Super13Cr stainless steel 80KSI-grade quenched and tempered bar for oil gas as well as production method and application of Super13Cr stainless steel 80KSI-grade quenched and tempered bar

Abstract

The invention belongs to the technical field of stainless steel on-line heat treatment, and particularly relates to a Super13Cr stainless steel 80KSI-grade quenched and tempered bar for oil gas and a production method and application thereof.The quenched and tempered bar is controlled to be smaller than or equal to 0.50 wt% of V, smaller than or equal to 0.10 wt% of Co, smaller than or equal to 0.10 wt% of Cu, smaller than or equal to 0.01 wt% of Nb, smaller than or equal to 0.03 wt% of N and smaller than or equal to 0.05 wt% of C + N. During preparation of the quenched and tempered bar, the bar is sequentially subjected to austenitizing treatment, water-cooling quenching, primary tempering and secondary tempering, and during water-cooling quenching, the quenching temperature is controlled to be smaller than or equal to 0.20 DEG C, and during secondary tempering, the quenching temperature is controlled to be smaller than or equal to the austenitized bar is placed in continuously flowing cooling water to be subjected to dip quenching, and the water outlet temperature of the bar is smaller than or equal to 200 DEG C; during primary tempering, the heat preservation temperature is 10-60 DEG C higher than that of secondary tempering, and the temperature of the secondary tempering is not higher than 650 DEG C. And finally, the obtained Super 13Cr 80KSI-grade quenched and tempered bar is stable in performance and meets the use requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of online heat treatment of stainless steel, and in particular relates to a Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas, and a production method and application thereof. Background Art

[0002] Super13Cr, composed primarily of chromium (Cr), nickel (Ni), and molybdenum (Mo), is a high-strength, highly corrosion-resistant, ultra-low-carbon martensitic stainless steel. Its grade code is generally 13-5-2 (the first digit represents the nominal chromium content; the second digit represents the nominal nickel content; the third digit represents the nominal molybdenum content). Due to its excellent corrosion resistance and superior physical and chemical properties, the material is widely used in a variety of applications. Under NACE MR0175 (ANSI / NACE MR0175 / ISO 15156-1:2015) and API 6A standards, Super13Cr is primarily used in the manufacture of critical equipment in the oil and gas industry. The 95 KSI strength grade is approved for NACE MR0175 applications, making it a key material for completion tools. Its primary application is in environments containing carbon dioxide, chlorides, and low concentrations of hydrogen sulfide. These equipment must operate under extreme temperatures and pressures and are frequently exposed to corrosive environments, requiring excellent corrosion resistance and high strength. In the API 5CRA standard, 80KSI of Super13Cr material can be used in casing, tubing, and accessory materials (including coupling materials and rods for accessories). The product has two levels of delivery conditions, namely PSL-1 (standard basic requirements) and PSL-2 (additional requirements for corrosion and crack resistance products involved in specific environments and certification methods). At the manufacturer's option, PSL-2 products can be provided in place of PSL-1.

[0003] Currently, 80KSI is still not widely adopted because achieving the required hardness is difficult. Existing production methods cannot consistently produce the required material, and most production is done through sorting of finished materials. Because the tempering temperature for 80KSI material approaches the phase transition point, excessive alloying elements in the material can prevent the 80KSI requirement from being achieved. However, smelting metal materials using vacuum induction or electric furnaces is prohibitively expensive. Furthermore, smelting using alloys and return materials is difficult to guarantee material quality.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas, and a production method and application thereof, so as to solve the problem that the hardness of Super13Cr stainless steel 80KSI is difficult to control.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, a method for producing Super13Cr stainless steel 80KSI grade quenched and tempered material for oil and gas use comprises:

[0008] S1. According to the chemical composition of Super13Cr stainless steel for oil and gas, the raw materials are subjected to electric furnace primary refining, LF refining, vacuum degassing, die casting, annealing or hot-feeding, heating, forging or rolling, annealing and finishing in sequence to obtain Super13Cr stainless steel bars;

[0009] Wherein, in the raw materials, V≤0.50wt%, Co≤0.10wt%, Cu≤0.10wt%, Nb≤0.01wt%, and after the vacuum degassing, N≤0.03wt% and C+N≤0.05wt% are controlled;

[0010] S2, sequentially subjecting the Super13Cr stainless steel bar to an austenitizing treatment and a quenching and tempering treatment, wherein the quenching and tempering treatment comprises sequentially water-cooling quenching, primary tempering, and secondary tempering to obtain a Super13Cr stainless steel 80KSI grade quenched and tempered bar;

[0011] Wherein, during the water-cooling quenching, the austenitized Super13Cr stainless steel bar is placed in continuously flowing cooling water for immersion quenching, and the outlet water temperature of the Super13Cr stainless steel bar is ≤200°C;

[0012] The holding temperature of the primary tempering is 10-60°C higher than the holding temperature of the secondary tempering, and the holding temperature of the secondary tempering is not higher than 650°C.

