US3893823A

US3893823A - Cladding system

Info

Publication number: US3893823A
Application number: US474883A
Authority: US
Inventors: Thomas E Webb
Original assignee: Reynolds Metals Co
Current assignee: Reynolds Metals Co
Priority date: 1972-12-18
Filing date: 1974-05-31
Publication date: 1975-07-08
Anticipated expiration: 1992-07-08

Abstract

A composite sheet product, suitable for porcelain enameling, having an aluminous metal cladding layer on an aluminum base core alloy containing about 2 to 3% copper, up to about 0.4% manganese, and about 0.2 to 0.6% magnesium.

Description

United States Patent [1 1 Webb [ CLADDING SYSTEM [75] Inventor: Thomas E. Webb, Richmond, Va.

[73] Assignee: Reynolds Metals Company,

Richmond, Va.

[ Notice: The portion of the term of this patent subsequent to Nov. 26, 1991, has been disclaimed.

[22] Filed: May 31, 1974 [21] Appl. No.: 474,883

Related U.S. Application Data [60] Division of Ser. No. 316,177, Dec. 18, 1972, Pat. No. 3,850,585, which is a continuation of Ser. No. 78,276, Oct. 5, 1970, abandoned.

[52] U.S. C1 29/195; 29/1975; 117/70 C; 117/71 M; 117/75 [51] Int. Cl. B32b 15/20; A47j 27/00 [58] Field of Search 29/1975, 195 PV; 220/64; 117/70 L, 71 M, 78

145] *July 8, 1975 Primary Examiner-L. Dewayne Rutledge Assistant Examiner-Arthur J. Steiner Attorney, Agent, or Fz'rmGlenn, Palmer, Lyne & Gibbs [57] ABSTRACT A composite sheet product, suitable for porcelain enameling, having an aluminous metal cladding layer on an aluminum base core alloy containing about 2 to 3% copper, up to about 0.4% manganese, and about 0.2 to 0.6% magnesium.

13 Claims, No Drawings CLADDING SYSTEM This application is a division of copending application Ser. No. 316,177 filed on Dec. 18, 1972, now US. Pat. No. 3,850,585, which is a continuation of application Ser. No. 78,276 filed on Oct. 5, l970, now aban doned.

The present invention relates to a composite aluminous metal article, typically in sheet form, having an outer cladding layer suitable for porcelain enameling and an adjoining core layer which is susceptible to strengthening under thermal conditions incident to porcelainizing treatment. The composite is adapted for such uses as making coated aluminum utensils, including those having an interior non-stick coating, and the core and cladding layers are selected to provide improved resistance to exfoliation and blistering.

BACKGROUND OF THE INVENTION Aluminum utensils are commonly provided with a TFE coating on their interior cooking surfaces. Porcelain enameling is used to finish the exterior surfaces of these and other products made of clad composites. The aluminous materials used for such purposes may be a commercial grade of aluminum (lXXX series) or a high aluminum content alloy such as 3003, either alone or as cladding on a stronger base alloy providing greater rigidity. Two such clad composites previously used are 3003 clad 7005-type alloy and H clad 7004-type alloy.

In these applications a cladding of l 100 or 3003 aluminum has been selected primarily on the basis of its suitability for porcelainizing or TFE coating operations, while the 7004 and 7005 type alloys have been chosen for their responsiveness to strengthening under thermal conditions incident to such operations. It has been found that the resulting combinations are less than ideal, however, because these cladding materials are not sufficiently anodic to such core alloys to provide electrolytic protection. Thus, in the event of a scratch or other discontinuity which allows access of corrosive food constituents or water and other sub stances used for cleaning purposes, a form of corrosion may occur which tends to spread laterally along and through the core layer, resulting in exfoliation and blistering.

An object of the present invention is to provide an alclad composite exhibiting improved resistance against such attack, while still employing conventional cladding materials adapted for porcelain enameling.

