Process including heating and cooling for production of an injection-moulded body

A process for production of a moulded ceramic and/or metallic body from a ductile material comprising one or more ceramic and/or metallic components, which material is fed into the pre-heated mould cavity (1) of a moulding tool. The moulded tool includes at least two mould parts (4, 5) of which at least one wholly or partly consists of a microporous material with communicating micropores. At least one mould cavity (1) comprising at least one mould surface (2, 3) exhibiting closed micropores is arranged in the microporous mould part (4, 5) or in a microporous section (6) thereof. The microporous mould part (4, 5) or the microporous section (6) thereof is pre-heated by supply of warm fluid, such as a heated gas. Said part (4, 5) or section (6) is after terminated moulding cooled by supply of cold fluid, such as a condensed gas. the invention includes in a further aspect a moulded body produced according to the process.

BACKGROUND OF THE INVENTION 
The present invention relates to a process for production of a moulded 
ceramic and/or metallic body. The basic material is a ductile material 
comprising one or more ceramic and/or metallic components, such as 
particles, which are mixed or coated with at least one binder and fed into 
a pre-heated mould cavity of a moulding tool. The mould cavity of said 
moulding tool is enveloped by at least two mould parts of which at least 
one wholly or partly consists of a microporous material with communicating 
pores, which mould part is pre-heated by supply of warm fluid and after 
terminated moulding cooled by supply of cold fluid. The invention include 
in a further aspect a moulded body made according to the procedure. 
It has for a long time been known to manufacture moulded bodies using 
various moulding procedures, such as injection moulding, extrusion, blow 
moulding or casting. The basic material is usually a ductile material 
consisting of ceramic or metallic powders or particles and one or more 
binders, additives and the like. A common procedure in making ceramic or 
metallic moulded bodies often comprises three steps. The first step is the 
moulding, whereby the ductile material is shaped in the mould of a 
moulding tool. A second step implies evaporation of binders, additives 
etc. included in the ductile material. The procedure is terminated by a 
particle compression, such as a sintering. 
The procedure as above typically starts with a mixing or coating of the 
ceramic or metallic powder or particles with a binder system comprising 
for example at least one polymer, such as thermosets and thermoplastics, 
and one or more additives having lubricating properties, such as waxes and 
stearates. The binder system can suitably be liquid per se or be in a 
liquid state, such as a solution or a fuse. The mixture is heated, 
typically.apprxeq.150.degree. C., to a consistency allowing injection and 
is thereafter fed, for instance by means of an extruder, into the mould 
part or parts, normally a mould cavity, of a moulding tool, wherein the 
binder physically, chemically or thermally is transformed into a solid 
state, and a moulded body consisting of for instance particles bonded 
together by the binder is obtained. The moulded body is cooled and 
released from the moulding tool. Binders and additives included in said 
moulded body are removed by suitable methods, such as heating, freeze 
drying or vaporisation, whereby a moulded body substantially bonded by 
particle bodying is obtained. The binder content is here normally less 
than 5%. Obtained moulded body can now be sintered using various sintering 
procedures, including among others dense sintering, liquid phase 
sintering, solid phase sintering, exogas and endogas sintering, reaction 
sintering, pressure sintering, vacuum sintering, selected laser sintering, 
microwave sintering and activated sintering. The three hereby disclosed 
steps can be performed directly after each other in a linked manufacturing 
unit or be performed at different occasions and in separate units, whereby 
each of the various stages of the moulded body can be further treated 
and/or worked. 
It has also for a long time been known to pre-heat a moulding tool at 
production of metallic and ceramic moulded bodies. Such a pre-heating is 
normally obtained by heated oil or water circulating in a pipe system. 
Pre-heating can also be performed by means of for example an electric rod 
or other electro-heating. It is furthermore known to cool a moulded body 
after terminated moulding by means of cold water. Microporous mould parts 
having microporous mould surfaces, which mould parts can be heated and/or 
cooled through communicating pores have for some time been used in 
connection with moulding of thermosets and thermoplastics. 
