# US 11,078,554 B2 · Lightweight steel and steel sheet with enhanced elastic modulus, and manufacturing method thereof

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- Number: US 11,078,554 B2
- Document ID: US11078554B2
- Status: Granted
- Kind: B2
- Application number: 16/092,867
- Filed: 2017-03-30
- Published: 2019-05-16
- Granted: 2021-08-03
- Earliest claimed: 2016-04-05
- Assignees: Baoshan Iron & Steel Co., Ltd.
- Applicants: Baoshan Iron & Steel Co., Ltd.
- Inventors: Qi Yang; Li Wang
- Web page: https://patentgrep.com/patent/US11078554B2

## CPC

- C21D 9/46: for sheet metals
- B22D 11/001: {of specific alloys}
- C21D 6/001: {containing Ni (C21D6/004 takes precedence)}
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/02: during manufacturing of plates or strips (C21D8/12 takes precedence)
- C21D 8/0226: {Hot rolling}
- C21D 8/0236: {Cold rolling}
- C21D 8/0273: {Final recrystallisation annealing}
- C22C 38/001: {containing N}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/08: containing nickel {(C22C38/105 takes precedence)}
- C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium
- C22C 38/14: containing titanium or zirconium
- C22C 38/16: containing copper
- C22C 38/18: containing chromium
- C22C 38/22: with molybdenum or tungsten
- C22C 38/26: with niobium or tantalum
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- C22C 38/38: with more than 1.5% by weight of manganese
- C21D 2211/002: Bainite
- C21D 2211/004: Dispersions; Precipitations
- C21D 2211/005: Ferrite
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- B22D: CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES (shaping of plastics or substances in a plastic state B29C; metallurgical processing, selection of substances to be added to metal C21, C22)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

There is disclosed a lightweight steel with an enhanced elastic modulus, wherein the lightweight steel has a chemical composition by mass percentage of 0.001%≤C≤0.30%, 0.05%≤Mn≤4.0%, 1.5%<Al<3.0%, 1.5%≤Ti≤7.0%, 0.5%≤B≤3.6%, and the remainder consisting of Fe and other unavoidable impurities. A microstructure of the lightweight steel comprises a matrix and fine hardening granules evenly distributed throughout the matrix. The matrix entirely or partially comprises a ferrite and/or a bainite. The hardening granule comprises at least TiB2.

## Claims

### Claim 1

A lightweight steel with an enhanced elastic modulus, wherein:
the lightweight steel has a chemical composition by mass percentage of 0.001%≤C≤0.30%, 0.05%≤Mn≤4.0%, 1.6%≤Al≤2.9%, 1.5%≤Ti≤7.0%, 0.5%≤B≤3.6%, at least one of the elements: 0.01%≤Si≤1.5%, 0.01%≤Cr≤2.0%, 0.01%≤Mo≤1.0%, 0.01%≤Nb≤0.2%, 0.01%≤V≤0.5%, 0.05%≤Ni≤1.0%, 0.05%≤Cu≤1.0%, and 0.001%≤Ca≤0.2%, and with a balance of Fe and unavoidable impurity elements;
the lightweight steel has a microstructure comprising a matrix and fine hard reinforcing particles dispersedly distributed in the matrix uniformly, wherein the matrix is entirely or partially ferrite and/or bainite, wherein the hard reinforcing particles comprise at least TiB2; and
wherein the lightweight steel has a tensile strength >500 MPa, an elastic modulus >200 GPa, and a density <7600 kg/m3.

### Claim 2 (depends on 1)

The lightweight steel of claim 1, wherein the Ti and B elements further meet: −1.2%≤(Ti-2.22*B)≤1.2%.

### Claim 3 (depends on 2)

The lightweight steel of claim 2, wherein the hard particles have a volumetric fraction amounting to at least 3% of the whole microstructure.

