A method for manufacturing a pre-hardening-free high manganese steel frog

Abstract

The application discloses a manufacturing method of pre-hardening-free high manganese steel frog, and relates to the technical field of turnout rail pieces. The application processes the austenitic high manganese steel frog, so that the specific regions of the nose rail and the corresponding wing rail are higher than the working surface by 50-80 mm, and the transition slope gradient is less than 60 degrees. The above-mentioned high regions are forged by adopting three-stage forging at 1180-1200 DEG C, the reduction of the first and second forging is controlled, and the forging is kept warm. The third forging makes the high regions flush with the working surface, and finally, water cooling is performed to obtain the pre-hardening-free high manganese steel frog. The application does not need pre-hardening treatment, improves the frog performance through structural design and forging process, forms a heterogeneous structure on the surface, significantly improves the initial strength of the frog under the premise of maintaining the plasticity and toughness of the frog, prolongs the service life, and is suitable for harsh service environments such as high-speed heavy-load railways, plateau railways and the like.

Description

Technical Field

[0001] This invention relates to the field of turnout rail components, and in particular to a method for manufacturing a pre-hardening high-manganese steel frog. Background Technology

[0002] The frog is a key component of the railway turnout system, a planar crossing device that allows wheels to cross from one rail to another. It is the component in the track system that experiences the harshest service conditions and the highest wear and tear. High-manganese steel, with its excellent impact resistance and work hardening properties, is the main steel grade used in the production of railway frogs. With the continuous development of high-speed and heavy-haul railways, high-manganese steel frogs often fail prematurely due to severe plastic deformation or large-scale spalling caused by structural or metallurgical quality problems. The manufacturing quality of the frog and the performance of the material itself are crucial factors for the stable and safe development of railway transportation towards high speed and heavy load.

[0003] In the traditional manufacturing process of high-manganese steel, frogs typically require pre-hardening treatment. However, this pre-hardening treatment impairs the mechanical properties of high-manganese steel, reducing its plasticity and toughness, making it prone to horizontal cracking and abnormal failure in heavy-haul railway frogs, shortening their service life, and threatening traffic safety. Forging high-manganese steel is an important way to improve its performance. However, austenitic high-carbon high-manganese steel has poor forging process performance and is difficult to machine. Furthermore, conventional forging still suffers from low hardness and strength, failing to address the problem of large plastic deformation in the initial stages of service. Chinese patent CN201210378468.5 discloses a method for preparing forged cast high-manganese steel. The chemical composition of the high-manganese steel is: C 0.7-1.5%, Mn 10-17%, Si 0.3-1.0%, P < 0.15%, S < 0.06%, with the remainder being Fe. Specifically, the forged high-manganese steel casting is placed in an electric furnace and held at 1150℃-1200℃, then quickly removed from the furnace for forging deformation. Finally, it is tempered and held at 250℃-350℃ to obtain forged cast high-manganese steel. This method allows for the integral forging of high-manganese steel, but the process is complex, difficult, and costly to implement. Currently, there is an urgent need for a manufacturing method that eliminates the need for pre-hardening treatment, simplifies the process, and significantly improves the strength and hardness of the working surface of high-manganese steel frogs, thereby enhancing their wear resistance, to meet the development needs of high-speed heavy-haul railways. Summary of the Invention

[0004] The purpose of this invention is to provide a method for manufacturing a pre-hardening-free high-manganese steel frog, thereby solving the problems existing in the prior art. This invention provides a method for manufacturing a pre-hardening-free high-manganese steel frog by rationally designing the forging process and billet structure of the high-manganese austenitic steel, and precisely controlling the deformation process during forging, significantly improving the initial strength, thereby enhancing its impact and wear resistance and extending the service life of the frog.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a method for manufacturing a pre-hardening high-manganese steel frog, comprising the following steps:

[0007] (1) Flip processing: The austenitic high manganese steel flip is processed so that the area of ​​the flip core rail section width of 10mm to 60mm and the corresponding side wing rail area are 50mm to 80mm higher than the flip working surface.

[0008] A smooth transition with a ramp is used from the tip of the frog to the 10mm width of the frog section and the corresponding wing rail area on both sides, with a ramp angle of less than 60°.

