US3333955A

US3333955A - Aluminum alloy and sole plate for electric iron and the like made therefrom

Info

Publication number: US3333955A
Application number: US400412A
Authority: US
Inventors: Lancelot H Walker; James E Hauafee
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1964-09-30
Filing date: 1964-09-30
Publication date: 1967-08-01
Anticipated expiration: 1984-08-01

Description

1. 1967 L.YH. WALKER ETAL ALUMINUM ALLOY AND SOLE PLATE FOR ELECTRI I LIKE MADE THEREFROM Filed Sept. 30, 1964 Tic} l.

C IRON INVENTORS wcaor f/f/Yky Mum dame-s focave/iw rrc United States Patent 3 333 955 ALUMINUM ALLOlK AND SOLE PLATE FOR ELECTRIC IRON AND THE LIKE MADE THEREFROM Lancelot H. Walker, Greenwich, Conn., and James E.

Hanafee, Cleveland, Ohio, assignors to The International Nickel Company, Inc., New York, N.Y., a corporation of Delaware Filed Sept. 30, 1964, Ser. No. 400,412 12 Claims. (Cl. 75142) The present invention relates to electrically heated kitchenware and the like, including electrically heated irons, frying pans, grlddles, etc., and more particularly to metallic hot plate elements therefor having heated working surfaces which are subjected in use to forceful contact with hard articles or particles tending to cause surface damage.

The art of ironing clothes by hand is very old, so old that the name of the tool therefor dates back to times when electricity was not available for heating and hand irons for ironing clothing, bedding, etc., were heated by external methods such as by heating on a kitchen stove and were in fact made principally of iron. Before the advent of electric heating, it was accepted that hand irons need be relatively heavy in order to have high heat capacity and the characteristics of cast iron were considered satisfactory for hand irons. When internally electrically heated hand irons were successfully developed, it was found that the high heat capacity and high weight of the old externally heated irons were not necessary or even desirable in electric irons and there arose new requirements for high thermal conductivity and relatively lightweight in the hot plate elements, i.e., the sole plates,

of electric irons. In view of the need for high thermal conductivity and lightweight, the manufacturers of elecric irons have made electric irons with sole plates of aluminum alloys instead of iron for many years. However, although some advantages were derived from making sole plates of aluminum alloys instead of cast iron, aluminum alloy sole plates in the prior art suffer serious disadvantages in having poor resistance to surface damage and marring such as by indentation or scratching. During the many years of use of aluminum alloy sole plates there has been in the electric iron industry a long standing need for electric iron sole plates having improved high resistance to surface damage, e.g., resistance to scratching and to indentation by hard sharp objects, along with other desired characteristics, including high thermal conductivity, lightweight, toughness, low cost, machinability and capability of being polished to a highly smooth, lustrous finish. When in use, sole plates are sometimes in contact with moderately corrosive agents such as tap water, steam, starch, soaps, detergents, bleaching compounds, etc., and should be resistant to corrosion by such agents and also to oxidation and discoloration.

Damage and marring of electric iron sole plates occurs by indentation when the plates are struck, pushed or otherwise forced against hard sharp articles or particles and by scratching when the plates are moved across sharp objects such as pins, zippers, snaps, buttons, etc., and occurs under on-shelf conditions when the plate is at room temperature prior to sale or between periods of service, e.g., when stored on a shelf in a kitchen, and also under in- 3,333,955 Patented Aug. 1, 1 967 ice service conditions when the plate is at elevated temperature. In-service temperatures of sole plates usually are about 250 F. to 450 F., e.g., 400 F., and occasionally can be up to a maximum of about 600 F. Accordingly, it is highly advantageous that electric iron sole plates have improved high resistance to surface damage and marring when at room temperature prior to being in service, when in service at elevated temperatures up to 600 F. and when at room temperature after being heated in service. For the sake of economy in commercial production, it is advantageous, and in fact required by some manufacturers, that electric iron sole plates be made of an alloy which has good castability for permanent mold casting and/or die casting, possesses the desired character istics when in the chill-cast (including permanent-mold cast or die-cast) condition and has good retention of thedesired characteristics after being heated to elevated temperatures up to 600 F. and cooled to room temperature. Problems of providing improved sole plates having improved resistance to indentation require retaining desired characteristics of currently used sole plates and providing increased room temperature hardness, hot hardness and good retention of hardness after heating. Worthwhile improvements in scratch resistance do not inherently flow from improvements in hardness and providing sole plates having improved scratch resistance is a distinct problem in addition to obtaining improved resistance to indentation.

