Method for producing conventionally hot-rolled profiled strip products

Patent metadata

Field	Value
Publication number	US-12331369-B2
Application number	US-201917413435-A
Country	US
Kind code	B2
Filing date	Dec 18, 2019
Priority date	Dec 19, 2018
Publication date	Jun 17, 2025
Grant date	Jun 17, 2025

Abstract

The invention relates to a method for producing hot-rolled hot strip products in which a steel alloy is melted; the melted steel alloy is cast into slab ingots and after being heat-ed to a temperature above Ac3, the slab ingots are hot rolled until they reach a desired degree of deformation and a desired strip thickness; the rolling is performed above the recrystallization temperature of the alloy; after the rolling, the strip is cooled to room 10 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. A method for producing hot-rolled hot 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;
hot rolling the slab ingots to produce steel strips having a desired degree of deformation and a desired strip thickness, the rolling being performed above a recrystallization temperature of the alloy;
cooling the steel strips to room temperature;
after cooling the steel strips to room temperature, hardening the steel strips by heating the steel strips to a temperature >Ac3 and cooling the steel strips again to form hardened steel strips;
wherein the heating of the steel strips takes place with a temperature increase of more than 5 K/s, and the steel strips are kept at a desired target temperature for a holding period of 0.5 to 60s prior to cooling and an optional annealing; and
after hardening the steel strips, profiling the steel strips into one or more components using a forming process.

2. The method according to claim 1 , wherein the steel alloy comprises the following components 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 steel strips comprises inductive heating.

4. The method according to claim 1 , wherein the heating of the steel strips to a temperature >Ac3 comprises heating the steel strips to between about 800° C. and about 1000° C.

5. 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.

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

7. The method according to claim 1 , wherein the step of cooling the steel strips after the heating step takes place at a cooling rate of >10° K/s.

8. The method according to claim 1 , wherein the cooling rate is >30K/s.

9. A method for producing hot-rolled hot 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 melting the steel alloy;
casting the melted steel alloy into slab ingots;
heating the slab ingots to a temperature above Ac3;
hot rolling the slab ingots using one or more roll passes to produce steel strips having a desired degree of deformation and a desired strip thickness, the rolling being performed above a recrystallization temperature of the alloy;
cooling the steel strips to room temperature;
after cooling the steel strips to room temperature, hardening the steel strips by heating the steel strips to a temperature >Ac3 and cooling the steel strips again to form hardened steel strips;
wherein the heating of the steel strips takes place with a temperature increase of more than 10 K/s, and the steel strips are kept at a desired target temperature for a holding period of 0.5 to 60 s prior to cooling the steel strips again and an optional annealing; and
after hardening the steel strips, profiling the steel strips into one or more components using a forming process;
wherein recrystallization of the steel alloy does not occur during the one or more roll passes.

10. The method according to claim 1 , further comprising the steps of welding the formed steel strips to form a weld seam and heat treating the welded steel strips to homogenize the weld seam.

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

12. The method according to claim 1 , wherein the step of hardening the steel strips if performed using a Hollomon-Jaffee parameter of about 18000 to about 23000.

13. A profiled component produced with a method according to claim 1 , wherein the profiled component comprises at least one of the following mechanical properties:
tensile strength (Rm) >=1200 MPa,
notched bar impact bending work (KV) >=40 J, measured at −40° C.,
and the following condition is satisfied: Rm×KV >=50000 MPa J.

14. A use of the profiled component according to claim 13 for producing at least one of support structures in steel construction, machinery construction, automobile manufacture, and crane construction; security plates; and wear protection applications.

15. A method for producing hot-rolled hot 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 melting the steel alloy;
casting the melted steel alloy into slab ingots;
heating the slab ingots to a temperature above Ac3;
hot rolling the slab ingots to produce steel strips having a desired degree of deformation and a desired strip thickness, the rolling being performed above a recrystallization temperature of the alloy;
cooling the steel strips to room temperature;
after cooling the steel strips to room temperature, hardening the steel strips by heating the steel strips to a temperature >Ac3 and cooling the steel strips again to form hardened steel strips;
wherein the heating of the steel strips takes place with a temperature increase of more than 10 K/s, and the steel strips are kept at a desired target temperature for a holding period of 0.5 to 60 s prior to cooling the steel strips again and an optional annealing; and
after hardening the steel strips, profiling the steel strips into one or more components using a forming process.

16. The method of claim 15 , wherein the heating of the steel strips takes place with a temperature increase of more than 50 K/s.

17. The method of claim 15 , wherein the heating of the steel strips takes place with a temperature increase of more than 100 K/s.

18. The method according to claim 9 , wherein the heating of the steel strips during hardening is performed using inductive heating.

19. The method of claim 9 , wherein the hot rolled strip products comprise an elongated, non-recrystallized austenite structure.

Assignees

• Voestalpine Stahl Gmbh

Inventors

• Ernst Wolfgang
• Spindler Helmut

Classifications

• C22C38/54

  with boron · CPC title

• C22C38/50

  with titanium or zirconium · CPC title

• C22C38/48

  with niobium or tantalum · CPC title

• C22C38/46

  with vanadium · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title