Manufacturing method of 60AT1-60kg / m forged alloy steel special-shaped steel rail and special-shaped steel rail

Abstract

The invention discloses a manufacturing method of a 60AT1-60kg / m forged alloy steel special-shaped steel rail and the special-shaped steel rail, the method comprises the following steps: heating: heating to 600-650 DEG C at a first heating speed, preserving heat for a first time, heating to 900-920 DEG C at a second heating speed, and preserving heat for a second time; cooling: cooling to 800 DEG C or below at a first air spraying pressure and a first cooling speed, cooling to 250-300 DEG C at a second air spraying pressure and a second cooling speed, and cooling to 200 DEG C or below at a third air spraying pressure and a third cooling speed; in the first stage, the temperature is increased to 200-240 DEG C, and heat preservation is conducted for third time; and in the second stage, the temperature is increased to 260-280 DEG C, heat preservation is conducted for the fourth time, and finally air cooling is conducted to the room temperature. The heat-affected softening area of the forged and pressed part of the heel end of the special-shaped rail is small in width, only 2-3 soft spots with the surface hardness lower than 380 HB are arranged, and the width is only about 30 mm.

Description

Technical Field

[0001] The invention relates to the technical field of forging special-shaped rails, and in particular to a manufacturing method for a 60AT1-60kg / m forged alloy steel special-shaped rail and the special-shaped rail. Background Art

[0002] With the frequency of railway transportation and the continuous growth of transportation volume, the requirements for the stability and efficiency of line operation are becoming higher and higher, which in turn puts higher requirements on the comprehensive mechanical properties of the rails used in the line. In order to meet the requirements of line operation and use, major domestic steel companies have successively developed high-strength and high-hardness bainitic alloy rails that can be used for the processing and manufacturing of turnouts, thereby further enhancing the wear resistance of line turnouts and extending their service life. Point rails are key components of turnouts, such as asymmetric point rails, heart rails, and special-shaped rails for connecting different rail types. Their heel ends are partially formed by high-temperature hot forging into standard rails that can be easily connected to the line. In this process, the comprehensive mechanical properties of the forged heel end are significantly reduced, and the width of the local heat-affected softening zone is large, especially for high-strength alloy steel. In order to restore the local comprehensive mechanical properties of the alloy steel heel end, the forged heel end needs to be re-heat treated. However, due to the difficulty of heat treatment process technology and the lack of reference standard technical requirements in the industry, the recovery and improvement of the comprehensive mechanical properties of the heel end has always plagued the manufacturing of products, which is mainly manifested in the lack of obvious improvement in the comprehensive mechanical properties, the wide control indicators of the softening zone, and the appearance of local low-collapse saddle-shaped wear, which is not conducive to the extension of the service life and improvement of the stability of the special-shaped rail.

[0003] At present, in order to restore the comprehensive mechanical properties of the heel end of alloy steel special-shaped rails, air cooling or tempering can be performed after forging. Patent CN104087852A discloses a high-strength bainitic rail and a production method thereof. The method utilizes the residual heat of rail rolling to accelerate the cooling of the rail head when it is cooled to 450-500°C, and then air cools it to room temperature when the temperature drops to 220-300°C, thereby obtaining a production method of a bainitic alloy rail with good wear resistance. However, the online heat treatment method adopted by the patent for heat treatment is relatively rough, and the detailed cooling parameters of each position of the rail are not specified. Moreover, how to restore the heel end after the hot die forging performance is lost and how to control the soft zone are not disclosed, and the manufacturing needs of the forged heel end of the special-shaped rail cannot be met. In addition, patent CN114015945A discloses a bainitic rail with a uniform hardness gradient and a production method thereof, which manufactures a bainitic rail with a uniform hardness gradient through smelting, casting, rolling, online heat treatment, processing and tempering heat treatment. The patent also does not disclose how to restore the heel end after the hot die forging performance is lost and how to control the soft zone, and cannot meet the manufacturing needs of the heel end of the special-shaped rail forging. Summary of the invention

[0004] The invention provides a manufacturing method of a 60AT1-60kg / m forged alloy steel special-shaped rail and the special-shaped rail, so as to solve the technical problem of how to restore the performance of the hot die forging performance loss of the rail heel end and control the soft zone.

