WO1990002105A1

WO1990002105A1 - Chemically bonded ceramic materials and use in forming of metals and glass

Info

Publication number: WO1990002105A1
Application number: PCT/US1989/003440
Authority: WO
Inventors: Sean Wise; R. Kevan Jones
Original assignee: Cemcom Corporation
Priority date: 1988-08-16
Filing date: 1989-08-16
Publication date: 1990-03-08

Abstract

High temperature resistant compositions comprise: (1) a high strength chemically bonded ceramic material, and (2) a high strength, high melting aggregate having a moderate hardness; wherein the aggregate is present in a proportion of about 20 to about 50 weight percent of said high temperature resistant composition. The aggregate generally has a melting point of at least about 1500°C, preferably in the range of about 1500 to about 2000°C. The high melting aggregate generally has a Mohs hardness value in the range of about 4 to about 7. The high-strength chemically bonded ceramic when cured preferably has a compressive strength of at least about 80 MPa, and a flexural strength of at least about 20 MPa. The foregoing compositions are useful in the process of superplastic forming parts made of a metallic material at temperatures in the range of up to 1000°C, preferably of 500 to 1000°C. The foregoing compositions are also useful in the process of forming glass parts at temperatures in the range of up to 1000°C, preferably of 500 to 1000°C.

Description

CHEMICALLY BONDED CERAMIC MATERIALS AND

USE IN FORMING OF METALS AND GLASS

Background of the Invention and

Information Disclosure Statement

This is a continuation in part of application Serial No.

07/233,404, filed August 16, 1988.

Field of Invention

This invention is directed to improved high temperature resistant compositions suitable for high temperature metal and glass forming processes.

This invention is also directed to improved metal -forming and glass-forming processes using improved high temperature resistant compositions.

A high temperature metal forming process is known as the superplastic forming (SPF) process. Such a process is accomplished by heating a metallic sheet until it becomes pliable and then forcing the sheet with pressure, usually gas pressure, against a tool, such as a die, until the sheet takes the form of the tool or die. The process produces strong, high-precision, low-cost parts and has become increasingly popular in the production of titanium and aluminum aircraft components.

SPF is now often the method of choice for forming structural parts wherein the forcing process requires the starting raw material to have a high deformation ratio. SPF is used in fabricating parts with close dimensional tolerances. The process is also useful for applications in which it is desirable either to substitute multipiece parts with one integral part or to create substitutes for parts that would otherwise require considerable machining. Thus, the SPF process is considered when the design of the desired part calls for complex, fairly deep shapes with compound curves or when multiplepiece structures must be redesigned to reduce part and fastener counts and to simplify assembly. SPF is generally not practical for the fabrication of simple parts that require little tooling.

A high temperature glass forming process is known as press bending of glass. This is a procedure for producing curved glass sheets which involves heating substantially flat sheets of glass to an elevated temperature at which the glass softens, and thereafter pressing the heat-softened glass sheets between complementary interfitting shaping surfaces formed to the desired shape of the finished sheets. After the sheets are bent or formed in the foregoing manner, the temperature is reduced so that the glass sets, and the sheet retains the shape imparted by the shaping surfaces. Press bending processes are particularly suitable for forming automobile windshields or other large industrial glass applications.

Another process for forming glass products is known as glass sagging. In accordance with this process, a sheet of glass is placed on a mold made of metal or a refractory substance. The glass sheet and mold are heated in an oven, whereupon the glass sheet sags into contact with the mold, thereby conforming precisely to the contours of the mold. The glass sagging process is particularly suitable for forming glass for use in the aerospace industry. The process is also useful for forming glass for industrial applications. Prior Art

Superplastic (SPF) forming processes are generally accomplished where a softened metal sheet is forced by gas pressure over a metal die member. Thus, U.S. Patent 3,934,441 at Column 4, beginning at line 32, states that a primary consideration in selection of a suitable shaping die member alloy is absence of reactivity with the metal to be formed at the forming temperature. When the metal to be formed is titanium or an alloy thereof, iron-based alloys with low nickel content and modest carbon content have been successfully used for the shaping or die member.

Many patents merely refer to "metal" die members without giving attention to the requirements for the metal.

The press bending of glass is described in the prior art as follows:

U.S. Patent 3,298,809 describes the press bending of glass using an apparatus having complementary shaping members which are disposed on the opposite sides of the path of movement for glass sheets. The shaping members have a shaping surface with a glass facing on each of complementary shaping surfaces that regulate the final configuration of the glass sheets. U.S. Patent 3,328,151 describes improvements in press bending molds used for imparting the desired curvature to glass sheets. The invention involves using at least one heat-reflective foil layer and at least one layer of thermally insulating heat-resistant fibrous material. It is preferred that a multiplicity of such layers should be used.