[0009] The area from 60mm to 70mm in cross-sectional width of the frog point rail and the corresponding wing rail area on both sides also adopts a smooth transition with a slope of less than 60°.

[0010] (2) Forging of the frog: At 1190℃, the frog core rail and the corresponding two side wing rails are forged in a three-stage forging process, which is 50mm to 80mm higher than the frog working surface, so that the overall working surface of the frog is at the same level. After the three-stage forging is completed, the frog is water-cooled to obtain the pre-hardening-free high manganese steel frog.

[0011] The three-stage forging process is as follows:

[0012] The initial forging reduction is controlled between 15mm and 25mm, and after forging, it is heat-preserved at 1180-1200℃.

[0013] The reduction during the second forging is controlled between 15mm and 25mm. After forging, the temperature is held at 1180-1200℃ and then naturally cooled to 900-1050℃.

[0014] The third forging process ensures that the area of ​​the center rail and the two side wing rails that is 50mm to 80mm higher than the working surface of the frog is level with the working surface of the frog.

[0015] As a further preferred embodiment of the present invention, after the first forging is completed, the heat treatment is performed for 5-30 minutes, more preferably 10-20 minutes; after the second forging is completed, the heat treatment is performed for 5-30 minutes, more preferably 10-20 minutes.

[0016] As a further preferred embodiment of the present invention, step (1) adopts a casting method to process the fork: the fork is cast using molten high-manganese steel that has been purified and refined to obtain an austenitic high-manganese steel fork, and the area of ​​the fork casting blank core rail section width of 10mm to 60mm and the corresponding side wing rail area are 50mm to 80mm higher than the fork working surface.

[0017] A smooth transition with a slope is adopted from the tip of the frog casting to the 10mm width of the frog section and the corresponding two side wing rail areas, with a slope of less than 60°.

[0018] The transition from the 60mm width of the core rail section to the 70mm width of the core rail section and the corresponding two side wing rail areas also adopts a smooth slope with a slope of less than 60°.

[0019] As a further preferred embodiment of the present invention, the purification smelting includes the following steps:

[0020] Argon gas is introduced into the molten steel that has undergone dephosphorization and desulfurization treatment to carry out deoxidation treatment, thereby achieving the clean smelting process.

[0021] As a further preferred embodiment of the present invention, the temperature of the molten steel during the refining process is 1450–1490°C.

[0022] As a further preferred embodiment of the present invention, the argon gas introduction time is 5 to 10 minutes and the argon gas pressure is 0.3 to 0.4 MPa.

[0023] As a further preferred embodiment of the present invention, deoxidation is performed by feeding silicon-aluminum-barium-calcium wire into the molten steel.

[0024] As a further preferred embodiment of the present invention, the three-stage forging is performed by die forging or semi-die forging.

[0025] As a further preferred embodiment of the present invention, the mass percentage content of C and Mn elements in the pre-hardening-free high-manganese steel frog must meet the following requirements:

[0026] 13×ω(C)+ω(Mn)≥17%;

[0027] In the formula:

[0028] ω(C): The mass percentage of carbon element in the pre-hardening-free high-manganese steel frog, in %;

[0029] ω(Mn): The mass percentage of Mn element in the pre-hardening-free high-manganese steel turnout, in %.

[0030] Under the above-mentioned content conditions, high-manganese steel turnouts can form stable austenite after heat treatment.

[0031] As a further preferred embodiment of the present invention, the chemical composition of the pre-hardening-free high-manganese steel frog, by mass percentage, is: C: 0.50-0.90%, N: 0.10-0.30%, Mn: 12.0-20%, Cr: 4.0-9.0%, Si: 0-1.0%, P≤0.01%, S≤0.01%, with the balance being Fe.

[0032] As a further preferred embodiment of the present invention, the chemical composition of the pre-hardening-free high-manganese steel frog, by mass percentage, is: C: 0.6%, N: 0.2%, Mn: 18.0%, Cr: 6.4%, Si: 0.3%, P≤0.005%, S≤0.005%, with the balance being Fe.

[0033] The second technical solution of the present invention provides a pre-hardening-free high-manganese steel fork obtained by the above manufacturing method.