Cyclic temperature regulation, of a moulding tool, alternating between a 
cold state, a heated state and back to a cold state and so on, are 
demanding reasonable cycle times not possible using said oil and water 
systems. The problem is known from the manufacturing of thermosets and 
rubbers, both requiring heated moulds for respective reaction and curing 
mechanism during the moulding. Regulation in such intervals of the 
temperature in a metallic or ceramic moulded body with reasonable heating 
and cooling times is due to conductive heat transport very difficult and 
has so far been a bar to maximised and rational utilisation of moulding 
tools. A heated mixture of ceramic or metallic particles, binders, 
additives etc. is when fed into a cold, a comparatively cold or an 
unevenly heated mould partly cooled and a skin formed on its surface 
facing the mould. This gives rise to a complexity of undesired side 
effects, such as inner tension due to differences between surface and core 
temperature, corrugation due to shear strain changes, uneven particle 
distribution in the moulded body due to particle piling in parts having 
reduced temperature. Corrugation can, furthermore, primarily or 
secondarily cause for instance defects in the surface finish and/or imply 
difficulties in the production a moulded body of complex geometry. Inner 
tensions and uneven particle distribution result in moulded bodies and 
articles having an uneven and/or inferior quality. 
The demand for a more even heating of the mould surface(s) of a moulding 
tool and a more rapid as well as facilitated cycling between heated and 
cooled state, which means between pre-heating of for example the mould 
part(s) and/or surface(s) and cooling of the moulded body, is very 
pronounced. 
SUMMARY OF THE INVENTION 
The process according to the present invention quite unexpectedly makes it 
possible to obtain a rapid and simple cycling between heating and cooling 
of the mould cavity of a moulding tool. Pre-heating of the mould cavity is 
furthermore, very evenly distributed, whereby said undesired effects, such 
as differences in surface and core temperature, corrugation and uneven 
particle distribution are eliminated or substantially reduced. The process 
according to the present invention reduces the cycle. time in the 
production of ceramic and/or metallic moulded bodies. The even temperature 
distribution, makes it possible to produce a moulded body having a complex 
geometry and an increased surface finish from a ductile material having a 
decreased amount of binder(s), additive(s) and the like, whereby 
evaporation thereof furthermore is facilitated. 
The process according to the present invention relates to production of a 
moulded ceramic and/or metallic body. The moulded body is produced by 
means of a moulding procedure, such as an injection moulding, a blow 
moulding, a gas injection moulding, an extrusion or a casting, from a 
ductile material comprising one or more ceramic and/or metallic components 
in form of a powder or particles, which components have been mixed or 
coated with at least one binder and optionally at least one property 
adjusting additive, such as waxes and stearates. The process comprises one 
or more steps. The ductile material is in a first step (a) moulded by 
being fed into one or more, preferably 1-160, such as 1, 2, 4, 8, 16, 32, 
64 or 96, mould cavities in a moulding tool, said cavities comprising one 
or more mould surfaces and being enveloped by at least two mould parts, of 
which at least one mould part wholly or partly consists of a microporous 
sintered material with communicating pores. The microporous mould part is 
provided with at least one means for supply of warm and/or cold fluid. The 
wholly or partly microporous mould part comprises, in at least one 
microporous section, one or more mould surfaces exhibiting substantially 
closed pores. The wholly or partly microporous mould part is, furthermore, 
provided with at least one outer surface, which wholly or partly exhibits 
substantially open pores and/or is provided with at least one outlet for 
evacuation of supplied fluid. At least one mould surface of at least mould 
cavity, which cavity is a part of a wholly or partly microporous mould 
part, is before feeding of ductile material and, optionally, at least 
initially during the subsequent process, heated by supply of warm fluid. 
Said surface is, after said feeding of ductile material, cooled in the 
closed moulding tool by supply of cold fluid to the micropores. Particles, 
binders and optional additives are, through heating by means of supplied 
warm fluid, bonded to a moulded body, whereby at least one in the ductile 
material included binder from a liquid or an intermediate liquid state 
physically, chemically and/or thermally is transformed into a solid state. 
