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    • 专利摘要:
    The present invention relates to a wear resistant bainitic needle which contains bainitic ferrite in the form of flakes in the 30 mm depth range of the surface layer of the rail head (1) to the core portion and point-shaped and / or bar-shaped carbides having an average length of 0.05 to 0.5 μm dispersed on the bainitic ferrite, the carbides being oriented in a direction at an angle of 40 to 70 ° inclusive from to the direction of the major axis of bainitic ferrite, the ratio of area between carbides and bainitic ferrite being 0.001 to 1: 100. The present invention further describes a method for producing the wear resistant bainitic needle. The bainitic needle described in the present invention has outstanding toughness and wear resistance properties, and is therefore advantageous for extending the life of needles, particularly heavy transport railroad connections which are used in difficult operating conditions.
    公开号:FR3021331A1
    申请号:FR1554351
    申请日:2015-05-13
    公开日:2015-11-27
    发明作者:Zhenyu Han；Ming Zou；Jihai Jia；Hua Guo；Dadong Li；Yong Deng；Chunjian Wang；Jun Yuan
    申请人:Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd；
    IPC主号:
    专利说明:

    [0001] The present invention relates to a wear resistant bainitic needle and a method of producing the same. As key parts that support frequent impacts of the train wheels and guide the change of direction of the train, track connections are closely related to the operational efficiency and safety of the railways in terms of quality, performance and life of these. The quality of a railroad connection depends mainly on the quality of its raw material (steel needles, also called needles), in addition to the processing and manufacturing techniques. In recent years, as they have been rapidly developed into a heavy transport trend, the operating conditions of needles have become increasingly demanding. Therefore, in some sections of track, railway switches must be replaced after being used for a few months or even tens of days. This problem seriously limits the rapid development of railways. In the development of needles, the needles should be developed not only to meet the requirement of high rigidity, but also to achieve better toughness matching, to improve overall needle performance, including high impact resistance. , high resistance to contact fatigue, and high resistance to wear. At the present time, widely applied products are still products of perlite rail hook-ups and crossings, while bainitic steel products have attracted a lot of interest because of their toughness, their overall best performance, and their broad application prospects. Based on the properties of bainitic steel, the impact resistance of bainitic products is much higher than that of perlite products, and the impact resistance and chipping resistance of bainite connection needle blades are higher. However, a problem of rapid wear has not yet been solved effectively, especially for heavy transport railways. Presently, bainitic needles are produced primarily by rolling, air-cooling and subsequent-income processes as described in patent documents CN-C100471974 and CN-C-1166804, etc. In addition, accelerated cooling can be used after rolling to obtain thinner bainitic structures. In CN-A-1095421, a method for producing high strength bainitic steel rails which have excellent rolling contact fatigue damage performance is disclosed, comprising: the use of residual heat of a steel rail which contains appropriate components, cooling of the upper surface of the steel rail at a cooling rate of 1 to 10 ° C / s and stopping of accelerated cooling when the temperature of the rail in steel is in the range of 500 to 300 ° C, and then the cooling of the steel rail by natural cooling or controlled cooling at room temperature, so as to obtain a steel rail which has a hardness of 300 to 400 HV on its surface and a hardness of 350 HV or higher at the angles of the upper surface. However, a problem in this process is that, since the cross-section of an ordinary steel rail is a symmetrical section, the specification for normal use of ordinary steel rails can be satisfied only as long as the required performance of the rails steel in the surface layer and in a specific depth range is taken into consideration when accelerated cooling is performed; on the other hand, the needles, as a raw material for the production of railway switches, can only be used after milling the railhead part. For example, in the case of switches used on railways in China, the needles are treated up to 23 mm deep, that is, the part within 23 mm of depth below the surface layer. rail head is milled. Therefore, for the needles, not only must the performance of the rail head surface layer be in accordance with the specification, but also the performance of the core part must be taken into consideration. In addition, since the cross-section of a needle is an asymmetrical section, the area of the working side of the rail head represents a higher percentage compared to the area of the non-working side. If both sides are cooled in the same way, the cooling rate of the working side of the rail head is lower due to the higher heat capacity of the working side during the accelerated cooling process; therefore, an excellent result can not be achieved on both sides; more seriously, in the cooling process, the side that is cooled to a higher cooling rate bends toward the side that is cooled to a lower cooling rate, and this phenomenon has detrimental effects on the straightness of the entire length of the needle and on the subsequent recovery process. In CN-C-1086743, a bainitic steel rail which has a high resistance to fatigue damage of the surface and a high wear resistance performance is presented. The microscopic structure of the bainitic steel rail is characterized in that: on a given cross section of the bainitic structure, the total area of the carbides having a major axis in the range of 100 to 1000 nm represents 10 to 50% of the total area of the cross section. This technique has the following obvious drawbacks: as a hard phase in steel, if the carbides represent too high a percentage or if the carbides have a concentrated distribution in the steel, the cracks formed in the steel rail develop under stress preferentially along the carbides, which causes fatigue damage such as cracks and flaking or even fractures of the needle, which affects the safety of operation. Although steps have been taken to reduce the carbide sizes in the invention to avoid the above problems, these problems can not be effectively solved at the base, as the percentage of carbides is too high.