[0034] This invention provides an innovative method for manufacturing high-manganese steel frogs without pre-hardening, aiming to improve the mechanical properties of vulnerable areas in high-manganese steel frogs, particularly in terms of wear resistance, impact resistance, and extended service life. Compared with traditional pre-hardening methods, this invention can obtain high-manganese steel frogs with excellent performance without relying on complex pre-hardening processes.

[0035] The method of this invention is not limited to the chemical composition of high-manganese fork steel and the type of fork structure. Under reasonable forging process, it has a significant effect on forks with austenitic microstructure.

[0036] The present invention discloses the following technical effects:

[0037] (1) This invention does not rely on the traditional pre-hardening process, but directly improves the performance of high manganese steel turnouts through reasonable structural design and forging process, achieving the effect of no pre-hardening and simplifying the production process;

[0038] (2) Compared with other high manganese steel fork forging processes, this invention performs local forging and heat treatment on areas of the high manganese steel fork that are prone to fatigue damage, while other areas are not forged. This can significantly improve the service life of the high manganese steel fork and significantly reduce the cost.

[0039] (3) The microstructure of the fork prepared by the present invention is not limited to the traditional austenitic grain structure. It has a gradient microstructure in the depth direction. From the surface to the inside, it gradually transitions from an incomplete recrystallized microstructure to an equiaxed grain structure. Within the surface 5mm, a heterogeneous microstructure is obtained, consisting of a fully recrystallized fine grain structure and a long strip-shaped non-recrystallized microstructure with deformation strengthening effect. This microstructure has an excellent combination of strength and toughness, avoiding the problem of severe plastic deformation in the early stage of service of the unpre-hardened fork, and improving the service stability and safety of the fork. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments 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.

[0041] Figure 1 This is a schematic diagram of the structure of the fork before forging according to the present invention.

[0042] Figure 2 This is a schematic diagram of the forging process of the fork in this invention.

[0043] Figure 3 In the diagram, a is the IPF image of the pre-hardening-free high-manganese steel turnout prepared in Example 1 of the present invention within 5 mm of the working surface, and b is the KAM image.

[0044] Figure 4 In the diagram, a is the IPF image of the pre-hardening-free high-manganese steel turnout prepared in Example 1 of the present invention at a distance of 25 mm from the working surface, and b is the KAM image.

[0045] Figure 5 In the diagram, a is the IPF image of the pre-hardening-free high-manganese steel turnout prepared in Example 2 of the present invention within 5 mm of the working surface, and b is the KAM image.

[0046] Figure 6 In the diagram, a is the IPF image of the pre-hardening-free high-manganese steel turnout prepared in Example 2 of the present invention at a distance of 25 mm from the working surface, and b is the KAM image.

[0047] Figure 7 The metallographic image shows the high-manganese steel fork prepared in Comparative Example 1 of this invention within 5 mm of the working surface.

[0048] Figure 8 The metallographic image shows the high-manganese steel fork prepared in Comparative Example 2 of this invention within 5 mm of the working surface. Detailed Implementation

[0049] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0050] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0051] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0052] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0053] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0054] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0055] This invention provides a method for manufacturing a pre-hardening turnout, comprising the following steps:

[0056] (1) Clean smelting of high manganese steel

[0057] When smelting high-manganese steel using an electric arc furnace, scrap steel, high-carbon ferromanganese, and other raw materials are first added to the furnace. The carbon and alloy element content in the molten steel is controlled by adjusting the raw material ratio. Slag formation is carried out simultaneously during the smelting process to complete dephosphorization and desulfurization operations. When the temperature of the molten steel reaches 1440–1480℃, the steel is tapped and transferred to an LF ladle refining furnace for refining.

[0058] During the refining stage in the LF furnace, the temperature of the molten steel is maintained at 1450–1490℃. During refining, high-purity argon gas is first introduced from the bottom of the ladle for 5–10 minutes, with the argon pressure controlled at 0.3–0.4 MPa. During this period, silicon-aluminum-barium-calcium wire is fed into the ladle to remove oxygen from the molten steel through a deoxidation reaction. After deoxidation is completed, the molten steel is transferred to a pre-baked ladle for later use.

