US3859055A

US3859055A - Tungsten-nickel-iron shaping members

Info

Publication number: US3859055A
Application number: US182886A
Authority: US
Inventors: Earl I Larsen
Original assignee: PR Mallory and Co Inc
Current assignee: Duracell Inc USA
Priority date: 1966-10-27
Filing date: 1971-09-22
Publication date: 1975-01-07
Anticipated expiration: 1992-01-07

Abstract

This invention is directed to the use of tungsten base alloys containing about 1 to 12 weight percent nickel and about 0.5 to 8 weight percent iron for die casting dies, molds, cores and other metal shaping members.

Description

Larsen Jan. 7, 1975 [75] Inventor: Earl l. Larsen, Indianapolis, Ind.

[73] Assignee: P. R. Mallory & Co., Inc.,

Indianapolis, Ind.

[22] Filed: Sept. 22, 1971 [21] Appl. No.: 182,886

Related U.S. Application Data [63] Continuation-impart of Ser. No. 590,088, Oct. 27, I966, abandoned, and a continuation of Ser. No. 855,712, Sept. 5, 1969, abandoned.

[52] U.S. Cl 29/182, 75/176,164/138 [51] Int. Cl. C22c H04 [58] Field of Search 29/182; 75/176; 164/138 [56] References Cited UNITED STATES PATENTS 3,307,982 3/1967 Milligan et a1 148/133 X 400 Lu :1: o E v 300 I U) m Lu 0 D 200 O a:

w o E 100 n: 3 an TUNGSTEN-NICKEL-IRON SHAPING MEMBERS FOREIGN PATENTS OR APPLICATIONS 760,113 10/1956 Great Britain 29/182 OTHER PUBLICATIONS Hurd, D. T., New Factor in Copper Alloy Casting," Precision Metal Molding, 23(10): p. 3738, Oct. 1965, TS200I35.

Primary Examiner-Benjamin R. Padgett Assistant Examiner-R. E. Schafer Attorney, Agent, or FirmHoffmann Meyer & Hanson [57] ABSTRACT This invention is directed to the use of tungsten base alloys containing about 1 to 12 weight percent nickel and about 0.5 to 8 weight percent iron for die casting dies, molds, cores and other metal shaping members.

7 Claims, 3 Drawing Figures IS /o Nl9/o CO5% MO 0.6 /0 TI "0. l /o Al-BALANCE Fe 0.4% C-O.35% NIH-1.1% Si- 50% Cir-0.9% V-l.25% M0- BALANCE F8 CYCLES x 1000 TUNGSTEN-NICKEL-IRON SHAPING MEMBERS This application is a continuation-in-part of Application Ser. No. 590,088, filed Oct. 27, 1966 and a continnation of application Ser. No. 855,712, filed Sept. 5, 1969, both abandoned.

Prior to this invention, most of the materials used as die casting dies, molds, cores, core pins and other metal shaping members were made from tool steel. A typical tool composition for such die casting molds contains about 5 percent chromium, 0.4 percent carbon, and minor amounts of vanadium and molybdenum.

While such tool steel dies are fairly satisfactory for forming low melting point metals and alloys of zinc, magnesium, and aluminum, a die material that would have longer life, resist erosion better, resist spalling and cracking, and be easier to machine would be highly desirable. When die casting the higher melting point metals and alloys such as copper, brasses, and bronzes, these undesirable characteristics are even more pronounced. Thus while prior art tool steel dies may be capable of making many thousands of parts of castings from zinc or aluminum alloys before they must be replaced, this is not true with copper or its alloys such as brasses or bronzes. Forexample, when die casting a brass alloy containing approximately 60 percent copper-40 percent zinc at a temperature of 1,750F, the tool steel may begin to crack and spall after as few as 1,000 castings have been made. Such spalling and cracking occurs when the die is subjected to thermal stresses created by the molten high temperature alloys being forced into the die under high pressure; while erosion of the die is generally caused by the washing action of such high temperature alloys.

It is, therefore, an object of the invention to provide die casting dies or molds, cores and other metal shaping members which have a long life.

It is another object of the invention to provide die casting dies, molds, cores, core pins and other metal shaping members which will be resistant to erosion when subjected to the washing action of molten metals and alloys, particularly non-ferrous metals and alloys such as copper, brass or bronze, aluminum and aluminum alloys, zinc and zinc alloys, magnesium and magnesium alloys.

Another object of the invention is to provide die casting dies, and other shaping members which will resist cracking or spalling when subjected to the thermal stresses created by molten metals and alloys being forced into dies and molds under pressure.

