Method of processing stainless steels

Claim 2

In the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot worked intermediate product formed from an ingot having a composition com- prising up to 0.25% maximum carbon, about 11.0% to about 14.5% chromiiim, and the balance substantially iron with incidental impurities, the steps comprising, sub- jecting the intermediate product to a subscritical nor- malizing treatment at a temperature in the range between 1200° F. and 1500° F., cold reducing the normalized intermediate product to effect a reduction therein of be- tween 10% to 60% such that the thickness of the cold reduced intermediate product is within 10% to 40% of the finished thickness of the final product, heating the cold reduced intermediate product at a temperature in the range between 1700° F. and 1875° F., cooling to harden the product, cold reducing the hardened cold reduced intermediate product 10% io 40% to the finish thickness of the final product, and stress relief annealing the final product at a temperature in the range between 700° F. and 1100° F., the final product being character- ized by having a hardness of 46 Rc minimum and a proof stress in excess of 180,000 p. s. i. }

Claim 3

In the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot worked intermediate product formed. from an ingot having a composition com- prising up t6 0.25% maximum carbon, about 11.0% to about 14.5% chromium, and the balance substantially iron with incidental impurities, the steps comprising, sub- jecting the intermediate product to a continuous sub- critical normalizing treatment by heating it to a tem- perature in the range between 1200° F. and 1500° F. for a time period ranging between 45 minutes and 75 minutes. per inch of thickness of the normalized intermediate 2,781,388 11 product, cold reducing the normalized intermediate prod- uct to effect a reduction therein of between 10% and 60% such that the thickness of the cold reduced intermediate product is within 10% to 40% of the finished thickness of the final product, continuously hardening the cold re- duced intermediate product by heating it to a temper- ature in the range between 1700° F. and 1875° F., for a time period ranging between 30 minutes and 65 minutes per inch of thickness of the cold reduced intermediate product to harden the product cooling, cold reducing the hardened cold reduced intermediate product to the finish thickness of the final product, and continuously stress relief annealing the final product at a temperature in the range between 700° F. and 1100° F., for a time period ranging between 45 minutes and 75 minutes per inch of thickness of the final product, the final product being characterized by having a hardness of 46 Rc minimum and a proof stress in excess of 180,000 p. s. i.

Claim 4

In the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot worked intermediate product formed. from an ingot having a composition com- prising up t6 0.25% maximum carbon, about 11.0% to about 14.5% chromium, and the balance substantially iron with incidental impurities, the steps comprising, sub- jecting the intermediate product to a continuous sub- critical normalizing treatment by heating it to a tem- perature in the range between 1200° F. and 1500° F. for a time period ranging between 45 minutes and 75 minutes. per inch of thickness of the normalized intermediate 2,781,388 11 product, cold reducing the normalized intermediate prod- uct to effect a reduction therein of between 10% and 60% such that the thickness of the cold reduced intermediate product is within 10% to 40% of the finished thickness of the final product, continuously hardening the cold re- duced intermediate product by heating it to a temper- ature in the range between 1700° F. and 1875° F., for a time period ranging between 30 minutes and 65 minutes per inch of thickness of the cold reduced intermediate product to harden the product cooling, cold reducing the hardened cold reduced intermediate product to the finish thickness of the final product, and continuously stress relief annealing the final product at a temperature in the range between 700° F. and 1100° F., for a time period ranging between 45 minutes and 75 minutes per inch of thickness of the final product, the final product being characterized by having a hardness of 46 Rc minimum and a proof stress in excess of 180,000 p. s. i.