[0013] Furthermore, during the LF refining to die casting process, the ladle is protected by argon instead of nitrogen.

[0014] And / or, in the raw materials, V≤0.20wt%, Co 0-0.05wt%, Cu 0-0.08wt%, Nb 0-0.008wt%;

[0015] and / or, during the water-cooling quenching, the outlet water temperature of the Super13Cr stainless steel bar is ≤150° C.;

[0016] And / or, the austenitizing temperature is 900-980° C., and the austenitizing holding time is: (2h / 100mm*D)-(2h / 100mm*D+5h), where h represents hours, and D represents the diameter of the Super13Cr stainless steel bar in the black skin state, in mm;

[0017] And / or, during the water-cooling quenching, the water inlet temperature of the Super13Cr stainless steel bar is ≥850°C;

[0018] And / or, the Super13Cr stainless steel bar is filled with water within 2 minutes after being austenitized and taken out of the furnace.

[0019] Furthermore, the outlet water temperature of the Super13Cr stainless steel bar is ≤80°C;

[0020] And / or, the Super13Cr stainless steel bar is filled with water within 1 minute after being austenitized and taken out of the furnace.

[0021] Furthermore, during the water-cooling quenching, the flow rate of the cooling water is 250-1000m 3 / h.

[0022] Furthermore, during the water-cooling quenching, the cooling water is circulated and used as circulating water during the water-cooling quenching.

[0023] Furthermore, the circulating water is used for water-cooling quenching after removing impurities, and the impurity removal includes removing oil stains, oxide scales, and suspended solid impurities.

[0024] Furthermore, the holding temperature of the primary tempering is 25 to 50° C. higher than the holding temperature of the secondary tempering;

[0025] And / or, the holding temperature of the primary tempering is 550-700°C;

[0026] And / or, the holding temperature of the secondary tempering is 500-650°C.

[0027] Furthermore, the holding temperature of the primary tempering is 550-645° C., and the holding time is (4h / 100mm*D)-(4h / 100mm*D+5h), wherein h represents hours, and D represents the diameter of the Super13Cr stainless steel bar in the black skin state, in mm;

[0028] And / or, in the primary tempering, air cooling is performed after heat preservation to release quenching stress;

[0029] And / or, the holding temperature of the secondary tempering is 500-610° C., and the holding time is (4h / 100mm*D)-(4h / 100mm*D+5h), wherein h represents hours, and D represents the diameter of the Super13Cr stainless steel bar in the black skin state, in mm;

[0030] And / or, straightening is performed before the secondary tempering to remove deformation of the bar caused by water quenching, and air cooling is performed after heat preservation during the secondary tempering to release straightening stress.

[0031] In a second aspect, a Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas use is produced using the production method described in the first aspect;

[0032] The Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas includes the following chemical components by mass fraction: C≤0.05%, Si≤0.50%, Mn≤1.00%, P≤0.02%, S≤0.005%, Ni 4.5-6.5%, Cr 11.5-15.0%, Mo 1.5-3.0%, Ti≤0.05%, V≤0.50%, Co≤0.10%, Cu≤0.10%, Nb≤0.01%, N≤0.03%, C+N≤0.05%, and the remainder is Fe and unavoidable impurities.

[0033] In a third aspect, a corrosion-resistant alloy seamless product is made of the Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas produced by the production method described in the first aspect or the Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas described in the second aspect.

[0034] The present invention has at least the following beneficial effects:

[0035] The present invention provides a method for producing Super13Cr stainless steel 80KSI grade quenched and tempered bars for oil and gas. The prepared Super13Cr (13-5-2) 80KSI grade quenched and tempered bars have stable performance, meet use requirements, do not generate waste, do not require material selection and procurement, have a large surplus, and can be used as PSL-2 products. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The grain map (100x 5-level grain size) of UNS S41426 80KSI steel obtained in Example 1 of the present invention;

[0037] Figure 2 The grain map of UNS S41426 80KSI steel obtained in Example 1 of the present invention (500x 5-level grain size);

[0038] Figure 3The grain map (100x 5-level grain size) of UNS S41427 80KSI steel obtained in Example 2 of the present invention;

[0039] Figure 4 This is the grain map (500x 5-level grain size) of UNS S41427 80KSI steel obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. The process parameters for which specific conditions are not specified in the following examples are generally in accordance with conventional conditions.

