High strength galvanized steel sheet having excellent bendability and weldability, and method of manufacturing the same

Patent metadata

Field	Value
Publication number	US-2016017473-A1
Application number	US-201514870322-A
Country	US
Kind code	A1
Filing date	Sep 30, 2015
Priority date	May 31, 2010
Publication date	Jan 21, 2016
Grant date	—

Abstract

A method of manufacturing a galvanized steel sheet includes a two-stage temperature raising process which includes: primary heating the sheet from 200° C. to an intermediate temperature of 500 to 800° C. at a primary average heating rate of 5 to 50° C./second at an excess air ratio of 1.10 to 1.20 maintained up to the intermediate temperature; secondary heating the sheet from the intermediate temperature to an annealing temperature of 730 to 900° C. at a secondary average heating rate of 0.1 to 10° C./second at an excess air ratio of less than 1.10 maintained up to the annealing temperature; holding the sheet to the annealing temperature for 10 to 500 seconds; cooling the sheet to 450 to 550° C. at an average cooling rate of 1 to 30° C./second; and subjecting the sheet to a galvanizing process and, optionally, an alloying process.

First claim

1 . A method of manufacturing a galvanized steel sheet comprising:
subjecting a steel slab having a composition comprising by mass:
C: equal to or more than 0.05% and less than 0.12%;
P: 0.001 to 0.040%;
S: equal to or less than 0.0050%;
Si: 0.01 to 1.6%;
Mn: 2.0 to 3.5%;
Al: 0.005 to 0.1%;
N: equal to or less than 0.0060%; and
the remainder as Fe and incidental impurities,

to heating at a temperature of 1150° C. to 1300° C. and then hot rolling the slab at a finisher delivery temperature of 850 to 950° C. to form a steel sheet;
cooling the steel sheet from the finisher delivery temperature to (the finisher delivery temperature minus 100° C.) at an average cooling rate of 5 to 200° C./second;
winding up the steel sheet into a coil at a temperature of 400 to 650° C.;
subjecting the steel sheet to pickling and cold rolling; and
subjecting the steel sheet to annealing including a two-stage temperature raising process, wherein the annealing step includes:
primary heating the steel sheet from 200° C. to an intermediate temperature of 500 to 800° C. at a primary average heating rate of 5 to 50° C./second at an excess air ratio of 1.10 to 1.20 maintained up to the intermediate temperature;
secondary heating the steel sheet from the intermediate temperature to an annealing temperature of 730 to 900° C. at a secondary average heating rate of 0.1 to 10° C./second at an excess air ratio of less than 1.10 maintained up to the annealing temperature;
holding the steel sheet in a range of the annealing temperature for 10 to 500 seconds;
cooling the steel sheet to a temperature of 450 to 550° C. at an average cooling rate of 1 to 30° C./second; and
subjecting the steel sheet to a galvanizing process and, optionally, an alloying process.

2 . A method of manufacturing a galvanized steel sheet, comprising:
subjecting a steel slab having a composition comprising by mass %:
C: equal to or more than 0.05% and less than 0.12%;
P: 0.001 to 0.040%;
S: equal to or less than 0.0050%;
Si: 0.01 to 1.6%;
Mn: 2.0 to 3.5%;
Al: 0.005 to 0.1%;
N: equal to or less than 0.0060%; and
at least one element selected from the group consisting of Cr: more than 0.5% and equal to or less than 2.0%, Mo: 0.01% to 0.50%, and B: 0.0001% to 0.0030%,
the remainder as Fe and incidental impurities,
to heating at a temperature of 1150° C. to 1300° C. and then hot rolling the slab at a finisher delivery temperature of 850 to 950° C. to form a steel sheet; cooling the steel sheet from the finisher delivery temperature to (the finisher delivery temperature minus 100° C.) at an average cooling rate of 5 to 200° C./second; winding up the steel sheet into a coil at a temperature of 400 to 650° C.; subjecting the steel sheet to pickling and cold rolling; and subjecting the steel sheet to annealing including a two-stage temperature raising process,
wherein the annealing step includes:
primary heating the steel sheet from 200° C. to an intermediate temperature of 500 to 800° C. at a primary average heating rate of 5 to 50° C./second at an excess air ratio of 1.10 to 1.20 maintained up to the intermediate temperature;
secondary heating the steel sheet from the intermediate temperature to an annealing temperature of 730 to 900° C. at a secondary average heating rate of 0.1 to 10° C./second at an excess air ratio of less than 1.10 maintained up to the annealing temperature;
holding the steel sheet in a range of the annealing temperature for 10 to 500 seconds;
cooling the steel sheet to a temperature of 450 to 550° C. at an average cooling rate of 1 to 30° C./second; and
subjecting the steel sheet to a galvanizing process and, optionally, an alloying process.

