Aluminum coated steel

Claim 1

AN ALUMINUM COATED LOW ALLOY MILD STEEL ARTICLE ADAPTED FOR SERIVICE AT AN ELEVATED TEMPERATURE COMPRISING, A LOW-ALLOY ALUMINUM KILLED LOW CARBON STEEL SHEET WHICH CONTAINS UNIFORMLY DISTRIBUTED THROUGHOUT AS AN ESSENTIAL COMBINATION OF ALLOY ELEMENTS TITANIUM IN AN AMOUNT UP TO A MIXIMUM OF 1% BY WT. WHICH COMBINES WITH ALL THE CARBON AND NITROGEN AND LEAVING UNCOMBINED TITANIUM THROUGHOUT THE STEEL AND MOLYBDENUM IN AN AMOUNT BETWEEN ABOUT 0.10 PERCENT AND 0.70 PERCENT BY WT. OF SAID STEEL, A UNIFORM THIN COATING OF METALLIC ALUMINUM DIRECTLY ON A SURFACE OF SAID STEEL SHEET WHICH IS FREE OF SURFACE OXIDES AND NON-METALLIC IMPURITIES, SAID ARTICLE IN THE AS COATED CONDITION EXHIBITING GOOD FORMABILITY AT ROOM TEMPERATURE AND HIGH CREEP RESISTANCE AND RUPTURE STRENGTH AT AN ELEVATED TEMPERATURE OF 1300*F-1500*F, AND SAID ARTICLE AFTER HEATING IN AN OXIDIZING ATMOSPHERE AT A TEMPERATURE OF 1500*F AND SAID ARTICLE HAVING ALUMINUM UNIFORMLY DIFFUSED INTO THE SURFACE OF STEEL SHEET WITH ONLY DISCRETE PARTICLE OF METALLIC OXIDE FORMED BELOW THE SURFACE OF SAID STEEL AS A DISCONTINUOUS SUBSURFACE STRATUM, WHEREBY SAID ALUMINUM COATED LOW ALLOY MILD STEEL ARTICLE EXHIBITS INCREASED OXIDATION RESISTANCE, HIGH CREEP RESISTANCE AND INCREASED RUPTURE STRENGTH ON HEATING THE SAID ELEVATED TEMPERATURE IN AN OXIDIZING ATMOSPHERE.

Claim 7

A method of providing an aluminum coated low alloy mild steel sheet which has good formability at room temperature and high creep resistance and rupture strength at an elevated temperature which comprises, applying a uniform thin coating of metallic aluminum directly to a surface of a steel sheet which is free surface oxides and non-metallic impurities and which is formed of a low-alloy aluminum killed low carbon steel having distributed uniformly throughout said steel as an essential combination of alloy element titanium in an amount up to 1% which combines with all the carbon and nitrogen in the said steel and molybdenum in an amount between about 0.10 and 0.70 percent by weight.

Claim 8

A method of providing an aluminum coated low alloy mild steel sheet which has good formability at room temperature and high creep resistance and rupture strength at an elevated temperature which comprises, applying a uniform thin coating of metallic aluminum directly to a surface of a steel sheet which is free surface oxides and non-metallic impurities and which is formed of a low-alloy aluminum killed low carbon steel having distributed uniformly throughout said steel as an essential combination of alloy element titanium in an amount up to 1% which combines with all the carbon and nitrogen in the said steel and molybdenum in an amount between about 0.10 and 0.70 percent by weight.

Claim 13

A method of providing an aluminum coated low alloy steel sheet which has good formability at room temperature and high creep resistance and rupture strength at an elevated temperature which comprises, adjusting the composition of an aluminum killed low-carbon steel which contains a maximum of about 0.10 wt. % carbon, a maximum of about 0.01 wt. % nitrogen, a maximum of about 0.70 wt. % manganese, and a maximum of about 0.09 wt. % aluminum with the balance being essentially iron with the normal amount of incidental impurities contained in a low-carbon aluminum killed steel by adding to said steel while said steel is in a molten condition as an essential combination of alloy elements titanium in an amount up to 1% by wt. which combines with all the carbon and nitrogen in the steel and leave an excess of uncombined titanium distributed throughout the steel and molybdenum in an amount between about 0.10 percent and 0.70 percent by weight to form a low-alloy aluminum killed low carbon steel and applying directly to a surface of a sheet of said low-alloy aluminum killed low-carbon steel while said surface is free of oxides and non-metallic impurities a thin uniform coating of molten metallic aluminum, and cooling said coating to provide an aluminum coated low-alloy steel sheet having good formability at room temperature and having high creep resistance and rupture strength at elevated temperatures up to 1500*F.

Claim 14

A method of providing an aluminum coated low alloy steel sheet which has good formability at room temperature and high creep resistance and rupture strength at an elevated temperature which comprises, adjusting the composition of an aluminum killed low-carbon steel which contains a maximum of about 0.10 wt. % carbon, a maximum of about 0.01 wt. % nitrogen, a maximum of about 0.70 wt. % manganese, and a maximum of about 0.09 wt. % aluminum with the balance being essentially iron with the normal amount of incidental impurities contained in a low-carbon aluminum killed steel by adding to said steel while said steel is in a molten condition as an essential combination of alloy elements titanium in an amount up to 1% by wt. which combines with all the carbon and nitrogen in the steel and leave an excess of uncombined titanium distributed throughout the steel and molybdenum in an amount between about 0.10 percent and 0.70 percent by weight to form a low-alloy aluminum killed low carbon steel and applying directly to a surface of a sheet of said low-alloy aluminum killed low-carbon steel while said surface is free of oxides and non-metallic impurities a thin uniform coating of molten metallic aluminum, and cooling said coating to provide an aluminum coated low-alloy steel sheet having good formability at room temperature and having high creep resistance and rupture strength at elevated temperatures up to 1500*F.