AU2023216732A1 - A method and device for increasing hardness of re-austenitizing zone of hypereutectoid rail joint - Google Patents
A method and device for increasing hardness of re-austenitizing zone of hypereutectoid rail joint Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 61
- 238000010791 quenching Methods 0.000 claims abstract description 95
- 230000000171 quenching effect Effects 0.000 claims abstract description 95
- 238000003466 welding Methods 0.000 claims abstract description 85
- 238000005242 forging Methods 0.000 claims abstract description 28
- 238000009721 upset forging Methods 0.000 claims abstract description 21
- 238000001816 cooling Methods 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 238000004519 manufacturing process Methods 0.000 claims abstract description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 12
- 230000001133 acceleration Effects 0.000 claims description 11
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 10
- 229910052748 manganese Inorganic materials 0.000 claims description 10
- 239000011572 manganese Substances 0.000 claims description 10
- 229910052710 silicon Inorganic materials 0.000 claims description 10
- 239000010703 silicon Substances 0.000 claims description 10
- 239000000126 substance Substances 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 3
- 239000005864 Sulphur Substances 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 239000011651 chromium Substances 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 239000011574 phosphorus Substances 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 3
- 239000010953 base metal Substances 0.000 abstract description 18
- 230000000052 comparative effect Effects 0.000 description 19
- 230000008569 process Effects 0.000 description 12
- 239000000463 material Substances 0.000 description 11
- 238000012360 testing method Methods 0.000 description 11
- 230000009471 action Effects 0.000 description 9
- 238000007689 inspection Methods 0.000 description 9
- 230000002159 abnormal effect Effects 0.000 description 8
- 229910000734 martensite Inorganic materials 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 229910001563 bainite Inorganic materials 0.000 description 5
- 229910001562 pearlite Inorganic materials 0.000 description 4
- 229910001567 cementite Inorganic materials 0.000 description 2
- 238000012733 comparative method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/62—Quenching devices
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
The present invention discloses a method and device for increasing a hardness of
a re-austenitizing zone of a hypereutectoid rail joint, the method comprising: a
pretreatment; subjecting the hypereutectoid rail joint to a flash butt welding
treatment, wherein the welding comprises pre-flash, flash, boost, upset forging
and forging stages; performing a circumferential quenching treatment on the
hypereutectoid rail joint having welding residual heat after welding, wherein the
circumferential quenching treatment comprises respectively injecting
compressed air uniformly into a top part of a rail head, a side part of the rail
head and a lower jaw of the rail head to perform accelerated cooling; and a
post-heat treatment. The ratio of the hardness of the re-austenitizing zone of the
high-strength hypereutectoid rail joint for the heavy-duty railway welded by the
method and device to the hardness of the base metal of the rail is 0.95-1.10,
which can ensure the smoothness of the joint and also easily meet the technical
requirements specified in the standard. It makes full use of the residual heat of
the welded rail joint after welding, increases the hardness of the joint and
effectively ensures the production efficiency.
24
Description
Description
A method and device for increasing hardness of re-austenitizing zone of hypereutectoid rail joint
Technical Field
The present invention relates to the field of rail welding, and more particularly to a method and device for increasing a hardness of a re-austenitizing zone of a hypereutectoid rail joint.
Background Art
In the field of rail production, a rail with a carbon content of more than 0.90% is generally referred to as a hypereutectoid rail. The thickness of cementite sheets and density of cementite in the matrix is increased by a technician to increase the hardness and wear resistance of the rail, i.e., increase the carbon content to obtain a higher hardness. The higher the strength and hardness of the rail, the poorer the welding performance of the rail. The welding joint is a weak link on the railway line. Therefore, the optimization of the welding joint performance of the heavy-duty rail is also the research focus of scholars at home and abroad.
The re-austenitizing zone of rail flash butt welding refers to a region in the rail joint where austenite phase transformation occurs during the welding heating process. This region is also commonly referred to as a normalized zone because the phase change rule during heating and cooling is the same as that during the heat treatment normalizing process. In general, the microstructure, tensile and impact properties of rail flash butt welding re-austenitizing zone are better than those of the base metal. However, for the rail with different chemical composition and supply status, the hardness index of the re-austenitizing zone of the flash weld joint will have different status compared with that of the base metal. Generally, the hardness of rail is mainly determined by the cooling rate. For the metal used in rail with the same starting temperature, the greater the cooling rate in the cooling process, the higher the hardness. If the cooling rate of the re-austenitizing zone after welding is greater than that of the base metal, the hardness of the re-austenitizing zone will be higher than that of the base metal. If the cooling rate of the re-austenitizing zone after welding is less than that of the base metal, the hardness of the re-austenitizing zone will be lower than that of the base metal. Compared with the base metal of the rail, too high or too low hardness of the re-austenitizing zone will affect the smoothness of the joint during service. Also, the abnormal harmful structures such as martensite and bainite will also affect the performance of the rail joint.
Thus, there is a need in the art for an improved method for increasing the hardness of re-austenitizing zone of the hypereutectoid rail joint.
