UNS S41427 stainless steel 110KSI-grade quenched and tempered bar for oil gas as well as preparation method and application of UNS S41427 stainless steel 110KSI-grade tempered bar

Abstract

The invention belongs to the technical field of online heat treatment of stainless steel, and particularly relates to a UNS S41427 stainless steel 110KSI-grade quenched and tempered bar for oil gas and a preparation method and application thereof.According to the preparation method, raw materials are sequentially subjected to electric furnace primary smelting, LF refining, vacuum degassing, die casting, annealing or red conveying, heating, rolling or forging, annealing and finishing according to chemical components of the UNS S41427 stainless steel for the oil gas, and the UNS S41427 stainless steel 110KSI-grade quenched and tempered bar for the oil gas is obtained. A stainless steel bar is obtained; then the bar is sequentially subjected to austenitizing treatment, water-cooling quenching, primary tempering, straightening and secondary tempering, and the 110KSI-grade quenched and tempered bar is obtained; wherein the content of N is controlled to be less than or equal to 0.03 wt% after vacuum degassing; the water-cooling quenching comprises the steps that the bar is placed in continuously flowing cooling water to be subjected to dip quenching, the temperature of the cooling water does not exceed 38 DEG C, and the water outlet temperature of the bar is smaller than or equal to 100 DEG C. The quenched and tempered bar prepared through the method can pass SSC inspection and is high in universality.

Description

Technical Field

[0001] The invention belongs to the technical field of stainless steel online heat treatment, and in particular relates to a UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas, and a preparation method and application thereof. Background Art

[0002] UNS S41427, primarily composed of chromium (Cr), nickel (Ni), nitrogen (N), manganese (Mn), and sulfur (S), is a high-strength, ultra-low-carbon martensitic stainless steel. Due to its high chromium content, UNS S41427 also exhibits excellent corrosion resistance. Its excellent physical and chemical properties have led to its widespread application in various fields. UNS S41427 is primarily used in the manufacture of critical equipment in the oil and gas industry under the NACE MR0175 (ANSI / NACEMR0175 / ISO 15156-1:2015) and API 6A standards. Its 95KSI strength grade is approved for use in NACE MR0175, making it a key material for completion tools. Its primary application is in environments containing carbon dioxide, chlorides, and low concentrations of hydrogen sulfide. Because these equipment must operate under extreme temperature and pressure conditions and is frequently exposed to corrosive environments, it requires both excellent corrosion resistance and high strength.

[0003] UNS S41427110KSI strength grade is also widely used, but only for carbon dioxide environments. It has certain defects and shortcomings, such as:

[0004] 1. Balance between strength and toughness:

[0005] UNS S41427110KSI has higher strength than 95KSI, but the toughness of the material is reduced. Under certain extreme conditions, its toughness may not meet the requirements of specific applications.

[0006] 2. Corrosion resistance limitations:

[0007] Although S41427110KSI has good corrosion resistance, its corrosion resistance is poor in H2S corrosive environment.

[0008] If 110KSI can be used in H2S environments, it can replace UNS S4142795KSI, making it easier for users to select materials and increasing the versatility of the material. In view of this, the present invention is proposed. Summary of the Invention

[0009] The purpose of the present invention is to provide a UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas, and a preparation method and application thereof, so as to solve the problems that the S41427 110KSI bar cannot meet the requirements of NACE MR0175, has poor corrosion resistance, is not included in the NACE MR0175 standard, and has a narrow application range.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] In a first aspect, a method for preparing UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas use comprises:

[0012] S1. According to the chemical composition of UNS S41427 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-sending, heating, rolling or forging, annealing and finishing in sequence to obtain UNS S41427 stainless steel bars;

[0013] wherein, after vacuum degassing, the nitrogen content is controlled to be ≤0.03wt%;

[0014] S2, sequentially subjecting the UNS S41427 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, straightening, and secondary tempering to obtain a UNS S41427 stainless steel 110KSI grade quenched and tempered bar;

[0015] During the water-cooling quenching, the austenitized UNS S41427 stainless steel bar is placed in continuously flowing cooling water for immersion quenching. The temperature of the cooling water does not exceed 38° C., and the outlet water temperature of the UNS S41427 stainless steel bar is ≤100° C.

