1700MPa-grade maraging stainless steel plate resistant to deep-sea high-pressure abrasion and manufacturing method of 1700MPa-grade maraging stainless steel plate

Abstract

The invention discloses 1700 MPa grade deep sea high pressure abrasion resistant maraging stainless steel and a manufacturing method thereof. The steel comprises the following chemical components in percentage by weight: less than or equal to 0.04% of C, 0.1%-0.3% of Si, 0.1%-0.2% of Mn, less than or equal to 0.003% of P, less than or equal to 0.003% of S, 1.3%-1.5% of Cu, 10.2%-11.5% of Cr, 8.5%-9.4% of Ni, 1%-3% of Mo, 3.2%-4.5% of Co, 0.08%-0.12% of Nb, 1%-1.5% of Ti, 0.1%-0.3% of Al and the balance of Fe and inevitable impurity elements. According to the steel plate, the yield strength is larger than or equal to 1700 MPa, the tensile strength is larger than or equal to 1900 MPa, the hardness is larger than or equal to 54 HRC, the pitting potential is larger than or equal to 2.4 Vsec, the abrasion weight loss in the 30 MPa deep sea environment is smaller than or equal to 0.05 g / h, and meanwhile the steel plate has the excellent strength, hardness, corrosion resistance and abrasion resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of deep-sea marine steel manufacturing, and particularly relates to a 1700MPa-grade deep-sea high-pressure abrasion-resistant martensite-ageing stainless steel plate and a manufacturing method. BACKGROUND

[0002] Deep-sea resource development covers multiple links such as underwater exploration, engineering construction, oil and gas production, mineral exploitation and resource transportation; the prerequisite for realizing efficient development of deep-sea resources is to have reliable equipment suitable for deep-sea underwater operation. Since it takes a very long time and costs a very high cost to recover several tons of equipment from several kilometers of seabed to the sea surface for maintenance or replacement, the reliability and super-long service life of the equipment and its key components become the primary design requirements.

[0003] In the process of deep-sea oil and gas pipeline laying, deep-sea mineral conveying pipeline installation, combustible ice exploitation, mooring anchor twisting operation and super-water-depth power and communication cable construction, the plow excavating mechanism of the plow of the laying equipment such as the deep-sea subsea pipeline plow trencher will rub and collide with the seabed sediments. These sediments usually have very high hardness and are mixed with rough basalt debris and sand particles, resulting in strong abrasive wear. Mechanical wear will continuously remove the protective coating or passivation film on the surface of the material, exposing the active metal matrix directly to the corrosion environment. As a strong electrolyte medium, seawater can cause various corrosion behaviors such as chloride ion corrosion and electrochemical corrosion, and material corrosion will further aggravate wear, forming a vicious cycle of wear-corrosion. In addition, in the deep-sea environment of several kilometers, the equipment continuously bears tens of megapascals of high hydrostatic pressure, further increasing the risk of stress corrosion. Therefore, the deep-sea equipment material suitable for this environment must have very high strength, high hardness and excellent corrosion resistance to cope with multiple failure mechanisms under extreme conditions.

[0004] Patent application No. 202510712696.9 discloses a high-strength martensite-ageing stainless steel with a multi-stage ageing process, its preparation method and application. The high-strength martensite-ageing stainless steel produced has a tensile strength of 1932MPa-2301MPa, a yield strength of 1755MPa-2156MPa, and a hardness of 556HV-633HV. The Cr content of this method is controlled at 12%-18%, which is too high and is within the ferrite and martensite phase range of the Schaeffler phase diagram, which will cause a decrease in material strength. In addition, this method uses a cold rolling and multi-stage ageing production process to produce high-strength martensite-ageing stainless steel, which has a complex production process and low efficiency, and is significantly different from the present method.

