High-strength and high-toughness breaking hammer cylinder body steel, and preparation method and application thereof

Abstract

The application discloses a high-strength and high-toughness breaking hammer cylinder body steel and a preparation method and application thereof. The chemical components of the high-strength and high-toughness breaking hammer cylinder body steel are controlled as follows in percentage by mass: 0.20%<=C<=0.25%, 0.17%<=Si<=0.37%, 0.90%<=Mn<=1.15%, P<=0.020%, S<=0.020%, 0.40%<=Cr<=0.70%, 0.30%<=Mo<=0.35%, 0.35%<=Ni<=0.75%, Cu<=0.020%, 0.002%<=Al<=0.045%, Ca<=0.0030%, and the balance is Fe and inevitable impurities. The application significantly improves the mechanical properties and low-temperature impact toughness of the cylinder body, effectively solves the problems of easy cracking and short service life of the breaking hammer in an extremely cold environment, thereby prolonging the service life of the equipment, reducing the maintenance cost, and improving the operation safety.

Description

Technical Field

[0001] This invention belongs to the field of high-strength and high-toughness hydraulic breaker cylinder body steel production technology, specifically relating to a high-strength and high-toughness hydraulic breaker cylinder body steel, a method for preparing the high-strength and high-toughness hydraulic breaker cylinder body steel, and its application. Background Technology

[0002] With the rapid development of my country's construction machinery industry, hydraulic breakers used in high-altitude and cold regions are facing prominent problems such as short service life, long production cycle and high cost, which puts forward higher requirements for the durability and safety of large hydraulic breakers.

[0003] In the existing technology, traditional hydraulic breaker cylinder materials (such as 20CrMoA, 35CrMoA, and 42CrMoA of Chinese National Standard 3077; SCM418 and SCM420 of Japanese JIS G4053; DIN 25CrMo4 of European Standard EN 10083-1; and ASTM4118 and ASTM 4140 of American Standard A29 / 29M, etc.) cannot meet the requirements for long service life under extremely cold conditions. The mechanical properties and low-temperature impact toughness of the cylinder are low, which easily leads to cracking and premature failure. Summary of the Invention

[0004] To address the aforementioned technical problems in the prior art, this invention provides a high-strength, high-toughness hydraulic breaker cylinder body steel, its preparation method, and its application.

[0005] In a first aspect of the invention, a high-strength, high-toughness hydraulic breaker cylinder body steel is provided, the chemical composition of which is controlled by mass percentage as follows: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.020%, S≤0.020%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.020%, 0.002%≤Al≤0.045%, Ca≤0.0030%, with the balance being Fe and unavoidable impurities.

[0006] Furthermore, the chemical composition of the aforementioned high-strength and high-toughness hydraulic breaker cylinder steel is controlled by mass percentage as follows: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.01%, S≤0.001%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.015%, 0.002%≤Al≤0.045%, Ca≤0.0030%, with the balance being Fe and unavoidable impurities.

[0007] Furthermore, the mechanical properties of the aforementioned high-strength, high-toughness hydraulic breaker cylinder body steel are: tensile strength Rm ≥ 1025 MPa, yield strength R... p0.2 ≥880MPa, elongation after fracture A≥16%, reduction of area Z≥62%, room temperature impact energy A KU2 ≥135J, -60℃ low temperature impact energy A KU2 ≥65J.

[0008] Furthermore, the mechanical properties of the aforementioned high-strength, high-toughness hydraulic breaker cylinder body steel are: tensile strength Rm ≥ 1025 MPa, yield strength R... p0.2 ≥880MPa, elongation after fracture A≥16.2%, reduction of area Z≥62%, room temperature impact energy A KU2 ≥135J, -60℃ low temperature impact energy A KU2 ≥65J.