[0016] Furthermore, after the initial refining in the electric furnace and before mold casting, the ladle is protected by argon instead of nitrogen throughout the entire process;

[0017] And / or, the temperature of the annealing before finishing is 610-640° C., and the holding time is (4h / 100mm*D)-(4h / 100mm*D+5h), wherein h represents hours, and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, in mm;

[0018] And / or, the austenitizing temperature is 900-980° C., and the austenitizing holding time is: (2h / 100mm*D)-(2h / 100mm*D+5h), wherein h represents hours, and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, in mm.

[0019] Furthermore, during the water-cooling quenching, the water inlet temperature of the UNS S41427 stainless steel bar is ≥850°C;

[0020] And / or, the cooling water is circulated and used as circulating water during water-cooling quenching.

[0021] Furthermore, the UNS S41427 stainless steel bar is filled with water within 2 minutes after being taken out of the austenitizing furnace; furthermore, the UNS S41427 stainless steel bar is filled with water within 1 minute after being taken out of the austenitizing furnace.

[0022] Furthermore, 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.

[0023] Furthermore, the flow rate of the cooling water is 250-1000m 3 / h.

[0024] Furthermore, the holding temperature of the primary tempering is 560-620° C., and the holding time is (4 h / 100 mm*D)-(4 h / 100 mm*D+5 h), wherein h represents hours, and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, in mm; and / or, air cooling is performed after the holding in the primary tempering to release quenching stress.

[0025] Furthermore, the holding temperature of the secondary tempering is 540-600°C, preferably 30-50°C lower than the holding temperature of the primary tempering, and the holding time is (4h / 100mm*D)-(4h / 100mm*D+5h), wherein h represents hours and D represents the diameter of the UNSS41427 stainless steel bar in the black skin state, in 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.

[0026] In a second aspect, a UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas use is prepared using the preparation method described in the first aspect;

[0027] The UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas includes the following chemical components by mass fraction: C≤0.03%, Si≤0.50%, Mn≤1.0%, P≤0.02%, S≤0.005%, Ni 4.5-6.0%, Cr 11.5-13.5%, Mo 1.5-2.5%, Ti≤0.01%, V 0.01-0.50%, N≤0.03%, and the remainder is Fe and unavoidable impurities.

[0028] In a third aspect, a completion tool is made of the UNSS41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas prepared by the preparation method of the first aspect or the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas prepared by the preparation method of the second aspect.

[0029] The present invention has at least the following beneficial effects:

[0030] The present invention provides a method for preparing a UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas. The prepared UNS S41427 110KSI grade quenched and tempered bar can pass the SSC test, can replace the UNS S41427 95KSI bar, and has strong versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the grain map (100x 5-grade grain size) of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Example 1 of the present invention;

[0032] Figure 2 This is the grain map (500x 5-grade grain size) of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Example 1 of the present invention;

[0033] Figure 3 This is the grain map (100x 5-grade grain size) of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Example 2 of the present invention;

[0034] Figure 4 The grain map (500x 5-grade grain size) of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Example 2 of the present invention;

[0035] Figure 5 This is a macroscopic surface image of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Example 1 of the present invention;

[0036] Figure 6 This is a 10X viewing field surface image of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Example 1 of the present invention;

[0037] Figure 7 This is a macroscopic surface image of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Example 2 of the present invention;

[0038] Figure 8 This is a 10X viewing field surface image of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Example 2 of the present invention;

[0039] Figure 9 This is a macroscopic surface image of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Comparative Example 1 of the present invention;

[0040] Figure 10 This is a 10X viewing field surface image of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0041] 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.