The mould parts can, in various embodiments, each and independently be 
heated by means of warm fluid and/or electrically. 
The first step (a) can optionally be followed by a second step (b), whereby 
in the moulded body included binder(s) and/or additive(s) wholly or partly 
are removed by heating; freeze drying; solvent leaching, soaking or 
maceration; evaporation under vacuum and/or heat; catalysed evaporation; 
or the like. A substantially by physical properties, such as particle 
bodying, bonded moulded body is thus obtained. The temperature during heat 
induced evaporation is normally within 100-500.degree. C., such as 
200-300.degree. C. or preferably 200-300.degree. C., whereby the metallic 
and/or ceramic particles are pre-sintered. 
The moulded body obtained according to step (a) or (b) is during an 
optional third step (c) sintered, whereby particle compression produces a 
sintered moulded body. Said sintering in said step (c) is preferably a 
dense sintering, a liquid phase sintering, a solid phase sintering, an 
exogas or an endogas sintering, a reaction sintering, a pressure 
sintering, a vacuum sintering, a selected laser sintering, a microwave 
sintering or an activated sintering. A suitable sintering temperature is 
normally within 500-3000.degree. C., such as 600-2500.degree. C. or 
preferably 800-2000.degree. C. Sintering is a procedure wherein a material 
in form of particles during heating or furnacing under atmospheric 
pressure, overpressure or vacuum with or without protective gas is 
compressed, whereby interparticle bonds are formed and the particles are 
transformed into a solid mass. Available and common sintering atmospheres 
are endotherm and exotherm gases (endo and exogases). Endo and exogases 
are normally produced by allowing a hydrocarbon catalyst to react at an 
elevated temperature with a pre-determined amount of air, whereby mainly 
H.sub.2, N.sub.2, CO and minor amounts of CO.sub.2, CH.sub.2 and H.sub.2 O 
are formed. Production of endogases requires compared to exogases a higher 
amount of air in relation to hydrocarbon. 
Common and in metallic and/or ceramic moulded bodies and hence in above 
disclosed ductile material used metals and/or ceramics are for instance 
iron, cobalt, tungsten, molybdenum, vanadium, bismuth, niobium, tin, 
titanium, nickel, tantalum, zirkonium, aluminium, alloys and mixtures 
thereof and therewith, calcite, kaolin, alum, China clay, quarzite, 
chromite, magnesite, magnetite, silicon dioxide, silicon carbide, silicon 
nitride, boron carbide, boron nitride and/or mixtures thereof and 
therewith. These compounds are also commonly used in combinations with 
carbon and/or graphite. Metals can, furthermore, be used as oxides, 
carbides, nitrides and similar compounds. Mixtures of various metals, 
metal alloys and/or ceramics are advantageously used for various 
speciality application and to provide a moulded body or an article 
produced therefrom with specific and/or specified properties. 
The present invention provides an excellent and even pre-heating as well as 
heating of the mould surface or surfaces of a moulding tool, implying that 
the ductile material advantageously, in stead of or in combination with 
polymers such as thermosets and thermoplastics, can comprise ceramic and 
metallic binding materials including bentonite, silicates of soda, low 
temperature melting metals or metal alloys, such as Woods metal, Roses 
metal and alloys of copper, lead, tin and zinc. The low temperature 
melting metal or metal alloy has preferably a melting point of at most 
150.degree. C. Above type of ceramic and metallic binders can, where 
possible or suitable, be present as a powder or as particles. The ductile 
material typically comprises 30-99, preferably 60-90, per cent by volume 
of metal and/or ceramic particles having a particle size of less than 300 
pm, such as 1-10 .mu.m or 100-200 .mu.m, while the binder content is 1-70, 
preferably 10-40, per cent by volume. 
In various embodiments of the present invention are at least the mould 
surface or surfaces, arranged in a wholly or partly microporous mould 
part, prior to feeding of ductile material to the mould cavity or 
cavities, and optionally during some part of the subsequent process, 
heated to a temperature of 50-300.degree. C., preferably 90-250.degree. 
