CN115870595A - Method for reducing width of high-strength pearlite steel rail joint softening zone - Google Patents
Method for reducing width of high-strength pearlite steel rail joint softening zone Download PDFInfo
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Abstract
The invention discloses a method for reducing the width of a high-strength pearlite steel rail joint softening zone, which comprises the following steps: the method comprises the following steps that a steel rail joint comprises five stages of pre-flashing, accelerated burning, upsetting and forging during welding, the surfaces to be welded of the steel rail are arranged in the pre-flashing stage and the flashing stage through flash blasting, the accelerated burning voltage and the flash accelerating speed are controlled in the accelerated burning stage, the upsetting amount is controlled in the upsetting stage, and the consumption of the steel rail and the forging time are controlled in the forging stage so as to reduce the width of a softening zone; the high-strength pearlite steel rail comprises, by weight, 0.72% -0.86% of carbon, 0.10% -1.00% of silicon, 0.60% -1.30% of manganese, no more than 0.020% of phosphorus and sulfur, no more than 0.3% of chromium, and no more than 0.01% of vanadium. The method effectively reduces the width of the high-strength pearlite steel rail joint softening area by controlling various parameters in the welding process, optimizes the performance of the heavy-duty steel rail welding joint, and ensures that the width of the high-strength pearlite steel rail joint softening area for the heavy-duty railway welded by the method is in a better level of 5-10 mm.
Description
Technical Field
The invention relates to the technical field of steel rail welding, in particular to a method for reducing the width of a high-strength pearlite steel rail joint softening zone.
Background
A large number of researches show that the damage of the steel rail welding joint accounts for a large proportion of the total damage of domestic and foreign heavy-load lines, and the method is the focus of attention of railway lines. In the service process of the upper track of the steel rail welding joint, the bonding strength of the steel rail joint determines whether the steel rail joint is easy to generate fatigue or brittle fracture, and the hardness of the longitudinal section of the steel rail joint determines the smoothness of different micro areas of the joint.
The softening area of the steel rail flash welding joint is an area with the hardness of the welding joint obviously lower than that of the base metal, and the hardness of the steel rail joint is softened. Unlike the joint re-austenitized region, which is less hard than the base material, the metals in the softened region do not undergo an austenitic transformation during heating, and the temperature range is generally in the annealing range of the metal in terms of its thermophysics, so the softened region is sometimes referred to as the annealed region. The softened region is also referred to as the spheroidized annealed region because the rail material is generally a granular pearlite structure after annealing. Generally, the joint softening zone has poor tensile and impact properties and is a weak link of the steel rail joint. Because the steel rail welding mainly carries out local heating on the end part of the steel rail, a transition zone always exists between a heating part and an unheated base metal, and the zone with lower hardness in the transition zone is a softening zone. The softened region is a region that is always present in a rail weld joint and cannot be completely eliminated. Under the condition of the same welding and post-welding processing method, the softening zones of the rail joints with different chemical compositions and supply states are different, and the Australian Standard AS specifies that the widths of the softening zones of the rails with different materials are different from 20mm to 40 mm. Generally, the narrower the softening zone is, the more beneficial the in-service performance of the joint. Therefore, reducing the width of the softened area of a rail joint is an advantageous way to improve the quality of the joint.
However, the heavy haul railway line is mainly characterized by a large axle weight as compared to a normal line or a high speed railway line. The current research shows that the axle load is the factor which has the greatest influence on the service performance of the upper rail, and the damages such as the abrasion of the steel rail base metal and the joint, the rolling contact fatigue damage, the impact dynamic load, the brittle fracture and the like are serious along with the increase of the axle load. In order to improve the most needed abrasion performance of the heavy-duty line steel rail, the strength and hardness of the heavy-duty line steel rail are both higher. The higher the strength and hardness of the steel rail, the poorer the welding performance of the steel rail, and the welded joint is a weak link on a railway line, so that the optimization of the performance of the heavy-load steel rail welded joint is still the research focus of the center of the prior art.
Accordingly, there is a need in the art for improved methods of reducing the softened area of high strength pearlitic rail joints.
