Armco Steel Corporation

Armco Steel Company, L.p.

Armco Inc.

Rollin E Hook

James A Elias

Ronald I Kinnett

A cold reduced, non-aging, aluminum killed steel characterized by an elongated grain structure and having an r.sub.m value at least 1.8 produced from a slab having a reduced hot rolling temperature. A slab consisting essentially of .ltoreq.0.08% carbon, .ltoreq.0.1% acid sol. aluminum, .ltoreq.0.2% manganese, all percentages by weight, the balance iron and unavoidable impurities, is hot rolled to a sheet from a temperature less than 1260.degree. C. Preferably, the slab is continuously cast from a melt consisting essentially of 0.03-0.08% acid sol. aluminum, 0.003-0.007% total nitrogen, &lt;0.20% manganese, wherein % acid sol. aluminum.times.% total nitrogen is within the range of 1.times.10.sup.-4 to 5.times.10.sup.-4 and is hot rolled from a temperature of 1093.degree.-1175.degree. C. The hot rolled sheet is descaled, cold reduced, batch annealed and temper rolled. Preferably, the cold reduced sheet is annealed in the range of 538.degree.-649.degree. C. and the temper rolled sheet has a tensile strength of 29-32 kg/mm.sup.2, a total elongation of at least 42% and an r.sub.m value of at least 2.0.

Cold reduced non-aging deep drawing steel and method for producing

A non-aging, cold reduced, recrystallization annealed, low manganese, aluminum killed steel having an r.sub.m value greater than 1.8 produced from a slab having a reduced hot rolling temperature. A slab consisting essentially of .ltoreq.0.08% carbon, .ltoreq.0.1% acid sol. aluminum, &lt;0.20% manganese, all percentages by weight, the balance iron and unavoidable impurities, is hot rolled from a temperature less than about 1260.degree. C. Preferably, the steel has an r.sub.m value of greater than 2.0 after batch annealing and is produced from a slab reheated to a temperature less than about 1175.degree. C.

A process of making aluminum killed, low manganese, deep drawing steel having a manganese content of up to 0.24%. The steel is hot rolled to hot band, cold rolled to final gauge, annealed and subjected to a small amount of temper rolling. In the annealing step, the steel is box annealed in coil form in such a manner that a coil cold spot temperature of at least about 1100.degree. F. (593.degree. C.) and below about 1250.degree. F. (677.degree. C.) is achieved.

Process of making aluminum killed low manganese deep drawing steel

A process of producing non-aging, low carbon steel having substantially no yield point elongation in the annealed condition and freedom from critical grain growth. A molten steel having an analysis typical of steel intended for rimmed or killed drawing steel is vacuum degassed to decarburize to a maximum carbon content of about 0.015%, and columbium (niobium) is added in an amount at least sufficient to combine with the carbon present in the steel. The cast material is hot rolled, finishing at 1500.degree. - 1700.degree. F (about 1090.degree. - 1200.degree. K) and coiled at a temperature of about 1500.degree. F (about 1090.degree. K) or less. The columbium addition retards the rate of recrystallization of the cold rolled product, and a wide spectrum of mechanical properties can be obtained in the final product by control of the final annealing time and temperature within the range of 1000.degree. to 1700.degree. F (about 810.degree. to 1200.degree. K). A preferred product is cold rolled and annealed strip suitable for deep drawing, porcelain enameling, hot dip metallic coating and the like, containing at least about 0.025% uncombined columbium at the hot rolling stage, as determined by analysis at room temperature, which has an average plastic strain ratio of at least 1.8, and a uniform grain size between ASTM 8 and 10.

Columbium treated, non-aging, vacuum degassed low carbon steel and

A method for internal strengthening of articles formed from deep drawing quality low carbon steel strip or sheet containing about 0.02 to about 0.3% titanium in solution, up to about 0.3% columbium in solution, columbium when present being in an amount of at least 0.025% in solution, with the sum total of titanium and columbium in solution not exceeding about 0.3%, comprising the steps of heating the articles at a temperature of about 570.degree. to about 580.degree. C in a nitriding fluid for a time sufficient to form a total nitrogen concentration adjacent the surfaces of the articles at least substantially equal to the amount theoretically required to combine completely with the nitride-forming elements in the steel; and diffusion annealing the articles in a non-nitriding fluid at a temperature of about 595.degree. to about 815.degree. C for a time sufficient to complete through-thickness strengthening by reaction of the nitrogen with the nitride-forming elements. A preferred nitriding fluid is a fused cyanate salt bath.

Method of nitride-strengthening low carbon steel articles

Deep drawing quality, low carbon steel is strengthened by alloy-nitrogen precipitation strengthening. A deoxidized, low carbon steel sheet or strip stock, or article formed therefrom, containing from about 0.02% to 0.2% titanium in solution, from about 0.025% to 0.3% columbium in solution, from about 0.025% to 0.3% zirconium in solution, singly or in admixture, is heat treated at 1100.degree. to 1300.degree. F (593.degree. to 705.degree. C) in an atmosphere containing 1% to 20% by volume ammonia for a time sufficient to produce an iron nitride surface layer, and then denitrided in a hydrogen-nitrogen atmosphere containing 6% to 50% hydrogen by volume at 1200.degree. to 1400.degree. F (649.degree. to 760.degree. C) for a time sufficient to remove the iron nitride surface layer and to reduce nitrogen in solid solution to less than 0.03% by weight.

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Dayton, OH, United States of America

Rollin E Hook