Method for water toughening of high manganese austenitic wear resistant steel coils

Abstract

This application discloses a method for water-toughening high-manganese austenitic wear-resistant steel coils. The method includes: coiling steel obtained from precision rolling to obtain high-manganese austenitic wear-resistant steel coils; heating the high-manganese austenitic wear-resistant steel coils to a first temperature and holding it at the first temperature for 2.5h-3.5h to obtain pretreated high-manganese austenitic wear-resistant steel coils, wherein the first temperature ranges from 1050℃ to 1550℃; and water-toughening the pretreated high-manganese austenitic wear-resistant steel coils, reducing the temperature of the pretreated high-manganese austenitic wear-resistant steel coils from the first temperature to a second temperature, wherein the cooling rate of the water-toughening treatment is 28℃ / min-70℃ / min, and the second temperature ranges from ≤200℃, to obtain water-toughened high-manganese austenitic wear-resistant steel coils. This method can achieve solid solution of carbides in high-manganese austenitic wear-resistant steel coils, improve or salvage high-manganese austenitic wear-resistant steel coils with coarse columnar crystal structure, reduce scrap rate, and improve the plasticity and toughness of high-manganese austenitic wear-resistant steel coils.

Description

Technical Field

[0001] This application relates to the field of heat treatment, specifically to a method for water quenching of high-manganese austenitic wear-resistant steel coils. Background Technology

[0002] High-manganese austenitic wear-resistant steel is widely used in railways, building materials, mining machinery, metallurgy, and other fields due to its excellent work hardening properties. However, the high manganese content, low thermal conductivity, and significant temperature difference between the solid and liquid phases in high-manganese austenitic wear-resistant steel lead to slow solidification, making it prone to forming coarse columnar crystal structures and significantly increasing carbides at grain boundaries. This greatly reduces the plasticity and toughness of high-manganese austenitic wear-resistant steel. Furthermore, the proportion of coarse columnar crystal structures in high-manganese austenitic wear-resistant steel coils produced by current processes is relatively high, resulting in a high scrap rate.

[0003] Therefore, it is essential to address or improve the problem of coarse columnar crystal structure in high-manganese austenitic wear-resistant steel coils. Summary of the Invention

[0004] This application provides a method for water toughening treatment of high-manganese austenitic wear-resistant steel coils, which can achieve solid solution of carbides in high-manganese austenitic wear-resistant steel coils, improve or salvage high-manganese austenitic wear-resistant steel coils with coarse columnar crystal structure, reduce scrap rate, and improve the plasticity and toughness of high-manganese austenitic wear-resistant steel coils.

[0005] This application provides a method for water-toughening high-manganese austenitic wear-resistant steel coils, comprising: coiling high-manganese austenitic wear-resistant steel coils obtained by precision rolling; heating the high-manganese austenitic wear-resistant steel coils to a first temperature and holding them at the first temperature for 2.5h-3.5h to obtain pretreated high-manganese austenitic wear-resistant steel coils, wherein the first temperature ranges from 1050℃ to 1550℃; and water-toughening the pretreated high-manganese austenitic wear-resistant steel coils, wherein the temperature of the pretreated high-manganese austenitic wear-resistant steel coils is reduced from the first temperature to a second temperature, wherein the cooling rate of the water-toughening treatment is 28℃ / min-70℃ / min, and the second temperature ranges from 25℃ to 200℃ to obtain water-toughened high-manganese austenitic wear-resistant steel coils.

[0006] According to one aspect of the embodiments of this application, the heat treatment includes a first heating stage, a second heating stage, a third heating stage, and a fourth heating stage; the first heating stage includes heating the steel coil from 0°C-25°C to 45°C-55°C, the second heating stage includes heating the steel coil from 45°C-55°C to 290°C-310°C, the third heating stage includes heating the steel coil from 290°C-310°C to 690°C-710°C, and the fourth heating stage includes heating the steel coil from 690°C-710°C to the first temperature.

[0007] According to one aspect of the embodiments of this application, the heating rate of the second heating stage is 75℃ / h to 85℃ / h, the heating rate of the third heating stage is 90℃ / h to 110℃ / h, and the heating rate of the fourth heating stage is 55℃ / h to 65℃ / h.

[0008] According to one aspect of the embodiments of this application, a gas-fired furnace is used to heat-treat high-manganese austenitic wear-resistant steel coils.

