Zirconium-titanium low-carbon low-alloy steel and method for producing the same

Abstract

The application discloses a zirconium-titanium low-carbon low-alloy steel and a preparation method thereof. The zirconium-titanium low-carbon low-alloy steel comprises the following components in percentage by mass: C: 0.05wt%-0.09wt%; Si: 0.08wt%-0.16wt%; Mn: 1.4wt%-2.2wt%; Cr: 0.22wt%-0.32wt%; Mo: 0.15wt%-0.24wt%; Cu: 0.02wt%-0.05wt%; Ti: 0.08wt%-0.16wt%; Zr: 0.05wt%-0.1wt%; N: 0.002wt%-0.006wt%; P: 0.01wt%-0.02wt%; S: ≤0.003wt%; and the balance of Fe and inevitable trace elements. The zirconium-titanium low-carbon low-alloy steel is treated by micro-zirconium and combined with titanium micro-alloying, so that the strength of the low-carbon low-alloy steel is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel smelting technology, and particularly relates to a zirconium-titanium low-carbon low-alloy steel and its preparation method. Background Technology

[0002] The TMCP production process for low-carbon, low-alloy high-strength steel combines microalloying technology with controlled rolling and cooling processes. Microalloying technology involves adding trace amounts of strong carbon and nitrogen elements such as niobium, titanium, and vanadium to steel to form carbonitrides. Simultaneously, controlled rolling and controlled cooling control the precipitation of these microalloying elements' carbonitrides, thereby exerting their grain-refining and precipitation-strengthening effects and improving the steel's performance.

[0003] However, titanium is highly reactive and easily combines with oxygen, nitrogen, and carbon in steel at high temperatures to form large inclusions with sharp edges. These inclusions are retained during subsequent heating and rolling processes, which adversely affect the fatigue resistance, ductility, toughness, weldability, and corrosion resistance of the steel, seriously impacting the performance stability of titanium low-carbon microalloyed steel. Summary of the Invention

[0004] This invention provides a zirconium-titanium low-carbon low-alloy steel and its preparation method. The zirconium-titanium low-carbon low-alloy steel of this invention adopts micro-zirconium treatment combined with titanium micro-alloying to enhance the strength of the low-carbon low-alloy steel.

[0005] In a first aspect, a zirconium-titanium low-carbon low-alloy steel is provided, wherein, by weight percentage, the components of the zirconium-titanium low-carbon low-alloy steel include: C: 0.05wt%~0.09wt%; Si: 0.08wt%~0.16wt%; Mn: 1.4wt%~2.2wt%; Cr: 0.22wt%~0.32wt%; Mo: 0.15wt%~0.24wt%; Cu: 0.02wt%~0.05wt%; Ti: 0.08wt%~0.16wt%; Zr: 0.05wt%~0.1wt%; N: 0.002wt%~0.006wt%; P: 0.01wt%~0.02wt%; S: ≤0.003wt%; and the balance being Fe and unavoidable trace elements.

[0006] The zirconium-titanium low-carbon alloy steel of the present invention adopts micro-zirconium treatment combined with titanium microalloying. Zr can partially or completely replace titanium in carbides, nitrides or carbonitrides in single titanium microalloyed steel, so that titanium can exist in the matrix in a solid solution as much as possible. Subsequently, when precipitating at low temperature, the amount of nano-scale carbides precipitated increases, thereby enhancing the strength of the microalloyed steel. This overcomes the problem of difficult control of the alloying effect of titanium in titanium low-carbon low-alloy steel, and can ensure the stable performance of the strengthening effect of titanium.

[0007] Furthermore, the zirconium-titanium low-carbon low-alloy steel of the present invention does not contain precious alloying elements such as vanadium and niobium, resulting in lower production costs. This not only improves the economic benefits of steel production enterprises but also contributes to the sustainable development of the steel industry.