Summary of the Invention
In view of the above, an object of examples of the present invention is to provide a method and device for increasing a hardness of a re-austenitizing zone of a hypereutectoid rail joint, which controls welding parameters and post-welding cooling treatment to increase the hardness of a re-austenitizing zone of a high-strength hypereutectoid rail joint for a heavy-duty railway and effectively guarantee the smoothness of the rail joint.
Based on the above object and in accordance with an aspect of examples of the present invention, a method for increasing a hardness of a re-austenitizing zone of a hypereutectoid rail joint is provided, the method comprising:
(1) subjecting the hypereutectoid rail joint to a pretreatment;
(2) subjecting the hypereutectoid rail joint to a flash butt welding treatment, wherein the welding comprises pre-flash, flash, boost, upset forging and forging stages;
(3) performing a circumferential quenching treatment on the hypereutectoid rail joint having welding residual heat after welding, wherein the circumferential quenching treatment comprises respectively injecting compressed air uniformly into a top part of a rail head, a side part of the rail head and a lower jaw of the rail head to perform accelerated cooling; and
(4) subjecting the hypereutectoid rail joint to a post-heat treatment;
wherein each treatment procedure is connected to form a production line via a conveying roller way; the hypereutectoid rail joint is driven to successively enter each treatment procedures via the conveying roller way; and the quenching length during the circumferential quenching treatment is 10-50 m.
In some embodiments, the welding treatment of step (2) comprises the followings:
the high pressure time of the pre-flash stage is 45s-65s, and the flash speed is 0.1 mm/s-0.6 mm/s;
the low pressure time of the flash stage is 80s-140s, and the flash speed is 0.1 mm/s -0.6 mm/s;
the flash acceleration speed of the boost stage is 0.5 mm/s -2.0 mm/s;
the upset current time in the upset forging stage is 0.1s-2.0s, and the upsetting timing is 1.Os-3.0s;
the rail consumption in the forging stage is 2.0 mm-4.0 mm, the forging time is 1.5s-3.0s, and the average speed is 0.60 mm/s-2.60 mm/s.
In some embodiments, the compressed air at a pressure in the range of 50 kPa-300 kPa is uniformly injected into the top part of the rail head, the side part of the rail head and the lower jaw of the rail head.
In some embodiments, the conveying speed of the conveying roller way is set to 0.2 m/s-2.5 m/s.
In some embodiments, the main chemical composition of the hypereutectoid rail comprises:
carbon with a mass fraction of 0.90%-1.20%, silicon with a mass fraction of 0.10%-1.00%, manganese with a mass fraction of 0.60%-1.50%, phosphorus and sulphur with a mass fraction of not more than 0.020%, chromium with a mass fraction of not more than 0.3%, and vanadium with a mass fraction of not more than 0.01%.
In some embodiments, the hypereutectoid rail has a minimum tensile strength of 1200 MPa and the hypereutectoid rail head has a minimum hardness of 400 HB.
According to another aspect of examples of the present invention, a device for increasing a hardness of a re-austenitizing zone of a hypereutectoid rail joint is provided for circumferential quenching, the device comprising:
a conveying roller way;
a plurality of quenching units arranged in sequence along the direction of the conveying roller way, wherein each of the quenching units comprises an air box of a rail head, first air pipes symmetrically distributed on a side surface of the rail head and second air pipes symmetrically distributed on a lower jaw of the rail head; the longitudinal length of the air box is consistent with that of the air pipe and the distances to the surface of their adjacent rail are the same; and a plurality of air outlets are uniformly distributed on the air box and the air pipe so as to blow compressed air to the rail joint.
In some embodiments, each of the quenching units comprises one air box of the rail head, two first air pipes symmetrically distributed on the side of the rail head and two second air pipes symmetrically distributed on the lower jaw of the rail head; and each of the quenching units independently regulates the pressure of the compressed air.
In some embodiments, the compressed air is at a pressure of 50 kPa-300 kPa prior to entering a quenching device.
In some embodiments, the quenching device composed of the plurality of quenching units has a total length of 10 m-50 m; the air box has a width of > 70 mm, the air box and the air pipe each has a length of > 150 mm; the air pipe has a diameter of ©25 mm-30 mm; a distance between the air box and the air pipe and the surface of their adjacent rail is 20 mm-40 mm; the air outlet has a diameter of 11 mm-43 mm; and a spacing between the air outlets is 5 mm-15 mm.
The present invention has the following advantageous technical effects:
The method of the present invention is achieved by a rail mobile flash butt welding machine, and the welding process mainly comprises five main stages, i.e., pre-flash, flash, boost, upset forging and forging. After the flash butt welding process is finished, a circumferential air quenching treatment is performed on the joint by a special fixed on-line quenching device. The ratio of the hardness of the re-austenitizing zone of the high-strength hypereutectoid rail joint for the heavy-duty railway welded by the method and device to the hardness of the base metal of the rail is 0.95-1.10, which can ensure the smoothness of the joint and also easily meet the technical requirements specified in the standard. It makes full use of the residual heat of the welded rail joint after welding, not only increases the hardness of the joint, but also effectively ensures the production efficiency.