[0009] In a second aspect of the present invention, the method for preparing high-strength, high-toughness hydraulic breaker cylinder body steel includes the following steps: (1) Electric furnace smelting: Smelting is carried out according to the smelting process requirements, controlling the mass percentage of C and P in the final composition of the electric furnace, and controlling the tapping temperature of the electric furnace. (2) LF refining: Argon gas is blown and stirred throughout the LF refining process. Ferromanganese, ferrosilicon, ferrochrome, ferronickel and ferromolybdenum are added for alloying adjustment. The contents of Cr, Mo and Ni are controlled to the target range. The final temperature of LF is controlled to the target value before leaving the station. (3) VD vacuum refining: After the LF refining is completed, the ladle is transferred to the VD furnace for vacuum degassing. Argon gas is continuously blown and stirred during the vacuum process. After maintaining the vacuum for a predetermined time under the predetermined vacuum conditions, the vacuum is broken. The VD outlet temperature is controlled, and the mass percentage of each chemical component of the VD outlet molten steel is controlled. The remainder is Fe and unavoidable impurities. (4) Ingot casting: The molten steel refined by VD is ingot cast, the temperature of the molten steel is controlled during the ingot casting process, the amount of molten steel remaining is controlled, and the ingot moving time is controlled. (5) Forging: The steel ingots obtained by die casting are forged, and the forging heating temperature, holding time, initial forging temperature, final forging temperature and forging ratio are controlled. (6) Quenching and tempering heat treatment: After forging, the workpiece is subjected to quenching and tempering heat treatment. The quenching and tempering process of oil quenching + tempering is adopted to finally obtain high strength and high toughness hydraulic breaker cylinder steel.

[0010] Furthermore, in the above-mentioned method for preparing high-strength and high-toughness hydraulic breaker cylinder body steel: In step (1), the final composition of the electric furnace is controlled to be C≥0.05% and P≤0.010%, and the tapping temperature of the electric furnace is 1640℃~1680℃; In step (2), the Cr content is controlled at 0.40%~0.70%, the Mo content is controlled at 0.30%~0.35%, and the Ni content is controlled at 0.35%~0.75%. The product leaves the station when the LF final temperature reaches 1640℃~1680℃. In step (3), the vacuum is maintained at ≤67Pa for ≥15 minutes before being broken. The VD outlet temperature is controlled at 1566℃~1576℃. The chemical composition of the VD outlet molten steel by weight percentage is: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.020%, S≤0.020%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.020%, 0.002%≤Al≤0.045%, Ca≤0.0030%; In step (4), the temperature of molten steel in the ingot casting process is controlled at 1507℃~1555℃, the remaining molten steel is ≥2.0t, and the ingot moving time is controlled at ≥150min; In step (5), the forging heating temperature is controlled at 1180℃~1220℃, the holding time is 3.0h~4.0h, the initial forging temperature is 1080℃~1130℃, the final forging temperature is ≥850℃, and the forging ratio is controlled at ≥6. In step (6), the tempering process of "oil quenching at 850℃~870℃ → tempering at 450℃~470℃" is adopted.

[0011] Furthermore, in the above-mentioned method for preparing high-strength and high-toughness hydraulic breaker cylinder body steel: In step (1), the final composition of the electric furnace is controlled to be 0.07%≤C≤0.09% and P≤0.008%, and the tapping temperature of the electric furnace is 1650℃~1680℃; After maintaining the vacuum for 16-18 minutes in step (3), the chemical composition of the molten steel leaving the VD station, by weight percentage, is as follows: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.01%, S≤0.001%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.015%, 0.002%≤Al≤0.045%, Ca≤0.0030%; In step (4), the temperature of molten steel in the ingot casting process is controlled at 1540℃~1555℃, the remaining molten steel is ≥2.4t, and the ingot moving time is controlled at 170min~180min; In step (5), the forging heating temperature is controlled at 1180℃~1220℃, the holding time is 3.0h~4.0h, the initial forging temperature is 1085℃~1130℃, the final forging temperature is 850℃~870℃, and the forging ratio is controlled at 6.5~8.0.

[0012] In a third aspect of the invention, the application of the above-mentioned high-strength and high-toughness hydraulic breaker cylinder body steel in hydraulic breaker cylinder bodies for extremely cold environments is also provided.

[0013] The high-strength and high-toughness hydraulic breaker cylinder body steel of the present invention, its preparation method, and its application have the following advantages and beneficial effects: This invention significantly improves the mechanical properties and low-temperature impact toughness of the cylinder, effectively solving the problems of easy cracking and short lifespan of hydraulic breakers in extremely cold environments, thereby extending the service life of the equipment, reducing maintenance costs and improving operational safety. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0015] In a first aspect, a high-strength and high-toughness hydraulic breaker cylinder body steel is provided, which effectively solves the problem of short service life caused by easy cracking of hydraulic breakers in extremely cold environments.

[0016] Specifically, the chemical composition of the high-strength and high-toughness hydraulic breaker cylinder steel of the present invention is controlled by mass percentage as follows: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.020%, S≤0.020%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.020%, 0.002%≤Al≤0.045%, Ca≤0.0030%, with the balance being Fe and unavoidable impurities.

