Wear-resistant steel for oil exploitation and preparation method thereof

Abstract

The invention provides wear-resistant steel for oil exploitation and a preparation method thereof, and relates to the technical field of wear-resistant steel. The wear-resistant steel for oil exploitation is obtained through molten iron pretreatment, refining, continuous casting, slow cooling, casting blank heating, rolling, graded cooling, quenching and tempering. The wear-resistant steel for oil exploitation comprises the following chemical components in percentage by mass: 0.24%-0.38% of C, 0.10%-0.50% of Si, 0.35%-0.50% of Mn, 0.02%-0.05% of Ti, 0.001%-0.003% of B, 0.75% < = Cr + Mo + Ni < = 3%, 0.05% < = Nb + V < = 0.05% and the balance of Fe and inevitable impurities. The ratio of Nb to V is 1: (1-2.5). By optimizing chemical components and accurately controlling the proportion of alloy elements and combining with a specific preparation process, the comprehensive wear resistance of the steel is greatly improved, the stability and durability of the wear-resistant steel are improved, the service life of the wear-resistant steel is prolonged, the maintenance cost is reduced, the production efficiency is improved, and the production cost is reduced. The wear-resistant steel disclosed by the invention has a good application prospect in the field of oil exploitation.

Description

Technical Field

[0001] The invention relates to the technical field of wear-resistant steel, in particular to wear-resistant steel for petroleum mining and a preparation method thereof. Background Art

[0002] Wear-resistant steel plate is a kind of steel specially designed to resist wear and impact. It is usually used in mechanical products such as mining, construction, cement production, ports, electricity and metallurgy under harsh working conditions, in order to reduce the wear rate of mechanical parts and prolong the time of failure due to wear.

[0003] Generally, wear-resistant steel has a relatively low carbon content, so compared with wear-resistant cast iron, wear-resistant steel has better toughness, plasticity and welding performance. In addition, the production and processing technology of wear-resistant steel is more flexible. Through appropriate process treatment, austenite, martensite, bainite or composite structure can be obtained to improve its wear resistance and comprehensive application performance. There are many types of wear-resistant steel, which can be classified according to composition, structure or mechanical properties. According to the chemical composition, wear-resistant steel is divided into medium manganese steel, high manganese steel, ultra-high manganese steel, modified manganese steel, medium carbon, medium-high carbon, high carbon steel, as well as low alloy, medium alloy, and high alloy wear-resistant steel; according to mechanical properties, wear-resistant steel can be divided into wear-resistant steels of different hardness levels and quality grades; according to metallographic structure, wear-resistant steel is divided into austenite, bainite, martensite and composite structure wear-resistant steel. Among them, austenitic wear-resistant steel mainly refers to wear-resistant cast steel with a manganese content of 6%-25%. Manganese element is used to stabilize the austenite structure, and it has excellent work hardening and wear resistance. Bainitic wear-resistant steel has excellent comprehensive mechanical properties, and high-quality bainitic wear-resistant steel can be obtained through reasonable composition and cooling system control. Martensitic wear-resistant steel has high hardness and good strength and toughness matching, and its matrix hardness and toughness are improved through alloying and process means. Dual-phase wear-resistant steel combines the performance characteristics of each organization, has good strength, toughness and wear resistance, and expands the scope of application. Although there are many types of wear-resistant steel, they all have deficiencies to varying degrees. In practical applications, special wear-resistant steels should be selected or developed according to working conditions. In short, researching and developing high-performance wear-resistant steels and understanding their organizational characteristics and performance characteristics are the basis for improving the performance of wear-resistant steels.