Brief Description of the Drawings
In order to more clearly describe the technical solutions in the examples of the invention or the prior art, the drawings to be used in the description of the examples or the prior art will be briefly introduced below. It will be apparent to those skilled in the art that the drawings in the following description are only some of the invention, and that other drawings may be obtained from the drawings without any creative works.
Fig. 1 is a flow diagram of an example of a method for increasing a hardness of a re-austenitizing zone of a hypereutectoid rail joint according to the present invention;
Fig. 2 is a schematic view of an example of a quenching unit according to the present invention;
Fig. 3 is a schematic view of a re-austenitizing zone for a rail joint according to the present invention.
Detailed Description of the Invention
In order that the objects, technical solutions, and advantages of the present invention will become more apparent, a more particular description of the invention will be rendered by reference to the examples and appended drawings.
The terms "comprising" and "having", and any variation thereof, in the description and claims of the present invention and in the preceding description of the drawings are intended to cover a non-exclusive inclusion. The terms "first", "second", and the like in the description and in the claims of the invention or in the above-described drawings are used for distinguishing between different objects and not for describing a particular sequence. "A plurality of' means two or more unless specifically limited otherwise.
Furthermore, reference herein to "an example" means that a particular feature, structure, or characteristic described in connection with the example may be included in at least one example of the invention. The appearances of the phrase in various places in the description are not necessarily all referring to the same example, nor are separate or alternative examples mutually exclusive of other examples. It should be expressly and implicitly understood by one of ordinary skill in the art that the examples described herein may be combined with other examples.
As shown in Fig. 1 which is a flow diagram of an example of a method for increasing a hardness of a re-austenitizing zone of a hypereutectoid rail joint according to the present invention, the method includes:
(1) subjecting the hypereutectoid rail joint to a pretreatment;
(2) subjecting the hypereutectoid rail joint to a flash butt welding treatment, wherein the welding comprises pre-flash, flash, boost, upset forging and forging stages;
(3) performing a circumferential quenching treatment on the hypereutectoid rail joint having welding residual heat after welding, wherein the circumferential quenching treatment comprises respectively injecting compressed air uniformly into a top part of a rail head, a side part of the rail head and a lower jaw of the rail head to perform accelerated cooling; and
(4) subjecting the hypereutectoid rail joint to a post-heat treatment;
wherein each treatment procedure is connected to form a production line via a conveying roller way; the hypereutectoid rail joint is driven to successively enter each treatment procedures via the conveying roller way; and the quenching length during the circumferential quenching treatment is 10-50 m.
Further, the above-mentioned high-strength hypereutectoid rail for the heavy-duty railway is characterized in that the main chemical composition of the rail includes carbon with a mass fraction of 0.90%-1.20%, silicon with a mass fraction of 0.10%-1.00%, manganese with a mass fraction of 0.60%-1.50%, phosphorus and sulphur with a mass fraction of not more than 0.020%, chromium with a mass fraction of not more than 0.3%, and vanadium with a mass fraction of not more than 0.01%. The rail has a minimum tensile strength of 1200 MPa, and the rail head has a minimum hardness of 400 HB.
Further, the front-end procedure and the rear-end procedure in the method of the present invention are conventional procedures in rail joint welding. Therefore, these will not be further explained in the present invention. For the continuous flash butt welding in Step (2), the flash process is mainly achieved by pre-flash, flash and boost. The flash process is smooth and continuous without interruption. In order to achieve the object of increasing the hardness of the re-austenitizing zone of hypereutectoid rail joints, the heat input during the welding process and the cooling rate during the joint cooling process should be strictly controlled. The joint is subjected to the circumferential quenching treatment of Step (3) after the welding is completed.
Further, the basic function of the pre-flash stage described above is to flatten and clean the section of the rail to be welded by flash burst, providing the advantageous conditions of relatively uniform flatness and basic heat for the subsequent flash. For the purpose of controlling the heat input, it is mainly necessary to control the high pressure time and flash speed in this stage. The high pressure time of the pre-flash stage is 45s-65s, and the flash speed is 0.1 mm/s-0.6 mm/s.
Further, the flash stage described above has the main function of flattening and cleaning the section of the rail to be welded by flash burst, providing the advantageous conditions of relatively uniform flatness and basic heat for the subsequent flash. For the purpose of controlling the heat input, it is mainly necessary to control the low pressure time and the flash speed in this stage. The low pressure time of the flash stage is 80s-140s, and the flash speed is 0.1 mm/s -0.6 mm/s.
Further, the above-mentioned boost stage mainly functions to form a protective atmosphere for preventing oxidation of the end face in the whole welding zone, and finally to form a suitable temperature field distribution for providing conditions for upset forging. For the purpose of controlling the heat input, it is mainly necessary to control the speed of flash acceleration in this stage. The flash acceleration speed in the boost stage is 0.5 mm/s-2.0 mm/s.
Further, the main function of the upset forging stage described above is to cause interatomic bonding of the rail to be welded in a high temperature plastic state. For the purpose of controlling heat input, it is mainly necessary to control the upset current time and upset forging timing at this stage. The upset current time is 0.1s-2.0s, and the upset forging timing is1.s-3.0s.