[0041] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0042] According to a first aspect of the present invention, a method for producing Super 13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas use comprises:

[0043] S1. According to the chemical composition of Super13Cr stainless steel for oil and gas, the raw materials are subjected to electric furnace primary refining, LF refining, vacuum degassing, die casting, annealing or hot-feeding, heating, forging or rolling, annealing and finishing in sequence to obtain Super13Cr stainless steel bars;

[0044] Wherein, in the raw materials, V≤0.50wt%, Co≤0.10wt%, Cu≤0.10wt%, Nb≤0.01wt%, and after the vacuum degassing, N≤0.03wt% and C+N≤0.05wt% are controlled;

[0045] S2, sequentially subjecting the Super13Cr stainless steel bar to an austenitizing treatment and a quenching and tempering treatment, wherein the quenching and tempering treatment comprises sequentially water-cooling quenching, primary tempering, and secondary tempering to obtain a Super13Cr stainless steel 80KSI grade quenched and tempered bar;

[0046] Wherein, during the water-cooling quenching, the austenitized Super13Cr stainless steel bar is placed in continuously flowing cooling water for immersion quenching, and the outlet water temperature of the Super13Cr stainless steel bar is ≤200°C;

[0047] The holding temperature of the primary tempering is 10-60°C higher than the holding temperature of the secondary tempering, and the holding temperature of the secondary tempering is not higher than 650°C.

[0048] The present invention provides a method for producing an 80KSI grade quenched and tempered Super13Cr stainless steel bar for oil and gas, wherein the total content of corresponding elements is controlled during steelmaking, wherein N is less than or equal to 0.03wt% (e.g., 0.03wt%, 0.02wt%, 0.01wt%, 0), C+N is less than or equal to 0.05wt% (e.g., 0.05wt%, 0.04wt%, 0.03wt%, 0.02wt%, 0.01wt%, 0), V is less than or equal to 0.50wt% (e.g., 0.50wt%, 0.40wt%, 0.30wt%, 0.20wt%, 0.10wt%, 0), Co is less than or equal to 0.10wt% (e.g., 0.10wt%, 0.09wt%, 0.08wt%, 0.07wt%, 0.06wt%, 0.05wt%), and Cu is less than or equal to 0.1wt%. t%, 0.04wt%, 0.03wt%, 0.02wt%, 0.01wt%, 0), Cu≤0.10wt% (such as 0.10wt%, 0.09wt%, 0.08wt%, 0.07wt%, 0.06wt%, 0.05wt%, 0.04wt%, 0.03wt%, 0.02wt%, 0.01wt%, 0), Nb≤0.01wt% (such as 0.01wt%, 0.009wt%, 0.008wt%, 0.007wt%, 0.006wt%, 0.005wt%, 0.004wt%, 0.003wt%, 0.002wt%, 0.001wt%, 0), so that the hardness of the steel after tempering meets the 80KSI grade requirement. Among them, the total content of V, Co, Cu and Nb must be controlled when the raw materials are prepared. They must not exceed the corresponding upper limit to avoid excessive residual amounts after steelmaking. The content of N and C+N must ensure that their corresponding contents do not exceed the upper limit after vacuum degassing. Because the phase transition point of Super13Cr is around 650℃, the tempering temperature is generally carried out below the phase transition point. The basic quenching strength of Super13Cr is very high. If the elements that increase the hardness are not controlled, the technical requirement of 80KSI cannot be achieved even if the tempering temperature is raised to 650℃.

[0049] In addition, the production method of the present invention uses water as the medium for immersion quenching during tempering. While the cooling water continuously flows through the surface of the bar to continuously exchange heat and remove heat, the water outlet temperature of the bar is controlled to be ≤200°C (such as 200°C, 180°C, 160°C, 140°C, 120°C, 100°C, 80°C, 60°C, 40°C, 20°C, etc.), ensuring that the material is fully quenched while meeting the performance requirements, preventing material cracking, and adjusting the yield strength. The process of the present invention can deliver 80KSI grade UNS S41426, UNS S41427, and other 13-5-2 materials, with performance and microstructure that meet the use requirements. Moreover, immersion quenching can process large quantities of steel bars, avoiding the problem of spray quenching that can only process single bars or small quantities of bars, and the fact that the steel bars must be rotated during spray quenching to ensure uniform contact with water, and the presence of air contact with the steel bars may affect cooling.

[0050] In the present invention, cooling water can be common fresh water, including hard or soft water, such as purified water, tap water, deionized water, distilled water, etc., or recycled treated wastewater or recycled water. Inexpensive industrial water is preferred for low production costs. Cooling water can generally be used directly at room temperature to begin water-cooling quenching, without the need for specialized cooling or heating treatment. Maintaining continuous water flow throughout the quenching process ensures stable material transformation and the absence of retained austenite.

[0051] As an optional embodiment of the production method of the present invention, the cooling water is circulated as circulating water during water-cooling quenching; further, the circulating water is used for water-cooling quenching after impurities are removed, and further, the impurity removal includes removing impurities such as oil, oxide scale, and suspended solids.

