US3533271A - Metal dies - Google Patents

Metal dies Download PDF

Info

Publication number
US3533271A
US3533271A US657720A US3533271DA US3533271A US 3533271 A US3533271 A US 3533271A US 657720 A US657720 A US 657720A US 3533271D A US3533271D A US 3533271DA US 3533271 A US3533271 A US 3533271A
Authority
US
United States
Prior art keywords
die
matrix
deposited
temperature
strength
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US657720A
Inventor
George J Walkey
Frank N Adgate
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Lockheed Corp
Original Assignee
Lockheed Aircraft Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lockheed Aircraft Corp filed Critical Lockheed Aircraft Corp
Application granted granted Critical
Publication of US3533271A publication Critical patent/US3533271A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21DWORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D37/00Tools as parts of machines covered by this subclass
    • B21D37/20Making tools by operations not covered by a single other subclass

Definitions

  • a die and the method of fabricating it utilizing the technique of thermal spraying A matrix of predetermined strength is initially cast over a pattern to a desired thickness. After the matrix hardens it is separated from the pattern, heated, and a metal or other die material sprayed over its formed surface. The combination is then cured and allowed to cool, causing the matrix, but not the die, to crack and facilitating easy separation.
  • the resulting die shell may then be filled with a mixture of reinforcing material and binder and heated, causing the binder to liquefy. Upon cooling the binder solidifies around the reinforcing material, giving great structural integrity to the die shell and producing a tough, high temperature die.
  • the Shaw process uses a conventional casting technique with a special sand matrix manufactured from Bakelite and resin. While close tolerances are obtainable by this process it is economically unsatisfactory in high temperature applications with hard materials.
  • the Keller method is a pantographic-like process and initially entails the making of the finished article as a master. A machine is then slaved, by conventional means such as a stylus bearing against the outer surface of the master, to produce the desired copies. While this method may be utilized for hard materials, it is very slow, comparatively expensive and completely unsuited for tracing complex shapes.
  • the resulting metal shell or die is filled with a selected mixture of reinforcing material and binder and heated, causing the binder to liquefy. As the mixture cools, the binder hardens and adheres the reinforcing material to the die shell.
  • FIG. 1 is a perspective view of a heated die configuration manufactured in accordance with the invention
  • FIG. 2 is a longitudinal section through a mold pattern after the substrate or matrix has been deposited thereon;
  • FIG. 3 is the matrix of FIG. 2 after it has been removed from the mold pattern and a layer of die material deposited thereon;
  • FIG. 4 is similar to FIG. 1 and illustrates the die material separated from the matrix with a mixture of reinforcing material and binder in reinforcing relationship therewith;
  • FIG. 5 illustrates an alternate embodiment of the matrix with a layer of die material deposited thereon
  • FIG. 6 is the die material layer of FIG. 5 separated from the matrix with a binder deposited thereon;
  • FIG. 7 is the die of FIG. 6 with additional layers of die material deposited thereon, and
  • FIG. 8 is an enlargement of the mixture of reinforcing material and binder of FIG. 4.
  • FIGS. 14 and 8 there is depicted a mold 10 having a surface 12. dimensionally contoured to a desired configuration and smoothness.
  • mold 10 may be fabricated from an inexpensive material such as plastic, plaster or wood. This economy is possible since the mold 10 and the surface 12 are not subject to deterioration as a result of subsequent spraying steps.
  • the surface 12 is first coated with a parting agent to provide a parting coating 14.
  • the function of the coating 14 is to facilitate removal of the molded refractory skeleton from the mold 10.
  • the parting agent may be applied in any suitable fashion such as by spraying or pouring. Although several layers of wax material will faciiltate the separation of the skeleton from the mold sprayed Teflon, molybdenum disulfide or lacquer may also be used as the parting agent.
  • an inorganic matrix or substrate is deposited thereover and over the coated surface 12 by conventional means such as spraying, ladling or the like.
  • the inorganic matrix 15 is fabricated from an aluminide or beryllide such as aluminum oxide or beryllium oxide or from a cement.
  • the matrix 15 is of such a strength, thickness and substance that it is compatible with die material 16 to be sprayed thereon at a subsequent time. It is of primary importance that the substance used for the matrix 15 be of a strength sufiicient to withstand the heat during the preheating procedures and the internal pressures of handling which are produced during the process. For high temperature applications and the ability to withstand internal stresses, a high strength cement has been found to be generally superior to plaster of paris or dental plaster. (38) Holfmaster-43965 Elec.
  • the resulting strength of the deposited matrix 15 is a critical consideration since the matrix 15 must have a compressive strength which is less than the yield strength of the die material 16 which is subsequently deposited thereon. Were it otherwise, die 17 would crack during the cooling process. After a predetermined thickness is reached, the matrix 15 is oven or air cured, depending upon the type of die 17 to be fabricated and the die material to be used.