SUMMARY OF THE INVENTION It has been found that an alclad copper-bearing aluminum base core alloy provides improved results with respect to corrosion resistance of the composite, in that such an alloy serves to limit attack to minor pitting of a localized nature. In accordance with the invention, the cladding layer is bonded to a base layer of an alloy consisting essentially of aluminum, about 2 to 3% copper, up to about 0.4% manganese, and about 0.2 to 0.6% magnesium by weight. This alloy may also contain the usual incidental impurities as well as minor alloying elements in customary amounts for recognized purposes, including, for example, up to about 0.8% silicon, 0.7% iron, 0.1% chromium, 0.25% zinc and 0.2% titanium.

The cladding may be applied on one or both surfaces of the base layer. A preferred cladding alloy is 3003,

but other conventional aluminous metal cladding materials are suitable, such as aluminum and high aluminum content alloys capable of affording electrolytic protection, particularly those selected from the group consisting of type lXXX aluminum of at least 99.0% purity and alloys of the 3XXX series (Aluminum Association designation) containing up to about 1.5% manganese as the principal alloying element by weight.

EXAMPLE The following example illustrates the practice of the invention and its presently preferred embodiment:

An ingot was prepared having a core composed of a copper-bearing aluminum base alloy and having 3003 alloy cladding l07r) on both sides. then rolled to 0.102 inch gage, blanked into suitable circles, and subjected to thermal treatment to simulate porcclainizing and TFE coating cycles. The core composition (alloy X2036) in weight percentages was:

0.50 max. Si

0.50 max. Fe

0.10 max. Cr

0.25 max. Zn

0.15 max. Ti

Others, each .05 max. total 0.15 max.

Balance aluminum.

For purposes of comparison, reference specimens were prepared from conventional 3003 clad 7005-type alloy. Exfoliation tests (5-day MASTMAASIS standard) were performed on annealed materials, and also on those treated for 10 minutes at l,000F. and fan cooled (to simulate porcelaining) and for 15 minutes at 750F. and air cooled (to simulate TFE coating).

The conventional materials showed moderate to severe blistering both in annealed and heat treated condition.

a In contrast, the composite matrials of the present invention showed only slight pitting (no blistering or exfoliation attack) in either condition.

A clad product of this sort is known commercially as Type 36 porcelain enameling sheet." its core alloy X2036 was registered with the US. Aluminum Association on Aug. I3, 1970, by the assignee of this application.

Alclad X2036 alloy in the form of such porcelain enameling sheet (PE-36) is suitable for conventional fabricating operations incident to making various types of cooking utensils, particularly pans and the like having a TFE non-stick coating or a porcelain enamel coating, or both, and such coatings are readily applied to a cladding surface of the composite sheet. The invention embraces the clad product itself, its use in making cooking utensils, and related method aspects of making such products and applying such coatings.

The term alclad is used here in the accepted sense to indicate a bonded composite having a layer of aluminum or corrosion-resistant aluminum alloy which is anodic to the core of structurally stronger aluminum alloy it covers, thus physically and electrolytically protecting the core alloy against corrosion.

What is claimed is:

1. In the art of making porcelain enameling sheet having a cladding layer of aluminous metal selected from the group consisting of type [XXX aluminum of at least 99.0% purity and aluminum base alloys ofthe BXXX series containing up to about 1.5% manganese by weight, the improvement which comprises bonding said cladding to a core of aluminum base alloy consisting essentially of aluminum, 2.2 to 3.0% copper, 0.3 to 0.6% magnesium and 0. ID to 0.40% manganese by weight.

2. in the art of making cooking utensils having a TFE coating, the improvement which comprises applying said coating on an exterior cladding surface of a composite sheet having a core of aluminum base alloy consisting essentially of aluminum, 2.2 to 3.0% copper, 0.3 to 0.6% magnesium and 0.l to 0.40% manganese by weight and a cladding layer of aluminous metal selected from the group consistingof type IXXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series containing up to about 1.5% manganese by weight.