Further, the main function of the forging stage described above is to continuously apply load to the rail joint during the metal crystallization of the joint after rail upset forging. The rail consumption in the forging stage is 2.0 mm-4.0 mm, the forging time is 1.5s-3.0s, and the average speed is 0.60 mm/s-2.60 mm/s.
Further, the above-mentioned circumferential quenching treatment is a process in which the rail passes through a special quenching device along the longitudinal direction of the rail at a certain running speed; and under the action of compressed air with a certain pressure, the welding joint of the rail with welding residual heat is accelerated to cool. Specifically, the conveying speed of the conveying roller way is set to be 0.2 m/s-2.5 m/s. The compressed air at a pressure in the range of 50 kPa-300 kPa is uniformly injected into the top part of the rail head, the side part of the rail head and the lower jaw of the rail head by the quenching device.
According to a further aspect of the present invention, a device for increasing a hardness of a re-austenitizing zone of a hypereutectoid rail joint used in the method described above is provided. The device is a fixed on-line quenching device for circumferential quenching and in tight contact with the outlet end of a welding machine. The device includes:
a conveying roller way;
a plurality of quenching units arranged in sequence along the direction of the conveying roller way, wherein each of the quenching units comprises an air box of a rail head, first air pipes symmetrically distributed on a side surface of the rail head and second air pipes symmetrically distributed on a lower jaw of the rail head; the longitudinal length of the air box is consistent with that of the air pipe and the distances to the surface of their adjacent rail are the same; and a plurality of air outlets are uniformly distributed on the air box and the air pipe so as to blow compressed air to the rail joint.
In some embodiments, each of the quenching units comprises one air box of a rail head, two first air pipes symmetrically distributed on the side of the rail head and two second air pipes symmetrically distributed on the lower jaw of the rail head; and each of the quenching units independently regulates the pressure of the compressed air. Further, the compressed air is at a pressure of 50 kPa-300 kPa prior to entering a quenching device.
In some embodiments, the quenching device composed of the plurality of quenching units has a total length of 10 m-50 m; the air box has a width of > 70 mm, the air box and the air pipe each has a length of > 150 mm; the air pipe has a diameter of ©25 mm-30 mm; a distance between the air box and the air pipe and the surface of their adjacent rail is 20 mm-40 mm; the air outlet has a diameter of 11 mm-43 mm; and a spacing between the air outlets is 5 mm-15 mm.
The device of the present invention is mainly applied to the quenching process in the above-mentioned method. The welded rail joint is transferred to a fixed quenching device via a conveying roller way, and is driven by the conveying roller way to successively pass through a plurality of quenching units so as to continuously perform quenching. On the one hand, the cooling effect of the rail joint is better, and on the other hand, the working efficiency of the whole welding production line is higher.
Specific examples of the invention are further illustrated below with reference to specific examples.
Example 1
In the rail material for testing in this example, the mass fraction of carbon was 0.91%, the mass fraction of silicon was 0.46%, the mass fraction of manganese was 0.81%, the tensile strength of the rail was 1200 MPa-1300 MPa, and the hardness of the rail head was 405 HB-415 HB. The high pressure time of the pre-flash stage during continuous flash butt welding was 45s, and the flash speed was 0.1 mm/s. The low pressure time of the flash stage was 80s, and the flash speed was 0.1 mm/s. The speed of flash acceleration during the boost stage was 0.5 mm/s. The upset current time during the upsetting stage was 0.1s, and the upset forging timing was 1.0s. The rail consumption during the forging stage was 2.0 mm, the forging time was 1.5s, and the average speed was 0.60 mm/s. After the welding was finished, the rail passed through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a certain pressure, the welding joint of the rail with welding residual heat was accelerated to cool. The rail running speed was 0.2m/s. The effective quenching total length of the residual heat quenching device at the rear end of the welding procedure was 40 m. The length of the air box and the air pipe of the independent quenching unit was 160 mm. The width of the air box on the top surface of the rail was 72 mm. The inner diameter of the air pipe was I30 mm. The distance of the air box and the air pipe to the surface of their adjacent rail was 20 mm, and several air outlets were uniformly distributed. The diameter of the air outlet was 13 mm, and the distance between the air outlets was 8 mm. The pressure of the compressed air before entering the quenching device was 300 kPa. After inspection, the ratio of the hardness of the re-austenitizing zone of the rail joint to the hardness of the rail base metal in this example was 0.95, which effectively guaranteed the smoothness of the joint, and the technical indicators met the standard provisions. Meanwhile, the microstructure of the standard test part in the joint was pearlite, without such abnormal structures as martensite or bainite. The joints and performances thereof met the standard technical requirements.
