100 kg-grade ultrahigh-strength galvanized steel sheet and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-2025346984-A1
Application number	US-202318879941-A
Country	US
Kind code	A1
Filing date	Jun 30, 2023
Priority date	Jun 30, 2022
Publication date	Nov 13, 2025
Grant date	—

Abstract

The present invention provides a 100 kg-grade ultra-high-strength galvanized steel sheet having excellent resistance spot welding properties and excellent resistance to liquid metal embrittlement (LME) cracking. The steel sheet contains the following components in percentage by weight: C: 0.17-0.25%, Mn: 1.7-2.7%, Si: 0.35-1.5%, Al: 0.01-1.0%, 0.7%≤Si+Al≤1.7%, and at least one of Nb, Ti and B, with the balance being Fe and unavoidable impurities. When the thickness of the steel sheet is t, the resistivity thereof is 0<R1≤50 μΩ·cm; and, in the direction from the coating layer/steel sheet substrate interface to the steel sheet substrate, when the thickness of the steel sheet is in the range of greater than or equal to 0.010t to less than or equal to 0.035t the resistivity thereof is 0<R2≤15 μΩ·cm, and when the thickness of the steel sheet is in the range of greater than 0.035t to less than or equal to 0.065t the resistivity thereof is 0<R3≤30 μΩ·cm, wherein (R2/2+R3/3)≤(3.1R11/2−1.5) is satisfied.

First claim

1 . A 100 Kg grade ultra-high strength galvanized steel plate, which comprises the following chemical elements by weight percentage:
C: 0.17-0.25%, Mn: 1.7-2.7%, Si: 0.35-1.5%, Al: 0.01-1.0%, 0.7%≤Si+Al≤1.7%, at least one of Nb, Ti and B, and a balance of Fe and unavoidable impurities, wherein the thickness of the steel plate is set to t, the resistivity R 1 of the steel plate is 0<R 1 ≤50μΩ·cm; in the direction from the interface between the plating layer and the steel plate matrix to the steel plate matrix, the resistivity R 2 of the steel plate in the range of 0.010 t to 0.035 t is 0<R 2 ≤15μΩ·cm, and the resistivity R 3 of the steel plate in the range of greater than 0.035 t to less than or equal to 0.065 t is 0<R 3 ≤30μΩ·cm, and they satisfy (R 2 /2+R 3 /3)≤(3.1R 1 1/2 −1.5).

2 . The 100 Kg grade ultra-high strength galvanized steel plate according to claim 1 , wherein the mass percentages of Nb, Ti, B are as follows:

0
<
Nb
≤

0.1
%

;

0
<
Ti
≤

0.1
%

;

0
<
B
≤

0.003

%
.

3 . The 100 Kg grade ultra-high strength galvanized steel plate according to claim 1 , wherein it comprises, by mass percentage, among other unavoidable impurities:

P
≤

0.015
%

S
≤

0.01
%

;

N
≤

0.008
%

;

REM
≤

0.01

%
.

4 . The 100 Kg grade ultra-high strength galvanized steel plate according to claim 1 , wherein it comprises at least one of the following components by mass percentage:
Nb: 0.03%-0.05%; Ti: 0.001%-0.02%; B: 0.0002%-0.0025%.

5 . The 100 Kg grade ultra-high strength galvanized steel plate according to claim 1 , wherein the thickness of the steel plate is set to t, the resistivity R 1 of the steel plate is 37μΩ·cm≤R 1 ≤50μΩ·cm, in the direction from the interface between the plating layer and the steel plate matrix to the steel plate matrix, the resistivity R 2 of the steel plate in the range of 0.010t to 0.035t is 9μΩ·cm≤R 2 ≤15μΩ·cm, and the resistivity R 3 of the steel plate in the range of greater than 0.035t to less than or equal to 0.065t is 24μΩ·cm≤R 3 ≤30μΩ·cm, and satisfies (R 2 /2+R 3 /3)≤(3.1R 1 1/2 −1.5).

6 . The 100 Kg grade ultra-high strength galvanized steel plate according to claim 1 , wherein the steel plate is configured as a GA plate or a GI plate.

