CN115233503A - Medium-strength steel rail with high yield strength and production method thereof - Google Patents
Medium-strength steel rail with high yield strength and production method thereof Download PDFInfo
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- CN115233503A CN115233503A CN202210941427.6A CN202210941427A CN115233503A CN 115233503 A CN115233503 A CN 115233503A CN 202210941427 A CN202210941427 A CN 202210941427A CN 115233503 A CN115233503 A CN 115233503A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 149
- 239000010959 steel Substances 0.000 title claims abstract description 149
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 33
- 238000010438 heat treatment Methods 0.000 claims abstract description 31
- 238000001816 cooling Methods 0.000 claims description 62
- 238000005096 rolling process Methods 0.000 claims description 11
- 239000000126 substance Substances 0.000 claims description 11
- 239000000203 mixture Substances 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 238000003723 Smelting Methods 0.000 claims description 6
- 239000003595 mist Substances 0.000 claims description 6
- 239000002826 coolant Substances 0.000 claims description 5
- 238000012545 processing Methods 0.000 claims description 4
- 238000007670 refining Methods 0.000 claims description 4
- 238000009489 vacuum treatment Methods 0.000 claims description 4
- 238000009749 continuous casting Methods 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 20
- 230000008569 process Effects 0.000 abstract description 14
- 229910045601 alloy Inorganic materials 0.000 abstract description 4
- 239000000956 alloy Substances 0.000 abstract description 4
- 229910001562 pearlite Inorganic materials 0.000 description 14
- 239000012535 impurity Substances 0.000 description 7
- 229910052717 sulfur Inorganic materials 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 229910052804 chromium Inorganic materials 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 230000009466 transformation Effects 0.000 description 5
- 229910052748 manganese Inorganic materials 0.000 description 4
- 230000006872 improvement Effects 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 239000007769 metal material Substances 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 2
- 229910001563 bainite Inorganic materials 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- 238000007546 Brinell hardness test Methods 0.000 description 1
- 238000007550 Rockwell hardness test Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000011534 incubation Methods 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
Classifications
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01B—PERMANENT WAY; PERMANENT-WAY TOOLS; MACHINES FOR MAKING RAILWAYS OF ALL KINDS
- E01B5/00—Rails; Guard rails; Distance-keeping means for them
- E01B5/02—Rails
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
- B21B1/085—Rail sections
-
- 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
- C21D11/00—Process control or regulation for heat treatments
- C21D11/005—Process control or regulation for heat treatments for cooling
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- 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
- C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Metallurgy (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Structural Engineering (AREA)
- Civil Engineering (AREA)
- Architecture (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
The invention belongs to the field of steel rail production, and particularly relates to a medium-strength steel rail with high yield strength and a production method thereof. The invention relates to a medium-strength steel rail with high yield strength, which comprises the following components: the yield strength is more than or equal to 820MPa, the tensile strength is 1200-1300MPa, and the elongation is more than or equal to 10%. The medium-strength steel rail related to the invention obtains high yield strength through an on-line heat treatment process design under the condition that various alloy elements are not added, can effectively reduce the probability of contact fatigue damage in the use of a passenger-cargo mixed transportation line, can effectively improve the service performance and service life of the steel rail, and improves the running safety of a train.
Description
Technical Field
The invention relates to the field of steel rail production, in particular to a medium-strength steel rail with high yield strength and a production method thereof.
Background
In China, railways are in a high-speed development stage, passenger dedicated lines and heavy-duty freight lines are greatly increased, but in order to realize comprehensive development of the railway field, the existing passenger-cargo mixed transportation lines are also upgraded and reformed, and the requirements on freight transportation volume, passenger transportation safety and overall operation stability are improved. The trend causes the surface contact fatigue damage conditions such as stripping and block dropping of the steel rail to be aggravated, the service performance and service life of the steel rail are seriously influenced, and the railway transportation efficiency and safety are difficult to guarantee.