[0042] 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.

[0043] The main composition range of UNS S41427 steel for oil and gas use (wt%) is: C≤0.03%, Si≤0.50%, Mn≤1.0%, P≤0.02%, S≤0.005%, Ni 4.5-6.0%, Cr 11.5-13.5%, Mo1.5-2.5%, Ti≤0.01%, V 0.01-0.50% (NACE MR0175 Table D.6).

[0044] The current production process for UNS S41427 quenched and tempered stainless steel for oil and gas applications includes: raw material preparation (molten iron, scrap steel, alloys, etc., control of the five harmful elements), electric furnace smelting + VOD + LF + VD (inclusion control, gas content control), die casting (microstructure uniformity control), annealing / hot-rolling, heating, forging / rolling (material grain size and density control), annealing, straightening (flatness preparation before quenching and tempering), quenching and tempering [air or oil quenching → primary tempering → (straightening) → stress relief tempering], physical and chemical testing, surface finishing, flaw detection, surface inspection, inspection and assessment, and packaging and warehousing. Through this production process, 95KSI grade steel and 110KSI grade steel of UNS S41427 can be obtained. Among them, 95KSI grade steel can pass the SSC evaluation, but 110KSI grade steel cannot. The reason is that the tensile strength of 110KSI is higher than that of 95KSI. Normally, 110KSI grade steel can only be used in CO2 environments and cannot be used in H2S-containing environments. After extensive research, the inventors found that only by making the tensile strength and hardness of the material close to the tensile strength and hardness of 95KSI, and the yield strength meeting 110KSI at the same time, it is necessary to adjust the yield strength ratio of the material to ensure that the strength and hardness of the material are not too high, so that the material can reach the 110KSI grade and pass the SSC test (applicable to H2S-containing environments). Specifically, the yield strength ratio of the material can be adjusted by controlling the content of the solid solution strengthening element N and water-cooled quenching (water quenching) treatment. Therefore, the following technical solution was finally adopted:

[0045] In a first aspect, a method for preparing UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas use comprises:

[0046] S1. According to the chemical composition of UNS S41427 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-sending, heating, rolling or forging, annealing and finishing in sequence to obtain UNS S41427 stainless steel bars;

[0047] wherein, after vacuum degassing, the nitrogen content is controlled to be ≤0.03wt%;

[0048] S2, sequentially subjecting the UNS S41427 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, straightening, and secondary tempering to obtain a UNS S41427 stainless steel 110KSI grade quenched and tempered bar;

[0049] During the water-cooling quenching, the austenitized UNS S41427 stainless steel bar is placed in continuously flowing cooling water for immersion quenching. The temperature of the cooling water does not exceed 38° C., and the outlet water temperature of the UNS S41427 stainless steel bar is ≤100° C.

[0050] The present invention discloses a method for preparing a UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas use. The method controls the content of the solid solution strengthening element nitrogen during steelmaking, performs finishing on the bar before quenching and tempering, and uses water as a medium for immersion quenching during quenching and tempering. While ensuring that the material does not crack, the steel is kept in water as much as possible, thereby improving the yield strength ratio of the material. The method not only enables the UNS S41427 stainless steel quenched and tempered bar to reach 110KSI grade strength, thus becoming a UNS S41427 stainless steel 110KSI grade quenched and tempered bar, but also has relatively low hardness, high toughness, and H2S corrosion resistance, meeting the requirements of NACE MR0175, and replacing UNS S4142795KSI, thereby facilitating user material selection and increasing the versatility of the material.