    [0002] In summary, existing processes can not meet the requirement of wear resistant needles. There is an urgent need for a bainitic needle product which has an excellent wear resistance performance and which can meet the demand for the development of railways in the future. The object of the present invention is to provide a wear resistant bainitic needle and a method for producing this wear resistant bainitic needle. The bainitic needle exhibits outstanding toughness and wear resistance properties, and is therefore advantageous for extending the life of the needles, particularly heavy transport railroad tracks which are used under conditions of wear and tear. difficult operation.
    [0003] To achieve the objective described above, the present invention provides a wear resistant bainitic needle which contains bainitic ferrite in the form of flakes in the 30 mm depth range of the rail head surface layer. at the core portion and carbides in the form of dots and / or bars of an average length of 0.05 to 0.5 μm dispersed on the bainitic ferrite, the carbides being oriented in a direction at an angle of 40 to 70 ° included with respect to the direction of the major axis of the bainitic ferrite, the ratio of area between the carbides and the bainitic ferrite being from 0.001 to 1: 100. By their study, the inventors have found that: similarly to the case of carbides in pearlitic steel, the carbides are precipitated and the carbide sizes in bainitic steel have clear influences on the resistance performance of the steel. wear and the life of the needles. During the operation of a needle, the needle is impacted by the train wheels and complex stresses in all directions, and the needle blade portion is worn, deteriorated, deformed, and eventually fails. under the effects of impacts and constraints in all directions. As seen under the microscope, as a soft phase in the steel of a needle, bainitic ferrite does not have sufficient wheel impact and wear resistance, even though it has been reinforced during accelerated cooling after rolling, and finally the needle blade portion becomes defective and can not meet the specification for its use due to severe wear. On the other hand, carbides, which are a hard phase in steel, will progressively precipitate from bainitic ferrite and concentrate while the steel is worn during operation, and so withstand the stress exerted by them. wheels together and can improve the wear resistance of steel. As for the sizes, shapes, distribution and percentage of carbides in bainitic steel for the branch needle blade, the inventors have found that: when the carbides in the form of bars or in the form of strips of a length not exceeding 0.5 μm and oriented in a direction at an angle of 40 to 70 ° inclusive with respect to the long axis direction of the bainitic ferrite precipitate from the bainitic ferrite matrix, the wear resistance property of the The needle can be improved, while the rolling contact fatigue resistance property of the needle is hardly affected. Since railroad connections must not only withstand impact loads, but must also have a good contact fatigue resistance property, the specific surface area of the carbides in the steel of the needle should not be greater than 1%. If the percentage of the carbides is too high (for example, greater than 1%), although the wear resistance can be improved more effectively, the cracks formed at the part of the needle blade that comes in contact with the wheels develop along the carbides under external stress once they are formed, resulting in the formation of cracks and in flaking or even fractures, which adversely affect the operational safety. Therefore, the percentage of carbides should not be greater than 1%; preferably, in the present invention, the area ratio between carbides and bainitic ferrite is 0.001 to 1: 100. To achieve the object described above, the present invention further provides a method for producing wear-resistant bainitic needles, comprising: obtaining a needle with residual heat by a finish rolling of a steel material, the cooling of the needle with the residual heat up to a temperature located in the temperature range of the austenitic phase domain, and then the cooling of the rail head of the needle by accelerated cooling, the speeds accelerated cooling for the running surface of the rail head and the non-working side of the rail head being respectively 3.0 to 5.0 ° C / s, and the accelerated cooling rate for the working side of the rail mushroom is higher than the accelerated cooling rates for the rail head rolling surface and the non-working side of the rail head of 1.0 C / s; treatment of the needle obtained at 300 to 350 ° C for 7 to 9 hours when the temperature at the center of the running surface of the rail head falls to 200 to 250 ° C, and then the cooling of the needle at room temperature, to obtain a bainitic needle. In another aspect, the present invention further provides a bainitic needle obtained with the method for producing a wear resistant bainitic needle as described above. The bainitic needle obtained with the described method has excellent properties of toughness and wear resistance, and is therefore advantageous for extending the life of the needles, particularly heavy transport railroad connections which are used in difficult operating conditions. Other features and advantages of the present invention will be further detailed in the embodiments below. 