ES2410904A1 - Device and procedure for using the same for the infiltration of porous preforms with metal liquid high pressure steam. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Device and procedure for its use for the infiltration of porous preforms with liquid metals of high vapor pressure, this being greater than 10-3 mm hg, which is mounted inside an infiltration chamber conventional and comprises a porous preform, an infiltration crucible that houses in turn said porous preform and the metal that will be infiltrated therein by gas pressurization, a saturation crucible arranged in such a way that it is inverted with respect to the infiltration crucible covering it and thus forming a closed saturation chamber, simple to assemble, adaptable to any conventional infiltration device and which avoids appreciable losses of metal, thus enabling the process of infiltration of the metal into the porous space of the preform. (Machine-translation by Google Translate, not legally binding)

Description

DEVICE AND PROCEDURE FOR USING THE SAME FOR INFILTRATION OF POROUS PREFORMS WITH METALS HIGH PRESSURE VAPOR LIQUIDS

TECHNICAL FIELD OF THE INVENTION

The present invention is encompassed in the field of metal matrix composites.

Said invention is a device and the method of using it for the infiltration of porous preforms with high vapor liquid pressure metals, this being greater than 10-3 mm Hg, which is mounted inside a conventional infiltration chamber and it comprises a porous preform, an infiltration crucible that houses said porous preform and the metal that will be inflated therein by gas pressurization, a saturation crucible arranged in such a way that it is inverted with respect to the infiltration crucible covering it and thus forming a closed saturation chamber, simple to assemble, adaptable to any conventional infiltration device and that avoids appreciable losses of metal, thus enabling the process of infiltration of the metal into the porous space of the preform.

BACKGROUND OF THE INVENTION

Metal matrix composites have been known for more than 4 years. Since then there have been many manufactured materials, as well as technologies to manufacture them.

The technologies that have been developed have been adapted to the characteristics of the material that was intended to be manufactured, depending on the type of matrix and reinforcement, fraction and morphology of the reinforcement, physical-chemical compatibility of the components, etc.

A device for manufacturing composite materials by gas infiltration is disclosed in US3547180. Other general descriptions of different devices can be found in the following documentation:

D. Hull, T.W. Clyne, "An Introduction to Composite Materials" Cambridge University Press, second edition, 280 (1996); K.K. Chawla, "Composite Materials" Springer, second edition, 168 (1998); R. Asthana, "Solidification Processing of Reinforced Metals" Trans. Tech. Publications, 6 (1998).

The wide variety of technologies developed is based on the different methods in which a discrete reinforcement, eg particles, fibers, etc., can be combined with a metal to consolidate a material with modified final properties.

Thus, different technologies make use of

techniques

from infiltration, "compo-casting", "spray depo

sition ",

etc. From all the technologies developed,

alone

the infiltration he has acquired importance indus

trial.

The techniques for infiltration are also very varied: gas pressure infiltration, mechanical pressure infiltration, the technique known as "drain casting", etc.

In particular, infiltration at low pressure or gas pressure has many advantages over the

rest and that is why it has been object, with much different

rencia, of an extraordinary development in recent

years.

5

Most of the various development technologies

calls and patented by companies and laboratories during

the last 25 years have been based on the technique of

Low pressure gas infiltration.

10

In all of them the following elements participate

common cough:

a) porous preform that will be infiltrated by the

metal and that can be manufactured in many different ways;

b) container with the liquid metal;

fifteen

c) pressure vessel where the pre

porous form and liquid metal, producing the infil

traction by pressurized gas inlet.

The arrangement of the components and performs

2 o

The infiltration process has been and is an object

of different patents.

The most common method of performing the process of

infiltration is as follows:

25

a) the preform is emptied; in some cases

when the preform is empty it is also done in

the whole set;

b) both the preform and the metal are heated;

in some cases both are at the same temperature

30

tura and in others the preform is at a temperature

tura lower than metal;

c) the metal melts and contacts

the preform; in some devices the metal flows through

yes only to make contact with the preform and in others

35

devices the metal needs a mechanical effort or

hydraulic until you reach the receptacle where you are

tra preform;

d) pressure is applied to the liquid metal so that

it penetrates the porous structure of the preform and

5

then it cools in a directional or multidirectional way

the crucible containing the composite material thus manufactured

fallen

The different patents that protect these challenges

the

Technology rolls cover different devices

Experiments and methods for the manufacture of matter

the metal matrix compounds in which the metal is

has chosen from among the most commonly used in

Industry for various purposes.

fifteen

Thus, for example, the patent of

US3547180 exclusively covers the aluminum metal (Al).

