CN-117305697-B - 9Ni steel plate and preparation method thereof

Abstract

The invention provides a 9Ni steel plate and a preparation method thereof, and relates to the technical field of steel rolling, wherein the chemical components of the 9Ni steel plate comprise, by weight, 0.04% -0.06% of C, 0.15% -0.35% of Si, 0.50% -0.80% of Mn, 8.5% -9.5% of Ni, less than or equal to 0.004% of P, less than or equal to 0.002% of S, 0.015% -0.045% of Als, and the balance of Fe and impurity elements. The 9Ni steel produced by the invention does not need to additionally add Nb, V, ti and other microalloy elements, thereby reducing the manufacturing cost of the steel plate. Meanwhile, the method has the characteristics of simple and easy heat treatment process and suitability for mass production.

Inventors

• CHAI YUGUO
• DONG ZHANBIN
• YU WENFEI
• WANG KUN
• LU SHIPING
• ZHOU DONGSHENG
• WEI SHANGHAO
• LIU MEIYAN
• LIU YANG
• LI ZHANJUN
• LV YANCHUN
• Ma longteng
• WANG GENJI
• MA CHANGWEN
• WANG QUANLI
• ZHOU DEGUANG
• HU XIANTANG
• WANG DONG
• WANG XING
• XIE CUIHONG

Assignees

• 首钢集团有限公司

Dates

Publication Date

20260512

Application Date

20230912

Claims (2)

1. 1. The preparation method of the 9Ni steel plate is characterized by comprising the following steps of: Preparing molten steel, and refining the molten steel into a steel billet; Polishing the surface of the steel billet to make the surface smooth, and then performing anti-oxidation coating treatment; heating the processed steel billet to 1030-1200 ℃, and preserving heat for 1-2 hours to obtain a heated steel billet; The heated billet is dephosphorized and rolled into a steel plate, whether the thickness of the steel plate is larger than 10mm or not is determined, if so, the steel plate is rolled by adopting rough rolling and finish rolling, and then the steel plate is cooled; Carrying out heat treatment on the rolled steel plate by adopting a quenching and tempering process to finally obtain a 9Ni steel plate; The cooling process adopts a water cooling mode, the final cooling temperature is 550-650 ℃, and the cooling speed is 5-10 ℃ per second; The heat treatment process specifically comprises the steps of heating the steel plate to 80-120 ℃ above A c3 , preserving heat for 20-50 min, quenching, heating the steel plate to 10-60 ℃ below A c1 , preserving heat for 20-min-60 min, and air cooling and tempering, wherein A c1 is the starting temperature of pearlite to austenite transformation during heating, and A c3 is the finishing temperature of eutectoid ferrite to austenite during heating; According to weight percentage, the chemical components of the 9Ni steel plate comprise 0.04% -0.06% of C, 0.15% -0.35% of Si, 0.50% -0.80% of Mn, 8.5% -9.5% of Ni, less than or equal to 0.004% of P, less than or equal to 0.002% of S, 0.015% -0.045% of Als, and the balance Fe and unavoidable impurity elements, wherein the 9Ni steel plate has the following properties that the yield strength is more than or equal to 590MPa, the tensile strength is more than or equal to 690MPa, the yield ratio is less than or equal to 0.90, the elongation is more than or equal to 19%, the impact energy at-196 ℃ is more than or equal to 100J, the structure of the 9Ni steel plate takes tempered martensite as a matrix, the mixed structure of ferrite and austenite which is not lower than 2.0% of austenite is added, and the thickness of the 9Ni steel plate is 5 mm-50 mm; in the rough rolling process, the initial rolling temperature is 1000-1050 ℃, the rough rolling ending temperature is 970-1000 ℃, in the finish rolling process, the initial rolling temperature is 900-980 ℃, and the finish rolling ending temperature is 800-860 ℃.
2. 2. The method for preparing a 9Ni steel plate according to claim 1, wherein the step of billet smelting comprises the steps of converter-LF refining-VD vacuum treatment-slab continuous casting process to produce thick billets.