Claim 5

In the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot rolled intermediate product having a thickness in the range between 0.100 and 0.200 inch formed from an ingot having a composi- tion comprising up to 0.15% maximum carbon, about 11.0% to about 13.5% chromium, and the balance sub- 2 stantially iron with incidental impurities, the steps com- prising, subjecting the intermediate strip product to a continuous subcritical normalizing treatment at a tem- perature in the range between 1250° F. and 1300° F., for a time period of about 60 minutes per inch of thickness of the hot rolled intermediate strip product to obtain a hardness in the strip in the range between 26 Re and 30 Re, cold roll reducing the normalized intermediate strip product to effect a reduction in thickness therein of be- tween 10% and 60% such that the thickness of the cold ¢ roli reduced intermediate strip product is within 20% to 30% of the finish thickness of the final product, con- tinuously hardening the cold roll reduced intermediate strip product by heating at a temperature in the range be- tween 1700° F. and 1800° F. for a time period of about “45 minutes per inch of thickness of the cold roll reduced intermediate strip product and cooling to produce a hard- ness in the range between 43 Rc and 47 Rc therein, cold roll reducing the hardened cold roll reduced intermediate strip product to the finish thickness of the final product, and continuously stress relief annealing the final strip product at a temperature in the range between 800° F. and 850° F. for a time period of about 60 minutes per inch of thickness of the final strip product to remove the internal stresses therefrom, the final strip product having * a hardness in the range between 48 Re and 54 Re and a proof stress in excess of 215,000 p. s. i.

Claim 6

In the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot rolled intermediate product having a thickness in the range between 0.100 and 0.200 inch formed from an ingot having a composi- tion comprising up to 0.15% maximum carbon, about 11.0% to about 13.5% chromium, and the balance sub- 2 stantially iron with incidental impurities, the steps com- prising, subjecting the intermediate strip product to a continuous subcritical normalizing treatment at a tem- perature in the range between 1250° F. and 1300° F., for a time period of about 60 minutes per inch of thickness of the hot rolled intermediate strip product to obtain a hardness in the strip in the range between 26 Re and 30 Re, cold roll reducing the normalized intermediate strip product to effect a reduction in thickness therein of be- tween 10% and 60% such that the thickness of the cold ¢ roli reduced intermediate strip product is within 20% to 30% of the finish thickness of the final product, con- tinuously hardening the cold roll reduced intermediate strip product by heating at a temperature in the range be- tween 1700° F. and 1800° F. for a time period of about “45 minutes per inch of thickness of the cold roll reduced intermediate strip product and cooling to produce a hard- ness in the range between 43 Rc and 47 Rc therein, cold roll reducing the hardened cold roll reduced intermediate strip product to the finish thickness of the final product, and continuously stress relief annealing the final strip product at a temperature in the range between 800° F. and 850° F. for a time period of about 60 minutes per inch of thickness of the final strip product to remove the internal stresses therefrom, the final strip product having * a hardness in the range between 48 Re and 54 Re and a proof stress in excess of 215,000 p. s. i.

Claim 7

Tn the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot worked intermediate ° product formed from an ingot having a composition com- prising up to 0.25% maximum carbon about 11.0% to about 14.5% chromium, and the balance substantially iron with incidental impurities, the steps comprising, sub- jecting the intermediate product to a subcritical nor- malizing treatment at a temperature in the range between 1200° F. and 1500° F., cold reducing the normalized intermediate product to a size within 10% to 40% of the finish thickness of the final product, such cold reduc- tion being effected in a plurality of steps with a nor- malizing treatment between each of said steps, each of the cold reductions effecting a reduction of between 10% to 60% of the thickness of the starting material of each step, the last of said cold reductions effecting a reduction to within 10% to 40% of the finish thickness of the final product, the normalizing treatment between each of the cold reductions being a subcritical normalizing treatment at a temperature in the range be- tween 1200° F. and 1500° F., subjecting said cold re- duced material to a temperature in the range between 10 40 GO -3 i 12 1700° F. and 1875° F., cooling to harden it, cold re- ducing the hardened cold reduced material to the finish thickness of the final product, and stress relief annealing the final product at a temperature in the range between 700° F. and 1100° F., the final product being character- ized by having a hardness of 46 Rc minimum and a prcof stress in excess of 180,000 p. s. i.