[0005] According to one aspect of the present invention, there is provided a method for manufacturing a 60AT1-60kg / m forged alloy steel special-shaped rail, comprising the following steps:

[0006] (1) Heating: The forged special-shaped rail heel end is heated over the entire cross section, heated to 600-650°C at a first heating rate and then kept warm for a first time, then heated to 900-920°C at a second heating rate and then kept warm for a second time;

[0007] (2) Cooling: After the heating is completed, the forged special-shaped rail heel end is cooled to 600-800°C at a first air jet pressure and a first cooling rate, then cooled to 250-300°C at a second air jet pressure and a second cooling rate, and then cooled to 200-250°C at a third air jet pressure and a third cooling rate;

[0008] (3) Tempering: The forged special-shaped rail heel end is tempered after cooling. In the first stage, the temperature is raised to 200-240°C and kept at this temperature for the third time; in the second stage, the temperature is raised to 260-280°C and kept at this temperature for the fourth time, and finally air-cooled to room temperature.

[0009] Furthermore, in step (1), the temperature is increased from 300 to 600° C. to 600 to 650° C. at a first heating rate, wherein the first heating rate is greater than the second heating rate.

[0010] Furthermore, in step (1), the first heating rate is 2.5-3.5°C / s, and the second heating rate is 1.5-2.5°C / s.

[0011] Furthermore, in step (1), the first insulation time is 25 to 35 seconds, and the second insulation time is 15 to 25 seconds.

[0012] Furthermore, in step (1), the first insulation time is 30 seconds, and the second insulation time is 20 seconds.

[0013] Furthermore, in step (2), the first air jet pressure is 0.02-0.05 MPa, the second air jet pressure is 0.1-0.15 MPa, and the third air jet pressure is 0.05 MPa.

[0014] Furthermore, in step (2), the first cooling rate is 1-1.5°C / s, the second cooling rate is 1.5-2.5°C / s, and the third cooling rate is 1-1.2°C / s.

[0015] Furthermore, the third insulation time in step (3) is 60 to 90 minutes, and the fourth insulation time is 240 to 300 minutes.

[0016] Furthermore, in step (3), the first stage of tempering is heated to 200°C, and the second stage is heated to 280°C.

[0017] According to another aspect of the present invention, there is also provided a 60AT1-60kg / m forged alloy steel special-shaped rail, which is prepared by the manufacturing method of the 60AT1-60kg / m forged alloy steel special-shaped rail. The forged alloy steel special-shaped rail has a top surface hardness value less than HBW380, the number of soft spots is less than 3, the hardness of the soft zone is between 317 and 375HB, and the width is not more than 30mm.

[0018] The present invention has the following beneficial effects:

[0019] The present invention adopts the heat treatment technology of re-controlling full-section induction heating + rapid and continuous spraying of compressed air cooling + long-term low-temperature tempering to facilitate recovery after performance loss; during the heating process, the induction heating speed is fast and the heating temperature is high. At the same time, proper insulation after reaching the temperature can improve the uniformity of the temperature of each part of the local heating and the fineness of the organizational transformation, while increasing the temperature gradient per unit distance near the furnace mouth, reducing the furnace mouth temperature excessive buffer zone and the gap distance between the furnace mouth and the rail top, and weakening heat spillover. Continuous air jet cooling and low-temperature tempering in the cooling stage can further reduce the proportion and generation area of ​​austenite and ferrite softening microstructure phases, expand the bainite strong and tough microstructure transformation zone, and be beneficial to the soft zone control. The above method can better restore the performance lost in the forged special-shaped rail heel end, and the heat-affected softening zone can be reasonably controlled, so that the width of the heat-affected softening zone of the forged part of the special-shaped rail heel end after local heat treatment by the method of the present invention is small, there are only 2 to 3 soft spots below the surface hardness of 380HB, and the width is only about 30mm, which can meet the current standard requirements and reach the domestic leading control level (the domestic general control of soft spots below the surface hardness of 360HB is 3 to 5), and the line is not prone to local wear during use, which is conducive to extending the service life.