[0004] The oil extraction environment usually contains corrosive substances, which will aggravate the corrosion and wear of steel. Therefore, compared with wear-resistant steel used in general wear environments, wear-resistant steel used in oil extraction has certain requirements for wear resistance in corrosive environments. In addition, equipment and components in oil extraction must not only be wear-resistant, but also have sufficient toughness to cope with the impact and stress during drilling. Therefore, wear-resistant steel used in oil extraction needs to seek a balance between high toughness and high hardness during the research and development process, so that it is not easy to break or peel off while being wear-resistant. Ordinary wear-resistant steel mainly focuses on surface hardness and has lower toughness requirements. Finally, the design of wear-resistant steel used in oil extraction also needs to consider fatigue resistance under long-term exposure to harsh environments. Repeated stress in a corrosive environment can cause metal fatigue and aggravate wear, so improving the wear resistance of steel in a corrosive environment can also help to increase the fatigue life of steel. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a wear-resistant steel for oil production and a preparation method thereof. By adjusting the element content and preparation process of the wear-resistant steel, the present invention not only improves the strength, toughness and comprehensive wear resistance of the wear-resistant steel, but also reduces cracks and deformation that may occur during the production process, so that the material has good application prospects in the field of oil production.

[0006] The present invention provides a wear-resistant steel for oil mining, which is obtained by molten iron pretreatment, refining, continuous casting, slow cooling, billet heating, rolling, graded cooling, quenching, and tempering. The chemical composition and mass percentage of the wear-resistant steel for oil mining are as follows:

[0007] C 0.24%~0.38%, Si 0.10%~0.50%, Mn 0.35%~0.50%, Ti 0.02%~0.05%, B 0.001%~0.003%, 0.75%≤Cr+Mo+Ni≤3%, Nb+V≤0.05%, the balance is Fe and unavoidable impurities;

[0008] Nb:V=1:(1~2.5).

[0009] Preferably, the chemical composition of the wear-resistant steel used in petroleum mining is Mo 0.25% to 0.35%, and Nb 0.01% to 0.02.

[0010] Preferably, the chemical composition of the wear-resistant steel used for petroleum mining is Nb:V=1:2.

[0011] The present invention also provides a method for preparing wear-resistant steel for petroleum mining, comprising the following steps:

[0012] The raw materials are melted into molten iron and then pretreated. After the molten iron is refined, large slabs are continuously cast, and then the ingots are stacked and slowly cooled. After the slow cooling is completed, the ingots are heated and then rolled. After cooling, they are graded quenched and tempered to obtain wear-resistant steel for oil mining.

[0013] Preferably, the desulfurization pretreatment is desulfurization pretreatment.

[0014] Preferably, the refining is LF refining and / or RH refining.

[0015] Preferably, the rolling is rough rolling and finish rolling. More preferably, the rough rolling is rough rolling in the austenite recrystallization region, and the finish rolling is finish rolling in the austenite non-recrystallization region.

[0016] Preferably, the quenching is step quenching, firstly, the steel plate is heated to 880°C, kept at this temperature for 15 to 60 minutes, then precooled, and finally cooled to the target temperature, and the quenching is completed after cooling to room temperature. More preferably, the temperature of the steel plate after precooling is 200°C to 300°C, the precooling rate is 20°C / s to 40°C / s, and the final cooling rate is 5°C / s to 10°C / s.

[0017] Preferably, the tempering temperature is 180° C. and the holding time is 60 to 120 minutes.

[0018] Compared with the prior art, the present invention optimizes the chemical composition and precisely controls the proportion of alloying elements, thereby significantly improving the comprehensive wear resistance of steel while reducing the amount of alloying elements and ensuring toughness, making it suitable for the field of oil production in a high-wear environment. The present invention adopts a staged cooling process that combines graded quenching, pre-cooling and final cooling, combined with a tempering process and the adjustment of elements, to further refine the grains and improve the dimensional stability and performance uniformity of the product, improve the stability and durability of the wear-resistant steel, and thereby increase the service life of the wear-resistant steel and reduce maintenance costs. Finally, the present invention improves production efficiency and reduces production costs by optimizing the production process, so that the wear-resistant steel of the present invention has good application prospects in the field of oil production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the accompanying drawings.

[0020] Figure 1 The present invention is a flow chart of the preparation process of wear-resistant steel for petroleum mining. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The present invention provides a wear-resistant steel for oil mining, which is obtained by molten iron pretreatment, refining, continuous casting, slow cooling, billet heating, rolling, graded cooling, quenching, and tempering. The chemical composition and mass percentage of the wear-resistant steel for oil mining are as follows:

[0023] C 0.24~0.38,Si 0.10~0.50%,Mn 0.35~0.50%,Ti 0.02~0.05%,B 0.001~0.003,0.75≤Cr+Mo+Ni≤3,Nb+V≤0.05,balance is Fe and unavoidable impurities;

[0024] Nb:V=1:(1~2.5).