Claim 8

Tn the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot worked intermediate ° product formed from an ingot having a composition com- prising up to 0.25% maximum carbon about 11.0% to about 14.5% chromium, and the balance substantially iron with incidental impurities, the steps comprising, sub- jecting the intermediate product to a subcritical nor- malizing treatment at a temperature in the range between 1200° F. and 1500° F., cold reducing the normalized intermediate product to a size within 10% to 40% of the finish thickness of the final product, such cold reduc- tion being effected in a plurality of steps with a nor- malizing treatment between each of said steps, each of the cold reductions effecting a reduction of between 10% to 60% of the thickness of the starting material of each step, the last of said cold reductions effecting a reduction to within 10% to 40% of the finish thickness of the final product, the normalizing treatment between each of the cold reductions being a subcritical normalizing treatment at a temperature in the range be- tween 1200° F. and 1500° F., subjecting said cold re- duced material to a temperature in the range between 10 40 GO -3 i 12 1700° F. and 1875° F., cooling to harden it, cold re- ducing the hardened cold reduced material to the finish thickness of the final product, and stress relief annealing the final product at a temperature in the range between 700° F. and 1100° F., the final product being character- ized by having a hardness of 46 Rc minimum and a prcof stress in excess of 180,000 p. s. i.

Claim 9

In the method of producing stainless steel having a high hardness, high proof stress and substantial free- dom from internal stresses from a hot worked inter- mediate product formed from an ingot having a com- position comprising ip to 0.25% maximum carbon, about 11.0% to about 14.5% chromium, and the balance sub- stantially iron with incidental impurities, the steps com- prising, subjecting the intermediate product to a con- tinuous subcritical normalizing treatment by heating it to a temperature in the range between 1200° F. and 1500° F. for a time period ranging between 45 minutes and 75 minutes per inch of thickness of the hot worked intermediate product, cold reducing the normalized in- termediate product to a size within 10% to 40% of the finish thickness of the final product, such cold reduction being effected in a plurality of steps with a normalizing treatment between each of said steps, each of the cold reductions effecting a reduction in thickness of between 10% and 60% of the thickness of the starting material of each step, the last of said cold reductions effecting a reduction to within 10% to 40% of the finish thick- ness of the final product, the normalizing treatment be- tween each of the cold reductions being a continucus subcritical normalizing treatment at a temperature in the range between 1200° F. and 1500° F. for a time period ranging between 45 minutes and 75 minutes per inch of thickness of the cold reduced steel, subjecting said cold reduced steel! to a continuous hardening treatment by heating at a temperature in the range between 1700° F. and 1875° F. for a time period ranging between 30 min- utes and 65 minutes per inch of thickness of the cold re- duced steel and cooling to harden it, cold reducing the hardened cold reduced steel to the finish thickness of the final product, and continuously stress relief annealing the final product at a temperature in the range between 700° F. and 1100° F. for a time period ranging between 45 minutes and 75 minutes per inch of thickness of the final product, the final product being characterized by having a hardness of 46 Re minimum and a preof stress in excess of 180,000 p. s. i.

Claim 10

In the method of producing stainless steel having a high hardness, high proof stress and substantial free- dom from internal stresses from a hot worked inter- mediate product formed from an ingot having a com- position comprising ip to 0.25% maximum carbon, about 11.0% to about 14.5% chromium, and the balance sub- stantially iron with incidental impurities, the steps com- prising, subjecting the intermediate product to a con- tinuous subcritical normalizing treatment by heating it to a temperature in the range between 1200° F. and 1500° F. for a time period ranging between 45 minutes and 75 minutes per inch of thickness of the hot worked intermediate product, cold reducing the normalized in- termediate product to a size within 10% to 40% of the finish thickness of the final product, such cold reduction being effected in a plurality of steps with a normalizing treatment between each of said steps, each of the cold reductions effecting a reduction in thickness of between 10% and 60% of the thickness of the starting material of each step, the last of said cold reductions effecting a reduction to within 10% to 40% of the finish thick- ness of the final product, the normalizing treatment be- tween each of the cold reductions being a continucus subcritical normalizing treatment at a temperature in the range between 1200° F. and 1500° F. for a time period ranging between 45 minutes and 75 minutes per inch of thickness of the cold reduced steel, subjecting said cold reduced steel! to a continuous hardening treatment by heating at a temperature in the range between 1700° F. and 1875° F. for a time period ranging between 30 min- utes and 65 minutes per inch of thickness of the cold re- duced steel and cooling to harden it, cold reducing the hardened cold reduced steel to the finish thickness of the final product, and continuously stress relief annealing the final product at a temperature in the range between 700° F. and 1100° F. for a time period ranging between 45 minutes and 75 minutes per inch of thickness of the final product, the final product being characterized by having a hardness of 46 Re minimum and a preof stress in excess of 180,000 p. s. i.