### Claim 4 (depends on 2)

The lightweight steel of claim 2, wherein the Ti element has a content of 3.0%≤Ti≤6.0%; the B element has a content of 1.2%≤B3.0%; the Ti and B elements further meet: −0.6%≤(Ti −2.22*B)≤0.6%; and the hard particles have a volumetric fraction amounting to at least 6% of the whole microstructure.

### Claim 5 (depends on 4)

The lightweight steel of claim 4, wherein the lightweight steel has a tensile strength >500 MPa, an elastic modulus >210 GPa, and a density <7400 kg/m3.

### Claim 6 (depends on 1)

The lightweight steel of claim 1, wherein the hard reinforcing particles further comprise at least one of TiC and Fe2B.

### Claim 7 (depends on 1)

The lightweight steel of claim 1, wherein the hard reinforcing particles have an average particle size of less than 15 μm.

### Claim 8 (depends on 1)

A steel sheet made of the lightweight steel according to claim 1.

### Claim 9 (depends on 8)

A manufacturing method for the steel sheet of claim 8, comprising the following steps:
(1) Smelting and continuous casting to obtain a slab having a thickness of 120-300 mm; and
(2) Hot rolling to obtain a hot-rolled sheet.

### Claim 10 (depends on 9)

The manufacturing method of claim 9, wherein Step (2) is followed by Step (3): recrystallization annealing.

### Claim 11 (depends on 9)

The manufacturing method of claim 9, wherein, in Step (2), a heating temperature is 1000-1250° C.; a soaking time is 0.5-3 h; a final rolling temperature is ≥850° C.; and coiling is performed at 400-750° C.

### Claim 12 (depends on 10)

The manufacturing method of claim 10, wherein, when the hot-rolled sheet is subjected to recrystallization annealing by way of continuous annealing in Step (3), the hot-rolled sheet is heated to a soaking temperature of 800-1000° C., held for 30-600s, and then cooled to room temperature.

### Claim 13 (depends on 10)

The manufacturing method of claim 10, wherein, when the hot-rolled sheet is subjected to recrystallization annealing by way of bell furnace annealing in Step (3), the hot-rolled sheet is heated to a soaking temperature of 650-900° C., held for 0.5-48 h, and then cooled to room temperature along with the furnace.

### Claim 14 (depends on 8)

A manufacturing method for the steel sheet of claim 8, comprising the following steps:
(1) Smelting and strip casting to obtain a thin strip having a thickness of no more than 10 mm; and
(2) Hot rolling to obtain a hot-rolled sheet.

### Claim 15 (depends on 14)

The manufacturing method of claim 14, wherein Step (2) is followed by Step (3): recrystallization annealing.

### Claim 16 (depends on 14)

The manufacturing method of claim 14, wherein, in Step (2), the thin strip is hot rolled immediately with no aid of external heating; a final rolling temperature is controlled at ≥850° C.; a hot rolling reduction is 20-60%; and coiling is then performed at 400−750° C.

### Claim 17 (depends on 15)

The manufacturing method of claim 15, wherein, when the hot-rolled sheet is subjected to recrystallization annealing by way of continuous annealing in Step (3), the hot-rolled sheet is heated to a soaking temperature of 800-1000° C., held for 30-600s, and then cooled to room temperature.

### Claim 18 (depends on 15)

The manufacturing method of claim 15, wherein, when the hot-rolled sheet is subjected to recrystallization annealing by way of bell furnace annealing in Step (3), the hot-rolled sheet is heated to a soaking temperature of 650-900° C., held for 0.5-48 h, and then cooled to room temperature along with the furnace.

### Claim 19 (depends on 8)

A manufacturing method for the steel sheet of claim 8, comprising the following steps:
(1) Smelting and continuous casting to obtain a slab having a thickness of 120-300 mm;
(2) Hot rolling;
(3) Pickling;
(4) Cold rolling to obtain a cold-rolled sheet; and
(5) Recrystallization annealing of the cold-rolled sheet.