[0051] If the nitrogen content is not controlled in the preparation method of the present invention, the qualified rate of the bar will be unstable and may not meet the requirements of NACE MR0175. This is because the Cr content in the steel is too high, and Cr has the effect of fixing nitrogen. Nitrogen is a solid solution strengthening element, which will lead to high strength and hardness of the material, affecting the SSC corrosion results. Therefore, the nitrogen content is controlled to be ≤0.03wt%, and further not to exceed 0.02wt%. Typical but non-limiting examples include 0.03wt%, 0.027wt%, 0.025wt%, 0.023wt%, 0.02wt%, 0.017wt%, 0.015wt%, 0.013wt%, 0.01wt%, 0.007wt%, 0.005wt%, 0.001wt%, 0.0005wt%, 0.0001wt%, etc. If water is not used as the medium for immersion quenching, and air cooling quenching is used, the material properties will be uneven and fluctuate greatly, making it difficult to obtain the desired results. If spray quenching is used, the steel rod must be rotated to ensure uniform contact with water, and the contact between air and the steel rod may affect cooling. Moreover, it can only process single or small quantities of steel rods, while immersion quenching can process large quantities of steel rods. Therefore, the present invention adopts immersion quenching with water as the medium, controls the cooling water to be continuously flowing water and maintains the water temperature no more than 38°C. Finally, by controlling the water outlet temperature of the rod and pre-finishing to avoid the source of induced cracks, it is ensured that the material obtained by water quenching does not suffer from stress cracking or grain boundary cracking of the structure, reaches a strength grade of 110KSI, passes the SSC evaluation, and meets the application of NACE MR0175.

[0052] Specifically, under normal circumstances, the bar temperature is high, and the cooling water in contact with the bar will inevitably boil, forming a steam film on the bar surface. However, when the cooling water continues to flow, it can quickly exchange heat with the bar and / or boiling water, quickly transfer heat, and reduce the water temperature after heat exchange. After extensive research, the inventors found that when the water temperature in the quenching tank is controlled to not exceed 38°C, that is, when the water temperature in the quenching tank is controlled by controlling the flow rate of the cooling water according to the size of the quenching tank and the size of the bar, it is possible to avoid water boiling, control the cooling rate of the bar, and stabilize and uniformly cool the bar from the outside to the inside, ensuring stable material transformation, without residual austenite, stress cracking, or grain boundary cracking. Therefore, the temperature of the cooling water can be selected, typically but not limited to, 37°C, 35°C, 30°C, 25°C, 20°C, 15°C, 10°C, 5°C, etc. In addition, the outlet water temperature of the UNS S41427 stainless steel bar can typically but not limitedly be selected as 100°C, 90°C, 80°C, 70°C, 60°C, 50°C, 40°C, 30°C, 20°C, etc. By controlling the outlet water temperature of the bar, the material is ensured to be fully quenched while meeting the performance requirements and preventing the material from cracking.

[0053] In the present invention, the cooling water can be ordinary 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-cooled quenching, without the need for specialized cooling or heating treatment. As long as the water is continuously flowing throughout the quenching process and the water temperature is maintained below 38°C after contact and heat exchange with the bar, stable material transformation and the absence of retained austenite are ensured.

[0054] In the present invention, the outlet water temperature is the outlet water temperature of the steel rod, which reflects the surface temperature of the steel rod. The temperature of the core of the steel rod is higher than the surface temperature because it is only affected by heat conduction.

[0055] As an optional embodiment of the preparation 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.

[0056] 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.

[0057] As an optional implementation of the preparation method of the present invention, after the initial refining in the electric furnace and before mold casting, the ladle is protected by argon rather than nitrogen throughout the entire process, thereby ensuring the nitrogen content in the steel.

[0058] As an optional embodiment of the preparation method of the present invention, the temperature of the annealing before finishing is 610-640°C (such as 615°C, 620°C, 625°C, 630°C, 635°C, etc.), and the holding time is (4h / 100mm*D) to (4h / 100mm*D+5h), where h represents hours and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, mm.