[0008] In some embodiments, the zirconium-titanium low-carbon low-alloy steel comprises, by weight percentage: C: 0.06wt%~0.08wt%; Si: 0.11wt%~0.14wt%; Mn: 1.7wt%~1.85wt%; Cr: 0.24wt%~0.28wt%; Mo: 0.17wt%~0.20wt%; Cu: 0.03wt%~0.04wt%; Ti: 0.10wt%~0.13wt%; Zr: 0.07wt%~0.08wt%; N: 0.003wt%~0.004wt%; P: 0.01wt%~0.02wt%; S: ≤0.003wt%; and the balance being Fe and unavoidable trace elements; Preferably, the zirconium-titanium low-carbon low-alloy steel comprises, by weight percentage: C: 0.07wt%; Si: 0.13wt%; Mn: 1.73wt%; Cr: 0.24wt%; Mo: 0.19wt%; Cu: 0.03wt%; Ti: 0.13wt%; Zr: 0.08wt%; N: 0.003wt%; P: 0.01wt%~0.02wt%; S: ≤0.003wt%; and the balance being Fe and unavoidable trace elements.

[0009] In some embodiments, the microstructure of zirconium-titanium low-carbon low-alloy steel includes ferrite and bainite.

[0010] In some embodiments, the non-metallic inclusion level of the zirconium-titanium low-carbon low-alloy steel is ≤0.5; and / or, the grain size level of the zirconium-titanium low-carbon low-alloy steel is ≥10.

[0011] In some embodiments, the zirconium-titanium low-carbon low-alloy steel satisfies one or more of the following conditions (1) to (5): (1) the yield strength of the zirconium-titanium low-carbon low-alloy steel is 730MPa~830MPa; (2) the tensile strength of the zirconium-titanium low-carbon low-alloy steel is 830MPa~950MPa; (3) the yield strength ratio of the zirconium-titanium low-carbon low-alloy steel is ≤0.86; (4) the elongation after fracture of the zirconium-titanium low-carbon low-alloy steel is ≥15%; (5) the impact energy of the zirconium-titanium low-carbon low-alloy steel at -20℃ is ≥70J.

[0012] Secondly, a method for preparing zirconium-titanium low-carbon low-alloy steel includes: Refining raw material molten steel; The raw steel is subjected to LF refining to obtain LF refined steel, which contains the components of the first aspect; LF refined molten steel is continuously cast to obtain slabs; The slab is heated to obtain a heated slab. The heated slab is subjected to rough rolling and finish rolling in sequence to obtain a steel plate.

[0013] In some embodiments, during the steelmaking process, steel is tapped when the temperature reaches 1610°C to 1630°C, and active lime is added when 40% to 70% of the steel has been tapped to maintain the slag alkalinity and prevent phosphorus reversion; and / or, in the raw steel, C ≤ 0.03 wt% and P ≤ 0.01 wt%.

[0014] In some embodiments, refining LF refined molten steel includes: heating the raw molten steel and rapidly adding an aluminum source to deeply deoxidize the molten steel and slag and alloy it to obtain LF refined molten steel. In the alloying process, a zirconium source is added first and then a titanium source. Preferably, the zirconium source and the titanium source are added by adding alloy blocks or feeding cored wire.

[0015] In some embodiments, during the slab heating step, the heating temperature is 1230℃~1255℃, preferably 1245℃~1255℃; and / or, during the roughing rolling step, the roughing rolling start temperature is 1140℃~1180℃, preferably 1150℃~1180℃; and / or, during the roughing rolling step, the roughing rolling finish temperature is 1055℃~1085℃, preferably 1060℃~1080℃; and / or, during the finishing rolling step, the finishing rolling start temperature is 970℃~1020℃, preferably 980℃~1010℃; and / or, during the finishing rolling step, the finishing rolling finish temperature is 850℃~880℃, preferably 860℃~880℃.

[0016] In the above embodiments, the preparation method of this application, through special temperature settings during the slab heating and rolling process, allows Zr to partially or completely replace titanium in the carbides, nitrides or carbonitrides in single titanium microalloyed steel, so that titanium can exist in the matrix in a solid solution as much as possible. Subsequently, during low-temperature precipitation, the amount of nano-scale carbides precipitated increases, thereby enhancing the strength of the microalloyed steel.