302 1 3 3 1 6 The accompanying drawings are provided herein to facilitate a better understanding of the present invention, and form a part of this document. They are used in conjunction with the following embodiments to explain the present invention, but are not to be construed as constituting any limitation to the present invention. In the drawings: Fig. 1 is a transmission electron microscope image of the microscopic structure of the bainitic needle in a first embodiment of the present invention in a field of view under a transmission electron microscope; Fig. 2 is a schematic cross-sectional view of the needle provided in the present invention. Below, some embodiments of the present invention will be detailed with reference to the accompanying drawings. It should be appreciated that the embodiments described herein are provided solely to describe and explain the present invention, but should not be construed as constituting any limitation to the present invention. The present invention provides a wear resistant bainitic needle which contains bainitic ferrite in the form of flakes in the 30 mm depth range from the surface layer of the rail head to the core portion and the carbides under it. in the form of dots and / or in the form of bars with an average length of 0.05 to 0.5 μm dispersed on the bainitic ferrite, the carbides being oriented in a direction at an angle of 40 to 70 ° inclusive with respect to the direction of the major axis of bainitic ferrite, the ratio of area between carbides and bainitic ferrite being 0.001 to 1: 100. Preferably, the bainitic needle contains 0.15 to 0.30% by weight of C, 1.00 to 1.80% by weight of Si, 1.50 to 2.50% by weight of Mn, 0, 50 to 1.00% by weight of Cr, and 0.20 to 0.50% by weight of Mo, and the total percentage by weight of Mn and Cr is 2.20% by weight Mn + Cr 3.00 % by weight, the remaining part consists of Fe; in addition, the bainitic needle may further contain P, S, and unavoidable impurities. In the bainitic needle described in the present invention, preferably the weight percent of P is 0.005 to 0.020% by weight, and the weight percent of S is 0.001 to 0.008% by weight.
    [0004] As shown in FIG. 2, in the present invention, a rail head rolling surface 101 refers to the upper portion of the rail head that comes into contact with the wheels, a working side of the rail head 102 refers to to the part of the rail head that experiences the compaction and impact load of the wheels when a train is traveling on the rail after the rail head has been milled and assembled in a branch, and a non-working side of the rail rail head 103 refers to the opposite side of the rail head which does not come into contact with the wheels, the rail head 1 including the rail head race surface 101, the working side of the rail head 102 and the non-working side of the rail mushroom; a rail pad 2 refers to the lower part of the needle, and a center of the rail pad 201 refers to the central portion of the rail pad 2; a rail core 3 refers to the part that connects the rail head 1 to the rail pad 2 of a needle. These parts will not be detailed further here, since they are well known to those skilled in the art. The bainitic needle provided in the present invention has outstanding toughness and wear resistance properties, and is therefore advantageous for extending the life of the needles, particularly heavy transport railroad connections which are used in difficult operating conditions. The present invention further provides a method for producing wear resistant bainitic needles, comprising: obtaining a needle with residual heat by finishing rolling a steel material, cooling the needle with the residual heat to a temperature within the temperature range of the austenitic phase domain, and then the cooling of the needle rail head by accelerated cooling, the accelerated cooling rates for the rolling surface of the rail and the non-working side of the rail head being respectively 3.0 to 5.0 ° C / s, and the accelerated cooling rate for the working side of the rail head being higher than the cooling speeds accelerated for rail head rolling surface and non-working side of rail head of 1.0 ° C / s; treating said needle at 300 ° to 350 ° C. for 7 to 9 hours when the temperature at the center of the running surface of the rail head falls to 200 ° to 250 ° C., and then cooling. of the needle at room temperature, to obtain a bainitic needle. In the present invention, preferably the running surface of the rail head and the non-working side of the rail head are cooled to the same accelerated cooling rate. In the present invention, the needle with residual heat refers to a needle which is obtained by finishing rolling of a steel material and which has residual heat (has not yet been completely cooled); preferably, in the present invention, the temperature of the needle with residual heat is higher than the temperature range of the austenitic phase domain. In the present invention, unless specifically indicated otherwise, cooling refers to natural cooling, while accelerated cooling refers to forced cooling of a target object. In the present