  • the matrix 15 After the matrix 15 cools, it is separated from the mold 10, such removal being facilitated by cracking of mold 10 which usually occurs during the cooling cycle. If the mold 10 does not crack, it may be removed from matrix 15 by use of conventional means (e.g., hammer and chisel). Upon being removed, the matrix 15 is ready to be preheated to a temperature compatible with the die material 16 to be subsequently deposited thereon.
  • the die material 16 itself is usually a metal or metal alloy but may comprise other types of inorganic materials such as plastic, cement or plaster. Thus, while a metallic material is referred to hereinafter, it is to be noted that this is for illustrative purposes only.
  • an organic which, upon being heated, becomes an inorganic e.g. calcium lactate into calcium oxide
  • the preheat temperature be approximately that which results in a 50% yield strength of the sprayed metal. While some latitude may be taken with regard to this temperature, the above has been found to be generally satisfactory. In handling aluminum materials, for example, a requirement exists that the temperature of the preheated matrix 15 be approximately 800 F., while in handling steel or steel alloys the heating requirement is approximately l500 F.
  • the die material 16 is sprayed on the matrix 15 to form a die 17 of predetermined yield strength, and of thickness compatible with the compressive strength of the matrix 15.
  • the preheat temperature is maintained by conventional and suitable means such as a gas burner or oxyactylene flame (not shown) until such time as the desired thickness of the sprayed metal is achieved.
  • the matrix 15 must be sufficiently thin that its compressive strength is less than the yield strength of the die 17.
  • the matrix surface 18 need not be coated with a parting agent as taught by the prior art of metal spraying since the matrix 15 will resist spalling on die surface 19 without the requirement of a coating therebetween because of the preheating of the matrix 15 and the preselected strength of the materials used.
  • the combination is placed in a preheated oven (not shown) and allowed to slowly cool for a length of time precalculated to result in failure of the matrix 15.
  • the temperature of the preheated oven should be approximately that to which the matrix 15 was heated prior to the deposition of die material.
  • the die 17 can, by the aforementioned procedure, be produced to any thickness desired, but because of its shell-like configuration would be somewhat limited in strength and thus substantially unsuited for high temperature forming of high strength materials but could, however, be utilized for forming lower strength materials such as plastic and thin aluminum sheet.
  • the materials used for the die 17 and the matrix 15 may be chosen of materials having nearly identical thermal coefiicients of expansion thereby contracting at almost the same rate. While under these circumstances neither material will crack during the cooling period, this procedure is generally very costly and is therefore economically unsatisfactory over the method previously discussed.
  • the matrix 15 is separated from the die 17 and excess overspray, if any, is removed by conventional means such as by sawing, grinding, or the like, until the desired finished dimensions are obtained. Since the finished dimensions are unaffected by excess overspray, it is not mandatory that it be removed. However, it has been found beneficial in that a more compact, easier handling and lighter weight die can be achieved if the additional material is removed.
  • a mixture of binder material 22 (FIG. 4) and reinforcing material 24 (the combination being sometimes referred to as reinforcing mixture) such as epoxy resin and metal shot, respectively, are deposited by pouring, ladling or the like, within a cavity formed in the die 17 opposite its surface 19.
  • the ingredients of the reinforcing mixture are carefully chosen to provide the desired strength of the finished die 17 and in view of temperatures involved in forming the material of the ultimate product for which the die of this invention is provided.
  • the combination is oven heated to a temperature sufficient to liquefy the binder material 22 which, upon cooling, adheres the reinforcing material 24 to the die 17, thereby forming one continuous, solid, die mass.
  • a heating member may be located within the die 17 and surrounded by the reinforcing mixture.
  • the heating member 20 may be of any conventional means such as a high resistance wire or heating rod electrically connected to a heating source 26 by wires 28 and 30 as best illustrated in FIG. 4.
  • the usage of a heating member 20 located within the die serves the dual purpose of heating the reinforcing mixture, thereby eliminating the requirement for oven heating and also permits the finished die to be integrally heated for the purpose of hot forming materials such as titanium.
  • the temperature to which the reinforcing mixture is heated should approximate that to which the matrix 15 and die 17 were previously preheated.
  • the binder material 22 is selected such that it will liquefy at or near the preheat temperature and when cooled cause the reinforcing material 24 to adhere to the interior portion of the die surface 19.
  • a modified embodiment of the present invention is depicted wherein a matrix 15 having a surface 18 of dimensionally contoured shape and smoothness has a die material 16 deposited thereon.
  • the matrix .15 in the modified embodiment may be of standard composition and for this purpose plaster of paris has been found to be generally satisfactory.