U.S. Patent 3,329,494 is directed to the production of curved sheets of glass and new apparatus for press bending of glass sheets. The apparatus of the patent utilizes shaping molds which appear to be made of metal.

The process known as glass sagging is described briefly in the following textbooks;

How Much Do You Know About Glass by Harland Logan, published by Dod, Mead & Companχ, New York City, (1951); discloses that glass sagging was widely used for curving glass plates as early as 1951.

Glass. Its Industrial Applications by C. J. Phillips, published by Reinhold Publishing Corporation, (1960), at pages 38 and 39;

discloses that in making windshields, two flat sheets of glass are placed in an open metal or refractory ring mold and bent together so they will match precisely when laminated.

Glass Engineering Handbook. Third Edition, 1984 at page 9;

discloses that glass sagging and bending can be performed by laying a glass sheet over a form of metal or refractory material.

Creative Glass Blowing by Hammesfahr & Stong, published by W.H. Freeman and Company, San Francisco (1968) at page 136, discloses that glass sheets are placed over a mold of fireclay, dental stone, plaster of paris or equivalent refractory substance.

It is the purpose of this invention to reduce even further the costs of superplastic forming and glass forming operations based on use of a novel material as the die or tool for the superplastic forming process, and glass forming processes.

A further purpose of the invention is to provide a composition that has improved thermal shock resistance, and which is not reactive with the metal or glass being formed.

A further purpose is to provide a composition that has a coefficient of thermal expansion (CTE) that matches the CTE of the metal being formed especially in the case of titanium.

A further purpose of the invention is to provide a composition that is dimensionally stable, and does not warp when heated and which has low shrinkage at high use temperatures.

Summary of the Invention

The above purposes are accomplished by providing high temperature resistant compositions comprising:

(1) a high-strength chemically bonded ceramic material,

and

(2) a high strength, high melting aggregate having a

moderate hardness;

wherein the aggregate is present in a proportion of about 20 to about 50 weight percent of said high temperature resistant composition.

The aggregate generally has a melting point of at least about 1500ºC, and preferably in the range of about 1500 to about 2000ºC.

The high melting aggregate generally has a Mohs hardness value in the range of about 4 to about 7.

The high-strength chemically bonded ceramic when cured preferably has a compressive strength of at least about 80 MPa, and a flexural strength of at least about 20 MPa.

The foregoing compositions are useful in the process of superplastic forming parts made of a metallic material, which process comprises the steps of:

(1) placing a sheet of metallic material in a press which

contains a tool which is configured to the desired metal part,

(2) heating the sheet of metallic material and the tool, (3) applying pressure such as argon gas pressure to the sheet of metallic material to force the sheet against the tool element that is configured to the desired metal part to form a molded part, and

(4) recovering the molded part from the tool.

The foregoing compositions are also used in glass forming processes such as press bending of glass and glass sagging.

The press bending process involves the steps of

(1) heating a sheet of glass to a sufficient temperature

that the glass is softened,

(2) pressing the softened glass sheets between

complementary, interfitting shaping surfaces formed to the desired shape of the finished sheets, and

(3) cooling the formed glass part with the mold.

The glass sagging process involves the steps of

(1) placing a sheet of glass over a tool which is

configured to the desired part;

(2) heating the sheet of glass and the tool to a

sufficient temperature that the glass is softened and takes the form of the tool, and

(3) cooling the formed glass part and the mold.

Description of the Preferred Embodiments

(1) Tool Materials

(a) Chemically Bonded Ceramics

Chemically bonded ceramics are inorganic oxide materials, for example, metal oxide silicates, aluminates and phosphates. High strength chemically bonded ceramics are such inorganic oxide materials that are blended and processed by special techniques designed to produce high strength and toughness and good thermal shock

characteristics and good stability at use temperatures.

Mostly based on conventional hydraulic cement systems, such as Portland cement and alumina cement, chemically bonded ceramics have mechanical properties which are achieved by processing techniques designed to produce a compact, controlled microstructure, and by use of admixtures which contribute to strength during the hydraulic bonding process. The compact microstructure causes the surfaces of the cured product to be smooth and relatively free of pores. It causes a fine surface. These admixtures may include reactive filler powders, such as pozzolanic silica, as well as small amounts of organic and inorganic polymers.

