Process for producing an at least partly quenched and tempered sheet steel component and at least partly quenched and tempered sheet steel component

1 . An at least partly quenched and tempered sheet steel component, wherein the at least partly quenched and tempered sheet steel component has regions having different properties: a first region having a first property, comprising a microstructure having a wt % with residual austenite between 3% and <35%, 35% to 97% martensite, up to 30% bainite and unavoidable structure constituents, and

a second region having a second property, comprising a structure having a residual austenite fraction which is lower by comparison with the first region, balance martensite and optionally bainite and unavoidable structure constituents;

a third region having a third property, comprising a structure having a residual austenite fraction which is lower by comparison with the first region and, if present, by comparison with the second region, balance martensite and optionally bainite and unavoidable structure constituents; and

a fourth region having a fourth property, comprising a structure having <3% residual austenite, balance martensite and optionally bainite and unavoidable structure constituents;

wherein the at least partly quenched and tempered sheet steel component comprises the following chemical composition in wt %:

C=0.08 to 0.5;

Si+Al>0.75, and Si+2*Al<5, wherein the Si is at least 0.1; and

Mn=0.5 to 4,

balance Fe and unavoidable impurities.

2 . The sheet steel component as claimed in claim 1 , where the sheet steel component has the first, second, third and fourth regions, the first region having a residual austenite stability value S_RA>=0.3590 nm and/or a structure hardness value Hv_rC and wherein at least one of the second, third and fourth region having the following residual austenite stability values S_RA and/or structure hardness values Hv_rC:

the second region with an S_RA which is less than the S_RA of the first region, and with an Hv_rC which is greater by at least 10 Hv than the Hv_rC of the first region, and

the third region with an S_RA which is greater than the S_RA of the first region and of the second region, and with an Hv_rC which is less by at least 10 Hv than the Hv_rC of the first region, and

the fourth region, if residual austenite>0 and <3% is present, with S_RA<0.3950 nm and/or with an Hv_rC which is greater by at least 40 Hv than the Hv_rC of the first region and greater by at least 10 Hv than the Hv_rC of the second region,

where the residual austenite stability value S_RA is determined with the following formula:

S _ RA=G _ RA− 0.0002 nm*% Si− 0.0006 nm*% Al+ 0.0004 nm*% Mn , where G _ RA defines the lattice constant of the residual austenite,

where the structure hardness value Hv_rC of the first region meets the following condition: Hv_rC<320+800*(% C+% N)+75*(% Nb){circumflex over ( )}0.5.

3 . The sheet steel component as claimed in claim 2 , where the sheet steel component, between the regions having different properties, has one or more transition regions, where the transition region or regions space the various regions from one another with a transverse extent (Q) of at least 5 mm.

4 . The sheet steel component of claim 1 , further comprising one or more alloy elements from the group P, S, N, Cr, Mo, Ti, B, Nb, V, Ni, Cu, Sn, Ca, Mg, REM:

P up to 0.1,

S up to 0.1,

N up to 0.1,

Cr up to 1.5,

Mo up to 1,

Ti up to 0.2,

B up to 0.01,

Nb up to 0.2,

V up to 0.5,

Ni up to 2,

Cu up to 2,

Sn up to 0.5,

Ca up to 0.1,

Mg up to 0.1,

REM up to 0.1.

5 . An at least partly quenched and tempered sheet steel component, wherein the at least partly quenched and tempered sheet steel component has regions having different properties: a first region having a first property, comprising a microstructure having a wt % with residual austenite between 3% and <35%, 35% to 97% martensite, up to 30% bainite and unavoidable structure constituents, and at least one further region having a further property, comprising at least one of the following properties:

a second region having a second property, comprising a structure having a residual austenite fraction which is lower by comparison with the first region, balance martensite and optionally bainite and unavoidable structure constituents;

a third region having a third property, comprising a structure having a residual austenite fraction which is lower by comparison with the first region and, if present, by comparison with the second region, balance martensite and optionally bainite and unavoidable structure constituents; and

a fourth region having a fourth property, comprising a structure having <3% residual austenite, balance martensite and optionally bainite and unavoidable structure constituents;

wherein the at least partly quenched and tempered sheet steel component comprises the following chemical composition in wt %:

C=0.08 to 0.5;

Si+Al>0.75, and/or Si+2*Al<5, wherein the Si is at least 0.1;

Mn=0.5 to 4; and

Cr up to 1.5;

balance Fe and unavoidable impurities.

6 . The sheet steel component as claimed in claim 5 , wherein Al<=0.3.

7 . The sheet steel component as claimed in claim 5 , wherein Si>=1.2.

8 . The sheet steel component of claim 5 , further comprising one or more alloy elements from the group P, S, N, Mo, Ti, B, Nb, V, Ni, Cu, Sn, Ca, Mg, REM:

P up to 0.1,

S up to 0.1,

N up to 0.1,

Mo up to 1,

Ti up to 0.2,

B up to 0.01,

Nb up to 0.2,

V up to 0.5,

Ni up to 2,

Cu up to 2,

Sn up to 0.5,

Ca up to 0.1,

Mg up to 0.1,

REM up to 0.1.

9 . The sheet steel component as claimed in claim 1 , wherein the at least partly quenched and tempered sheet steel component comprises Si+Al>1.3 chemical composition in wt %.

10 . The sheet steel component as claimed in claim 5 , wherein the at least partly quenched and tempered sheet steel component comprises Si+Al>1.3 chemical composition in wt %.