[0017] Preferably, the chemical composition of the high-strength and high-toughness hydraulic breaker cylinder steel of the present invention is controlled by mass percentage as follows: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.01%, S≤0.001%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.015%, 0.002%≤Al≤0.045%, Ca≤0.0030%, with the balance being Fe and unavoidable impurities.

[0018] Furthermore, the mechanical properties of the high-strength, high-toughness hydraulic breaker cylinder body steel of the present invention are: tensile strength Rm ≥ 1025 MPa, yield strength R p0.2 ≥880MPa, elongation after fracture A≥16%, reduction of area Z≥62%, room temperature impact energy A KU2 ≥135J, -60℃ low temperature impact energy A KU2 ≥65J.

[0019] Preferably, the mechanical properties of the high-strength and high-toughness hydraulic breaker cylinder body steel of the present invention are: tensile strength Rm ≥ 1025 MPa, yield strength R p0.2 ≥880MPa, elongation after fracture A≥16.2%, reduction of area Z≥62%, room temperature impact energy A KU2 ≥135J, -60℃ low temperature impact energy A KU2 ≥65J.

[0020] The function of the required elemental and content control ranges for the high-strength, high-toughness hydraulic breaker cylinder body steel of this invention is described below: C: 0.20%~0.25%. Carbon is the core strengthening element in steel, significantly improving its strength, hardness, and wear resistance through solid solution strengthening and carbide precipitation. This invention adopts a low-carbon design, which ensures the basic strength required for the hydraulic breaker cylinder body while avoiding a sharp decrease in the steel's toughness (especially low-temperature toughness) due to excessive carbon content. At the same time, it improves the steel's machinability and weldability.

[0021] Si: 0.17%~0.37%. Silicon is the main deoxidizer in the steelmaking process and also has a certain solid solution strengthening effect, which can improve the strength and elastic limit of steel. This invention controls the content within this range to ensure sufficient deoxidation to improve the purity of molten steel, while avoiding excessive silicon content that would reduce the plasticity and toughness of the steel, and preventing an increase in the temper brittleness tendency of the steel.

[0022] Mn: 0.90%~1.15%. Manganese is an excellent deoxidizer and desulfurizer, which can eliminate or reduce the hot brittleness caused by sulfur, significantly improve the hot working properties of steel, and greatly improve the hardenability of steel. It further enhances the strength of steel through solid solution strengthening. This invention controls the content within this range to ensure the overall hardenability of the large-section hydraulic breaker cylinder workpiece, while avoiding excessive manganese content that could lead to coarse grains, and preventing an increase in the steel's temper brittleness sensitivity.

[0023] P: ≤0.020%. Phosphorus is a harmful impurity element in steel, which can segregate at grain boundaries, significantly reducing the toughness of steel, especially its low-temperature toughness, and increasing its cold brittleness. This invention strictly controls the phosphorus content, ensuring that the steel still has good impact toughness in extremely cold environments of -60℃, while avoiding early fracture caused by grain boundary embrittlement.

[0024] S: ≤0.020%. Sulfur is a harmful impurity element in steel, which easily forms long strip-shaped manganese sulfide inclusions, disrupting the continuity of the steel matrix and significantly reducing the steel's plasticity, toughness, and fatigue resistance, while also deteriorating the steel's transverse mechanical properties. This invention strictly controls the sulfur content, which can not only greatly reduce the disruptive effect of harmful inclusions on the matrix, but also improve the anisotropy of the steel.

[0025] Cr: 0.40%~0.70%. Chromium can significantly improve the hardenability and tempering stability of steel, and at the same time, it can form stable alloy carbides, improving the strength, hardness and wear resistance of steel. This invention controls the content within this range, which can ensure the hardenability and strength requirements of the hydraulic breaker cylinder body, while avoiding the reduction of steel toughness due to excessive chromium content, and at the same time controlling the production cost within a reasonable range.

[0026] Mo (0.30%~0.35%) significantly improves the hardenability and tempering stability of steel, effectively suppresses high-temperature tempering brittleness, and refines grains, allowing the steel to maintain high strength and toughness after tempering. This invention controls the content within this range, effectively improving the strength-toughness balance of the steel while avoiding a significant increase in production costs due to excessive molybdenum content, and simultaneously ensuring the tempering stability of the steel.

[0027] Ni: 0.35%~0.75%. Nickel is one of the most effective alloying elements for improving the low-temperature toughness of steel. It can significantly reduce the ductile-brittle transition temperature of steel, while also improving its hardenability and strength. This invention adds an appropriate amount of nickel to ensure that the steel retains sufficient impact toughness in extremely cold environments down to -60℃, while also meeting the strength requirements of the steel, and controlling production costs within an acceptable range.