  • the die material 16 sprayed upon the contoured surface 18 need not be heated in the modified embodiment since it has been found that preheat is required only when a thick coating of die material 16 is deposited. In this regard coatings of inch and under do not require the die material to be heated since the internal stress determines the necessity for preheat and is a function of thickness.
  • a fiber glass binder 22 is deposited over the die material 16 to a thickness of approximately /2 inch.
  • copper reinforcing material 24 is deposited on the binder 22 at room temperature to a thickness of inch.
  • an additional layer of epoxy impregnated fiber glass binder 22 is deposited over the copper layer.
  • EXAMPLE 1 A wooden mold 10 of the character illustrated in FIG. 2 and having a desired dimensionally contoured surface 12 was coated with a .005 inch layer of paste wax to form a parting coating 14 over its surface 12.
  • An inorganic matrix 15 of high strength cement was thereafter deposited at room temperature upon the waxed surface 12 until the matrix 15 was /2 inch thick.
  • the matrix 15 was deposited by spraying it over the surface 12 and was precalculated to be of a thinness sufficient to crack during the subsequent cooling steps.
  • the matrix 15 was then oven cured at a temperature of 350 F. for two hours and the mold 10 separated therefrom after it had cooled to room temperature.
  • the matrix 15 was next preheated to 1500 F. and S.A.E.
  • EXAMPLE 2 A Wooden mold 10 having a desired dimensionally contoured surface 12 was coated with molybdenum disulfide to form a parting coating 14 of .004 inch thickness. An inorganic matrix 15 of beryllium oxide was then deposited upon the coating 14 to a thickness of A inch, air cured at a temperature of 350 F. and then allowed to cool for 24 hours to room temperature. Upon cooling, the matrix 15 separated from the mold 10 and was then preheated to 800 F. Aluminum was thereafter sprayed on the matrix 15 while the matrix 15 was maintained at 800 F. by a gas burner.
  • a metal die shell of a 17 /2 inch thickness in length was formed and the combination thereafter placed in an oven preheated to 800 F., the oven then being turned off and the die allowed to cool for four hours.
  • the matrix 15 was found to be cracked.
  • the die surface 19 was cleaned by grit blasting with 40 mesh iron grit at 80 p.s.i.
  • a mixture of 5% epoxy resin binder material 22 and chopped fiber glass reinforcing material 24 was then deposited within the die 17 opposite the die surface 19.
  • the combination was then oven cured at a temperature of 150 F. and subsequently allowed to air cool for a period of 24 hours.
  • the die was found suitable for cold forming low strength metals.
  • EXAMPLE 3 A plastic mold 10 having a predetermined contoured surface 12 was coated with molybdenum disulfide to a thickness of .002 inch to form a parting coating 14 over its surface 12. A plaster of paris matrix 15 was then deposited, at room temperature, over the parting coating 14. The matrix 15 was then oven cured at a temperature of 350 F. for four hours and thereafter removed from the mold 10. Aluminum was next sprayed over the matrix 15 to a thickness of inch. The matrix 15 and the aluminum were not preheated during this step since the resultant internal stresses determine the preheating requirement and are a function of the thickness of the material. Epoxy impregnated fiber glass was then deposited over the aluminum at room temperature to a thickness of /2 inch.
  • the combination was then air cured for three and one-half hours at room temperature. Upon reaching room temperature a 4; inch layer of copper was deposited at room temperature on the fiber glass.
  • the die 17 was then filled with epoxy impregnated fiber glass reinforcing material 24 and air cured for 3 /2 hours. The die was found to be suitable for filament winding and forming aluminum of thickness of .060 inch or less.
  • EXAMPLE 4 A plastic mold 10 was coated with lacquer to form a parting coating 14 of a thickness of .003 inch. Dental plaster was then deposited on the coating 14 to a thickness of A inch and the combination oven cured at 225 F. for two hours. The matrix 15 was then removed from the mold 10 and preheated to 800 F. Zinc was then sprayed at 300 F. upon the matrix 15 to form the die 17. The layers were then allowed to cool to F. requiring two hours. After the combination had cooled the matrix 15 was removed from the die surface 19 and a mixture of 10% plaster of paris binder material 22 and 90% aluminum reinforcing material 24 was deposited within the die 17 opposite the die surface 19. The combination was then oven cured at 250 F. for three hours and allowed to air cool for 24 hours, at which time room temperature was achieved. A die was produced suitable for forming plastics and filament winding.
  • EXAMPLE A wooden mold 10 was coated with a paste wax .004 inch thick. A matrix composed of finely powdered portland cement was deposited on the mold 10 to a thickness of inch and thereafter cured at a temperature of 175 F. for four hours. That matrix 15 was removed from the mold 10 and then sprayed with a /2 inch layer of copper at room temperature. The matrix 15 was then removed from the copper die 17 by means of grit blasting and a Cerro-Bend deposited within the die 17 opposite and die surface 19. Cerro-Bend is a well known low temperature melting (185 F.) alloy of bismuth and lead, used in die work, and is readily available from a number of manufacturers. The mixture was then allowed to set for approximately four hours producing a die suitable for forming plastics.
  • 185 F. low temperature melting
  • a die for forming a plastic article and filament winding comprising in combination,
  • a die for forming plastics comprising in combination,