Disclosure of Invention
In view of this, an object of the embodiments of the present invention is to provide a method for reducing the width of a softened region of a high-strength pearlitic rail joint, which effectively reduces the width of the softened region by controlling various parameters of a welding process, and far exceeds the requirements of the technical indexes specified by standards.
In view of the above, an embodiment of the present invention provides a method for reducing the width of the softened area of a high-strength pearlitic rail joint, comprising the steps of:
the method comprises the following steps that a steel rail joint comprises five stages of pre-flashing, accelerated burning, upsetting and forging during welding, the surfaces to be welded of the steel rail are arranged in the pre-flashing stage and the flashing stage through flash blasting, the accelerated burning voltage and the flash accelerating speed are controlled in the accelerated burning stage, the upsetting amount is controlled in the upsetting stage, and the consumption of the steel rail and the forging time are controlled in the forging stage so as to reduce the width of a softening zone;
the high-strength pearlite steel rail comprises, by weight, 0.72% -0.86% of carbon, 0.10% -1.00% of silicon, 0.60% -1.30% of manganese, no more than 0.020% of phosphorus, no more than 0.020% of sulfur, no more than 0.3% of chromium, and no more than 0.01% of vanadium.
In some embodiments, the high voltage time of the preflash stage is 45s to 65s, the high voltage is 370V to 440V, the preflash distance is 2mm to 10mm, and the flash speed is 0.1mm/s to 0.6mm/s.
In some embodiments, the low voltage time of the flash stage is 80s to 140s, the low voltage is 320V to 390V, and the flash speed is 0.1mm/s to 0.6mm/s.
In some embodiments, the accelerated burning voltage of the accelerated burning stage is 380V-450V, and the flash acceleration speed is 0.5 mm/s-2.0 mm/s.
In some embodiments, the amount of upset in the upset stage is 5.0mm to 18.0mm.
In some embodiments, the rail consumption during the forging stage is between 2.0mm and 4.0mm and the forging time is between 1.5s and 3.0s.
In some embodiments, the rail joint is welded using a moving flash welding process.
The invention also provides a high-strength pearlitic steel rail joint treated by the method, wherein the width of a softening zone of the high-strength pearlitic steel rail joint is 5-10 mm.
The invention has at least the following beneficial technical effects:
the method of the invention divides the welding process into 5 main stages of pre-flashing, accelerated burning, upset forging and forging, effectively reduces the width of the softening area of the high-strength pearlite steel rail joint by controlling various parameters of the welding process, optimizes the performance of the welding joint of the heavy-duty steel rail, ensures that the width of the softening area of the high-strength pearlite steel rail joint for the heavy-duty railway welded by the method is in a better level of 5-10 mm, ensures that the widths of the softening areas at two sides of a fusion line are equivalent, ensures that the difference between the maximum value and the minimum value is 1-4 mm, meets the technical index requirements specified by far exceeding standards, and ensures that the other performances of the joint also meet the standard requirements.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other embodiments can be obtained by using the drawings without creative efforts.
FIG. 1 is a schematic view of an embodiment of a high-strength pearlitic steel rail flash welded joint softening zone provided by the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention are described in further detail with reference to the accompanying drawings.
It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are used for distinguishing two entities with the same name but different names or different parameters, and it should be noted that "first" and "second" are merely for convenience of description and should not be construed as limitations of the embodiments of the present invention, and they are not described in any more detail in the following embodiments.
The invention provides a method for reducing the width of a softening region of a high-strength pearlite steel rail joint aiming at the problem that the width of the softening region of a continuous flash welding joint of a high-strength pearlite steel rail for a heavy-load railway is too wide to meet standard requirements, and as shown in figure 1, the method provided by the invention comprises the following steps:
the method comprises the following steps that a steel rail joint comprises five stages of pre-flashing, accelerated burning, upsetting and forging during welding, the surfaces to be welded of the steel rail are arranged in the pre-flashing stage and the flashing stage through flash blasting, the accelerated burning voltage and the flash accelerating speed are controlled in the accelerated burning stage, the upsetting amount is controlled in the upsetting stage, and the consumption of the steel rail and the forging time are controlled in the forging stage so as to reduce the width of a softening zone;
the high-strength pearlite steel rail comprises, by weight, 0.72-0.86% of carbon, 0.10-1.00% of silicon, 0.60-1.30% of manganese, no more than 0.020% of phosphorus and sulfur, no more than 0.3% of chromium, and no more than 0.01% of vanadium.