[0020] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0022] Figure 1 It is a schematic diagram of the heating and cooling equipment structure for the forging heel of the special-shaped rail;

[0023] Figure 2 It is a structural schematic diagram of the forged heel end of the special-shaped rail;

[0024] Figure 3 Schematic diagram of the surface hardness testing position of the forging heel end of the special-shaped rail.

[0025] In the figure: 1. Induction heating furnace; 2. Air jet cooling device; 3. Softening zone; 4. Forging heel of special-shaped rail; 5. Rail head; 6. Rail waist; 7. Rail bottom. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0027] The embodiment of the first aspect of the present invention provides a method for manufacturing a 60AT1-60kg / m forged alloy steel special-shaped rail, comprising the following steps:

[0028] (1) Heating: The forged special-shaped rail heel end is heated over the entire cross section by using a medium frequency induction furnace. The temperature is raised to 650°C at a first heating rate and then kept at this temperature for a first time. The temperature is then raised to 900-920°C at a second heating rate and then kept at this temperature for a second time. The rail is then immediately taken out of the furnace for air jet cooling.

[0029] (2) Cooling: After the heating is completed, the forged special-shaped rail heel end is cooled to 600-800°C at a first air jet pressure and a first cooling rate, then cooled to 250-300°C at a second air jet pressure and a second cooling rate, and then cooled to 200-250°C at a third air jet pressure and a third cooling rate;

[0030] (3) Tempering: The forged special-shaped rail heel end is tempered after cooling. In the first stage, the temperature is raised to 200-240°C and kept at this temperature for the third time; in the second stage, the temperature is raised to 260-280°C and kept at this temperature for the fourth time, and finally air-cooled to room temperature.

[0031] The present invention adopts the heat treatment technology of re-controlling full-section induction heating + rapid and continuous compressed air cooling + long-term low-temperature tempering to facilitate recovery after performance loss; in the heating process, the induction heating speed is fast and the heating temperature is high, and appropriate insulation after reaching the temperature can improve the uniformity of the temperature of each part of the local heating and the fineness of the organizational transformation, while increasing the temperature gradient per unit distance near the furnace mouth, reducing the furnace mouth temperature excessive buffer zone and the gap distance between the furnace mouth and the rail top, and reducing heat spillover. Continuous air spray cooling and low-temperature tempering in the cooling stage further reduce the proportion and generation area of ​​austenite and ferrite softening organizational phases, expand the bainite strong and tough organizational transformation zone, which can be beneficial to the control of the soft zone. Through the above method, the performance lost at the heel end of the forged special-shaped rail can be better restored, and the heat-affected softening zone can be reasonably controlled.

[0032] The present invention combines the process methods of rapid intermittent continuous cooling after forging + low-temperature long-time segmented tempering, and reduces the residual martensite, austenite and stress, and avoids the precipitation of unfavorable tissues by reasonably allocating and accurately controlling the cooling speed and time of different parts, so as to further improve the comprehensive mechanical properties such as strength and hardness of the heel end of the special-shaped rail, reduce the width of the local heat-affected softening zone, improve the quality of the heel end of the alloy steel special-shaped rail after forging, and extend the reliability and service life of the special-shaped rail.

[0033] In this embodiment, step (1) uses a medium frequency induction furnace to perform full-section induction heating on the heel end of the forged special-shaped rail, which can not only reduce the temperature stress during the heating process, but also reduce the temperature non-uniformity in the length and height directions of the special-shaped rail, ensuring that the temperature difference is no more than 50°C, and preparing for cooling. During the heating process, the heating speed is slightly faster at low temperatures and slightly slower at high temperatures, and the front and back are balanced. In addition, the step-by-step insulation at different temperatures is more conducive to the diffusion of heat and atomic internal vibration, reducing the temperature difference between different parts, and the thermal expansion and contraction of each part tend to be consistent, which is conducive to reducing temperature stress and reducing temperature non-uniformity.