The present invention utilizes high strength chemically bonded ceramics which in the final cured material exhibit a flexural strength of at least about 20 MPa, but which on the average can be as high as 35 to 70 MPa and higher; and a compressive strength of at least about 80 MPa, but which on the average can be 200 to 300 MPa and higher. A wide variety of cementitious materials can be used to prepare the high strength chemically bonded ceramics used in the high temperature resistant compositions of the present invention. The most important type of cementitious material includes cements such as the following:

1. hydraulic cementitious materials such as:

(a) high alumina cements, and

(b) silica based cements, e.g., Portland cements,

2. other cementitious materials such as cement forming

ceramic compounds, e.g.; metal oxides combinded with silicates, aluminates, phosphates, sulfates,

carbonates, and combinations thereof.

Examples of high strength chemically bonded ceramic matrix materials include those described in the following United States Patents Nos. 4,482,385; 4,501,830 and 4,505,753, the disclosures of which are incorporated herein by reference.

In addition, the high strength chemically bonded ceramic material can include the additives disclosed in the three above-noted U.S.

patents. For example, as described in U.S. Patent No. 4,505,753, the cement is preferably Class H Portland cement, mixed with a crystalline form of silicon dioxide of a general size of finer than 5 microns, silica fume and a superplasticizer. U.S. Patent No. 4,482,385 describes a matrix comprising Class H Portland cement, Min-U-Sil silica particles, silica fume and a superplasticizer. A stainless steel additive is also employed. Suitably chemically bonded ceramic materials are also disclosed in copending applications Serial No. 894,815, filed August 8, 1986, now U.S. Patent No. 4,792,361; and Serial No. 945,632, filed

December 23, 1986, now U.S. Patent No. 4,780,141.

Other suitable and sometimes preferred chemically bonded ceramic materials are disclosed in copending application Serial No. (Case

6137. filed , which is directed to the use of Minex filler instead of the Min-U-Sil filler disclosed in the prior art.

(b) Additive Components: Aggregates and Fibers

A constituent of the chemically bonded ceramic material is a high strength, high melting aggregate which has a moderate degree of hardness. The aggregates generally have a melting point of at least about 1500ºC, preferably about 1500 to 2000ºC. The aggregates should not be so hard that they will render the cured tool too difficult to machine. Accordingly, the high melting aggregates should have a Mohs hardness in the range of about 4 to about 7.

Suitable high melting aggregates include alumino-silicates that are strong and high melting, which are moderately hard so that they are machinable, and which bond well to the chemically bonded ceramics. Suitable such aggregates include mullite and kyanite. Kyanite is a mineral in the condition mined from the earth. One type of mullite is a calcined form of kyanite.

The high melting aggregates generally have a particle size of at least about 200 microns, and preferably in the range of about 300 to about 700 microns. The high melting aggregates are employed in a proportion of about

20 to about 50 weight percent of the high temperature resistant composition of the invention, preferably about 25 to about 40 weight percent.

The high temperature resistant compositions of the invention, also may comprise fiber components. Preferred for enhancement of strenth and toughness are metal fibers which generally have an average length of about 0.5 to about 5 millimeters, preferably 2-3

millimeters, an average width or cross-section of about 10 to 250 microns, preferably about 50 to 150 microns. These are average dimensions. The fibers have a broad distribution of length and widths or cross-sections, such that up to about 20 percent of the fibers can be outside the above-mentioned ranges. Generally, the fiber lengths do not exceed about 20 millimeters and the widths are cross-sections of not more than about 300 microns.

The fibers can be made of stainless steel, but other metals such as low carbon steel, tungsten and copper can be used. Mixtures of such fibers can be used. The fibers can be razor-cut from a metal wire and chopped. The metal fibers can be produced as "steel wool" and chopped to the desired size. The chopped steel wool is

commercially available in short lengths (1 to about 15 millimeters) can be used.

Polymeric fibers can also be incorporated into the compositions of the invention. Organic fibers, such as nylon, polyesters and fibers with low ignition temperatures are useful. The organic fibers tend to burn at the elevated temperatures employed in the practice of the invention. This results in the formation of escape routes for the moisture in the composition.

The fiber component is generally employed in a proportion of about 0 to about 30 weight percent based on the weight of the high temperature resistant composition of the invention, usually about 5 to about 20 weight percent, preferably about 5 to less than 20 weight percent, depending on the use of temperature of the composition.

(2) Processing of the Chemically Bonded Ceramic Materials

The components of the high temperature resistant, chemically bonded ceramic compositions of the invention are mixed in a cool, moist environment. A planetary mixer is suitable for use in mixing the components of the composition.

The resulting mixture is used for casting of the composition into the form of the desired tool. The compositions of the invention are cast using vibration to facilitate flow. When the pattern is nearly full, the composition is leveled off.