invention, the temperature is measured with an infrared thermometer. In the present invention, preferably the temperature of the needle at the beginning of the accelerated cooling (i.e., the initial cooling temperature) is 800 to 920 ° C. Below, the reasons for the settings of the processing parameters will be detailed. The accelerated cooling rates for the rail head rolling surface and the non-working side of the rail head are set at 3.0 to 5.0 ° C / s, and the accelerated cooling speed for the side of the railhead rail head work is set to be higher than the accelerated cooling rates for the rail head rolling surface and the non-working side of the rail head of 1.0 ° C, because, if accelerated cooling media which reaches the same accelerated cooling rate are applied to the running surface of the rail head and to both sides, the cooling rate of the working side is lower, i.e. that the heat supply from the core portion is higher, since the working side of the rail head has a larger specific area and a greater heat capacity; therefore, the working side of the rail head is cooled at a much slower speed than the rail head race surface and the non-working side of the rail head, and thereby the needle bends to one side, i.e., lateral bending occurs. This phenomenon not only has a strong impact on the following recovery procedure and results in abnormal situations such as breakage during straightening, etc., but also results in a significant increase in the residual stress in the center of the pad. Therefore, the needle does not meet the specification. The inventors have discovered that the above problem can be solved if the accelerated cooling rate is appropriately increased for the working side of the rail head in the accelerated cooling process. The accelerated cooling rate should be increased by 1.0 ° C / s. Below, the reason for setting the accelerated cooling rate at 3.0 to 5.0 ° C / s for the rail head rolling surface and the non-working side of the rail head will be explained: if the accelerated cooling rate is less than 3.0 ° C / sec, the surface temperature of the rail head surface does not decrease or even increase after a period during the accelerated cooling due to the feeding back heat from the core part of the rail head, and therefore the accelerated cooling objective can not be achieved; if the accelerated cooling rate is greater than 5.0 ° C / sec, martensitic structures can be formed in the surface layer of the rail head due to the high cooling rate, and therefore the operational safety of the connection may be compromised. When the temperature at the center of the rail head rolling surface drops to 200 to 250 ° C, the resulting needle is tempered at 300 to 350 ° C for 7 to 9 hours, and then the needle is cooled. at room temperature. By analysis, the inventors believe that the reason for the above result is that if the final accelerated cooling temperature is greater than 250 ° C, although fine bainitic structures have been obtained in the surface layer of the rail head, coarse bainitic structures appear in the core portion of the rail head, particularly in an area 30 mm or more from the rail head, and ultimately the performance of the needle blade portion is affected, and the performance overall operation of the branch can not be improved; if the final accelerated cooling temperature is below 200 ° C, the percentage of martensite in an area of the rail head surface layer at a specific depth is increased; therefore, the tenacity and plasticity of the needle are severely degraded, or even the needle can not be used. If the tempering temperature is less than 300 ° C, the toughness and plasticity of the steel are severely degraded, particularly at low temperature, and therefore the high tenacity property of the bainitic needle can not be used; furthermore, since carbides can not precipitate efficiently from steel, the wear resistance property of the needle can not be improved; if the tempering temperature is above 350 ° C, although the toughness and plasticity further increase, the strength and hardness decrease; therefore, it is difficult to obtain a needle with excellent overall performance. The duration of the income is set at 7 to 9 hours, because, compared to the standard steel rails, the time required for the treatment of income is longer for the needles, since the needles have a higher unit weight and a larger cross-section; if the income is shorter than 7 hours, the carbides in the steel, in particular the carbides in a deep zone of the rail head, can not precipitate as expected, and therefore the object of the present invention can not be achieved ; if the income is longer than 9 hours, the excessively long income does not bring significant benefits since the precipitation of carbides in the steel is already completed and the income objective has already been reached. After the treatment of income, the needle is discharged and then cooled by cooling with air at room temperature, so as to obtain the bainitic needle described in the present invention. Preferably, in the process described in the present invention, the steel contains 0.15 to 0.30% by weight of C, 1.00 to 1.80% by weight of Si, 1.50 to 2.50. % by weight of Mn, 0.50 to 1.00% by weight of Cr, and 0.20 to 0.50% by weight of Mo, and the