[0034] In step (1), 600-650°C is taken as the dividing point, and the heating rate before the temperature rises to 600-650°C during the heating process is greater than the heating rate after 600-650°C. Preferably, in this embodiment, 650°C is taken as the dividing point, which has the effect of not producing phase change and reducing tissue stress. The principle is: phase change is the transformation of one tissue structure into another tissue structure. The volume, atomic structure arrangement and distribution of the two tissue structures are different, and different degrees of distortion will occur inside the metal lattice, resulting in different degrees of expansion, contraction and other physical property changes, thereby causing extrusion and expansion of the surrounding metal. These microscopic extrusion and expansion distortions gradually accumulate to a certain extent and evolve into a larger stress field, thereby affecting the deformation of the metal. The larger the stress field, the stronger the stress. If no phase change occurs, there will be no obvious tissue transformation, that is, no obvious increase in tissue stress. At the same time, 650°C can produce microscopic recovery and recrystallization, further reducing tissue stress.

[0035] In step (2), continuous compressed air spray cooling is adopted in stages, and different cooling air spray pressures are set in different areas of the forging of the heel end of the special-shaped rail. This can not only avoid the rapid cooling of the surface at high temperature to produce martensite and reduce thermal stress, but also generate bainite at medium and low temperatures to reduce tissue stress, stabilize austenite at low temperatures, and improve comprehensive mechanical properties. The working principle is as follows: at high temperature (the temperature after leaving the furnace is 900-920°C), the cooling rate is slightly lower, which can reduce the diffusion of local metal carbon elements and alloy elements to inhibit the rapid cooling of local metal to reach the martensitic phase transformation zone and produce more martensite, which will result in ultra-high strength and hardness and reduced toughness. Appropriate rapid cooling at medium and low temperatures (below 600-800°C) is to inhibit the further inhibition of the diffusion of carbon elements and alloy elements at high temperatures, which causes part of the austenite to decompose into soft phases such as pearlite. Further reducing the cooling rate at low temperature (250-300°C) can not only reduce temperature stress, but also reduce the possibility of continuous transformation of austenite to martensite by increasing the probability of element diffusion.

[0036] In step (3), low-temperature staged tempering is adopted. The end profiled rail section is placed in a heating furnace and heated to 200-240°C, kept warm for 60-90 minutes, and then heated to 260-280°C again, kept warm for 240-300 minutes, and then taken out of the furnace and air-cooled to room temperature. The main purpose of setting different low-temperature tempering temperatures and holding times is to increase the temperature step by step at different temperatures, which is more conducive to the recovery of microscopic defects of metal materials. A small amount of carbide precipitation further strengthens the matrix (if the temperature is higher (greater than 280-350°C), a large amount of carbide precipitation will occur, and the comprehensive mechanical properties, especially toughness and plasticity, will decrease), avoid temper brittleness, and the recovery temperature is more uniform and the recovery is more sufficient. After tempering, the comprehensive mechanical properties such as hardness, strength, plasticity, and toughness are further improved, which is more conducive to the material recovering to the high strength, wear resistance and high toughness of the original material.

[0037] In an embodiment of the present application, in step (1), the temperature is increased to 600-650°C at a first heating rate within 300-600°C, and the first heating rate is greater than the second heating rate. Preferably, in step (1), the first heating rate is 2.5-3.5°C / s, and the second heating rate is 1.5-2.5°C / s. Setting the heating rate within the above range can not only ensure a certain heating rate efficiency, but also appropriately relax the organization and thermal stress, inhibit the growth of the organization before the phase change, and prepare for the phase change.