[0017] In some embodiments, the preparation method may further include rapidly cooling the steel plate and then rolling it into a steel coil. Preferably, the rapid cooling temperature is 80°C / s to 100°C / s, and the coil is rolled after rapid cooling to 550°C to 580°C. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a metallographic image of zirconium-titanium low-carbon low-alloy steel according to an embodiment of the present invention. Detailed Implementation

[0020] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present invention and not to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the invention.

[0021] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0022] The foregoing description of this application is not intended to describe every disclosed embodiment or implementation. The following description illustrates exemplary embodiments in more detail. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. In each example, the enumeration is merely representative and should not be construed as exhaustive. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0023] Steel products, as essential raw materials for the national economy, are a significant indicator of industrial civilization and economic strength in the world today. As a crucial component of steel products, steel for construction machinery is increasingly being used in the industry, particularly in high-strength, low-alloy steel, driven by the trend towards lighter and larger industrial machinery. Thermomechanical processing (TMCP), one of the processes for producing high-strength, low-alloy steel, significantly promotes the production of high-quality steel materials and offers advantages such as resource conservation, energy saving, and emission reduction.

[0024] The TMCP production process for low-carbon, low-alloy high-strength steel combines microalloying technology with controlled rolling and cooling processes. Microalloying technology involves adding trace amounts of strong carbon and nitrogen elements such as niobium, titanium, and vanadium to steel to form carbonitrides. Simultaneously, by controlling rolling and cooling, the precipitation of these microalloying elements' carbonitrides is controlled, thereby exerting their grain-refining and precipitation-strengthening effects and improving the steel's performance.

[0025] China has abundant titanium ore resources compared to niobium and vanadium, and the cost is relatively low. Compared to niobium and vanadium, titanium, due to its chemical reactivity and strong affinity for oxygen, sulfur, nitrogen, and carbon, plays a crucial role in high-strength steel production during high-temperature homogenization. This is because titanium acts as a pinning agent, which niobium and vanadium cannot replicate through their carbides and nitrides, resulting in finer austenite grains. However, due to its high reactivity, titanium readily combines with oxygen, nitrogen, and carbon in steel at high temperatures to form large, angular inclusions. These inclusions are retained during subsequent heating and rolling processes, negatively impacting the steel's properties. Furthermore, they consume available titanium, adversely affecting the steel's fatigue resistance, ductility, toughness, weldability, and corrosion resistance, severely impacting the performance stability of titanium-based low-carbon low-alloy steel.

[0026] In view of the above-mentioned technical problems, the present invention provides a zirconium-titanium low-carbon low-alloy steel. The zirconium-titanium low-carbon low-alloy steel of the present invention adopts micro-zirconium treatment combined with titanium micro-alloying to enhance the strength of low-carbon low-alloy steel.

[0027] The zirconium-titanium low-carbon low-alloy steel provided in the embodiments of the present invention will be introduced first below.

[0028] According to this application, the composition of zirconium-titanium low-carbon low-alloy steel, by weight percentage, includes: C: 0.05wt%~0.09wt%; Si: 0.08wt%~0.16wt%; Mn: 1.4wt%~2.2wt%; Cr: 0.22wt%~0.32wt%; Mo: 0.15wt%~0.24wt%; Cu: 0.02wt%~0.05wt%; Ti: 0.08wt%~0.16wt%; Zr: 0.05wt%~0.1wt%; N: 0.002wt%~0.006wt%; P: 0.01wt%~0.02wt%; S: ≤0.003wt%; and the balance being Fe and unavoidable trace elements.