Description

Oct. 13, 1970 WALKEY ETAL 31,533,271
METAL DIES Filed July 6. 1967 3 Sheets-Sheet 1 HIEATING 26 SOURCE i Q. R
IN VENTORS GEORGE J. WALKEY FRANK N. A'DGATE By W Agent Oct. 13, 1970 wAl-KEY ETAL 3,533,271
METAL DIES Filed July 6, 1967 3 Sheets-Sheet 2 W m W1 M I h MIN.
NEW :Wm...W W "W INVENTORS GEORGE J. WALKEY F|G f FRANK N. ADGATE Agent Oct. 13, 1970 G.J. WALKEY ETAL METAL DIES- 5 Sheets-Sheet :5-
Filed July 6. 1967 FIG-2 INVENTORS GEORGE J. WALKEY FRANK N. ADGATE Unitcd States Patent Office 3,533,271 Patented Oct. 13, 1970 3,533,271 METAL DIES George J. Walkey, Burbank, and Frank N. Adgate,
Granada Hills, Calif., assignors to Lockheed Aircraft Corporation, Burbank, Calif.
Filed July 6, 1967, Ser. No. 657,720 Int. Cl. B21k 5/20 US. Cl. 72-476 4 Claims ABSTRACT OF THE DISCLOSURE A die and the method of fabricating it utilizing the technique of thermal spraying. A matrix of predetermined strength is initially cast over a pattern to a desired thickness. After the matrix hardens it is separated from the pattern, heated, and a metal or other die material sprayed over its formed surface. The combination is then cured and allowed to cool, causing the matrix, but not the die, to crack and facilitating easy separation. The resulting die shell may then be filled with a mixture of reinforcing material and binder and heated, causing the binder to liquefy. Upon cooling the binder solidifies around the reinforcing material, giving great structural integrity to the die shell and producing a tough, high temperature die.
BACKGROUND OF THE INVENTION The ever-increasing use of high strength substances such as titanium in many of todays products has greatly intensified the need for an inexpensive method of fabricating dies. Aircraft and spacecraft, for example, are requiring larger amounts of high strength materials than ever before. However, because only a few parts may be needed and produced from a single die, the conventional hot stamping process commonly used becomes prohibitively expensive.
Many industries have turned to other techniques such as the Shaw process or the Keller method to at least partially alleviate this high cost.
The Shaw process uses a conventional casting technique with a special sand matrix manufactured from Bakelite and resin. While close tolerances are obtainable by this process it is economically unsatisfactory in high temperature applications with hard materials.
The Keller method, on the other hand, is a pantographic-like process and initially entails the making of the finished article as a master. A machine is then slaved, by conventional means such as a stylus bearing against the outer surface of the master, to produce the desired copies. While this method may be utilized for hard materials, it is very slow, comparatively expensive and completely unsuited for tracing complex shapes.
As a consequence of the various disadvantages of the above methods, one approach has been to fabricate dies by means of various thermal spray process. These processes generally involve the deposition of a metallic layer on a plaster casting to produce a die shell. The use of such processes indeed offer several important advantages in that the time required to produce the die as Well as the finished article, is much less than by normal maching methods. In addition, complexity of shape is not an important factor as it is in the Keller method.
However, metal spray techniques in the past have been severely limited to low strength, low temperature melting metals such as Zinc or tin. One reason for this has been the natural tendency of the sprayed metal as it cooled to contact, such shrinkage causing it to separate from the patterned surface. This tendency produced cracks and spalling, apparently due to the uneven thermal stresses produced in the metal when sprayed onto the pattern. Consequently, it has heretofore been very difficult to spray an accurate negative or mold having sufficient strength or rigidity for practical use.
While such dies are suitable for forming low strength materials and for operating at low temperatures, they cannot be used to form strong materials at high temperatures. Thus, titanium, for example, which must be formed at a high-temperature because of its tendency to springback or return to its original shape, could not until now, be formed on a die manufactured by the thermal spray method.
It is, therefore, a purpose of this invention to provide a method of fabricating a strong, high temperature die wherein a substrate or matrix of predetermined strength is deposited upon a pattern to a desired thickness. After being heated and cured, to remove excess water, the matrix is separated from the pattern and is again heated to a temperature compatible with that of the metal to be subsequently deposited thereon. The combination is thereafter placed in a preheated oven and allowed to slowly cool, at which time, the substrate will crack because of its difierences in predetermined strength, thickness, and thermal coefiicient of expansion as compared with those of the metallic layer. Upon having the matrix thoroughly removed from its surface, the resulting metal shell or die is filled with a selected mixture of reinforcing material and binder and heated, causing the binder to liquefy. As the mixture cools, the binder hardens and adheres the reinforcing material to the die shell.
BRIEF DESCRIPTION OF THE DRAWING The procedure of the present .invention as applied to the production of a die is illustrated by the accompanying drawing, wherein:
FIG. 1 is a perspective view of a heated die configuration manufactured in accordance with the invention;
FIG. 2 is a longitudinal section through a mold pattern after the substrate or matrix has been deposited thereon;
FIG. 3 is the matrix of FIG. 2 after it has been removed from the mold pattern and a layer of die material deposited thereon;
FIG. 4 is similar to FIG. 1 and illustrates the die material separated from the matrix with a mixture of reinforcing material and binder in reinforcing relationship therewith;
FIG. 5 illustrates an alternate embodiment of the matrix with a layer of die material deposited thereon;
FIG. 6 is the die material layer of FIG. 5 separated from the matrix with a binder deposited thereon;
FIG. 7 is the die of FIG. 6 with additional layers of die material deposited thereon, and
FIG. 8 is an enlargement of the mixture of reinforcing material and binder of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 14 and 8, there is depicted a mold 10 having a surface 12. dimensionally contoured to a desired configuration and smoothness. In contrast to the molds used in prior art processes, particularly Where sintering procedures are used, mold 10 may be fabricated from an inexpensive material such as plastic, plaster or wood. This economy is possible since the mold 10 and the surface 12 are not subject to deterioration as a result of subsequent spraying steps.