Curing involves developing an inorganic network through the use of hydrothermal hydration reactions, followed by dehydration of the network using a high temperature oven.The compositions of the invention are partially cured in a mold in a warm moist environment for an extended period such as a day or two. In one curing procedure, the molded tool is wrapped in a sealed nylon container which seals in the moisture and provides a moist environment to enhance curing. In another curing method, the molded tool is subjected to a high pressure, high temperature moist environment to enhance hydration. Following hydration, the tool is dried at a temperature that is slightly above the intended use temperature.

(3) Superplastic Forming Metals

A variety of metallic materials can be subjected to the superplastic forming process. Most of these metallic materials are based on titanium and aluminum and their respective alloys. Several such metal materials are disclosed in the article entitled "Superplastic Forming-An Elegant Solution" by Catherine A. Behringer, published by

Manufacturing Engineering, January 1987, the disclosure of which is incorporated herein by reference.

(4) The Superplastic Forming Process

Superplasticity is the capability of a material to develop unusually high tensile elongations with reduced tendency toward necking, a capability exhibited by only a few metals and alloys and within a limited temperature and strain rate range.

The superplastic forming (SPF) process of the invention involves the insertion of a sheet or sheets of a metallic material that is capable of exhibiting superplasticity into a heated press, containing a forming die or dies. These dies are also often referred to as tools. The press, including the die(s) and metallic sheet(s), is heated to the superplastic forming temperature of the metallic material being formed. The metallic sheet is then formed to the configuration of the die or tool by the use of controlled gas pressure. After the part is fully formed, the press and contents are cooled somewhat to harden the metallic part, and the finished piece is removed.

Thus the superplastic forming process for forming metals comprises the steps of

(1) placing a sheet of metallic material in a press which

contains a tool which is configured to the desired metal part,

(4) recovering the molded part from the tool.

The chemically bonded ceramic compositions of the invention designed for use in super-plastic forming of titanium and its alloys have, when cured, a CTE which approximates the CTE of the titanium based metallic material. This has the effect of allowing the tool and formed metallic part to be cooled to facilitate removal of the part without causing excessive stress in the part due to differences in thermal expansion.

The mechanical properties of the chemically bonded ceramic products intended for use at temperatures below 1200ºF are superior to the chemically bonded ceramic products made for use at 1800ºF.

The chemically bonded ceramic material used in the forming of aluminum has the same beneficial characteristics of chemically bonded ceramic material used for forming titanium. However, the similarities in CTE between aluminum and chemically bonded ceramic is not as significant as the similarities in CTE between the chemically bonded ceramic and titanium. This is because aluminum is softer and is formed at a much lower forming temperature than titanium.

(5) The Glass Component

A variety of glass sheets can be employed in the process of the invention. (6) The Glass-Forming Processes

The glass sheets can be formed into the desired shape by the processes known as the press bending of glass and glass sagging.

(A) The press bending process involves the steps of

(1) heating a sheet of glass to a sufficient temperature that the glass is softened,

(2) pressing the softened glass sheets between

(3) cooling the formed glass part.

The glass is heated to a temperature in the range of about 1000 to 1500ºF, preferably about 1200ºF. The surface of the tool is heated to a temperature of about 600 to 800ºF. The glass sheets are rapidly cooled and set to the desired shape by the cooling effect of the tool. Thus, the process is generally not used for complex shapes that require slower cooling. The CTE is not critical because of the temperature differentials involved between tool and glass, and the fact that the tool is held at constant temperature.

(B) The glass sagging process involves the steps of

(1) placing a sheet of glass over a tool which is configured to the desired part;

(2) heating the sheet of glass and the tool to a sufficient temperature that the glass is softened and takes the form of the tool, and

(3) cooling the formed glass part. The glass sagging process is characterized by the tool and glass being heated and cooled together. It is helpful for the glass and tool to have similar coefficients of thermal expansion (CTE). The use of thin shell tools facilitates uniform transfer of heat between the tool and the glass.

In the foregoing glass-forming processes, the glass is generally heated to its softening temperature in the range of about 1100 to about 1400 degrees Fahrenheit (593 to 760 degrees Celsius).

Advantages of the Invention

The chemically bonded ceramic compositions of the invention, when cured, provide tools and dies which exhibit improved thermal shock resistance when compared to ordinary cements and concretes. In fact, ordinary cements and concretes do not exhibit the thermal stability to be used at superplastic forming and glass forming temperatures. The compositions of the invention may, therefore, be repeatedly heated and cooled, as required by the superplastic forming process or the glass forming processes, without risk of mechanical failure due to thermal stresses.