Example 2
In the rail material for testing in this example, the mass fraction of carbon was 1.18%, the mass fraction of silicon was 0.56%, the mass fraction of manganese was 0.78%, the tensile strength of the rail was 1380 MPa-1480 MPa, and the hardness of the rail head was 425 HB-450 HB. The high pressure time of the pre-flash stage during continuous flash butt welding was 65s, and the flash speed was 0.6 mm/s. The low pressure time of the flash stage was 140s, and the flash speed was 0.6 mm/s. The speed of flash acceleration during the boost stage was 2.0 mm/s. The upset current time during the upsetting stage was 2.0s, and the upset forging timing was 3.0s. The rail consumption during the forging stage was 4.0 mm, the forging time was 3.0s, and the average speed was 2.60 mm/s. After the welding was finished, the rail passed through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a certain pressure, the welding joint of the rail with welding residual heat was accelerated to cool. The rail running speed was 2.0 m/s. The effective quenching total length of the residual heat quenching device at the rear end of the welding procedure was 20 m. The length of the air box and the air pipe of the independent quenching unit was 150 mm. The width of the air box on the top surface of the rail was 70 mm. The inner diameter of the air pipe was ©25 mm. The distance of the air box and the air pipe to the surface of their adjacent rail was 30 mm, and several air outlets were uniformly distributed. The diameter of the air outlet was ©2 mm, and the distance between the air outlets was 10 mm. The pressure of the compressed air before entering the quenching device was 100 kPa. After inspection, the ratio of the hardness of the re-austenitizing zone of the rail joint to the hardness of the rail base metal in this example was 1.02, which effectively guaranteed the smoothness of the joint, and the technical indicators met the standard provisions. Meanwhile, the microstructure of the standard test part in the joint was pearlite, without such abnormal structures as martensite or bainite. The joints and performances thereof met the standard technical requirements.
Example 3
In the rail material for testing in this example, the mass fraction of carbon was 1.10%, the mass fraction of silicon was 0.73%, the mass fraction of manganese was 1.10%, the tensile strength of the rail was 1300 MPa-1420 MPa, and the hardness of the rail head was 415 HB-440 HB. The high pressure time of the pre-flash stage during continuous flash butt welding was 50s, and the flash speed was 0.4 mm/s. The low pressure time of the flash stage was 100s, and the flash speed was 0.5 mm/s. The speed of flash acceleration during the boost stage was 1.7 mm/s. The upset current time during the upsetting stage was 1.2s, and the upset forging timing was 1.1s. The rail consumption during the forging stage was 2.4 mm, the forging time was 2.0s, and the average speed was 1.2 mm/s. After the welding was finished, the rail passed through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a certain pressure, the welding joint of the rail with welding residual heat was accelerated to cool. The rail running speed was 1.0 m/s. The effective quenching total length of the residual heat quenching device at the rear end of the welding procedure was 35m. The length of the air box and the air pipe of the independent quenching unit was 155mm. The width of the air box on the top surface of the rail was 72mm. The inner diameter of the air pipe was ©25 mm. The distance of the air box and the air pipe to the surface of their adjacent rail was 30 mm, and several air outlets were uniformly distributed. The diameter of the air outlet was ©2 mm, and the distance between the air outlets was 10 mm. The pressure of the compressed air before entering the quenching device was 200 kPa. After inspection, the ratio of the hardness of the re-austenitizing zone of the rail joint to the hardness of the rail base metal in this example was 0.98, which effectively guaranteed the smoothness of the joint, and the technical indicators met the standard provisions.
Meanwhile, the microstructure of the standard test part in the joint was pearlite, without such abnormal structures as martensite or bainite. The joints and performances thereof met the standard technical requirements.
Comparative Example 1
In the rail material for testing in this comparative example, the mass fraction of carbon was 1.10%, the mass fraction of silicon was 0.73%, the mass fraction of manganese was 1.10%, the tensile strength of the rail was 1300 MPa-1420 MPa, and the hardness of the rail head was 415 HB-440 HB. The high pressure time of the pre-flash stage during continuous flash butt welding was 50s, and the flash speed was 0.4 mm/s. The low pressure time of the flash stage was 100s, and the flash speed was 0.5 mm/s. The speed of flash acceleration during the boost stage was 1.7 mm/s. The upset current time during the upsetting stage was 1.2s, and the upset forging timing was 1.1s. The rail consumption during the forging stage was 2.4 mm, the forging time was 2.0s, and the average speed was 1.2 mm/s. After the welding was finished, the rail passed through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a certain pressure, the welding joint of the rail with welding residual heat was accelerated to cool. The rail running speed was 3.0 m/s. The effective quenching total length of the residual heat quenching device at the rear end of the welding procedure was 8m. The length of the air box and the air pipe of the independent quenching unit was 150 mm. The width of the air box on the top surface of the rail was 70 mm. The inner diameter of the air pipe was ©25 mm. The distance of the air box and the air pipe to the surface of their adjacent rail was 30 mm, and several air outlets were uniformly distributed. The diameter of the air outlet was ©2 mm, and the distance between the air outlets was 20mm. The pressure of the compressed air before entering the quenching device was 40 kPa. After inspection, the ratio of the hardness of the re-austenitizing zone of the rail joint to the hardness of the rail base metal in this comparative example was 0.75, which fails to meet the standard requirements. The main difference between this comparative example and Example 3 lied in the post-weld quenching device and quenching method. After the welding was completed, the rail passed through the quenching device at a speed exceeding the running speed of the patent claim. The length of the quenching device was short and the pressure of compressed air was small, resulting in that the cooling speed of the joint of the rail was too slow to increase the hardness of the re-austenitizing zone of the joint. That is, in the case where the material of the rail was the same as the welding method, the method in the comparative example cannot achieve the desired effect.