[0025] In some specific embodiments of the present invention, the chemical composition of the wear-resistant steel used for petroleum mining is 0.25% to 0.35% Mo and 0.01% to 0.02 Nb.

[0026] Generally speaking, the tensile strength of low carbon steel and medium carbon steel and the C content satisfy the following relationship:

[0027] Rm=2940×C%+820

[0028] Therefore, when designing the elements of the wear-resistant steel, the present invention limits the C content to a range of 0.24 to 0.38 based on the design requirements while taking into account the superposition of the strengthening effects of other alloy elements to ensure the strength and hardness requirements.

[0029] Mn, Mo, Nb and V have the effect of refining grains, Si and Mo can improve tempering stability, and Mo can be used to refine the precipitate phase and improve the thermal stability of the precipitate phase. From the carbon equivalent formula for weldability evaluation, it can be seen that the content of C, Si, Mn, Ni, Cr, Mo and V also affects the welding performance of steel, so the addition amount of these alloy elements should be controlled to ensure the welding performance of steel. The addition of B can improve hardenability and avoid the problem of insufficient hardenability and strengthening caused by the reduction of the addition amount of silver alloy elements.

[0030] In some specific embodiments of the present invention, the chemical composition of the wear-resistant steel used in petroleum mining is Nb:V=1:2. The present invention reduces the amount of Nb by adding V and controlling the ratio of Nb and V, reduces the production cost of steel, and controls the organizational structure of steel by optimizing the ratio of Nb and V, thereby improving the comprehensive performance of wear-resistant steel, especially wear resistance and toughness. Specifically, Nb and V can form a fine and uniformly distributed carbide precipitation phase. These dispersed carbides can effectively refine the grains and improve the wear resistance of steel. By regulating the amount and ratio of Nb and V, the size and type of carbide particles can be controlled to prevent the decrease in toughness caused by excessive carbide particles. In addition, in general, the price of Nb is higher than that of V. In the research process of the present invention, it was found that increasing the amount of Nb without using V can also achieve similar technical effects, but it will undoubtedly increase the production cost of steel. Therefore, the sharing of Nb and V is a more economical method to improve the wear resistance of steel. On the contrary, V cannot completely replace Nb, and if the Nb content is too low, the performance of the wear-resistant steel will be significantly reduced. In summary, Nb:V=1:(1-2.5) is a better range.

[0031] The present invention also provides a method for preparing wear-resistant steel for petroleum mining, comprising the following steps:

[0032] The raw materials are melted into molten iron and then pretreated. After the molten iron is refined, large slabs are continuously cast, and then the ingots are stacked and slowly cooled. After the slow cooling is completed, the ingots are heated and then rolled. After cooling, they are graded quenched and tempered. After tempering, they are air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0033] In some specific embodiments of the present invention, the desulfurization pretreatment is a desulfurization pretreatment, and the desulfurization pretreatment can be a commonly used desulfurization method, specifically including a spraying method (using lime powder or magnesium powder), a stirring method, a KR method, and the like.

[0034] In some specific embodiments of the present invention, the refining is LF refining and / or RH refining. In some preferred embodiments of the present invention, the refining is LF refining and RH refining.

[0035] In the present invention, LF refining is mainly used for desulfurization, deoxidation, removal of inclusions and fine-tuning of composition, and the molten steel is heated at the same time to reduce temperature fluctuations so that it has good temperature stability in subsequent processes. However, LF refining has limited ability to remove gaseous impurities (such as hydrogen and nitrogen) and is not effective in controlling oxidation losses of micro-alloy elements. RH refining is mainly used for degassing, which can effectively remove gaseous impurities such as hydrogen, oxygen and nitrogen, and significantly improve the toughness and fatigue resistance of steel. At the same time, since RH refining is carried out under vacuum, the temperature drop of the molten steel is less. However, RH refining has limited effects on desulfurization and deoxidation, and inclusions cannot be effectively removed. The combination of LF and RH refining can simultaneously achieve desulfurization, deoxidation, degassing, removal of inclusions and composition homogenization, achieving high purity and composition stability that are difficult to achieve when used alone. Therefore, according to actual conditions, a suitable refining method can be flexibly selected to achieve a balance between economy and process effect.