Another object of the present invention is to provide shaping members which have resistance to thermal shock.

Still another object of the invention is to provide shaping members which have resistance to erosion.

Still another object of the invention is to provide shaping members which are resistant to spalling.

Still another object of the invention is to provide shaping members which are resistant to cracking.

Still another object of the invention is to provide shaping members which have low surface roughness after continued operation.

It is another object of the present invention to provide shaping members which require cleaning less frequently.

It is another object of the invention to provide shaping members having good mechanical properties both at room temperature and at elevated temperatures encountered in die casting operations.

Another object of the present invention is to provide shaping members which rapidly remove heat from the metals and alloys being cast.

Another object of the present invention is to provide a method of casting resulting in increased life of casting components including dies, molds, cores, core pins and other shaping members.

Another object of the present invention is to provide a method of increasing the life of casting components including dies, molds, cores, core pins and other shaping members.

Other objects will be apparent from the following description and drawings.

In the drawings:

FIG. 1 is a cross section of an exemplary die casting die or mold;

FIG. 2 is a cross section of another exemplary die or mold; and

FIG. 3 is a graph comparing the surface roughness of dies made in accordance with the present invention with various die materials of the prior art.

Generally speaking, the objects of the invention are accomplished by utilizing a die, mold, core or other metal shaping member having a molding surface com prising a tungsten-iron-nickel alloy. For example, the shaping members may comprise one or more die blocks defining a portion of a die cavity, as well as cores, core pins and other metal shaping members commonly associated with non-ferrous casting, particularly die castings, fabricated from an alloy comprising -99 percent tungsten by weight, the balance being essentially iron and nickel, with said shaping member constituting at least a portion of the casting cavity. The conduit or conduits, or other means to conduct molten metal to the casting cavity may also utilize surfaces made of a tungsten-nickel-iron alloy, if desired.

Referring now to FIG. 1, an exemplary die casting die or mold 10 in the main comprises at least two blocks 11 and 12 each having a cavity 13 and 14 the blocks being positioned adjacent each other to form a continu ous die cavity 15 for forming a metal part. As shown, the casting die is held within a block housing 16 com posed of two

sections

17 and 18. Molten metal from which the part is to be formed, is fed to the cavity 15, under pressure, by way of conduit 19. The shape of cavity 15 is determined by molding surfaces 13a and 14a. The shape of the cavity as shown in FIG. 1 is by way of illustration only, the particular shape being cast being dependent upon the shape of the part desired.

An important feature of the present invention lies in the material used to fabricate the shaping members such as blocks 11 and 12 which define the surfaces 13a and 14a. The present invention makes use of a tungsten base alloy containing iron and nickel to give dies and other shaping members longer life even though high melting point metals and alloys such as copper, bronzes and brasses or other non-ferrous metals such as aluminum, aluminum alloys, zinc, zinc alloys, magnesium and magnesium alloys are being molded. It is within the scope of the invention to form such surfaces from a tungsten-nickel-iron alloy coating upon the die blocks, cores, core pins, or other shaping members.

Tungsten has little, if any, solubility in copper. This renders the material especially useful for the forming of parts from the afore-mentioned high melting point materials. However, pure tungsten has low mechanical properties, is relatively brittle and is difficult to fabricate. Very high sintering temperatures are required, and to obtain a completely dense structure it usually is usually about 0.15 cgs units and preferably it is about 0.20 cgs units. The high thermal conductivity of the shaping members of the present invention tends to result in solid, sound casting; and the rapid rate of heat must be hot worked mechanically. 5 removal tends to reduce welding and erosion and ther- On the other hand, tungsten based alloys containing mal stresses. small percentages of iron and nickel can be formed by Another important property of the shaping members powder metallurgy and liquid phase sintered at reasonof the present invention is that of the surface roughness able temperatures to make articles having densities of the shaping member cavity after prolonged use. In very near theoretical with high yield and tensile the case of steel shaping member cavities, the surface strengths, good ductility, good impact strength, and roughness has been such that after as few as six to ten high resistance to thermal shock. Such alloys are thousand cycles of casting shots the cavities must be readily machined utilizing ordinary machine shop tools polished and/or machined because the surface has beand practices so that intricate cavity shapes can be come too rough, resulting in casting defects such as readily formed. And tungsten-iron-nickel alloys are poor surface quality and/or cracking. This, usually insusceptible to heat treatment which increases not only volves shutting down the operation and/or down time, their tensile properties, but more important for casting etc A surface roughness above ut 300 X 10 applications, their ductility. inches or higher is often considered to be too rough.

