[0001] The subject of the invention is a mould insert with extended service life for forming
stampings by means of press moulding method, especially stampings from refractory
materials in the form of powders or granulates.
[0002] The moulds for fabrication of cuboidal stampings out of powdered refractory materials
known to date have usually a frame provided with a through opening with rectangular
profile in which a die is mounted composed of four side monolithic plate-shaped inserts
made of tool alloy steel of NC11 grade with hardness of 60HRC.
[0003] Replaceable inserts for these moulds, as a result of friction occurring between them
and the powdered refractory material under pressure exerted on them in the course
of press moulding, after fabrication of certain number of stampings are subject to
significant wear-out which results in rejection of the manufactured stampings and
ultimate scrapping of the inserts after several cycles of renovation. The wear is
also the cause of prolonged stoppages in the stampings production process relating
to the necessity to remove the mould from the press, uninstall the worn-out inserts,
and install analogous replacement inserts.
[0004] The objective of the present invention is to eliminate the above-quoted inconveniences
characterising the plate-shaped steel mould inserts constituting the cavity of the
mould used to fabricate the stampings.
[0005] According to the invention, the essential feature of the mould insert with extended
service life for forming stampings by means of the press moulding method, especially
out of refractory materials in the form of powders or granulates, constituting one
of linings of side walls of the mould die and made of alloy steel in the form of plate-shaped
cuboidal solid consists in that its outer working surface is joined inseparably with
a metallic coating with thickness of 0.2-0.4 mm and hardness of 2750-2785HV, whereas
the coating contains in its composition 86-90% by weight of tungsten carbide and 10-14%
by weight of cobalt. Favourably, the inseparable joint between the outer working surface
of the mould insert with the metallic coating is made by means of plasma-spraying
of powder with grain size (45 ± 15) µm.
[0006] The new design solution of the mould insert with increased service life for forming
stampings of refractory materials supplied in the form of powders or granulates according
to the present invention allowed to reduce significantly the operating costs related
to the use of said form, and thus to reduce also the overall cost of the products
fabricated in these moulds. The above-mentioned merits of the mould insert according
to the invention are evidenced, among other things, by the following facts:
- the monolithic, massive, one-piece mould insert made of alloy tool steel was replaced
with an analogous monolithic mould insert but with a metallic coating containing tungsten
carbides in a cobalt matrix deposited by means of plasma-spraying of powder with grain
size of (45 ± 15) µm on the insert working surface and joined permanently with said
surface which resulted in a multiple increase of service life of such mould insert
compared to previously used inserts without such coating, and moreover
- the increase of the service life of mould inserts, and at the same the service life
of the mould for production of stampings of powdered refractory materials allowed
to reduce the stoppage time connected with the necessity to remove the mould from
press, uninstall the worn-out inserts, and install new ones. This allowed also to
reduce significantly consumption of expensive tool steel of which the monolithic mould
inserts were fabricated to date, subject to scrapping once their working surfaces
were deteriorated.
[0007] The subject of the invention is shown in its example embodiments on drawings, of
which Fig. 1 shows the insert for the mould used to form stampings in a perspective
view; Fig. 2 - the same insert in the front view; Fig. 3 - the same insert in vertical
cross-section along line A-A; and Fig. 4 - the frame of the mould for fabrication
of stampings, with rectangular die opening of the frame equipped with four inserts
provided with metallic coatings on their working surfaces, in a perspective view.
Example 1
[0008] The mould insert with extended service life for press-moulding of stampings out of
refractory materials constitutes a cuboidal solid made of NC 11 alloy steel with hardness
(60 ± 1)HRC which on one end of its inner surface 1 has a rectangular recess 2, whereas
on the whole of its outer surface 3, the solid is provided with a metallic coating
4 with thickness g = 0.2 mm and hardness of 2750HV joined permanently with said outer
surface. The metallic coating 4 is deposited on surface 3 of the insert by means of
plasma spraying a powder with grain size (45 ± 15) µm containing tungsten carbides
in a cobalt matrix whereas the powder contains 86% by weight of tungsten carbide and
14% by weight of cobalt in its composition creating thus a monolithic cuboidal solid.
Example 2
[0009] The mould insert described in the first example has a metallic coating 4 with thickness
g = 0.4 mm and hardness of 2785HV, whereas the powder with grain size (45 ±15) µm
contains in its composition 90% by weight of tungsten carbides and 10% by weight of
cobalt.
[0010] In an example embodiment of the mould for fabrication of stampings presented in Fig.
7, four monolithic mould inserts according to the invention having the form of plate-shaped
cuboidal solids and provided with metallic coating 4 on their outer working surfaces
are placed in a rectangular opening 5 of frame 6 of the mould used for fabrication
of stampings, said inserts being joined detachably by means of any known method with
walls 7 of the opening, as a result of which a die 8 is created increasing significantly
the service life of the mould.
1. A mould insert with extended service life for forming stampings by means of press
moulding, especially stampings formed from refractory materials in the form of powders
or granulates, constituting one of linings of the mould cavity side walls and made
of alloy steel in the form of cuboidal solid characterised in that its outer working surface (3) is joined inseparably with a metallic coating (4) with
thickness g = 0.2-0.4 mm and hardness of 2750-2785HV.
2. The mould insert according to claim 1 characterised in that the metallic coating (4) contains in its composition 86-90% by weight of tungsten
carbide and 10-14% by weight of cobalt.
3. The mould insert according to claim 1 or 2 characterised in that the 'inseparable joint of the outer working surface (3) of the insert with the metallic
coating (4) is made with the use of plasma-spraying a powder with grain size (45 ±
15) µm.