percentage by total weight of Mn and Cr is 2.20% by weight Mn + Cr 3.00% by weight, the remaining part consists mainly of Fe, and the steel may further contain P, S, the remainder being Fe and unavoidable impurities; Preferably the weight percent of P being from 0.005 to 0.020% by weight, and the weight percent of S being from 0.001 to 0.008% by weight. Below, the reasons for confining the main chemical elements in the needle described in the present invention in the above ranges will be explained: 302 1 3 3 1 11 Carbon (C) is the most important element for that bainitic steel has a good toughness adequacy and overall mechanical performance. When the carbon content is less than 0.15% by weight, it is unable to give full play to the reinforcing effect, and the rigidity of the needle 5 is too low, the carbides in the needle can not precipitate effectively, and the wear resistance can not be improved effectively; when the carbon content is greater than 0.30% by weight, by the process described in the present invention, the strength of the steel is too high, while the toughness and plasticity are too low; therefore, the contact fatigue strength of the steel is severely affected because the percentage of carbides is too high, and the safety of application of the needle is compromised. Therefore, in the present invention, the carbon content is limited to 0.15 to 0.30% by weight. As an important additional element in steel, silicon (Si) generally exists in solid solution ferrite, and can improve the strength of the structure. When the silicon content is less than 1.00% by weight, for bainitic steel, on the one hand, the reinforcing effect is not significant because the concentration in solid solution is low; on the other hand, fine carbides can not be obtained, and therefore the objective of structural control in the present invention can not be achieved; when the silicon content is greater than 1.80% by weight, carbide precipitation is completely inhibited; instead, a large amount of residual austenite exists, and surface defects may occur; therefore, the regularity of the operation of the train can not be ensured. Therefore, in the present invention, the silicon content is limited to 1.00 to 1.80% by weight. Manganese (Mn) can significantly decrease the initial transition temperature of the bainitic structure, improve the hardness of carbides, and is an important additional element in bainitic steel. When the manganese content is less than 1.50% by weight, it is difficult to achieve the active effects for bainitic steel; when the manganese content is greater than 2.50% by weight, the hardness of the carbides is too high, and the property of fatigue resistance of the needle is severely degraded. Therefore, in the present invention, the manganese content is limited to 1.50 to 2.50% by weight. As a moderately sized carbide forming element, chromium (Cr) can bond with carbon in steel to form various carbides; in addition, chromium is useful for evenly distributing carbon in the steel, decreasing the size of the carbides, and thereby improving the wear resistance property of the needle. When the chromium content is less than 0.50% by weight, the hardness and the percentage of the carbides formed in the steel are low, and the carbides are concentrated in the form of flakes, which impairs the improvement of the wear resistance property of the needle; when the chromium content is greater than 1.00 by weight, the percentage of martensite in the steel is greatly increased, and therefore the safety of operation of the needle can not be ensured. Therefore, in the present invention, the chromium content is limited to 0.50 to 1.00% by weight. Molybdenum (Mo) has a remarkable effect in decreasing the initial transition temperature of the bainitic structure, and is advantageous for stabilizing and strengthening the bainitic structure. When the molybdenum content is less than 0.20 by weight, it is difficult to achieve the effects mentioned above; when the molybdenum content is greater than 0.50% by weight, the efficiency of the transition of the bainitic structure is greatly diminished, and therefore an ideal bainitic structure can not be obtained in the accelerated cooling process. Therefore, in the present invention, the molybdenum content is limited to 0.20 to 0.50% by weight.
    [0005] To ensure that the needle described in the present invention has a better operating performance, the inventors have found that the total weight percentage of Mn + Cr should be 2.20% by weight Mn + Cr 3.00% by weight . The reason is that Mn and Cr have similar effects in bainitic steel; when Mn + Cr <2.20% by weight, the strength, size and percentage of carbides in the steel can not meet the requirement described in the present invention; in addition, the carbide hardness is low, and a moderate wear resistance property can not be obtained; when Mn + Cr> 3.00% by weight, on the one hand, the hardness of the carbides is too high; on the other hand, severe segregation occurs locally in the needle, and therefore the uniformity of the bainitic structure and the performance of the bainitic structure in the needle can not be assured. Therefore, in the present invention, the total weight percent of Mn + Cr is limited to 2.20% by weight Mn + Cr 3.00% by weight.