[0052] In the above technical solution, cooling water is recycled as circulating water during water-cooled quenching, which not only ensures that the cooling water is in a continuous flow state during water-cooled quenching, but also saves water. However, the circulating water should be clean water. Before using the circulating water for water-cooled quenching, it is important to filter and clean it to remove impurities such as oil, scale, suspended solids, etc., because the presence of these impurities can seriously affect the cooling effect of the circulating water and may even cause equipment blockage and damage. Therefore, filtering and cleaning the circulating water and removing impurities can ensure clean water quality, extend the service life of equipment, and improve production efficiency.

[0053] As an optional embodiment of the production method of the present invention, during the LF refining to die casting, the ladle is protected by argon gas instead of nitrogen gas, thereby ensuring the nitrogen content in the steel and preventing nitrogen in the nitrogen gas from being absorbed into the molten steel.

[0054] As an optional embodiment of the production method of the present invention, the raw materials include V≤0.20wt%, Co 0-0.05wt%, Cu 0-0.08wt%, and Nb 0-0.008wt%. For the present invention, when adding raw materials, Co, Cu, and Nb are not actively added, and their contents are controlled to be as low as possible.

[0055] As an optional embodiment of the production method of the present invention, during the water-cooling quenching, the water outlet temperature of the Super13Cr stainless steel bar is ≤150°C (such as 150°C, 130°C, 110°C, 90°C, 70°C, 50°C, 30°C, 10°C, etc.), and further, the water outlet temperature of the Super13Cr stainless steel bar is ≤80°C (such as 80°C, 70°C, 60°C, 50°C, 40°C, 30°C, 20°C, 10°C, 0°C, etc.).

[0056] As an optional embodiment of the production method of the present invention, the austenitizing temperature is 900-980°C (such as 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, etc.), and the austenitizing holding time is: (2h / 100mm*D) to (2h / 100mm*D+5h), where h represents hours, and D represents the diameter of the Super13Cr stainless steel bar in the black skin state, mm.

[0057] In the present invention, the Super13Cr stainless steel bar is first austenitized before water quenching, with the austenitization temperature at 900-980°C and a holding time. The austenitized bar can be directly water-quenched, that is, directly placed in water at a furnace temperature of 900-980°C for water cooling. However, in actual operation, the bar needs to undergo a certain time and space transfer after being removed from the furnace. Therefore, the surface of the bar is affected by the environment and the temperature will drop. Moreover, its surface actually has an oxide scale. Therefore, the water inlet temperature of the bar can be controlled based on the oxide scale temperature or the time from the time it is removed from the furnace to the time it is completely filled with water. The latter is preferred and more convenient for actual production on-site operation. Optionally, the water inlet temperature of the Super13Cr stainless steel bar is ≥850°C; further, the Super13Cr stainless steel bar is filled with water within 2 minutes after being removed from the austenitization furnace; further, the Super13Cr stainless steel bar is filled with water within 1 minute after being removed from the austenitization furnace to ensure stable material properties. It is preferred to control the water inlet temperature by controlling the water inlet time, which is convenient for on-site operation in actual production. During on-site operation, it is only necessary to tell the workers to complete the water inlet within one or two minutes. Therefore, in the present invention, the water inlet temperature of the Super13Cr stainless steel bar can be typically but not limited to 850°C, 870°C, 890°C, 910°C, 930°C, 950°C, 970°C, etc., and / or, the Super13Cr stainless steel bar is completed within 110s, 100s, 90s, 80s, 70s, 60s, 50s, 40s, 30s, 25s, 20s, 15s, 10s, 0s, etc. after the austenitization furnace.

[0058] As an optional embodiment of the production method of the present invention, the water flow rate of the cooling water is 250 to 1000 m 3 / h(such as 300m 3 / h、400m 3 / h、500m 3 / h、600m 3 / h、700m 3 / h、800m 3 / h、900m 3 / h, etc.).

[0059] In the above technical solution, by controlling the cooling water flow rate ≥ 250m 3 / h, which can not only avoid water boiling and ensure uniform cooling process from the inside to the outside of the rod, but also achieve precise control of the cooling rate of the rod during water cooling, avoiding stress cracking or grain boundary cracking of the structure; and can also take away the steam film in time to reduce the impact of the steam film. In the present invention, the flow rate can be selected according to the upper limit of the existing equipment to avoid the water pressure from acting on the rod. For example, the water flow rate of the cooling water can be 250 to 1000m 3 / h. When the quenching tank is large and / or the bar is large, a larger water flow rate is used to ensure that the cooling water in the quenching tank submerges the bar.

[0060] As an optional implementation of the production method of the present invention, the holding temperature of the primary tempering is 25-50° C. (such as 30° C., 35° C., 40° C., 45° C., etc.) higher than the holding temperature of the secondary tempering.