[0009] According to one aspect of the embodiments of this application, in the step of heating the high-manganese austenitic wear-resistant steel coil to a first temperature, the high-manganese austenitic wear-resistant steel coil comprises the following chemical composition, based on the total mass of the high-manganese austenitic wear-resistant steel coil as 100%: C: 0.9%-1.2%, Mn: 10%-14%, Si: 0.3%-0.6%, 0≤P≤0.05%, 0≤S≤0.02%, Al: 0.02%-0.1%, with the remainder being iron and unavoidable impurities.

[0010] According to one aspect of the embodiments of this application, the method further includes: continuous casting before finishing rolling, billet heating, and hot rolling treatment.

[0011] According to one aspect of the embodiments of this application, the superheat of the molten steel in the continuous casting process is 15°C-50°C.

[0012] According to one aspect of the embodiments of this application, the casting speed of the billet in the continuous casting process is 0.6m / s-1.3m / s.

[0013] According to one aspect of the embodiments of this application, the temperature of the cooling water in the crystallizer during the continuous casting process is 4°C-8°C; the ratio of the flow rate of the cooling water on the wide side to the flow rate of the cooling water on the narrow side of the crystallizer during the continuous casting process is 0.7 times to 0.9 times the ratio of the width dimension to the narrow dimension of the cast slab.

[0014] According to one aspect of the embodiments of this application, in the continuous casting process, the secondary cooling zone adopts ultra-weak cooling, and the specific water volume of the cooling water in the secondary cooling zone is 0.25L / Kg steel to 0.68L / Kg steel.

[0015] According to one aspect of the embodiments of this application, the temperature of the billet in the straightening zone is 850°C-950°C.

[0016] According to one aspect of the embodiments of this application, the secondary cooling zone is stirred during the continuous casting process; and argon blowing is used for continuous casting under protection during the continuous casting process.

[0017] The method for water toughening of high-manganese austenitic wear-resistant steel coils in this application involves first coiling the finished steel to obtain high-manganese austenitic wear-resistant steel coils; then, heating the high-manganese austenitic wear-resistant steel coils to 1050℃-1550℃ and holding them at 1050℃-1550℃ for 2.5h-3.5h; and then water toughening the high-manganese austenitic wear-resistant steel coils at a cooling rate of 28℃ / min-70℃ / min to reduce the temperature of the high-manganese austenitic wear-resistant steel coils to less than or equal to 200℃. This achieves solid solution of carbides in the high-manganese austenitic wear-resistant steel coils, thereby improving or salvaging the high-manganese austenitic wear-resistant steel coils with coarse columnar crystal structures, reducing the scrap rate, and improving the plasticity and toughness of the high-manganese austenitic wear-resistant steel coils. Attached Figure Description

[0018] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0019] Figure 1 This is a schematic diagram of the water toughening process for high-manganese austenitic wear-resistant steel coils provided in the embodiments of this application.

[0020] Figure 2 This is a metallographic image of the steel coil at the 20μm scale before water toughening treatment in Example 1 of this application.

[0021] Figure 3 This is a metallographic image of the steel coil at the 50μm scale after water toughening treatment in Example 1 of this application. Detailed Implementation

[0022] The features and exemplary embodiments of various aspects of this application will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a comprehensive understanding of this application. However, it will be apparent to those skilled in the art that this application can be implemented without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of this application by illustrating examples. In the accompanying drawings and the following description, at least some well-known structures and techniques are not shown to avoid unnecessarily obscuring the application; and, for clarity, the dimensions of some structures may be exaggerated. Furthermore, the features, structures, or characteristics described below can be combined in any suitable manner in one or more embodiments.

[0023] It should be noted that, in this application, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0024] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application). Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C and the test pressure is standard atmospheric pressure.

[0025] The list of items connected by the term "one or more" can mean any combination of the listed items. The term "multiple" means two or more.

[0026] High-manganese austenitic wear-resistant steel possesses excellent work hardening properties. However, high-manganese steel after conventional hot rolling exhibits completely different microstructures, containing a large amount of ferrite and large grain boundary cementite, making it very brittle and even unusable in the form of rolled coils. Therefore, to achieve excellent work hardening properties in high-manganese austenitic wear-resistant steel, this application applies water quenching treatment after finishing rolling following hot rolling. However, conventional manufacturing processes result in high-manganese austenitic wear-resistant steel coils with coarse columnar crystal structures, and the proportion of columnar crystals in the microstructure is relatively high, leading to a high scrap rate for the steel coils.