Comparative Example 2
In the rail material for testing in this comparative example, the mass fraction of carbon was 1.10%, the mass fraction of silicon was 0.73%, the mass fraction of manganese was 1.10%, the tensile strength of the rail was 1300 MPa-1420 MPa, and the hardness of the rail head was 415 HB-440 HB. The high pressure time of the pre-flash stage during continuous flash butt welding was 50s, and the flash speed was 0.4 mm/s. The low pressure time of the flash stage was 100s, and the flash speed was 0.5 mm/s. The speed of flash acceleration during the boost stage was 1.7 mm/s. The upset current time during the upsetting stage was 1.2s, and the upset forging timing was 1.1s. The rail consumption during the forging stage was 2.4 mm, the forging time was 2.0s, and the average speed was 1.2 mm/s. After the welding was finished, the rail passed through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a certain pressure, the welding joint of the rail with welding residual heat was accelerated to cool. The rail running speed was 1.0 m/s. The effective quenching total length of the residual heat quenching device at the rear end of the welding procedure was 60m. The length of the air box and the air pipe of the independent quenching unit was 150 mm.
The width of the air box on the top surface of the rail was 70 mm. The inner diameter of the air pipe was 130 mm. The distance of the air box and the air pipe to the surface of their adjacent rail was 30 mm, and several air outlets were uniformly distributed. The diameter of the air outlet was ©2 mm, and the distance between the air outlets was 15 mm. The pressure of the compressed air before entering the quenching device was 350 kPa. After inspection, the ratio of the hardness of the re-austenitizing zone of the rail joint to the hardness of the rail base metal in this comparative example was 1.3. The local hardness of the joint was too high, so that the joint smoothness cannot be guaranteed, and the technical indicators do not meet the standards. At the same time, an abnormal martensite structure was detected at the standard inspection position in the joint. The main difference between this comparative example and Example 3 lied in the post-weld quenching device and quenching method. After welding, the rail passed through the quenching device at a certain speed. The quenching device was long and the compressed air pressure was large, resulting in the cooling speed of the rail joint was too fast, so that the hardness of the re-austenitizing zone of the joint was increased beyond the range required by the standard, and the microstructure also appears abnormal. That is, in the case where the material of the rail was the same as the welding method, the method in the comparative example cannot achieve the desired effect.
Comparative Example 3
In the rail material for testing in this comparative example, the mass fraction of carbon was 1.10%, the mass fraction of silicon was 0.73%, the mass fraction of manganese was 1.10%, the tensile strength of the rail was 1300 MPa-1420 MPa, and the hardness of the rail head was 415 HB-440 HB. The high pressure time of the pre-flash stage during continuous flash butt welding was 70s, and the flash speed was 0.1 mm/s. The low pressure time of the flash stage was 160s, and the flash speed was 0.1 mm/s. The speed of flash acceleration during the boost stage was 0.5 mm/s. The upset current time during the upsetting stage was 0.1s, and the upset forging timing was 1.0s. The rail consumption during the forging stage was 1.0 mm, the forging time was 1.2s, and the average speed was 0.40 mm/s. After the welding was finished, the rail passed through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a certain pressure, the welding joint of the rail with welding residual heat was accelerated to cool. The rail running speed was 1.0 m/s. The effective quenching total length of the residual heat quenching device at the rear end of the welding procedure was 35m. The length of the air box and the air pipe of the independent quenching unit was 155 mm. The width of the air box on the top surface of the rail was 72 mm. The inner diameter of the air pipe was ©25 mm. The distance of the air box and the air pipe to the surface of their adjacent rail was 30 mm, and several air outlets were uniformly distributed. The diameter of the air outlet was ©2 mm, and the distance between the air outlets was 10 mm. The pressure of the compressed air before entering the quenching device was 200 kPa. After inspection, the ratio of the hardness of the re-austenitizing zone of the rail joint to the hardness of the rail base metal in this comparative example was 1.25. The local hardness of the joint was too high, so that the joint smoothness cannot be guaranteed, and the technical indicators do not meet the standards. At the same time, an abnormal martensite structure was detected at the standard inspection position in the joint. The main difference between this comparative example and Example 3 lied in the welding method. The high pressure time, low pressure time and welding heat input amount used in the comparative example were higher than those in the present patent claim. The rail consumption was reduced and the heat loss was reduced by using a flash speed lower than that in each stage of this patent claim. When the consumption of rail in upset forging and forging was lower than that in the patent claim, the consumption of rail was reduced and the heat loss was less. In the subsequent air quenching process, the cooling rate was too fast, and the ratio of the hardness of the re-austenization zone of the joint to the hardness of the rail base metal does not met the standard technical requirements. Under the condition that the rail materials were the same, this comparative method cannot achieve the desired effect.
