Galvanized steel sheet and method for producing the same

1. A galvanized steel sheet, comprising:

a steel sheet; and

a galvanizing layer which is formed on a surface of the steel sheet,

wherein the steel sheet includes as a chemical component, by mass %,

C: more than 0.100% to 0.500%,

Si: 0.0001% to less than 0.20%,

Mn: more than 0.20% to 0.5%,

Al: 3.0% to 10.0%,

N: 0.0030% to 0.0100%,

Ti: more than 0.100% to 1.000%,

P: 0.00001% to 0.0200%,

S: 0.00001% to 0.0100%, and

a remainder including Fe and impurities,

wherein a sum of a C content and a Ti content satisfies 0.200<C+Ti≤1.500, by mass %,

a product of an Al content and an Si content satisfies Al×Si≤0.8,

the galvanizing layer is a hot-dip galvannealing layer and includes as a chemical component, by mass %,

Fe: 7% to 15%,

Ni: 0.05% to 1.0%,

Al: 0.15% to 2.0%, and

a remainder including Zn and impurities, and

the galvanized steel sheet has a specific gravity of 5.5 to less than 7.5,

a CTS of the galvanized steel sheet evaluated in accordance with JIS Z 3137 with a spot welding under welding conditions, which are adjusted such that a nugget diameter is 5×√t mm at a sheet thickness of t mm, is 5 kN or higher, and

TS×λ is 30000 MPa ·% or more, in which TS is defined as a tensile strength of the galvanized steel sheet and λ is defined as a hole expansion ratio of the galvanized steel sheet.

2. The galvanized steel sheet according to claim 1 , wherein the steel sheet includes as a chemical component, by mass %, one element or two or more elements selected from the group consisting of

Nb: 0.300% or less,

V: 0.50% or less,

Cr: 3.00% or less,

Mo: 3.00% or less,

Ni: 5.00% or less,

Cu: 3.00% or less,

B: 0.0100% or less,

Ca: 0.0100% or less,

Mg: 0.0100% or less,

Zr: 0.0500% or less, and

REM: 0.0500% or less.

3. A method for producing the galvanized steel sheet according claim 1 , the method comprising:

performing a Ni-preplating treatment to the steel sheet so as to set a plating amount of Ni to 0.2 g/m 2 to 2 g/m 2 per one-sided surface of the steel sheet;

performing a heating treatment to the steel sheet to which the Ni-preplating treatment is performed to a temperature of 430° C. to 480° C. at a heating rate of 20° C/sec or more; and

performing a hot-dip galvanizing treatment by immersing the steel sheet into a galvanizing bath having a bath temperature of 440° C. to 470° C., and including, by mass %, Al: 0.1% to 0.4% and a remainder including Zn and impurities.

4. The method for producing the galvanized steel sheet according to claim 3 , further comprising:

performing an alloying heat treatment at a temperature of 470° C. to 560° C. for a heating time of 10 seconds to 40 seconds after the hot-dip galvanizing treatment is performed.