[0059] (2) Fork casting

[0060] Sand casting is employed to design the sand mold for a high-manganese steel frog billet with a unique shape for the frog rail and wing rails. The frog rail section, with a width of 10mm to 60mm and the corresponding wing rail sections on both sides, is 50mm to 80mm higher than the frog's working surface. A smooth, sloping transition is used from the frog rail tip to a 10mm section width and the corresponding wing rail sections on both sides, with a slope less than 60°. Similarly, a smooth, sloping transition is used from a 60mm to a 70mm section width of the frog rail and the corresponding wing rail sections on both sides, with a slope less than 60°. A structural schematic diagram is shown below. Figure 1 As shown.

[0061] (3) Fork forging

[0062] Before forging begins, the mold needs to be preheated to 500–600℃. The frog casting is then heated to 1190℃ and held for 2–3 hours before being removed. The raised area of ​​the frog is then forged using either die forging or semi-die forging. The lower die fits snugly with the bottom structure of the high-manganese steel frog, providing support. The internal structure of the upper die is similar to and matches the actual working surface, with a draft angle of 7–10°. A three-stage forging method is adopted. The first forging reduction is controlled between 15mm and 25mm, followed by a furnace holding period of 10-20 minutes to homogenize the microstructure and refine the grains. The second forging reduction is controlled between 15mm and 25mm, followed by a furnace holding period of 10-20 minutes to further refine the grains and obtain a more fully recrystallized microstructure. Natural cooling is then performed until the temperature reaches 900℃-1050℃. A third forging is then performed on the raised area, forging it until it is flush with the working surface of the fork, ensuring that the entire working surface of the fork is at the same level. Water cooling is then performed immediately after forging. A schematic diagram of the forging process is shown below. Figure 2 As shown. After forging, the turnout acquires a gradient microstructure in the depth direction, gradually transitioning from an incompletely recrystallized microstructure to an equiaxed grain microstructure from the surface to the interior. Within the surface 5mm, a heterogeneous microstructure is obtained, consisting of a fully recrystallized fine-grained microstructure and an elongated, non-recrystallized microstructure with deformation strengthening effect. This microstructure has an excellent combination of strength and toughness.

[0063] Example 1

[0064] The chemical composition of the turnout in this embodiment is as follows: C: 0.6 wt.%, N: 0.2 wt.%, Mn: 18.0 wt.%, Cr: 6.4 wt.%, Si: 0.3 wt.%, P≤0.005 wt.%, S≤0.005 wt.%, with the balance being Fe.

[0065] The preparation process of pre-hardening-free high-manganese steel frogs is as follows:

[0066] (1) Clean smelting of high-manganese steel: High-manganese steel is smelted using an electric arc furnace. First, industrial pure iron, scrap steel, high-carbon ferrochrome, and high-carbon ferromanganese are added to the electric arc furnace. The carbon and alloy element content in the molten steel is controlled by adjusting the raw material ratio. During the smelting process, slag formation is carried out simultaneously to complete dephosphorization and desulfurization operations. When the temperature of the molten steel reaches 1460℃, the steel is tapped and transferred to an LF furnace for refining.

[0067] The temperature of the molten steel in the LF ladle refining furnace is maintained at 1470℃. First, high-purity argon gas is introduced into the bottom of the ladle for 10 minutes at a pressure of 0.4 MPa. During this time, silicon-aluminum-barium-calcium wire is fed into the ladle for deoxidation. After wire feeding is complete, the molten steel is transferred to a pre-baked ladle.

[0068] (2) Flip casting: Sand casting is used to manufacture a flip with a specific shape: the area of ​​the flip core rail section width from 10mm to 60mm and the corresponding side wing rail areas are 80mm higher than the working surface of the flip; a smooth transition with a slope of 45° is adopted from the tip of the flip core rail to the 10mm section width of the core rail and the corresponding side wing rail areas; a smooth transition with a slope of 45° is also adopted from the 60mm section width of the flip core rail to the 70mm section width of the core rail and the corresponding side wing rail areas.