[0036] In some preferred embodiments of the present invention, the stacking slow cooling time is ≥36h.

[0037] In some specific embodiments of the present invention, the rolling is rough rolling and finish rolling, the rough rolling is rough rolling in the austenite recrystallization zone, and the finish rolling is finish rolling in the austenite non-recrystallization zone. In some preferred embodiments of the present invention, the cast billet is kept at 1180°C to 1200°C for 3 to 5 minutes before rough rolling. In some other preferred embodiments of the present invention, the cast billet is cooled to the rough rolling temperature at a speed of 3°C / s to 5°C / s, and then cooled at a speed of 5s -1 The deformation rate is to complete the single-pass compression deformation with a single-pass reduction rate of 20%, and then cool to the finishing temperature at a speed of 3℃ / s~5℃ / s for 5s -1 The steel is subjected to a single-pass compression deformation with a single-pass reduction rate of 30% at a deformation rate, and is cooled to room temperature at a speed of 10°C / s to 30°C / s to complete the rolling. The rough rolling temperature is 1100°C to 1150°C, and the finishing rolling temperature is 820°C to 900°C.

[0038] In some specific embodiments of the present invention, the quenching is graded quenching, firstly, the steel plate is heated to 880°C, kept warm for 15 to 60 minutes, and then pre-cooled. After pre-cooling to the target temperature, final cooling is performed, and quenching is completed after cooling to room temperature. After pre-cooling, the temperature of the steel plate is 200°C to 300°C, the pre-cooling rate is 20°C / s to 40°C / s, and the final cooling rate is 5°C / s to 10°C / s.

[0039] In some specific embodiments of the present invention, the tempering temperature is 180° C. and the holding time is 60 to 120 minutes.

[0040] In some preferred embodiments of the present invention, the preparation method of wear-resistant steel for oil mining also includes straightening, flaw detection, shot blasting and other steps, and the above steps are performed after rolling cooling and before quenching. Among them, straightening refers to adjusting the shape of the rolled steel by mechanical force to eliminate bending and warping to ensure the flatness and straightness of the material; flaw detection is to use non-destructive testing technology to detect defects inside and on the surface of the material, such as cracks, pores, inclusions, etc., to ensure the quality and reliability of the material; shot blasting is to project small steel shots or sand shots onto the surface of the material through a high-speed rotating shot blaster to remove surface oxide scale and dirt, improve surface quality, and harden the surface.

[0041] Straightening, flaw detection and shot blasting are important processes to improve the quality and reliability of steel and other metal materials. Straightening ensures the shape accuracy of the steel; flaw detection ensures the internal quality and structural integrity; shot blasting improves durability and subsequent processing effects by cleaning and strengthening the surface. These processes work together to make the material meet the application requirements and improve overall performance. Indeed, steps such as straightening, flaw detection and shot blasting are not necessary. The specific application can be selected according to actual conditions and needs to achieve a balance between product performance and economy.

[0042] To further illustrate the present invention, the following examples are provided for detailed description. The raw materials used in the following examples of the present invention are all commercially available. Unless otherwise specified, all tests were repeated 3 times, and the results are expressed as average values.

[0043] Example 1 A wear-resistant steel for oil mining, the chemical composition and mass percentage are as follows:

[0044] C 0.35%, Si 0.35%, Mn 0.40%, Ti 0.03%, B 0.001%, Mo 0.3%, Cr 1.2%, Ni 1.0%, Nb 0.01%, V 0.02%, and the balance is Fe and inevitable impurities.

[0045] The preparation method of wear-resistant steel for oil mining comprises the following steps:

[0046] After the raw materials are melted into molten iron, the KR method is used for desulfurization, followed by LF refining and RH refining. After the molten iron is refined, large slabs are continuously cast, and then the billets are stacked and slowly cooled for 48 hours. After the slow cooling is completed, the billets are heated to 1180℃ and kept warm for 5 minutes, cooled to 1150℃ at a speed of 3℃ / s, and then cooled at a speed of 5s. -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s -1The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 180°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0047] Example 2 A wear-resistant steel for oil mining, the chemical composition and mass percentage are as follows:

[0048] C 0.30%, Si 0.40%, Mn 0.35%, Ti 0.05%, B 0.003%, Mo 0.35%, Cr 1.5%, Ni 1.15%, Nb 0.02%, V 0.03%, and the balance is Fe and inevitable impurities.