[0028] Cu: ≤0.020% (preferably ≤0.015%). Copper is a harmful residual element in steel. When its content is too high, it will segregate at grain boundaries, causing hot brittleness during hot working and seriously affecting the forging and rolling properties of the steel. This invention strictly controls the copper content, which can effectively avoid the generation of defects such as hot working cracks, ensure the hot working quality of steel, and improve the yield.

[0029] Al: 0.002%~0.045%. Aluminum is a commonly used final deoxidizer in steel. It can also form fine, dispersed aluminum nitride particles with nitrogen, effectively pinning grain boundaries and refining austenite grains, significantly improving the toughness of steel, especially its low-temperature toughness. This invention controls the content within this range to ensure both deoxidation and grain refinement, while avoiding excessive aluminum content that would form large amounts of coarse alumina inclusions, thus preventing a reduction in the purity and properties of the steel.

[0030] Ca: ≤0.0030%. Calcium is an inclusion modification element in steel, capable of transforming elongated, angular manganese sulfide inclusions into spherical, dispersed calcium sulfide inclusions, thereby improving the anisotropy of steel and enhancing its plasticity, toughness, and fatigue resistance. This invention controls the content within this range to achieve a good inclusion modification effect while avoiding excessive calcium content that could lead to excessive calcium oxide inclusions, thus preventing any adverse effects on the steel's properties.

[0031] In a second aspect of the present invention, a method for preparing high-strength, high-toughness hydraulic breaker cylinder body steel is provided, comprising the following steps: (1) Electric furnace smelting: Smelting is carried out according to the smelting process requirements, controlling the mass percentage of C and P in the final composition of the electric furnace, and controlling the tapping temperature of the electric furnace. (2) LF refining: Argon gas is blown and stirred throughout the LF refining process. Ferromanganese, ferrosilicon, ferrochrome, ferronickel and ferromolybdenum are added for alloying adjustment. The contents of Cr, Mo and Ni are controlled to the target range. The final temperature of LF is controlled to the target value before leaving the station. (3) VD vacuum refining: After the LF refining is completed, the ladle is transferred to the VD furnace for vacuum degassing. Argon gas is continuously blown and stirred during the vacuum process. After maintaining the vacuum for a predetermined time under the predetermined vacuum conditions, the vacuum is broken. The VD outlet temperature is controlled, and the mass percentage of each chemical component of the VD outlet molten steel is controlled. The remainder is Fe and unavoidable impurities. (4) Ingot casting: The molten steel refined by VD is ingot cast, the temperature of the molten steel is controlled during the ingot casting process, the amount of molten steel remaining is controlled, and the ingot moving time is controlled. (5) Forging: The steel ingots obtained by die casting are forged, and the forging heating temperature, holding time, initial forging temperature, final forging temperature and forging ratio are controlled. (6) Quenching and tempering heat treatment: After forging, the workpiece is subjected to quenching and tempering heat treatment. The quenching and tempering process of oil quenching + tempering is adopted to finally obtain high strength and high toughness hydraulic breaker cylinder steel.

[0032] Preferably, in the method for preparing high-strength and high-toughness hydraulic breaker cylinder body steel of the present invention: In step (1), the final composition of the electric furnace is controlled to be C≥0.05% and P≤0.010%, and the tapping temperature of the electric furnace is 1640℃~1680℃; In step (2), the Cr content is controlled at 0.40%~0.70%, the Mo content is controlled at 0.30%~0.35%, and the Ni content is controlled at 0.35%~0.75%. The product leaves the station when the LF final temperature reaches 1640℃~1680℃. In step (3), the vacuum is maintained at ≤67Pa for ≥15 minutes before being broken. The VD outlet temperature is controlled at 1566℃~1576℃. The chemical composition of the VD outlet molten steel by weight percentage is: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.020%, S≤0.020%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.020%, 0.002%≤Al≤0.045%, Ca≤0.0030%; In step (4), the temperature of molten steel in the ingot casting process is controlled at 1507℃~1555℃, the remaining molten steel is ≥2.0t, and the ingot moving time is controlled at ≥150min; In step (5), the forging heating temperature is controlled at 1180℃~1220℃, the holding time is 3.0h~4.0h, the initial forging temperature is 1080℃~1130℃, the final forging temperature is ≥850℃, and the forging ratio is controlled at ≥6. In step (6), the tempering process of "oil quenching at 850℃~870℃ → tempering at 450℃~470℃" is adopted.