    [0006] Preferably, in the process described in the present invention, the accelerated cooling medium is selected from one or more of compressed air, an air-water mixture and a gas-oil mixture. In the present invention, the needle with residual heat can be prepared by any method existing in the prior art. For example, the needle with residual heat can generally be prepared by the following steps: treating a steel material which contains the above-mentioned chemical components by melting in a converter or electric furnace, refining in a furnace pocket, vacuum treatment RH or pocket, and continuous casting, to obtain a continuous casting billet with specific dimensions in cross section; thereafter, charging the continuous casting billet in a traveling-beam furnace, heating to 1200 to 1300 ° C, and holding at that temperature for 3 hours or more, then rolling the steel billet into a needle with the required cross section; here, the final rolling temperature of the needle is 850 to 1000 ° C. In the present invention, preferably the needle with residual heat is raised in a rolling line operating continuously by means of a steel turning device, and the needle blade with the residual heat is fed into a heat treatment unit for the following accelerated cooling. In another aspect, the present invention further provides a bainitic needle obtained with the method for producing a wear resistant bainitic needle as described above. Hereinafter, the present invention will be further detailed in some embodiments. The chemical components and their contents in the steel materials used in Embodiments A1 to A6 and the comparative samples D1 to D6 in the present invention are shown in Table 1, and the remainder consists of Fe and unavoidable impurities.
    [0007] No. C If Mn PS Cr Mo Mn + Cr A1, D1 0.24 1.62 1.95 0.012 0.004 0.76 0.20 2.71 A2, D2 0.19 1.18 2.50 0.014 0.003 0, 50 0.32 3.00 A3, D3 0.15 1.80 1.50 0.010 0.003 1.00 0.41 2.50 A4, D4 0.23 1.64 1.77 0.012 0.003 0.68 0.50 2.45 A5, D5 0.26 1.00 2.18 0.009 0.004 0.56 0.39 2.74 A6, D6 0.30 1.30 1.87 0.014 0.005 0.91 0.24 2.78 Table 1: Samples tested compositions After the steel material that contains the components listed above was laminated to a 60AT needle, the needle is processed by the following method, and the treatment parameters are shown in Table 2. The steel material is subjected to finishing rolling to obtain a needle with residual heat; then, the needle with residual heat is cooled in the temperature range of the austenitic phase domain, and then the needle rail mushroom is cooled by accelerated cooling; when the temperature at the center of the running surface of the rail head is lowered to the final cooling temperature shown in Table 2, the resulting needle is processed by tempering, and then cooled to room temperature, to obtain a bainitic needle. Thus, the running surface of the rail head and the non-working side of the rail head are cooled to the same accelerated cooling rate. The accelerated cooling rate quoted in Table 2 is the accelerated cooling rate for the rail head rolling surface and the non-working side of the rail head, while the accelerated cooling speed for the working side of the rail head rail mushroom is not mentioned. The accelerated cooling rate for the working side of the rail head is higher than the accelerated cooling rate for the rolling head of the rail head and the non-working side of the rail head of 1.0 ° Gs.