[0029] The inventors discovered that zirconium is more reactive than titanium, and both belong to Group IVB with similar properties. By adding an appropriate amount of zirconium to titanium microalloyed steel, at high temperatures, oxygen, nitrogen, sulfur, and other elements can combine with zirconium, replacing some of the titanium. At low temperatures, zirconium and titanium can combine with carbon to precipitate nano-sized TiC and ZrC, increasing precipitation strengthening. Furthermore, the inventors fully utilize the different solid solubility of ZrC, TiC, TiN, and ZrN precipitates in austenite. At high temperatures, the solid solubility product of ZrN is less than that of TiN. Through appropriate heating processes, small-sized ZrN, or Zr-rich TiN and ZrN particles, precipitate at high temperatures. These particles pin the austenite grain boundaries, hindering grain movement and thus preventing austenite grain growth. At relatively low temperatures, the solid solubility products of the two elements' carbides are more similar, allowing carbide particles to precipitate individually or in combination, thereby pinning the deformed austenite grain boundaries during hot deformation. During the homogenization and rolling processes, Zr can partially or completely replace titanium in carbides, nitrides, or carbonitrides in single titanium microalloyed steel, allowing titanium to exist in the matrix in a solid solution form as much as possible. Subsequently, during low-temperature precipitation, it increases the amount of nanoscale carbides precipitated, thereby enhancing the strength of the microalloyed steel. This overcomes the difficulty in controlling the alloying effect of titanium in titanium-based low-carbon low-alloy steel, ensuring the stable exertion of the strengthening effect of titanium.

[0030] Furthermore, the zirconium-titanium low-carbon low-alloy steel of the present invention does not contain precious alloying elements such as vanadium and niobium, resulting in lower production costs. This not only improves the economic benefits of steel production enterprises but also contributes to the sustainable development of the steel industry.

[0031] In some specific embodiments, the zirconium-titanium low-carbon low-alloy steel comprises, by weight percentage: C: 0.06wt%~0.08wt%; Si: 0.11wt%~0.14wt%; Mn: 1.7wt%~1.85wt%; Cr: 0.24wt%~0.28wt%; Mo: 0.17wt%~0.20wt%; Cu: 0.03wt%~0.04wt%; Ti: 0.10wt%~0.13wt%; Zr: 0.07wt%~0.08wt%; N: 0.003wt%~0.004wt%; P: 0.01wt%~0.02wt%; S: ≤0.003wt%; and the balance being Fe and unavoidable trace elements. Preferably, the zirconium-titanium low-carbon low-alloy steel comprises, by weight percentage: C: 0.07wt%; Si: 0.13wt%; Mn: 1.73wt%; Cr: 0.24wt%; Mo: 0.19wt%; Cu: 0.03wt%; Ti: 0.13wt%; Zr: 0.08wt%; N: 0.003wt%; P: 0.01wt%~0.02wt%; S: ≤0.003wt%; and the balance being Fe and unavoidable trace elements.

[0032] In some specific implementations, such as Figure 1 The image shown is a metallographic diagram of zirconium-titanium low-carbon low-alloy steel according to some preferred embodiments of this application. The metallographic structure of the zirconium-titanium low-carbon low-alloy steel includes ferrite and bainite.

[0033] In some specific embodiments, the non-metallic inclusion level of zirconium-titanium low-carbon low-alloy steel is ≤0.5; and / or, the grain size level of zirconium-titanium low-carbon low-alloy steel is ≥10.

[0034] In some specific embodiments, the zirconium-titanium low-carbon low-alloy steel meets one or more of the following conditions (1) to (5): (1) the yield strength of the zirconium-titanium low-carbon low-alloy steel is 730MPa~830MPa; (2) the tensile strength of the zirconium-titanium low-carbon low-alloy steel is 830MPa~950MPa; (3) the yield strength ratio of the zirconium-titanium low-carbon low-alloy steel is ≤0.86; (4) the elongation after fracture of the zirconium-titanium low-carbon low-alloy steel is ≥15%; (5) the impact energy of the zirconium-titanium low-carbon low-alloy steel at -20℃ is ≥70J.

[0035] Secondly, a method for preparing zirconium-titanium low-carbon low-alloy steel includes: Refining raw material molten steel; The raw steel is subjected to LF refining to obtain LF refined steel, which contains the components of the first aspect; LF refined molten steel is continuously cast to obtain slabs; The slab is heated to obtain a heated slab. The heated slab is subjected to rough rolling and finish rolling in sequence to obtain a steel plate.