[0033] More preferably, in the method for preparing high-strength and high-toughness hydraulic breaker cylinder body steel of the present invention: In step (1), the final composition of the electric furnace is controlled to be 0.07%≤C≤0.09% and P≤0.008%, and the tapping temperature of the electric furnace is 1650℃~1680℃; After maintaining the vacuum for 16-18 minutes in step (3), the chemical composition of the molten steel leaving the VD station, by weight percentage, is as follows: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.01%, S≤0.001%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.015%, 0.002%≤Al≤0.045%, Ca≤0.0030%; In step (4), the temperature of molten steel in the ingot casting process is controlled at 1540℃~1555℃, the remaining molten steel is ≥2.4t, and the ingot moving time is controlled at 170min~180min; In step (5), the forging heating temperature is controlled at 1180℃~1220℃, the holding time is 3.0h~4.0h, the initial forging temperature is 1085℃~1130℃, the final forging temperature is 850℃~870℃, and the forging ratio is controlled at 6.5~8.0.

[0034] In a third aspect of the invention, the application of the above-mentioned high-strength and high-toughness hydraulic breaker cylinder body steel in hydraulic breaker cylinder bodies for extremely cold environments is provided. The high-strength and high-toughness hydraulic breaker cylinder body steel effectively solves the problem of short service life caused by easy cracking of hydraulic breakers in extremely cold environments.

[0035] The following detailed description of the high-strength and high-toughness hydraulic breaker cylinder body steel, its preparation method, and its application are illustrated in conjunction with specific embodiments.

[0036] Example 1 The chemical composition of the high-strength and high-toughness hydraulic breaker cylinder steel in Example 1 is as follows by mass percentage: 0.20, Si: 0.37, Mn: 1.15, P: 0.01, S: 0.001, Cr: 0.40, Ni: 0.75, Mo: 0.35, Cu: 0.011, Al: 0.002, Ca: 0.003, with the balance being Fe and unavoidable impurities.

[0037] The specific process of preparing the high-strength and high-toughness hydraulic breaker cylinder steel in Example 1 includes: (1) Electric furnace smelting: The raw materials are prepared according to the smelting process requirements. The mass percentages of C and P in the final composition of the electric furnace are controlled to be 0.08% and 0.007% respectively. The tapping temperature of the electric furnace is controlled to be 1650℃. Auxiliary materials such as lime (CaO) and synthetic slag are added at the tapping. Aluminum shot, ferromanganese and silicon manganese alloy are added with the steel flow. The tapping amount is 80.3 tons.

[0038] (2) LF refining: Argon gas is blown and stirred throughout the LF refining process. Ferromanganese, ferrosilicon, ferrochrome, ferronickel and ferromolybdenum are added for alloying adjustment. The contents of Cr, Mo and Ni are controlled to the target range. The mass percentage of chemical composition at the LF endpoint is (%): Cr: 0.40, Ni: 0.75, Mo: 0.35. The LF endpoint temperature is controlled to 1640℃ before leaving the station.

[0039] (3) VD vacuum refining: After the LF refining is completed, the ladle is transferred to the VD furnace for vacuum degassing. Argon gas is continuously blown and stirred during the vacuuming process. The vacuum is maintained at a high vacuum (≤67Pa) for 16 minutes before the vacuum is broken. The mass percentage of each chemical component of the VD molten steel is controlled as follows (%): C: 0.20, Si: 0.37, Mn: 1.15, P: 0.01, S: 0.001, Cr: 0.40, Ni: 0.75, Mo: 0.35, Cu: 0.011, Al: 0.002, Ca: 0.003, with the balance being Fe and unavoidable impurities. The VD outlet temperature is controlled at 1566℃.

[0040] (4) Ingot casting: The molten steel refined by VD is ingot cast. The temperature of the molten steel during the ingot casting process is controlled at 1540-1555℃, the amount of molten steel remaining is controlled at 2.8t, and the ingot moving time is controlled at 170min.

[0041] (5) Forging: The steel ingots obtained by die casting are forged. The forging heating temperature is controlled at 1180℃, the holding time is 4h, the initial forging temperature is 1085℃, the final forging temperature is 850℃, and the forging ratio is 6.5.

[0042] (6) Quenching and tempering heat treatment: After forging, the workpiece is subjected to quenching and tempering heat treatment using the process of "850℃ oil quenching + 450℃ tempering" to finally obtain high-strength and high-toughness hydraulic breaker cylinder steel.

