CN105385938A - Alloy system, heat treatment method for Bainite steel rail of alloy system and Bainite steel rail - Google Patents
Alloy system, heat treatment method for Bainite steel rail of alloy system and Bainite steel rail Download PDFInfo
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- CN105385938A CN105385938A CN201510919742.9A CN201510919742A CN105385938A CN 105385938 A CN105385938 A CN 105385938A CN 201510919742 A CN201510919742 A CN 201510919742A CN 105385938 A CN105385938 A CN 105385938A
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- 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
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- 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
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/20—Isothermal quenching, e.g. bainitic hardening
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- 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
- C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
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- 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
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
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- 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
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- 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
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- 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
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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- 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
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- 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
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- 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
- C21D2211/002—Bainite
Abstract
The invention provides an alloy system, a heat treatment method for a Bainite steel rail of the alloy system and the Bainite steel rail. The alloy system comprises, by mass, 0.22-0.27% of C, 1.65-1.85% of Si, 1.60-1.80% of Mn, 1.30-1.90% of Cr, 0.25-0.85% of Mo, 0.25-0.95% of Ni, 0.040-0.060% of V or 0.020-0.040% of Nb, 0.015% or less of P, 0.015% or less of S, and the balance Fe and inevitable impurity elements. The impurity elements are strictly controlled according to the standards that (1) gas content: molten steel [H]<=2.0 ppm, casting blanks [H]<=1.5 ppm, [O]<=25 ppm, and [N]<=70 ppm; and (2) residual elements: Al<=0.006%, Cu<=0.15%, Sn<=0.010%, and Sb<=0.010%. The heat treatment method has the production characteristics that refining of austenite structures as well as segregation and unevenness of elements and microstructures are effectively controlled, so that fine and even lower Bainite structures are obtained easily after the cooling phase change, it is guaranteed that phase change of the lower Bainite structures of the steel rail occurs completely through effective control, and accordingly the Bainite steel rail high in performance is obtained.
Description
Technical field
The invention belongs to the technical field of heat treatment of bainite rail, specifically relate to heat treating method and the bainite rail of a kind of alloy system and bainite rail thereof.
Background technology
China's heavy haul railway annual traffic has surpassed hundred million tons, wherein two fortune coal heavy haul railway main line Shuohuang Railway year fortune coal amount surpass 200,000,000 tons, the year fortune coal amount fortune coal amount of expanding on Dalian-Qinhuangdao Railway surpasses 400,000,000 tons.Train shaft is heavy also to be improved constantly, and Shuohuang Railway axle weighs 30 tons of heavy haul train successes of the test.Along with the raising of railway transporting amount, the serious hurt of tensile strength 980MPa level pearlite steel rail has become the bottleneck of Railway transportation throughput rate raising.Select the low-alloy high-strength bainite rail of more than 1200MPa level, become the Main way of heavy haul railway rail exploitation nearly ten years.
In low-alloy high-strength bainite rail technical field, nearly ten remainder patents are successively had to obtain mandate, specific as follows: patent of invention number: 02158853.8, to resistance to wear, high-strong toughness meta-bainite rail and manufacture method thereof.Patent of invention number: 200510047907.4, has rail and the production method thereof of the bainite structure of excellent anti-fatigue performance.Patent of invention number: 2011104191837, a kind of high strength bainite steel rail and thermal treatment process thereof.Patent of invention number: 2011100778921, a kind of corrosion-resistant bainite rail.Patent of invention number: 98112095.4, high speed quasi high-speed highway road basin high-performance abrasion-proof steel and preparation method thereof.Patent of invention number: 2009100635812, a kind of ultra-high strength bainite rail steel and manufacture method thereof.Patent of invention number: 02158852.X, resistance to wears, high-strong toughness meta-bainite railroad turnout steel rail and production technique thereof.Patent of invention number: 200610012673.4, dedicated tungsten-containing bainite forged steel for railway frog crossing and manufacture method thereof.Patent of invention number: 99800029.9, has the bainitic steel rail of high resistance surface fatigue hurt and high-wearing feature.Patent of invention number: 94101720.6, the manufacture method of the bainite high duty rails of the resistance to rolling contact fatigue hurt of tool excellence.
