Arcelormittal

Anirban Chakraborty

Hassan Ghassemi-Armaki

Christian Allely

Pascal Bertho

Jean-Marc Pipard

Olga A Girina

Damon Panahi

Pavan Challa Venkata Surya

Sebastien Cremel

Tiago Machado Amorim

Pavan C Venkatasurya

Michel Soler

Ronan Jacolot

Yacine Benlatreche

Alexey Koltsov

Patrice Alexandre

Magali Bouzat

Aude Nadler

Hassan Ghassemi-armaki

Pavan Challa Venkatasurya

The present invention relates to a method for the manufacture of a coated steel sheet comprising the following successive steps: A. the coating of the steel sheet with a first coating consisting of nickel and having a thickness between 600 nm and 1400 nm, the steel sheet having the following composition in weight: 0.10<C<0.40%, 1.5<Mn<3.0%, 0.7<Si<3.0%, 0.05<Al<1.0%, 0.75<(Si+Al)<3.0%, and on a purely optional basis, one or more elements such as Nb≤0.5%, B≤0.010%, Cr≤1.0%, Mo≤0.50%, Ni≤1.0%, Ti≤0.5%, the remainder of the composition making up of iron and inevitable impurities resulting from the elaboration, B. the recrystallization annealing at a temperature between 820 to 1200° C., C. the coating with a second coating based on zinc not comprising nickel.

Method for the manufacturing of liquid metal embrittlement resistant zinc coated steel sheet

The present invention relates to a method for the manufacture of a galvannealed steel sheet including the steps of A.) coating of the steel sheet with a first coating consisting of nickel and having a thickness between 150 nm and 650 nm, the steel sheet having the following composition in weight percentage 0.10<C<0.40%, 1.5<Mn<3.0%, 0.7<Si<3.0%, 0.05<Al<1.0%, 0.75<(Si+Al)<3.0%, and on a purely optional basis, one or more elements such as Nb≤0.5%, B≤0.010%, Cr≤1.0%, Mo≤0.50%, Ni≤1.0%, Ti≤0.5%., the remainder of the composition is made up of iron and inevitable impurities resulting from the elaboration, B.) annealing of the coated steel sheet being annealed at a temperature between 600 to 1200° C., C.) coating of the steel sheet obtained in step B.) with a second coating based on zinc and D.) an alloying heat treatment to form a galvannealed steel sheet.

Method for the manufacturing of liquid metal embrittlement resistant galvannealed steel sheet

Galvannealed steel sheet having a steel substrate coated with a first alloy layer with iron and nickel directly topped by a second alloy layer based on zinc, the first and second alloyed layers being alloyed through diffusion such that the second alloy layer includes from 5 to 15 wt. % of iron, from 0 to 15 wt. % of nickel, a balance being zinc.

Galvannealed steel sheet coated with an iron and nickel layer topped by a zinc-based layer

A method for producing a zinc or zinc-alloy coated steel sheet with a tensile strength higher than 900 MPa, for the fabrication of resistance spot welds containing in average not more than two Liquid Metal Embrittlement cracks per weld having a depth of 100 μm or more, with steps of providing a cold-rolled steel sheet, heating cold-rolled steel sheet up to a temperature T1 between 550° C. and Ac1+50° C. in a furnace zone with an atmosphere (A1) containing from 2 to 15% hydrogen by volume, so that the iron is not oxidized, then adding in the furnace atmosphere, water steam or oxygen with an injection flow rate Q higher than (0.07%/h×α), α being equal to 1 if said element is water steam or equal to 0.52 if said element is oxygen, at a temperature T≥T1, so to obtain an atmosphere (A2) with a dew point DP2 between −15° C. and the temperature Te of the iron/iron oxide equilibrium dew point, then heating the sheet from temperature Tup to a temperature Tbetween 720° C. and 1000° C. in a furnace zone under an atmosphere (A2) of nitrogen containing from 2 to 15% hydrogen and more than 0.1% CO by volume, with an oxygen partial pressure higher than 10atm., wherein the duration to of heating of the sheet from temperature Tup to the end of soaking at temperature Tis between 100 and 500 s, soaking the sheet at T, then cooling the sheet at a rate between 10 and 400° C./s, then coating the sheet with zinc or zinc-alloy coating.

