CN-117305698-B - 9Ni steel and preparation method thereof

Abstract

The invention discloses 9Ni steel and a preparation method thereof, and relates to the technical field of steel preparation. The 9Ni steel provided by the invention adopts a C-Si-Mn-Ni alloy component system, and comprises 0.035-0.05% of C, 0.5-0.8% of Si, 0.4-1.4% of Mn, 8-10% of Ni, less than or equal to 0.006% of P, less than or equal to 0.002% of S and the balance of Fe. And then the 9Ni steel is prepared by directly adopting continuous cooling and warm straightening procedures after a billet heating and two-stage steel plate rolling process. According to the invention, through reasonable component design and deformation heat treatment process technology, dislocation in the material after plastic processing is reserved, and the steel plate is directly quenched under the condition of retaining the dislocation, and after the steel plate is subjected to processes such as tempering, the steel plate with good toughness matching and good flatness is obtained, so that the production flow is simplified, the production process is optimized, the construction period is shortened, and the energy consumption is reduced.

Inventors

• LU SHIPING
• MA CHANGWEN
• WU WEIYANG
• DI GUOBIAO
• CHAI YUGUO
• WANG KAIKAI
• Ma longteng
• ZHANG SUYUAN
• ZHAO DEFU
• WANG HAIBAO
• YU WENFEI
• ZHANG XUEFENG

Assignees

• 首钢集团有限公司

Dates

Publication Date

20260512

Application Date

20230912

Claims (3)

1. 1. The preparation method of the 9Ni steel is characterized by comprising the following steps of: Preparing molten steel, and controlling a smelting process by adopting LF+VD to obtain a steel billet containing chemical components; Heating the steel billet in a stepping heating mode; Rolling the heated steel billet by adopting a two-stage rolling process to obtain a rolled steel plate; Directly quenching the rolled steel plate in a continuous cooling mode to obtain a quenched steel plate; carrying out warm straightening on the quenched steel plate; Tempering the straightened steel plate to obtain a 9Ni steel plate; The chemical components comprise 0.035-0.05% of C, 0.5-0.8% of Si, 0.4-1.4% of Mn, 8-10% of Ni, less than or equal to 0.006% of P, less than or equal to 0.002% of S, and the balance of Fe and unavoidable impurities; The step-by-step heating mode has the parameters that the heating rate is 4-6 ℃ at 200-700 ℃, the heating rate is 6-10 ℃ at 700-900 ℃, and the heating rate is 2 ℃ at the temperature of >900 ℃ until the heating is 1130-1150 ℃; The two-stage rolling process comprises a rough rolling stage and a finish rolling stage, wherein the initial rolling temperature of the rough rolling stage is 1000-1050 ℃, the rough rolling finishing temperature is 970-1000 ℃, the initial rolling temperature is 900-980 ℃ and the finish rolling finishing temperature is 800-890 ℃ in the finish rolling process; In the quenching process of the steel plate, the cooling rate of continuous cooling is 20-30 ℃ per second, and the cooling termination temperature is less than or equal to 100 ℃; the temperature of the warm straightening is less than 100 ℃; The structure of the 9Ni steel plate comprises tempered martensite and rotary austenite, and 3% -7% of the rotary austenite is distributed in the tempered martensite lath boundary; The yield strength of the 9Ni steel is above 680MPa, the tensile strength is above 740MPa, and the impact energy average value at-196 ℃ is at least 128J.
2. 2. The method of producing 9Ni steel according to claim 1, wherein the sulfur content of the steel slab is 0.002% or less and the phosphorus content of the steel slab is 0.006% or less.
3. 3. The method for producing 9Ni steel according to claim 1, wherein the tempering temperature in the tempering process is 550 ℃ to 600 ℃.

Description

9Ni steel and preparation method thereof Technical Field The application belongs to the technical field of steel plate preparation, and particularly relates to 9Ni steel and a preparation method thereof. Background Currently, 9Ni steel is one of the important materials for LNG storage and transportation facilities built in the world. At present, the production of the steel grade needs to adopt a plurality of heat treatment procedures to ensure that the steel grade has good toughness matching, and mainly adopts the processes of twice quenching and tempering, twice normalizing and tempering and once quenching and tempering to produce, but all have the problems of more heat treatment resources occupation, longer production flow, higher carbon emission, longer delivery period and the like, and the production efficiency of the steel grade is affected. Disclosure of Invention The application provides 9Ni steel and a preparation method thereof, which aim to solve the technical problems of long preparation period, low production efficiency and the like of the existing 9Ni steel. In a first aspect, the application provides 9Ni steel, which comprises, by weight, 0.035% -0.05% of C, 0.5% -0.8% of Si, 0.4% -1.4% of Mn, 8% -10% of Ni, less than or equal to 0.006% of P, less than or equal to 0.002% of S, and the balance of Fe and unavoidable impurities. Optionally, the structure of the 9Ni steel sheet includes tempered martensite and rotary austenite. Optionally, the tempered mahalanobis lath boundary is distributed with a set amount of said gyratory austenite, said set amount being 3% -7%. In a second aspect, the invention provides a method for preparing 9Ni steel, comprising the following steps: preparing molten steel, and controlling a smelting process by adopting LF+VD to obtain a steel billet containing the chemical components; Heating the steel billet in a stepping heating mode; Rolling the heated steel plate by adopting a two-stage rolling process to obtain a rolled steel plate; Directly quenching the rolled steel plate in a continuous cooling mode to obtain a quenched steel plate; carrying out warm straightening on the quenched steel plate; tempering the straightened steel plate to obtain the 9Ni steel plate. Optionally, the sulfur content of the steel billet is below 0.002%, the phosphorus content is below 0.006%, A, B, C class inclusions are respectively required to be less than or equal to 1.5 grade, wherein class A inclusions are sulfides, class B inclusions are alumina, and class C inclusions are silicate. Optionally, the step-by-step heating mode has the specific parameters of heating rate of 4-6 ℃ at 200-700 ℃ and heating rate of 6-10 ℃ at 700-900 ℃ and heating rate of 2 ℃ at >900 ℃ until 1130-1150 ℃. Optionally, the two-stage rolling process comprises a rough rolling stage and a finish rolling stage, wherein the initial rolling temperature of the rough rolling stage is 1000-1050 ℃, the rough rolling finishing temperature is 970-1000 ℃, the initial rolling temperature is 900-980 ℃ and the finish rolling finishing temperature is 800-890 ℃. Optionally, in the quenching process of the steel plate, the cooling rate of continuous cooling is 20-30 ℃ per second, and the cooling termination temperature is less than or equal to 100 ℃. Optionally, the temperature of the warm straightening is less than 100 ℃. Optionally, the tempering temperature in the tempering process is 550-600 ℃, the heating time is 40-60 min, and the heat preservation time is 30-50 min. Compared with the prior art, the technical scheme provided by the invention has the following advantages: The invention provides 9Ni steel and a preparation method thereof, wherein dislocation in a material after plastic processing is reserved for direct quenching by reasonable component design and deformation heat treatment technology, and the steel plate is subjected to tempering and other processes to obtain the steel plate with good toughness matching and good flatness, so that the production flow is simplified, the production process is optimized, the preparation period is shortened, the energy consumption is reduced, and the cost is also reduced. Drawings The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application. In order to more clearly illustrate the embodiments of the application or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort. FIG. 1 is a schematic flow chart of a preparation method of 9Ni steel provided by the application. Fig. 2 is a microstructure schematic of 9Ni steel provided in example 1. Fig. 3 is a microstructure schematic of 9N