[0043] Performance test results: Tensile strength Rm: 1028MPa, Yield strength R p0.2 880MPa, elongation after fracture (A): 16.2%, reduction of area (Z): 62%, impact energy at room temperature (A) KU2 ≥135J, impact energy at -60℃ (A) KU2 ≥65J.

[0044] Example 2 The chemical composition of the high-strength and high-toughness hydraulic breaker cylinder steel in Example 2, by mass percentage, is as follows: C: 0.23, Si: 0.29, Mn: 0.9, P: 0.01, S: 0.001, Cr: 0.56, Ni: 0.57, Mo: 0.30, Cu: 0.010, Al: 0.033, Ca: 0.0014, with the balance being Fe and unavoidable impurities.

[0045] The specific process of preparing the high-strength and high-toughness hydraulic breaker cylinder steel in Example 2 includes: (1) Electric furnace smelting: The raw materials are prepared according to the smelting process requirements. The mass percentages of C and P in the final composition of the electric furnace are controlled to be 0.07% and 0.008% respectively. The tapping temperature of the electric furnace is controlled to be 1660℃. Auxiliary materials such as lime (CaO) and synthetic slag are added at the tapping. Aluminum shot, ferromanganese and silicon manganese alloy are added with the steel flow. The tapping amount is 81.2 tons.

[0046] (2) LF refining: Argon gas is blown and stirred throughout the LF refining process. Ferromanganese, ferrosilicon, ferrochrome, ferronickel and ferromolybdenum are added for alloying adjustment. The contents of Cr, Mo and Ni are controlled to the target range. The mass percentage of chemical composition at the LF endpoint is (%): Cr: 0.56, Ni: 0.57, Mo: 0.30. The LF endpoint temperature is controlled to 1655℃ before leaving the station.

[0047] (3) VD vacuum refining: After the LF refining is completed, the ladle is transferred to the VD furnace for vacuum degassing. Argon gas is continuously blown and stirred during the vacuuming process. The vacuum is maintained at a high vacuum (≤67Pa) for 17 minutes before the vacuum is broken. The mass percentage of each chemical component of the VD molten steel is controlled as follows (%): C: 0.23, Si: 0.29, Mn: 0.9, P: 0.01, S: 0.001, Cr: 0.56, Ni: 0.57, Mo: 0.30, Cu: 0.010, Al: 0.033, Ca: 0.0014, with the balance being Fe and unavoidable impurities. The VD outlet temperature is controlled at 1571℃.

[0048] (4) Ingot casting: The molten steel refined by VD is ingot cast. The temperature of the molten steel during the ingot casting process is controlled at 1540-1555℃, the amount of molten steel remaining is controlled at 2.4t, and the ingot moving time is controlled at 170min.

[0049] (5) Forging: The steel ingots obtained by die casting are forged. The forging heating temperature is controlled at 1200℃, the holding time is 3.5h, the initial forging temperature is 1100℃, the final forging temperature is 860℃, and the forging ratio is 7.0.

[0050] (6) Quenching and tempering heat treatment: After forging, the workpiece is subjected to quenching and tempering heat treatment. The quenching and tempering process of "860℃ oil quenching + 460℃ tempering" is adopted to finally obtain high strength and high toughness hydraulic breaker cylinder steel.

[0051] Performance test results: Tensile strength Rm: 1030MPa, Yield strength R p0.2 910MPa, elongation after fracture (A): 17.1%, reduction of area (Z): 64%, impact energy at room temperature (A) KU2 ≥150J, impact energy at -60℃ (A) KU2 ≥80J.

[0052] Example 3 The chemical composition of the high-strength and high-toughness hydraulic breaker cylinder steel in Example 3, by mass percentage, is as follows: C: 0.25, Si: 0.17, Mn: 1.0, P: 0.01, S: 0.001, Cr: 0.70, Ni: 0.35, Mo: 0.30, Cu: 0.015, Al: 0.045, Ca: 0.0010, with the balance being Fe and unavoidable impurities.

[0053] The specific process of preparing the high-strength and high-toughness hydraulic breaker cylinder body steel in Example 3 includes: (1) Electric furnace smelting: The raw materials are prepared according to the smelting process requirements. The mass percentages of C and P in the final composition of the electric furnace are controlled to be 0.09% and 0.007% respectively. The tapping temperature of the electric furnace is controlled to be 1680℃. Auxiliary materials such as lime (CaO) and synthetic slag are added at the tapping. Aluminum shot, ferromanganese and silicon manganese alloy are added with the steel flow. The tapping amount is 79.8 tons.