[0027] Figure 1 This is a schematic diagram of the water toughening process for high-manganese austenitic wear-resistant steel coils provided in the embodiments of this application.

[0028] like Figure 1 As shown in the embodiment of this application, a method for water quenching of high-manganese austenitic wear-resistant steel coils is provided, including the following steps: S10: The steel obtained from precision rolling is coiled to obtain high-manganese austenitic wear-resistant steel coils; S20: The high-manganese austenitic wear-resistant steel coil is heated to the first temperature and held at the first temperature for 2.5h-3.5h to obtain the pretreated high-manganese austenitic wear-resistant steel coil. The first temperature range is 1050℃-1550℃. S30: Water quenching is performed on the pretreated high-manganese austenitic wear-resistant steel coil to reduce the temperature of the pretreated high-manganese austenitic wear-resistant steel coil from a first temperature to a second temperature. The cooling rate of the water quenching is 28℃ / min-70℃ / min, and the second temperature range is ≤200℃, thus obtaining the water-quenched high-manganese austenitic wear-resistant steel coil.

[0029] The water-toughening method for high-manganese austenitic wear-resistant steel coils provided in this application involves first coiling the precision-rolled steel to obtain high-manganese austenitic wear-resistant steel coils; then, the high-manganese austenitic wear-resistant steel coils are heated to 1050℃-1550℃ and held at 1050℃-1550℃ for 2.5h-3.5h, followed by water-toughening at a cooling rate of 28℃ / min-70℃ / min to reduce the temperature of the high-manganese austenitic wear-resistant steel coils to less than or equal to 200℃. This achieves solid solution of carbides in the high-manganese austenitic wear-resistant steel coils, improves or salvages high-manganese austenitic wear-resistant steel coils with coarse columnar crystal structures, reduces the scrap rate, and improves the plasticity and toughness of the high-manganese austenitic wear-resistant steel coils.

[0030] The inventors of this application discovered that carbides precipitated along austenite grain boundaries reduce the toughness of high-manganese austenitic wear-resistant steel. To eliminate carbides, this application developed a method for water-toughening high-manganese austenitic wear-resistant steel coils, including water-toughening treatment. Water-toughening treatment involves heating the steel to an austenitic temperature and holding it at that temperature for a period of time, causing the carbides in the as-cast structure to essentially dissolve into the austenite, followed by rapid water cooling to obtain a single, supercooled austenitic structure.

[0031] The water toughening method for high-manganese austenitic wear-resistant steel coils in this application embodiment achieves the re-dissolution of carbides in the steel coil by controlling the first temperature within the range of 1050℃-1550℃. By controlling the second temperature within the range of less than or equal to 200℃, the precipitation range of carbides in the steel coil can be avoided, thus achieving solid solution of carbides in the high-manganese austenitic wear-resistant steel coil. This improves or salvages high-manganese austenitic wear-resistant steel coils with coarse columnar crystal structures, reduces the scrap rate, and improves the plasticity and toughness of the high-manganese austenitic wear-resistant steel coils.

[0032] It is understood that the apparatus for water toughening of steel coils in the embodiments of this application includes, but is not limited to, conventional water cooling devices. In some embodiments, water toughening of pretreated high-manganese austenitic wear-resistant steel coils is performed in a water tank.

[0033] In this embodiment, the thickness of the steel coil can be 3.0 mm to 10.0 mm, and the weight of the steel coil can be 10 tons to 30 tons.

[0034] For example, the apparatus for heating steel coils in this application embodiment can be one or more of a box-type resistance furnace, a gas heating furnace, or a natural gas heating furnace.

[0035] The as-cast microstructure of high-manganese austenitic wear-resistant steel consists of austenite, carbides, and a small amount of pearlite, a phase transformation product. The purpose of heat treatment on the steel coil is to heat the high-manganese austenitic wear-resistant steel coil to the austenitic temperature, thereby dissolving the carbides in the as-cast microstructure into the austenitic microstructure. Then, water quenching is performed for rapid cooling, thereby obtaining a single supercooled austenitic microstructure, eliminating the carbides in the high-manganese austenitic wear-resistant steel coil, and thus enhancing the toughness of the high-manganese austenitic wear-resistant steel coil.