C., by supply of warm fluid. The warm fluid is supplied through one or 
more capillary tubes or channels or through at least one gap, slit or 
channel arranged between a microporous section and a substantially solid 
section of said mould part. Said mould surface can alternatively be heated 
to said temperatures by supply of warm fluid directly into the cavity 
through a slit, channel or gap between two mould parts, through capillary 
tubes or through the gate of the moulding tool. The warm fluid is in 
preferred embodiments a heated gas, such as air, air mixtures; carbon 
dioxide; nitrogen; hydrogen; an inert gas, for instance helium or argon; 
and/or mixtures thereof and therewith. The warm fluid can also be heated 
water or oil, such as a mineral oil, a triglyceride or an equivalent fatty 
acid ester. Further suitable heating methods include electro-heating and 
the like. The choice of heating method is among other reasons influenced 
by the geometry of produced moulded body and used moulding tool and 
procedure. After feeding of ductile material into the closed moulding 
tool, are at least the mould surface or surfaces arranged in a wholly or 
partly microporous mould part cooled, preferably at least 20.degree. C. in 
relation to its temperature as heated, by supply of cold fluid to the 
micropores of said mould part. The cold fluid is supplied through one or 
more capillary tubes or channels or through at least one slit, channel or 
gap arranged between a microporous section and a substantially solid 
section of said mould part. The cold fluid is preferably a condensed gas, 
such as carbon dioxide, nitrogen or air. Cooling is a results of condensed 
gas expanding inside the micropores of the mould part. Supplied warm or 
cold gas is suitably evacuated by means of one or more capillary tubes or 
slits or by means of diffusion via the open micropores of the wholly or 
partly microporous mould part. 
Warm and cold gaseous fluid is suitably supplied in cycles at a pressure of 
2 to 70, preferably 5 to 60, bars, whereby cold fluid is forced out by 
warm fluid and warm fluid by cold fluid. Supply and evacuation can be made 
jointly or separately by means of for instance capillary tubes, channels 
and/or slits with or without one or more networks of guiding valves. The 
herein disclosed method of heating and/or cooling of one or more mould 
surfaces utilises conductive as well as convective heat flow increased by 
the large flow areas provided by micropores. This makes a rapid cycling 
between a warm and a cold state possible and provides an improved and more 
even heating and cooling, whereby previously discussed advantages are 
obtained and previously disclosed problems are avoided. 
The wholly or partly microporous mould part is preferably made of a 
microporous sintered metal produced from steel particles or powder, such 
as iron based carbon steel, stainless steel and high-tech steel alloys, 
preferably containing titanium, nickel, chromium, tungsten and/or 
molybdenum. The closed micropores of a mould surface are suitably obtained 
mechanically, by heat treatment or by surfacing a 2 .mu.m to 2 .mu.m, 
preferably 2 to 500 .mu.m, layer of titanium, nickel, chromium, titanium 
carbide, titanium nitride and/or aluminium trioxide. A surfacing is 
preferably a vacuum surfacing, such as a chemical or physical gas 
surfacing including evaporation, deposition, ion plating and sputtering, 
such as reactive magnetron sputtering. Chemical gas surfacing means that 
said layer is formed by deposition of chemical reaction products resulting 
from a high temperature process. The temperature is normally 
800-1300.degree. C. Physical gas surfacing can generally be divided into 
the three main groups evaporation, sputtering and ion plating. A physical 
gas surfacing is characterised in that a solid substance (a starting 
material) is transformed to a layer on an object according to following 
general procedure: Solid 
phase.fwdarw.evaporation/sputtering.fwdarw.gaseous phase.fwdarw.condensati 
on.fwdarw.solid phase. The composition of the surfaced layer need not be 
the same as that of the starting material. The evaporated starting 
material can be allowed to react with for instance a reactive gas. 
Transformation of the starting material into gaseous state can be done by 
resistance heating or by means of an electron gun. Evaporation can also be 
performed by so called sputtering, meaning that atoms are ejaculated by 
means of bombarding argon ions. 
