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Publication numberUS3118223 A
Publication typeGrant
Publication dateJan 21, 1964
Filing dateMar 29, 1960
Publication numberUS 3118223 A, US 3118223A, US-A-3118223, US3118223 A, US3118223A
InventorsWilhelm Sciiull
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
High strength aluminum coated steel
US 3118223 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

United States Patent 3,118,223 HEGH STRENGTH ALUMEJUM OUATED STEEL Wilhelm Schiill, Cologne-Dellbruck, and Clemens Eisenhnth, Cologne-Holweide, Germany, assignors to Amer can Chain & Cable Company, Inc, a corporation of New York No Drawing. Filed Mar. 29, 1960, Ser. No. 18,226 Claims priority, application Germany Apr. 9, 1959 Claims. (Cl. 29-528) This invention relates to aluminum coated steel, and is particularly directed to the provision of an improved method for producing aluminum coated steel or" high tensile strength. It is a particular object of the invention to produce high strength aluminum coated steel wire by a process which involves dipping the wire (or other shape) in molten aluminum to form the aluminum coating thereon. Satisfactory processes and equipment that can be used for hot dip aluminizing of wire have only recently been developed. Good coatings are formed by these processes, but with the limitation that the strength of the steel wire does not exceed about 170,000 lbs/sq. in. The production of aluminized steel wire of greater strengths is not possible by the processes heretofore proposed, for during aluminizing the strength of the Wire is considerably reduced because of the high melting point of the aluminum bath. it has been attempted to counteract this wire strength loss by a subsequent drawing operation. This, however, has been only partly successful, as the aluminized steel wire is not structurally adapted to the extensive cold working necessary for developing a really high tensile strength (e.g., above 175,000 lbs/sq. in.). Thus, it has not been possible, by the processes presently known, to produce aluminized steel wire of greater strength than 170,000 lbs/sq. in.

Efforts also have been made to lessen the loss of strength accompanying the aluminizing of steel wire by keeping the temperature of the coating bath as low as possible through the addition of suitable metals, but important improvements have not yet been obtained by this approach.

This invention provides for the production or aluminized steel wire of high strength by passing the cleaned wire through a molten aluminum coating bath and drawing it in the same process. The invention departs, however, from procedures heretofore used in that the temperature of the bath is raised to above the values heretofore employed and is controlled in accordance with the carbon content of the wire passing through, so that the utmost possible alteration in the wire to an austenitic structure results.

Thus, in carrying out the new method, the bath of molten aluminum is heated to above the Ac point of the wire or other steel shape to be coated. The wire (or other shape) then is immersed in such bath, and is retained therein long enough to be heated to above its AC3 temperature. Thus, upon withdrawal of the steel wire or other shape from the molten aluminum, it is in the substantially fully austenitic condition. It is cooled in air substantially to room temperature and thereafter severely worked to develop the desired high tensile strength (above 175,000 lbs/sq. in.).

in order to avoid the necessity of supplying heat to the bath to heat the steel to above its Ac point, the wire or other shape may be preheated in a protective gas atmosphere to a temperature near or above its Ac point. The resulting hot wire then is introduced into the molten aluminum bath. Preheating the wire not only reduces the need for supplying heat to the molten aluminum, but also reduces the time the wire need be held in the molten aluminum bath to be heated to above its Ac transformation point. Indeed, in some cases it is practical and desirable to preheat the wire to above its Ac point and to introduce it at such temperature into the heated molten aluminum. All the heat required to maintain the aluminum bath at the desired temperature may in some cases be supplied in this fashion. Even in such case, however, the molten aluminum must be heated to above the AC3 point of the wire to avoid quenching and hardening it.

The actual temperature to which the molten aluminum must be heated depends of course on the carbon content of the steel wire, for the Ac point depends on carbon content. For example, a steel wire containing 0.5% carbon has an Ac point of about 1435 F.; and a steel wire containing about 0.85% carbon has an Ac point of about 1365 F. The aluminum bath is, in accordance with the invention, heated to above such temperature, depending on the particular steel being aluminum coated.

Wh n the wire is preheated to near or above its Ac point, it should be protected by a non-oxidizing atmosphere to prevent substantial ox dation of its surface prior to its introduction into the molten aluminum. The aluminum coating which adheres to the wire as it is withdrawn from the bath protects it from oxidation, and hence the wire can be allowed to cool in air without suffering any undesirable chemical attacl By means of the method of this invention it is possible to produce aluminum coated high carbon steel wires of very high tensile strength. For example, aluminum coated steel wires containing 0.5 carbon having tensile strengths exceeding 200,000 lbs/sq. in., and similar wires containing 0.85% carbon having tensile strengths substantially exceeding 250,000 lbs/sq. in, can readily be produced. Steel wires or" such strength, and possessing a high degree of hardness, are eminently suitable for use as spring wire, in high strength bridge cables and wire ropes, and for other purposes requ ring steel of very high tensile strength. Moreover, these high strength products possess the notable resistan e to corrosion that characterizes aluminum coated articles.