    [0008] Sample No. Temperature Temperature Temperature Speed Cooling Time Cooling Revenue / ° C Return / h Accelerated Cooling 7 ° C / s Final / Initial C / ° C Invention Al 872 3.4 250 308 7.5 A2 908 3.9 245 300 7.0 A3 864 4.5 232 350 8.2 A4 835 3.0 217 337 7.9 A5 811 5.0 200 332 9.0 A6 806 4.1 234 345 8.7 302 1 3 Samples D1 The laminated needle is cooled to ambient temperature 308 7.5 by air-cooling D2 300 7.0 D3 350 8.2 D4 337 7.9 D5 332 9.0 D6 345 8 Table 2: Sample Processing Conditions The bainitic needles obtained in Embodiments A1-A6 and Comparative Samples D1-D6 are tested, and the mechanical properties are shown in Table 3. In this case, Wear tests are performed on a MM200 wear testing machine to test the average weight loss resulting from wear. Samples are taken from the needle rail fungi obtained in Embodiments A1 to A6 and comparative samples D1 to D6. In all wear tests, the lower grinding parts are made of the same material. The test parameters are as follows: Sample size: round and hollow sample 10 mm thick and 36 mm in diameter 15 Test load: 150 kg Slip: 10% Opposite grinding bottom material: steel for wheel with a hardness 280 to 310 HB Rotation speed: 200 rpm 20 Total number of wear cycles: 100,000 cycles The average carbide length, the angle formed by carbides and bainitic ferrite and the area ratio between the carbides and the bainitic ferrite are obtained by the following method: the taking of samples from the needles obtained in the embodiments A1 to A6 and the needles obtained in the comparative samples D1 to D6 and the preparation of samples of films with a thickness of 50 μm, the reduction of the thickness by electrolytic polishing with two jets, and then the indexing and the observation of the morphology of the carbides, and the measurement of the angle formed with the iron bainitic rite under a transmission electron microscope, the selection of carbides at an angle of 40 to 70 ° and a length of 0.05 to 0.5 μm, and the measurement of the carbide area by approximate estimation. Since the morphology of the carbides varies considerably in the different fields of view, in order to guarantee the accuracy of the measurement, the samples obtained from the same sampling position on a needle made of the same material and treated by the same process. should be observed in at least 20 fields of view. Sample No. Tensile Property Property Percentage Length Impact Weight Tag Average Carb Weight Due to Aku / J /% Wear / g (at carb side temperature) / pm Rp0.2 Rm AZ / MPa / MPa /% /% Invention Al 1250 1470 14.5 45 98 0.84 0.41 0.5236 A2 1215 1410 15.0 52 105 0.81 0.06 0.5914 A3 1155 1320 17.0 58 118 0, 72 0.33 0.6255 A4 1205 1450 14.0 44 102 0.65 0.22 0.5651 A5 1280 1510 13.0 39 76 0.92 0.39 0.4624 A6 1345 1590 12.5 40 72 0 , 99 0.28 0.4258 Samples D1 1060 1310 13.0 42 65 N / A / 1.4569 Comparative D2 1025 1280 13.5 44 72 1.6851 D3 980 1220 15.0 52 88 1.7693 D4 1085 1300 12.5 38 69 1.5268 D5 1110 1320 12.0 36 55 1.3264 D6 1115 1340 11.0 36 48 1.2635 Table 3: Mechanical Properties of Samples Needles produced from the steel material described herein invention with the method described in the present invention are described in Embodiments A1 to A6; the needles produced from the steel material described in the present invention with the method of the prior art are described in comparative samples D1 to D6; in the samples according to the invention and the comparative samples, the same method is used to produce the needles with residual heat, and the method is known to those skilled in the art. More specifically, in the samples according to the invention and the comparative samples, a steel material which contains the chemical components mentioned above is melt processed in a converter, refining in a pocket-furnace, vacuum treatment in a ladle, and continuous casting to produce a continuous casting billet with specific cross-sectional dimensions; then, the continuous casting billet is fed into a traveling beam furnace and heated to 1,250 ° C and held at that temperature for 4 hours; then, the steel billet is rolled into a needle with a required cross-section; in this way, the needle with the residual heat described in the present invention is obtained. It can be seen from the comparative results in Tables 1 to 3, under conditions of the same chemical composition and the same melting and rolling process, that the treatment applied to the needle with the residual heat after rolling has an influence. significant on the final properties of the finally obtained bainitic needle, namely: with the method described in the present invention, carbides in the form of bars or in the form of strips having a length of 0.05 to 0.5 pm, the carbides being oriented in a direction at an angle of 40 to 70 ° inclusive with respect to the direction of the main axis of the bainitic ferrite, and representing a percentage of area 1%, precipitates from the bainitic ferrite matrix. The microscopic structure of a sample taken from a bainitic needle produced from the steel material described in Embodiment 1 of the present invention with the method described in the present invention in a field of view under an electron microscope The transmission is shown in Figure 1, in which the bar-shaped or black-banded areas indicate the carbides, while the gray-ash areas indicate the bainitic ferrite. The bainitic needle presented in the present invention not only has excellent toughness, but also has a substantially improved wear resistance under the same conditions, and is therefore advantageous for prolonging the life of the needles, particularly heavy transport railroad connections that are used in difficult operating conditions. Although some preferred embodiments of the present invention are described above, the present invention is not limited to the details of these embodiments. Those skilled in the art can make modifications and variations of the technical method of the present invention without departing from the spirit of the present invention. In addition, it should be noted that the specific technical features described in the above embodiments may be combined into any suitable form, provided that there is no incompatibility. To avoid unnecessary repetition, the possible combinations are not specifically described in the present invention.