Above-mentioned patented technology all have employed the technological line without carbon bainite steel adding the alloy such as Cr, Mo, Ni and V, Nb microalloy element in middle C height Si height Mn alloy system.Object wishes that only adopting hot rolling to produce just can obtain air cooling condition lower bainite microtexture, thus obtain high strength and high-plasticity energy.But without carbon bainite core feature be still the structure and morphology feature of lath bainitic ferrite in upper bainite and residual austenite.Si is passed through in research through scholar, Mn, the regulation and control of the alloy content of Mo, what inhibit bainite ferrite lath too grows up simultaneously, residual austenite number size in meta-bainite is effectively controlled, microscopic observation is similar to non-pattern such as ferrite such as axle such as grade, but partial austenitic but exists with the form of martensitic transformation, more go deep into microanalysis to show, meta-bainite still has lath bainitic ferrite pattern, namely so-calledly the atypical quasi-bainite steel of novel Si-Mn-Mo series is defined, this bainite still can not be completely free of lath bainitic ferrite Facial Features, i.e. upper bainite tissue signature, but along with Mn, the possibility that the increase of Mo content but adds local, rail section martensitic stucture quantity to be increased can not be effectively controlled, all containing a small amount of martensitic stucture in the quasi-bainite steel that current document is announced, this mixed structure rail in actual applications effect is not very good.
Show in concrete actual production and application, so-called hot rolling and air cooling bainite rail all needs the temper after rolling, and is beneficial to reduce bainitic steel high residual stress inherently, ensures the stability of rail military service performance.Nonetheless, detect analysis and show that the unrelieved stress of bainite rail is still higher than pearlite steel rail.Simultaneously because rail shaped steel changes of section is large, and bainite structure is to the feature of cooling conditions sensitivity, bainite rail in actual hot rolling production, no matter because of its high silicomanganese content without carbon bainite or meta-bainite rail, the inconsistent meeting of rail different sites cooling rate obviously causes component segregation, local produces martensitic stucture or residual austenite coarsening, unrelieved stress is too high, Aging Characteristic is obvious, rail entire body performance is inconsistent, the feature that cross section performance variation is large is very outstanding, when being subject to external force effect as under the conditions such as Wheel Rail Contact friction, there is acute variation in localized micro structure and properties, and there is disconnected rail, peel off, the phenomenons such as fish scale wound.Consequently there is mixed phenomenon in upper track service life, and the popularization of bainite rail is restricted always.Service life that is stable and prolongation bainite rail has become the emphasis of bainite rail exploitation.
In sum, need to develop a kind of structure stability, obdurability, the lower bainite that fatigue performance is higher organizes rail.Lower bainite has following characteristics of organizational structure: 1. the spatial shape of lower bainite is lenticular, crossing with sample flour milling in the form of sheets or needle-like.2. formed on austenite grain boundary, but be more formed in austenite crystal inside.3. in lower bainite, ferritic substructure is dislocation, and its dislocation desity is than height ferritic in upper bainite.Containing oversaturated carbon in the ferrite of lower bainite, its solid solution capacity is higher than upper bainite, and reduces with formation temperature and increase.Residual austenite comparatively speaking in lower bainite no matter quantity and size is all less than or is less than content in upper bainite.The intensity of lower bainite is higher, and toughness is also better, and the intensity of upper bainite is low, and toughness is very poor, and with the reduction of bainite formation temperature, intensity and toughness progressively improve, and plasticity and toughness improve along with the reduction of formation temperature too.Carbides In Lower Bainite particle is less, and grain amount is also more, so carbide is also larger to the contribution of lower bainite.Because upper bainite ferrite bar is arranged in parallel with each other bunchy, between bar and bar, position is very little to difference, seems a crystal grain, and lower bainite ferrite lamellae position is very large to difference each other.Namely the Effective grain size diameter of upper bainite is far longer than lower bainite, and the carbide of upper bainite is that sequential like is distributed between ferrite bar in addition, result in upper bainite performance relatively poor.
Therefore, develop the production technology of the bainite rail based on lower bainite, really can play its high strength, high tenacity and long lifetime feature is emphasis of the present invention.But the controlling of production process obtaining lower bainite is comparatively complicated, the method being difficult to be regulated and controled by alloy system is obtained.Experiment shows effect by adding alloying element Ni, V, Nb and carry out stable residual austenite and reduce unrelieved stress and not obvious, therefore needs to be obtained by Heat Treatment Measures.The present invention develops the production technique of thin brilliant lower bainite rail, and in the actual application of laying a railway track of heavy haul railway, achieves the effect of good resistance to rolling contact fatigue.