Further, the minimum tensile strength of the steel rail is 1080MPa, and the minimum hardness of the rail head is 310HB.
In the continuous flash welding, the flash process is mainly realized by pre-flash, flash and accelerated burning, and the flash process is stable, continuous and uninterrupted. In order to reduce the width of the high-strength pearlite rail joint softening zone, the heat input, heat conduction time and high-temperature rail consumption of each stage of the welding process need to be strictly controlled.
The main effect of the pre-flashing stage is to enable the to-be-welded section of the steel rail to be flat and clean through flash blasting, and provide favorable conditions and basic heat for subsequent flashing, wherein the favorable conditions and the basic heat are relatively uniform and flat. In order to control the heat quantity, the heat conduction time and the consumption of the high-temperature steel rail, the high-voltage time, the high voltage, the pre-flashing distance and the flashing speed at the stage are mainly controlled. In some embodiments, the high voltage time of the preflash stage is 45s to 65s, the high voltage is 370V to 440V, the preflash distance is 2mm to 10mm, and the flash speed is 0.1mm/s to 0.6mm/s.
The main effect of the flash stage is to make the section to be welded of the steel rail smooth and clean through flash blasting, so as to provide favorable conditions and basic heat for subsequent flash, which are relatively uniform and smooth. The low voltage time, low voltage and flash speed of the stage are mainly controlled for the purpose of controlling the heat and heat conduction time. In some embodiments, the low voltage time of the flash stage is 80s to 140s, the low voltage is 320V to 390V, and the flash speed is 0.1mm/s to 0.6mm/s.
The accelerated burning stage mainly has the function of forming protective atmosphere for preventing end surface oxidation in the whole welding area, and finally forming proper temperature field distribution to provide conditions for upset forging. For the purpose of controlling the heat and the heat conduction time, the accelerated burning voltage and the flash acceleration speed of the stage are mainly controlled. In some embodiments, the accelerated burning voltage of the accelerated burning stage is 380V-450V, and the accelerated speed is 0.5 mm/s-2.0 mm/s.
The main function of the upsetting stage is to make the steel rail to be welded in a high-temperature plastic state produce interatomic bonding. In order to control the consumption of the steel rail, the upsetting amount at the stage is mainly controlled. In some embodiments, the upset amount in the upset stage is 5.0mm to 18.0mm.
The forging stage is mainly used for continuously applying load to the rail joint in the process of crystallizing the joint metal after the steel rail is upset. In order to control the consumption of the steel rail and further reduce the width of the high-strength pearlite steel rail joint softening zone, the consumption of the steel rail and the forging time at the stage are mainly controlled. In some embodiments, the rail consumption during the forging stage is between 2.0mm and 4.0mm and the forging time is between 1.5s and 3.0s.
The invention also provides a high-strength pearlite steel rail joint treated by the method, wherein the width of a rail joint softening region is in a better level of 5-10 mm, the widths of the softening regions on two sides of a fusion line are equivalent, the difference value between the maximum value and the minimum value is 1-4 mm, and the technical index requirements are far beyond the standard regulation.
The invention will be further explained below on the basis of specific embodiments.