[0049] The preparation method of wear-resistant steel for oil mining comprises the following steps:

[0050] After the raw materials are melted into molten iron, the KR method is used for desulfurization, followed by LF refining and RH refining. After the molten iron is refined, large slabs are continuously cast, and then the billets are stacked and slowly cooled for 36 hours. After the slow cooling is completed, the billets are heated to 1200℃ and kept warm for 3 minutes, cooled to 1120℃ at a speed of 5℃ / s, and then cooled at a speed of 5s -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 900℃ at a rate of 3℃ / s and then cooled to 900℃ at a rate of 5s. -1 The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 3°C / s. The steel plate is then kept warm at 180°C for 100 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0051] Example 3 A wear-resistant steel for oil mining, the chemical composition and mass percentage are as follows:

[0052] C 0.35%, Si 0.20%, Mn 0.50%, Ti 0.02%, B 0.002%, Mo 0.25%, Cr 1.5%, Ni 1.25%, Nb 0.02%, V 0.02%, and the balance is Fe and inevitable impurities.

[0053] The preparation method of wear-resistant steel for oil mining comprises the following steps:

[0054] After the raw materials are melted into molten iron, the KR method is used for desulfurization, followed by LF refining and RH refining. After the molten iron is refined, large slabs are continuously cast, and then the billets are stacked and slowly cooled for 48 hours. After the slow cooling is completed, the billets are heated to 1180℃ and kept warm for 5 minutes, cooled to 1150℃ at a speed of 3℃ / s, and then cooled at a speed of 5s. -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s -1 The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 180°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0055] Comparative Example 1

[0056] Same as Example 1, except that the chemical composition and mass percentage of the steel are as follows:

[0057] C 0.35%, Si 0.35%, Mn 0.40%, Ti 0.03%, B 0.002%, Mo 0.3%, Cr 1.2%, Ni 1.0%, Nb 0.01%, V 0.03%, and the balance is Fe and inevitable impurities.

[0058] Comparative Example 2

[0059] Same as Example 1, except that the chemical composition and mass percentage of the steel are as follows:

[0060] C 0.35%, Si 0.35%, Mn 0.40%, Ti 0.03%, B 0.002%, Mo 0.4%, Cr 1.2%, Ni 1.0%, Nb 0.01%, V 0.02%, and the balance is Fe and inevitable impurities.

[0061] Comparative Example 3

[0062] Same as Example 1, except that:

[0063] ① The ingot stacking and slow cooling were not performed. The specific preparation method steps were as follows: the raw materials were smelted into molten iron, desulfurized by KR method, and then LF refining and RH refining were performed. After the molten iron was refined, large slabs were continuously cast. The ingots were then heated to 1180℃ and kept warm for 5min, cooled to 1150℃ at a rate of 3℃ / s, and then cooled at a rate of 5s. -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s -1The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 180°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0064] ② The slow cooling time of the ingot stack is 24h. The specific preparation method steps are as follows:

[0065] After the raw materials are melted into molten iron, the KR method is used for desulfurization, followed by LF refining and RH refining. After the molten iron is refined, large slabs are continuously cast, and then the billets are stacked and slowly cooled for 24 hours. After the slow cooling is completed, the billets are heated to 1180℃ and kept warm for 5 minutes, cooled to 1150℃ at a speed of 3℃ / s, and then cooled at a speed of 5s. -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s -1 The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 180°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0066] Comparative Example 4

[0067] The same as Example 1, except that the ingot was not kept at 1180°C before rough rolling. The specific preparation method steps are as follows: the raw material is smelted into molten iron, then desulfurized by KR method, and then LF refining and RH refining are performed. After the molten iron is refined, large slabs are continuously cast, and then the ingots are stacked and slowly cooled for 48 hours. After the slow cooling is completed, it is heated to 1150°C and then heated for 5 seconds. -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s -1 The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 180°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0068] Comparative Example 5