[0005] Patent application number 202410012617.9 discloses a high-strength, high-toughness, and corrosion-resistant martensitic aging stainless steel and its preparation method. The martensitic precipitation-aging stainless steel obtained has a tensile strength and hardness exceeding 1900 MPa and 52 HRC, respectively, and its elongation, reduction of area, and impact toughness are significantly improved, exceeding 15%, 50%, and 60 J / mm, respectively. 2 This method combines the advantages of low preparation cost, high strength, high yield strength ratio, good toughness, and high corrosion resistance. The Ni content in this method is controlled at 9.5%-10.5%; excessively high content will increase the content of retained austenite in the steel, thus affecting the material's strength. Furthermore, this method involves cold rolling the steel plate at 20℃~300℃ for 5%~15% deformation, followed by cryogenic treatment and 2-3 aging treatments to achieve excellent mechanical properties. This method involves multiple heating of the steel plate, resulting in high energy consumption and low production efficiency, which is significantly different from this method. Summary of the Invention

[0006] The purpose of this invention is to provide a 1700MPa grade deep-sea high-pressure abrasion resistant martensitic aging stainless steel and its manufacturing method, which has a yield strength ≥1700MPa, tensile strength ≥1900MPa, hardness ≥54HRC, pitting potential ≥2.4Vsec, and a weight loss of ≤0.05g / h in a 30MPa deep-sea environment. It also has excellent strength, hardness, corrosion resistance and abrasion resistance.

[0007] To achieve the above objectives, the present invention employs the following technical solution: A 1700MPa grade deep-sea high-pressure abrasion-resistant martensitic aging stainless steel has the following chemical composition by weight percentage: C≤0.04%, Si: 0.1%~0.3%, Mn: 0.1%~0.2%, P≤0.003%, S≤0.003%, Cu: 1.3%~1.5%, Cr: 10.2%~11.5%, Ni: 8.5%~9.4%, Mo: 1%~3%, Co: 3.2%~4.5%, Nb: 0.08%~0.12%, Ti: 1%~1.5%, Al: 0.1%~0.3%, with the balance being Fe and unavoidable impurity elements.

[0008] The roles and scope of the main alloying elements in this invention are explained below: Carbon (C): In martensitic aging stainless steel, carbon exists as an impurity element in the matrix. When the carbon content is too high, it will form carbides. If the size of these carbides is too large, it will seriously deteriorate the toughness and corrosion resistance of the steel. In addition, carbon can form intergranular precipitates with chromium (Cr), promoting Cr depletion and reducing the corrosion resistance of the material. Considering the cost of decarburization treatment in the smelting process, the carbon content in this invention is controlled below 0.04%.

[0009] Silicon (Si): Si is one of the important elements in martensitic aging stainless steel. Si can react with oxygen in molten steel to form oxide inclusions such as SiO2, reducing the oxygen content and improving the purity of the material. The synergistic addition of low-diffusion elements such as Si and Mo can reduce the precipitation kinetics of precipitates, preventing coarsening of the precipitates. Si can also effectively inhibit the precipitation and growth of carbides in the martensitic matrix during tempering, thus preventing the formation of Cr-depleted zones and reducing corrosion resistance. However, excessive Si content can lead to the formation of brittle phases, reduced grain boundary bonding, and severe damage to the material's plasticity. Considering all factors, the mass percentage of Si should be controlled between 0.1% and 0.3%.

[0010] Manganese (Mn): In martensitic aging stainless steel, Mn mainly participates in the precipitation of nanophases, forming Ni(Mn, Ti, Mo) intermetallic compounds. Therefore, it can replace Ti and Mo elements in small amounts, reducing costs. However, excessively high Mn content can lead to severe material segregation, reduced weldability, and increased internal stress. Taking all factors into consideration, the mass percentage of Mn should be controlled between 0.1% and 0.2%.

[0011] Phosphorus (P): Phosphorus is a harmful impurity element in martensitic aging stainless steel. To ensure the mechanical properties of the material, the content of phosphorus should be kept as low as possible while considering production costs, and the phosphorus content should be controlled to ≤0.003%.

[0012] Sulfur (S): Sulfur is a harmful impurity element in martensitic aging stainless steel. To ensure the mechanical properties of the material, the content of sulfur should be kept as low as possible while considering production costs, and the sulfur content should be controlled to ≤0.003%.

