Method for suppressing internal oxidation in steel with antimony addition

Claim 1

In a process employing hot rolling and cold rolling for making a rolled steel product containing iron, carbon and at least one uncombined additional alloying element having an affinity for oxygen greater than that of iron, with said steel product being intended for subjection, in its cold rolled state, to at least one heating operation which causes oxidation of said uncombined alloying element in an internal oxidation layer adjacent the surface of said steel product, and wherein said uncombined alloying elements comprise silicon and aluminum included in said steel product to improve the magnetic properties thereof, a method for reducing the depth of said internal oxidation layer, said method comprising: providing the steel product with an antimony content of at least about 0.02 wt.% and which will form, upon the performance of such a heating operation, an antimony-enriched layer at, and immediately adjacent, the surface of said steel product; and minimizing the surface cleaning of said steel product before the completion of said cold rolling to minimize diminution of the antimony content before the performance of the first such heating operation after said completion of the cold rolling there being no annealing step prior to the completion of cold rolling.

Claim 10

A method for producing a cold rolled, temper rolled strip of electrical steel containing silicon and aluminum and which will suppress the formation of an internal oxidation layer containing oxides of silicon and aluminum adjacent the surface of said cold rolled steel strip during subsequent decarburizing after temper rolling, said method comprising the steps of: providing a steel composition consisting essentially of, in wt.%: carbon: up to 0.06, manganese: 0.20-0.75, silicon: 0.15-2.50, aluminum: 0.15-0.50, phosphorus: 0.12 max., sulfur: 0.02 max., antimony: 0.02-0.10 wt.%, iron: essentially the balance, hot rolling said steel into a strip; coiling said strip at an elevated temperature and then cooling the coiled strip; cold rolling said strip; annealing said strip after said cold rolling step, at a strip temperature which forms an antimony enriched layer at, and immediately adjacent, the surface of said strip; there being no annealing step after said hot rolling step and prior to the completion of cold-rolling; and temper rolling said strip after annealing; there being no substantial reduction in the carbon content of said steel in any of said steps through said temper rolling step.

Claim 11

A method for producing a cold rolled, temper rolled strip of electrical steel containing silicon and aluminum and which will suppress the formation of an internal oxidation layer containing oxides of silicon and aluminum adjacent the surface of said cold rolled steel strip during subsequent decarburizing after temper rolling, said method comprising the steps of: providing a steel composition consisting essentially of, in wt.%: carbon: up to 0.06, manganese: 0.20-0.75, silicon: 0.15-2.50, aluminum: 0.15-0.50, phosphorus: 0.12 max., sulfur: 0.02 max., antimony: 0.02-0.10 wt.%, iron: essentially the balance, hot rolling said steel into a strip; coiling said strip at an elevated temperature and then cooling the coiled strip; cold rolling said strip; annealing said strip after said cold rolling step, at a strip temperature which forms an antimony enriched layer at, and immediately adjacent, the surface of said strip; there being no annealing step after said hot rolling step and prior to the completion of cold-rolling; and temper rolling said strip after annealing; there being no substantial reduction in the carbon content of said steel in any of said steps through said temper rolling step.

Claim 17

A method for producing a cold rolled strip of electrical steel containing silicon and aluminum and which will suppress the formation of an internal oxidation layer containing oxides of silicon and aluminum adjacent the surface of said steel strip during subsequent decarburizing after cold rolling, said method comprising the steps of: providing a steel composition consisting essentially of, in wt%: carbon: up to 0.06, manganese: 0.20-0.75, silicon: 0.15-2.50, aluminum: 0.15-0.50, phosphorus: 0.12 max., sulfur: 0.02 max., antimony: 0.02-0.10 wt.%, iron: essentially the balance, hot rolling said steel into a strip; coiling said strip at an elevated temperature and then cooling the coiled strip; cold rolling said strip; there being no annealing step after said hot rolling step and prior to the completion of cold rolling; there being no substantial reduction in the carbon content of said steel in any of said steps through said cold rolling step; said method providing said cold cold rolled steel strip with an average ferritic grain size of about 11-13 ASTM.

Claim 18

A method for producing a cold rolled strip of electrical steel containing silicon and aluminum and which will suppress the formation of an internal oxidation layer containing oxides of silicon and aluminum adjacent the surface of said steel strip during subsequent decarburizing after cold rolling, said method comprising the steps of: providing a steel composition consisting essentially of, in wt%: carbon: up to 0.06, manganese: 0.20-0.75, silicon: 0.15-2.50, aluminum: 0.15-0.50, phosphorus: 0.12 max., sulfur: 0.02 max., antimony: 0.02-0.10 wt.%, iron: essentially the balance, hot rolling said steel into a strip; coiling said strip at an elevated temperature and then cooling the coiled strip; cold rolling said strip; there being no annealing step after said hot rolling step and prior to the completion of cold rolling; there being no substantial reduction in the carbon content of said steel in any of said steps through said cold rolling step; said method providing said cold cold rolled steel strip with an average ferritic grain size of about 11-13 ASTM.

Claim 21

A method for producing a cold rolled strip of electrical steel containing silicon and aluminum while suppressing the formation of an internal oxidation layer containing oxides of silicon and aluminum adjacent the surface of said cold rolled steel strip, said method comprising the steps of: providing a steel composition consisting essentially of, in wt.%: carbon: up to 0.06, manganese: 0.20-0.75, silicon: 0.15-2.50, aluminum: 0.15-0.50, phosphorus: 0.12 max., sulfur: 0.02, antimony: 0.02-0.10 wt.%, iron: essentially the balance, hot rolling said steel into a strip; coiling said strip at an elevated temperature and then cooling the coiled strip; cold rolling said strip; annealing said strip after said cold rolling step, at a strip temperature which forms an antimony-enriched layer at, and immediately adjacent, the surface of said strip; said annealing step being conducted in an oxidizing atmosphere to partially decarburize said steel strip to a carbon content in the range of about 0.01-0.02 wt.%; there being no annealing step after said hot rolling step and prior to the completion of said cold rolling step; said method providing said steel strip, after said annealing step, with an average ferritic grain size of about 6-8 ASTM; said method imparting to said steel strip sufficient strain to provide an average ferritic grain size of about 4-6 ASTM when the steel strip is subjected to a subsequent decarburizing and annealing operation.

Claim 22

A method for producing a cold rolled strip of electrical steel containing silicon and aluminum while suppressing the formation of an internal oxidation layer containing oxides of silicon and aluminum adjacent the surface of said cold rolled steel strip, said method comprising the steps of: providing a steel composition consisting essentially of, in wt.%: carbon: up to 0.06, manganese: 0.20-0.75, silicon: 0.15-2.50, aluminum: 0.15-0.50, phosphorus: 0.12 max., sulfur: 0.02, antimony: 0.02-0.10 wt.%, iron: essentially the balance, hot rolling said steel into a strip; coiling said strip at an elevated temperature and then cooling the coiled strip; cold rolling said strip; annealing said strip after said cold rolling step, at a strip temperature which forms an antimony-enriched layer at, and immediately adjacent, the surface of said strip; said annealing step being conducted in an oxidizing atmosphere to partially decarburize said steel strip to a carbon content in the range of about 0.01-0.02 wt.%; there being no annealing step after said hot rolling step and prior to the completion of said cold rolling step; said method providing said steel strip, after said annealing step, with an average ferritic grain size of about 6-8 ASTM; said method imparting to said steel strip sufficient strain to provide an average ferritic grain size of about 4-6 ASTM when the steel strip is subjected to a subsequent decarburizing and annealing operation.