Similar problems involving need for an improved combination of resistance to surface damage, high thermal conductivity, and other aforementioned characteristics also arise in the case of other electrically heated kitchenware, including Skillets, frying pans, hot platters, broiling pans, griddles, etc., comprising metallic hot plate elements adapted to be heated from one surface to a temperature of at least about 212 F. or higher by an electric heating element and having in addition a substantially smooth, flat, heated Working surface which is subjected in use at elevated temperature to forceful contact by hard articles tending to produce surface damage of localized indentations or scratches. For example, in an electrically heated frying pan the metallic portion thereof which includes the cooking surface isa hot plate adapted to be heated from one surface by an electric heating element and has in addition a substantially smooth, flat, working surface (the cooking surface thereof) which is subjected in use to forceful contact by steel forks, knives and/or spatulas tending to produce localized indentations or scratches.

Although many attempts were made to overcome the foregoing difficulties and disadvantages and other difliculties, none, as far as we are aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that improved electrically heated kitchenware hot plate elements having improved high resistance to surface damage, including resistance to scratching and indentation, and also other desired and/or necessary characteristics of electrically heated kitchenware generally can be provided in accordance with the present invention.

It is an object of the present invention to provide an article of electrically heated kitchenware comprising a hot plate having a working surface characterized by improved high resistance to surface damage and marring, high thermal conductivity, lightweight, satisfactory toughness, including impact strength, good machinability and polishability, and adequate corrosion resistance.

Another object of the invention is to provide a new electric iron sole plate.

The invention also contemplates providing a new aluminum-base alloy characterized in the chill-cast condition by improved scratch resistance at room temperature and at elevated temperatures and by improved high room temperature hardness, hot hardness and retention of hardness after heating.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawing in which:

FIGURE 1 depicts a plan view, viewed toward the working surface, of an electric iron sole plate within the contemplation of the present invention; and

FIGURE 2 is a vertical cross-sectional view of the sole plate of FIGURE 1 taken along the line AA of FIG- URE 1.

Generally speaking, the present invention contemplates in an article of heated kitchenware and the like a new and improved metallic hot plate adapted to be heated from one sufrace to a temperature of at least about 212 F. or higher and having in addition a substantially smooth, flat, working surface which is subjected in use at elevated temperature to forceful contact by hard articles, including hard particles, tending to produce surface damage of local indentations. The present invention contemplates a new electric iron sole plate or other heated kitchenware plate made of a special aluminum-nickel alloy containing about 5% to about 15% nickel, about 2% to about 12% silicon and up to about 14% copper with the total percentage of silicon plus copper being about 7% to about 17%, up to about 1.5% magnesium, with balance essentially aluminum. The metal at the working surface of the hot plate of the invention is in a chill-cast condition characterized by a chill-cast microstructure and by relatively high hardness as compared to the hardness of the same metal when in the annealed, or an otherwise slowly cooled, condition. The chill-cast microstructure extends at least about one-sixteenth of an inch, usually at least one-quarter of an inch, from the working surface and has a refined metallographic structure characterized by small intermetallic particle size, fine grain size and small dendrite cell size such as are known by aluminum metallurgists to generally characterize chill-cast aluminum alloys. The metal more remote than about one-sixteenth of an inch from the working surface may or may not be in a chillcast condition. The working surface of the hot plate of the invention is characterized by improved high resistance to surface damage by indentation at room temperature and at elevated temperatures when in the chill-cast condition and also after being heated to elevated temperatures up to 600 F. for prolonged periods, as compared with the resistance to indentation characteristics of hot plates made of otherwise similar aluminum alloys without nickel. Surface indentation to which the working surface of the hot plate of the invention is resistant includes damage by nicking, hitting, piercing, denting and highly localized penetration of the metal, with plastic deformation thereof, such as occurs when the ironing surface of a sole plate is pressed against a hard point or particle or when the point of a steel fork is struck against the cooking surface of a frying pan. Resistance to indentation is evidenced by results of hardness tests such as the Rockwell F and the Rockwell H tests which show relatively high resistance to indentation by relatively high hardness numbers. In addition, the special aluminum-nickel alloy of which the hot plate of the invention is made is characterized by good castability, machinability and polishability and by high thermal conductivity, adequate toughness and impact resistance, resistance to corrosion, oxidation and discoloration. Further, the aforedescribed special aluminum-nickel alloy when in the buffed and/ or polished condition has a highly lustrous, white-metal finish which is appreciably whiter and more silvery than the usual color of aluminum.