However, due to the increasing number of applications

twenty

cations that have been derived from composite materials

cough has seen the need to protect metals like

silver (Ag), copper (Cu) or magnesium (Mg), as cited in

PCT / ES2008 / 000146, US20080050589,

US6355340, US5511603, US6599466 and US5672433.

25

In particular, Mg has acquired a large relay

due to its low density and its properties

Mechanical and thermomechanical. In all these patents the

variety of protected reinforcements is remarkable; yes well in

30

all the cases cited are used Mg and the technique of

infiltration are very few cases in which

provides an example of manufacturing a composite material

To with this metal.

35

This is because the protected devices

They are adapted to the manufacture of composite materials with Al but do not take into account the peculiarities of Mg that make their manufacture through the infiltration technique with these devices impracticable.

Mg, as well as many other metals, has the peculiarity of having a high vapor pressure. In addition, in the liquid state it acquires a high reactivity, being able to react violently with the oxygen and water vapor of the environment. These characteristics mean that Mg and metals with similar properties cannot be processed in oxidizing or vacuum atmospheres and need specifically adapted technologies.

These considerations have in many cases been directly obviated, and it can be demonstrated that experimentally it is impossible to manufacture Mg matrix composites (and by extension, of metals with high vapor pressure and / or with high affinity for oxygen in liquid state) With patented technologies.

For example, the open mold device proposed in U85672433 for working with Mg is unfeasible as it is protected, since it does not prevent Mg in liquid state from being in contact with air. In other cases, these problems have been minimized by proposing the manipulation of the infiltration atmosphere in two stages:

i) in a first stage it becomes empty and is maintained until the metal melts;

ii) in a second stage a certain pressure is applied with an inert or protective gas, the use of which in many cases is regulated because they are classified

Two as greenhouse gases.

The problem with this method is that it is impossible to avoid a considerable evaporation of the high vapor pressure metals during the time between its fusion and the application of the gas

inert.

A consequence from this is the lost from a

volume

important from metal (the which impossible its

infiltration)

Y the serious deterioration that it causes its

deposition in the coldest parts of the infiltration equipment.

The use of the above devices for the infiltration of alloys containing high vapor pressure alloying elements presents the same problems. In these cases, the most volatile species are the most rapidly vaporized and deposited in the components of the devices that work at a lower temperature. To put an example, it is common when working with Al-Mg alloys to find metal deposits rich in Mg in the walls of the infiltration chamber, vacuum application tubes and electrical terminals.

In the case of copper and chromium alloys (Cu-Cr), an excess amount of alloy is usually added to cover the losses that are caused during the infiltration process due to the fact that a large part of the highly oxidizable elements (in this case, Cr) are transformed into their respective oxides.

A new technology is therefore necessary for the manufacture of composite materials by infiltration in porous media of liquid metals with high vapor pressure.

This patent exposes the invention of a device and the method of using it for the infiltration of porous preforms with high vapor liquid pressure metals, this being greater than 10-3 mm Hg, which is mounted inside a chamber of pressure and comprises a porous preform, an infiltration crucible that in turn houses said porous preform and the metal that will be infiltrated therein by gas pressurization, a saturation crucible arranged in such a way that it is inverted with respect to the infiltration crucible covering it and thus forming a closed saturation chamber, simple to assemble, adaptable to any conventional infiltration device and that avoids appreciable losses of metal, thus enabling the process of infiltration of the metal into the porous space of the preform.

DESCRIPTION OF THE INVENTION

The present invention is established and characterized in the independent claims, while the dependent claims describe other features thereof.

In view of the foregoing, the present invention relates to a device for the infiltration of porous preforms with liquid metals of high vapor pressure, this being greater than 10-3 mm

Hg

Said device comprises different elements: a porous preform, an infiltration crucible that

it also houses said porous preform and the liquid metal that will be infiltrated therein, the infiltration being produced by pressurized gas.

The device further comprises a saturation crucible arranged in such a way that it is inverted with respect to the infiltration crucible covering it and thus forming a closed saturation chamber.

An advantage of the device is the easy assembly and disassembly because it consists only of the sliding of two crucibles.

Another advantage is that saturation of the chamber in metallic vapor prevents significant volumetric losses of the metal by evaporation.

In addition, due to its simplicity, it can be adapted in any conventional infiltration device or machine without covering the infiltration crucible with another saturation crucible.