[0061] As an optional embodiment of the production method of the present invention, the primary tempering holding temperature is 550-700°C (such as 570°C, 610°C, 650°C, 690°C, etc.), further, the primary tempering holding temperature is 550-645°C (such as 560°C, 580°C, 600°C, 620°C, 640°C, etc.); the holding time is (4h / 100mm*D) to (4h / 100mm*D+5h), where h represents hours, D represents the diameter of the Super13Cr stainless steel bar in the black skin state, mm; and / or, air cooling is performed after holding in the primary tempering to release quenching stress.

[0062] As an optional embodiment of the production method of the present invention, the secondary tempering holding temperature is 500-650°C (such as 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, etc.), further, the secondary tempering holding temperature is 500-610°C; the holding time is (4h / 100mm*D) to (4h / 100mm*D+5h), where h represents hours, and D represents the diameter of the Super13Cr stainless steel bar in the black skin state, mm; and / or, straightening is performed before the secondary tempering to remove bar deformation caused by water quenching, and air cooling is performed after holding in the secondary tempering to release straightening stress.

[0063] As an optional implementation method of the production method of the present invention, the specifications of the Super13Cr stainless steel bar are round steel with a diameter of Φ12 to 310 mm (such as 15 mm, 20 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, etc.).

[0064] As an optional embodiment of the production method of the present invention, the Super13Cr stainless steel bar includes 13-5-2 materials such as UNSS41426 and UNS S41427.

[0065] According to a second aspect of the present invention, a Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas use is produced using the production method described in the first aspect;

[0066] The Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas includes the following chemical components by mass fraction: C≤0.05%, Si≤0.50%, Mn≤1.00%, P≤0.02%, S≤0.005%, Ni 4.5-6.5%, Cr 11.5-15.0%, Mo 1.5-3.0%, Ti≤0.05%, V≤0.50%, Co≤0.10%, Cu≤0.10%, Nb≤0.01%, N≤0.03%, C+N≤0.05%, and the remainder is Fe and unavoidable impurities.

[0067] Furthermore, the Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas includes the following chemical components by mass fraction: C≤0.02%, Si≤0.30%, Mn≤0.50%, P≤0.02%, S≤0.003%, Ni 5.0-5.5%, Cr12.0-13.0%, Mo 1.6-2.2%, Ti≤0.05%, V≤0.20%, Co≤0.05wt%, Cu≤0.08wt%, Nb≤0.008wt%, N≤0.01%, C+N≤0.03%, and the rest is Fe and unavoidable impurities.

[0068] According to the third aspect of the present invention, a corrosion-resistant alloy seamless product is made of the Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas produced by the production method described in the first aspect or the Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas described in the second aspect.

[0069] Furthermore, the corrosion-resistant alloy seamless product includes casing, oil pipe and accessory materials (including coupling materials and rods for making accessories).

[0070] The specific embodiments of the present invention will be further explained below in conjunction with Examples and Comparative Examples:

[0071] Example 1

[0072] This embodiment provides a Super13Cr steel suitable for the oil and gas field, with a production specification of 80KSI steel grade and Φ130mm round steel. The main chemical components of the steel and their contents (wt%) are: C: 0.01%, Si: 0.28%, Mn: 0.40%, P: 0.015%, S: 0.002%, Cr: 12.51%, Ni: 5.19%, Mo: 2.05%, V: 0.08%, Ti: 0.03%, N: 0.006%, Co: 0.03%, Cu: 0.06%, Nb: 0.007%, and the rest are Fe and unavoidable impurities.

[0073] Specifically, the method for manufacturing Super13Cr steel produced in this embodiment includes the following steps:

[0074] S1. Billet Preparation: The raw materials are sequentially subjected to electric furnace smelting, LF refining, VD vacuum degassing (N content is analyzed after vacuum degassing to ensure that N content is ≤0.03%, C+N ≤0.05%, and argon protection rather than nitrogen is used in the ladle throughout the process), die casting, hot feeding, heating, and rolling to produce Super13Cr rolled round steel. The total amount of V in the raw materials is 0.08%, the total amount of Co is 0.03%, the total amount of Cu is 0.06%, and the total amount of Nb is approximately 0.007%. The final rolling temperature is 927°C.

[0075] S2, Annealing: After the material cools to room temperature, it is put into the furnace for annealing. The annealing temperature is set at 630℃. After keeping the temperature for 7 hours, it is taken out of the furnace and air-cooled to eliminate rolling stress.

[0076] S3, finishing: In order to prevent water quenching cracking, the material is finished and flaw detection is carried out, and the defects and cracks in the rolling process are repaired and ground away. After the flaw detection is qualified, it is transferred to the heat treatment line;

[0077] S4, the material is austenitized, the austenite temperature is set to 950 ° C, kept at this temperature for 4 hours, and then taken out of the furnace for quenching;

[0078] S5, water-cooled quenching: open the circulating water, and ensure that the circulating water is filtered and cleaned to remove impurities such as oil, scale, and suspended solids before use. The time from the bar leaving the furnace to the water entering is 45s, and the circulating water flow rate is 260m 3 / h; circulating water temperature before entering the water is 18℃. Circulating water temperature after leaving the water is 26℃. The surface temperature of the steel at the outlet is 76℃.