[0054] (2) LF refining: Argon gas is blown and stirred throughout the LF refining process. Ferromanganese, ferrosilicon, ferrochrome, ferronickel and ferromolybdenum are added for alloying adjustment. The contents of Cr, Mo and Ni are controlled to the target range. The mass percentage of chemical composition at the LF endpoint is (%): Cr: 0.70, Ni: 0.35, Mo: 0.30. The LF endpoint temperature is controlled to 1680℃ before leaving the station.

[0055] (3) VD vacuum refining: After the LF refining is completed, the ladle is transferred to the VD furnace for vacuum degassing. Argon gas is continuously blown and stirred during the vacuuming process. The vacuum is maintained at a high vacuum (≤67Pa) for 18 minutes and then the vacuum is broken. The mass percentage of each chemical component of the VD molten steel is controlled as follows (%): C: 0.25, Si: 0.17, Mn: 1.0, P: 0.01, S: 0.001, Cr: 0.70, Ni: 0.35, Mo: 0.30, Cu: 0.015, Al: 0.045, Ca: 0.0010, with the balance being Fe and unavoidable impurities. The VD outlet temperature is controlled at 1576℃.

[0056] (4) Ingot casting: The molten steel refined by VD is ingot cast. The temperature of the molten steel during the ingot casting process is controlled at 1540-1555℃, the amount of molten steel remaining is controlled at 2.5t, and the ingot moving time is controlled at 180min.

[0057] (5) Forging: The steel ingots obtained by die casting are forged. The forging heating temperature is controlled at 1220℃, the holding time is 3.0h, the initial forging temperature is 1130℃, the final forging temperature is 870℃, and the forging ratio is 8.0.

[0058] (6) Quenching and tempering heat treatment: After forging, the workpiece is subjected to quenching and tempering heat treatment. The quenching and tempering process of "870℃ oil quenching + 470℃ tempering" is adopted to finally obtain high strength and high toughness hydraulic breaker cylinder steel.

[0059] Performance test results: Tensile strength Rm: 1025MPa, Yield strength R p0.2 900MPa, elongation after fracture A: 16.8%, reduction of area Z: 63%, impact energy at room temperature A KU2 ≥145J, impact energy at -60℃ (A) KU2 ≥75J.

[0060] In summary, this invention significantly improves the mechanical properties and low-temperature impact toughness of the cylinder, effectively solving the problems of easy cracking and short lifespan of hydraulic breakers in extremely cold environments, thereby extending the service life of the equipment, reducing maintenance costs, and improving operational safety.

[0061] In the description of this specification, the term "embodiment" means a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The illustrative expressions of the above terms in this specification do not necessarily refer to the same embodiment. Furthermore, those skilled in the art can combine or combine the different embodiments and features described in this specification without creating contradiction.

[0062] It should be noted that, unless otherwise specified, the terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, when a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum. Further, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Moreover, when multiple ranges are provided to describe features, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0063] It should also be noted that, in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A high-strength, high-toughness hydraulic breaker cylinder body steel, characterized in that, The chemical composition of the high-strength and high-toughness hydraulic breaker cylinder steel is controlled by mass percentage as follows: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.020%, S≤0.020%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.020%, 0.002%≤Al≤0.045%, Ca≤0.0030%, with the balance being Fe and unavoidable impurities.

2. The high-strength, high-toughness hydraulic breaker cylinder body steel according to claim 1, characterized in that, The chemical composition of the high-strength and high-toughness hydraulic breaker cylinder steel is controlled by mass percentage as follows: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.01%, S≤0.001%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.015%, 0.002%≤Al≤0.045%, Ca≤0.0030%, with the balance being Fe and unavoidable impurities.

3. The high-strength, high-toughness hydraulic breaker cylinder body steel according to claim 1, characterized in that, The mechanical properties of the high-strength and high-toughness hydraulic breaker cylinder steel are as follows: tensile strength Rm ≥ 1025 MPa, yield strength R... p0.2 ≥880MPa, elongation after fracture A≥16%, reduction of area Z≥62%, room temperature impact energy A KU2 ≥135J, -60℃ low temperature impact energy A KU2 ≥65J.

4. The high-strength, high-toughness hydraulic breaker cylinder body steel according to claim 3, characterized in that, The mechanical properties of the high-strength and high-toughness hydraulic breaker cylinder steel are as follows: tensile strength Rm ≥ 1025 MPa, yield strength R... p0.2 ≥880MPa, elongation after fracture A≥16.2%, reduction of area Z≥62%, room temperature impact energy A KU2 ≥135J, -60℃ low temperature impact energy A KU2 ≥65J.