The heat transfer characteristics of the chemically bonded ceramic compositions of the inventions have advantages, from some respects, over both the commercial product known as "THERMOSIL" and steel. The specific nature of these advantages is dependent on the nature of the process parameters under which the chemically bonded ceramic is to be used. Specifically, the high bending strength of the chemically bonded ceramic allows design of very thin structures which transfer heat quickly. This is advantageous in the glass sagging process, where continuous heating of the tool and part occurs, and heat must be transferred evenly to the glass part. However, in the press bending process, it is advantageous for the thermal transfer to be low, as in the case of a more massive chemically bonded ceramic tool, so that rapid cooling of the glass part does not occur while bending is taking piace.

The compositions of the invention have good strength at the high operating temperatures used in forming metals and glass. They have good surface finishes and can be used repeatedly in the forming of glass and metals.

The chemically bonded ceramics of the invention have the characteristics of ease of forming the tool as contrasted to the difficulty in forming of metal tools.

The cured chemically bonded ceramic compositions of the invention do not react with the metal subjected to the superplastic forming processes, or the glass used in the glass forming processes.

The cured chemically bonded ceramic compositions of the invention have good mechanical properties. They are dimensionally stable and do not warp when heated. They exhibit low shrinkage at high use temperatures. The tools have a very good finish. They do not require re-working as often as tools made of conventional materials. EXAMPLES

In the following examples and throughout the specification and claims, parts are by weight and temperatures are in degrees Celcius unless indicated otherwise.

Composition Example A

The following components were blended in the proportions shown.

Ingredient Wt % Vol %

Aggregate

-35 mesh Kyanite 32.75 27.00

Fibers

434 Stainless Steel Fiber 17.08 6.50

Binder

Class H Cement 26.11 24.60

Min-U-Sil 12.65 14.17

Silica Fume 3.55 5.02

M-100 Superplasticizer 0.55 1.02

Water 7.31 21.69

Composition Example B

The following components were blended in the proportions shown.

Ingredient Wt % Vol %

Aggregate

-35 mesh Mullite 25.87 24.00

Fibers

434 Stainless Steel Fiber 18.22 6.50

Binder

Class H Cement 29.10 25.71

Min-U-Sil 14.10 14.81

Silica Fume 3.96 5.25

M-100 Superplasticizer 0.62 1.07

Water 8.14 22.67

Example 1

The components of composition A were mixed according to

procedures specified in ASTM test C305, Section 7. Samples of the resultant material were cast using high speed vibration to facilitate flow. Some hand working of the surface of the material was required to ensure a level finish.

The resulting specimens were cured in the mold for 24 hours in a warm (24ºC to 32ºC), moist (100% relative humidity) environment.

After demolding, the samples were cured for a further 24 hours in a saturated lime solution at 60ºC. A minimum of 4 days air drying followed the lime treatment, and after the air dry, an oven was used to fully dry the material. In this oven, the material was slowly heated from room temperature to 25ºC above its use temperature, held at this temperature for 24 hours, then cooled back to room

temperature.

Example 2

Composition B was treated in accordance with the procedure used in Example 1.

The tools produced in Examples 1 and 2 were tested for various physical properties and compared with the properties of three commercial materials shown in Table 1.

In comparing the results shown in Table 1, care must be taken to compare materials having similar cure temperature. Thus, in comparing composition A of the invention with COMTEK^® 66 tooling material and the liquid silicate rebonded fused silica, it is seen that composition A of the invention has distinct advantages over the other materials. With respect to use in superplastic forming applications, important properties are the compressive strength, flexural strength and the shrinkage on curing. It is seen that composition A of the invention has higher strengths, generally, which makes it more resistant to mechanical failure. Moreover, composition A of the invention exhibits better dimensional stability characteristics than the other two materials because of its lower shrinkage.

Comparing composition B with aluminate rebonded fused silica shows the same strength advantages demonstrated for composition A over its competitors. Thus, the shrinkage displayed by composition B was at least as low as that of the aluminate bonded fused silica. Also, the coefficient of thermal expansion of composition B is much more closely matched to the metal being formed on it. This means that cool down of the mold and part could be achieved without risk of causing stresses in parts.

A further advantage of both composition A and B is their resistance to warp at high temperatures.

A composition of the invention similar to Composition A was cured to form novel tools of the invention. When these tools were used in the superplastic forming of aluminum sheets, aluminum parts were formed.

A composition of the invention similar to Composition B was cured to form the novel tools of the invention. When these tools were used in the superplastic forming of titanium sheets, titanium parts were formed.