At present, in order to improve the service performance and service life of a steel rail, a passenger-cargo mixed transportation line and a freight special line at home and abroad mainly adopt a high-performance heat-treated pearlite steel rail, and the tensile strength and hardness of the steel rail are improved in an online or offline heat treatment mode to achieve the purposes of improving the wear resistance and the contact fatigue resistance, but the traditional medium-strength pearlite heat-treated steel rail rarely considers the improvement of the plastic deformation resistance of the steel rail caused by high yield strength and the effect of fundamentally reducing the surface contact fatigue damage, and the high-strength heat-treated pearlite steel rail with high yield strength cannot consider the safety reduction caused by the problems of increased wheel abrasion and the like caused by the overhigh tensile strength and hardness when being applied to the passenger-cargo mixed transportation line.
Patent CN 106086622A discloses a passenger-cargo mixed use steel rail and a production method thereof in a passenger-cargo mixed use steel rail heat treatment production method and an obtained steel rail, wherein the steel rail comprises the following chemical components in percentage by weight: 0.71 to 0.82 percent of C, 0.13 to 0.60 percent of Si, 0.65 to 1.25 percent of Mn, 0.05 to 0.25 percent of Cr, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, less than or equal to 0.1 percent of Al, and the balance of Fe and inevitable impurities. The method adopts an online heat treatment method, and sequentially carries out accelerated cooling, slow cooling and air cooling on the center of a rail head tread, two sides of a rail head and the center of a rail bottom of a steel rail, wherein the start cooling temperature of the accelerated cooling is 650-950 ℃, the cooling speed is 2.5-7 ℃/s, the final cooling temperature is 400-630 ℃, the cooling speed of the slow cooling is 0.1-1.5 ℃/s, and the final cooling temperature is 180-300 ℃; in addition, the rail bottom of the steel rail needs to be accelerated and cooled in the production method of the steel rail, the requirement on equipment is high, and the production method is complex.
Patent CN 104988405A discloses a passenger-cargo mixed steel rail and a production method and application thereof, and a preparation method thereof, wherein the steel rail comprises the following chemical components in percentage by weight: 0.71 to 0.78 percent of C, 0.30 to 0.80 percent of Si, 0.80 to 1.1 percent of Mn, 0.1 to 0.3 percent of Cr, 0.04 to 0.2 percent of V, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and inevitable impurities, wherein the steel rail adopts an online heat treatment method: rapidly cooling the finally rolled steel rail, and then rapidly heating and insulating the gauge angle part; conditions for rapid cooling include: the initial cooling temperature is 800-880 ℃, the cooling speed is 2-6 ℃/s, and the final cooling temperature is 430-470 ℃; the conditions for rapid heating and incubation include: raising the temperature of the track gauge angle to 700-800 ℃ at a heating rate of 3.0-4.0 ℃/s and preserving the heat for 2-4min. The steel rail disclosed by the patent needs to be added with high-valence alloy elements such as V and the like, the cost is high, meanwhile, the steel rail head is heated for many times in the production process of the steel rail, the production method is complex, secondary heating has a large negative effect on the performance stability of the steel rail head, and the service safety performance of a steel rail line is seriously influenced.
In patent CN 112301205a "pearlite steel rail with high yield ratio and its preparation method", a pearlite steel rail with high yield ratio and its manufacturing method are disclosed, the components of the steel rail are as follows by weight percentage: c:0.70 to 0.85%, si:0.2 to 0.8%, mn:0.8 to 1.1%, cr:0.5 to 0.7%, cu:0.01 to 0.1%, nb:0.01 to 0.05%, P: less than or equal to 0.020%, S: not more than 0.015 percent, not more than 0.005 percent of Al and the balance of Fe and inevitable impurities, the steel rail adopts an online heat treatment method, the heat treatment is a multi-stage cooling process, and the steel rail is cooled to the room temperature from 850 to 950 ℃ at different cooling speeds. The steel rail disclosed by the patent has high yield strength, but the tensile strength of the steel rail exceeds 1300MPa, so that the steel rail is easy to cause rapid wheel abrasion in the use of a low-axle-weight passenger-cargo mixed transportation line, the line maintenance cost is improved, and meanwhile, the steel rail contains a large amount of alloy elements such as Cr, cu and Nb, so that the production cost is high, and the popularization and production are difficult.