[0079] S6. Primary tempering: The tempering holding temperature is set to 630°C for 7 hours. After holding, the furnace is taken out of the furnace and air-cooled to complete the primary tempering.

[0080] S7, straightening;

[0081] S8. Secondary tempering: The tempering holding temperature is set at 600°C for 7 hours. After the holding period, the steel is taken out of the furnace and air-cooled to complete the tempering. Super13Cr 80KSI steel is obtained.

[0082] Example 2

[0083] This embodiment provides a Super13Cr steel suitable for the oil and gas field, with a production specification of 80KSI steel grade and Φ250mm round steel. The main chemical components of the steel and their contents (wt%) are: C: 0.01%, Si: 0.28%, Mn: 0.43%, P: 0.013%, S: 0.001%, Cr: 12.21%, Ni: 5.25%, Mo: 1.87%, V: 0.11%, Ti: 0.001%, N: 0.007%, Co: 0.02%, Cu: 0.04%, Nb: 0.003%, and the rest are Fe and unavoidable impurities.

[0084] Specifically, the method for manufacturing Super13Cr steel produced in this embodiment includes the following steps:

[0085] S1. Billet Preparation: The raw materials are sequentially subjected to electric furnace smelting, LF refining, VD vacuum degassing (N content is analyzed after vacuum degassing to ensure that N content is ≤0.03%, C+N ≤0.05%, and argon protection is used in the ladle rather than nitrogen protection throughout the process), die casting, hot-feeding, heating, and forging to produce Super13Cr forged round steel. The total V content in the raw materials is 0.11%, the total Co content is 0.02%, the total Cu content is 0.04%, and the total Nb content is approximately 0.003%. The final forging temperature is 907°C.

[0086] S2, Annealing: After the material cools to room temperature, it is put into the furnace for annealing. The annealing temperature is set at 620℃. After keeping the temperature for 13 hours, it is taken out of the furnace and air-cooled to eliminate rolling stress.

[0087] S3, finishing: In order to prevent water quenching cracking, the material is finished and flaw detection is carried out, and the defects and cracks in the forging process are ground away. After the flaw detection is qualified, it is transferred to the heat treatment line;

[0088] S4, the material is austenitized, the austenite temperature is set to 940 ° C, kept at this temperature for 6 hours, and then taken out of the furnace for quenching;

[0089] S5, water-cooled quenching: open the circulating water, and ensure that the circulating water is filtered and cleaned to remove impurities such as oil, scale, and suspended solids before use. The time from the bar leaving the furnace to the water entering is 35s, and the circulating water flow rate is 270m 3 / h; circulating water temperature before entering the water is 15℃. Circulating water temperature after leaving the water is 26℃. Outlet steel surface temperature is 75℃;

[0090] S6. Primary tempering: The tempering holding temperature is set to 635°C for 13 hours. After holding, the furnace is taken out of the furnace and air-cooled to complete the primary tempering.

[0091] S7, straightening;

[0092] S8. Secondary tempering: The tempering holding temperature is set at 610°C for 13 hours. After holding, the steel is taken out of the furnace and air-cooled to complete the tempering. Super13Cr 80KSI steel is obtained.

[0093] Comparative Examples 1-3

[0094] Comparative Examples 1-3 are comparative experiments of Example 2. The main chemical components of the obtained Φ250 mm round steel and their contents (wt%) are designed to be: C: 0.01%, Si: 0.26%, Mn: 0.43%, P: 0.012%, S: 0.001%, Cr: 12.30%, Ni: 5.62%, Mo: 2.13%, V: 0.11%, Ti: <0.005%, N: 0.043%, Co: 0.12%, Cu: 0.14%, Nb: 0.016%, and the rest are Fe and unavoidable impurities.

[0095] The manufacturing method differs from Example 2 in that: (1) during the process of obtaining the Super13Cr stainless steel bar, V≤0.50wt%, Co≤0.10wt%, Cu≤0.10wt%, and Nb≤0.01wt% were not controlled during the addition of raw materials, and N was not specifically controlled during the VD vacuum degassing. The remaining steps were the same as in Example 1, thereby obtaining the Super13Cr stainless steel bar of the furnace steel. (2) The bars obtained from the furnace steel were subjected to austenitization and tempering treatment as in Comparative Examples 1-3, and the tempering treatment mainly did not use water-cooling quenching with continuously flowing cooling water. Specifically, the following steps are included:

[0096] S1. Billet Preparation: The raw materials are sequentially subjected to electric furnace smelting, LF refining + VD vacuum degassing (without special control for N), die casting, hot-melting, heating, and forging to produce Super13Cr forged round steel; wherein the final forging temperature is 907°C;

[0097] S2, Annealing: After the material cools to room temperature, it is put into the furnace for annealing. The annealing temperature is set at 620℃. After keeping the temperature for 13 hours, it is taken out of the furnace and air-cooled to eliminate rolling stress.