TABLE 1

Liquid

Silicate Aluminate

Composition Composition COMTEK Rebonded Rebonded A B _ 66_ Fused Silica Fused Silica

Cure Temperature (ºF) 1000 1800 1000 1000 1850

Compressive Strength (kpsi) 38.5 13.0 45.0 4.0 5.0*

Flexural Strength (kpsi) 6.2 4.0 4.0 1.2 Not Reported

Flexural Modulus (Mpsi) 3.0 3.0 1.5 <3.0 Not Reported

Shrinkage (Percent) 0.307 0.382 0.540 1.200 <0.200^§

Coefficient of Thermal 4.5 4.5 7.7 4.5 0.4 Expansion (X 10^-6/ºF)

* At 250ºF

§ Users of Aluminate Rebonded Fused Silica have reported shrinkages of 0.60%.

Examples 3 to 8

The procedures of Examples 1 and 2 were substantially repeated using the Compositions C through H, respectively, shown in Table 2. The cured materials produced from Compositions C through H were tested for various physical properties which are shown in Table 3.

Tools made from Compositions C, D, G and H are used in the superplasticforming of aluminum sheets. Excellent, reproducable aluminum parts are obtained.

Tools made from Compositions D, G and H are used in the

superplasticforming of titanium sheets. Excellent, reproducable titanium parts are obtained.

TABLE 2

Composition C D E F G H

Wt. % Vol. % Wt. % Vol. % Wt. % Vol. % Wt. % Vol. % Wt. % Vol. % Wt. % Vol. %

Aggregates

-28 mesh Kyanite - - - - 52.77 41.00 - - - - - - -35 mesh Kyanite 32.75 27.00 - - - - - - - - - - -35 mesh Mullite - - 25.87 24.00 - - 40.84 34.00 36.23 31.00 31.63 28.00

Fibers

434 Stainless Steel 17.08 6.50 18.22 6.50 - - - - 6.08 2.00 11.75 4.00

Matrix

Class H Cement 26.11 24.60 29.10 25.71 24.58 21.82 30.79 24.41 29.71 24.22 29.16 24.58

Min-U-Sil 12.65 14.17 14.10 14.81 11.91 12.57 14.92 14.06 14.40 13.95 14.13 14.16

Silica Fume 3.55 5.02 3.96 5.25 3.34 4.45 4.19 4.98 4.04 4.94 3.96 5 .01

Mighty 100 0.55 1.02 0.62 1.07 0.52 0.91 0.65 1.02 0.63 1.01 0.62 1.03 Superplasticizer

Water 7.31 21.69 8.14 22.67 6.88 19.25 8.62 21.53 8.91 22.88 8.75 23.23

TABLE 3

Composition C D E F G _ H

Cure Temperature, °C 538 954 427 816 538 538

Flexural Strength (MPa) 36.5 33.1 32.4 22.8 27.6 37.2

Flexural Modulus (GPa) 19.3 27.6 32.4 22.8 16.5 18.6

Compressive Strength (MPa) 317 96 207 90 262 290

Shrinkage (Percent) 0.412 0.092* 0. 167 0.344 0.344 0.398

*Some expansion seen due to oxidation.

Example 9

One of the major parameters measured, when evaluating a potential tooling or die material for use in SPF of titanium and its alloys, is the occurence of alpha case on the formed metallic parts. Alpha case is a transformation of the crystal structure of the alloy being formed, and may be catalyzed by surface oxidation of the tool or die. It is characterized by determining the depth to which it has

penetrated the formed part. Alpha case contamination from

conventional steel tooling occurs in depths ranging up to 0.0030 inch. Composition B has been used to form parts of titanium that exhibit alpha case contamination of depths of only half that shown for conventional steel. Thus, the products of the invention showed an improvement over conventional tooling materials.

Composition Example J

The following components were blended in the proportions shown.

Ingredient Wt % Vol %

Aggregate

-35 mesh Mullite 29.20 25.00

Fibers

434 Stainless Steel Fiber 9.11 3.00

1/8" Chopped Nylon Fiber 0.11 0.25

Binder

Portland Class H

Cement 31.76 25.90

Minex 10 15.39 15.15

Silica Fume 4.32 5.28

M-100 Superplasticizer 0.59 0.95

Water 9.53 24.48 Examples 10 to 12

The components of Composition J were mixed according to procedures specified in ASTM test C305, Section 7. Samples of the resultant material were cast using high speed vibration to facilitate flow. Some hand working of the surface of the material was required to ensure a level finish.

After demolding, the samples were placed in a nylon bag and placed in an oven. In this oven, the material was slowly heated from room temperature to 25ºC above its use temperature. This cure temperature was held for 24 hours. The meterial was then cooled to room temperature.

The cured materials produced from Composition J were tested for various physical properties which are shown in Table 4.