[0036] In some specific embodiments, during the steelmaking process, steel is tapped when the temperature reaches 1610℃~1630℃, and active lime is added when 40%~70% of the steel has been tapped to maintain slag basicity and prevent phosphorus reversion; and / or, in the raw steel, C ≤ 0.03wt% and P ≤ 0.01wt%. For example, the mass percentage of C in the raw steel can be 0.005wt%, 0.008wt%, 0.01wt%, 0.015wt%, 0.02wt%, 0.025wt%, 0.03wt%, or any combination thereof, and the mass percentage of P in the raw steel can be 0.001wt%, 0.002wt%, 0.005wt%, 0.008wt%, 0.01wt%, or any combination thereof.

[0037] In some specific embodiments, refining LF refined molten steel includes: heating the raw molten steel and rapidly adding an aluminum source to deeply deoxidize the molten steel and slag and alloy it to obtain LF refined molten steel. In the alloying process, a zirconium source is added first and then a titanium source. Preferably, the zirconium source and the titanium source are added by feeding alloy blocks or cored wire.

[0038] In some specific embodiments, during the slab heating step, the heating temperature is 1230℃~1255℃, preferably 1245℃~1255℃. For example, the heating temperature can be any combination of 1230℃, 1235℃, 1240℃, 1245℃, 1250℃, 1255℃, or the above values; and / or, during the rough rolling step, the rough rolling start temperature is 1140℃~1180℃, preferably 1150℃~1180℃. For example, the rough rolling start temperature... The temperature can be any combination of 1140℃, 1145℃, 1150℃, 1155℃, 1160℃, 1165℃, 1170℃, 1175℃, 1180℃, or higher; and / or, in the roughing rolling step, the final rolling temperature is 1055℃~1085℃, preferably 1060℃~1080℃. For example, the final rolling temperature can be 1055℃, 1060℃, 1065℃, 1070℃, 1075℃, 1080℃, or higher. Any combination range of values; and / or, in the roughing step, the total reduction rate is 70%~80%, and after 7~12 passes of rolling, finishing rolling is performed. For example, the total reduction rate can be 70%, 72%, 75%, 78%, 80%, or any combination range of values ​​above; and / or, in the finishing rolling step, the finishing rolling start temperature is 970℃~1020℃, preferably 980℃~1010℃. For example, the finishing rolling start temperature is 970℃, 975℃, 980℃, 985℃, 990℃, etc. ℃, 995℃, 1000℃, 1005℃, 1010℃, or any combination of the above values; and / or, in the finishing rolling step, the finishing rolling temperature is 850℃~880℃, preferably 860℃~880℃, for example, the finishing rolling temperature can be 850℃, 855℃, 860℃, 865℃, 870℃, 875℃, 880℃, or any combination of the above values; and / or, the cumulative reduction rate is ≥80%, and the steel plate is rolled into a steel plate through 7~12 passes.

[0039] In the above specific embodiments, the preparation method of this application, through special temperature settings during the slab heating and rolling process, allows Zr to partially or completely replace titanium in the carbides, nitrides or carbonitrides in single titanium microalloyed steel, so that titanium can exist in the matrix in a solid solution as much as possible. Subsequently, during low-temperature precipitation, the amount of nano-scale carbides precipitated increases, thereby enhancing the strength of the microalloyed steel.

[0040] In some embodiments, the preparation method may further include rapidly cooling the steel plate and then rolling it into a steel coil. Preferably, the rapid cooling temperature is 80℃ / s to 100℃ / s, and the coil is rolled after rapid cooling to 550℃ to 580℃. For example, the temperature of the rapid cooling zone can be any combination of 80℃ / s, 82℃ / s, 85℃ / s, 88℃ / s, 90℃ / s, 95℃ / s, 100℃ / s, or the above values, and the coil can be rolled after rapid cooling to any combination of 550℃, 555℃, 560℃, 565℃, 570℃, 575℃, 580℃, or the above values.

[0041] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0042] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are for illustrative purposes only.

[0043] Because various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all raw materials used in the examples are commercially available or prepared by conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0044] This specific embodiment is based on a top-and-bottom combined blowing converter of a steel plant, and all percentages involved in the embodiments are mass percentages.