In carrying the invention into practice to produce kitchenware hot plates characterized by high chill-cast hardness of at least about 65 Rockwell H at temperatures up to 600 F. which is retained when the plate is heated at temperatures up to 600 F. for prolonged periods of time such as 24 hours or 120 hours, it is advantageous that the hot plate be of an advantageous alloy containing about 5% to about 15% nickel, about 3% to about 12% silicon and about 2.5% to about 14% copper with the total of copper plus silicon equal to about 9.5% to about 17% of the alloy, up to about 1.5% magnesium, with balance essentially aluminum. The presence of about 2.5% to about 14% copper, more advantageously about 8% to about 12%, in the alloy of the plate is advantageous for obtaining high hardness. An advantageous alloy composition for die-cast sole plates in accordance with the invention contains about 5% to about 13% nickel, about 8% to about 10% silicon, about 2.5 to about 4.5% copper, up to about 1% magnesium, with balance essentially aluminum. For making sole plates by permanent mold casting, it is advantageous that the alloy of the plate contain about 5% to about 13% nickel, about 3% to about 5% silicon, about 9% to about 11% copper, up to about 1.5% magnesium, with balance essentially aluminum. All alloy percentages herein are by Weight.

Where it is desired to obtain advantageous corrosion resistant characteristics of copper-free, or substantially copper-free, aluminum-nickel-silicon alloys and the hardening effect of copper is not needed, die cast or permanent mold cast hot plates for frying pans, skillets and electric irons, especially electric steam irons, are advantageously made of a copper-free aluminum-nickel-silicon alloy containing about 5% to about 13% nickel, about 8% to about 10% silicon, not more than about 0.6% copper, advantageously not more than 0.3% copper, up to about 1% magnesium, with balance essentially aluminum. Alloys containing more than about 0.6% but less than about 2.5% copper are not advantageous for hot plates of the invention inasmuch as such alloys do not have the corrosion resistant advantages of copper-free aluminum alloys or the hardness advantages imparted by the presence of about 2.5 or more copper.

The hot plate of the invention has especially good characteristics of resistance to surface damage and marring, including high scratch resistance in combination with especially high resistance to indentation, when made of a new, high-nickel, aluminum alloy provided by the invention, which alloy contains about 9% to about 15% nickel, about 2% to about 12% silicon and about 2.5% to about 14% copper with the total of the percentage of silicon plus the percentage of copper equal to about 9.5 to about 17%, up to about 1.5% magnesium, with balance essentially aluminum. The new, high-nickel, aluminum alloy of the invention is characterized in the chillcast condition and, also, in the condition obtained by heating the alloy in the chill-cast condition at temperatures up to 600 F. for up to about 120 hours by hardness at 600 F. of at least about Rockwell H. In the chill-cast condition the alloy of the invention has improved high resistance to particular kinds of scratching of the nature commonly encountered by sole plates on electric irons, as further pointed out hereinafter.

An embodiment of the new, high-nickel, aluminum alloy which is particularly advantageous for die casting contains about 9% to about 13% nickel, about 8% to about 10% silicon, about 2.5% to about 4.5% copper, up to about 1% magnesium, with balance essentially aluminum. For. making castings by permanent molding, the invention provides an advantageous embodiment of the new, high-nickel, aluminum alloy which contains about 9% to about 13% nickel, about 3% to about 5% silicon,

about 9% to about 11% copper, up to about 1.5% magnesium, with balance essentially aluminum.

Where the balance of an alloy is referred to herein as essentially aluminum, it is to be understood that balance essentially aluminum does not exclude small amounts of other elements which can be present as impurities without substantial detrimental effects or which can serve some useful purpose ancillary to the invention. Thus, the aluminum-nickel alloy of a hot plate in accordance with the invention can contain up to about 0.5% titanium and/or up to about 0.5% boron for grain refinement, small amounts of cadmium and/ or lithium effective to improve aging characteristics and/or a small amount of sodium, e.g., about 0.1% sodium. Iron is commonly present as an impurity in commercial aluminum alloys and can be present in the alloy of a sole plate of the invention, but the amount of iron therein should not be greater than about 2.5%, preferably not greater than 1%, in order to avoid detrimental effects of iron on the toughness of the alloy. Also, the balance of the alloy may contain up to about 1.5% manganese and up to about 3% zinc. In any event, the total amount of elements other than nickel, silicon, copper, magnesium and aluminum in the alloy of a hot plate in accordance with the invention is not greater than about 5%.