In the related patents of the existing heat-treated pearlite steel rail and the production method thereof, although most of the steel rails disclosed by the patents have good strength and hardness, the research on the yield strength of the steel rail is rough, the improvement of the yield strength is mainly driven by the improvement of the overall tensile property, the condition that the service safety is reduced on the contrary due to the overhigh tensile strength in the application process of a low-axle-weight line of the steel rail is not considered, the obtained heat-treated pearlite steel rail cannot completely meet the performance requirements after the upgrading and transformation of a passenger-cargo mixed transportation line, and the chemical component system and the production process are complex and are difficult to realize large-scale application.
Disclosure of Invention
Aiming at the defects and shortcomings of the prior art, the invention aims to provide a medium-strength steel rail with high yield strength and a production method thereof, so as to meet the requirements of standard sound insulation and shock absorption, and have the advantages of higher construction speed, stronger adhesive force, lower cost, more stable sound insulation effect and the like.
In order to achieve the purpose, the invention provides the following technical scheme:
a medium strength steel rail having a high yield strength, the medium strength steel rail having: the yield strength is more than or equal to 820MPa, the tensile strength is 1200-1300MPa, and the elongation is more than or equal to 10%.
In one or more embodiments, the railhead microstructure of the medium strength steel rail is fully pearlitic.
In one or more embodiments, the medium strength rail has a top surface hardness of 350 to 390HB and a top surface and gauge angle 10mm depth section hardness of 35.5 to 41.0HRC.
In one or more embodiments, the chemical composition of the steel rail should be, in weight percent: 0.65-0.85% of C, 0.15-0.60% of Si, 0.50-1.30% of Mn, 0.05-0.20% of Cr, less than or equal to 0.020% of P, less than or equal to 0.015% of S and the balance of Fe.
The invention also provides a production method based on the medium-strength steel rail with high yield strength, which sequentially comprises the following steps: converter smelting, LF furnace refining, RH vacuum treatment, continuous casting to obtain a billet, rolling the billet, and carrying out online heat treatment and processing.
In one or more embodiments, the in-line heat treatment comprises:
a. cooling in the first stage: cooling the steel rail after finish rolling, wherein the cooling comprises accelerated cooling of the top surface of the steel rail, two upper fillets of the railhead, two side surfaces of the railhead and two lower fillets of the railhead until the temperature of the top surface of the rail is 630-750 ℃;
b. cooling in the second stage: b, carrying out accelerated cooling treatment on the top surface of the steel rail, two upper fillets of the rail head, two side surfaces of the rail head and two lower fillets of the rail head at a cooling speed of 3.0-6.0 ℃/s on the steel rail cooled in the step a until the temperature of the top surface of the rail is 400-500 ℃;
c. and (3) cooling in the third stage: and c, placing the steel rail cooled in the step c on a cooling bed, and air-cooling the steel rail to room temperature.
In one or more embodiments, the cooling medium employed for the in-line heat treatment is at least one of water mist, compressed air, a mixture of compressed air and water mist.
In one or more embodiments, in step a, the cooling treatment is performed when the temperature of the top surface of the steel rail after the final rolling is between 800 and 950 ℃.
In one or more embodiments, the cooling process is carried out at a cooling rate of 1.0 to 3.0 ℃/s.
In one or more embodiments, the cooling medium employed for in-line heat treatment compresses air.
Compared with the prior art, the invention has the beneficial effects that:
the invention adopts the method of controlling the chemical components of the steel rail and the on-line heat treatment process, and can obtain the medium-strength steel rail with high yield strength without adding a plurality of alloy elements, wherein the yield strength is more than or equal to 820MPa, the tensile strength is 1200-1300MPa, and the elongation is more than or equal to 10%. Therefore, the medium-strength steel rail provided by the invention can effectively reduce the probability of contact fatigue damage in the use of a passenger-cargo mixed transportation line, can effectively improve the service performance and service life of the steel rail, and improves the running safety of a train.
Detailed Description
The technical solution of the present invention will be described in further detail with reference to specific embodiments.
The invention provides a medium-strength steel rail with high yield strength, which has high yield strength, the yield strength is more than or equal to 820MPa, the tensile strength is 1200-1300MPa, and the elongation is more than or equal to 10%.
Furthermore, the rail head microstructure of the medium strength steel rail is fully pearlite.