### Claim 20 (depends on 19)

The manufacturing method of claim 19, wherein Step (2) is followed by a post-hot-rolling recrystallization annealing.

### Claim 21 (depends on 19)

The manufacturing method of claim 19, wherein, in Step (2), a heating temperature is 1000-1250° C.; a soaking time is 0.5-3 h; a final rolling temperature is ≤850° C.; and coiling is then performed at 400-750° C.

### Claim 22 (depends on 20)

The manufacturing method of claim 20, wherein, when the post-hot-rolling recrystallization annealing is performed by a continuous annealing, the hot-rolled sheet is heated to a soaking temperature of 800-1000° C., held for 30-600s, and then cooled to room temperature.

### Claim 23 (depends on 20)

The manufacturing method of claim 20, wherein, when the post-hot-rolling recrystallization annealing is performed by a bell furnace annealing, the hot-rolled sheet is heated to a soaking temperature of 650-900° C., held for 0.5-48 h, and then cooled to room temperature along with the furnace.

### Claim 24 (depends on 19)

The manufacturing method of claim 19, wherein a cold rolling reduction is controlled at 25-75% in Step (4).

### Claim 25 (depends on 19)

The manufacturing method of claim 19, wherein, when the recrystallization annealing of the cold-rolled sheet is performed by a continuous annealing in Step (5), the cold-rolled sheet is heated to a soaking temperature of 700-900° C., held for 30-600s, and then cooled to room temperature.

### Claim 26 (depends on 19)

The manufacturing method of claim 19, wherein, when the recrystallization annealing of the cold-rolled sheet is performed by a bell furnace annealing in Step (5), the cold-rolled sheet is heated to a soaking temperature of 600-800° C., held for 0.5-48 h, and then cooled to room temperature along with the furnace.

### Claim 27 (depends on 8)

A manufacturing method for the steel sheet of claim 8, comprising the following steps:
(1) Smelting and strip casting to obtain a thin strip having a thickness of no more than 10 mm;
(2) Hot rolling;
(3) Pickling;
(4) Cold rolling to obtain a cold-rolled sheet; and
(5) Recrystallization annealing of the cold-rolled sheet.

### Claim 28 (depends on 27)

The manufacturing method of claim 27, wherein Step (2) is followed by a post-hot-rolling recrystallization annealing.

### Claim 29 (depends on 27)

The manufacturing method of claim 27, wherein, in Step (2), the thin strip is hot rolled immediately with no aid of external heating; a final rolling temperature is controlled at ≥850° C.; a hot rolling reduction is 20-60%; and coiling is then performed at 400-750° C.

### Claim 30 (depends on 28)

The manufacturing method of claim 28, wherein, when the post-hot-rolling recrystallization annealing is performed by a continuous annealing, the hot-rolled sheet is heated to a soaking temperature of 800-1000° C., held for 30-600s, and then cooled to room temperature.

### Claim 31 (depends on 28)

The manufacturing method of claim 28, wherein, when the post-hot-rolling recrystallization annealing is performed by a bell furnace annealing, the hot-rolled sheet is heated to a soaking temperature of 650-900° C., held for 0.5-48 h, and then cooled to room temperature along with the furnace.

### Claim 32 (depends on 27)

The manufacturing method of claim 27, wherein a cold rolling reduction is controlled at 25-75% in Step (4).

### Claim 33 (depends on 27)

The manufacturing method of claim 27, wherein, when the recrystallization annealing of the cold-rolled sheet is performed by a continuous annealing in Step (5), the cold-rolled sheet is heated to a soaking temperature of 700-900° C., held for 30-600s, and then cooled to room temperature.

### Claim 34 (depends on 27)

The manufacturing method of claim 27, wherein, when the recrystallization annealing of the cold-rolled sheet is performed by a bell furnace annealing in Step (5), the cold-rolled sheet is heated to a soaking temperature of 600-800° C., held for 0.5-48 h, and then cooled to room temperature along with the furnace.