[0069] The same as Example 1, except that: cooling to 1150°C at a rate of 10°C / s, cooling to 860°C at a rate of 10°C / s, the specific preparation method steps are as follows: the raw material is smelted into molten iron, desulfurized by KR method, and then LF refining and RH refining are performed, large slabs are continuously cast after molten iron refining, and then the billet stacking is slowly cooled for 48 hours, after the slow cooling is completed, the billet is heated to 1180°C and then kept warm for 5 minutes, cooled to 1150°C at a rate of 10°C / s, and then heated for 5 seconds -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 10℃ / s and cooled to 5s -1 The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 180°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0070] Comparative Example 6

[0071] The same as Example 1, except that the cooling rate after finishing rolling is 5°C / s. The specific preparation method steps are as follows: the raw material is smelted into molten iron, and then desulfurized by KR method, and then LF refining and RH refining are performed. After the molten iron is refined, large slabs are continuously cast, and then the billet stacking is slowly cooled for 48 hours. After the slow cooling is completed, the billet is heated to 1180°C and kept warm for 5 minutes, cooled to 1150°C at a rate of 3°C / s, and then heated to 5s -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s -1 The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 180°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0072] Comparative Example 7

[0073] The same as Example 1, except that the quenching temperature is 920°C. The specific preparation method steps are as follows: the raw material is melted into molten iron, and then the KR method is used for desulfurization, and then LF refining and RH refining are performed. After the molten iron is refined, large slabs are continuously cast, and then the stacked billets are slowly cooled for 48 hours. After the slow cooling is completed, the billets are heated to 1180°C and then kept warm for 5 minutes, cooled to 1150°C at a rate of 3°C / s, and then cooled at a rate of 5s -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s-1 The steel plate is heated to 920°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 180°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0074] Comparative Example 8

[0075] The same as Example 1, except that: no staged cooling is performed after quenching, and the specific preparation method steps are as follows: the raw material is smelted into molten iron, and then desulfurization is performed by the KR method, and then LF refining and RH refining are performed, and after the molten iron is refined, large slabs are continuously cast, and then the billet stacking is slowly cooled for 48 hours, and after the slow cooling is completed, the billet is heated to 1180°C and then kept warm for 5 minutes, cooled to 1150°C at a rate of 3°C / s, and then cooled at a rate of 5s -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s -1 The steel plate is subjected to a single-pass compression deformation with a single-pass reduction rate of 30% at a deformation rate, cooled to room temperature at a rate of 30°C / s, heated to 880°C, kept warm for 30 minutes, finally cooled to room temperature at a rate of 5°C / s, then kept warm at 180°C for 120 minutes, and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0076] Comparative Example 9

[0077] Same as Example 1, except that: ① The tempering temperature is 160°C, and the specific preparation method steps are as follows: the raw material is smelted into molten iron, and then desulfurized by the KR method, and then LF refining and RH refining are performed. After the molten iron is refined, large slabs are continuously cast, and then the billet stack is slowly cooled for 48 hours. After the slow cooling is completed, the billet is heated to 1180°C and then kept warm for 5 minutes, cooled to 1150°C at a rate of 3°C / s, and then cooled at a rate of 5s -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s -1 The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 160°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0078] ② The tempering temperature is 200℃. The specific preparation method steps are as follows: the raw materials are melted into molten iron and then desulfurized by KR method, followed by LF refining and RH refining. After the molten iron is refined, large slabs are continuously cast, and then the billets are stacked and slowly cooled for 48h. After the slow cooling is completed, the billets are heated to 1180℃ and kept warm for 5min, cooled to 1150℃ at a speed of 3℃ / s, and then cooled at a speed of 5s. -1 The deformation rate is 20% for a single pass compression deformation, and then cooled to 860℃ at a rate of 5℃ / s, and then cooled to 860℃ at a rate of 5s -1 The steel plate is heated to 880°C, kept warm for 30 minutes, pre-cooled to 200°C at a rate of 40°C / s, and finally cooled to room temperature at a rate of 5°C / s. The steel plate is then kept warm at 200°C for 120 minutes and air-cooled to room temperature to obtain wear-resistant steel for oil mining.