A moulding tool having at least one wholly or partly microporous mould part 
comprising at least one mould surface exhibiting closed pores is used in 
preferred embodiments of the process. Nothing prevents, however, where 
applicable, suitable and/or in order to obtain a maximised heating and/or 
cooling, the use of a moulding tool wherein all parts or, preferably, all 
in the moulding process participating parts are porous or microporous. The 
mould surface or surfaces can in certain embodiments exhibit open pores. 
The outer surface of a microporous section included in a mould part can 
according to one embodiment of the process exhibit a sealed or tightened 
surface with closed pores, whereby supplied warm or cold fluid is 
evacuated via one or more outlets arranged therein. Suitable outlets are 
for instance capillary tubes or the like, preferably being tightened 
towards said outer surface. 
In a further aspect, the invention refers to a moulded body produced by the 
process of the present invention. The moulded body comprises one or more 
metallic and/or ceramic components and is produced by moulding a ductile 
material comprising one or more ceramic and/or metallic powders or 
particles, preferably having a particle size of 1-300 .mu.m, such as 1-10 
.mu.pm or 100-200 .mu.m. The particles have been mixed or coated with at 
least one binder and optionally at least one property adjusting additive, 
whereby the metallic and/or ceramic content is 30-99, preferably 60-90, 
per cent by volume while the binder content is 1-70, preferably 10-40, per 
cent by volume. The moulding is performed according to previously 
disclosed step (a) of the process. The content of binder and additive can 
optionally, as disclosed in step (b) of the process, be removed and the 
from step (a) or (b) resulting moulded body can optionally and in 
accordance with step (c) of the process be sintered. 
A sintered moulded body produced according to the process of the present 
invention can in its various embodiments advantageously be used in a large 
number of industrial application areas, including machinery and parts 
thereto, such as gear, cog, paddle, blade and turbine wheels as well as 
shafts thereto. 
Further application areas are for instance drilling, milling, lathery and 
grinding tools and tooling. Suitable application areas are also permanent 
magnets and filaments.

The various parts of FIGS. 1-3 are not entirely according to scale. Some 
parts are, to facilitate reading, enlarged or reduced. The moulding tools 
of FIGS. 1-3 are used in various embodiments of step (a) of the process of 
the present invention. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a skeleton drawing of two mould parts 4, 5 being included in a 
moulding tool. One mould part 4 is entirely solid (steel) and one mould 
part 5 comprises a solid (steel) section 8 and a microporous (sintered 
steel) section 6. The microporous section 6 is an insert in the solid 
section 8. The insert is supported by steel bosses 20 and rests on two 
ceramic beds 22. A channel 10 between the solid section 8 and the 
microporous section 6 encircles said microporous section 6. Warm fluid for 
heating is supplied to the channel 10 and thus the microporous section 6 
via a capillary tube 9 provided with a valve 14 and evacuated on the 
opposite side of the channel 10 through a capillary tube 9' provided with 
a valve 14'. The valve 14' is during supply of warm fluid preferably shut. 
Supplied warm fluid is distributed inside the microporous section 6 by 
penetrating its outer surface 11, which surface 11 exhibits open pores. 
Supplied warm fluid is removed by means of diffusion or is forced out of 
the pores of section 6 by a supply of cold fluid. Between the microporous 
section 6 and the solid section 8, embedding the channel 10, is 
furthermore an insulating ceramic layer 19. The microporous section 6 
comprises a mould cavity I having a mould surface 2 exhibiting closed 
pores. The closed pores have been obtained by a surfaced 10 pm nickel 
layer 16. The mould part 4 has a mould surface 3, without any surfaced, 
coated or otherwise applied layer. Cold fluid for cooling is supplied to 
the micropores of section 6 via a capillary tube 7 provided with a valve 
14", which capillary tube 7 ends in an expansion cavity 17 beneath the 
outer surface 11 of the microporous section 6. The valves 14, 14' can 
during supply of cold fluid independently be open or shut. The cold fluid 
expands in the expansion cavity 17, whereby providing a strong cooling 
effect. Said cold fluid penetrates into and is distributed inside the 
micropores of section 6. Cold fluid can be removed by means of diffusion 
or be forced out of the micropores by supply of warm fluid and is 
evacuated through the channel 10 and the thereto attached capillary tubes 
9 and/or 9'. Heating and cooling can, due to the fact that the capillary 
tubes 7, 9, 9' each is provided with a valve 21, 14, 14', be controlled 
according to requirement by adjustment of supplied and/or evacuated amount 
of warm and/or cold fluid. The solid section 8 and the mould part 4 are, 
furthermore, electrically heated by heating devices 12. A ductile material 
to be moulded is fed into the cavity I via a gate 15. The gate 15 can 
also, if so is desired and/or suitable, be used for heating of the cavity 
1. Warm fluid is then, prior to feeding of the ductile material, supplied 
directly into the cavity I through the gate 15 by means of one or more 
tubes, channels, hoses or other suitable piping. 