Example 1
In this example, the mass fraction of carbon in the steel rail material for testing was 0.73%, the mass fraction of silicon was 0.81%, and the mass fraction of manganese was 1.12%. The tensile strength of the steel rail is 1180MPa to 1200MPa, and the hardness of the rail head is 310HB to 320HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 45s, the high voltage is 370V, the pre-flashing distance is 10mm, and the flashing speed is 0.6mm/s; the low-voltage time of the flashing stage is 80s, the low voltage is 320V, and the flashing speed is 0.6mm/s; the accelerated burning voltage in the accelerated burning stage is 380V, and the accelerated speed is 2.0mm/s; the upsetting amount in the upsetting stage is 18.0mm; the consumption of the steel rail in the forging stage is 4.0mm, and the forging time is 3.0s. Through inspection, the widths of the softening zones at the left side and the right side of the steel rail joint in the embodiment are respectively 6mm and 7mm, the difference value between the maximum value and the minimum value is 1mm, the technical index requirements of standard regulation are far exceeded, and the other properties of the joint also meet the standard requirements.
Example 2
In this example, the mass fraction of carbon in the steel rail material for testing was 0.73%, the mass fraction of silicon was 0.81%, and the mass fraction of manganese was 1.12%. The tensile strength of the steel rail is 1180MPa to 1200MPa, and the hardness of the rail head is 310HB to 320HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 65s, the high voltage is 440V, the pre-flashing distance is 2mm, and the flashing speed is 0.1mm/s; the low-voltage time of the flashing stage is 140s, the low voltage is 390V, and the flashing speed is 0.1mm/s; the accelerated burning voltage in the accelerated burning stage is 450V, and the accelerated speed is 0.5mm/s; the upsetting amount in the upsetting stage is 5.0mm; the consumption of the steel rail in the forging stage is 2.0mm, and the forging time is 1.5s. Through inspection, the widths of the softening areas on the left side and the right side of the steel rail joint in the embodiment are respectively 9mm and 5mm, the difference value between the maximum value and the minimum value is 4mm, the technical index requirements far exceeding the standard are met, and the other performances of the joint also meet the standard requirements.
Example 3
In this example, the mass fraction of carbon in the steel rail material for testing was 0.86%, the mass fraction of silicon was 0.58%, and the mass fraction of manganese was 0.81%. The tensile strength of the steel rail is 1280MPa to 1420MPa, and the rail head hardness is 370HB to 420HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 45s, the high voltage is 370V, the pre-flashing distance is 10mm, and the flashing speed is 0.6mm/s; the low-voltage time of the flashing stage is 80s, the low voltage is 320V, and the flashing speed is 0.6mm/s; the accelerated burning voltage in the accelerated burning stage is 380V, and the accelerated speed is 2.0mm/s; the upsetting amount in the upsetting stage is 18.0mm; the consumption of the steel rail in the forging stage is 4.0mm, and the forging time is 3.0. Through inspection, the widths of the softening zones at the left side and the right side of the steel rail joint in the embodiment are respectively 5mm and 7mm, the difference value between the maximum value and the minimum value is 2mm, the technical index requirements far exceeding the standard specification are met, and the other properties of the joint also meet the standard requirements.
Example 4
In this example, the mass fraction of carbon in the steel rail material for testing was 0.86%, the mass fraction of silicon was 0.58%, and the mass fraction of manganese was 0.81%. The tensile strength of the steel rail is 1280MPa to 1420MPa, and the rail head hardness is 400HB to 420HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 65s, the high voltage is 440V, the pre-flashing distance is 2mm, and the flashing speed is 0.1mm/s; the low-voltage time of the flashing stage is 140s, the low voltage is 390V, and the flashing speed is 0.1mm/s; the accelerated burning voltage in the accelerated burning stage is 450V, and the accelerated speed is 0.5mm/s; the upsetting amount in the upsetting stage is 5.0mm; the consumption of the steel rail in the forging stage is 2.0mm, and the forging time is 1.5s. Through inspection, the widths of the softening zones at the left side and the right side of the steel rail joint in the embodiment are respectively 9mm and 6mm, the difference value between the maximum value and the minimum value is 3mm, the technical index requirements of standard regulation are far exceeded, and the other properties of the joint also meet the standard requirements.