Electric iron sole plates and other hot plates in accordance with the invention can be cast by known techniques for die casting or permanent mold casting aluminum alloys or can be cast by other techniques, such as sand casting, provided the working surface of the plate is chilled to produce a chill-cast microstructure. The spe cial aluminum-nickel alloy for plates of the invention can be made by melting together, in accordance with melting practices known for production of high quality aluminum alloys, appropriate quantities of alloy ingredients, e.g., aluminum pig, elemental metals or aluminum master alloys containing silicon or copper, such as are commercially used for producing high quality aluminum alloys. In adding nickel to an aluminum alloy melt, it is advantageous to add the nickel as an aluminum-nickel master alloy, e.g., an aluminum alloy containing 20% nickel, in order to obtain rapid and uniform distribution of the nickel in the melt. Heating elements and/or other components of electric irons can be cast-in-place and thus integrally bonded-by-casting to sole plates of the invention but are understood not to be portions, component, etc., of a sole plate. Heating elements can also be pressed or brazed on hot plates of the invention. However, it is important not to anneal, or otherwise soften by heat treatment, the chill-cast working surface of the hot plate in order to avoid loss of resistance to deformation and/ or scratching. For instance, the chill-cast surface of the plate must not be heated to a temperature of about 750 F. or higher and slowly cooled. It is necessary that the hot plate of the invention have a fine grain structure, such as is obtained by chill-casting, in order to obtain good retention of hardness after prolonged heating. Poor retention of hardness has been found where an aluminumnickel alloy of composition in accordance with the special composition of the invention was of a coarse microstructure.

Referring now to the drawing, FIGURES 1 and 2 depict an electric iron sole plate which is illustrative of the hot plate of the present invention. The sole plate has an ironing (working) surface 11 and recess 12 wherein electric heating elements (not shown) can be embedded to supply heat to heated surface 13. The illustrative sole plate is made of an aluminum-nickel alloy 14, e.g., 11% nickel, 4% silicon, 10% copper, 0.3% magnesium, with balances essentially aluminum, of composition in accordance with the invention and has a chill-cast microstructure throughout portion 15 at the working surface of the plate. Although the plate illustrated in the drawing is a solid plate having an uninterrupted working surface, the invention also includes solo plates having steam exhaust ports in the working surfaces thereof and passages for conducting steam to the exhaust ports.

For the purpose of giving those skilled in the art a better understanding of the invention and/ or a better appreciation of the advantages of the invention, the following illustrative examples are given:

EXAMPLE I A high-nickel, aluminum alloy containing about 11% nickel, 4.2% silicon, 10% copper, 0.4% magnesium, 0.4% iron, 0.2% titanium with balance essentially aluminum is cast in a cast iron permanent mold to the configuration of an electric iron sole plate. Electric heating elements are embedded in the sole plate when the alloy thereof is cast. The sole plate is machined, polished and assembled into an electric iron. In the as-cast condition the sole plate has high resistance to deformation with a Rockwell H hardness of 117 and a Brinell hardness of 141 and high scratch resistance at room temperature on a chill-cast surface. The electric iron with the sole plate in accordance with the invention is used for ironing and is found entirely satisfactory therefor. While in use, the sole plate is heated to temperatures of 250 F. to 450 F. in normal operation, with occasional overshoots up to 600 F., and has good resistance to indentation and scratching by forceful contact with dressmaking pins, snaps, zippers, etc. After being in use for a total of 120 hours, with intermittent cooling, the sole plate surface has retained high resistance to deformation and scratch resistance and has a Rockwell H hardness of about at 600 F.