[0036] In some alternative embodiments, the heating process includes a first heating stage, a second heating stage, a third heating stage, and a fourth heating stage.

[0037] In some alternative embodiments, the first heating stage may include heating the steel coil from 0°C-25°C to 45°C-55°C, the second heating stage may include heating the steel coil from 45°C-55°C to 290°C-310°C, the third heating stage may include heating the steel coil from 290°C-310°C to 690°C-710°C, and the fourth heating stage may include heating the steel coil from 690°C-710°C to the first temperature.

[0038] The water quenching method for high-manganese austenitic wear-resistant steel coils in this application divides the heat treatment into the aforementioned heating stages. The first heating stage ensures the high-manganese austenitic wear-resistant steel coil reaches the basic required temperature, preventing performance variations during subsequent heating due to insufficient temperature. The second heating stage further raises the temperature to 290℃-310℃, allowing the ε-martensite formed during processing to rapidly transform into austenite through a significant expansion effect at 290℃-310℃. This ensures the transformation is fully completed, releases internal stress from processing, and reduces damage to the high-manganese austenitic wear-resistant steel coil from subsequent heating stages. The third heating stage raises the temperature to 690℃-710℃ and then quickly skips this temperature range to prevent carbide precipitation within this range. The fourth heating stage involves heating the high-manganese austenitic wear-resistant steel coil to 1050℃-1550℃ to allow the carbides to dissolve within this temperature range, and then holding it at this temperature for 2.5h-3.5h to ensure that the carbides are fully dissolved.

[0039] In some optional embodiments, the heating rate of the first heating stage can be 1℃ / min to 20℃ / min, and the embodiments of this application do not explicitly limit it. The heating rate of the second heating stage is 75℃ / h to 85℃ / h, the heating rate of the third heating stage is 90℃ / h to 110℃ / h, and the heating rate of the fourth heating stage can be 55℃ / h to 65℃ / h.

[0040] The water toughening method for high-manganese austenitic wear-resistant steel coils in this application embodiment uses a heating rate in the second heating stage to keep the performance of the high-manganese austenitic wear-resistant steel coils relatively stable. By using heating rates in the third and fourth heating stages, the temperature of the high-manganese austenitic wear-resistant steel coils can quickly pass through the temperature range for carbide precipitation, effectively reducing carbide precipitation.

[0041] In some alternative embodiments, a gas-fired furnace is used to heat-treat the high-manganese austenitic wear-resistant steel coil.

[0042] In some alternative embodiments, the first heating stage can be free heating. For example, the high-manganese austenitic wear-resistant steel coil can be heated from 0°C-25°C to 45°C-55°C at a heating rate of 1°C / min to 20°C / min.

[0043] The water quenching method for high-manganese austenitic wear-resistant steel coils in this application embodiment controls the heating rate of each heating stage. By controlling the heating rate of the first and second heating stages, the high-manganese austenitic wear-resistant steel coil can be rapidly heated to the first temperature through the heating rates of the third and fourth heating stages while maintaining the performance of the high-manganese austenitic wear-resistant steel coil. This avoids prolonged stay in the second and third heating stages, which would cause a large amount of carbides to precipitate and reduce the carbide content.

[0044] The water quenching method for high-manganese austenitic wear-resistant steel coils in this application embodiment achieves austenitic treatment of the steel coil through the above-mentioned heat treatment, causing the carbides in the steel coil to dissolve back. Because high-manganese steel has very low thermal conductivity, without the above-mentioned heat treatment and heat preservation, the internal and external temperatures of the high-manganese austenitic wear-resistant steel coil will be inconsistent, leading to cracking of the steel coil due to thermal stress, thereby affecting the service life of the high-manganese austenitic wear-resistant steel coil.

[0045] In some alternative embodiments, after the steel coil is kept at 1050℃-1550℃ for 2.5h-3.5h, it is quickly hoisted into a water tank for water toughening treatment.

[0046] In some optional embodiments, the high-manganese austenitic wear-resistant steel coil is kept at 1050℃-1550℃ for 2.5h-3.5h and the time between the coil being hoisted into the water tank for water toughening is minimized. After the high-manganese austenitic wear-resistant steel coil is kept at 1050℃-1550℃ for 2.5h-3.5h, it is quickly hoisted into the aqueous phase for water toughening. The high-manganese austenitic wear-resistant steel coil can be hoisted out of the water tank when its temperature reaches ≤200℃. After testing, the carbides in the original high-manganese austenitic wear-resistant steel coil did not precipitate again at the grain boundaries after water toughening, and the plasticity and toughness of the steel coil were significantly improved.