Claim 11

In the method of producing stainless steel! having a high hardness, high proof stress and substantial free- dom from internal stresses from a hot rolled interme- diate product having a thickness in the range between 0.100 and 0.200 inch formed from an ingot having a composition comprising up to 0.15% maximum carbon about 11.0% to about 13.5% chromium, and the balance substantially iron with incidental impurities, the steps comprising, subjecting the hot rolled intermediate strip product to a continuous subcritical normalizing treatment bv heating the strip to a temperature in the range between 1250° F. and 1300° F. for a time period of about 60 minutes per inch of thickness of the hot rolled interme- diate strip product to soften it to a hardness in the range between 25 Re and 30 Re, cold roll reducing the normal- ized intermediate strip product to a thickness within 10% to 40% of the finish thickness of the final strip product, such cold roll reduction being effected in a plurality of op- erations with a normalizing treatment between each of said cold roll reducing operations, each of the cold roll reductions effecting a reduction of between 10% to 60% of the thickness of the starting strip material of each cold rell reducing operation, the last of said cold roll reduc- tions being accomplished on highly polished work rells and effecting a reduction to within 20% to 3C% of the finish thickness of the final strip product, the normaliz- ing treatment between each of ‘the cold roll reductions being a contintious subcritical normalizing treatment at a 2,781,288 13 temperature in the range between 1250° F. and 1300° F. for a time period of about 60 minutes per inch of cold roll reduced strip thickness to soften the strip to a hard- ness in the range between 25 Re and 30 Re, subjecting said cold roll reduced strip material to a continuous hard- ening treatment by heating at a temperature in the range between 1700° F. and 1800° F. for a time period of about 45 minutes per inch of thickness of the cold roll reduced strip material and cooling to harden it to a hardness in the range between 44 Rc and 46 Re, cold rol reducing the hardened strip material using highly polished work rolls to the finish thickness of the final strip prod- uct, and continuously stress relief annealing the final product at a temperature in the range between 800° F. and 850° F. for a time period of about 60 minutes per inch of thickness of the final strip product to remove the internal stresses therefrom, the final product being characterized by having a hardness of 48 Rc minimum, a proof stress in excess of 215,000 p. s. i. and a bright surface finish having a reflectivity of at least 40%.

Claim 12

In the method of producing stainless steel! having a high hardness, high proof stress and substantial free- dom from internal stresses from a hot rolled interme- diate product having a thickness in the range between 0.100 and 0.200 inch formed from an ingot having a composition comprising up to 0.15% maximum carbon about 11.0% to about 13.5% chromium, and the balance substantially iron with incidental impurities, the steps comprising, subjecting the hot rolled intermediate strip product to a continuous subcritical normalizing treatment bv heating the strip to a temperature in the range between 1250° F. and 1300° F. for a time period of about 60 minutes per inch of thickness of the hot rolled interme- diate strip product to soften it to a hardness in the range between 25 Re and 30 Re, cold roll reducing the normal- ized intermediate strip product to a thickness within 10% to 40% of the finish thickness of the final strip product, such cold roll reduction being effected in a plurality of op- erations with a normalizing treatment between each of said cold roll reducing operations, each of the cold roll reductions effecting a reduction of between 10% to 60% of the thickness of the starting strip material of each cold rell reducing operation, the last of said cold roll reduc- tions being accomplished on highly polished work rells and effecting a reduction to within 20% to 3C% of the finish thickness of the final strip product, the normaliz- ing treatment between each of ‘the cold roll reductions being a contintious subcritical normalizing treatment at a 2,781,288 13 temperature in the range between 1250° F. and 1300° F. for a time period of about 60 minutes per inch of cold roll reduced strip thickness to soften the strip to a hard- ness in the range between 25 Re and 30 Re, subjecting said cold roll reduced strip material to a continuous hard- ening treatment by heating at a temperature in the range between 1700° F. and 1800° F. for a time period of about 45 minutes per inch of thickness of the cold roll reduced strip material and cooling to harden it to a hardness in the range between 44 Rc and 46 Re, cold rol reducing the hardened strip material using highly polished work rolls to the finish thickness of the final strip prod- uct, and continuously stress relief annealing the final product at a temperature in the range between 800° F. and 850° F. for a time period of about 60 minutes per inch of thickness of the final strip product to remove the internal stresses therefrom, the final product being characterized by having a hardness of 48 Rc minimum, a proof stress in excess of 215,000 p. s. i. and a bright surface finish having a reflectivity of at least 40%.