[0069] (3) Forging of the frog: Before forging, the mold needs to be preheated to 600℃. The frog billet is heated to 1190℃ and held for 2.5 hours before being removed and the heightened area of ​​the frog is forged. The forging method is die forging. The lower die fits with the bottom structure of the high manganese steel frog and provides support. The internal structure of the upper die is similar to the actual working surface, and the draft angle is 8°. The first forging of the 10mm wide section of the core rail and the corresponding wing rails on both sides is reduced by 20mm. After forging, it is reheated in the furnace for 15 minutes. The second forging of the 10mm wide section of the core rail and the corresponding wing rails on both sides is reduced by 20mm. After forging, it is reheated in the furnace for 15 minutes. The remaining height of the frog is 40mm. Then, it is naturally cooled. When it cools to 1000℃, the heightened area is forged for the third time, and the heightened area is forged to be level with the working surface of the fork, so that the entire working surface of the fork is at the same level. After forging, it is immediately water-cooled to obtain a pre-hardening high manganese steel fork.

[0070] Within 5 mm of the surface layer of the pre-hardening-free high-manganese steel turnout prepared in Example 1, there are fine-grained and elongated grain structures. Figure 3 (a)), and the KAM values ​​of the two regions differ significantly ( Figure 3(b) indicates that a heterogeneous granular structure consisting of recrystallized fine-grained structure and non-recrystallized elongated deformation-strengthening structure has formed in this region. The tensile properties and hardness of the working surface of the turnout within 5 mm and 25 mm were evaluated using an MTS hydraulic servo testing machine and a Vickers microhardness tester. The results are shown in Table 1. The turnout structure gradually transforms into an equiaxed granular structure towards the interior, reaching a completely equiaxed grain at a depth of 25 mm. Figure 4 (a)), in Figure 4 (b) has a generally low KAM value and a uniform microstructure. The properties are shown in Table 1.

[0071] Table 1

[0072]

[0073] Example 2

[0074] The chemical composition of the turnout in this embodiment is: C: 1.2 wt.%, Mn: 13.0 wt.%, Si: 0.3 wt.%, P≤0.005 wt.%, S≤0.005 wt.%, with the balance being Fe.

[0075] The manufacturing process of pre-hardening-free high-manganese steel frogs is as follows:

[0076] (1) Clean smelting of high manganese steel: High manganese steel is smelted using an electric arc furnace. First, industrial pure iron, scrap steel, and high-carbon ferromanganese are added to the electric arc furnace. The carbon and alloy element content in the molten steel is controlled by adjusting the raw material ratio. During the smelting process, slag is formed simultaneously to complete dephosphorization and desulfurization operations. When the temperature of the molten steel reaches 1460℃, the steel is tapped and transferred to an LF furnace for refining.

[0077] The temperature of the molten steel in the LF ladle refining furnace is maintained at 1470℃. First, high-purity argon gas is introduced into the bottom of the ladle for 10 minutes at a pressure of 0.4 MPa. During this time, silicon-aluminum-barium-calcium wire is fed into the ladle for deoxidation. After wire feeding is complete, the molten steel is transferred to a pre-baked ladle.

[0078] (2) Flip casting: Sand casting is used to manufacture a flip with a specific shape: the area of ​​the flip core rail section width from 10mm to 60mm and the corresponding side wing rail areas are 80mm higher than the working surface of the flip; a smooth transition with a slope of 45° is adopted from the tip of the flip core rail to the 10mm section width of the core rail and the corresponding side wing rail areas; the slope is less than 60°; a smooth transition with a slope of 45° is also adopted from the 60mm section width of the flip core rail to the 70mm section width of the core rail and the corresponding side wing rail areas.

[0079] (3) Forging of the frog: Before forging, the mold needs to be preheated to 600℃. The frog billet is heated to 1190℃ and held for 2.5 hours before being removed and the heightened area of ​​the frog is forged. The forging method is die forging. The lower die fits into the bottom structure of the high-manganese steel frog and provides support. The internal structure of the upper die is similar to the actual working surface and the draft angle is 7-10°. The first forging of the 10mm wide section of the core rail and the corresponding wing rails on both sides is reduced by 20mm. After forging, it is reheated in the furnace for 15 minutes. The second forging of the 10mm wide section of the core rail and the corresponding wing rails on both sides is reduced by 20mm. After forging, it is reheated in the furnace for 15 minutes. The remaining height of the frog is 40mm. Then, it is naturally cooled. When it cools to 950℃, the heightened area is forged for the third time, and the heightened area is forged to be level with the working surface of the fork, so that the entire working surface of the fork is at the same level. After forging, it is immediately water-cooled to obtain a pre-hardening high manganese steel fork.

