Method for producing thermo-mechanically produced hot-rolled strip products

Patent metadata

Field	Value
Publication number	US-12529128-B2
Application number	US-201917413187-A
Country	US
Kind code	B2
Filing date	Dec 18, 2019
Priority date	Dec 19, 2018
Publication date	Jan 20, 2026
Grant date	Jan 20, 2026

Abstract

The invention relates to a method for producing thermomechanically produced hot strip products in which a steel alloy is melted; the steel alloy is adjusted so that a recrystallization during the hot rolling is suppressed; the final rolling temperature is greater than 800° C.; the melted steel alloy is cast into slab ingots and after being heated to a temperature above Ac3, the slab ingots are hot rolled until they reach a desired degree of deformation and a desired strip thickness; after the rolling, the strip is cooled to room temperature and for hardening purposes, is briefly heated to a temperature >Ac3 and cooled again, characterized in that the heating takes place with a temperature increase of more than 5 K/s, more than 10 K/s, more than 50 K/s, or more than 100 K/s, and is kept at a desired target temperature for a period of 0.5 to 60 s before cooling to yield improved mechanical properties.

First claim

The invention claimed is:

1 . An inline, continuous method for producing thermomechanically produced hot-rolled strip products, comprising the steps of:
providing a steel alloy including the following elements, in percent by weight: 0.03 to 0.22% carbon, 0.0 to 2.0% silicon, 0.5 to 3.0% manganese, 0.02 to 1.2% aluminum, 0 to 2.0% chromium, 0 to 2.0% nickel, 0.0 to 1.0% molybdenum, 0.0 to 1.5% copper, 0 to 0.02% phosphorus, 0 to 0.01% sulfur, 0 to 0.008% nitrogen, 0 to 0.005% boron, 0.0 to 0.2% niobium, 0.0 to 0.3% titanium, 0.0 to 0.5% vanadium the remainder being comprised of iron and smelting-related impurities;
melting the steel alloy;
casting the melted steel alloy into slab ingots;
heating the slab ingots to a temperature above Ac3,
thermomechanically hot rolling the slab ingots using a final rolling temperature greater that 800° C. until they reach a desired degree of deformation and a reduced strip thickness and suppressing a recrystallization of the steel alloy during the hot rolling to form hot-rolled steel strips having a non-recrystallized elongated austenite structure;
cooling the hot-rolled steel strips to room temperature; and
after the cooling, hardening the hot-rolled steel strips by heating the hot-rolled steel strips to a target temperature >Ac3 and between about 800° C. and about 1000° C., and cooling the hot-rolled steel strips again to form hardened steel strips;
wherein the heating of the hot-rolled steel strips is performed using a temperature increase of more than 5 K/s, and the hot-rolled steel strips are kept at the target temperature for a holding period of about 0.5 to about 60 seconds prior to cooling the hot-rolled steel strips again; and
the hardened steel strips have a predominantly martensitic structure.

2 . The method according to claim 1 , wherein the steel alloy comprises the following elements in percent by weight:
0.055 to 0.195 carbon, 0.0 to 0.3% silicon, 1.4 to 2.3% manganese, 0.02 to 0.6% aluminum, 0 to 2% chromium, 0 to 2% nickel, 0.0 to 0.42% molybdenum, 0.0 to 0.5% copper, 0 to 0.008% phosphorus, 0 to 0.0015% sulfur, 0 to 0.007% nitrogen 0 to 0.005% boron, 0.0 to 0.2% niobium, 0.0 to 0.3% titanium, 0.0 to 0.5% vanadium, the remainder being comprised of iron and smelting-related impurities.

3 . The method according to claim 1 , wherein the heating of the hot-rolled steel strips comprises inductive heating.

4 . The method according to claim 1 , further comprising the step of annealing the hardened steel strips at a temperature of about 300° C. to about 700° C.

5 . The method according to claim 1 , wherein the holding period is about 0.5 to about 10 seconds.

6 . The method according to claim 1 , wherein the step of cooling the hot-rolled steel strips to room temperature takes place at a cooling rate of >10 K/s.

7 . The method according to claim 6 , wherein the cooling rate is >30K/s.

8 . The method according to claim 1 , wherein the heating of the hot-rolled steel strips is performed using rolling heat.

9 . The method according to claim 1 , further comprising the steps of welding the hardened steel strips by forming a weld seam, and heat treating the welded steel strips to homogenize the weld seam.

10 . The method according to claim 1 , wherein the hardened steel strips have a sheet thickness of about 1.5 mm to about 20 mm.