Example 5
In this example, the mass fraction of carbon in the steel rail material for testing was 0.82%, the mass fraction of silicon was 0.70%, and the mass fraction of manganese was 0.92%. The tensile strength of the steel rail is 1180MPa to 1300MPa, and the hardness of the rail head is 350HB to 410HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 50s, the high voltage is 4050V, the pre-flashing distance is 5mm, and the flashing speed is 0.3mm/s; the low-voltage time of the flashing stage is 110s, the low voltage is 385V, and the flashing speed is 0.5mm/s; the accelerated burning voltage in the accelerated burning stage is 420V, and the accelerated speed is 1.2mm/s; the upsetting amount in the upsetting stage is 11.0mm; the consumption of the steel rail in the forging stage is 2.6mm, and the forging time is 2.1s. Through inspection, the widths of the softening zones at the left side and the right side of the steel rail joint in the embodiment are respectively 9mm and 7mm, the difference value between the maximum value and the minimum value is 2mm, the technical index requirements far exceeding the standard specification are met, and the other properties of the joint also meet the standard requirements.
Comparative example 1
In the comparative example, the mass fraction of carbon in the steel rail material for testing was 0.73%, the mass fraction of silicon was 0.81%, and the mass fraction of manganese was 1.12%. The tensile strength of the steel rail is 1180MPa to 1200MPa, and the hardness of the rail head is 310HB to 320HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 40s, the high voltage is 360V, the pre-flashing distance is 11mm, and the flashing speed is 0.7mm/s; the low-voltage time of the flash stage is 70s, the low voltage is 310V, and the flash speed is 0.8mm/s; the accelerated burning voltage in the accelerated burning stage is 375V, and the accelerated speed is 2.3mm/s; the upsetting amount in the upsetting stage is 19.0mm; the consumption of the steel rail in the forging stage is 5.2mm, and the forging time is 3.4s. According to the test, the widths of the left and right softening regions of the steel rail joint in the comparative example are respectively 4mm and 5mm, the difference value of the widths of the left and right softening regions of the fusion line is 1mm, and the joint is broken and does not meet the standard requirement when the static bending load reaches 800kN in the static bending test process. The main difference between this comparative example and examples 1 and 2 is in the welding method. The comparative example uses a high pressure time, a low pressure time, a short continuous flash process, a low weld heat input, lower than that claimed in the patent; by adopting the voltage value lower than the patent claims, the continuous flashing process is not violent, and the welding heat input is small; the flash speed of each stage is higher than that of the patent claims, so that the high-temperature metal is consumed quickly, the generated heat is consumed quickly, and the welding heat input is small; the amount of the top end, the forging amount and the forging time which are higher than the requirements of the patent are adopted, the high-temperature consumption of the steel rail is large, the heat loss is large, a cold joint is formed, although the softening area is narrow, the other performances of the joint are sharply reduced. Under the condition that the materials of the steel rails are the same, the expected effect cannot be achieved by adopting the method for the comparative example.
Comparative example 2
In the comparative example, the mass fraction of carbon in the steel rail material for testing was 0.73%, the mass fraction of silicon was 0.81%, and the mass fraction of manganese was 1.12%. The tensile strength of the steel rail is 1180MPa to 1200MPa, and the hardness of the rail head is 310HB to 320HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 69s, the high voltage is 450V, the pre-flashing distance is 2mm, and the flashing speed is 0.1mm/s; the low-voltage time of the flash stage is 152s, the low voltage is 400V, and the flash speed is 0.1mm/s; the accelerated burning voltage in the accelerated burning stage is 420V, and the accelerated speed is 0.4mm/s; the upsetting amount in the upsetting stage is 4.0mm; the consumption of the steel rail in the forging stage is 0.5mm, and the forging time is 1.0s. According to the test, the widths of the softening zones at the left side and the right side of the steel rail joint in the comparative example are respectively 22mm and 23mm, and the difference value of the widths of the softening zones at the left side and the right side of the fusion line is 1mm, so that the standard requirement is not met. The main difference between this comparative example and examples 1 and 2 is in the welding method. The comparative example adopts a high pressure time and a low pressure time which are higher than the patent claims, the continuous flashing process is long, and the welding heat input is large; the voltage value higher than the patent claims is adopted, the continuous flashing process is violent, and the welding heat input is large; the flash speed of each stage is lower than that of the patent claims, so that the consumption of high-temperature metal is low, the loss of generated heat is low, and the welding heat input is large; by adopting the amount of the top end and the forging amount and time which are lower than the patent claims, the high-temperature consumption of the steel rail is less, the heat loss is less, and the width of the joint softening area is too wide. Under the condition that the materials of the steel rails are the same, the expected effect cannot be achieved by adopting the method of the comparative example.