[0013] Copper (Cu): In martensitic aging stainless steel, Cu can form a Cu-rich phase, thus strengthening the steel. It can also accelerate the precipitation of Ni-rich strengthening phases. In the early stages of aging of Cu-containing martensitic aging stainless steel, it first forms particle-rich clusters, which serve as nucleation sites for precipitates in the subsequent age-hardening process. However, excessive Cu content can cause copper embrittlement during hot working. Considering all factors, the Cu mass percentage should be controlled between 1.3% and 1.5%.

[0014] Chromium (Cr): Cr is a crucial element in martensitic aging stainless steel. To ensure the corrosion resistance of stainless steel, its mass percentage generally needs to be greater than 10%. However, Cr is a ferrite-forming element, and excessively high Cr content can reduce the material's strength. The Cr content must be determined by comprehensively considering corrosion resistance and ensuring that the Ni and Cr equivalents are within the martensitic phase region of the Schaeffler phase diagram. Therefore, the mass percentage of Cr should be controlled between 10.2% and 11.5%.

[0015] Nickel (Ni): Ni is an important element in the formation of intermetallic compounds in martensitic aging stainless steel. In the early stages, it strengthens the matrix by forming Ni(Ti, Mn) and Ni3(Ti, Mo), with Ni3(Ti, Mo) also serving as the nucleation core for Mo-rich phases. Additionally, Ni strengthens the matrix, providing a certain degree of ductility and toughness to the stainless steel; Ni also improves the hardenability of martensite. However, Ni is an austenite-forming element; excessive Ni content can lead to the formation of retained austenite, thus affecting the strength of the stainless steel. Furthermore, the Ni content must be carefully considered, taking into account corrosion resistance and ensuring that the Ni and Cr equivalents are within the martensitic phase region of the Schaeffler phase diagram. Considering all factors, the Ni mass percentage should be controlled between 8.5% and 9.4%.

[0016] Mo (Mo): In martensitic aging stainless steel, Mo plays a role in solid solution strengthening. Furthermore, Mo is one of the main elements forming the Mo-rich phase and Ni3(Ti,Mo). The Mo-rich phase, formed over a long aging period, encapsulates Ni3Ti to form a fine, dispersed core-shell structure, effectively improving strength. Mo is also an effective corrosion-resistant element; its addition synergistically improves the corrosion resistance of the material with Cr. Cr mainly limits the dissolution of the anolyte metal by forming a stable oxidation state, while Mo can reduce the cathode reaction rate and decrease harmful reactions such as hydrogen evolution. The interaction between Mo and Cr improves the overall corrosion resistance of the material. In addition, Mo is a ferrite-forming element; excessively high Mo content increases the precipitation tendency of δ-ferrite, raising its content and deteriorating the material's performance. Considering all factors, the mass percentage of Mo should be controlled between 1% and 3%.

[0017] Cobalt (Co): The addition of Co can improve the mechanical properties of martensitic aging stainless steel. Co interacts with Mo, reducing the nucleation energy of Mo-rich phase precipitation, resulting in finer and more uniformly distributed Mo-rich precipitates in the martensitic matrix, thus increasing strength. Simultaneously, Co can hinder dislocation recovery, reduce precipitate size, and stabilize the martensitic matrix, thereby improving the level of secondary hardening. However, Co is expensive, and excessive addition will significantly increase the cost of steel plates. Considering all factors, the mass percentage of Co should be controlled between 3.2% and 4.5%.

[0018] Niobium (Nb): The addition of Nb can produce precipitation strengthening in the matrix, improve strength, and give the matrix good resistance to tempering softening. However, excessive niobium addition may lead to the formation of chain-like primary carbides, which will negatively affect the properties of martensitic aging stainless steel. Taking all factors into consideration, the mass percentage of Nb should be controlled between 0.08% and 0.12%.

[0019] Titanium (Ti): Ti is the main strengthening phase-forming element in martensitic aging stainless steel. In the early stages, it can form Ni-Ti clusters, preparing for the precipitation of subsequent strengthening phases. When the Ti content is too high, the tendency for precipitates to form at the martensite lath boundaries increases. When there is too much precipitate at the martensite lath boundaries, it is very easy for it to evolve into crack initiation sites and propagate along the martensite lath interface, initiating quasi-cleavage cracking. Taking all factors into consideration, the mass percentage of Ti should be controlled between 1% and 1.5%.