3 . A method of manufacturing a galvanized steel sheet, comprising:
subjecting a steel slab having a composition comprising by mass %:
C: equal to or more than 0.05% and less than 0.12%;
P: 0.001 to 0.040%;
S: equal to or less than 0.0050%;
Si: 0.01 to 1.6%;
Mn: 2.0 to 3.5%;
Al: 0.005 to 0.1%;
N: equal to or less than 0.0060%; and
at least one element selected from the group consisting of Ti: 0.010% to 0.080% and Nb: 0.010 to 0.080%,
the remainder as Fe and incidental impurities,
to heating at a temperature of 1150° C. to 1300° C. and then hot rolling the slab at a finisher delivery temperature of 850 to 950° C. to form a steel sheet; cooling the steel sheet from the finisher delivery temperature to (the finisher delivery temperature minus 100° C.) at an average cooling rate of 5 to 200° C./second; winding up the steel sheet into a coil at a temperature of 400 to 650° C.; subjecting the steel sheet to pickling and cold rolling; and subjecting the steel sheet to annealing including a two-stage temperature raising process, wherein the annealing step includes: primary heating the steel sheet from 200° C. to an intermediate temperature of 500 to 800° C. at a primary average heating rate of 5 to 50° C./second at an excess air ratio of 1.10 to 1.20 maintained up to the intermediate temperature; secondary heating the steel sheet from the intermediate temperature to an annealing temperature of 730 to 900° C. at a secondary average heating rate of 0.1 to 10° C./second at an excess air ratio of less than 1.10 maintained up to the annealing temperature; holding the steel sheet in a range of the annealing temperature for 10 to 500 seconds; cooling the steel sheet to a temperature of 450 to 550° C. at an average cooling rate of 1 to 30° C./second; and subjecting the steel sheet to a galvanizing process and, optionally, an alloying process.

4 . A method of manufacturing a galvanized steel sheet, comprising:
subjecting a steel slab having a composition by mass %:
C: equal to or more than 0.05% and less than 0.12%;
P: 0.001 to 0.040%;
S: equal to or less than 0.0050%;
Si: 0.01 to 1.6%;
Mn: 2.0 to 3.5%;
Al: 0.005 to 0.1%;
N: equal to or less than 0.0060%;
at least one element selected from the group consisting of Cr: more than 0.5% and equal to or less than 2.0%, Mo: 0.01% to 0.50%, and B: 0.0001% to 0.0030%; and
at least one element selected from the group consisting of: Ti: 0.010% to 0.080% and Nb: 0.010% to 0.080%,
the remainder as Fe and incidental impurities,
to heating at a temperature of 1150° C. to 1300° C. and then hot rolling the slab at a finisher delivery temperature of 850 to 950° C. to form a steel sheet; cooling the steel sheet from the finisher delivery temperature to (the finisher delivery temperature minus 100° C.) at an average cooling rate of 5 to 200° C./second; winding up the steel sheet into a coil at a temperature of 400 to 650° C.; subjecting the steel sheet to pickling and cold rolling; and subjecting the steel sheet to annealing including a two-stage temperature raising process, wherein the annealing step includes: primary heating the steel sheet from 200° C. to an intermediate temperature of 500 to 800° C. at a primary average heating rate of 5 to 50° C./second at an excess air ratio of 1.10 to 1.20 maintained up to the intermediate temperature; secondary heating the steel sheet from the intermediate temperature to an annealing temperature of 730 to 900° C. at a secondary average heating rate of 0.1 to 10° C./second at an excess air ratio of less than 1.10 maintained up to the annealing temperature; holding the steel sheet in a range of the annealing temperature for 10 to 500 seconds; cooling the steel sheet to a temperature of 450 to 550° C. at an average cooling rate of 1 to 30° C./second; and subjecting the steel sheet to a galvanizing process and, optionally, an alloying process.

5 . A method of manufacturing a galvanized steel sheet comprising:
subjecting a steel slab having a composition comprising by mass %:
C: equal to or more than 0.05% and less than 0.12%;
P: 0.001 t

Assignees

• Jfe Steel Corp

Inventors

• Takagi Shusaku
• Hasegawa Kohei

Classifications

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/06

  containing aluminium · CPC title

• C21D6/002

  containing Cr (C21D6/004 takes precedence) · CPC title

• C21D6/008

  containing Si · CPC title