The shaping members of the present invention should By rthe shaping be s o the present incontain from about 85 to about 99 weight percent tungvention can withstand many more cycles of operation sten, from about 1 to about 12 percent nickel and from before such polishing and/or machining is necessary. about 0.5 to about 7.5 percent iron. The ratio of nickel The cavity of the shaping members of the present into iron in the shaping members of the present invention vention almost always have a surface roughness below should b f b t 1 t 1 t about 4 t 1, about 300 X 10 inches after 50,000 cycles. It is usu- The p f d range f th h i members f th ally below 300 X 10 inches after 70,000 cycles and present invention is from about 90 to about 98 weight y Often below 300 X 10*; inches after 80,000 y percent tungsten, from about 1.5 to about 8 percent In fact, in a y instances the Surfacfi roughness is nickel and from about 0.5 to about 5 percent iron. Prefbelow 200 X after 50,000 cycles, and even below erably, the ratio of nickel to iron is from about 1.5 to 200 X inches after 701000 or 80,000 cycles- 1 to about 3 to 1 With particular reference to FIG. 2, an exemplary ap- Th h i members f h present invention gemplication of the present invention is described. In FICi. ally have a tensile strength of at least 120,000 psi at aflle castmg (he or mold 2015 formed P l mom temperature d a i l Strength f at least sections or blocks 21 and 22, the blocks being fabri- 75 000 i at room temperature Elongation is imPorcated from an alloy consisting essentially of 95 percent tant because the shaping members must withstand ther- 92 percenfi nickel and Percent "'9" by mal shock. The elongation is usually at least 3 percent Yvelghti blocks fi formed y q Phase ffor this reason and is often at least 5 percent (inches in g- T dle held Wlthm a housmg 23 that 15 2 inches). Through heat treating elongations of from 7 prmclpany made P of two

Sections

24 and 25 and to 25 percent .can be achieved and elongations in this backlng P 36 and range are the most preferred for applications requiring Each 9 of the contains a cavity and 29 particularly high resistance to thermal Shock 1 each having a mold surface 20 and 31 the cavities being The preferred method of heat treatment comprises machined into the blocks.

Cavities

28 and 29 together heating the sintered compact to a temperature of with the space 32 formed by the spaced relationship of 5000 12000C in a neutral or slightly reducing atm0 the

blocks

21 and 22 form'the continuous die cavity 3 3. sphere for about one-half to 12 hours and then quenchh Partlcular part belng formed s P m ing rapidly this instance comprises a tube having a /a inch I.D. and

. 1 Tensile strength at elevated temperature is very ima mch a length on Inches" It has a A mch portant for the Shaping members of the present inven thick collar X 2 inch 0.1). at one end. The molten metal tion. It has been found that in short time tensile tests form the tube fed to the cavlty through uall be obtained g i l gz gifig gg igzg g fiz z z After forming

blocks

21 and 22 with their cavities,

SHORT TIME TENSILE STRENGTHS Composition Temp (Fl Tensile Strengths (psi) W, 7 Ni, 3Fe W, 3.5Ni, 1.5Fe

1200F 65,000 psi 70,000 psi 72,000 si 1500F 40,000 psi 45,000 psi 47,000 psi I800F 20,000 psi 27,000 si 30,000 psi 2000F 15,000 psi 19,000 psi 20,000 psi the blocks were heat treated to increase their ductility such that an elongation of about 15 percent was achieved. While not shown in FIG. 2, another die casting die identical in structure to that shown but constructed of tool steel is positioned in the

split block housings

24 and 25 such that comparative results could The material used for casting was 60 percent cop-' per-40 percent zinc alloy by weight. The temperature of the dies was maintained at about 500F by means of a gas heater. The temperature of the molten brass alloy was l,'750F. The alloy was injected into the die cavities at a pressure of about 18,000 psi.

After each stroke of the die casting machine in which a casting was made in each of the different dies, the cavities were cleaned of chips, flakes or flash remaining from the casting operation. This was done with an air blast which contained an oil, graphite, or other hydrocarbon compound. This left a carbonaceous film on the die cavities which assisted in releasing the brass casting from the dies. After eight hours, it was necessary to remove the tool steel die to clear away the hard carbon base film that had built up in the cavity. The same type of film built up or formed very slowly on the tungsteniron-nickel alloy cavity and required cleaning only after 80 to 100 hours of operation. Thus there was much less down time and loss of production with the tungsteniron-nickel die.