The surface 12 is first coated with a parting agent to provide a parting coating 14. The function of the coating 14 is to facilitate removal of the molded refractory skeleton from the mold 10. In the practice of this invention, the parting agent may be applied in any suitable fashion such as by spraying or pouring. Although several layers of wax material will faciiltate the separation of the skeleton from the mold sprayed Teflon, molybdenum disulfide or lacquer may also be used as the parting agent. Once the mold 10 has been coated with a parting agent, an inorganic matrix or substrate is deposited thereover and over the coated surface 12 by conventional means such as spraying, ladling or the like. The inorganic matrix 15 is fabricated from an aluminide or beryllide such as aluminum oxide or beryllium oxide or from a cement. The matrix 15 is of such a strength, thickness and substance that it is compatible with die material 16 to be sprayed thereon at a subsequent time. It is of primary importance that the substance used for the matrix 15 be of a strength sufiicient to withstand the heat during the preheating procedures and the internal pressures of handling which are produced during the process. For high temperature applications and the ability to withstand internal stresses, a high strength cement has been found to be generally superior to plaster of paris or dental plaster. (38) Holfmaster-43965 Elec. 'Ptg.day 9/18/70 The resulting strength of the deposited matrix 15 is a critical consideration since the matrix 15 must have a compressive strength which is less than the yield strength of the die material 16 which is subsequently deposited thereon. Were it otherwise, die 17 would crack during the cooling process. After a predetermined thickness is reached, the matrix 15 is oven or air cured, depending upon the type of die 17 to be fabricated and the die material to be used.
Highly acceptable results have been obtained by providing a matrix 15 of the high strength cement commercially known as Glass-Rok cured in an oven at 300- 400 F. for a period of approximately two hours. The curing time is, of course, dependent upon the characteristics of the specific material being cured and the curing temperature, but it is required that the water contained within the matrix 15 be completely removed since during the heating cycle any water remaining in the matrix 15 turns to steam, forming internal bubbles, thereby cracking the matrix 15 or deforming the matrix surface 18.
After the matrix 15 cools, it is separated from the mold 10, such removal being facilitated by cracking of mold 10 which usually occurs during the cooling cycle. If the mold 10 does not crack, it may be removed from matrix 15 by use of conventional means (e.g., hammer and chisel). Upon being removed, the matrix 15 is ready to be preheated to a temperature compatible with the die material 16 to be subsequently deposited thereon. The die material 16 itself is usually a metal or metal alloy but may comprise other types of inorganic materials such as plastic, cement or plaster. Thus, while a metallic material is referred to hereinafter, it is to be noted that this is for illustrative purposes only. In addition, an organic which, upon being heated, becomes an inorganic (e.g. calcium lactate into calcium oxide), may be used.
In order to obtain such temperature compatibility of the matrix 15, it is required that the preheat temperature be approximately that which results in a 50% yield strength of the sprayed metal. While some latitude may be taken with regard to this temperature, the above has been found to be generally satisfactory. In handling aluminum materials, for example, a requirement exists that the temperature of the preheated matrix 15 be approximately 800 F., while in handling steel or steel alloys the heating requirement is approximately l500 F.
When the desired preheat temperature is reached, the die material 16 is sprayed on the matrix 15 to form a die 17 of predetermined yield strength, and of thickness compatible with the compressive strength of the matrix 15. During the metal spraying process, the preheat temperature is maintained by conventional and suitable means such as a gas burner or oxyactylene flame (not shown) until such time as the desired thickness of the sprayed metal is achieved. Again it is to be noted that the matrix 15 must be sufficiently thin that its compressive strength is less than the yield strength of the die 17. As an ex- 4 ample, based upon the reported structural properties of a mild steel, such as S.A.E. 1010 (30,000 p.s.i. tensile strength at 1000 F.) and a high strength cement such as Glass-Rok (4,000 to 6,000 p.s.i. compressive strength), a cement matrix 15 having a thickness within the approximate range of to has been found to fail under the compressive load applied by the thermal contraction of a A" mild steel coating at room temperature.
The matrix surface 18 need not be coated with a parting agent as taught by the prior art of metal spraying since the matrix 15 will resist spalling on die surface 19 without the requirement of a coating therebetween because of the preheating of the matrix 15 and the preselected strength of the materials used.
After the layer of die material 16 has been deposited upon the preheated matrix 15, the combination is placed in a preheated oven (not shown) and allowed to slowly cool for a length of time precalculated to result in failure of the matrix 15. The temperature of the preheated oven should be approximately that to which the matrix 15 was heated prior to the deposition of die material.
During the cooling process, the die 17 and the matrix 15 cool and contract at different rates because of their different coefficients of thermal expansion. The usual result is a severe cracking of the matrix 15. However, as previously indicated, this cooling process does not always cause the cracking of the matrix 15. In such case it can be subsequently removed by suitable conventional means, as by hammer and chisel or by grit blasting it with 40 mesh chilled iron grit at p.s.i. A clean metallic surface has been produced by each of the noted removal methods, no apparent damage to die surface 19 having resulted. The die 17 can, by the aforementioned procedure, be produced to any thickness desired, but because of its shell-like configuration would be somewhat limited in strength and thus substantially unsuited for high temperature forming of high strength materials but could, however, be utilized for forming lower strength materials such as plastic and thin aluminum sheet.