[0047] In some optional embodiments, in the step of heating the high-manganese austenitic wear-resistant steel coil to a first temperature, the high-manganese austenitic wear-resistant steel coil, based on 100% of its total mass, comprises the following chemical composition: C: 0.9%-1.2%, Mn: 10%-14%, Si: 0.3%-0.6%, 0≤P≤0.05%, 0≤S≤0.02%, Al: 0.02%-0.1%, with the remainder being iron and unavoidable impurities.

[0048] The specific principles for controlling the constituent elements of the high-manganese austenitic wear-resistant steel coil provided in this application embodiment are as follows: Carbon can improve the hardenability of high-manganese austenitic wear-resistant steel coils and has a strong solid solution strengthening effect. Increased carbon content improves wear resistance but reduces impact toughness. In high-manganese steel, the combination of carbon and manganese promotes work hardening and improves wear resistance. Therefore, in the embodiments of this application, the carbon mass content is controlled within the range of 0.9%-1.2%.

[0049] Manganese is a weak carbide-forming element and is usually dissolved in steel, providing solid solution strengthening. Manganese is a key element in stabilizing austenite, increasing the impact toughness of steel, promoting austenite grain growth, and easily forming columnar crystals. When the mass ratio of manganese to carbon is <10%, carbides are distributed in the austenite matrix, increasing wear resistance but decreasing toughness, making it prone to fracture during use. When the mass ratio of manganese to carbon is >10%, water toughening treatment can produce a single austenite structure, giving the steel coil both good toughness and good wear resistance. Therefore, to ensure good strength and toughness in the steel, the manganese content in the embodiments of this application is controlled within the range of 10%-14%.

[0050] Silicon is typically dissolved in steel, providing solid solution strengthening and improving its strength. In high-manganese steel, silicon can act as a deoxidizer; however, when the silicon content exceeds 0.6% by mass, it promotes carbide coarsening and reduces wear resistance. Therefore, in the embodiments of this application, the silicon content is controlled between 0.3% and 0.6% by mass.

[0051] Aluminum is a ferrite stabilizing element, which can promote the formation of ferrite structure, reduce the work hardening ability of high manganese steel, reduce carbon activity, increase carbon solubility in austenite, and reduce carbide precipitation. In the embodiments of this application, the mass content of aluminum is controlled within the range of 0.02%-0.1%.

[0052] Phosphorus and sulfur are harmful impurity elements in steel. Excessive phosphorus and sulfur content can significantly reduce the ductility, toughness, and weldability of steel. Therefore, the phosphorus and sulfur content should be minimized as much as possible. In this application, the phosphorus content is set to 0 ≤ P ≤ 0.05%, and the sulfur content is set to 0 ≤ S ≤ 0.02%.

[0053] In some optional embodiments, the method may further include: continuous casting prior to finish rolling, billet heating, and hot rolling. The hot rolling process includes rough rolling and finish rolling of the heated billet.

[0054] In some optional embodiments, the superheat of the molten steel during the continuous casting process is 15°C-50°C. Exemplarily, the superheat of the molten steel during casting can be 15°C, 16°C, 18°C, 20°C, 21°C, 23°C, 25°C, 28°C, 30°C, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, 49°C, or 50°C.

[0055] The water toughening method for high-manganese austenitic wear-resistant steel coils in this application embodiment, by setting the superheat of the molten steel during the continuous casting process within the aforementioned range, can prevent excessively high casting temperatures from causing the billet shell to become thinner upon exiting the crystallizer, thereby preventing steel leakage. Furthermore, excessively high superheat of the molten steel can also lead to the development of columnar crystals in the billet. In addition, setting the superheat of the molten steel within the aforementioned range during the casting process can also prevent excessively low temperatures during the continuous casting process from causing nozzle blockage, resulting in interruption of continuous casting and defects such as cracks on the surface of the continuously cast billet.