Comparative Example 4
In the rail material for testing in this comparative example, the mass fraction of carbon was 1.10%, the mass fraction of silicon was 0.73%, the mass fraction of manganese was 1.10%, the tensile strength of the rail was 1300 MPa-1420 MPa, and the hardness of the rail head was 415 HB-440 HB. The high pressure time of the pre-flash stage during continuous flash butt welding was 40s, and the flash speed was 0.8 mm/s. The low pressure time of the flash stage was 50s, and the flash speed was 1.0 mm/s. The speed of flash acceleration during the boost stage was 2.1 mm/s. The upset current time during the upsetting stage was 0.1s, and the upset forging timing was 1.0s. The rail consumption during the forging stage was 5.0 mm, the forging time was 1.0s, and the average speed was 0.60 mm/s. After the welding was finished, the rail passed through a special quenching device along the longitudinal direction of the rail at a certain running speed. Under the action of compressed air with a certain pressure, the welding joint of the rail with welding residual heat was accelerated to cool. The rail running speed was 1.Om/s. The effective quenching total length of the residual heat quenching device at the rear end of the welding procedure was 35m. The length of the air box and the air pipe of the independent quenching unit was 155 mm. The width of the air box on the top surface of the rail was 72 mm. The inner diameter of the air pipe was ©25 mm. The distance of the air box and the air pipe to the surface of their adjacent rail was 30 mm, and several air outlets were uniformly distributed. The diameter of the air outlet was ©2 mm, and the distance between the air outlets was 10 mm. The pressure of the compressed air before entering the quenching device was 200 kPa. After inspection, the ratio of the hardness of the re-austenitizing zone of the rail joint to the hardness of the rail base metal in this comparative example was 0.78, which effectively guarantees the smoothness of the joint, and the technical indicators met the standard provisions. Meanwhile, the microstructure of the standard test part in the joint was pearlite, without such abnormal structures as martensite or bainite. The high pressure time, the low pressure time, and the welding heat input amount used in the comparative example were lower than those in the patent claims. When the flash speed was higher than that in each stage of this patent claim, the rail consumption was increased and the heat loss was increased. The consumption of rail in the upset forging and forging was higher than that in this patent claim, the consumption of rail was increased, and the heat loss was large. In the subsequent air quenching process, the cooling rate was too slow, and the ratio of the hardness of the re-austenitizing region of the joint to the hardness of the rail base metal does not met the standard technical requirements. Under the condition that the rail materials were the same, this comparative method cannot achieve the desired effect.
The foregoing is the exemplary examples of the present disclosure. It should be noted that various changes and modifications can be made herein without departing from the scope of the disclosed examples as defined by the appended claims. The functions, steps, and/or actions of the method claims in accordance with the disclosed examples described herein need not be performed in any particular order. Although elements disclosed in the examples of the present invention can be described or required in individual forms, it can also be interpreted as a plurality unless explicitly limited to the singular.
It will be understood that, as used herein, the singular forms "a" or "an" 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 above-described examples of the present invention have been disclosed for the purpose of illustration only, and are not intended to represent the advantages and disadvantages of the examples.
Those of ordinary skill in the art will appreciate that the above discussion of any examples is intended to be exemplary only, and is not intended to suggest that the scope of the disclosed examples (including the claims) should be limited to these examples. Combinations of features in the above examples or in different examples are also possible within the idea of examples of the invention, and many other variations of different aspects of the examples of the invention as described above are not provided in detail for the sake of clarity. Therefore, any omission, modification, equivalent substitution or improvement made within the spirit and principle of the example of the invention shall be included in the scope of protection of the example of the invention.
Claims (10)
1. A method for increasing a hardness of a re-austenitizing zone of a hypereutectoid rail joint, characterized by comprising:
(1) subjecting the hypereutectoid rail joint to a pretreatment;
(2) subjecting the hypereutectoid rail joint to a flash butt welding treatment, wherein the welding comprises pre-flash, flash, boost, upset forging and forging stages;
(3) performing a circumferential quenching treatment on the hypereutectoid rail joint having welding residual heat after welding, wherein the circumferential quenching treatment comprises respectively injecting compressed air uniformly into a top part of a rail head, a side part of the rail head and a lower jaw of the rail head to perform accelerated cooling; and
(4) subjecting the hypereutectoid rail joint to a post-heat treatment;
wherein each treatment procedure is connected to form a production line via a conveying roller way; the hypereutectoid rail joint is driven to successively enter each treatment procedures via the conveying roller way; and the quenching length during the circumferential quenching treatment is 10-50 m.
2. The method for increasing the hardness of the re-austenitizing zone of the hypereutectoid rail joint according to claim 1, characterized in that the welding treatment of step (2) comprises the followings:
the high pressure time of the pre-flash stage is 45s-65s, and the flash speed is 0.1 mm/s-0.6 mm/s;
the low pressure time of the flash stage is 80s-140s, and the flash speed is 0.1 mm/s -0.6 mm/s;
the flash acceleration speed of the boost stage is 0.5 mm/s -2.0 mm/s;
the upset current time in the upset forging stage is 0.1s-2.0s, and the upsetting timing is 1.Os-3.0s; the rail consumption in the forging stage is 2.0 mm-4.0 mm, the forging time is 1.5s-3.0s, and the average speed is 0.60 mm/s-2.60 mm/s.