[0038] In an embodiment of the present application, the first insulation time described in step (1) is 25 to 35 seconds, and the second insulation time is 20 to 30 seconds. Further preferably, the first insulation time described in step (1) is 30 seconds, and the second insulation time is 20 seconds. When the temperature is raised to 650°C and maintained for 30 seconds, the temperature is raised to 920°C, and maintained for 20 seconds before being taken out of the furnace for spray cooling, with a homogenizing temperature to prepare for the transformation of the organization. If the insulation time is lower than the above range, the uniform temperature effect is not obvious. If the insulation time is greater than the above range, the organization will gradually coarsen and the heat affected zone will gradually widen.

[0039] In an embodiment of the present application, in step (2), the first air jet pressure is 0.02-0.05Mpa, the second air jet pressure is 0.1-0.15Mpa, and the third air jet pressure is 0.05Mpa. In step (2), the first cooling rate is 1-1.5℃ / s, the second cooling rate is 1.5-2.5℃ / s, and the third cooling rate is 1-1.2℃ / s. The air jet pressure and cooling rate during the cooling process are set to the above values ​​to achieve a balance between the strength, hardness, toughness and other properties of the forged special-shaped rails. If it is higher than the above protection range, it is easy to cause mechanical properties such as hardness and strength to be too high, plastic toughness is low, and the comprehensive mechanical properties deteriorate; if it is lower than the above protection range, it is easy to cause equipment damage, mechanical properties such as hardness and strength are low, plastic toughness is high, and the comprehensive mechanical properties are also deteriorated.

[0040] In an embodiment of the present invention, the third insulation time in step (3) is 60 to 90 minutes, and the fourth insulation time is 240 to 300 minutes. The first stage of tempering in step (3) is heated to 200°C, and the second stage is heated to 280°C. Different low-temperature tempering temperatures and insulation times are set mainly to increase the temperature step by step at different temperatures, which is more conducive to the recovery of microscopic defects of metal materials.

[0041] In an embodiment of the present invention, the forged heel end of the profiled rail is placed in an induction heating furnace for heating. Figure 1 and Figure 2 As shown. One end of the forged heel end 4 of the special-shaped rail is transported by the mechanism into the furnace chamber of the induction heating furnace 1 for a certain distance and then stops. The power is turned on to start heating. After the temperature reaches the preset temperature and the insulation is completed, the mechanism exits the furnace chamber of the induction heating furnace 1 and stops. At this time, the air jet cooling device 2 located above the furnace mouth starts to spray compressed gas downward to fully cover and continuously cool the local heated part of the rail. After reaching the cooling temperature, the air jet stops and continues to cool to room temperature. Then, the heated and cooled end of the rail is put into the box-type resistance furnace for tempering treatment and then taken out of the furnace for air cooling. The softening zone 3 is located near the furnace mouth of the induction heating furnace 1. It is a hardness softening area formed by the local heating of the medium and high temperature induction heating furnace. The forged heel end of the special-shaped rail is provided with a rail head 5, a rail waist 6 and a rail bottom 7.