Comparative example 3
In the comparative example, the mass fraction of carbon in the steel rail material for test was 0.86%, the mass fraction of silicon was 0.58%, and the mass fraction of manganese was 0.81%. The tensile strength of the steel rail is 1280MPa to 1420MPa, and the rail head hardness is 370HB to 420HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 40s, the high voltage is 360V, the pre-flashing distance is 11mm, and the flashing speed is 0.7mm/s; the low-voltage time of the flash stage is 70s, the low voltage is 310V, and the flash speed is 0.8mm/s; the accelerated burning voltage in the accelerated burning stage is 375V, and the accelerated speed is 2.3mm/s; the upsetting amount in the upsetting stage is 19.0mm; the consumption of the steel rail in the forging stage is 5.2mm, and the forging time is 3.4s. According to the test, the widths of the left and right softening regions of the steel rail joint in the comparative example are respectively 4mm and 5mm, the difference value of the widths of the left and right softening regions of the fusion line is 1mm, and the joint is broken and does not meet the standard requirement when the static bending load reaches 800kN in the static bending test process. The main difference between this comparative example and examples 3 and 4 is in the welding method. The comparative example uses a high pressure time, a low pressure time, a short continuous flashing process, a low welding heat input, which are lower than the patent claims; by adopting the voltage value lower than the patent claims, the continuous flashing process is not violent, and the welding heat input is small; the flash speed of each stage is higher than that of the patent claims, so that the high-temperature metal is consumed quickly, the generated heat is consumed quickly, and the welding heat input is small; by adopting the amount of the top end and the forging amount and time which are higher than the patent claims, the steel rail consumes much high temperature, the heat loss is large, a cold joint is formed, and although the softening zone is narrow, the other performances of the joint are reduced sharply. Under the condition that the materials of the steel rails are the same, the expected effect cannot be achieved by adopting the method of the comparative example.
Comparative example 4
In the comparative example, the mass fraction of carbon in the steel rail material for testing was 0.86%, the mass fraction of silicon was 0.58%, and the mass fraction of manganese was 0.81%. The tensile strength of the steel rail is 1280MPa to 1420MPa, and the rail head hardness is 370HB to 420HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 80s, the high voltage is 420V, the pre-flashing distance is 2mm, and the flashing speed is 0.1mm/s; the low-voltage time of the flashing stage is 170s, the low voltage is 400V, and the flashing speed is 0.1mm/s; the accelerated burning voltage in the accelerated burning stage is 420V, and the accelerated speed is 2.5mm/s; the upsetting amount in the upsetting stage is 3.0mm; the consumption of the steel rail in the forging stage is 2.0mm, and the forging time is 1.0. According to the test, the widths of the left and right softening zones of the steel rail joint in the comparative example are respectively 25mm and 26mm, the difference value of the widths of the left and right softening zones of the fusion line is 1mm, the standard requirement is not met, meanwhile, in a static bending test, when a static bending load reaches 1500kN, the joint is broken, the maximum bending value is 8.4mm, and the standard requirement is not met. The main difference between this comparative example and examples 1 and 2 is in the welding method. The comparative example uses a high pressure time, a low pressure time, a long continuous flash process, a high welding heat input, which are higher than the patent claims; the voltage value higher than the patent claims is adopted, the continuous flashing process is violent, and the welding heat input is large; the flash speed of each stage is lower than that of the patent claims, so that the high-temperature metal consumption is low, the generated heat loss is low, and the welding heat input is large; by adopting the amount of the top end and the forging amount and time which are lower than the patent claims, the high-temperature consumption of the steel rail is less, the heat loss is less, and the width of the joint softening area is too wide. Meanwhile, when the welding heat input is too large and the upsetting amount is too small, the bonding strength of the steel rail is reduced, and the static bending performance is sharply reduced. Under the condition that the materials of the steel rails are the same, the expected effect cannot be achieved by adopting the method for the comparative example.