3. in the art of making cooking utensils from composite sheet material having a cladding of aluminous metal selected from the group consisting of type lXXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series containing up to about l.5% manganese by weight and a core layer of a higher strength aluminum base alloy, the improvement which comprises providing composite sheet material having a core of aluminum base alloy consisting essentially of aluminum, 2.2 to 3.0% copper, 0.3 to 0.6% magnesium and 0.l0 to 0.40% manganese by weight and a layer of said cladding on each side of the core, applying a TFE coating on a cladding surface at one side of said sheet, and applying a porcelain enamel coating on a cladding surface at the other side of said sheet.

4. A clad composite article having an aluminum base alloy core consisting essentially of aluminum, 2.2 to 3.0% copper, 0.3 to 0.6% magnesium and 0.lO-0.40% manganese by weight; and having a cladding of aluminous metal selected from the group consisting of type lXXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series containing up to about 1.5% manganese by weight, said cladding being anodic to said core alloy and effective cooperatively therewith to avoid exfoliation and blistering.

5. An article made of sheet according to claim 4, having a TEE coating on a cladding surface of said sheet.

6. An article made of sheet according to claim 4, having a porcelain enamel coating on a cladding surface of said sheet.

7. An article made of sheet according to claim 4, wherein said sheet is clad on both sides, said article 4 having a porcelain enamel coating on a cladding surface at one side of said sheet and TFE coating on a cladding surface at the other side of said sheet.

8. An article comprising a clad composite suitable for porcelain enameling, having a cladding layer of aluminous metal selected from the group consisting of type lXXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series containing up to about 1.5% manganese by weight, and an adjoining core layer of an alloy consisting essentially of aluminum, about 2 to 3% copper, up to about 0.4% manganese and about 0.2 to 0.6% magnesium. by weight, with incidental elements and impurities not exceeding 0.8% silicon, 0.7% iron, 0.l% chromium, 0.25% zinc and 0.2% titanium.

9. The article of claim 8 wherein said core alloy contains about 0.l00.40% manganese, about 0.30-0.6% magnesium and about 22-30% copper.

[0. The article of claim 9 wherein said core alloy includes incidental amounts of silicon and iron not exceeding 0.5% each. 7

11. The article of claim 10 in the form of sheet.

12. The article of claim 8 in the form ofsheet, having a layer of said cladding on each side of the sheet.

13. In an article of the type having an outer cladding layer suitable for porcelain enameling and TFE coating operations, and an adjoining core layer of a higher strength aluminum base alloy, the improvement wherein:

a. said core layer is composed of an alloy consisting essentially of aluminum, about 2 to 3% copper, up to about 0.4% manganese and about 0.2 to 0.6%

magnesium, by weight, with incidental ,elements and impurities not exceeding 0.8% silicon, 0.7% iron, 01% chromium, 0.25% zinc and 0 .2% tita nium;

b. said cladding layer being composed of aluminous metal selected from the group consisting of type lXXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series effective to provide electrolytic protection of the core;

0. said cladding and core in combination affording a composite article adapted for porcelainizing treat ment at l,000F.;

d. said article being further characterized by the responsiveness of its core alloy to strengthening under thermal conditions incident to such treatment and by the effectiveness of said composite in avoiding exfoliation and blistering.

Claims

1. IN THE ART OF MAKING PORCELAIN ENAMELING SHEET HAVING A CLADDING LAYER OF ALUMINOUS METAL SELECTED FROM THE GROUP CONSISTING OF TYPE 1XXX ALUMINUM OF AT LEAST 99.0% PURITY AND ALUMINUM BASE ALLOYS OF THE 3XXX SERIES CONTAINING UP TO ABOUT 1.5% MANGANESE BY WEIGHT THE IMPROVEMENT WHICH COMPRISES BONDING SAID CLADDING TO A CORE OF ALUMINUM BASE ALLOY CONSISTING ESSENTIALLY OF ALUMINUM, 2.2 TO 3.0% COPPER, 0.3 TO 0.6% MAGNESIUM AND 0.10 TO 0.40% MANGANESE BY WEIGHT.