[0042] During the heating process, the heating rate is controlled within 600-650℃ to be no more than 2.5-3.5℃ / S to reduce stress. When the temperature reaches about 600-650℃, it is kept warm for about 30s and then immediately heated to 900-920℃. At this time, the heating rate is controlled at about 1.5-2.5℃ / s. After keeping warm for 20s, it is immediately taken out of the furnace for spray cooling to ensure sufficient organizational transformation and more uniform longitudinal and transverse temperatures, and to ensure that the temperature difference is no more than 50℃ to prepare for cooling. After heating, the special-shaped rail is withdrawn from the furnace, and the compressed air of the blower is turned on to cool the forged heel and end rail heads of the special-shaped rail. During the cooling process, different cooling air pressures are set in different areas of the forged heel and end rails of the special-shaped rails. The air pressure at the beginning of the forming section is about 0.02MPa, and the air pressure from the transition section to the heat-affected zone of the raw material is about 0.05MPa. The cooling rate is controlled at 1-1.5℃ / s to avoid the generation of a large amount of martensite on the surface and reduce the local thermal stress of the surface. When cooled to 600-800℃, the air pressure in the forming section is adjusted to about 0.1MPa, and the air pressure in the transition section to the heat-affected zone of the raw material is about 0.15M Pa, the cooling rate is controlled at 1.5-2.5℃ / s, which can quickly reduce the rail head temperature, refine the grains, and promote the rail to reach the bainite phase transformation temperature. It can effectively control the overall cooling of the rail, and it is easy to obtain good strength, hardness and reduce the width of the softening zone. When the residual temperature is lower than about 300℃, the overall air pressure is set to 0.05MPa before and after, and the cooling rate is controlled at 0.8-1.2℃ / s. When it is cooled to about 200℃, the air spray is stopped and air-cooled to room temperature. This process method can not only ensure that more bainite structures are generated at medium and low temperatures, but also obtain a small amount of martensite structures. After the cooling of the forged heel end of the special-shaped rail is completed to room temperature, it is then placed in a resistance furnace for staged low-temperature tempering. The temperature is raised to 200℃ in the tempering heating furnace, and the temperature is kept for 60-90min. The temperature is raised to 280℃ again, and the temperature is kept for 240-300min. The furnace is air-cooled to room temperature. This method can gradually eliminate residual stress in stages while controlling excessive precipitation of carbides and reducing material embrittlement.

[0043] According to another aspect of the present invention, there is also provided a 60AT1-60kg / m forged alloy steel special-shaped rail, which is prepared by the manufacturing method of the 60AT1-60kg / m forged alloy steel special-shaped rail. The forged alloy steel special-shaped rail has a top surface hardness value less than HBW380, the number of soft spots is less than 3, the hardness of the soft zone is between 317 and 375HB, and the width is not more than 30mm.

[0044] The longitudinal rail top surface hardness value of the alloy steel special-shaped rail head after forging is less than HBW380, the number of soft spots is about 2 to 3 (the measuring point spacing is 10mm), the hardness of the soft area is between 317 and 375HB, the width is not more than 30mm, the surface hardness excluding the soft area is between 407 and 468HB, the impact absorption energy is not less than 120J, the tensile strength is in the range of 1343 to 1477.5MPa, the elongation after fracture is between 12.5 and 14.3%, and the material performance after forging is effectively restored and improved.

[0045] The following examples describe the present disclosure in more detail, and these examples are intended for illustrative purposes only.

[0046] Example 1

[0047] This embodiment provides a method for manufacturing a 60AT1-60kg / m forged alloy steel special-shaped rail, comprising the following steps:

[0048] (1) Heating: The forged special-shaped rail heel end is heated over the entire cross section using a medium frequency induction furnace. The temperature is raised to 650°C at a rate of 2.5°C / s and then kept at that temperature for 30 seconds. The temperature is then raised to 900°C at a rate of 1.5°C / s and then kept at that temperature for 20 seconds. The rail is then immediately taken out of the furnace for air jet cooling.

[0049] (2) Cooling: After heating, the forged special-shaped rail heel end is cooled to 800°C at 0.02MPa and 1.0°C / s, then cooled to 280°C at 0.1MPa and 1.5°C / s, and then cooled to below 200°C at 0.05MPa and 1.1°C / s;

[0050] (3) Tempering: The forged special-shaped rail heel end is tempered after cooling. In the first stage, the temperature is raised to 200°C and kept at this temperature for 60 minutes. In the second stage, the temperature is raised to 280°C and kept at this temperature for 240 minutes. Finally, the rail is air-cooled to room temperature.

[0051] Example 2

[0052] This embodiment provides a method for manufacturing a 60AT1-60kg / m forged alloy steel special-shaped rail, comprising the following steps:

[0053] (1) Heating: The forged special-shaped rail heel end is heated over the entire cross section using a medium frequency induction furnace. The temperature is raised to 650°C at 3.1°C / s and then kept at this temperature for 30 seconds. The temperature is then raised to 900°C at 2.2°C / s and then kept at this temperature for 20 seconds. The rail is then immediately taken out of the furnace for air jet cooling.