[0045] Example 1 A zirconium-titanium low-carbon low-alloy steel is prepared by the following method: Molten iron and scrap steel are smelted into molten steel with a composition of C: 0.02wt%, P: 0.01wt%, and S: 0.015wt%. The steel is tapped when the temperature reaches 1670℃. When 60% of the steel has been tapped, quicklime is added to maintain the basicity of the slag and prevent phosphorus reversion. At the same time, a sliding plate mechanism is used to block slag during tapping, and the amount of slag is strictly controlled.

[0046] After tapping, the ladle is transported to the LF refining station for alloying. After the ladle is transported to the refining station, it is heated. Five minutes before the LF heating ends, aluminum wire is added. After the aluminum wire is fed in, the Al content of the molten steel is 0.025%. Argon gas is gently blown for 4 minutes, during which the alloy is fine-tuned. Then, zirconium-iron alloy is immediately fed in, and argon gas is gently blown for 1 minute. Then, titanium-iron alloy is immediately fed in. Finally, LF refined molten steel with qualified composition is obtained.

[0047] The LF refined steel is sent to the continuous casting machine for continuous casting to obtain a continuously cast billet with a thickness of 240mm. The continuously cast billet is placed in a natural gas heating furnace and heated to 1240℃ and held for 42min.

[0048] The heated slab is then rolled on a hot continuous rolling mill. The initial rolling temperature of the roughing mill is controlled at 1170℃, and the final rolling temperature is controlled at 1070℃. The roughing mill is rolled in 7 passes to obtain an intermediate slab with a thickness of 55mm. The intermediate slab is then finished rolled in 7 passes. The initial rolling temperature of the finish rolling mill is controlled at 980℃, and the final rolling temperature is controlled at 860℃. The finish rolling mill is rolled in 7 passes to obtain a hot-rolled strip with a thickness of 10mm. Water cooling is used between the finish mill stands.

[0049] The hot-rolled strip was then cooled using laminar flow cooling at a rate of 90°C / s. The cooled strip was then coiled at a temperature of 560°C to obtain sheet-like coiled zirconium-titanium low-carbon low-alloy steel. The chemical composition of the zirconium-titanium low-carbon low-alloy steel is shown in Table 1.

[0050] Table 1 Table 2 Examples 2-4 Following the method of Example 1, different steel compositions were used, and the soaking temperature, roughing rolling start temperature, roughing rolling finish temperature, finishing rolling start temperature, finishing rolling finish temperature, cooling rate, coiling temperature, and thickness of hot-rolled strip are shown in Tables 1 and 2, respectively.

[0051] Comparative Example 1 Following the method of Example 1, different steel compositions (without adding zirconium) were used. The soaking temperature, roughing rolling start temperature, roughing rolling finish temperature, finishing rolling start temperature, finishing rolling finish temperature, cooling rate, coiling temperature, and thickness of hot-rolled strip are shown in Tables 1 and 2, respectively.

[0052] Samples were taken from the finished strip steel obtained in Examples 1-4 and Comparative Examples 1-2 above, and the yield strength, tensile strength and total elongation were tested according to the method specified in GB / T228. The test results are shown in Table 3.

[0053] Table 3 The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A zirconium-titanium low-carbon low-alloy steel, characterized in that, The components of the zirconium-titanium low-carbon low-alloy steel, by weight percentage, include: C: 0.05wt%~0.09wt%, Si: 0.08wt%~0.16wt%, Mn: 1.4wt%~2.2wt%, Cr: 0.22wt%~0.32wt%, Mo: 0.15wt%~0.24wt%, Cu: 0.02wt%~0.05wt%, Ti: 0.08wt%~0.16wt%, Zr: 0.05wt%~0.1wt%, N: 0.002wt%~0.006wt%, P: 0.01wt%~0.02wt%, S: ≤0.003wt%; and the balance Fe and unavoidable trace elements.