Furthermore, the surface hardness of the top surface of the medium-strength steel rail is 350-390HB, and the section hardness of the top surface of the rail and the 10mm depth at the gauge angle is 35.5-41.0HRC.
Further, the medium-strength steel rail with high yield strength comprises the following chemical components in percentage by weight: 0.65 to 0.85 percent of C, 0.15 to 0.60 percent of Si, 0.50 to 1.30 percent of Mn, 0.05 to 0.20 percent of Cr, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and inevitable impurities.
As a preferred scheme, the steel rail comprises the following chemical components in percentage by weight: 0.70 to 0.85 percent of C, 0.30 to 0.60 percent of Si, 0.95 to 1.25 percent of Mn, 0.05 to 0.20 percent of Cr, less than or equal to 0.020 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and inevitable impurities. The reasons for limiting the contents of the main chemical elements of the steel rail according to the present invention will be described in detail below.
C is the most important and cheapest element in pearlite steel rail, which can make the steel rail obtain good comprehensive mechanical property and promote pearlite transformation. When the content of C is less than 0.65%, the proper high hardness of the steel rail and the contact fatigue resistance of the steel rail cannot be ensured under the production process; when the content of C is more than 0.85 percent, under the production process, the carbide proportion of the steel rail is too high, the tensile strength is too high, the strength index is excessive, the contact fatigue resistance of the steel rail in the service process is reduced, and the safety use of the steel rail is adversely affected; therefore, the carbon content in the present invention is limited to 0.65 to 0.85%.
The main functions of Si in steel are to suppress the formation of cementite and act as a solid solution strengthening element, to increase the hardness of the ferrite matrix, and to improve the strength and hardness of the steel. When the content of Si is less than 0.15%, the strengthening effect is not obvious due to low solid solution amount, and abnormal structures such as martensite and the like easily appear in the steel rail; when the content of Si is more than 0.60%, local segregation is easy to generate, the toughness and the plasticity and the weldability of steel are reduced, and the safe use of the steel rail is negatively influenced. Therefore, the Si content in the present invention is limited to 0.15 to 0.60%.
Mn is essential for improving the strength of ferrite and austenite in steel. When the Mn content is less than 0.50%, it is difficult to achieve the effect of increasing the hardness of carbides to thereby increase the strength of the steel; when the Mn content is more than 1.30%, the Mn can coarsen the grain size, influence the structural change of the rail steel in the heat treatment process and obviously reduce the toughness and plasticity of the steel; meanwhile, mn has a significant influence on the diffusion of C in steel, and may generate abnormal structures such as bainite and martensite in Mn segregation regions, and may affect the weldability of rails. Therefore, the Mn content in the present invention is limited to 0.50 to 1.30%.
Cr is used as a carbide forming element and can form various carbides with carbon in steel; meanwhile, cr can be used for uniformly distributing carbide in steel, reducing the size of the carbide and improving the wear resistance of the steel rail. When the Cr content is less than 0.05%, the hardness and the proportion of the formed carbide are lower; when the Cr content is more than 0.20 percent, the hardenability of the steel rail is too high, the steel rail is easy to produce harmful bainite and martensite structures, and the steel rail cannot be ensured to be a full pearlite structure while the mechanical property of the steel rail is reduced. Therefore, the Cr content in the present invention is limited to 0.05 to 0.20%.
P and S are impurity elements which cannot be completely removed from the steel rail. P is partially polymerized at the grain boundary of the steel rail structure, so that the toughness of the steel rail is seriously reduced; s is easy to form MnS inclusions in steel and is harmful to the wear resistance and contact fatigue resistance of the steel rail. Therefore, the content of P in the invention needs to be controlled below 0.020%; the S content is controlled below 0.015%.
The invention also provides a production method of the medium-strength steel rail with high yield strength, which sequentially comprises the following steps: converter smelting, LF furnace refining, RH vacuum treatment, continuous casting to obtain a steel billet, rolling the steel billet, and performing online heat treatment and processing.