FIG. 2 shows a skeleton view of two mould parts 4, 5 being included in a 
moulding tool. The mould parts 4, 5 are both completely microporous 
(sintered steel) and enveloped by a solid steel frame 18. Warm fluid for 
heating is supplied to respective micropores of said mould parts 4, 5 
through capillary tubes 9 each provided with a valve 14 and evacuated on 
the opposite side through capillary tubes 9' each provided with a valve 
14'. The valves 14' is during supply of warm fluid preferably shut. 
Supplied warm fluid is distributed inside the mould parts 4, 5 by 
penetrating respective outer surface 11, 11', which surfaces 11, 11' 
exhibit open micropores. Supplied warm fluid is removed by means of 
diffusion or is forced out of the micropores by supply of cold fluid and 
is evacuated through said capillary tubes 9'. The mould parts 4, 5 
comprise a mould cavity 1, having mould surfaces 2, 3 exhibiting closed 
pores. The closed pores are obtained by a surfaced 50 .mu.m layer 16 of 
aluminium trioxide. Cold fluid for cooling is supplied to the micropores 
of respective mould part 4, 5 through capillary tubes 7, 7', each provided 
with a valve 21 and 21' and each ending in an expansion cavity 17 and 17'. 
The cold fluid expands in the expansion cavities 17 and 17', whereby 
providing a strong cooling effect. Said cold fluid penetrates into and is 
distributed inside the pores of respective mould parts 4 and 5. Cold fluid 
can be removed by means of diffusion or be forced out of the pores by 
supply of warm fluid and is evacuated through the capillary tubes 9 and/or 
9'. Heating and cooling can, due to the fact that the capillary tubes 7, 
7' 9, 9', each is provided with a valve 21, 21' 14, 14', be controlled 
according to requirement by adjustment of supplied and/or evacuated amount 
of warm and/or cold fluid. A ductile material to be moulded is fed into 
the cavity 1 via a gate 15. The gate 15 can also, if so is desired and/or 
suitable, be used for heating of the cavity 1. Warm fluid is then, prior 
to feeding of the ductile material, supplied directly into the cavity I 
through the gate 15 by means of one or more tubes, channels, hoses or 
other suitable piping. 