[0054] (2) Cooling: After heating, the forged special-shaped rail heel end is cooled to 800°C at 0.03MPa and 1.2°C / s, then cooled to 300°C at 0.15MPa and 2.5°C / s, and then cooled to below 200°C at 0.05MPa and 1.0°C / s;

[0055] (3) Tempering: The forged special-shaped rail heel end is tempered after cooling. In the first stage, the temperature is raised to 200°C and kept at this temperature for 60 minutes. In the second stage, the temperature is raised to 280°C and kept at this temperature for 240 minutes. Finally, the rail is air-cooled to room temperature.

[0056] Example 3

[0057] This embodiment provides a method for manufacturing a 60AT1-60kg / m forged alloy steel special-shaped rail, comprising the following steps:

[0058] (1) Heating: The forged special-shaped rail heel end is heated over the entire cross section using a medium frequency induction furnace. The temperature is raised to 650°C at 3.5°C / s and then kept at this temperature for 30 seconds. The temperature is then raised to 900°C at 2.5°C / s and then kept at this temperature for 20 seconds. The rail is then immediately taken out of the furnace for air jet cooling.

[0059] (2) Cooling: After heating, the forged special-shaped rail heel end is cooled to 800°C at 0.05MPa and 1.5°C / s, then cooled to 250°C at 0.13MPa and 2.2°C / s, and then cooled to below 200°C at 0.05MPa and 1.2°C / s;

[0060] (3) Tempering: The forged special-shaped rail heel end is tempered after cooling. In the first stage, the temperature is raised to 200°C and kept at this temperature for 60 minutes. In the second stage, the temperature is raised to 280°C and kept at this temperature for 240 minutes. Finally, the rail is air-cooled to room temperature.

[0061] Comparative Example 1

[0062] This comparative example is basically the same as Example 1, except that:

[0063] During the heating process, the temperature is increased to 950°C at 3.8°C / s; during the cooling process, the temperature is reduced to 200-250°C at 3.6°C / s; during the tempering process, the temperature is first increased to 330°C and then increased to 360°C.

[0064] Comparative Example 2

[0065] This comparative example is basically the same as Example 1, except that:

[0066] During the heating process, the temperature is increased to 930°C at 2.4°C / s; during the cooling process, the temperature is reduced to 260-300°C at 3.3°C / s; during the tempering process, the temperature is first increased to 300°C and then increased to 330°C.

[0067] Comparative Example 3

[0068] This comparative example is basically the same as Example 1, except that:

[0069] During the heating process, the temperature is increased to 890°C at 2.8°C / s; during the cooling process, the temperature is reduced to 280-350°C at 3.8°C / s; during the tempering process, the temperature is first increased to 280°C and then increased to 300°C.

[0070] The control parameters in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1.

[0071] Table 1 shows the control parameters in Examples 1 to 3 and Comparative Examples 1 to 3.

[0072]

[0073] According to TB / T2344.3 "Rail Part 3: Special-shaped Rail" and GB228.1, GB230.1, GB231.1 standard technical requirements, the tensile strength of the forged part of the heel end of the special-shaped rail prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was tested for performance. The test results are shown in Table 2.

[0074] Table 2 Performance test results of the forging parts of the special-shaped rail heel end prepared in Examples 1 to 3 and Comparative Examples 1 to 3

[0075]

[0076]

[0077] By comparing Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that for the same type of special-shaped rails, under different heat treatment conditions, Examples 1 to 3 of the present invention will have a certain impact on the final performance of the special-shaped rails. After the alloy steel special-shaped rails are treated by this process, the hardness value of the longitudinal rail top surface of the rail head after the end forging is less than HBW380, and the number of soft points is about 2 to 3 (the distance between the measuring points is 10 mm, such as Figure 3 As shown in the figure, the hardness of the soft zone is between 317 and 375 HB, the width is not more than 30 mm, the surface hardness excluding the soft zone is between 407 and 468 HB, the impact absorption energy is not less than 120 J, the tensile strength is in the range of 1352 to 1477.5 MPa, the elongation after fracture is between 12.5 and 14.3%, the tensile strength and impact performance are sampled at the rail head position, the material properties are effectively restored and improved after forging, and the comprehensive mechanical properties are significantly improved.