Further, in the method for producing the medium-strength steel rail with high yield strength, the online heat treatment comprises the following steps:
a. cooling in the first stage: when the temperature of the top surface of the steel rail after finish rolling is between 800 and 950 ℃, carrying out accelerated cooling treatment on the top surface of the steel rail, two upper fillets of the railhead, two side surfaces of the railhead and two lower fillets of the railhead at a cooling speed of 1.0 to 3.0 ℃/s until the temperature of the top surface of the rail is 630 to 750 ℃;
b. cooling in the second stage: b, performing accelerated cooling treatment on the top surface of the steel rail, two upper fillets of the rail head, two side surfaces of the rail head and two lower fillets of the rail head at a cooling speed of 3.0-6.0 ℃/s on the steel rail cooled in the step a until the temperature of the top surface of the rail is 400-500 ℃;
c. and (3) cooling in the third stage: and c, placing the steel rail cooled in the step c on a cooling bed, and air-cooling the steel rail to room temperature.
Furthermore, the cooling medium adopted by the on-line heat treatment of the patent is at least one of water mist, compressed air and a mixture of the compressed air and the water mist.
The inventors of the present invention have found through a great deal of research that:
(1) aiming at the first stage cooling of the online heat treatment process: when the tread temperature of the rail head of the steel rail is 800-950 ℃, the steel rail does not start pearlite phase transformation, in order to obtain the steel rail with high yield strength, and simultaneously, the tensile strength of the steel rail is not excessively improved, a lower cooling speed is required to uniformly reduce the temperature of the steel rail, and in order to ensure that the temperature of the rail head of the steel rail is uniformly reduced, the cooling speed is required to be controlled between 1.0-3.0 ℃/s;
(2) and (3) aiming at the second stage cooling of the online heat treatment process: when the tread temperature of the rail head of the steel rail is cooled to 630-750 ℃ through a first stage, the steel rail starts to generate pearlite phase transformation, a higher cooling speed is needed to obtain the steel rail with high yield strength by considering the heat transfer from the part, which is not cooled, of the steel rail to the rail head, and the cooling speed is controlled to be 3.0-6.0 ℃/s in the second stage of cooling;
(3) cooling for the third stage: after the first two cooling stages are finished, the internal temperature of the rail head of the steel rail is within the range of 400-500 ℃, the pearlite phase transformation process of the steel rail is finished, the continuous accelerated cooling has no obvious significance, and the steel rail can be cooled to room temperature by air for subsequent process treatment.
The complete production process of the production method of the medium-strength steel rail with high yield strength can be as follows: smelting low-sulfur vanadium-containing molten steel by a converter or an electric furnace, performing LF refining, RH or VD vacuum treatment, protecting and continuously casting blooms, heating billet heating furnaces, descaling billets by high-pressure water before rolling, rolling by a universal mill, performing online steel rail heat treatment, cooling by air at room temperature by a stepping cooling bed, performing horizontal and vertical composite straightening, checking steel rail specifications, processing line treatment, checking surfaces and warehousing.
The present invention will be described in detail below by way of examples, but the scope of the present invention is not limited thereto.
Examples 1 to 3 and comparative examples 1 to 3 correspond to steel rails having chemical compositions of the following numbers 1 to 3, and the manufacturing process is the same as described above, and the specific chemical compositions are shown in table 1.
TABLE 1
| Numbering | C | Si | Mn | Cr | P | S |
| 1 | 0.80 | 0.50 | 1.09 | 0.08 | 0.011 | 0.006 |
| 2 | 0.74 | 0.55 | 1.02 | 0.15 | 0.017 | 0.012 |
| 3 | 0.78 | 0.48 | 0.99 | 0.11 | 0.009 | 0.003 |
The balance being Fe and unavoidable impurities.
Examples 1-3 comparative examples 1-3 heat treatment process parameters as shown in table 2, the differences between the smelting process and the rolling process of the examples and comparative examples are negligible.
TABLE 2
In the invention, according to GB/T228.1 part 1 of metal material tensile test: the yield strength, tensile strength and elongation after fracture of the steel rail are tested according to a room temperature test method, according to GB/T230.1 part 1 of Rockwell hardness test of metal materials: test method for testing the section hardness of the steel rail at the position of 10mm, according to GB/T231.1 Brinell hardness test part 1 of metal materials: test method tests the hardness of the surface of the top surface of the steel rail. Tensile properties, rail top surface hardness, and 10mm site section hardness of examples 1 to 3 and comparative examples 1 to 3 are shown in Table 3.