[0059] In the above technical solution, annealing temperatures exceeding the range, especially exceeding 650°C, are prone to phase transition, while temperatures below the range, especially below 600°C, are ineffective. The annealing time should also be neither too long nor too short. If the time is too short, stress relief will not be achieved, while if the time is too long, production capacity will be wasted.

[0060] As an optional embodiment of the preparation 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 UNS S41427 stainless steel bar in the black skin state, mm.

[0061] In the present invention, UNS S41427 stainless steel bars are austenitized at a temperature of 900-980°C and held for a predetermined time before water-quenching. The austenitized bars can be directly water-quenched, i.e., placed in water at a furnace temperature of 900-980°C for water cooling. However, in actual operation, the bars need to undergo a certain period of time and space transfer after being removed from the furnace, so the surface of the bars is affected by the environment and the temperature drops. Furthermore, the surface of the bars actually has an oxide scale. Therefore, the water inlet temperature of the bars can be controlled based on the oxide scale temperature or the time from the time of removal from the furnace to the time of complete water inlet. The latter is preferred and is more convenient for on-site operation in actual production. Optionally, the water inlet temperature of the UNS S41427 stainless steel bar is ≥850°C; further, the water inlet of the UNS S41427 stainless steel bar is completed within 2 minutes after the austenitizing furnace; further, the water inlet of the UNS S41427 stainless steel bar is completed within 1 minute after the austenitizing furnace to ensure stable material properties. Therefore, in the present invention, the water inlet temperature of the UNS S41427 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 water inlet of the UNS S41427 stainless steel bar is completed within 110s, 100s, 90s, 80s, 70s, 60s, 50s, 40s, 30s, 25s, 20s, 15s, 10s, 0s, etc. after the austenitizing furnace.

[0062] As an optional embodiment of the preparation method of the present invention, the 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.).

[0063] In the above technical solution, by controlling the cooling water flow rate ≥ 250m 3 / h, which can not only ensure that the cooling water temperature does not exceed 38℃ and avoid water boiling, but also ensure that the cooling process of the rod is uniform from the inside to the outside, and realize the precise control of the cooling rate of the rod during the water cooling process, thus 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 upper limit of the existing equipment can be selected to avoid the water pressure from acting on the rod. For example, the water flow rate of the cooling water can be 250-1000m 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 and the cooling water does not exceed 38°C.

[0064] As an optional embodiment of the preparation method of the present invention, the holding temperature of the primary tempering is 560-620°C (such as 570°C, 580°C, 590°C, 610°C, etc.), and the holding time is (4h / 100mm*D) to (4h / 100mm*D+5h), where h represents hours and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, in mm; and / or, air cooling is performed after the holding in the primary tempering to release quenching stress.

[0065] In the above technical solution, the primary tempering temperature is controlled at 560-620°C to avoid the situation where the higher the temperature, the lower the tensile strength and yield strength of the steel.

[0066] As an optional embodiment of the preparation method of the present invention, the holding temperature of the secondary tempering is 540-600°C (such as 550°C, 560°C, 570°C, 580°C, 590°C, etc.), preferably 30-50°C lower than the holding temperature of the primary tempering (such as 35°C, 40°C, 45°C, etc.), and the holding time is (4h / 100mm*D) to (4h / 100mm*D+5h), where h represents hours and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, in 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.

[0067] In the above technical solution, the secondary tempering temperature is preferably 30 to 50° C. lower than the primary tempering holding temperature, which can avoid some possible abnormal situations.

[0068] As an optional embodiment of the preparation method of the present invention, the specification of the UNS S41427 stainless steel bar is round steel with a diameter of Φ12-310 mm (such as 15 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, etc.).