[0078] Figure 3 The surface hardness detection method of the forged heel end of the special-shaped rail is as follows: after the top of one end of the rail is milled and ground to remove about 1mm within 1.5m from the end, the surface Brinell hardness is detected at 10mm, 100mm and 10mm away from the end respectively. After 600mm from the end, the detection interval is 10mm, and the detection is continued to the position of 1.5m. The heat-affected softening zone is distributed between 1m and 1.5m where the hardness value is lower than HB380.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for manufacturing 60AT1-60kg / m forged alloy steel special-shaped rail, characterized in that: The following steps are involved: (1) Heating: The forged special-shaped rail heel end is heated over the entire cross section, heated to 600-650°C at a first heating rate and then kept warm for a first time, then heated to 900-920°C at a second heating rate and then kept warm for a second time; (2) Cooling: After the heating is completed, the forged special-shaped rail heel end is cooled to 600-800°C at a first air jet pressure and a first cooling rate, then cooled to 250-300°C at a second air jet pressure and a second cooling rate, and then cooled to below 200-250°C at a third air jet pressure and a third cooling rate; (3) Tempering: The forged special-shaped rail heel end is tempered after cooling. In the first stage, the temperature is raised to 200-240°C and kept at this temperature for the third time; in the second stage, the temperature is raised to 260-280°C and kept at this temperature for the fourth time, and finally air-cooled to room temperature.

2. The method for manufacturing 60AT1-60kg / m forged alloy steel special-shaped rail according to claim 1, characterized in that: In step (1), the temperature is increased from 300 to 600° C. to 600 to 650° C. at a first heating rate, wherein the first heating rate is greater than the second heating rate.

3. The method for manufacturing 60AT1-60kg / m forged alloy steel special-shaped rail according to claim 1, characterized in that: In step (1), the first heating rate is 2.5-3.5°C / s, and the second heating rate is 1.5-2.5°C / s.

4. The method for manufacturing 60AT1-60kg / m forged alloy steel special-shaped rail according to claim 1, characterized in that: The first insulation time in step (1) is 25 to 35 seconds, and the second insulation time is 15 to 25 seconds.

5. The method for manufacturing 60AT1-60kg / m forged alloy steel special-shaped rail according to claim 4, characterized in that: The first insulation time in step (1) is 30 seconds, and the second insulation time is 20 seconds.

6. The method for manufacturing 60AT1-60kg / m forged alloy steel special-shaped rail according to claim 1, characterized in that: In step (2), the first air jet pressure is 0.02-0.05 MPa, the second air jet pressure is 0.1-0.15 MPa, and the third air jet pressure is 0.05 MPa.

7. The method for manufacturing 60AT1-60kg / m forged alloy steel special-shaped rail according to claim 1, characterized in that: In step (2), the first cooling rate is 1-1.5°C / s, the second cooling rate is 1.5-2.5°C / s, and the third cooling rate is 1-1.2°C / s.

8. The method for manufacturing 60AT1-60kg / m forged alloy steel special-shaped rail according to claim 1, characterized in that: The third insulation time in step (3) is 60 to 90 min, and the fourth insulation time is 240 to 300 min.

9. The method for manufacturing 60AT1-60kg / m forged alloy steel special-shaped rail according to claim 1, characterized in that: In step (3), the temperature of the tempering is raised to 200°C in the first stage and to 280°C in the second stage.

10. A 60AT1-60kg / m forged alloy steel special-shaped rail, characterized in that: The forged alloy steel special-shaped rail is prepared by the manufacturing method of 60AT1-60kg / m as claimed in any one of claims 1 to 9, wherein the top surface hardness value of the forged alloy steel special-shaped rail is less than HBW380, the number of soft spots is less than 3, the hardness of the soft zone is between 317 and 375HB, and the width is not more than 30mm.

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