Under these conditions, the tool steel dies had an average life on the order of 5,000 castings. At this point they cracked and abraded to such an extent that the castings could not be ejected. The cavity surface roughness was above 300 X inches. An examination of the tungsten-iron-nickel dies after they had produced 13,500 castings revealed them to be essentially the same as when they had been put into operation (well below 200 X 10 inches). In fact, the die continued in operation until after about 56,000 cycles when the test was stopped, but at which time the surface roughness was below 200 X 10' inches.

With reference to FIG. 3, there is shown a graph showing the relationship of the cavities surface roughness as it varies with the number of castings made for the types of tool steels tested and the tungsten-ironnickel die. Note the relatively little tendency for the surface roughness of the tungsten-nickel-iron die to increase.

What is claimed is:

l. A shaping surface for shaping a molten high melting point material, the surface consisting essentially of about I to about 12 wt. percent Ni, about 0.5 to about 7.5 wt. percent Fe, the ratio of Ni to Fe being from about 1:1 to about 4:1, and about to about 99 wt. percent W, the shaping surface having a short time elevated temperature strength at about 1,800 of at least about 20,000 psi and at about l,500F of at least about 40,000 psi, a thermal conductivity of at least about 0.15 cgs units, an elongation of at least about 3 percent, and having a surface roughness of not more than about 300 X 10 inches after 50,000 cycles of shaping molten high melting point materials.

2. The shaping surface of claim 1, wherein the shaping surface consists essentially of about 1.5 to about 8 wt.% Ni, about 0.5 to about 5 wt.% Fe, the ratio of Ni to Fe is from about 1.511 to about 3:1, and about to 98 wt. percent W, the thermal conductivity of the shaping surface is at least 0.2 cgs units.

3. The shaping surface of claim 2, wherein the shaping surface consists essentially of about 7 wt.% Ni, about 3 wt.% Fe, the balance W.

4. The shaping surface of claim 2, wherein the shaping surface consists essentially of about 3.5 wt.% Ni, about 1.5 wt.% Fe, the balance W.

5. The shaping surface of claim 1, wherein the shaping surface is selected from the group consisting of a mold surface, a die surface, a core pin surface, and a core surface.

6. In a method of shaping a molten high melting point material including the steps of contacting the molten material with the shaping surface of claim 1 to shape the molten material, cooling the molten shaped mate rial to solidify the material, and removing the solidified shaped material from contact with the shaping surface.

7. In the method of claim 6, wherein the material to be shaped is selected from the group consisting of Cu, bronze, brass, Cu base materials, Al, A] base materials,

Zn, Zn base materials, Mg, and Mg base materials.

Claims

1. A SHAPING SURFACE FOR SHAPING A MOLTEN HIGH MELTING POINT MATERIAL, THE SURFACE CONSISTING ESSENTIALLY OF ABOUT 1 TO ABOUT 12 WT PERCENT NI, TO ABOUT 0.5 TO ABOUT 7.5 WT. PERCENT FE, THE RATIO OF NI TO FE BEING FROM ABOUT 1:1 TO ABOUT 4:1 AND ABOUT 85 TO ABOUT 99 WT. PERCENT W. THE SHAPING SURFACE HAVING A SHORT TIME ELEVATED TEMPETATURE STRENGHT AT ABOUT 1,800* OF AT LEAST ABOUT 20,000 PSI AND AT ABOUT 1,500*F OF AT LEAST ABOUT 40,000 PSI, A THERMAL CONDUCTIVITY OF AT LEAST ABOUT 0.15 CGS UNITS, AN ELONGATION OF AT LEAST ABOUT 3 PERCENT, AND HAVING A SURFACE ROUGHNESS OF NOT MORE THAN ABOUT 300 X 10**-6 INCHES AFTER 50,000 CYCLES OF SHAPING MOLTEN HIGH MELTING POINT MATERIALS.

2. The shaping surface of claim 1, wherein the shaping surface consists essentially of about 1.5 to about 8 wt.% Ni, about 0.5 to about 5 wt.% Fe, the ratio of Ni to Fe is from about 1.5:1 to about 3:1, and about 90 to 98 wt. percent W, the thermal conductivity of the shaping surface is at least 0.2 cgs units.

6. In a method of shaping a molten high melting point material including the steps of contacting the molten material with the shaping surface of claim 1 to shape the molten material, cooling the molten shaped material to solidify the material, and removing the solidified shaped material from contact with the shaping surface.

7. In the method of claim 6, wherein the material to be shaped is selected from the group consisting of Cu, bronze, brass, Cu base materials, Al, Al base materials, Zn, Zn base materials, Mg, and Mg base materials.