[0020] Aluminum (Al): Al is a key age-hardening element in martensitic aging stainless steel. On one hand, Al can dissolve in the matrix to produce a certain solid solution strengthening effect; on the other hand, and more importantly, during the aging process, Al combines with Ni to form nanoscale Ni3Al intermetallic compounds, producing a significant precipitation strengthening effect, which is the main source of the material's ultra-high strength. Furthermore, as a ferrite-forming element, Al helps to obtain a fully martensitic structure after solution treatment, avoiding the adverse effects of retained austenite on performance. Al can also promote the formation of a denser surface passivation film, synergistically enhancing the material's oxidation resistance with Cr. Considering all factors, the mass percentage of Al should be controlled between 0.1% and 0.3%.

[0021] Improving the resistance to high-pressure abrasion in deep-sea environments hinges on simultaneously enhancing the material's strength, hardness, and corrosion resistance. This invention addresses this by adding intermetallic compound-forming elements such as Ni, Ti, Nb, Al, Cu, and Mo. Through heat treatment, it forms nano-sized Ni3Ti, Ni3Nb, and Ni3Al precipitates and a synergistically strengthened precipitate system composed of nano-clusters of Cu and Mo, thereby improving the matrix strength and hardness through precipitation strengthening. Furthermore, it utilizes Cu, Co, and Mo to increase the pitting potential, enhancing the corrosion resistance of martensitic aging stainless steel. The steel plate of this invention exhibits a yield strength ≥1700 MPa, tensile strength ≥1900 MPa, hardness ≥54 HRC, pitting potential ≥2.4 Vsec, and a weight loss of ≤0.05 g / h during abrasion in a 30 MPa deep-sea environment.

[0022] A method for manufacturing 1700MPa grade deep-sea high-pressure abrasion-resistant martensitic aging stainless steel, the specific method including: 1) Vacuum induction melting: Smelting is carried out according to the composition range of the present invention, and a vacuum induction melting furnace is used for melting. After the design composition requirements are met, the steel ingot is cast to obtain steel ingot.

[0023] 2) Vacuum self-consumption remelting: The steel ingot is remelted by vacuum self-consumption remelting and then cast.

[0024] 3) High-temperature homogenization treatment of billet: Heating in air atmosphere, the heating method is furnace heating, the heating rate is 80-100℃ / h, holding at 600~900℃ (T1) for 4~8h (t1), then heating to 1200~1300℃ (T2) and holding for 10~20h (t2), and then oil cooling to room temperature.

[0025] 4) Rolling: The homogenized billet is heated to 1200℃~1300℃ (T3) and held for 2-4 hours (t3) before rolling. The initial rolling temperature is 1100~1200℃ (T4) and the final rolling temperature is 1000~1100℃ (T5). The rolling reduction is ≥60%. After rolling, the billet is air-cooled to room temperature.

[0026] 5) Solution treatment and aging heat treatment: Solution treatment is carried out at 1050~1100℃ (T6), and the temperature is held for 1-2 hours (t4). Then, the solution is quenched and cooled in an ice-water mixture at 0℃. The aging treatment temperature is 400~450℃ (T7), and the aging time is 3-6 hours (t5). After aging, the solution is air-cooled to room temperature.

[0027] The purpose of solution treatment between 1050 and 1100℃ is to completely dissolve all precipitation strengthening elements (such as Cu, Ni, Mo, Nb, etc.) into austenite, resulting in a homogeneous single microstructure. Rapid quenching in 0℃ ice water then yields a single, high-dislocation-density supersaturated lath martensite matrix. During aging treatment at 400–450℃, due to the relatively low tempering temperature, the precipitated nanoscale intermetallic compounds are finer, and the internal dislocations in the matrix do not largely disappear due to recovery, further restricting dislocation movement and increasing the matrix yield strength. This is the fundamental reason why the material strength is increased to the 1700 MPa level.