EXAMPLE II polished and assembled into an electric iron. In the ascast condition the sole plate has high resistance to deformation with a Rockwell H hardness of at least about 113 and a Brinell hardness of about 111 and high scratch resistance at room temperature on a chill-cast surface. The electric iron with the sole plate in accordance with the invention is used for ironing and is found entirely satisfactory therefor. While in use, the sole plate is heated to temperatures of 250 F. to 450 F. in normal operation, with occasional overshoots up to 600 F., and has good resistance to indentation and scratching by forceful contact with dressmaking pins, snaps, zippers, etc. After being in use for a total of hours, with intermittent cooling, the sole plate surface has retained high resistance to deformation and scratch resistance and has a Rockwell H hardness of at least about 82 at 600 F.

Aluminum-nickel alloys having chemical compositions of Alloys Nos. 1 through 6 set forth in Table I hereinafter, which compositions are illustrative of the special aluminum-nickel alloy of which the hot plate of the invention is made, were induction melted, treated by standard commercial degassing techniques as appropriate and cast at about 1300 F. to 1350 F. in permanent molds (chill molds). Alloys Nos. 4 and 5 are examples of the scratch-resistant high-nickel, aluminum alloy of the invention. To further illustrate the advantages of the present invention, three substantially nickel-free alloys having the compositions of Alloys A, B and C set forth in Table I and not in accordance with the special aluminum-nickel alloy composition of hot plates of the invention were also cast in permanent molds by the same melting and casting techniques employed for making permanent mold castings of Alloys Nos. 1 through 6.

TABLE I Alloy Ni, Si, Cu, Mg, Fe, Ti, Aluminum No. percent percent percent percent percent percent 6. 7 4 10. 0.2 0. 3 0.2 Balance. 0. s 8.9 3.8 Nil 0. 3 0. 2 Do. 7 9 Nil 1 0.2 0.2 Do. 11 4. 2 10. 1 0. 4 0.4 0. 2 Do. 10. 9 s. 5 3. 7 Nil 0. 4 0. 2 Do. 11. 3 9 Nil 1.1 0. 4 0. 2 D0. Nil 4 9. 4 0. 3 0. 5 0. 2 D0. Nil 8.6 4. 2 Nil 0. 3 0. 2 Do. Nil 9. 1 Nil 1 0. 4 0. 2 Do.

Nil Not more than 0.05%.

Hardness test results which were obtained by testing which are also set forth in Table III. It is also noted that chill-cast surfaces of Alloys Nos. 1 through 6 and which comparisons of results set forth in Tables II and III, illustrate the high resistance to deformation of chill-cast taken in conjunction with chemical compositions set forth working surfaces of hot plates in accordance with the inin Table I, show that scratch resistance is not directly provention in the as-cast condition, at elevated temperature, portlonal or predictably related to the hardness of the and after prolonged exposure to elevated temperatures are alloys. set forth in Table II. In addition, Table II shows results TABLF m of hardness tests of Alloys A, B and C.

TABLE II Average Depth of Scratches in Microinclles Alloy No. Tested At Room Temperature Tested at 400 F., At Room 'lemperature At 400 F At 00 F 3 Load i v 1 Alloy After 24 After 24 After 24 After 24 f qi g 55%? 3 N0. As-Cast hrs. at hrs. at hrs. at hrs. at 3 1b L033 400 F., 600 F, 400 F 600 F.,

RF RH RF RH RF RH 590 765 103 115 102 10s 91 80 94 100 02 106 76 73 510 80 105 32 100 59 56 590 105 117 105 Y 114 07 92 600 100 113 100 111 s5 82 730 90 100 02 105 73 71 880 95 112 97 102 79 53 32 102 84 9s 57 34 74 99 74 89 44 23 Microinch=10- inch.

RI -Rockwell F Hardness (1/16 diameter ball, 60 kilograms load). RH-Rockwell H Hardness (1 8 diameter ball, 00 kilograms load).