3. The method for increasing the hardness of the re-austenitizing zone of the hypereutectoid rail joint according to claim 1, characterized in that the compressed air at a pressure in the range of 50 kPa-300 kPa is uniformly injected into the top part of the rail head, the side part of the rail head and the lower jaw of the rail head.
4. The method for increasing the hardness of the re-austenitizing zone of the hypereutectoid rail joint according to according to claim 1, characterized in that the conveying speed of the conveying roller way is set to 0.2 m/s-2.5 m/s.
5. The method for increasing the hardness of the re-austenitizing zone of the hypereutectoid rail joint according to according to claim 1, characterized in that the main chemical composition of the hypereutectoid rail comprises:
carbon with a mass fraction of 0.90%-1.20%, silicon with a mass fraction of 0.10%-1.00%, manganese with a mass fraction of 0.60%-1.50%, phosphorus and sulphur with a mass fraction of not more than 0.020%, chromium with a mass fraction of not more than 0.3%, and vanadium with a mass fraction of not more than 0.010%.
6. The method for increasing the hardness of the re-austenitizing zone of the hypereutectoid rail joint according to according to claim 1, characterized in that the hypereutectoid rail has a minimum tensile strength of 1200 MPa and the hypereutectoid rail head has a minimum hardness of 400 HB.
7. A device for increasing a hardness of a re-austenitizing zone of a hypereutectoid rail joint used in the method of any one of the preceding claims, the device being used for a circumferential quenching treatment, characterized in that the device comprises: a conveying roller way; a plurality of quenching units arranged in sequence along the direction of the conveying roller way, wherein each of the quenching units comprises an air box of a rail head, first air pipes symmetrically distributed on a side surface of the rail head and second air pipes symmetrically distributed on a lower jaw of the rail head; the longitudinal length of the air box is consistent with that of the air pipe and the distances to the surface of their adjacent rail are the same; and a plurality of air outlets are uniformly distributed on the air box and the air pipe so as to blow compressed air to the rail joint.
8. The device for increasing the hardness of the re-austenitizing zone of the hypereutectoid rail joint according to claim 7, characterized in that each of the quenching units comprises one air box of the rail head, two first air pipes symmetrically distributed on the side of the rail head and two second air pipes symmetrically distributed on the lower jaw of the rail head; and each of the quenching units independently regulates the pressure of the compressed air.
9. The device for increasing the hardness of the re-austenitizing zone of the hypereutectoid rail joint according to claim 8 characterized in that the compressed air is at a pressure of 50 kPa-300 kPa prior to entering a quenching device.
10. The device for increasing the hardness of the re-austenitizing zone of the hypereutectoid rail joint according to claim 7, characterized in that the quenching device composed of the plurality of quenching units has a total length of 10 m-50 m; the air box has a width of > 70 mm, the air box and the air pipe each has a length of > 150 mm; the air pipe has a diameter of ©25 mm-©30 mm; a distance between the air box and the air pipe and the surface of their adjacent rail is 20 mm-40 mm; the air outlet has a diameter of Il mm-©3 mm; and a spacing between the air outlets is 5 mm-15 mm.
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| CN202211368264.3A CN115679079A (en) | 2022-11-03 | 2022-11-03 | Method and device for improving hardness of hypereutectoid steel rail joint re-austenitizing area |
| CN202211368264.3 | 2022-11-03 | ||
| PCT/CN2023/093531 WO2024093182A1 (en) | 2022-11-03 | 2023-05-11 | Method and device for improving hardness of reaustenitizing area of hypereutectoid steel rail joint |
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| CN102365377B (en) * | 2009-03-30 | 2014-03-05 | 新日铁住金株式会社 | Method of cooling welded rail section, device for cooling welded rail section, and welded rail joint |
| CN107520529B (en) * | 2017-08-31 | 2019-10-11 | 攀钢集团研究院有限公司 | The method of the mobile Flash Butt Welding of 136RE+SS heat-treated rail |
| CN109055708B (en) * | 2018-08-20 | 2020-07-21 | 攀钢集团攀枝花钢铁研究院有限公司 | Heat treatment method for weld joint of eutectoid steel rail and hypereutectoid steel rail |
| CN113414480B (en) * | 2021-07-23 | 2022-10-11 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for eliminating overburning defect of mobile flash welding head of hypereutectoid steel rail of 75kg/m |
| CN115679079A (en) * | 2022-11-03 | 2023-02-03 | 攀钢集团攀枝花钢铁研究院有限公司 | Method and device for improving hardness of hypereutectoid steel rail joint re-austenitizing area |
| CN115488484B (en) * | 2022-11-03 | 2024-03-08 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for improving hardness of normalizing region of flash welding head of hypereutectoid steel rail |
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