Comparative example 5
In the steel rail material for test in this comparative example, the mass fraction of carbon was 0.82%, the mass fraction of silicon was 0.70%, and the mass fraction of manganese was 0.92%. The tensile strength of the steel rail is 1180MPa to 1300MPa, and the hardness of the rail head is 350HB to 410HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 40s, the high voltage is 360V, the pre-flashing distance is 11mm, and the flashing speed is 0.7mm/s; the low-voltage time of the flash stage is 70s, the low voltage is 310V, and the flash speed is 0.8mm/s; the accelerated burning voltage in the accelerated burning stage is 375V, and the accelerated speed is 2.3mm/s; the upsetting amount in the upsetting stage is 20.0mm; the consumption of the steel rail in the forging stage is 5.2mm, and the forging time is 3.4s. According to the test, the widths of the softening areas on the left side and the right side of the steel rail joint in the comparative example are respectively 3mm and 5mm, the difference value of the widths of the softening areas on the left side and the right side of the fusion line is 2mm, in the static bending test process of the joint, when the static bending load reaches 1000kN, the joint is broken, the maximum bending value is 7.6mm, the standard requirement is not met, and abnormal martensite structures are detected at the standard test position of the joint and the standard requirement is not met. The main difference between this comparative example and example 5 is in the welding method. The comparative example uses a high pressure time, a low pressure time, a short continuous flash process, a low weld heat input, lower than that claimed in the patent; by adopting the voltage value lower than the patent claims, the continuous flashing process is not violent, and the welding heat input is small; the flash speed of each stage is higher than that of the patent claims, so that the high-temperature metal is consumed quickly, the generated heat is consumed quickly, and the welding heat input is small; by adopting the amount of the top end and the forging amount and time which are higher than the patent claims, the steel rail consumes much high temperature, the heat loss is large, a cold joint is formed, and although the softening zone is narrow, the other performances of the joint are reduced sharply. Meanwhile, because the heat input of the joint is too small, the cooling rate in the cooling process is high, and the local area is easy to generate martensite phase transformation. Under the condition that the materials of the steel rails are the same, the expected effect cannot be achieved by adopting the method of the comparative example.
Comparative example 6
In the comparative example, the mass fraction of carbon in the steel rail material for testing was 0.82%, the mass fraction of silicon was 0.70%, and the mass fraction of manganese was 0.92%. The tensile strength of the steel rail is 1180MPa to 1300MPa, and the hardness of the rail head is 350HB to 410HB. The high-voltage time of the pre-flashing stage of continuous flash welding is 85s, the high voltage is 415V, the pre-flashing distance is 2mm, and the flashing speed is 0.1mm/s; the low-voltage time of the flashing stage is 172s, the low voltage is 410V, and the flashing speed is 0.1mm/s; the accelerated burning voltage in the accelerated burning stage is 425V, and the accelerated speed is 2.5mm/s; the upsetting amount in the upsetting stage is 3.0mm; the consumption of the steel rail in the forging stage is 2.0mm, and the forging time is 1.0. According to the test, the widths of the softening areas on the left side and the right side of the steel rail joint in the comparative example are respectively 24mm and 25mm, the difference value of the widths of the softening areas on the left side and the right side of the fusion line is 1mm, the standard requirement is not met, meanwhile, in a static bending test, when the static bending load reaches 1600kN, the joint is broken, the maximum bending value is 9.3mm, and the standard requirement is not met. The main difference between this comparative example and example 5 is in the welding method. The comparative example adopts a high pressure time and a low pressure time which are higher than the patent claims, the continuous flashing process is long, and the welding heat input is large; the voltage value higher than the patent claims is adopted, the continuous flashing process is violent, and the welding heat input is large; the flash speed of each stage is lower than that of the patent claims, so that the consumption of high-temperature metal is low, the loss of generated heat is low, and the welding heat input is large; by adopting the amount of the top end and the forging amount and time which are lower than the patent claims, the high-temperature consumption of the steel rail is less, the heat loss is less, and the width of the joint softening area is too wide. Meanwhile, when the welding heat input is too large and the upsetting amount is too small, the bonding strength of the steel rail is reduced, and the static bending performance is sharply reduced. Under the condition that the materials of the steel rails are the same, the expected effect cannot be achieved by adopting the method of the comparative example.