2. The zirconium-titanium low-carbon low-alloy steel according to claim 1, characterized in that, The components of the zirconium-titanium low-carbon low-alloy steel, by weight percentage, include: C: 0.06wt%~0.08wt%, Si: 0.11wt%~0.14wt%, Mn: 1.7wt%~1.85wt%, Cr: 0.24wt%~0.28wt%, Mo: 0.17wt%~0.20wt%, Cu: 0.03wt%~0.04wt%, Ti: 0.10wt%~0.13wt%, Zr: 0.07wt%~0.08wt%, N: 0.003wt%~0.004wt%, P: 0.01wt%~0.02wt%, S: ≤0.003wt%; and the balance Fe and unavoidable trace elements; Preferably, the zirconium-titanium low-carbon low-alloy steel comprises, by weight percentage: C: 0.07wt%, Si: 0.13wt%, Mn: 1.73wt%, Cr: 0.24wt%, Mo: 0.19wt%, Cu: 0.03wt%, Ti: 0.13wt%, Zr: 0.08wt%, N: 0.003wt%, P: 0.01wt%~0.02wt%, S: ≤0.003wt%; and the balance being Fe and unavoidable trace elements.

3. The zirconium-titanium low-carbon low-alloy steel according to claim 1 or 2, characterized in that, The microstructure of the zirconium-titanium low-carbon low-alloy steel includes ferrite and bainite.

4. The zirconium-titanium low-carbon low-alloy steel according to claim 1 or 2, characterized in that, The non-metallic inclusion level of the zirconium-titanium low-carbon low-alloy steel is ≤0.

5. And / or, the grain size level of the zirconium-titanium low-carbon low-alloy steel is ≥10.

5. The zirconium-titanium low-carbon low-alloy steel according to claim 1 or 2, characterized in that, The zirconium-titanium low-carbon low-alloy steel satisfies one or more of the following conditions (1) to (5): (1) The yield strength of the zirconium-titanium low-carbon low-alloy steel is 730MPa~830MPa; (2) The tensile strength of the zirconium-titanium low-carbon low-alloy steel is 830MPa~950MPa; (3) The yield strength ratio of the zirconium-titanium low-carbon low-alloy steel is ≤0.86; (4) The elongation after fracture of the zirconium-titanium low-carbon low-alloy steel is ≥15%; (5) The impact energy of the zirconium-titanium low-carbon low-alloy steel at -20℃ is ≥70J.

6. A method for preparing zirconium-titanium low-carbon low-alloy steel as described in any one of claims 1 to 5, characterized in that, include: Refining raw material molten steel; The raw steel is subjected to LF refining to obtain LF refined steel, wherein the LF refined steel contains the components as described in any one of claims 1-5; LF refined molten steel is continuously cast to obtain slabs; The slab is heated to obtain a heated slab. The heated slab is subjected to rough rolling and finish rolling in sequence to obtain a steel plate.

7. The preparation method according to claim 6, characterized in that, In the process of refining raw material molten steel, the steel is tapped when the temperature reaches 1610℃~1630℃, and active lime is added when 40%~70% of the steel is tapped to maintain the alkalinity of the slag and prevent phosphorus reversion. And / or, in the molten steel of the raw material, C ≤ 0.03 wt% and P ≤ 0.01 wt%.

8. The preparation method according to claim 6, characterized in that, The refining of LF refined molten steel includes: heating the raw molten steel and rapidly adding an aluminum source to deeply deoxidize the molten steel and slag and then alloying them to obtain the LF refined molten steel. During alloying, a zirconium source is added first and then a titanium source. Preferably, the zirconium source and the titanium source are added by adding alloy blocks or feeding cored wire.

9. The preparation method according to claim 6, characterized in that, In the step of heating the slab, the heating temperature is 1230℃~1255℃, preferably 1245℃~1255℃; And / or, in the roughing step, the roughing temperature is 1140℃~1180℃, preferably 1150℃~1180℃; And / or, in the roughing rolling step, the final rolling temperature is 1055℃~1085℃, preferably 1060℃~1080℃; And / or, in the finishing rolling step, the finishing rolling start temperature is 970℃~1020℃, preferably 980℃~1010℃; And / or, in the finishing rolling step, the finishing rolling temperature is 850℃~880℃, preferably 860℃~880℃.

10. The preparation method according to claim 6, characterized in that, It also includes rapidly cooling the steel plate and then rolling it into a steel coil. Preferably, the rapid cooling temperature is 80℃ / s~100℃ / s, and the coil is rolled after being rapidly cooled to 550℃~580℃.

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