Although under normal circumstances the matrix 15 cracks, it is to be noted that the materials used for the die 17 and the matrix 15 may be chosen of materials having nearly identical thermal coefiicients of expansion thereby contracting at almost the same rate. While under these circumstances neither material will crack during the cooling period, this procedure is generally very costly and is therefore economically unsatisfactory over the method previously discussed.
It is of course apparent that in performing the above steps dimensional control, surface hardness and other metallurgical properties of the materials used for the matrix 15 and die 17 should be determined prior to the initiation of the process. This provides the fabricator with the ability to predict and control critical dimensions required to assure that the yield strength of the die 17 is greater than the compressive strength of the matrix 15.
After the combination has cooled the matrix 15 is separated from the die 17 and excess overspray, if any, is removed by conventional means such as by sawing, grinding, or the like, until the desired finished dimensions are obtained. Since the finished dimensions are unaffected by excess overspray, it is not mandatory that it be removed. However, it has been found beneficial in that a more compact, easier handling and lighter weight die can be achieved if the additional material is removed.
When the desired finished dimensions have been achieved, a mixture of binder material 22 (FIG. 4) and reinforcing material 24 (the combination being sometimes referred to as reinforcing mixture) such as epoxy resin and metal shot, respectively, are deposited by pouring, ladling or the like, within a cavity formed in the die 17 opposite its surface 19. The ingredients of the reinforcing mixture are carefully chosen to provide the desired strength of the finished die 17 and in view of temperatures involved in forming the material of the ultimate product for which the die of this invention is provided. After this mixture has been deposited the combination is oven heated to a temperature sufficient to liquefy the binder material 22 which, upon cooling, adheres the reinforcing material 24 to the die 17, thereby forming one continuous, solid, die mass. If a hot forming die is desired to be fabricated, a heating member may be located within the die 17 and surrounded by the reinforcing mixture. The heating member 20 may be of any conventional means such as a high resistance wire or heating rod electrically connected to a heating source 26 by wires 28 and 30 as best illustrated in FIG. 4. The usage of a heating member 20 located within the die serves the dual purpose of heating the reinforcing mixture, thereby eliminating the requirement for oven heating and also permits the finished die to be integrally heated for the purpose of hot forming materials such as titanium. The temperature to which the reinforcing mixture is heated should approximate that to which the matrix 15 and die 17 were previously preheated. The binder material 22 is selected such that it will liquefy at or near the preheat temperature and when cooled cause the reinforcing material 24 to adhere to the interior portion of the die surface 19.
Referring to FIGS. 57, a modified embodiment of the present invention is depicted wherein a matrix 15 having a surface 18 of dimensionally contoured shape and smoothness has a die material 16 deposited thereon. The matrix .15 in the modified embodiment may be of standard composition and for this purpose plaster of paris has been found to be generally satisfactory. The die material 16 sprayed upon the contoured surface 18 need not be heated in the modified embodiment since it has been found that preheat is required only when a thick coating of die material 16 is deposited. In this regard coatings of inch and under do not require the die material to be heated since the internal stress determines the necessity for preheat and is a function of thickness. After the die material 16 has set, a fiber glass binder 22 is deposited over the die material 16 to a thickness of approximately /2 inch. After air curing for about three and one-half hours at room temperature, copper reinforcing material 24 is deposited on the binder 22 at room temperature to a thickness of inch. Finally an additional layer of epoxy impregnated fiber glass binder 22 is deposited over the copper layer. By such construction a composite die 17 may be formed for many useful purposes, such as filament winding or lay up of plastic parts or for the forming of aluminum of thicknesses of .060 inch or less The following examples are generally illustrative of the process:
EXAMPLE 1 A wooden mold 10 of the character illustrated in FIG. 2 and having a desired dimensionally contoured surface 12 was coated with a .005 inch layer of paste wax to form a parting coating 14 over its surface 12. An inorganic matrix 15 of high strength cement was thereafter deposited at room temperature upon the waxed surface 12 until the matrix 15 was /2 inch thick. The matrix 15 was deposited by spraying it over the surface 12 and was precalculated to be of a thinness sufficient to crack during the subsequent cooling steps. The matrix 15 was then oven cured at a temperature of 350 F. for two hours and the mold 10 separated therefrom after it had cooled to room temperature. The matrix 15 was next preheated to 1500 F. and S.A.E. 1010 steel sprayed thereon to a thickness of inch. Upon obtaining the desired thickness, the combination was placed in a preheated oven at 1500 F. and allowed to furnace cool for a period of four hours. The matrix 15 cracked for the reasons previously enumerated and the die surface 19 was cleaned of the residue matrix material by grit blasting with 40 mesh chilled iron grit at p.s.i. A heating rod 20 connected to a heat source 26 and a mixture of 10% sodium silicate binder material 22 and iron shot reinforcing material 24 were then placed within the cavity of the die 17 opposite the die surface 19. The mixture was then heated to a temperature of 1500 F. and allowed to air cool until it reached room temperature. This die was found to be suitable for both cold and hot forming of titanium and other high strength materials at temperatures of 1450 F. and above.