The foregoing is an exemplary embodiment of the present disclosure, but it should be noted that various changes and modifications could be made herein without departing from the scope of the present disclosure as defined by the appended claims. The functions, steps and/or actions of the method claims in accordance with the disclosed embodiments described herein need not be performed in any particular order. Furthermore, although elements of the disclosed embodiments of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.
It should be understood that, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly supports the exception. It should also be understood that "and/or" as used herein is meant to include any and all possible combinations of one or more of the associated listed items.
The numbers of the embodiments disclosed in the embodiments of the present invention are merely for description, and do not represent the merits of the embodiments.
It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware, and the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.
Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, of embodiments of the invention is limited to these examples; within the idea of an embodiment of the invention, also technical features in the above embodiment or in different embodiments may be combined and there are many other variations of the different aspects of the embodiments of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, substitutions, improvements, and the like that may be made without departing from the spirit and principles of the embodiments of the present invention are intended to be included within the scope of the embodiments of the present invention.
Claims (8)
1. The method for reducing the width of the softened zone of the high-strength pearlite steel rail joint is characterized in that the steel rail joint comprises five stages of pre-flashing, accelerated burning, upsetting and forging during welding, the pre-flashing stage and the flashing stage finish the surface to be welded of the steel rail through flash blasting, the accelerated burning stage controls accelerated burning voltage and flash accelerated speed, the upsetting stage controls upsetting amount, and the forging stage controls steel rail consumption and forging time to reduce the width of the softened zone;
the high-strength pearlite steel rail comprises, by weight, 0.72% -0.86% of carbon, 0.10% -1.00% of silicon, 0.60% -1.30% of manganese, no more than 0.020% of phosphorus, no more than 0.020% of sulfur, no more than 0.3% of chromium, and no more than 0.01% of vanadium.
2. The method for reducing the width of the softening zone of the high-strength pearlitic steel rail joint according to claim 1, wherein the high-pressure time of the pre-flashing stage is 45s to 65s, the high voltage is 370V to 440V, the pre-flashing distance is 2mm to 10mm, and the flashing speed is 0.1mm/s to 0.6mm/s.
3. The method for reducing the width of the high-strength pearlitic steel rail joint softening zone according to claim 1, wherein the low-pressure time of the flashing stage is 80-140 s, the low-voltage is 320-390V, and the flashing speed is 0.1-0.6 mm/s.
4. The method for reducing the width of the softening zone of the high-strength pearlitic steel rail joint according to claim 1, wherein the accelerated burning voltage of the accelerated burning stage is 380V to 450V, and the flash acceleration speed is 0.5mm/s to 2.0mm/s.
5. The method of reducing the width of the softened region of a high strength pearlitic rail joint according to claim 1 wherein said upset amount during said upset stage is in the range of 5.0mm to 18.0mm.
6. The method for reducing the width of the softened region of a high-strength pearlitic rail joint according to claim 1, wherein said consumption of said rail during said forging stage is between 2.0mm and 4.0mm and said forging time is between 1.5s and 3.0s.
7. A method of reducing the width of the softened region of a high strength pearlitic rail joint according to claim 1 wherein said rail joint is welded using a moving flash weld.
8. A high strength pearlitic rail joint treated by the method defined in any one of the preceding claims wherein the high strength pearlitic rail joint has a softened zone width of from 5mm to 10mm.
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| CN202211368320.3A CN115870595A (en) | 2022-11-03 | 2022-11-03 | Method for reducing width of high-strength pearlite steel rail joint softening zone |
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| CN202211368320.3A CN115870595A (en) | 2022-11-03 | 2022-11-03 | Method for reducing width of high-strength pearlite steel rail joint softening zone |
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