Following is an example of the method of this invention. A steel wire containing 0.85% carbon, 0.102 inch in diameter, was heated in a conventional patenting furnace to a temperature of about 1550 F. The heated wire was rapidly transferred to a bath of molten aluminum maintained at a temperature of about 1370 F. The wire was then withdrawn from the aluminum bath with an adherent aluminum coating and was cooled in air to room temperature. Thereafter, it was cold drawn to a final diameter of 0.039 inch. The drawn wire had a tensile strength of 265,000 lbs/sq. in. and withstood 30 full turns when twisted about its axis over a length of times its diameter.

We claim:

1. The method of producing high strength aluminum coated steel which comprises heating a bath of molten aluminum to a temperature above the Ac point of the steel, immersing the steel in such bath to form an aluminum coating thereon, Withdrawing the steel from the bath in the substantially fully austenitic condition, cooling the steel substantially to room temperature, and severe ly working the cooled aluminum-coated steel to develop therein a high tensde strength.

2. The method of producing high strength aluminum coated steel Wire which comprises heating a bath of molten aluminum to a temperature above the Ac point of the wire, immersing the wire in such bath to form an aluminum coating thereon, withdrawing the wire from the bath in the substantially fully austenitic condition, cooling the wire substantially to room temperature, and severely working the cooled aluminum coated wire to develop therein a high tensile strength.

3. The method of producing high strength aluminum coated steel Wire which comprises heating a bath of molten 52 aluminum to a temperature above the Ac point of the Wire, preheating the Wire to a temperature near its AC3 point, immersing the preheated wire in the molten aluminum and withdrawing it therefrom only after it has attained a temperature above its A0 point and is in substantially the fully austenitic condition, cooling the wire substantially to room temperature, and severely Working the cooled aluminum coated wire to develop therein a high tensile strength.

4. The method of producing iigh strength aluminum coated steel wire Which comprises heating a bath of molten aluminum to a temperature above the A0 point of the wire, preheating the Wire in a protective gas atmosphere to a temperature near its A0 point, immersing the preheated Wire in the molten aluminum and maintaining it therein until it is heated to above its Ac point, withdrawing the wire from the bath in the substantially fully austenitic condition, cooling the wire substantially to room temperature, and severely Working the cooled aluminum coated wire to develop therein a high tensile strength.

5. The method of producing high strength aluminum coated steel wire which comprises heating a bath of molten aluminum to a temperature above the Ac point of the wire, preheating the Wire in a protective gas atmosphere to a temperature above its AC3 point, passing the thusheated Wire through the bath of molten aluminum and withdrawing it therefrom in the substantially fully austenitic condition, cooling the resulting aluminum coated wire in air substantially to room temperature, and thereafter severely working the wire to develop therein a high tensile strength.

References Cited in the tile of this patent UNITED STATES PATENTS 1,409,017 Ortiz Mar. 7, 1922 2,082,622 Fink June 1, 1937 2,191,598 Swartz et al. Feb. 27, 1940 2,455,457 Whitfield et al. Dec 7, 1948 2,543,936 Reynolds Mar. 6, 1951 2,686,355 Lundin Aug. 17, 1954 2,785,084 Lundin Mar. 12, 1957 3,057,050 Hodge et a1. Oct. 9, 1962

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1409017 *Dec 23, 1914Mar 7, 1922Gen ElectricCompound metal body and method of making the same
US2082622 *Mar 14, 1936Jun 1, 1937Colin G FinkDaluminum coated metal and process for producing the same
US2191598 *Nov 5, 1938Feb 27, 1940Cleveland Graphite Bronze CoMethod of bonding dissimilar metals
US2455457 *Jul 24, 1945Dec 7, 1948Fairchild Engine & AirplaneCoated metal article
US2543936 *Sep 22, 1947Mar 6, 1951Julian L ReynoldsApparatus for covering a metallic core with a cast layer of another metal
US2686355 *Jan 19, 1952Aug 17, 1954Lundin Helen MarieProcess for coating metals with aluminum
US2785084 *Dec 13, 1952Mar 12, 1957Birgit WallerCoating ferrous metals with aluminum
US3057050 *Apr 30, 1953Oct 9, 1962Kaiser Aluminium Chem CorpAluminizing of ferrous metal and product
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3224087 *Oct 10, 1962Dec 21, 1965United States Steel CorpMethod of making high-strength aluminum-coated steel wire
US3309906 *Apr 22, 1963Mar 21, 1967Inland Steel CoLight gauge, hot dip metal coated steel products
US3881882 *Apr 19, 1973May 6, 1975Inland Steel CoAluminum coated steel
US4773151 *Aug 6, 1987Sep 27, 1988Dunlop LimitedMethod of making a hose
US4789005 *Mar 14, 1988Dec 6, 1988Dunlop LimitedMarine growth retarding hose
WO2015004597A1 *Jul 8, 2014Jan 15, 2015Prysmian S.P.A.Submarine flexible pipe
Classifications
U.S. Classification72/47, 428/939, 428/653
International ClassificationC23C2/12
Cooperative ClassificationY10S428/939, C23C2/12
European ClassificationC23C2/12