Also, the invention relates to a method of using the device described above and comprising the following steps:

a. arrangement of the porous preform inside the infiltration crucible, and the infiltrating metal in its upper part above said porous preform,

b.arrangement of inverted saturation crucible

covering

he melting pot from infiltration with the function from

create

a camera from saturation closed for achieve the

saturation of

metallic steam,

C. vacuum application to said device until

a value below 50 mbar, d. increase in the temperature of the device to at least the melting temperature of the metal,

and. increase of the internal pressure of the device chamber by applying pressurized gas to the infiltration machine where the device is installed to force the liquid metal to infiltrate inside the porous preform,

f. solidification of liquid metal.

An advantage of such a procedure is that because the free space in the closed chamber is controllable and limited saturation in metallic vapor will be achieved before the metal losses are significant.

Another advantage is that when working in a vacuum, it is possible to work with metals with a high affinity for oxygen in the liquid state, since oxidation is no longer a problem since the vacuum acts as if it were a reducing atmosphere.

Another advantage is that it prevents the deposition of the metal in the components of the device since the closed saturation chamber acts as a hot trap for the metallic vapor preventing its deposition and subsequent evaporation.

BRIEF DESCRIPTION OF THE FIGURES

The present specification is complemented with a set of figures, illustrative of the preferred example, and never limiting the invention.

Figure 1 represents a sectional view of the

device.

DETAILED EXHIBITION OF THE PREFERRED EMBODIMENT OF THE INVENTION

The present invention consists of a device for the infiltration of porous preforms with liquid metals of high vapor pressure and a method of use thereof.

With high vapor pressure, the higher than 10-3 mm Hg is specified.

Said device (1) comprises different elements: a porous preform (2), an infiltration crucible (3) which in turn houses said porous preform (2) and the liquid metal (4) that will be infiltrated into the mymema, producing the infiltration by pressurized gas and a saturation crucible (5) arranged in such a way that it is inverted with respect to the infiltration crucible (3) covering it and thus forming a closed saturation chamber (6).

In short, the device introduces a closed saturation chamber (6), which is the space enclosed between the infiltration crucible (3) and the easily removable saturation crucible (5), which can be understood as a hot trap for metallic vapor generated inside. This closed saturation chamber (6) prevents the metal from evaporating by means of saturating the medium in metallic vapor, so as to avoid appreciable volumetric losses of the metal.

Due to its simplicity, it can be adapted in which

Any conventional infiltration machine. Said adaptation results from covering the infiltration crucible (3) containing the porous preform (2) to be infiltrated and the infiltrating metal with another inverted saturation crucible (5) that is adjusted as much as possible to the previous one. In this way the porous preform (2) and the metal are enclosed in the closed saturation chamber (6) whose assembly and disassembly only involves the sliding of both crucibles, infiltration crucible (3) and saturation crucible (5) with each other. .

Additionally, to ensure the functionality of the closed saturation chamber (6), a machined piece of thermal insulating material that acts as a hood, not shown in the figures, can be placed on the saturation crucible (5) inverted in the upper part of the device, in order to keep said crucible always at a higher temperature than the rest.

The resulting device can be introduced into any conventional infiltration chamber to which vacuum can be applied, raise the temperature and apply pressure by means of a gas.

The material from which the infiltration crucible (3) is made is preferably selected from the following group: commercial steel, graphite, high density ceramic of type A1203 or Si02. In addition, said material may be superficially modified to avoid any chemical reaction with the infiltrating metal.

The material from which the saturation crucible (5) is made is preferably selected from the following group: commercial steel, graphite, high density ceramic of type A1203 or Si02. In addition, said material may be superficially modified to avoid any chemical reaction with the infiltrating metal.

The material from which the thermal insulation hood is made, if used covering the saturation crucible (5), is preferably selected from the following group: high or low density ceramic type A1203 or Si02, base ceramic A1203 or Si02 of porous texture and high machining capacity.

High pressure liquid vapor metals

(Pv), this being greater than 10-3 mm Hg, they are preferably selected from the following group of pure metals or alloys that may contain them: Sr, Ca, Pb, Zn, Mg, Mn and Cr.

The infiltration crucible (3) is, in one embodiment, preferably flat base. The saturation crucible (5) is, in the same or another embodiment, preferably flat or hemispherical base. Also, this saturation crucible (5) has a contour preferably adaptable in ± O.lmm to the infiltration crucible

(3) .

The device usage procedure

(one)

understands the following stages:

to. provision

from the preform porous (2) in he

inside

of the melting pot from infiltration (3), Y of the metal

liquid

infiltrant in its part higher by over from

said porous preform

(2),

b. arrangement of the saturation crucible (5) inverted covering the infiltration crucible (3) with the function of creating a closed saturation chamber (6)

to achieve saturation of

metallic steam,

C. application

from empty to saying device (one)

until

a value below fifty mbar

d. increase

from the temperature of the device (one)

up to

less the temperature of fusion of metal,

E. Increase the internal pressure of the closed saturation chamber (6) of the device (1) by applying pressurized gas to the infiltration machine where the device (1) is installed to force the liquid metal to infiltrate inside of the porous preform (2),

f. solidification of liquid metal.