[0080] Within 5 mm of the surface layer of the pre-hardening-free high-manganese steel turnout prepared in Example 2, there are fine-grained and elongated grain structures. Figure 5 (a)), and the KAM values ​​of the two regions differ significantly ( Figure 5 (b) indicates that a heterogeneous granular structure consisting of recrystallized fine-grained structure and non-recrystallized elongated deformation-strengthening structure has formed in this region. The tensile properties and hardness of the working surface of the turnout within 5 mm and 25 mm were evaluated using an MTS hydraulic servo testing machine and a Vickers microhardness tester. The results are shown in Table 1. The turnout structure gradually transforms into an equiaxed granular structure towards the interior, reaching a completely equiaxed grain at a depth of 25 mm. Figure 6 (a)), in Figure 6 (b) has a generally low KAM value and a uniform microstructure. The properties are shown in Table 2.

[0081] Table 2

[0082]

[0083] Comparative Example 1

[0084] The chemical composition of the comparative example turnout is as follows: C: 0.6 wt.%, N: 0.2 wt.%, Mn: 18.0 wt.%, Cr: 6.4 wt.%, Si: 0.3 wt.%, P≤0.005 wt.%, S≤0.005 wt.%, with the balance being Fe.

[0085] The preparation process of the fork is as follows:

[0086] (1) Clean smelting of high-manganese steel: High-manganese steel is smelted using an electric arc furnace. Scrap steel and high-carbon ferromanganese are added to the electric arc furnace to adjust the carbon and alloy element content in the molten steel. Slag formation during the smelting process completes dephosphorization and desulfurization operations. The molten steel is tapped at 1460℃ and transferred to an LF furnace for refining. The temperature of the molten steel in the LF ladle refining furnace is maintained at 1470℃. First, high-purity argon gas is introduced into the bottom of the ladle for 10 minutes at a pressure of 0.4 MPa. During this period, silicon-aluminum-barium-calcium wire is fed into the ladle for deoxidation. After wire feeding, the molten steel is transferred to a pre-baked ladle.

[0087] (2) Frog casting: Sand casting is used to manufacture frogs with a specific shape: the width of the frog casting blank core rail section is 10mm to 60mm and the corresponding side wing rail sections are 25mm higher than the frog working surface, and the slope is 45°.

[0088] (3) Forging of the frog: Before forging, the mold needs to be preheated to 600℃. The frog billet is heated to 1190℃ and held for 2.5 hours. The raised area of ​​the frog is then forged using die forging. The lower die fits into the bottom structure of the high-manganese steel frog and provides support. The internal structure of the upper die is similar to the actual working surface, and the draft angle is 7-10°. The raised area is forged until it is flush with the working surface of the frog. After forging, it is returned to the furnace and held for 15 minutes. It is then immediately water-cooled after forging.

[0089] The working surface of the high-manganese steel frog prepared in Comparative Example 1 consists of a fully recrystallized grain structure, and the microstructure at 5 mm is as follows: Figure 7 As shown, the structure is equiaxed. The tensile properties and hardness of the top 5 mm of the working surface of the turnout were evaluated using an MTS hydraulic servo testing machine and a Vickers microhardness tester. The results are shown in Table 3.

[0090] Table 3

[0091]

[0092] Comparative Example 2

[0093] The chemical composition of the comparative example turnout is as follows: C: 1.2 wt.%, Mn: 13.0 wt.%, Si: 0.3 wt.%, P ≤ 0.005 wt.%, S ≤ 0.005 wt.%, with the balance being Fe.