5. A method for preparing the high-strength, high-toughness hydraulic breaker cylinder body steel according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Electric furnace smelting: Smelting is carried out according to the smelting process requirements, controlling the mass percentage of C and P in the final composition of the electric furnace, and controlling the tapping temperature of the electric furnace. (2) LF refining: Argon gas is blown and stirred throughout the LF refining process. Ferromanganese, ferrosilicon, ferrochrome, ferronickel and ferromolybdenum are added for alloying adjustment. The contents of Cr, Mo and Ni are controlled to the target range. The final temperature of LF is controlled to the target value before leaving the station. (3) VD vacuum refining: After the LF refining is completed, the ladle is transferred to the VD furnace for vacuum degassing. Argon gas is continuously blown and stirred during the vacuum process. After maintaining the vacuum for a predetermined time under the predetermined vacuum conditions, the vacuum is broken. The VD outlet temperature is controlled, and the mass percentage of each chemical component of the VD outlet molten steel is controlled. The remainder is Fe and unavoidable impurities. (4) Ingot casting: The molten steel refined by VD is ingot cast, the temperature of the molten steel is controlled during the ingot casting process, the amount of molten steel remaining is controlled, and the ingot moving time is controlled. (5) Forging: The steel ingots obtained by die casting are forged, and the forging heating temperature, holding time, initial forging temperature, final forging temperature and forging ratio are controlled. (6) Quenching and tempering heat treatment: After forging, the workpiece is subjected to quenching and tempering heat treatment. The quenching and tempering process of oil quenching + tempering is adopted to finally obtain high strength and high toughness hydraulic breaker cylinder steel.

6. The method for preparing high-strength and high-toughness hydraulic breaker cylinder body steel according to claim 5, characterized in that, In step (1), the final composition of the electric furnace is controlled to be C≥0.05% and P≤0.010%, and the tapping temperature of the electric furnace is 1640℃~1680℃; In step (2), the Cr content is controlled at 0.40%~0.70%, the Mo content is controlled at 0.30%~0.35%, and the Ni content is controlled at 0.35%~0.75%. The product leaves the station when the LF final temperature reaches 1640℃~1680℃. In step (3), the vacuum is maintained at ≤67Pa for ≥15 minutes before being broken. The VD outlet temperature is controlled at 1566℃~1576℃. The chemical composition of the VD outlet molten steel by weight percentage is: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.020%, S≤0.020%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.020%, 0.002%≤Al≤0.045%, Ca≤0.0030%; In step (4), the temperature of molten steel in the ingot casting process is controlled at 1507℃~1555℃, the remaining molten steel is ≥2.0t, and the ingot moving time is controlled at ≥150min; In step (5), the forging heating temperature is controlled at 1180℃~1220℃, the holding time is 3.0h~4.0h, the initial forging temperature is 1080℃~1130℃, the final forging temperature is ≥850℃, and the forging ratio is controlled at ≥6. In step (6), the tempering process of "oil quenching at 850℃~870℃ → tempering at 450℃~470℃" is adopted.

7. The method for preparing high-strength, high-toughness hydraulic breaker cylinder body steel according to claim 6, characterized in that, In step (1), the final composition of the electric furnace is controlled to be 0.07%≤C≤0.09% and P≤0.008%, and the tapping temperature of the electric furnace is 1650℃~1680℃; After maintaining the vacuum for 16-18 minutes in step (3), the chemical composition of the molten steel leaving the VD station, by weight percentage, is as follows: 0.20%≤C≤0.25%, 0.17%≤Si≤0.37%, 0.90%≤Mn≤1.15%, P≤0.01%, S≤0.001%, 0.40%≤Cr≤0.70%, 0.30%≤Mo≤0.35%, 0.35%≤Ni≤0.75%, Cu≤0.015%, 0.002%≤Al≤0.045%, Ca≤0.0030%; In step (4), the temperature of molten steel in the ingot casting process is controlled at 1540℃~1555℃, the remaining molten steel is ≥2.4t, and the ingot moving time is controlled at 170min~180min; In step (5), the forging heating temperature is controlled at 1180℃~1220℃, the holding time is 3.0h~4.0h, the initial forging temperature is 1085℃~1130℃, the final forging temperature is 850℃~870℃, and the forging ratio is controlled at 6.5~8.

0.

8. The application of the high-strength and high-toughness hydraulic breaker cylinder steel as described in claims 1-4 in the cylinder body of a hydraulic breaker for extremely cold environments.