Between the stages c and d, another stage is added, which consists in the application of an inert gas in the closed saturation chamber (6) to a pressure lower than that of infiltration of the porous medium in order to avoid the subsequent evaporation of the metal due to the vacuum .

In the described process, vacuum heating achieves the evaporation of highly volatile metals. Since the metal is inside the closed saturation chamber (6) generated by both crucibles, infiltration crucible (3) and saturation crucible (5), the atmosphere of the medium will rapidly enrich the metal vapor until a balance is reached, thus stopping the evaporation of the metal. Since the free space in the closed saturation chamber (6) is controllable and generally very limited, metal vapor saturation will be achieved before the metal losses are significant.

The fact that the device allows to work in a vacuum provides multiple advantages in the case of working with metals with high affinity for oxygen

in a liquid state, since the partial pressure of oxygen in the closed saturation chamber (6) of infiltration is reduced so much that oxidation is no longer a problem for many metals.

These oxides are usually high melting compounds. In these cases, the presence of a closed saturation chamber (6) is of great help because as well as for the metallic vapor it acts as a trap

10 hot preventing its deposition and subsequent evaporation, for these oxides, with a high melting point, acts as a cold trap, consequently deposited on the inner walls of the inverted saturation crucible (5).

15 An extremely positive consequence is that, in any case, the device allows obtaining a composite material free of oxides.

20 Finally, a practical effect of great relevance is that this device completely prevents the metal from depositing in the different parts of the infiltration machine where it is installed.

Claims (11)

l.-Device

(one) for the infiltration from pre

shapes

porous with metals liquids from high Pressure from

steam,

being is higher to 10-3 mm Hg, that understands

different elements: a porous preform (2), an infiltration crucible (3) which in turn houses said porous preform (2) and the liquid metal (4) that will be infiltrated therein causing infiltration by pressurized gas characterized in that it comprises a saturation crucible (5) arranged in such a way that it is inverted with respect to the infiltration crucible (3) covering it and thus forming a closed saturation chamber (6).

2.

-Device according to claim 1 wherein covering the saturation crucible (5) a thermal insulation hood is provided.

3.

-Device according to the preceding claims in which the material from which the infiltration crucible (3) is made is selected from the following group: commercial steel, graphite, high density ceramic of the type A1203 or Si02.

Four.

-Device according to the preceding claims in which the material of which the saturation crucible is made (5) is selected from the following group: commercial steel, graphite, high density ceramic of the type A1203 or Si02.

5.

-Device according to the preceding claims in which the material of which the thermal insulation hood is made is selected from the following group: high or low density ceramic of type A1203 or Si02, base ceramic A1203 or Si02 of textu

Porous and high machining capacity.

6.

-Device according to the preceding claims wherein the high pressure liquid metals of

7.

-Device according to the preceding claims in which the infiltration crucible (3) is flat based.

8.

-Device according to the preceding claims wherein the saturation crucible (5) is flat or hemispherical base.

9.

-Device according to the preceding claims in which the saturation crucible (5) has a contour preferably adaptable in ± O. 1mm to the infiltration crucible (3).

steam

be select of the next group from metals

cigars

or alloys that the they can contain: Mr, AC, Pb,

Zn,

Mg, Mn Y Cr.

10.-Device use procedure (1) according to any of the preceding claims characterized in that it comprises the following steps:

to.

arrangement of the porous preform (2) inside the infiltration crucible (3), and the infiltrating liquid metal (4) in its upper part above said porous preform

(2) ,

b.

arrangement of the saturation crucible (5) inverted covering the infiltration crucible

(3) with the function of creating a closed saturation chamber (6) to achieve saturation of metallic vapor,

C.

vacuum application to said device (1)

up to a value below 50 mbar, d. increase of the temperature of the device (1) to at least the melting temperature of the metal, 5 e. increase of the internal pressure of the closed saturation chamber (6) of the device (1) by applying pressurized gas to the infiltration machine where the device (1) is installed to force the liquid metal 10 c to infiltrate inside the porous preform (2), F. solidification of the liquid metal. 11.-Procedure according to claim 10 in 15 which between the stages c and d is added another stage consisting in the application of an inert gas in the closed saturation chamber (6) to a pressure lower than the infiltration of the porous medium in order to avoid the subsequent evaporation of the metal by vacuum effect.  1 ~ 3 Fig. 1