Description

9Ni steel plate and preparation method thereof Technical Field The application belongs to the technical field of steel rolling processes, and particularly relates to a 9Ni steel plate and a preparation method thereof. Background Under the great background of building the global ecological community, clean energy strategy is accelerated, and natural gas favored in recent years is taken as the cleanest fossil energy, so that the important role of the natural gas is increasingly highlighted. The liquefied natural gas (Liquefied Natural Gas, LNG for short) has the advantages of convenient storage and transportation, good safety and the like, and occupies more than half of the natural gas trade. The 9Ni steel has higher strength, excellent ultralow-temperature impact toughness at-196 ℃ and good weldability, and is widely applied to various links such as Liquefied Natural Gas (LNG) storage, transportation and use. In order to obtain proper strength and good ultralow temperature toughness, 9Ni steel is subjected to thermal mechanical rolling and then subjected to heat treatment in the forms of double normalizing, tempering, quenching, tempering or quenching, two-phase zone quenching, tempering and the like. The 9Ni steel is mainly used as a liner material of a large land LNG storage tank, a marine LNG fuel tank and an LNG transport ship liquid cargo maintenance system, is directly contacted with the LNG which is at the temperature of minus 162 ℃ and is inflammable and explosive, and has a severe service environment. To ensure a sufficient safety factor, designers have a clear requirement for the yield ratio of the material. However, the yield ratio of the 9Ni steel plate after heat treatment is generally high, and the design requirement of low yield ratio is met with great difficulty. In the prior art, chinese patent CN110229998 discloses a thin-specification 9Ni steel plate with low yield ratio, the thickness of the steel plate is as low as 5mm by adopting a hot rolled coil production process, and the method is matched with an off-line quenching-off-line normalizing-high temperature tempering heat treatment process, and can not completely cover the thickness range of an actual steel plate for supplying only the thin-specification 9Ni steel plate with the thickness of 5 mm. Meanwhile, the heat treatment process is complex, the production efficiency is low, the heat treatment productivity is influenced, and the method has certain limitation relative to batch production. Chinese patent CN114836692 discloses a high nickel steel plate for ship with large compression ratio and low yield ratio and its manufacturing method, which provides a 9Ni steel plate with large reduction and low yield ratio for LNG ship with 10-25 mm thickness and its manufacturing method, and adds a two-phase zone two-time quenching process between normal quenching and tempering heat treatment, so as to reduce alloy elements and impurity elements in ferrite matrix, reduce solid solution strengthening effect of material, and thus reduce yield ratio. The method also does not completely cover the range of thicknesses of the steel sheet actually supplied. And the primary two-phase zone secondary quenching process is added, so that the manufacturing cost and the production efficiency of the steel plate are both affected to a certain extent. Chinese patent CN110541110a discloses a 9Ni steel plate for a high strength low yield ratio ship LNG storage tank and a manufacturing method thereof, and by adding Nb and Cr components in the steel and adopting QLT heat treatment process, the 9Ni steel with good toughness and low yield ratio is obtained. According to the method, the purposes of improving the strength of the 9Ni steel and reducing the yield ratio are achieved by adding alloy elements and adding a one-time quenching mode of an intermediate two-phase region. But also has a certain influence on the manufacturing cost and the production efficiency of the steel plate. In view of the above, in order to solve the above technical problems, a new 9Ni steel and a method for preparing the same are needed. Disclosure of Invention The application provides 9Ni steel and a preparation method thereof, which aim to solve the technical problems of high alloy cost and complex heat treatment process in the existing 9Ni steel production process. In a first aspect, the application provides a 9Ni steel plate, wherein the chemical components of the 9Ni steel plate comprise, by weight, 0.04% -0.06% of C, 0.15% -0.35% of Si, 0.50% -0.80% of Mn, 8.5% -9.5% of Ni, less than or equal to 0.004% of P, less than or equal to 0.002% of S, 0.015% -0.045% of Als, and the balance of Fe and unavoidable impurity elements. Optionally, the 9Ni steel has the following properties that the yield strength is more than or equal to 590MPa, the tensile strength is more than or equal to 690MPa, the yield ratio is less than or equal to 0.90, the elongation is more than or equal to 19%, and the impac