[0056] In some optional embodiments, the casting speed of the billet in the continuous casting step is 0.6 m / s-1.3 m / s. Exemplarily, the casting speed of the billet in the continuous casting step can be 0.65 m / s, 0.7 m / s, 0.75 m / s, 0.8 m / s, 0.84 m / s, 0.88 m / s, 0.9 m / s, 1.0 m / s, 1.05 m / s, 1.1 m / s, 1.2 m / s, or 1.25 m / s.

[0057] In some alternative embodiments, the temperature of the cooling water in the crystallizer during the continuous casting process is 4°C-8°C. Exemplarily, the temperature of the cooling water in the crystallizer during the continuous casting process can be 4.5°C, 5°C, 5.4°C, 5.6°C, 6°C, 6.3°C, 6.5°C, 6.8°C, 7.0°C, 7.5°C, or 7.9°C.

[0058] The water quenching method for high-manganese austenitic wear-resistant steel coils in this application embodiment controls the temperature of the cooling water in the crystallizer within the above-mentioned range, which prevents the billet shell from leaking due to insufficient cooling, and also prevents the billet shell from developing shape defects and cracks due to excessive cooling.

[0059] In some alternative embodiments, the ratio of the wide-face cooling water flow rate to the narrow-face cooling water flow rate of the crystallizer in the continuous casting step is 0.7 to 0.9 times the ratio of the wide-face dimension to the narrow-face dimension of the cast slab.

[0060] The water toughening method for high-manganese austenitic wear-resistant steel coils provided in this application embodiment controls the ratio of cooling water flow rate on the wide side of the crystallizer to cooling water flow rate on the narrow side to be 0.7 to 0.9 times the ratio of the wide side size to the narrow side size of the cast slab, so that the cast slab can be effectively cooled without producing columnar crystals, shape defects, or cracks.

[0061] In some optional embodiments, the secondary cooling zone in the continuous casting process employs ultra-weak cooling, with a cooling rate of 0.25 L / kg steel to 0.68 L / kg steel. The secondary cooling zone can use cooling water or mist to cool the continuously cast slab. Exemplarily, the cooling rate of the secondary cooling zone can be 0.25 L / kg steel, 0.28 L / kg steel, 0.30 L / kg steel, 0.32 L / kg steel, 0.35 L / kg steel, 0.38 L / kg steel, 0.4 L / kg steel, 0.43 L / kg steel, 0.45 L / kg steel, 0.48 L / kg steel, 0.5 L / kg steel, 0.54 L / kg steel, 0.59 L / kg steel, 0.6 L / kg steel, 0.63 L / kg steel, 0.65 L / kg steel, or 0.68 L / kg steel.

[0062] In the water quenching method for high-manganese austenitic wear-resistant steel coils provided in this application embodiment, the secondary cooling zone adopts ultra-weak cooling, which allows the billet to cool slowly and expands the central equiaxed crystal zone.

[0063] In some alternative embodiments, water spraying is stopped after the billet enters the straightening section.

[0064] In some alternative embodiments, the temperature of the billet in the straightening zone can be 850°C-950°C.

[0065] The water quenching method for high-manganese austenitic wear-resistant steel coils provided in this application can avoid the low-temperature brittle zone of the steel and further prevent the generation of cracks by controlling the temperature of the billet in the straightening zone within the range of 850℃-950℃.

[0066] In some alternative embodiments, the secondary cooling zone is stirred during the continuous casting step.

[0067] In the water quenching method for high-manganese austenitic wear-resistant steel coils provided in this application embodiment, stirring the secondary cooling zone can break up the dendrites at the front of the columnar crystals. Using these broken dendrites as equiaxed crystal nuclei, the equiaxed crystal zone in the center of the cast billet can be expanded, eliminating central segregation, porosity, and shrinkage cavities. Simultaneously, it can also cause inclusions in the liquid phase to float to the surface, reducing the accumulation of inclusions on the outer arc. Optionally, an electromagnetic stirring device can be used to perform alkaline stirring treatment on the cast billet in the secondary cooling zone.

[0068] In some alternative embodiments, argon blowing is used to protect the casting during the continuous casting step.

[0069] In the continuous casting process of this application embodiment, argon blowing is used to protect the casting, which can effectively prevent secondary oxidation of molten steel and nodule formation at the sprue, and also facilitates the floating of inclusions.

[0070] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are for illustrative purposes only, as 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 embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0071] It should be noted that in Examples 1-2 and Comparative Examples 1-3 below, the steel coils were compared with process parameters and performance based on products with a strip thickness of 5.0 mm and a coil weight of 12 tons.

