Aluminum coated steel

Claim 2

AN ALUMINUM COATED LOW ALLOY STEEL ARTICLE WHICH HAS GOOD FORMABILITY AND HAS GOOD SUBSURFACE OXIDATION RESISTANCE AND TENSILE PROPERTIES WHEN HEATED AT AN ELEVATED TEMPERATURE IN AN OXIDIZING ATMOSPHERE CONSISTING ESSENTIALLY OF AN ALUMINUM KILLED LOW CARBON STEEL BASE WHICH HAS TITANIUM ADDED TO THE SAID LOW CARBON STEEL AS THE ESSENTIAL ADDED ALLOY ELEMENT WITH THE TITANIUM BEING UNIFORMLY DISTRIBUTED THROUGHOUT THE STEEL IN AN AMOUNT WHICH COMBINES WITH ALL OF THE CARBON AND NITROGEN IN THE STEEL AND PROVIDING AN EXCESS OF BETWEEN ABOUT 0.1 AND ABOUT 0.3 WEIGHT PERCENT OF UNCOMBINED TITANIUM THROUGHOUT THE STEEL, AND A UNIFORM THIN COATING OF METALLIC ALUMINUM DIRECTLY ON A SURFACE OF SAID STEEL BASE WHICH IS FREE OF SURFACE OXIDES AND NON-METALLIC MATERIAL, SAID LOW ALLOY STEEL ARTICLE IN THE AS-COATED CONDITION EHIBITING GOOD FORMABILITY AND WHEN HEATED IN AN OXIDIZING ATMOSPHERE AT AN ELEVATED TEMPERATURE OF 1,500*F EXHIBITING GOOD SUBSURFACE OXIDATION RESISTANCE AND TENSILE PROPERTIES.

Claim 3

The article of claim 1, wherein said steel base is an aluminum killed steel containing from about 0.005 wt. percent to about 0.09 wt. percent aluminum.

Claim 4

The article of claim 1, further characterized in that said steel base is devoid of other added metallic alloying elements in an amount exceeding about 1 percent by weight.

Claim 5

The article of claim 3, wherein said steel base is devoid of other added metallic alloying elements in an amount exceeding about 0.5 percent by weight.

Claim 6

The article of claim 1, wherein the carbon content of said steel base is from about 0.03 wt. percent to about 0.10 wt. percent.

Claim 7

The article of claim 1, wherein said aluminum coating contains up to about 11 wt. percent silicon.

Claim 8

The article of claim 1, wherein said aluminum coating is substantially pure aluminum.

Claim 9

The article of claim 1 further characterized in that upon exposure of said article to an oxidizing atmosphere at an elevated temperature, formation of a substantially continuous subsurface oxide layer in said steel base is avoided and diffusion of aluminum from said coating into said steel base is thereby facilitated.

Claim 10

An aluminum coated low alloy steel article which is resistant to surface and subsurface oxidation and exhibits high tensile properties when heated in an oxidizing atmosphere at an elevated temperature of about 1,500*F, consisting essentially of: an aluminum killed mild steel base containing titanium added thereto in an amount between at least four times and not substantially in excess of about 10 times the amount of carbon in the steel base which effects precipitation of all of the said carbon and nitrogen and provides an excess of between about 0.1 and about 0.3 weight percent of chemically uncombined titanium distributed through the steel; and a metallic aluminum surface coating directly on a clean oxide-free surface of said steel base; said article possessing good formability and on heating in an oxidizing atmosphere at an elevated temperature forming a discontinuous subsurface stratum of discrete particles of oxides below the coating of aluminum, whereby said coating of aluminum diffuses into said steel base without being impeded by a continuous subsurface barrier layer of oxides between the said steel base and said aluminum coating when heated at said elevated temperature.

Claim 11

An aluminum coated low alloy steel article which is resistant to surface and subsurface oxidation and exhibits high tensile properties when heated in an oxidizing atmosphere at an elevated temperature of about 1,500*F, consisting essentially of: an aluminum killed mild steel base containing titanium added thereto in an amount between at least four times and not substantially in excess of about 10 times the amount of carbon in the steel base which effects precipitation of all of the said carbon and nitrogen and provides an excess of between about 0.1 and about 0.3 weight percent of chemically uncombined titanium distributed through the steel; and a metallic aluminum surface coating directly on a clean oxide-free surface of said steel base; said article possessing good formability and on heating in an oxidizing atmosphere at an elevated temperature forming a discontinuous subsurface stratum of discrete particles of oxides below the coating of aluminum, whereby said coating of aluminum diffuses into said steel base without being impeded by a continuous subsurface barrier layer of oxides between the said steel base and said aluminum coating when heated at said elevated temperature.

Claim 12

An aluminum coated steel article as in claim 9, wherein said mild steel base is a low carbon steel containing a maximum of about 0.10 percent by weight carbon.

Claim 15

The method of claim 11, wherein said aluminum coating is applied by immersing said steel base in a bath of molten aluminum.

Claim 16

A corrosion resistant article of manufacture for use in an automotive exhaust system, such as an exhaust muffler, said article being formed from an aluminum coated steel sheet possessing good formability and consisting essentially of an aluminum killed plain carbon steel having a carbon content of up to about 0.25 wt. percent max. and having titanium added thereto as an essential added alloying element in an amount between about four times and about 10 times the carbon content of said steel and which is sufficient to combine with all the carbon and nitrogen in the steel and provide an excess of between about 0.1 and about 0.3 weight percent of uncombined titanium; and an aluminum coating directly on the surface of said steel which is free of oxides and non-metallic material.

Claim 17

A corrosion resistant article of manufacture for use in an automotive exhaust system, such as an exhaust muffler, said article being formed from an aluminum coated steel sheet possessing good formability and consisting essentially of an aluminum killed plain carbon steel having a carbon content of up to about 0.25 wt. percent max. and having titanium added thereto as an essential added alloying element in an amount between about four times and about 10 times the carbon content of said steel and which is sufficient to combine with all the carbon and nitrogen in the steel and provide an excess of between about 0.1 and about 0.3 weight percent of uncombined titanium; and an aluminum coating directly on the surface of said steel which is free of oxides and non-metallic material.

Claim 18

The article of claim 13, wherein said steel is an aluminum killed steel containing from about 0.005 wt. percent to about 0.09 wt. percent aluminum.

Claim 19

An aluminum coated low alLoy steel article as in claim 1, wherein said aluminum killed low carbon steel base in which said titanium is incorporated has a maximum of about 0.25 wt. percent carbon, from about 0.02 to about 0.50 wt. percent manganese, a maximum of about 0.05 wt. percent silicon, and from about 0.005 to about 0.09 wt. percent aluminum.

Claim 22

A method as in claim 16 wherein said steel to which said titanium is added has a maximum of about 0.25 wt. percent carbon, from about 0.02 to about 0.50 wt. percent manganese, a maximum of about 0.05 wt. percent silicon, and between about 0.005 and about 0.09 wt. percent aluminum.

Claim 23

A method as in claim 17, wherein no other alloying element is added to said low carbon steel in an amount greater than the wt. percent of titanium added to said steel.

Claim 24

A method as in claim 16, wherein no other alloying element is added to said low carbon steel in an amount greater than 1 percent of the weight of said steel.