Scratch resistance referred to herein is resistance to scratching by sharp portions, including points, corners, edges, etc., on articles of visible size such as on dressmakers pins, snaps, buttons, zippers and other objects which are sometimes attached to clothing, curtains and other cloth articles which are ironed. Scratching and also indentation referred to herein not only results from contact with articles encountered in ironing but also from contact with pins, nails, tacks, screws, corners or edges of metal or glass counter tops, metal moldings, or decor and other objects which may be present where an electric iron is stored or exhibited for sale. Scratch resistance of the nature referred to herein was tested by using commercially sold dressmakers pins as points and moving the pinpoints under loads of 1.2 pounds and 3.0 pounds (an ordinary weight of an electric iron) over chill-cast surfaces of Alloys Nos. 1 through 6 and Alloys A, B and C at room temperature and also with the chill-cast surfaces at elevated temperatures. Resistance to scratching was evaluated by measuring depths of scratches. It was found that the extent of burring and undesirability of appearance increased with the depth of scratch. To insure good test results, a new pin was used for each test and results of a number of tests were averaged. The high scratch resistance of chill-cast surfaces of the new, highnickel, aluminum-silicon-copper alloy, containing about 9% to about 15% nickel, advantageously about 9% to 13% nickel for good castability, which is provided by the invention, is illustrated by scratch test results pertaining to Alloys Nos. 4 and 5 as set forth in Table III. Advantages of scratch resistance which flow from having a high nickel content of about 11% with copper copresent in amounts within the range of about 2.5% to 11%, or 2.5% to 14%, are further illustrated by comparison of scratch test results on Alloys Nos. 4 and 5 with results of scratch tests on Alloys Nos. 1, 2, 3, 6, A, B, and C The results set forth in Table III show that Alloys Nos. 4 and 5 are characterized by high scratch resistance on chill-cast, polished surfaces thereof at room temperature in the as-cast condition and after being heated at 400 F. for a prolonged period of 24 hours and also when tested at an elevated temperature of about 400 F. In addition, Table III shows that Alloys Nos. 1, 2, 3, 6, A, B and C do not possess the high scratch resistance of Alloys Nos. 4 and 5. It is also pointed out that Alloy No. 4, which contains about 11% nickel, 4% silicon, 10% copper, about 0.3% to about 0.6% magnesium and balance essentially aluminum, possesses markedly superior scratch resistance and it is especially advantageous that hot plate articles requiring high resistance to deformation and scratching be made of an alloy composition which, as contemplated by the invention, contains 9% to 13% nickel, about 3% to about 5% silicon, about 9% to about 11% copper, about 0.2% to about 0.8% magnesium, with balance essentially aluminum.

Advantages of good castability including high fluidity are achieved by restricting the nickel content of the alloy to not more than 13%. Magnesium in amounts of about 0.2% to about 0.8% is advantageous for obtaining highest hardness in aluminum alloys set forth herein; however, in order that the alloy have good fluidity, the magnesium content should not be more than about 1%. An advantageous combination of characteristics including good castability with high fluidity and also high resistance to deformation and high scratch resistance when in the chill-cast condition is obtained with an alloy composition containing 9% to 13% nickel, about 2% to about 12% silicon and about 2.5 to about 14% copper with a total percentage of silicon plus copper of about 7% to about 17%, up to about 1% magnesium, with balance essentially aluminum which is contemplated within the invention. In all embodiments of the present invention, the sum of the percentages of silicon and copper must be at least about 7%, advantageously at least about 9.5%, in

order to have necessary hardness and is maintained not greater than about 17% in order to insure good toughness and to avoid embrittlement of the alloy.

Aluminum-nickel hot plates in accordance with the invention are particularly useful in electrically heated kitchenware including irons, frying pans, skillets, pancake griddles, food warmers and other electrically heated kitchenware appliances. The hot plate of the invention is especially advantageous for use as the sole plate of an electric iron inasmuch as electric irons are usually and very frequently set down on the ironing surface and subjected to possible damage by indentation or scratching when being exhibited for sale and also when in storage or in use. The high-nickel, aluminum-silicon-copper alloy of the invention is particularly useful for making scratchresistant hot plates and is also useful for making other aluminum-alloy articles which need or require high hardness at room temperature and elevated temperature, good retention of hardness after being heated to elevated temperatures and/ or high scratch resistance, e.g., brake drums or shoes, pulleys, sheaves, pots, pans, egg beaters, mixing bowls and the like.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

We claim:

1. A kitchenware hot-plate appliance having an electric heating element wherein the improvement comprises the combination with said heating element of an aluminum-base alloy hot plate consisting essentially of to about 15% nickel, about 2% to about 12% silicon and up to about 14% copper with the total percentage of silicon plus copper being about 7 to about 17, up to about 1.5% magnesium with the balance essentially aluminum and having a substantially flat working surface with a chill cast microstructure characterized by small intermetallic particle size, fine grain size and small dendrite cell size extending at least inward from said surface.