Claim 13

In the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot rolled intermediate product having a thickness of about 0.160 inch formed from an ingot having a composition comprising about 0.14% carbon, about 12.88% chromium and the balance substantially iron with incidental impurities, the steps comprising, subjecting the hot rolled intermediate strip product having a thickness of about 0.160 inch to a con- tinuous subcritical normalizing treatment by heating it to a temperature in the range between 1250° F. and 1300° F. for a time period of about 9% minutes to soften the steel to a hardness of about 26 Re, pickling the normal- ized intermediate strip product to remove the scale there- from and provide the strip with a clean surface, cold roll reducing the normalized and pickled intermediate strip product about 25% to a thickness of about 0.120 inch, subjecting the cold roll reduced intermediate strip product to a continuous subcritical normalizing treatment by heating it to a temperature in the range of 1250° EF. and 1300° F. for a time period of about 7 minutes to soften the strip product to a hardness of about 26 Re, pickling the cold roll reduced and normalized strip prod- uct to remove the scale therefrom, cold roll reducing the normalized and pickled strip product to within about 25% of the thickness of the final product by reducing the thickness of the normalized and pickled strip product about 33% to a thickness of about 0.080 inch using highly polished work rolls, subjecting said cold reduced strip product to a continuous hardening treatment by heating at a temperature in the range between 1700° F. and 1800° F. for about 5 minutes and cooling to harden it to a hardness of about 44 Re, cold roll reducing the 14 hardened strip product on highly polished work rolls about 25% to the finish thickness of about 0.060 inch of the final strip product, and continuously stress relief annealing the final strip product at a temperature in the range between 800° F. and 850° F. for a time period of about 3% minutes to remove the internal stresses there- from, the final strip product being characterized by having a bright surface finish, a hardness of about 48 Re, and a proof stress of about 222,200 p. s. i.

Claim 14

In the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot rolled intermediate product having a thickness of about 0.160 inch formed from an ingot having a composition comprising about 0.14% carbon, about 12.88% chromium and the balance substantially iron with incidental impurities, the steps comprising, subjecting the hot rolled intermediate strip product having a thickness of about 0.160 inch to a con- tinuous subcritical normalizing treatment by heating it to a temperature in the range between 1250° F. and 1300° F. for a time period of about 9% minutes to soften the steel to a hardness of about 26 Re, pickling the normal- ized intermediate strip product to remove the scale there- from and provide the strip with a clean surface, cold roll reducing the normalized and pickled intermediate strip product about 25% to a thickness of about 0.120 inch, subjecting the cold roll reduced intermediate strip product to a continuous subcritical normalizing treatment by heating it to a temperature in the range of 1250° EF. and 1300° F. for a time period of about 7 minutes to soften the strip product to a hardness of about 26 Re, pickling the cold roll reduced and normalized strip prod- uct to remove the scale therefrom, cold roll reducing the normalized and pickled strip product to within about 25% of the thickness of the final product by reducing the thickness of the normalized and pickled strip product about 33% to a thickness of about 0.080 inch using highly polished work rolls, subjecting said cold reduced strip product to a continuous hardening treatment by heating at a temperature in the range between 1700° F. and 1800° F. for about 5 minutes and cooling to harden it to a hardness of about 44 Re, cold roll reducing the 14 hardened strip product on highly polished work rolls about 25% to the finish thickness of about 0.060 inch of the final strip product, and continuously stress relief annealing the final strip product at a temperature in the range between 800° F. and 850° F. for a time period of about 3% minutes to remove the internal stresses there- from, the final strip product being characterized by having a bright surface finish, a hardness of about 48 Re, and a proof stress of about 222,200 p. s. i.