[0072] Example 1 A method for water quenching of high-manganese austenitic wear-resistant steel coils includes: The molten steel is provided with the following composition, based on the total mass of the molten steel: C: 0.9%, Mn: 10%, Si: 0.35%, P: 0.045%, S: 0.02%, Al: 0.03%, with the remainder being iron and unavoidable impurities.

[0073] Continuous casting: In the continuous casting process, the superheat of the molten steel is 16℃, the casting speed is 0.8m / s, the temperature of the cooling water in the crystallizer is 5℃, and the ratio of the wide-face cooling water flow rate to the narrow-face cooling water flow rate in the crystallizer is 0.75 times the ratio of the wide-face dimension to the narrow-face dimension of the cast slab. The secondary cooling zone uses ultra-weak cooling, and the specific flow rate of the cooling water in the secondary cooling zone is 0.32L / Kg steel. The temperature of the slab in the straightening zone is 880℃. An electromagnetic stirrer is used to agitate the secondary cooling zone during the continuous casting process. Argon blowing is used for protection during continuous casting to obtain the slab.

[0074] The billet is heated and hot-rolled, including rough rolling and finish rolling. The steel obtained from finish rolling is coiled to obtain high-manganese austenitic wear-resistant steel coils.

[0075] High-manganese austenitic wear-resistant steel coils exhibiting coarse columnar crystal structures were selected for subsequent processing. The metallographic structure of the steel coils before water quenching was as follows: Figure 2 As shown, carbides and microstructures are distributed alternately in the metallographic structure, indicating that carbides are significantly precipitated in the high-manganese austenitic wear-resistant steel coil.

[0076] The high-manganese austenitic wear-resistant steel coil was heated from 25℃ to 50℃ at a rate of 2.5℃ / min; from 50℃ to 300℃ at a rate of 83℃ / h; from 300℃ to 700℃ at a rate of 83.33℃ / h; and from 700℃ to 1055℃ at a rate of 59.2℃ / h. It was then held at 1055℃ for 3 hours to obtain a pretreated high-manganese austenitic wear-resistant steel coil. This pretreated coil was then subjected to water toughening treatment. The coil was rapidly transported to a water tank for water toughening, causing the temperature to drop from 1055℃ to 200℃ at a cooling rate of 30℃ / min. The high-manganese austenitic wear-resistant steel coil obtained after water toughening treatment has the following metallographic structure: Figure 3 As shown, the metallographic structure is uniformly distributed with virtually no carbide precipitation.

[0077] Example 2 Example 2 provides a method for water-toughening high-manganese austenitic wear-resistant steel coils. The difference between Example 2 and Example 1 is that the cooling rate during the water-toughening process, where the temperature of the pretreated high-manganese austenitic wear-resistant steel coil is reduced from 1055℃ to 200℃, is 68℃ / min. The metallographic structures of the high-manganese austenitic wear-resistant steel coil in Example 2 before and after water-toughening are essentially the same, with a uniform distribution and virtually no carbide precipitation. This indicates that the process parameters of Example 2 can effectively improve the problem of carbide precipitation at grain boundaries affecting the toughness and plasticity of the steel.

[0078] Comparative Example 1 Comparative Example 1 provides a method for water toughening treatment of high-manganese austenitic wear-resistant steel coils. The difference between this method and Example 1 is that, except for not water toughening treatment of the high-manganese austenitic wear-resistant steel coils with coarse columnar crystal structures that appear during the production process and directly testing their performance, the rest of the preparation method is the same as that of Example 1.

[0079] Comparative Example 2 Comparative Example 2 provides a method for water toughening of high-manganese austenitic wear-resistant steel coils. The difference between this method and Example 1 is that, except for the use of a single heating curve during the heat treatment process, i.e., a constant heating rate of 60℃ / h is used to heat the steel coil from 25℃ to 1055℃, the rest of the preparation method is the same as in Example 1.

[0080] Comparative Example 3 Comparative Example 3 provides a method for water toughening of high-manganese austenitic wear-resistant steel coils, which differs from Example 1 in that the preliminary heating steps for the high-manganese austenitic wear-resistant steel coils are the same as in Example 1, but the cooling rate of the water toughening treatment is 25°C / min. The remaining preparation methods are the same as in Example 1.