2. An electric iron appliance in accordance with claim 1 wherein the sole plate of the iron is a cast aluminumbase alloy hot plate as set forth in claim 1.

3. An electrically heated skillet appliance in accordance with claim 1 wherein the cooking plate is a cast aluminum-base alloy hot plate in accordance with claim 1.

4. A cast kitchenware hot plate of a structure adapted to be electrically heated from one surface and having in addition a substantially flat working surface, said plate being composed of an aluminum-base alloy consisting essentially of 5% to about 15% nickel, about 2% to about 12% silicon and up to about 14% copper with the total percentage of silicon plus copper being about 7 to about 17, up to about 1.5% magnesium, with the balance essentially aluminum and having at said working surface a chill cast microstructure characterized by small intermetallic particle size, fine grain size and small dendrite cell size and extending at least inward from said surface.

5. An electric iron sole plate in accordance with the hot plate set forth in claim 4.

6. An electric skillet cooking plate in accordance with the hot plate set forth in claim 4.

7. A hot plate in accordance with claim 4 wherein the aluminum-base alloy contains 5% to about 15% nickel, about 3% to about 12% silicon and about 2.5% to about 14% copper with the total of silicon plus copper equal to about 9.5% to about 17% of the alloy, up to about 1.5% magnesium, with the balance consisting essentially of aluminum and wherein the chill cast surface is further characterized at temperatures up to 600 F. by hardness of at least about Rockwell H that is retained when said plate is heated at temperatures up to 600 F. for prolonged periods up to 24 hours.

8. A hot plate in accordance with claim 4 wherein the aluminum-base alloy contains 9% to about 15% nickel, about 2% to about 12% silicon and about 2.5 to about 14% copper with the total of silicon plus copper equal to about 9.5% to about 17% of the alloy, up to about 1.5 magnesium, with the balance essentially aluminum and wherein the chill cast surface is further characterized at temperatures up to 600 F. by hardness of at least Rockwell H that is retained when said plate is heated at 600 F. for prolonged periods up to about 24 hours.

9. In a process for making an electrically heated article of kitchenware wherein an electric heating element and a cast hot plate are combined, the combination with said steps of casting the hot plate of an aluminum-base alloy consisting essentially of 5% to about 15 nickel, about 2% to about 12% silicon and up to about 14% copper with the total of silicon plus copper being about 7% to about 17% of the alloy, up to about 1.5% magnesium with the balance essentially aluminum and chilling a surface of said plate to produce at said surface a chill cast microstructure characterized by small intermetallic particle size, fine grain size and small dendrite cell size.

10. An alloy consisting essentially of 9% to about 15 nickel, about 2% to about 12% silicon, about 2.5% to about 14% copper with the total of silicon plus copper equal to about 9.5% to about 17 of the alloy, up to about 1.5 magnesium, with the balance essentially aluminum.

11. An alloy as set forth in claim 10 containing 9% to 13% nickel, 8% to 10% silicon, 2.5% to 4.5% copper, up to 1% magnesium, with the balance essentially aluminum.

12. An alloy as set forth in claim 10 containing 9% to 13% nickel, 3% to 5% silicon, 9% to 11% copper, up to 1% magnesium, with the balance essentially aluminum.

References Cited UNITED STATES PATENTS 1,449,052 3/1923 Pack 75-144 1,799,837 4/1931 Archer et al. 75143 1,920,233 8/1933 Archer et al. 75143 1,920,262 8/1933 Kempf et al. 75143 DAVID L. RECK, Primary Examiner.

R. O. DEAN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,333 ,955 August 1 1967 Lancelot H. Walker et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 26, for "sufrace" read surface column 5, line 75, for "solo" read sole column 8, TABLE III, firs column, line 8 thereof, for "C" read B same table, first column, line 9 thereof, for "B" read C Signed and sealed this 20th day of August 1968.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

10. AN ALLOY CONSISTING ESSENTIALLY OF 9% TO ABOUT 15% NICKEL, ABOUT 2% TO ABOUT 12% SILICON, ABOUT 2.5% TO ABOUT 14% COPPER WITH THE TOTAL OF SILICON PLUS COPPER EQUAL TO ABOUT 9.5% TO ABOUT 17% OF THE ALLOY, UP TO ABOUT 1.5% MAGNESIUM, WITH THE BALANCE ESSENTIALLY ALUMINUM.