Zinc-coated steel sheet with high resistance spot weldability

A method for producing a high-strength steel sheet having high ductility, formability and weldability includes providing a cold-rolled sheet, with a composition containing: 0.15% &#x2264;C&#x2264;0.23%, 1.4% &#x2264;Mn&#x2264;2.6%, 0.6% &#x2264;Si&#x2264;1.3%, with C+Si/10&#x2264;0.30%, 0.4% &#x2264;Al&#x2264;1.0%, with Al&#x2265;6(C+Mn/10)&#x2212;2.5%, 0.010% &#x2264;Nb&#x2264;0.035%, 0.1% &#x2264;Mo&#x2264;0.5%, annealing the sheet at 860&#xb0; C.-900&#xb0; C. to obtain a structure consisting of at least 90% austenite and at least 2% intercritical ferrite, quenching to a temperature between Ms-10&#xb0; C. and Ms-60&#xb0; C. at a rate Vc higher than 30&#xb0; C./s, heating to a temperature PT between 410&#xb0; C. and 470&#xb0; C. for 60 s to 130 s, hot-dip coating the sheet, and cooling to room temperature. The microstructure includes 45% to 68% of martensite, consisting of 85% to 95% partitioned martensite having a C content of at most 0.45%, and fresh martensite; 10% to 15% retained austenite; 2% to 10% intercritical ferrite; 20% to 30% lower bainite.

Method for producing a high strength steel sheet having high ductility, formability and weldability, and obtained steel sheet

A steel sheet coated with a coating comprising from 10 to 40% of nickel, the balance being zinc, such steel sheet having a microstructure comprising from 1 to 50% of residual austenite, from 1 to 60% of martensite and optionally at least one element chosen from: bainite, ferrite, cementite and pearlite, and the following chemical composition in weight: 0.10&#x3c;C&#x3c;0.50%, 1.0&#x3c;Mn&#x3c;5.0%, 0.7&#x3c;Si&#x3c;3.0%, 0.05&#x3c;Al&#x3c;1.0%, 0.75&#x3c;(Si+Al)&#x3c;3.0% and on a purely optional basis, one or more elements such as Nb&#x2264;0.5%, B&#x2264;0.005%, Cr&#x2264;1.0%, Mo&#x2264;0.50%, Ni&#x2264;1.0%, Ti&#x2264;0.5%, the remainder of the composition making up of iron and inevitable impurities resulting from the elaboration.

Method for the manufacture of a coated steel sheet

The present invention relates to a method for the manufacture of a galvannealed steel sheet including the steps of A.) coating of the steel sheet with a first coating consisting of nickel and having a thickness between 150 nm and 650 nm, the steel sheet having the following composition in weight percentage 0.10&#x3c;C&#x3c;0.40%, 1.5&#x3c;Mn&#x3c;3.0%, 0.7&#x3c;Si&#x3c;3.0%, 0.05&#x3c;Al&#x3c;1.0%, 0.75&#x3c;(Si+Al)&#x3c;3.0%, and on a purely optional basis, one or more elements such as Nb&#x2264;0.5%, B&#x2264;0.010%, Cr&#x2264;1.0%, Mo&#x2264;0.50%, Ni&#x2264;1.0%, Ti&#x2264;0.5%, the remainder of the composition is made up of iron and inevitable impurities resulting from the elaboration, B.) annealing of the coated steel sheet being annealed at a temperature between 600 to 1200&#xb0; C., C.) coating of the steel sheet obtained in step B.) with a second coating based on zinc and D.) an alloying heat treatment to form a galvannealed steel sheet.