[0081] The test results of the high-manganese austenitic wear-resistant steel coils prepared in Examples 1-2 and Comparative Examples 1-3 are shown in Table 1.

[0082] Table 1 The test results of the high-manganese austenitic wear-resistant steel coils in Examples 1-2 and Comparative Examples 1-3 show that the high-manganese austenitic wear-resistant steel coils prepared by the water-toughening treatment method provided in this application have excellent mechanical properties. Their yield strength, tensile strength, and elongation are all superior to those prepared by the methods in Comparative Examples 1-3, significantly improving the plasticity and toughness of the steel coils. The Brinell hardness and impact energy at -40°C are also superior to those of the comparative examples, indicating that the treatment method provided in this application can further improve the hardness and low-temperature toughness of the high-manganese austenitic wear-resistant steel coils.

[0083] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for water toughening treatment of high-manganese austenitic wear-resistant steel coils, characterized in that, include: The steel obtained from precision rolling is coiled to obtain high-manganese austenitic wear-resistant steel coils. The high-manganese austenitic wear-resistant steel coil is heated to a first temperature and held at the first temperature for 2.5h-3.5h to obtain a pretreated high-manganese austenitic wear-resistant steel coil. The first temperature ranges from 1050℃ to 1550℃. The pretreated high-manganese austenitic wear-resistant steel coil is subjected to water toughening treatment, which reduces the temperature of the pretreated high-manganese austenitic wear-resistant steel coil from a first temperature to a second temperature. The cooling rate of the water toughening treatment is 28℃ / min-70℃ / min, and the value of the second temperature is ≤200℃, thereby obtaining the water-toughened high-manganese austenitic wear-resistant steel coil.

2. The method according to claim 1, characterized in that, The heating process includes a first heating stage, a second heating stage, a third heating stage, and a fourth heating stage; The first heating stage includes heating the steel coil from 0℃-25℃ to 45℃-55℃, the second heating stage includes heating the steel coil from 45℃-55℃ to 290℃-310℃, the third heating stage includes heating the steel coil from 290℃-310℃ to 690℃-710℃, and the fourth heating stage includes heating the steel coil from 690℃-710℃ to the first temperature.

3. The method according to claim 2, characterized in that, The heating rate of the second heating stage is 75℃ / h to 85℃ / h, the heating rate of the third heating stage is 90℃ / h to 110℃ / h, and the heating rate of the fourth heating stage is 55℃ / h to 65℃ / h. Optionally, the high-manganese austenitic wear-resistant steel coil is heat-treated using a gas-fired furnace.

4. The method of claim 1, wherein, In the step of heating the high-manganese austenitic wear-resistant steel coil to a first temperature, the high-manganese austenitic wear-resistant steel coil, based on a total mass of 100%, comprises the following chemical composition: C: 0.9%-1.2%, Mn: 10%-14%, Si: 0.3%-0.6%, 0≤P≤0.05%, 0≤S≤0.02%, Al: 0.02%-0.1%, with the remainder being iron and unavoidable impurities.

5. The method of claim 1, wherein, The method further includes: continuous casting, billet heating, and hot rolling treatment prior to the finishing rolling.

6. The method according to claim 5, characterized in that, In the continuous casting process, the superheat of the molten steel is 15℃-50℃.

7. The method of claim 5, wherein, In the continuous casting process, the casting speed of the billet is 0.6 m / s to 1.3 m / s.

8. The method of claim 5, wherein, The temperature of the cooling water in the crystallizer during the continuous casting process is 4℃-8℃. In the continuous casting process, the ratio of the wide-face cooling water flow rate to the narrow-face cooling water flow rate of the crystallizer is 0.7 to 0.9 times the ratio of the wide-face dimension to the narrow-face dimension of the cast slab.

9. The method of claim 5, wherein, The secondary cooling zone is stirred during the continuous casting process; Optionally, argon blowing is used as a protective method for continuous casting in the continuous casting process; Optionally, in the continuous casting process, the secondary cooling zone adopts ultra-weak cooling, and the specific water volume of the cooling water in the secondary cooling zone is 0.25L / Kg steel to 0.68L / Kg steel; Optionally, the temperature of the billet in the straightening zone is 850℃-950℃.

10. The method of claim 1, wherein, The pretreated high-manganese austenitic wear-resistant steel coil is subjected to water toughening treatment in a water tank.

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