Claim 15

In the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot rolled intermediate product having a thickness of about 0.125 inch formed from an ingot having a composition comprising about 0.14% carbon, about 12.88% chromium and the balance substantially iron with incidental impurities, the steps comprising, subjecting the hot rolled intermediate strip product having a thickness of about 0.125 inch to a continuous subcritical normalizing treatment by heating it to a temperature in the range between 1250° F. and 1300° F. for a time period of about 7% minutes to soften the steel to a hardness of about 26 Re, pickling the normalized intermediate strip product to remove the scale therefrom and provide the strip with a clean sur- face, cold roll reducing the normalized and pickled inter- mediate strip product about 56% to a thickness of about 0.055 inch, subjecting the cold roll reduced intermediate strip product to a continuous subcritical normalizing treatment by heating it to a temperature in the range of 1250° F. and 1300° F. for a time period of about 3% minutes to soften the strip product to a hardness of about 26 Re, pickling the cold roll reduced and normalized strip product to remove the scale therefrom, cold Toll reducing the normalized and pickled strip product to within about 25% of the thickness of the final product by reducing the thickness of the normalized and pickled strip product abou: 56% to a thickness of about 0.024 inch using highly polished work rolls, subjecting said cold reduced strip product to a continuous hardening treat- ment by heating at a temperature in the range between 1700° F. and 1800° F. for about 1.5 minutes and cool- ing to harden it to a hardness of about 44 Re, cold roll reducing the hardened strip product on highly polished work rolls about 25% to the finish thickness of about 0.018 inch of the final strip product, and continuously stress relief annealing the final strip product at a tem- perature in the range between 800° F. and 850° F. for a time period of about 1 minute to remove the internal stresses therefrom, the final strip product being character- ized by having a bright surface finish, a hardness of about 48 Rc, and a proof stress of about 230,000 p. Ss. i. No references cited,

Claim 16

In the method of producing stainless steel having a high hardness, high proof stress and substantial freedom from internal stresses from a hot rolled intermediate product having a thickness of about 0.125 inch formed from an ingot having a composition comprising about 0.14% carbon, about 12.88% chromium and the balance substantially iron with incidental impurities, the steps comprising, subjecting the hot rolled intermediate strip product having a thickness of about 0.125 inch to a continuous subcritical normalizing treatment by heating it to a temperature in the range between 1250° F. and 1300° F. for a time period of about 7% minutes to soften the steel to a hardness of about 26 Re, pickling the normalized intermediate strip product to remove the scale therefrom and provide the strip with a clean sur- face, cold roll reducing the normalized and pickled inter- mediate strip product about 56% to a thickness of about 0.055 inch, subjecting the cold roll reduced intermediate strip product to a continuous subcritical normalizing treatment by heating it to a temperature in the range of 1250° F. and 1300° F. for a time period of about 3% minutes to soften the strip product to a hardness of about 26 Re, pickling the cold roll reduced and normalized strip product to remove the scale therefrom, cold Toll reducing the normalized and pickled strip product to within about 25% of the thickness of the final product by reducing the thickness of the normalized and pickled strip product abou: 56% to a thickness of about 0.024 inch using highly polished work rolls, subjecting said cold reduced strip product to a continuous hardening treat- ment by heating at a temperature in the range between 1700° F. and 1800° F. for about 1.5 minutes and cool- ing to harden it to a hardness of about 44 Re, cold roll reducing the hardened strip product on highly polished work rolls about 25% to the finish thickness of about 0.018 inch of the final strip product, and continuously stress relief annealing the final strip product at a tem- perature in the range between 800° F. and 850° F. for a time period of about 1 minute to remove the internal stresses therefrom, the final strip product being character- ized by having a bright surface finish, a hardness of about 48 Rc, and a proof stress of about 230,000 p. Ss. i. No references cited,