EXAMPLE 2 A Wooden mold 10 having a desired dimensionally contoured surface 12 was coated with molybdenum disulfide to form a parting coating 14 of .004 inch thickness. An inorganic matrix 15 of beryllium oxide was then deposited upon the coating 14 to a thickness of A inch, air cured at a temperature of 350 F. and then allowed to cool for 24 hours to room temperature. Upon cooling, the matrix 15 separated from the mold 10 and was then preheated to 800 F. Aluminum was thereafter sprayed on the matrix 15 while the matrix 15 was maintained at 800 F. by a gas burner. A metal die shell of a 17 /2 inch thickness in length was formed and the combination thereafter placed in an oven preheated to 800 F., the oven then being turned off and the die allowed to cool for four hours. Upon removal of the die from the oven, the matrix 15 was found to be cracked. The die surface 19 was cleaned by grit blasting with 40 mesh iron grit at 80 p.s.i. A mixture of 5% epoxy resin binder material 22 and chopped fiber glass reinforcing material 24 was then deposited within the die 17 opposite the die surface 19. The combination was then oven cured at a temperature of 150 F. and subsequently allowed to air cool for a period of 24 hours. The die was found suitable for cold forming low strength metals.
EXAMPLE 3 A plastic mold 10 having a predetermined contoured surface 12 was coated with molybdenum disulfide to a thickness of .002 inch to form a parting coating 14 over its surface 12. A plaster of paris matrix 15 was then deposited, at room temperature, over the parting coating 14. The matrix 15 was then oven cured at a temperature of 350 F. for four hours and thereafter removed from the mold 10. Aluminum was next sprayed over the matrix 15 to a thickness of inch. The matrix 15 and the aluminum were not preheated during this step since the resultant internal stresses determine the preheating requirement and are a function of the thickness of the material. Epoxy impregnated fiber glass was then deposited over the aluminum at room temperature to a thickness of /2 inch. The combination was then air cured for three and one-half hours at room temperature. Upon reaching room temperature a 4; inch layer of copper was deposited at room temperature on the fiber glass. The die 17 was then filled with epoxy impregnated fiber glass reinforcing material 24 and air cured for 3 /2 hours. The die was found to be suitable for filament winding and forming aluminum of thickness of .060 inch or less.
EXAMPLE 4 A plastic mold 10 was coated with lacquer to form a parting coating 14 of a thickness of .003 inch. Dental plaster was then deposited on the coating 14 to a thickness of A inch and the combination oven cured at 225 F. for two hours. The matrix 15 was then removed from the mold 10 and preheated to 800 F. Zinc was then sprayed at 300 F. upon the matrix 15 to form the die 17. The layers were then allowed to cool to F. requiring two hours. After the combination had cooled the matrix 15 was removed from the die surface 19 and a mixture of 10% plaster of paris binder material 22 and 90% aluminum reinforcing material 24 was deposited within the die 17 opposite the die surface 19. The combination was then oven cured at 250 F. for three hours and allowed to air cool for 24 hours, at which time room temperature was achieved. A die was produced suitable for forming plastics and filament winding.
EXAMPLE A wooden mold 10 was coated with a paste wax .004 inch thick. A matrix composed of finely powdered portland cement was deposited on the mold 10 to a thickness of inch and thereafter cured at a temperature of 175 F. for four hours. That matrix 15 was removed from the mold 10 and then sprayed with a /2 inch layer of copper at room temperature. The matrix 15 was then removed from the copper die 17 by means of grit blasting and a Cerro-Bend deposited within the die 17 opposite and die surface 19. Cerro-Bend is a well known low temperature melting (185 F.) alloy of bismuth and lead, used in die work, and is readily available from a number of manufacturers. The mixture was then allowed to set for approximately four hours producing a die suitable for forming plastics.
The products produced in relation to these examples, while suitable for the indicated uses, may obviously be found readily acceptable for other applications as well.
The various features and advantages of the invention are thought to be clear from the foregoing description. Other advantages not specifically enumerated will undoubtedly occur to those skilled in the art as well as other modifications of the preferred embodiment illustrated. The following claims measure the invention in a die as illustrated by the above Examples 1, 3, 4 and 5, respectively.
We claim:
1. A die for cold and hot forming a high strength material at temperatures at and above 1450 F. and having a solid continuous mass formed from (a) and (b) below and comprising in combination,
(a) a S.A.E. 1010 sprayed steel forming a shell and a die surface thereon,
(b) a mixture formed of substantially 90% iron shot and 10% sodium silicate deposited in said shell and heated to a temperature of 1500 F.
the combination of (a) and (b) then being air cooled to produce said die.
2. A die for filament winding, and forming aluminum,
and the like, of .060 inch or less thickness, comprising in combination,
(a) sprayed aluminium forming a shell and a die surface thereon,
(b) epoxy impregnated fiber glass deposited at room temperature within said shell, the combination of (a) and (b) then being air cooled at room temperature for approximately 3 /2 hours,
(0) a layer of copper deposited at room temperature on said fiber glass, and
(d) additional epoxy impregnated fiber glass filling said shell, being air cured thereto, to produce said die.
3. A die for forming a plastic article and filament winding, comprising in combination,
(a) sprayed zinc formed into a shell and a die surface thereon for said die at 300 F. and cooled to 100 F. in substantially 2 hours,
(b) a reinforcing material deposited Within said shell and formed substantially of aluminum and 10% plaster, said material and shell being oven cured at substantially 250 F. for 3 hours,
the combination of (a) and (b) then being air cooled for substantially 24 hours.
4. A die for forming plastics comprising in combination,
(a) a sprayed copper layer forming a die surface and shell for said die,
(b) a low temperature melting alloy of bismuth and lead deposited within said shell,
the combination of said copper layer and alloy producing said die upon setting for approximately 4 hours.
References Cited UNITED STATES PATENTS 1,835,916 11/1933 Ragsdale 76-107 3,015,292 1/ 1962 Bridwell 72342 3,125,974 3/1964 Toulmin 76107 3,195,341 7/1965 Zunich 72475 3,422,663 1/1969 James et al. 76-107 LOWELL A. LARSON, Primary Examiner US. Cl. X.R. 76-107
US657720A 1967-07-06 1967-07-06 Metal dies Expired - Lifetime US3533271A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US65772067A 1967-07-06 1967-07-06