11 . The method according to claim 1 , wherein the step of hardening the hot-rolled steel strips is performed using a Hollomon-Jaffe parameter of about 18000 to about 23000.

12 . The method according to claim 1 , wherein the hardened steel strips comprise at least one of the following mechanical properties:
tensile strength (Rm)>=1000 MPa, and notched bar impact bending work (KV)>=50 J, measured at −40° C., and the following condition is satisfied:
Rm×KV>= 75000 MPa− J.

13 . An inline, continuous method for producing thermomechanically produced hot-rolled strip products, comprising the steps of:
providing a steel alloy including the following elements, in percent by weight: 0.03 to 0.22% carbon, 0.0 to 2.0% silicon, 0.5 to 3.0% manganese, 0.02 to 1.2% aluminum, 0 to 2.0% chromium, 0 to 2.0% nickel, 0.0 to 1.0% molybdenum, 0.0 to 1.5% copper, 0 to 0.04% total of phosphorus, sulfur, nitrogen and boron, 0.0 to 1.0% total of niobium, titanium and vanadium,
the remainder being comprised of iron and smelting-related impurities;
casting the melted steel alloy into slab ingots;
heating the slab ingots to a temperature above Ac3;
thermomechanically hot rolling the slab ingots using a final rolling temperature greater that 800° C. until they reach a desired degree of deformation and a reduced strip thickness and suppressing a recrystallization of the steel alloy during the hot rolling to form hot-rolled steel strips having a non-recrystallized elongated austenite structure;
cooling the hot-rolled steel strips to room temperature;
after the cooling, hardening the hot-rolled steel strips by heating the hot-rolled steel strips to a target temperature >Ac3 and between about 800° C. and about 1000° C., and cooling the hot-rolled steel strips again to form hardened steel strips; and
annealing the hardened steel strips at a temperature below Ac1;
wherein the heating of the hot-rolled steel strips is performed using a temperature increase of more than 5 K/s, and the hot-rolled steel strips are kept at the target temperature for a holding period of about 0.5 to about 60 seconds prior to cooling the hot-rolled steel strips again; and
the hardened steel strips have a predominantly martensitic structure.

14 . The method of claim 13 , wherein the hot-rolled strip products have a tensile strength Rm in excess of 1000 MPa, a notched bar impact bending work (KV) in excess of 50 J at −40° C., and a Rm×KV in excess of 75000 MPa−J.

15 . The method of claim 14 , wherein the Rm multiplied by the notched bar impact bending work (KV) is at least about 165,000 MPa−J.

16 . The method of claim 13 , wherein the steel alloy comprises the following elements in percent by weight:
0.055 to 0.195 carbon, 0.0 to 0.3% silicon, 1.4 to 2.3% manganese, 0.02 to 0.6% aluminum, 0 to 2% chromium, 0 to 2% nickel, 0.0 to 0.42% molybdenum, 0.0 to 0.5% copper, 0 to 0.008% phosphorus, 0 to 0.0015% sulfur, 0 to 0.007% nitrogen 0 to 0.005% boron, 0.0 to 0.2% niobium, 0.0 to 0.3% titanium, 0.0 to 0.5% vanadium the remainder being comprised of iron and smelting-related impurities.

17 . An inline, continuous method for producing thermomechanically produced hot-rolled strip products, comprising the steps of:
providing a steel alloy including the following elements, in percent by weight: 0.03 to 0.22% carbon, 0.0 to 2.0% silicon, 0.5 to 3.0% manganese, 0.02 to 1.2% aluminum, 0 to 2.0% chromium, 0 to 2.0% nickel, 0.0 to 1.0% molybdenum, 0.0 to 1.5% copper, 0 to 0.04% total of phosphorus, sulfur, nitrogen and boron, 0.0 to 1.0% total of niobium, titanium and vanadium,
the remainder being comprised of iron and smelting-related impurities;
casting the melted steel alloy into slab ingots;
heating the slab ingots to a temperature above Ac3,
thermomechanically hot rolling the slab ingots using a final rolling temperature greater that 800° C. until they reach a desired degree of deformation and a reduced strip thickness and suppressing a recrystallization of the steel alloy during the hot rolling to form hot-rolled steel strips having a non-recrystallized elonga

Assignees

• Voestalpine Stahl Gmbh

Inventors

• Ernst Wolfgang
• Spindler Helmut

Classifications

• C21D8/02

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

• C22C38/54

  with boron · CPC title

• C22C38/50

  with titanium or zirconium · CPC title

• C22C38/48

  with niobium or tantalum · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title