[0028] Compared with the prior art, the beneficial effects of the present invention are: 1) Compared with other high-strength stainless steels, the precious metal content in this invention is lower and the raw material cost is less.

[0029] 2) The preparation method of this invention is simple, the process is highly controllable, and it is easy to realize industrial production.

[0030] 3) The martensitic aging stainless steel produced by this invention has excellent strength, hardness, corrosion resistance and wear resistance, and is suitable for deep-sea abrasive environments. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below with reference to the examples. The following examples are used to specifically illustrate the content of the present invention. These examples are only general descriptions of the content of the present invention and do not limit the content of the present invention.

[0032] Table 1 shows the chemical composition of the steel in the embodiments of the present invention; Table 2 shows the rolling and heat treatment process parameters of the steel in the embodiments of the present invention; Table 3 shows the mechanical and corrosion resistance properties of the steel in the embodiments of the present invention.

[0033] Table 1. Chemical composition (wt%) of the steel plate in the embodiments of the present invention Table 2 Rolling and heat treatment process parameters of steel in the embodiments of the present invention Table 3 Mechanical and corrosion resistance properties of the steel in the embodiments of the present invention As can be seen from the data in Tables 1, 2 and 3, the martensitic aging stainless steel plate prepared by the technical solution adopted in this invention has a yield strength ≥1700MPa, tensile strength ≥1900MPa, hardness ≥54HRC, pitting potential ≥2.4Vsec, and a weight loss of ≤0.05g / h in a 30MPa deep-sea environment. It also has excellent strength, hardness, corrosion resistance and abrasion resistance, and its performance fluctuates little within the entire process window.

Claims

1. A 1700MPa grade deep-sea high-pressure abrasion-resistant martensitic aging stainless steel, characterized in that the chemical composition of the steel, by weight percentage, is: C≤0.04%, Si: 0.1%~0.3%, Mn: 0.1%~0.2%, P≤0.003%, S≤0.003%, Cu: 1.3%–1.5%, Cr: 10.2%–11.5%, Ni: 8.5%–9.4%, Mo: 1%–3%, Co: 3.2%–4.5%, Nb: 0.08%–0.12%, Ti: 1%–1.5%, Al: 0.1%–0.3%, with the balance being Fe and unavoidable impurity elements.

2. The 1700MPa grade deep-sea high-pressure abrasion-resistant martensitic aging stainless steel according to claim 1, characterized in that, The steel plate has a yield strength ≥1700MPa, tensile strength ≥1900MPa, hardness ≥54HRC, pitting potential ≥2.4Vsec, and abrasion weight loss ≤0.05g / h in a 30MPa deep-sea environment.

3. A method for manufacturing 1700MPa grade deep-sea high-pressure abrasion-resistant martensitic aging stainless steel as described in claim 1 or 2, characterized in that, Specific methods include: 1) High-temperature homogenization treatment of billet: Heating in air atmosphere at a heating rate of 80-100℃ / h, holding at 600-900℃ for 4-8h, then heating to 1200-1300℃ and holding for 10-20h, then oil cooling to room temperature; 2) Rolling: After heating the homogenized billet to 1200℃~1300℃ and holding it for 2-4 hours, rolling begins. The initial rolling temperature is 1100~1200℃ and the final rolling temperature is 1000~1100℃. The rolling reduction is ≥60%. After rolling, air cool to room temperature. 3) Solution treatment and aging heat treatment: Solution treatment is performed at 1050~1100℃, and after holding at this temperature for 1-2 hours, the mixture is quenched and cooled in an ice-water mixture at 0℃; the aging treatment temperature is 400~450℃, and the aging time is 3-6 hours. After aging, the mixture is air-cooled to room temperature.

4. The method for manufacturing a 1700MPa grade deep-sea high-pressure abrasion-resistant martensitic aging stainless steel according to claim 3, characterized in that, Molten steel is smelted in a vacuum induction furnace.

5. The method for manufacturing a 1700MPa grade deep-sea high-pressure abrasion-resistant martensitic aging stainless steel according to claim 3, characterized in that, The ingots obtained by pouring molten steel are then remelted through vacuum consumable melting and cast into billets.

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