# US 11,441,214 B2 · Low-yield-ratio ultra-high-strength high-toughness steel for pressure hulls and preparation method therefor

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- Number: US 11,441,214 B2
- Document ID: US11441214B2
- Status: Granted
- Kind: B2
- Application number: 17/130,785
- Filed: 2020-12-22
- Published: 2022-01-06
- Granted: 2022-09-13
- Earliest claimed: 2020-07-01
- Assignees: Northeastern University
- Applicants: Northeastern University
- Inventors: Qibin Ye; Liye Kan; Cheng Zhou; Qinghai Wang; Yimin Wang; Yong Tian; Zhaodong Wang
- Web page: https://patentgrep.com/patent/US11441214B2

## CPC

- C22C 38/46: with vanadium
- C21D 8/00: 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)
- C21D 8/0226: {Hot rolling}
- C21D 9/46: for sheet metals
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/42: with copper
- C22C 38/44: with molybdenum or tungsten
- C21D 2211/001: Austenite
- C21D 2211/005: Ferrite
- C21D 2211/008: Martensite
- Y02P 10/20: Recycling
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- 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)
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

The present invention discloses a low-yield-ratio ultra-high-strength high-toughness steel for pressure hulls and a preparation method therefor, wherein the chemical components by weight percentage are: 0.05%-0.10% of C, 0.15%-0.35% of Si, 0.60%-1.00% of Mn, 0.10%-0.50% of Cu, 0.10%-1.00% of Mo, 0.40%-0.70% of Cr, 0.05%-0.15% of V, 5.00%-10.00% of Ni, and the balance of Fe and unavoidable impurities. The technical solution of the present invention adopts secondary quenching heat treatment, the first quenching is performed to achieve complete austenitizing, and then the second quenching and tempering are performed to finally obtain complex phase structures such as tempered martensite, critical ferrite and retained austenite, so as to meet the performance index requirements of low yield ratio, ultra-high strength and high toughness, and thereby promoting application in practice.

## Claims

### Claim 1

A preparation method for a steel for pressure hulls, comprising the following steps:
step 1, melting
melting to obtain a casting blank using the following chemical components by weight percentage: 0.05%-0.10% of C, 0.15%-0.35% of Si, 0.60%-1.00% of Mn, 0.10%-0.50% of Cu, 0.10%-1.00% of Mo, 0.40%-0.70% of Cr, 0.05%-0.15% of V, 5.00%-10.00% of Ni, and the balance of Fe and unavoidable impurities,
step 2, hot rolling
keeping the casting blank obtained in step 1 at 1150° C.-1220° C. for soaking, and then performing hot rolling to a final thickness of 5-80 mm to obtain a hot-rolled steel plate; wherein the hot rolling comprises a two-stage rolling process, wherein a first stage of the two-stage rolling process is carried out at a rolling temperature of 1000° C.-1150° C. and a reduction of >50%, and wherein a second stage of the two-stage rolling process is carried out at a rolling temperature of 750° C.-900° C. and a reduction of >50%; and air cooling the hot-rolled steel plate after the hot rolling to room temperature;
step 3, heat treatment
heating a sample of the hot-rolled steel plate in step 2 to 790° C.-810° C., soaking for 20-40 minutes, and water quenching to room temperature; then heating again to 650° C.-690° C., soaking for 20-40 minutes, and water quenching to room temperature; and finally, tempering at 590° C.-610° C. for 50-70 minutes.