[0069] In a second aspect, a UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas use is prepared using the preparation method described in the first aspect;

[0070] The UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas comprises the following chemical components by mass fraction: C≤0.03%, Si≤0.50%, Mn≤1.0%, P≤0.02%, S≤0.005%, Ni 4.5-6.0%, Cr 11.5-13.5%, Mo 1.5-2.5%, Ti≤0.01%, V0.01-0.50%, N≤0.03%, and the remainder is Fe and unavoidable impurities; further, the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas comprises the following chemical components by mass fraction: C≤0.03%, Si≤0.25%, Mn≤0.5%, P≤0.02%, S≤0.005%, Ni 5.0-6.0%, Cr11.5-13.5%, Mo 1.5-2.2%, Ti<0.005%, V 0.01-0.20%, N≤0.02%, the rest are Fe and inevitable impurities.

[0071] In a third aspect, a completion tool is made of the UNSS41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas prepared by the preparation method of the first aspect or the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas prepared by the preparation method of the second aspect.

[0072] The specific embodiments of the present invention will be further explained below in conjunction with Examples and Comparative Examples:

[0073] Example 1

[0074] This embodiment provides a UNS S41427 steel suitable for the oil and gas field, with a production specification of 110KSI steel grade and Φ130mm round steel. The main chemical components of the steel and their contents (wt%) are: C: 0.02%, Si: 0.24%, Mn: 0.38%, P: 0.015%, S: 0.002%, Cr: 12.15%, Ni: 5.39%, Mo: 1.95%, V: 0.12%, Ti: <0.005%, N: 0.012%, and the rest is Fe and unavoidable impurities.

[0075] Specifically, the method for manufacturing UNS S41427 steel produced in this embodiment includes the following steps:

[0076] S1. Billet Preparation: The raw materials are sequentially subjected to electric furnace smelting, LF refining and VD vacuum degassing (N content is analyzed after vacuum degassing to ensure that the N content is ≤ 0.03%, and argon protection is used in the ladle rather than nitrogen protection throughout the process), die casting, hot feeding, heating, and rolling to produce UNS S41427 rolled round steel; wherein the final rolling temperature is 927°C;

[0077] 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.

[0078] 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;

[0079] 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;

[0080] 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℃. Outlet steel surface temperature is 76℃;

[0081] S6. Primary tempering: The tempering holding temperature is set to 590°C for 7 hours. After holding, the furnace is taken out of the furnace and air-cooled to complete the primary tempering.

[0082] S7, straightening;

[0083] S8. Secondary tempering: The tempering holding temperature is set at 550°C for 7 hours. After holding, the steel is taken out of the furnace and air-cooled to complete the tempering. UNS S41427110KSI steel is obtained.

[0084] Example 2

[0085] This embodiment provides a UNS S41427 steel suitable for the oil and gas field, with a production specification of 110KSI steel grade and Φ250mm round steel. The main chemical components of the steel and their contents (wt%) are: C: 0.01%, Si: 0.23%, Mn: 0.41%, P: 0.014%, S: 0.001%, Cr: 12.21%, Ni: 5.55%, Mo: 2.17%, V: 0.13%, Ti: <0.005%, N: 0.011%, and the rest is Fe and unavoidable impurities.

[0086] Specifically, the method for manufacturing UNS S41427 steel produced in this embodiment includes the following steps:

[0087] S1. Preparation of steel billets: The raw materials are sequentially subjected to electric furnace smelting, LF refining outside the furnace + VD vacuum degassing (N content is analyzed after vacuum degassing and the N content should be ensured to be ≤0.03%. Argon protection is used in the ladle instead of nitrogen protection throughout the process), die casting, hot feeding, heating, and forging to produce UNS S41427 forged round steel; wherein, the final forging temperature is 907°C;

[0088] 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.

[0089] 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;

[0090] S4, the material is austenitized, the austenite temperature is set to 970 ° C, kept at this temperature for 6 hours, and then taken out of the furnace for quenching;

[0091] 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℃;

[0092] S6. Primary tempering: The tempering holding temperature is set to 590°C for 13 hours. After holding, the furnace is taken out of the furnace and air-cooled to complete the primary tempering.