[0098] S3, finishing: In order to prevent water quenching cracking, the material is finished and flaw detection is carried out, and the defects and cracks in the forging process are ground away. After the flaw detection is qualified, it is transferred to the heat treatment line;

[0099] S4, the material is austenitized, the austenite temperature is set to 940 ° C, kept at this temperature for 6 hours, and then taken out of the furnace for quenching;

[0100] S5, water-cooled quenching: Do not use circulating water. Ensure that the cooling water is filtered and cleaned to remove impurities such as oil, scale, and suspended solids before use. The time from the bar leaving the furnace to the water entering is 35 seconds; the water temperature before entering the water is 15°C; the water temperature after leaving the water is 51°C; the surface temperature of the steel at the outlet is 165°C.

[0101] S6. Primary tempering: The tempering holding temperature is set according to Table 1 below, and the holding time is 13 hours. After holding, the furnace is taken out of the furnace and air-cooled to complete the primary tempering.

[0102] Table 1

[0103] project Primary tempering holding temperature (℃) Example 2 635 Comparative Example 1 635 Comparative Example 2 615 Comparative Example 3 650

[0104] S7, straightening;

[0105] S8. Secondary tempering: The tempering holding temperature is set at 610°C for 13 hours. After holding, the steel is taken out of the furnace and air-cooled to complete the tempering. Super13Cr steel is obtained.

[0106] Comparative Example 4

[0107] The main difference from Example 1 is that the material composition is different, and the water-cooling quenching process is also slightly different, as follows:

[0108] The main chemical components of the steel and their contents (wt%) are: C: 0.01%, Si: 0.22%, Mn: 0.47%, P: 0.016%, S: 0.003%, Cr: 12.11%, Ni: 5.42%, Mo: 1.93%, V: 0.16%, Ti: <0.005%, N: 0.053%, Co: 0.13%, Cu: 0.15%, Nb: 0.013%, and the rest are Fe and unavoidable impurities.

[0109] S5, water-cooled quenching: open the circulating water, and ensure that the circulating water is filtered and cleaned to remove impurities such as oil, scale, and suspended solids before use. The time from the bar leaving the furnace to the water entering is 47s, and the circulating water flow rate is 260m 3 / h; circulating water temperature before entering the water is 17℃. Circulating water temperature after leaving the water is 25℃. The surface temperature of the steel plate at the outlet is 81℃.

[0110] The rest of the settings are the same as those in Example 1.

[0111] Comparative Example 5

[0112] The only difference from Example 1 is that the water-cooling quenching process is different, as follows:

[0113] S5, Water-Cooled Quenching: Circulating water is not used. Before use, ensure that the cooling water is filtered and cleaned to remove impurities such as oil, scale, and suspended solids. The time from the bar leaving the furnace to the water entering is 49 seconds. The water temperature is 17°C, the water temperature after exiting the water is 43°C, and the steel surface temperature at the exit is 124°C.

[0114] The rest of the settings are the same as those in Example 1.

[0115] Performance Testing

[0116] 1. Mechanical properties of the Super13Cr steel samples taken at 1 / 2R of the examples and comparative examples were tested with reference to API 5CRA standard. The results are shown in the following table:

[0117]

[0118] As can be seen from the table above, the Super13Cr steel obtained by the method of the present invention can reach the 80KSI strength level. Figure 1 、 Figure 2 As shown in the figure, it can be seen that the grain size is level 5, the grains are uniform, the ferrite is 0, and no defects are seen. The grain size of the UNS S41427 80KSI steel obtained in Example 2 is as follows Figure 3 、 Figure 4 As shown in the figure, it can be seen that the grain size is grade 5, the grains are uniform, the ferrite content is zero, and no defects are observed. However, Super13Cr produced not according to the method of the present invention cannot meet the 80 KSI requirement. For example, UNS S41427 in Comparative Examples 1-3, the material composition is not controlled, and the water quenching is not carried out using a continuous flow of cooling water. The resulting Super13Cr bar room temperature longitudinal yield strength and / or hardness do not meet the 80 KSI requirement. For another example, UNS S41426 in Comparative Examples 4 and 5, the material composition is not controlled and / or the water quenching is not carried out using a continuous flow of cooling water. The resulting Super13Cr bar room temperature longitudinal yield strength and hardness do not fully meet the 80 KSI requirement.