Table 4

Properties of Composition J Cured at Various Temperatures

Example No. 10 11 12

Compressive Strength (MPa) 83 210 207

Flexural Strength (MPa) 21 35 28

Modulus of Elasticity (GPa) 16 24 20

Hardness (Mohs) 4-5 4-5 4-5

Density (g/cc) 2.6 2.6 2.6

Coefficient of Thermal Expansion 8.1x10^-6/°C 8.1x10^-6/°C 8.1x10^-6/°C

Thermal Conductivity (mK) -- 2.06 2.06

Specific Heat (kJ/kgK) -- 0.879 Approx. 0.879

Cure Temperature (°C) 980 540 625

Shrinkage at Cure Temperature, Percent 0.3 0.44 0.47

Intended Use Titanium Aluminum Glass Forming

Forming Forming

Composition J is cured to form novel tools of the invention. When these tools are used in the superplastic forming of aluminum sheets, reproducable aluminum parts are formed.

Composition J is cured to form the novel tools of the invention. When these tools are used in the superplastic forming of titanium sheets, reproducable titanium parts are formed.

Composition J is cured to form the novel tools of the invention. When these tools are used in the forming of glass sheets, reproducable glass parts are formed.

Claims

WE CLAIM: - 1 - A high temperature resistant composition comprising: (1) a high strength chemically bonded ceramic material, and (2) a high strength, high melting aggregate having a Mohs hardness value in the range of about 4 to about 7; wherein the aggregate is present in a proportion of about 20 to about 50 weight percent of said composition. - 2 -The composition of Claim 1 wherein the high strength chemically bonded ceramic when cured has a compressive strength of at least about 80 MPa and a flexural strength of at least about 20 MPa. - 3 -The composition of Claim 1 wherein the aggregate has a melting point of at least about 1500 degrees Celsius. - 4 - The composition of Claim 1 wherein the aggregate has a melting point in the range of about 1500 to about 2000 degrees Celsius. - 5 -The composition of Claim 1 wherein the aggregate is mullite. - 6 -The composition of Claim 1 wherein the aggregate is kyanite. - 7 - A high temperature resistant composition comprising: (1) a high strength chemically bonded ceramic material which when cured has a compressive strength of at least about 80 MPa and a flexural strength of at least about 20 MPa, and (2) a high strength, high melting aggregate having a melting point in the range of about 1500 to about 2000ºC and a Mohs hardness value in the range of about 4 to about 7; wherein the aggregate is present in a proportion of about 20 to about 50 weight percent of said composition. - 8 -The composition of Claim 7 wherein the aggregate is mullite, kyanite, or a mixture thereof. - 9 -The composition of Claim 1 when cured to a shaped article. - 10 -The composition of Claim 7 when cured in the form of a tool. - 11 -The composition of Claim 8 when cured in the form of a tool. - 12 - In the process for superplastic forming of parts made of metallic material which comprises the steps of: (1) placing a sheet of said metallic material in a press which contains a tool which is configured to the desired part; (2) heating the sheet of metallic material and the tool, (3) applying pressure to the sheet of metallic material to force the metallic material into the cavity formed by the metallic material and the tool that is configured to the desired part, and (4) recovering the formed part from the tool; the improvement wherein the tool is comprised of the cured composition of components comprising (a) a high strength, chemically bonded ceramic material, and (b) a high strength, high melting aggregate having a Mohs hardness value in the range of about 4 to about 7; wherein the aggregate is present in a proportion of about 20 to about 50 weight percent of said composition. - 13 -The process of Claim 12 wherein the high strength chemically bonded ceramic when cured has a compressive strength of at least about 80 MPa and a flexural strength of at least about 20 MPa. - 14 -The process of Claim 12 wherein the aggregate has a melting point of at least about 1500 degrees Celsius. - 15 -The process of Claim 12 wherein the aggregate has a melting point in the range of about 1500 to about 2000 degrees Celsius. - 16 - In the process for superplastic forming of parts made of metallic material which comprises the steps of:

(1) placing a sheet of said metallic material in a press which contains a tool which is configured to the desired part;

(2) heating the sheet of metallic material and the tool,

(3) applying pressure to the sheet of metallic material to force the metallic material into the cavity formed by the metallic material and the tool that is configured to the desired part, and

(4) recovering the formed part from the tool; the improvement wherein the tool is comprised of the cured composition of components comprising

(a) a high strength chemically bonded ceramic material which when cured has a compressive strength of at least about 80 MPa and a flexural strength of at least about 20 MPa, and (b) a high strength, high melting aggregate having a melting point in the range of about 1500 to about 2000ºC and a Mohs hardness value in the range of about 4 to about 7; wherein the aggregate is present in a proportion of about 20 to about 50 weight percent of said composition.