[0094] The process of preparing the fork is as follows:

[0095] (1) Clean smelting of high-manganese steel: Scrap steel, high-carbon ferromanganese, and other materials are added to the electric arc furnace to adjust the carbon and alloy element content in the molten steel. During the smelting process, slag formation completes dephosphorization and desulfurization operations. The molten steel is tapped at 1460℃ and transferred to the LF furnace for refining. The temperature of the molten steel in the LF ladle refining furnace is maintained at 1470℃. First, high-purity argon gas is introduced into the bottom of the ladle for 10 minutes at a pressure of 0.4 MPa. During this period, silicon-aluminum-barium-calcium wire is fed into the ladle for deoxidation. After the wire feeding is completed, the molten steel is transferred to a pre-baked ladle.

[0096] (2) Frog casting: Sand casting is used to manufacture frogs with a specific shape: the width of the frog casting blank core rail section is 10mm to 60mm and the corresponding side wing rail sections are 25mm higher than the frog working surface, and the slope is 45°.

[0097] (3) Forging of the frog: Before forging, the mold needs to be preheated to 600℃. The frog billet is heated to 1190℃ and held for 2.5 hours. The raised area of ​​the frog is then forged using die forging. The lower die fits into the bottom structure of the high-manganese steel frog and provides support. The internal structure of the upper die is similar to the actual working surface, and the draft angle is 7-10°. The raised area is forged until it is flush with the working surface of the frog. After forging, it is returned to the furnace and held for 15 minutes. It is then immediately water-cooled after forging.

[0098] The working surface of the high-manganese steel frog prepared in Comparative Example 2 consists of a fully recrystallized grain structure, and the microstructure at 5 mm is as follows: Figure 8 As shown, the structure is equiaxed. The tensile properties and hardness of the top 5 mm of the working surface of the turnout were evaluated using an MTS hydraulic servo testing machine and a Vickers microhardness tester. The results are shown in Table 4.

[0099] Table 4

[0100]

[0101] Comparative Example 3

[0102] The chemical composition of the comparative example turnout is as follows: C: 1.2 wt.%, Mn: 13.0 wt.%, Si: 0.3 wt.%, P ≤ 0.005 wt.%, S ≤ 0.005 wt.%, with the balance being Fe.

[0103] The process of preparing the fork is as follows:

[0104] (1) Clean smelting of high-manganese steel: Scrap steel, high-carbon ferromanganese, and other materials are added to the electric arc furnace to adjust the carbon and alloy element content in the molten steel. During the smelting process, slag formation completes dephosphorization and desulfurization operations. The molten steel is tapped at 1460℃ and transferred to the LF furnace for refining. The temperature of the molten steel in the LF ladle refining furnace is maintained at 1470℃. First, high-purity argon gas is introduced into the bottom of the ladle for 10 minutes at a pressure of 0.4 MPa. During this period, silicon-aluminum-barium-calcium wire is fed into the ladle for deoxidation. After the wire feeding is completed, the molten steel is transferred to a pre-baked ladle.

[0105] (2) Frog casting: Sand casting is used to manufacture a frog with a complete shape: the width of the frog casting blank core rail section from 10mm to 60mm and the corresponding side wing rail sections are 25mm higher than the frog working surface, and the slope is 45°.

[0106] (3) Forging of the frog: Before forging, the mold needs to be preheated to 600℃. The frog billet is heated to 1190℃ and held for 2.5 hours. The raised area of ​​the frog is then forged using die forging. The lower die fits into the bottom structure of the high-manganese steel frog and provides support. The internal structure of the upper die is similar to the actual working surface, and the draft angle is 7-10°. The raised area is forged until it is flush with the working surface of the frog. After forging, it is returned to the furnace and held for 15 minutes. It is then immediately water-cooled after forging.

[0107] (4) Frog Pre-hardening: The surface of the forged high-manganese steel frog is heated to 300℃, and then the working surface of the high-manganese steel frog is pre-hardened using a mechanical impact pre-hardening device. During the mechanical impact treatment, the pressure between the impact hammer and the working surface of the frog is 9MPa, the impact energy of the hammer is 80J, the impact frequency is 15Hz, the impact hardening treatment time for each treatment point is 20s, and the distance between each hardened edge is 4mm. The pre-hardened high-manganese steel frog is then allowed to cool naturally in the air.