[0093] S7, straightening;

[0094] S8. Secondary tempering: The tempering holding temperature is set at 550°C for 13 hours. After holding, the steel is taken out of the furnace and air-cooled to complete the tempering. UNS S41427110KSI steel is obtained.

[0095] Comparative Example 1

[0096] This comparative example provides a UNS S41427 steel suitable for the oil and gas field, with a production specification of 110KSI steel grade and Φ250mm round steel. The main chemical components of the steel and their contents (wt%) are: 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%, and the rest are Fe and unavoidable impurities.

[0097] Specifically, the method for manufacturing the UNS S41427 steel produced in this comparative example comprises the following steps:

[0098] S1. Preparation of steel billets: The raw materials are sequentially subjected to electric furnace smelting, LF refining outside the furnace + VD vacuum degassing (without special control for nitrogen), die casting, hot-melting, heating, and forging to produce UNS S41427 forged round steel; wherein the final forging temperature is 907°C;

[0099] 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.

[0100] 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;

[0101] S4, the material is austenitized, the austenite temperature is set to 970 ° C, kept at this temperature for 6 hours, and then taken out of the furnace for quenching;

[0102] S5. Water-cooled quenching: Circulating water is not used. Ensure that the cooling water is filtered and cleaned to remove impurities such as oil, scale, and suspended solids before use. The time from bar exiting the furnace to water entry is 59 seconds; the water temperature before entering the water is 25°C; the water temperature after exiting the water is 51°C; and the steel surface temperature at the exit is 165°C.

[0103] S6. Primary tempering: The tempering holding temperature is set to 590°C for 13 hours. After holding, the furnace is taken out of the furnace and air-cooled to complete the primary tempering.

[0104] S7, straightening;

[0105] S8. Secondary tempering: The tempering holding temperature is set at 550°C for 13 hours. After holding, the steel is taken out of the furnace and air-cooled to complete the tempering. UNS S41427110KSI steel is obtained.

[0106] Performance Testing

[0107] 1. With reference to API 6A standard, mechanical properties of samples taken at 1 / 2R of UNS S41427110KSI steel obtained in Example 1, Example 2 and Comparative Example 1 were tested. The results are shown in the following table:

[0108]

[0109]

[0110] From the table above we can see that:

[0111] The mechanical properties of Examples 1, 2, and Comparative Example 1 all meet the requirements for standard UNS S414271 10KSI. However, the tensile strength and hardness of Examples 1 and 2 are lower than those of Comparative Example 1. If the tensile strength and hardness of Comparative Example 1 were further reduced, the yield strength would be substandard and would not meet the basic material requirements.

[0112] In addition, the grain size of the UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas obtained in Example 1 is as follows: Figure 1 、 Figure 2As shown in the figure, it can be seen that the grain size is level 5, the grains are uniform, and no defects are seen. The grain size of the UNSS41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas 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 level 5, the grains are uniform, and no defects are seen.

[0113] 2. According to the NACE0175 requirements for 95KSI, the UNSS41427110KSI steel obtained in Examples 1 and 2 and Comparative Example 1 was subjected to SSC testing (test temperature 22°C to 24°C, H2S partial pressure 0.01 bar, total pressure 1 bar, CO2 balance gas, Cl - : 140000 mg / L, Buffer for pH balance: 0.82 g / L CH3COONa+CH3COOH, pH 4.50, loading according to 90% of the actual yield strength).

[0114] The test results show that after 720h, the sample of Example 1 did not break, and the macroscopic surface (such as Figure 5 As shown) and the sample 10X field of view surface (as shown Figure 6 No cracks were generated and the samples were qualified; the sample of Example 2 did not break after 720h, and the macroscopic surface (as shown Figure 7 As shown) and the sample 10X field of view surface (as shown Figure 8 No cracks were generated and the samples were qualified; the sample of comparative example 1 did not break after 720h, and the macroscopic surface (as shown) Figure 9 As shown) and the sample 10X field of view surface (as shown Figure 10 As shown in Figure 2, no cracks were generated, but severe pitting corrosion occurred, and the sample failed. It can be seen that the UNS S41427 produced according to the method of the present invention passed the SSC test, met the NACE requirements, and the performance and structure met the requirements for use.