2. In the art of making cooking utensils having a TFE coating, the improvement which comprises applyiNg said coating on an exterior cladding surface of a composite sheet having a core of aluminum base alloy consisting essentially of aluminum, 2.2 to 3.0% copper, 0.3 to 0.6% magnesium and 0.10 to 0.40% manganese by weight and a cladding layer of aluminous metal selected from the group consisting of type 1XXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series containing up to about 1.5% manganese by weight.

3. In the art of making cooking utensils from composite sheet material having a cladding of aluminous metal selected from the group consisting of type 1XXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series containing up to about 1.5% manganese by weight and a core layer of a higher strength aluminum base alloy, the improvement which comprises providing composite sheet material having a core of aluminum base alloy consisting essentially of aluminum, 2.2 to 3.0% copper, 0.3 to 0.6% magnesium and 0.10 to 0.40% manganese by weight and a layer of said cladding on each side of the core, applying a TFE coating on a cladding surface at one side of said sheet, and applying a porcelain enamel coating on a cladding surface at the other side of said sheet.

4. A clad composite article having an aluminum base alloy core consisting essentially of aluminum, 2.2 to 3.0% copper, 0.3 to 0.6% magnesium and 0.10-0.40% manganese by weight; and having a cladding of aluminous metal selected from the group consisting of type 1XXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series containing up to about 1.5% manganese by weight, said cladding being anodic to said core alloy and effective cooperatively therewith to avoid exfoliation and blistering.

5. An article made of sheet according to claim 4, having a TFE coating on a cladding surface of said sheet.

7. An article made of sheet according to claim 4, wherein said sheet is clad on both sides, said article having a porcelain enamel coating on a cladding surface at one side of said sheet and a TFE coating on a cladding surface at the other side of said sheet.

8. An article comprising a clad composite suitable for porcelain enameling, having a cladding layer of aluminous metal selected from the group consisting of type 1XXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series containing up to about 1.5% manganese by weight, and an adjoining core layer of an alloy consisting essentially of aluminum, about 2 to 3% copper, up to about 0.4% manganese and about 0.2 to 0.6% magnesium, by weight, with incidental elements and impurities not exceeding 0.8% silicon, 0.7% iron, 0.1% chromium, 0.25% zinc and 0.2% titanium.

9. The article of claim 8 wherein said core alloy contains about 0.10-0.40% manganese, about 0.30-0.6% magnesium and about 2.2-3.0% copper.

10. The article of claim 9 wherein said core alloy includes incidental amounts of silicon and iron not exceeding 0.5% each.

11. The article of claim 10 in the form of sheet.

12. The article of claim 8 in the form of sheet, having a layer of said cladding on each side of the sheet.

13. In an article of the type having an outer cladding layer suitable for porcelain enameling and TFE coating operations, and an adjoining core layer of a higher strength aluminum base alloy, the improvement wherein: a. said core layer is composed of an alloy consisting essentially of aluminum, about 2 to 3% copper, up to about 0.4% manganese and about 0.2 to 0.6% magnesium, by weight, with incidental elements and impurities not exceEding 0.8% silicon, 0.7% iron, 0.1% chromium, 0.25% zinc and 0.2% titanium; b. said cladding layer being composed of aluminous metal selected from the group consisting of type 1XXX aluminum of at least 99.0% purity and aluminum base alloys of the 3XXX series effective to provide electrolytic protection of the core; c. said cladding and core in combination affording a composite article adapted for porcelainizing treatment at 1,000*F.; d. said article being further characterized by the responsiveness of its core alloy to strengthening under thermal conditions incident to such treatment and by the effectiveness of said composite in avoiding exfoliation and blistering.