[0119] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for producing Super13Cr stainless steel 80KSI grade quenched and tempered bars for oil and gas, characterized in that: include: S1. According to the chemical composition of Super13Cr stainless steel for oil and gas, the raw materials are subjected to electric furnace primary refining, LF refining, vacuum degassing, die casting, annealing or hot-feeding, heating, forging or rolling, annealing and finishing in sequence to obtain Super13Cr stainless steel bars; Wherein, in the raw materials, V≤0.50wt%, Co≤0.10wt%, Cu≤0.10wt%, Nb≤0.01wt%, and after the vacuum degassing, N≤0.03wt% and C+N≤0.05wt% are controlled; S2, sequentially subjecting the Super13Cr stainless steel bar to an austenitizing treatment and a quenching and tempering treatment, wherein the quenching and tempering treatment comprises sequentially water-cooling quenching, primary tempering, and secondary tempering to obtain a Super13Cr stainless steel 80KSI grade quenched and tempered bar; Wherein, during the water-cooling quenching, the austenitized Super13Cr stainless steel bar is placed in continuously flowing cooling water for immersion quenching, and the outlet water temperature of the Super13Cr stainless steel bar is ≤200°C; The holding temperature of the primary tempering is 10-60°C higher than the holding temperature of the secondary tempering, and the holding temperature of the secondary tempering is not higher than 650°C.

2. The production method according to claim 1, characterized in that During the LF refining to die casting process, the ladle is protected by argon instead of nitrogen throughout the process; And / or, in the raw materials, V≤0.20wt%, Co 0-0.05wt%, Cu 0-0.08wt%, Nb0-0.008wt%; and / or, during the water-cooling quenching, the outlet water temperature of the Super13Cr stainless steel bar is ≤150° C.; And / or, the austenitizing temperature is 900-980° C., and the austenitizing holding time is: (2h / 100mm*D)-(2h / 100mm*D+5h), where h represents hours, and D represents the diameter of the Super13Cr stainless steel bar in the black skin state, in mm; And / or, during the water-cooling quenching, the water inlet temperature of the Super13Cr stainless steel bar is ≥850°C; And / or, the Super13Cr stainless steel bar is filled with water within 2 minutes after being austenitized and taken out of the furnace.

3. The production method according to claim 2, characterized in that: During the water-cooling quenching, the outlet water temperature of the Super13Cr stainless steel bar is ≤80°C; And / or, the Super13Cr stainless steel bar is filled with water within 1 minute after being austenitized and taken out of the furnace.

4. The production method according to claim 1, characterized in that: During the water-cooling quenching, the flow rate of the cooling water is 250-1000m 3 / h.

5. The production method according to claim 1, characterized in that: During the water-cooling quenching, the cooling water is circulated and used as circulating water during the water-cooling quenching.

6. The production method according to claim 5, characterized in that: The circulating water is used for water-cooling quenching after impurities are removed, and the impurity removal includes removing oil stains, oxide scales, and suspended solid impurities.

7. The production method according to claim 1, characterized in that: The holding temperature of the first tempering is 25 to 50° C. higher than the holding temperature of the second tempering; And / or, the holding temperature of the primary tempering is 550-700°C; And / or, the holding temperature of the secondary tempering is 500-650°C.

8. The production method according to claim 7, characterized in that: The holding temperature of the primary tempering is 550-645° C., and the holding time is (4h / 100mm*D)-(4h / 100mm*D+5h), where h represents hours, and D represents the diameter of the Super13Cr stainless steel bar in the black skin state, in mm; And / or, in the primary tempering, air cooling is performed after heat preservation to release quenching stress; And / or, the holding temperature of the secondary tempering is 500-610° C., and the holding time is (4h / 100mm*D)-(4h / 100mm*D+5h), wherein h represents hours, and D represents the diameter of the Super13Cr stainless steel bar in the black skin state, in mm; And / or, straightening is performed before the secondary tempering to remove deformation of the bar caused by water quenching, and air cooling is performed after heat preservation during the secondary tempering to release straightening stress.

9. A Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas, characterized in that: Prepared by the production method according to any one of claims 1 to 8; The Super13Cr stainless steel 80KSI grade quenched and tempered bar for oil and gas includes the following chemical components by mass fraction: C≤0.05%, Si≤0.50%, Mn≤1.00%, P≤0.02%, S≤0.005%, Ni 4.5-6.5%, Cr 11.5-15.0%, Mo 1.5-3.0%, Ti≤0.05%, V≤0.50%, Co≤0.10%, Cu≤0.10%, Nb≤0.01%, N≤0.03%, C+N≤0.05%, and the remainder is Fe and unavoidable impurities.

10. A corrosion-resistant alloy seamless product, characterized in that: The oil and gas Super13Cr stainless steel 80KSI grade quenched and tempered bar is produced by the production method according to any one of claims 1 to 8, or the oil and gas Super13Cr stainless steel 80KSI grade quenched and tempered bar according to claim 9.

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