7 . The 100 Kg grade ultra-high strength galvanized steel plate according to claim 1 , wherein when Type III specimens according to ISO 6892-1 standard are stretched at room temperature perpendicularly to the rolling direction, the steel plate has a tensile strength of ≥980 MPa, an elongation at break of ≥20%, and a hole expansion ratio of ≥20%.

8 . The 100 Kg grade ultra-high strength galvanized steel plate according to claim 1 , wherein when the steel plate is welded with 1 to 1.25 times of the I splash current, no Type B or Type C cracks will occur, and the depth of Type D cracks is not greater than 10% of the thickness of the base metal plate if Type D cracks are generated; when the steel plate is welded with 1 time or less of the I splash current, no Type B or Type C cracks will occur, and the depth of Type A cracks is not greater than 10% of the thickness of the base metal plate if Type A cracks are generated, wherein I splash is the minimum current at which splashing occurs.

9 . A manufacturing method for the 100 Kg grade ultra-high strength galvanized steel plate according to claim 1 , which comprises the following steps:
(1) Smelting and continuous casting to obtain a cast billet that satisfies the above composition of the steel plate according to claim 1 ; (2) Hot rolling: the cast billet obtained in step (1) is heated, subjected to final rolling, laminar flow cooling and coiling to obtain a hot-rolled coil; (3) Pickling and cold rolling: the hot-rolled coil obtained in step (2) is pickled, cold-rolled to obtain a cold rolled coil without annealing; (4) Continuous annealing: the cold rolled coil without annealing obtained in step (3) is subjected to a multi-stage heat treatment; (5) Galvanizing: the strip steel obtained in step (4) enters the zinc pot at a temperature of (zinc pot temperature T ZP ±15° C.) for galvanizing, to obtain a galvanized steel plate.

10 . The manufacturing method for the 100 Kg grade ultra-high strength galvanized steel plate according to claim 9 , wherein the multi-stage heat treatment comprises the following (a)-(d):
(a) First stage annealing: the cold rolled coil without annealing is heated to a first stage temperature in the range of not less than 600° C.˜(A c1 +40° C.) to obtain a steel coil, (b) Second stage annealing: the steel coil obtained in (a) is further heated to a second stage temperature in the range of (A c1 +50° C.)˜(A c3 +80° C.) or (A c1 +50° C.)˜900° C., and held for 30˜300 s to obtain a strip steel, wherein the smaller value from (A c3 +80° C.) and 900° C. is taken as the upper limit of the second stage temperature range, (c) Third stage annealing: the strip steel obtained in (b) is cooled to a third stage temperature in the range of M s ˜M f at a cooling rate that is not less than a certain cooling rate V 2-3 and held for 10˜200 s, (d) Fourth stage annealing, the strip steel obtained in (c) is heated again to a fourth stage temperature in the range of (350° C.˜zinc pot temperature) and held for 15˜90 s, wherein A c1 is the temperature at which the pearlite transforms into austenite when heated, A c3 is the final temperature of transforming into austenite when heated, M s is the temperature at which martensite appears, and M f is the temperature of full martensitization, V 2-3 represents the cooling rate, which is not less than 50° C./s.

11 . The manufacturing method for the 100 Kg grade ultra-high strength galvanized steel plate according to claim 10 , wherein
in (b), the second stage annealing temperature is controlled to be (A c1 +70° C.)˜(A c3 +80° C.) or (A c1 +70° C.)˜900° C., the holding time is controlled to be 35˜120 s, and the smaller value from (A c3 +80° C.) and 900° C. is taken as the upper limit of the second stage temperature range; and/or in (d), the fourth stage temperatur

Assignees

• Baoshan Iron & Steel

Inventors

• Chen Meng
• Zhong Yong
• Bi Wenzhen
• Wang Li

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C23C2/285

  for remelting the coating · CPC title

• C23C2/06

  Zinc or cadmium or alloys based thereon · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title

• C22C38/12

  containing tungsten, tantalum, molybdenum, vanadium, or niobium · CPC title