Publications (1)

Publication Number Publication Date
US3533271A true US3533271A (en) 1970-10-13

Family

ID=24638401

Family Applications (1)

Application Number Title Priority Date Filing Date
US657720A Expired - Lifetime US3533271A (en) 1967-07-06 1967-07-06 Metal dies

Country Status (1)

Country Link
US (1) US3533271A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3926029A (en) * 1974-04-30 1975-12-16 Us Air Force Heated die assembly
US5079974A (en) * 1991-05-24 1992-01-14 Carnegie-Mellon University Sprayed metal dies
US5638724A (en) * 1993-10-01 1997-06-17 The Boeing Company Method of making a ceramic die
US20150266079A1 (en) * 2014-03-19 2015-09-24 Ford Global Technologies, Llc Composite dies and method of making the same

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1835916A (en) * 1926-08-02 1931-12-08 Gen Electric Circuit controlling means
US3015292A (en) * 1957-05-13 1962-01-02 Northrop Corp Heated draw die
US3125974A (en) * 1964-03-24 figure
US3195341A (en) * 1961-11-20 1965-07-20 Nat Lead Co Die apparatus
US3422663A (en) * 1963-08-22 1969-01-21 Gen Motors Corp Sheet metal forming dies

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3125974A (en) * 1964-03-24 figure
US1835916A (en) * 1926-08-02 1931-12-08 Gen Electric Circuit controlling means
US3015292A (en) * 1957-05-13 1962-01-02 Northrop Corp Heated draw die
US3195341A (en) * 1961-11-20 1965-07-20 Nat Lead Co Die apparatus
US3422663A (en) * 1963-08-22 1969-01-21 Gen Motors Corp Sheet metal forming dies

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3926029A (en) * 1974-04-30 1975-12-16 Us Air Force Heated die assembly
US5079974A (en) * 1991-05-24 1992-01-14 Carnegie-Mellon University Sprayed metal dies
US5638724A (en) * 1993-10-01 1997-06-17 The Boeing Company Method of making a ceramic die
US20150266079A1 (en) * 2014-03-19 2015-09-24 Ford Global Technologies, Llc Composite dies and method of making the same
US9302310B2 (en) * 2014-03-19 2016-04-05 Ford Global Technologies, Llc Composite dies and method of making the same

Similar Documents

Publication Publication Date Title
US3631745A (en) Method of fabricating metal dies
US4231982A (en) Method for the production of tools for deep drawing, moulding, extruding and the like
US3721534A (en) Method of forming protective coatings on ferrous metal and the resulting article
FR2399487A1 (en) METHOD FOR MAKING A METAL COATING RESISTANT TO CORROSION AT HIGH TEMPERATURE
US5079974A (en) Sprayed metal dies
US6134785A (en) Method of fabricating an article of manufacture such as a heat exchanger
US2886869A (en) Graphite refractory molds and method of making same
HU185397B (en) Heat-proof details and method for producing same
US2966423A (en) Method of producing metal deposits
US3139658A (en) Production of tungsten objects
EP0190114B1 (en) Molded metal object and method to manufacture the same
US3533271A (en) Metal dies
US4537742A (en) Method for controlling dimensions of RSPD articles
US2826512A (en) Method of coating and resulting product
US3461944A (en) Method of manufacturing a lined iron-base article
US3141756A (en) Glass forming element and method of manufacture
JPH02182343A (en) Shell modle for manufacturing metal spring
US4608317A (en) Material sheet for metal sintered body and method for manufacturing the same and method for manufacturing metal sintered body
US4541474A (en) Process for manufacturing a moulding plunger for hollow glass objects
KR100723126B1 (en) Method for manufacturing molds and dies by thermal spraying
US5711062A (en) Process for manufacture of a fluid containment element
US3158912A (en) Controlled grain size casting method
US2754570A (en) Method of producing a cast alloy coated oxidizable metal article
US3053610A (en) Flame-sprayed metal article
DE3736661C1 (en) Process for the production of layers