[0079] The properties of the steel obtained in the examples and comparative examples were tested, and the results are shown in Table 1.

[0080] The wear resistance of steel is expressed in terms of wear quality and corrosion wear quality.

[0081] The detection method of wear mass loss is as follows:

[0082] The sample with the size of 2cm×2cm×5cm was ground, polished, cleaned, dried and weighed, and then tested using an abrasive wear tester. The sand content of the abrasive in the slurry was 70%, and the rest was distilled water. The abrasive was SiO2 with a particle size of 1μm, the wear load was 45N, and the wear time was 20min. After the experiment, the sample was cleaned, dried and weighed.

[0083] The detection methods of corrosion and wear quality are as follows:

[0084] The sample with the size of 2cm×2cm×5cm was ground, polished, cleaned, dried and weighed, and then tested using an abrasive wear tester. The sand content of the abrasive in the slurry was 70%, and the rest was a 5% NaCl solution. The abrasive was SiO2 with a particle size of 1μm, the wear load was 45N, and the wear time was 20min. After the experiment, the sample was cleaned, dried and weighed.

[0085] Table 1 Performance statistics of wear-resistant steel for oil mining prepared in Examples 1 to 3 and Comparative Examples 1 to 9

[0086]

[0087]

[0088] * indicates P<0.05 compared with Example 1, ** indicates P<0.01 compared with Example 1.

[0089] As can be seen from Table 1, the amount and ratio of alloying elements have a significant effect on the performance of steel. Although in some cases, increasing or changing the amount or ratio of certain alloying elements has an effect on improving the strength and hardness of steel, it will cause the material to be too brittle and hard, resulting in brittle fracture in actual use. In addition, it can be seen from the test data of the embodiments and comparative examples that the strict limitation of the cooling rate and the special design of multiple process steps in the preparation process of the steel of the present invention can improve the comprehensive wear resistance of the steel while ensuring that the steel has good strength.

[0090] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A wear-resistant steel for oil mining, characterized in that: The chemical composition and mass percentage of the wear-resistant steel used in petroleum mining are as follows: C 0.24%~0.38%, Si 0.10%~0.50%, Mn 0.35%~0.50%, Ti 0.02%~0.05%, B 0.001%~0.003%, 0.75%≤Cr+Mo+Ni≤3%, Nb+V≤0.05%, the balance is Fe and unavoidable impurities; Nb:V=1:(1~2.5).

2. The wear-resistant steel for oil mining according to claim 1, characterized in that: The chemical composition of the wear-resistant steel used in petroleum mining is 0.25% to 0.35% Mo and 0.01% to 0.02 Nb.

3. The wear-resistant steel for oil mining according to claim 1, characterized in that: The chemical composition of the wear-resistant steel used in petroleum mining is Nb:V=1:

2.

4. A method for preparing wear-resistant steel for petroleum mining as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: The raw materials are melted into molten iron and then pretreated. After the molten iron is refined, large slabs are continuously cast, and then the ingots are stacked and slowly cooled. After the slow cooling is completed, the ingots are heated and then rolled. After cooling, they are graded quenched and tempered to obtain wear-resistant steel for oil mining.

5. The preparation method according to claim 4, characterized in that: The pretreatment is desulfurization pretreatment.

6. The preparation method according to claim 4, characterized in that: The refining is LF refining and / or RH refining.

7. The preparation method according to claim 4, characterized in that: The rolling includes rough rolling and finish rolling.

8. The preparation method according to claim 4, characterized in that: The quenching is a stepwise quenching, wherein the steel plate is first heated to 880° C., kept at this temperature for 15 to 60 minutes, and then pre-cooled. After pre-cooling to the target temperature, final cooling is performed, and the quenching is completed after cooling to room temperature.

9. The preparation method according to claim 8, characterized in that: The temperature of the steel plate after precooling is 200°C to 300°C, the precooling speed is 20°C / s to 40°C / s, and the final cooling speed is 5°C / s to 10°C / s.

10. The preparation method according to claim 4, characterized in that: The tempering temperature is 180° C. and the holding time is 60 to 120 minutes.

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