FIG. 3 shows a skeleton view of two mould parts 4, 5 being included in a 
moulding tool. One mould part 4 is entirely solid (steel) and one mould 
part 5 comprises a solid (steel) section 8 and a microporous (sintered 
steel) section 6. The microporous section 6 is an insert in the solid 
section 8. Warm fluid for heating is supplied to the microporous section 6 
through a capillary tube 9 provided with a valve 14 and evacuated on the 
opposite side of the microporous section 6 through a capillary tube 9' 
provided with a valve 14'. The valve 14' is during supply of warm fluid 
preferably shut. Supplied warm fluid is distributed inside the microporous 
section 6 by penetrating its outer surface 11, which surface 11 exhibits 
open micropores. Supplied warm fluid is removed by means of diffusion or 
is forced out of the micropores of section 6 by supply of cold fluid. The 
microporous section 6 comprises a mould cavity I having a mould surface 2 
exhibiting closed pores. The closed pores have been obtained by a surfaced 
25 .mu.m nickel layer 16. The mould part 4 has a mould surface 3, without 
any surfaced, coated or otherwise applied layer. Cold fluid for cooling is 
supplied to the micropores of section 6 via a capillary tube 7 provided 
with a valve 21, which capillary tube 7 ends in an expansion cavity 17 
beneath the outer surface 11 of the microporous section 6. The valves 14 
and 14' can during supply of cold fluid independently be open or shut. The 
cold fluid expands in the expansion cavity 17, whereby providing a strong 
cooling effect. Said cold fluid penetrates into and is distributed inside 
the micropores of section 6 and can be removed by means of diffusion or be 
forced out of the micropores by supply of warm fluid. Cold fluid is 
evacuated through the capillary tube 9 and/or 9'. Heating and cooling can, 
due to the fact that the capillary tubes 7, 9, 9' each is provided with a 
valve 21, 14 and 14' be controlled according to requirement by adjustment 
of supplied and/or evacuated amount of warm and/or cold fluid. The mould 
part 4 are, furthermore, water cooled, whereby the water is supplied 
through water inlets 23. The solid section 8 of the mould part 5 is also 
water cooled through water inlets 23 and in addition thereto internally 
arranged water channels 13. A ductile material to be moulded is fed into 
the cavity I via a gate 15. The gate 15 can also, if so is desired and/or 
suitable, be used for heating of the cavity 1. Warm fluid is then, prior 
to feeding of the ductile material, supplied directly into the cavity 1 
through the gate 15 by means of one or more tubes, channels, hoses or 
other suitable piping. 
EXAMPLE 
A moulding tool, similar to that disclosed in FIG. 1, comprising two mould 
parts 4, 5 was used One mould part 4 was entirely solid (steel) and one 
mould part 5 consisted of a solid section 8 and a microporous section 6, 
which section 6 comprised a mould cavity I having a mould surface 2 
exhibiting closed micropores in accordance with FIG. 1 and an outer 
surface 11 exhibiting open micropores. The microporous section 6 was an 
insert in the solid section 8. The moulding tool was provided with means 
7, 9, 9' and 10 for supply and evacuation of cold and warm fluid. 
The moulding tool was closed and warm carbon dioxide, 160.degree. C., was 
supplied to the microporous section 6 through a capillary tube 9' and a 
channel 10 arranged between said microporous section 6 and said solid 
section 8 of mould part 5. The warm carbon dioxide was immediately 
distributed in the micropores of section 6, whereby a strong heating was 
obtained. The temperature in section 6 was rapidly raised to 
100-110.degree. C. A ductile material was now injected through a gate 15 
into the mould cavity 1. Said ductile material consisted of particles of 
tungsten carbide homogeneously suspended in molten polyethylene with an 
addition of lubricating wax. Cold fluid, condensed carbon dioxide, was 
after terminated injection supplied to the micropores through a from below 
towards the outer surface 11 of section 6 directed capillary tube 7. The 
capillary tube 7 ended a small distance beneath the outer surface 11 in an 
expansion cavity 17. The cold carbon dioxide expanded in said expansion 
cavity 17 and a strong cooling effect was obtained. The moulding tool was, 
when the temperature had decreased 100.degree. C. and the binder had 
obtained a solid state, opened and the thus resulting moulded body was 
ejected. Heating by supply of warm carbon dioxide was immediately 
re-commenced and the moulding process repeated. 
Cooling and heating was controlled by a thermoelement arranged inside the 
mould cavity I and the amount of supplied warm and cold carbon dioxide was 
adjusted by a supervising unit arranged outside the moulding tool. The 
supervising unit co-operated with the thermoelement and a number of valves 
14, 14', 21. 
The cycle time of above injection moulding was 8-10 seconds. 
While particular embodiments of the invention have been shown, it will be 
understood, of course, that the invention is not limited thereto since 
many modifications may be made, and it is, therefore, contemplated to 
cover by the appended claims any such modifications as fall within the 
true spirit and scope of the invention.