    权利要求:
    Claims (6)
    [0001]
    REVENDICATIONS1. Wear-resistant bainitic needle containing bainitic ferrite in the form of flakes in the 30 mm depth range from the surface layer of the rail head (1) to the core part and carbides in the form of dots and or in the form of bars with an average length of 0.05 to 0.5 μm dispersed on the bainitic ferrite, the carbides being oriented in a direction forming an angle of 40 to 70 ° inclusive with respect to the direction of the major axis bainitic ferrite, in which the area ratio between carbides and bainitic ferrite is 0.001 to 1: 100.
    [0002]
    The bainitic needle according to claim 1, wherein the bainitic needle contains 0.15 to 0.30% by weight of C, 1.00 to 1.80% by weight of Si, 1.50 to 2.50% by weight of Mn, 0.50 to 1.00% by weight of Cr, and 0.20 to 0.50% by weight of Mo, and the percentage by total weight of Mn and Cr is 2.20% by weight weight Mn + Cr 3.00% by weight, the remainder being iron and unavoidable impurities.
    [0003]
    A process for producing wear-resistant bainitic needles, comprising: obtaining a needle with residual heat by finishing rolling a steel material, cooling the needle with residual heat up to at a temperature in the temperature range of the austenitic phase domain, and then cooling the rail head (1) of the needle by accelerated cooling, wherein the accelerated cooling speeds for the tread surface ( 101) of the rail head (1) and the non-working side (103) of the rail head (1) are respectively 3.0 to 5.0 ° C / s, and the accelerated cooling speed for the side working pressure (102) of the rail head (1) is higher than the accelerated cooling speeds for the running surface (101) of the rail head (1) and the non-working side (103) of the rail head (1) 1.0 ° C / s, the treatment of the needle obtained at 300 to 350 ° C for 7 to 9 hours when the temperature at the center of the running surface (101) of the rail head (1) falls to 200 to 250 ° C, and then the cooling of the needle at room temperature, to obtain a bainitic needle.
    [0004]
    The production method according to claim 3, wherein the steel material contains 0.15 to 0.30% by weight of C, 1.00 to 1.80% by weight of Si, 1.50 to 2.50. % by weight of Mn, 0.50 to 1.00% by weight of Cr, and 0.20 to 0.50% by weight of Mo, and the percentage by total weight of Mn and Cr is 2.20% by weight Mn + Cr 3.00% by weight, the remainder being iron and unavoidable impurities.
    [0005]
    The production method according to claim 3 or 4, wherein the accelerated cooling medium is selected from at least one of compressed air, an air-water mixture and a gas-oil mixture.
    [0006]
    A bainitic needle produced by the production method according to any one of claims 3 to 5.
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    同族专利:
    公开号 | 公开日
    CN103993237A|2014-08-20|
    CN103993237B|2016-07-06|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    JP2685381B2|1991-12-27|1997-12-03|新日本製鐵株式会社|Surface damage resistant / long life rail|
    CN102839268B|2012-08-28|2014-08-13|攀钢集团攀枝花钢铁研究院有限公司|Heat treatment method of bainite switch rail|
    CN102899471B|2012-10-17|2014-08-06|攀钢集团攀枝花钢铁研究院有限公司|Heat treatment method for bainite steel rail|
    CN103966520B|2014-05-08|2016-07-06|攀钢集团攀枝花钢铁研究院有限公司|A kind of bainite rail containing trace carbon compound and production method thereof|CN105695849B|2016-03-17|2017-05-17|内蒙古科技大学|Method for manufacturing steel rail through nano bainite material containing rare earth La element and steel rail|
    CN106048175B|2016-07-12|2018-03-06|攀钢集团攀枝花钢铁研究院有限公司|A kind of turnout rail and preparation method thereof|
    CN110358904B|2019-05-30|2020-11-03|邯郸钢铁集团有限责任公司|Method for controlling rail shape after on-line heat treatment of steel rail|
    CN112159940A|2020-10-27|2021-01-01|攀钢集团攀枝花钢铁研究院有限公司|Switch steel rail with large supercooling degree and deep hardened layer and preparation method thereof|
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    优先权:
    申请号 | 申请日 | 专利标题
    CN201410218743.6A|CN103993237B|2014-05-22|2014-05-22|A kind of anti abrasive bainite turnout rail and production method thereof|
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