[0108] The tensile properties and hardness of the working surface within 5 mm of the turnout were evaluated using an MTS hydraulic servo testing machine and a Vickers microhardness tester. The results are shown in Table 5.

[0109] Table 5

[0110]

[0111] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for manufacturing a pre-hardening-free high-manganese steel frog, characterized in that, Includes the following steps: (1) Frog processing: The austenitic high manganese steel frog is processed so that the frog core rail section width of 10mm to 60mm and the corresponding side wing rail section are 50mm to 80mm higher than the frog working surface. A smooth transition with a ramp is used from the tip of the frog to the 10mm width of the frog section and the corresponding wing rail area on both sides, with a ramp angle of less than 60°. The area from 60mm to 70mm in cross-sectional width of the frog point rail and the corresponding wing rail area on both sides also adopts a smooth transition with a slope of less than 60°. (2) Forging of the frog: In the range of 1180℃~1200℃, the frog center rail and the corresponding two side wing rails are forged in three stages to the area 50mm~80mm higher than the frog working surface, so that the overall working surface of the frog is at the same level; after the three stages of forging are completed, water cooling is performed to obtain the pre-hardening-free high manganese steel frog. The three-stage forging process is as follows: The initial forging reduction is controlled between 15mm and 25mm, and after forging, it is heat-preserved in the range of 1180℃ to 1200℃. The reduction during the second forging is controlled between 15mm and 25mm. After forging, the temperature is maintained at 1180℃ to 1200℃, and then naturally cooled to 900-1050℃. The third forging process ensures that the area of ​​the center rail and the two side wing rails that is 50mm to 80mm higher than the working surface of the frog is level with the working surface of the frog. After the first forging is completed, hold the temperature for 5-30 minutes; after the second forging is completed, hold the temperature for 5-30 minutes. The microstructure of the pre-hardening-free high-manganese steel frog is as follows: it is a gradient microstructure in the depth direction, gradually transitioning from an incomplete recrystallized microstructure to an equiaxed grain microstructure from the surface to the interior. Within the surface 5mm, a heterogeneous microstructure is obtained, consisting of a fully recrystallized fine-grained microstructure and an elongated non-recrystallized microstructure with deformation strengthening effect.

2. The manufacturing method according to claim 1, characterized in that, Step (1) The fork is processed by casting, including the following steps: the fork is cast using molten high manganese steel that has been cleaned and refined to obtain austenitic high manganese steel fork, and the width of the fork casting core rail section of 10mm to 60mm and the corresponding side wing rail sections are 50mm to 80mm higher than the working surface of the fork. A smooth transition with a slope is adopted from the tip of the frog casting to the 10mm width of the frog section and the corresponding two side wing rail areas, with a slope of less than 60°. The transition from the 60mm width of the core rail section to the 70mm width of the core rail section and the corresponding two side wing rail areas also adopts a smooth slope with a slope of less than 60°.

3. The manufacturing method according to claim 2, characterized in that, The clean smelting process includes the following steps: Argon gas is introduced into the molten steel that has undergone dephosphorization and desulfurization treatment to carry out deoxidation treatment, thereby achieving the clean smelting process.

4. The manufacturing method according to claim 3, characterized in that, The temperature of the molten steel during the refining process is 1450~1490℃.

5. The manufacturing method according to claim 3, characterized in that, Argon gas is introduced for 5-10 minutes at a pressure of 0.3-0.4 MPa.

6. The manufacturing method according to claim 1, characterized in that, The three-stage forging process employs either die forging or semi-die forging.

7. The manufacturing method according to claim 1, characterized in that, The mass percentage content of C and Mn elements in the pre-hardening-free high-manganese steel frog must meet the following requirements: 13×ω(C)+ω(Mn)≥17%; In the formula: ω(C): The mass percentage of carbon element in the pre-hardening-free high-manganese steel frog, in % (%). ω(Mn): The mass percentage of Mn element in the pre-hardening-free high-manganese steel turnout, in units of %.

8. A pre-hardening-free high-manganese steel forklift manufactured by the manufacturing method according to any one of claims 1-7.

Images