TABLE 3
Compared with the comparative example, the embodiment of the invention has the advantages that under the same chemical components and smelting process, the final performance of the steel rail is obviously influenced by the different online heat treatment modes of the rolled steel rail, and the steel rail obtained by adopting the method has high yield strength which is more than or equal to 820MPa, the tensile strength which is 1200-1300MPa and the elongation which is more than or equal to 10 percent; in contrast, in the comparative example, the yield strength, tensile strength or microstructure of the steel rail was not satisfactory.
While the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.
Claims (10)
1. A medium strength steel rail having a high yield strength, said medium strength steel rail comprising: the yield strength is more than or equal to 820MPa, the tensile strength is 1200-1300MPa, and the elongation is more than or equal to 10%.
2. A medium strength steel rail with high yield strength according to claim 1 wherein the rail head microstructure of the medium strength steel rail is fully pearlitic.
3. A medium strength steel rail with high yield strength according to claim 1 or 2 wherein the surface hardness of the top surface of the rail is 350-390HB and the 10mm depth section hardness at the top surface and gauge angle is 35.5-41.0HRC.
4. A high yield strength medium strength steel rail according to claim 3, wherein the steel rail has a chemical composition, in weight percent, of: 0.65-0.85% of C, 0.15-0.60% of Si, 0.50-1.30% of Mn, 0.05-0.20% of Cr, less than or equal to 0.020% of P, less than or equal to 0.015% of S and the balance of Fe.
5. A method for producing a medium-strength steel rail with high yield strength is characterized by sequentially comprising the following steps: converter smelting, LF furnace refining, RH vacuum treatment, continuous casting to obtain a billet, rolling the billet, and carrying out online heat treatment and processing.
6. The production method according to claim 5, wherein the in-line heat treatment comprises:
a. cooling in the first stage: cooling the steel rail after final rolling, wherein the cooling comprises accelerated cooling of the top surface of the steel rail, two upper fillets of the railhead, two side surfaces of the railhead and two lower fillets of the railhead until the temperature of the top surface of the rail is 630-750 ℃;
b. cooling in the second stage: b, performing accelerated cooling treatment on the top surface of the steel rail, two upper fillets of the rail head, two side surfaces of the rail head and two lower fillets of the rail head at a cooling speed of 3.0-6.0 ℃/s on the steel rail cooled in the step a until the temperature of the top surface of the rail is 400-500 ℃;
c. and (3) cooling in the third stage: and d, placing the steel rail cooled in the step c on a cooling bed, and air-cooling the steel rail to room temperature.
7. The production method according to claim 6, wherein the cooling medium used for the in-line heat treatment is at least one of water mist, compressed air, and a mixture of compressed air and water mist.
8. The production method according to claim 6, wherein in the step a, when the temperature of the top surface of the steel rail after finish rolling is between 800 and 950 ℃, cooling care is carried out.
9. The production method according to claim 6, wherein in the cooling treatment, the temperature is lowered at a cooling rate of 1.0-3.0 ℃/s.
10. The production method according to claim 6, wherein the cooling medium used for the in-line heat treatment is compressed air.
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| CN202210941427.6A CN115233503A (en) | 2022-08-05 | 2022-08-05 | Medium-strength steel rail with high yield strength and production method thereof |
| PCT/CN2023/093537 WO2024027264A1 (en) | 2022-08-05 | 2023-05-11 | Medium-strength steel rail having high yield strength and production method therefor |
| AU2023319321A AU2023319321A1 (en) | 2022-08-05 | 2023-05-11 | Medium-strength steel rail having high yield strength and production method therefor |
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| CN202210941427.6A CN115233503A (en) | 2022-08-05 | 2022-08-05 | Medium-strength steel rail with high yield strength and production method thereof |
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| WO2024027264A1 (en) * | 2022-08-05 | 2024-02-08 | 攀钢集团攀枝花钢铁研究院有限公司 | Medium-strength steel rail having high yield strength and production method therefor |
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| AU2023319321A1 (en) | 2024-05-30 |
| WO2024027264A1 (en) | 2024-02-08 |
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