Hot stamping product with enhanced toughness and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-9920408-B2
Application number	US-201314762466-A
Country	US
Kind code	B2
Filing date	May 15, 2013
Priority date	May 9, 2013
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

Disclosed are a hot stamping part with enhanced toughness and a method for manufacturing the same, in which the hot stamping part has a tensile strength (TS) of 700-1,200 MPa after hot stamping while guaranteeing elongation (EL) of 12% or more by adjusting alloy components and controlling process conditions.

First claim

The invention claimed is:

1. A method for manufacturing a hot stamped product, comprising:
(a) forming a cold-rolled steel sheet through pickling and cold rolling a hot-rolled steel sheet, the hot-rolled steel sheet comprising carbon (C): 0.05˜0.14 wt %, silicon (Si): 0.01˜0.55 wt %, manganese (Mn): 1.0˜2.3 wt %, chromium (Cr): 0.01˜0.38 wt %, molybdenum (Mo): 0.05˜0.30 wt %, aluminum (Al): 0.01˜0.10 wt %, titanium (Ti): 0.03˜0.10 wt %, niobium (Nb): 0.02˜0.10 wt %, vanadium (V): 0.05 wt % or less, boron (B): 0.001 wt % or less, and the balance of iron (Fe) and unavoidable impurities;
(b) annealing the cold-rolled steel sheet at a temperature of 740° C. to 840° C., followed by hot dip plating;
(c) cutting the hot dip-plated steel sheet to form a blank;
(d) heating the blank to a temperature of 850° C. to 950° C.; and
(e) transferring the heated blank to a press mold, followed by hot stamping and then cooling the pressed product within the press mold in a closed state, thereby forming a hot stamped product,
wherein the hot stamped product has a tensile strength (TS) of 700 MPa to 1,200 MPa and an elongation (EL) of 12.0% to 17.0% after hot stamping.

2. The method according to claim 1 , wherein the hot-rolled steel sheet comprises at least one of phosphorus (P): 0.04 wt % or less and sulfur (S): 0.015 wt % or less.

3. The method according to claim 1 , wherein in (b) annealing the cold-rolled steel sheet, hot dip plating is performed by one selected from among Al—Si plating, hot-dip galvanizing, and hot-dip galvannealing.

4. The method according to claim 1 , wherein in (d) heating the blank, heat treatment of the blank is performed for 3 to 10 minutes.

5. The method according to claim 1 , wherein in (e) transferring the heated blank, the heated blank is transferred to the press mold within 15 seconds.

6. The method according to claim 1 , wherein cooling the pressed product within the press mold in a closed state comprises cooling the pressed product at a cooling rate of 30° C./sec to 300° C./sec for 5 seconds to 18 seconds, followed by quenching to 200° C. or less.

7. A method for manufacturing a hot stamped product, comprising:
(a) forming a cold-rolled steel sheet through pickling and cold rolling a hot-rolled steel sheet, the hot-rolled steel sheet including carbon (C): 0.05˜0.14 wt %, silicon (Si): 0.01˜0.55 wt %, manganese (Mn): 1.0˜2.3 wt %, chromium (Cr): 0.01˜0.38 wt %, molybdenum (Mo): 0.05˜0.30 wt %, aluminum (Al): 0.01˜0.10 wt %, titanium (Ti): 0.03˜0.10 wt %, niobium (Nb): 0.02˜0.10 wt %, vanadium (V): 0.05 wt % or less, boron (B): 0.001 wt % or less, and the balance of iron (Fe) and unavoidable impurities;
(b) annealing the cold-rolled steel sheet at a temperature of 740° C. to 840° C., followed by hot dip plating;
(c) cutting the hot dip-plated steel sheet to form a first blank, followed by laser welding the first blank and a second blank having a different composition and thickness than those of the first blank;
(d) heating the welded first and second blank to a temperature of 850° C. to 950° C.; and
(e) transferring the heated first and second blanks to a press mold, followed by hot stamping and then cooling the pressed product within the press mold in a closed state, thereby forming a hot stamped product,
wherein the hot stamped product has a tensile strength (TS) of 700 MPa to 1,200 MPa and an elongation (EL) of 12.0% to 17.0% after hot stamping.

8. The method according to claim 7 , wherein the second blank comprises carbon (C): 0.12˜0.42 wt %, silicon (Si): 0.03˜0.60 wt %, manganese (Mn): 0.8˜4.0 wt %, phosphorus (P): 0.2 wt % or less, sulfur (S): 0.1 wt % or less, chromium (Cr): 0.01˜1.0 wt %, boron (B): 0.0005˜0.03 wt %, at least one of aluminum (Al) and titanium (Ti): 0.05˜0.3 wt (in a total sum), at least one of nickel (Ni) and vanadium (V): 0.03˜4.0 wt % (in a total sum), and the balance of iron (Fe) and unavoidable impurities.

9. The method according to claim 7 , wherein after step (e), the first blank has a tensile strength (TS) of 700 MPa to 1,200 MPa and an elongation (EL) of 12.0% to 17.0%, and the second blank has a tensile strength (TS) of 1,200 MPa to 1,600 MPa and an elongation (EL) of 6.0% to 10.0%.

Assignees

• Hyundai Steel Co

Inventors

• Nam Seung-Man
• Lee Seung-Ha

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

• C21D9/0068

  for particular articles not mentioned below · CPC title

• C22C38/32

  with boron · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• C21D8/005

  Chemistry & Metallurgy · mapped topic