- 17 -

The process of Claim 12 wherein the aggregate is kyanite or mullite.

- 18 -

A molded article produced in accordance with the process of Claim 12.

- 19 -

A molded article produced in accordance with the process of Claim 13.

- 20 -

A molded article produced in accordance with the process of Claim 14.

- 21 -

A molded article produced in accordance with the process of Claim 15.

- 22 -

A molded article produced in accordance with the process of Claim 16.

- 23 -

A molded article produced in accordance with the process of Claim 17.

- 24 -

The molded article of Claim 18 wherein the metallic material is titanium or aluminum.

- 25 -

The molded article of Claim 22 wherein the metallic material is titanium. - 26 -

The molded article of Claim 23 wherein the metallic material is aluminum.

- 27 - In the process for forming glass parts which comprises the steps of:

(I) heating a sheet of glass to a sufficient temperature that the glass is softened,

(2) pressing the softened glass sheets between

(3) cooling the formed glass part;

the improvement wherein the tool is comprised of the cured composition of components comprising

(a) a high strength, chemically bonded ceramic material, and (b) a high strength, high melting aggregate having a Mohs

hardness value in the range of about 4 to about 7; wherein the aggregate is present in a proportion of about 20 to about 50 weight percent of said composition.

- 28 -

The process of Claim 27 wherein the high strength chemically bonded ceramic when cured has a compressive strength of at least about 80 MPa and a flexural strength of at least about 20 MPa. - 29 -

The process of Claim 27 wherein the aggregate has a melting point of at least about 1500 degrees Celsius.

- 30 -

The process of Claim 27 wherein the aggregate has a melting point in the range of about 1500 to about 2000 degrees Celsius.

- 31 -

The process of Claim 27 wherein the aggregate is mullite.

- 32 -

The process of Claim 27 wherein the aggregate is kyanite.

- 33 - In the process for forming glass parts which comprises the steps of:

(2) pressing the softened glass sheets between

(3) cooling the formed glass part;

the improvement wherein the tool is comprised of the cured composition of components comprising (a) a high strength chemically bonded ceramic material which when cured has a compressive strength of at least about 80 MPa and a flexural strength of at least about 20 MPa, and (b) a high strength, high melting aggregate having a melting point in the range of about 1500 to about 2000ºC and a Mohs hardness value in the range of about 4 to about 7; wherein the aggregate is present in a proportion of about 20 to about 50 weight percent of said composition.

- 34 -

The process of Claim 33 wherein the aggregate is mullite, kyanite, or a mixture thereof.

- 35 - In the process for forming glass parts which comprises the steps of:

(2) heating the sheet of glass and the tool to a sufficient

temperature that the glass is softened and takes the form of the tool, and

(3) cooling the formed glass part;

(a) a high strength, chemically bonded ceramic material, and (b) a high strength, high melting aggregate having a Mohs hardness value in the range of about 4 to about 7; wherein the aggregate is present in a proportion of about 20 to about 50 weight percent of said composition.

- 36 -

The process of Claim 35 wherein the high strength chemically bonded ceramic when cured has a compressive strength of at least about 80 MPa and a flexural strength of at least about 20 MPa.

- 37 -

The process of Claim 35 wherein the aggregate has a melting point of at least about 1500 degrees Celsius.

- 38 -

The process of Claim 35 wherein the aggregate has a melting point in the range of about 1500 to about 2000 degrees Celsius.

- 39 -

The process of Claim 35 wherein the aggregate is mullite.

- 40 -

The process of Claim 35 wherein the aggregate is kyanite. - 41 - In the process for forming glass parts which comprises the steps of:

(2) heating the sheet of glass and the tool to a sufficient

temperature that the glass is softened and takes the form of the tool, and

(3) cooling the formed glass part;

- 42 -

The process of Claim 41 wherein the aggregate is mullite, kyanite, or a mixture hhereof. - 43 -

A molded article produced in accordance with the process of Claim 27.

- 44 -

A molded article produced in accordance with the process of Claim 31.

- 45 -

A molded article produced in accordance with the process of Claim 32.

- 46 -

A molded article produced in accordance with the process of Claim 33.

- 47 -

A molded article produced in accordance with the process of Claim 34.

- 48 -

A molded article produced in accordance with the process of Claim 27.

- 49 -

A molded article produced in accordance with the process of Claim 31.

- 50 -

A molded article produced in accordance with the process of Claim 32.

- 51 -

A molded article produced in accordance with the process of Claim 41.

- 52 -

A molded article produced in accordance with the process of Claim 42.