[0115] 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 preparing UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas, characterized in that: include: S1. According to the chemical composition of UNS S41427 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-sending, heating, rolling or forging, annealing and finishing in sequence to obtain UNS S41427 stainless steel bars; wherein, after vacuum degassing, the nitrogen content is controlled to be ≤0.03wt%; S2, sequentially subjecting the UNS S41427 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, straightening, and secondary tempering to obtain a UNS S41427 stainless steel 110KSI grade quenched and tempered bar; During the water-cooling quenching, the austenitized UNS S41427 stainless steel bar is placed in continuously flowing cooling water for immersion quenching. The temperature of the cooling water does not exceed 38° C., and the outlet water temperature of the UNS S41427 stainless steel bar is ≤100° C.

2. The preparation method according to claim 1, characterized in that After the initial refining in the electric furnace and before mold casting, the ladle is protected by argon instead of nitrogen throughout the process; And / or, the temperature of the annealing before finishing is 610-640° C., and the holding time is (4h / 100mm*D)-(4h / 100mm*D+5h), wherein h represents hours, and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, in mm; And / or, the austenitizing temperature is 900-980° C., and the austenitizing holding time is: (2h / 100mm*D)-(2h / 100mm*D+5h), wherein h represents hours, and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, in mm.

3. The preparation method according to claim 1, characterized in that: During the water-cooling quenching, the water inlet temperature of the UNS S41427 stainless steel bar is ≥850°C; And / or, the cooling water is circulated and used as circulating water during water-cooling quenching.

4. The preparation method according to claim 3, characterized in that The UNS S41427 stainless steel bar is filled with water within 2 minutes after being taken out of the austenitizing furnace; and / or the circulating water is used for water cooling quenching after removing impurities.

5. The preparation method according to claim 4, characterized in that: The UNS S41427 stainless steel bar is filled with water within 1 minute after being taken out of the austenitizing furnace; and / or, the impurity removal includes removing impurities such as oil, oxide scale, and suspended solids.

6. The preparation method according to claim 1, characterized in that: The cooling water flow rate is 250~1000m 3 / h.

7. The preparation method according to claim 1, characterized in that: The holding temperature of the primary tempering is 560-620° C., and the holding time is (4 h / 100 mm*D)-(4 h / 100 mm*D+5 h), where h represents hours and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, in mm; and / or, air cooling is performed after the holding in the primary tempering to release quenching stress.

8. The preparation method according to claim 1, characterized in that: The holding temperature of the secondary tempering is 540-600° C., which is 30-50° C. lower than the holding temperature of the primary tempering, and the holding time is (4 h / 100 mm*D)-(4 h / 100 mm*D+5 h), where h represents hours and D represents the diameter of the UNS S41427 stainless steel bar in the black skin state, in 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.

9. A UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas, characterized by: Prepared by the preparation method according to any one of claims 1 to 8; The UNS S41427 stainless steel 110KSI grade quenched and tempered bar for oil and gas includes the following chemical components by mass fraction: C≤0.03%, Si≤0.50%, Mn≤1.0%, P≤0.02%, S≤0.005%, Ni 4.5-6.0%, Cr 11.5-13.5%, Mo 1.5-2.5%, Ti≤0.01%, V 0.01-0.50%, N≤0.03%, and the remainder is Fe and unavoidable impurities.

10. A completion tool, characterized in that: The oil and gas UNS S41427 stainless steel 110KSI grade quenched and tempered bar is prepared by the preparation method according to any one of claims 1 to 8, or the oil and gas UNS S41427 stainless steel 110KSI grade quenched and tempered bar according to claim 9.

Images