A method for producing a zinc or zinc-alloy coated steel sheet with a tensile strength higher than 900 MPa, for the fabrication of resistance spot welds containing in average not more than two Liquid Metal Embrittlement cracks per weld having a depth of 100 &#x3bc;m or more, with steps of providing a cold-rolled steel sheet, heating cold-rolled steel sheet up to a temperature T1 between 550&#xb0; C. and Ac1+50&#xb0; C. in a furnace zone with an atmosphere (A1) containing from 2 to 15% hydrogen by volume, so that the iron is not oxidized, then adding in the furnace atmosphere, water steam or oxygen with an injection flow rate Q higher than (0.07%/h&#xd7;&#x3b1;), &#x3b1; being equal to 1 if said element is water steam or equal to 0.52 if said element is oxygen, at a temperature T&#x2265;T1, so to obtain an atmosphere (A2) with a dew point DP2 between &#x2212;15&#xb0; C. and the temperature Te of the iron/iron oxide equilibrium dew point, then heating the sheet from temperature Tup to a temperature Tbetween 720&#xb0; C. and 1000&#xb0; C. in a furnace zone under an atmosphere (A2) of nitrogen containing from 2 to 15% hydrogen and more than 0.1% CO by volume, with an oxygen partial pressure higher than 10atm., wherein the duration tof heating of the sheet from temperature Tup to the end of soaking at temperature Tis between 100 and 500 s., soaking the sheet at T, then cooling the sheet at a rate between 10 and 400&#xb0; C./s, then coating the sheet with zinc or zinc-alloy coating.

Method for the manufacture of a galvannealed steel sheet includes the following steps: A) the provision of a pre-coated steel sheet coated with a first coating comprising iron and nickel, such steel sheet having the following chemical composition in weight percent 0.10&#x3c;C&#x3c;0.40%, 1.5&#x3c;Mn&#x3c;3.0%, 0.7&#x3c;Si&#x3c;2.0%, 0.05&#x3c;Al&#x3c;1.0%, 0.75&#x3c;(Si+Al)&#x3c;3.0% and on a purely optional basis, one or more elements such as Nb&#x2264;0.5%, B&#x2264;0.005%, Cr&#x2264;1.0%, Mo&#x2264;0.50%, Ni&#x2264;1.0%, Ti&#x2264;0.5%, the remainder of the composition making up of iron and inevitable impurities resulting from the elaboration, B) the thermal treatment of such pre-coated steel sheet at a temperature between 600 to 1000&#xb0; C., C) the hot-dip coating of the steel sheet obtained in step B) with a second coating based on zinc and D) an alloying treatment to form a galvannealed steel sheet.

Method for the manufacture of a galvannealed steel sheet

The present invention relates to a method for the manufacture of a coated steel sheet comprising the following successive steps: A. the coating of the steel sheet with a first coating consisting of nickel and having a thickness between 600 nm and 1400 nm, the steel sheet having the following composition in weight: 0.10&#x3c;C&#x3c;0.40%, 1.5&#x3c;Mn&#x3c;3.0%, 0.7&#x3c;Si&#x3c;3.0%, 0.05&#x3c;Al&#x3c;1.0%, 0.75&#x3c;(Si+Al)&#x3c;3.0%, and on a purely optional basis, one or more elements such as Nb&#x2264;0.5%, B&#x2264;0.010%, Cr&#x2264;1.0%, Mo&#x2264;0.50%, Ni&#x2264;1.0%, Ti&#x2264;0.5%, the remainder of the composition making up of iron and inevitable impurities resulting from the elaboration, B. the recrystallization annealing at a temperature between 820 to 1200&#xb0; C., C. the coating with a second coating based on zinc not comprising nickel.

Method for the manufacture of a coated steel sheet including the following step of A) the provision of a pre-coated steel sheet coating with a first coating including iron and nickel, B) the thermal treatment of such pre-coated steel sheet at a temperature between 600 and 1000&#xb0; C., and C) the coating of the steel sheet obtained in step B) with a second coating based on zinc.

Growing community of inventors

Saint John, IN, United States of America

Anirban Chakraborty