface of martensltic white cast-irorl, and the soft
steel is finally machined to form the fitting surface.
Alternatively, perforations can be made in a soft steel pla-te,
and through these perforations a wearing surface made from
martensitic white cast-iron is attached to the soft steel
plate by welding.
It is evident that the expression "soft steel" in this conte~t
denotes in general any steel which can be machined to the
precision required by the backing surfaces in the crusher
and which, without deforming, is resistant to the stresses
it is subjected to in the crusher.