Summary of the invention
The object of the invention is to provide heat treating method and the bainite rail of a kind of bainite rail alloy system and bainite rail thereof.The productive prospecting of this technique is, effectively controls the refinement of austenite structure and the segregation of element and microtexture and uneven phenomenon, obtains tiny uniform lower bainite tissue after being beneficial to cooling phase-change.In production thermal treatment process, ensure effectively to control the phase transformation that lower bainite tissue occurs rail completely, thus obtain high performance bainite rail.Therefore, after bainite rail hot rolling is produced, need to carry out second heat treatment work, namely the present invention adopts normalizing+modified twice thermal treatment process route, effectively reduce the unrelieved stress of component segregation, refinement bainite structure, decompose refinement and stabilization residual austenite microtexture, eliminate a small amount of martensitic stucture, make the microtexture of rail section and hardness more even, the properties of full-scale rail is stabilized in narrow fluctuation range.Thus significantly improve the military service performance of rail.
Technical scheme of the present invention is as follows:
One aspect of the present invention provides a kind of alloy system of bainite rail, it is characterized in that: the composition of described alloy system is as follows by percentage to the quality: C:0.22 ~ 0.27; Si:1.65 ~ 1.85; Mn:1.60 ~ 1.80; Cr:1.30 ~ 1.90; Mo:0.25 ~ 0.85; Ni:0.25 ~ 0.95; V:0.040 ~ 0.060 or Nb:0.020 ~ 0.040, P :≤0.015, S :≤0.015; Surplus is Fe and inevitable impurity element; Wherein impurity element is strictly controlled: (1) gas content: molten steel [H]≤2.0ppm, strand [H]≤1.5ppm, [O]≤25ppm, [N]≤70ppm; (2) residual element: Al≤0.006%, Cu≤0.15%, Sn≤0.010%, Sb≤0.010%.
The production technique of usual bainite rail is, 850-950 DEG C of austenitizing is reheated after rail hot rolling or after hot rolling and air cooling to room temperature, then controlled cooling model speed passes through pearlitic ferrite transition temperature area (greatly between 550-700 DEG C) with very fast speed of cooling, its speed of cooling is greater than 0.3 DEG C/s, and object avoids ferritic-pearlitic phase transformation occurs.Then controlled cooling model speed is to be less than 5 DEG C/s, and after being cooled to 200 DEG C, air cooling is to room temperature, and as far as possible the object of this stage control cooling rate makes phase transformation occur in bainite speed of cooling control interval, instead of due to too fast cooling rate generation martensite.In order to stable microtexture and residual austenite, eliminate unrelieved stress, also need to carry out temper in 300-400 DEG C of interval.The complicacy that above-mentioned bainite rail is produced needs to coordinate the actual rhythm of Rolling production exactly, continuous adjustment cooling velocity after rolling, simultaneously due to the changes of section of rail, the cross section speed of cooling of rail can not be made always, cause section hardness skewness, and local, corner and internal component segregation place are easy to produce martensitic stucture or local grain unusual phenomenon thus the deterioration causing bainite rail performance, the final use properties affecting rail.
The martensitic transformation temperature of the alloy system of above-mentioned bainite rail is 320 DEG C, lower bainite formation temperature less than 360 DEG C.In order to ensure that in thermal treatment bainite rail, microtexture does not produce martensitic stucture or ferritic-pearlitic tissue, hardening of rails final temperature controls between 320 DEG C-360 DEG C, then long-time isothermal phase change process.Namely in modified quenching process, control rail cooling temperature think more than temperature and the following temperature range of Lower Bainite Transformation temperature at martensite.The stability contorting of residual austenite, in bainite structure, the elimination of residualinternal stress is the key that bainite rail ensures operation life.Therefore long normalizing and anneal is needed.
The present invention additionally provides a kind of heat treating method of the bainite rail using above-mentioned alloy system to prepare on the other hand, and it is characterized in that, described heat treating method is specific as follows:
Normalizing+adjustment process: normalizing temperature is 900-940 DEG C of austenite warm area heating, and stove inside holding was more than 8 hours, and air cooling of coming out of the stove is to room temperature;
Quenching: at Ac3+50 ~ 70 DEG C austenite (about 830-900 DEG C) warm area scope inside holding after 7 hours, water-cooled direct quenching is between the above 320-350 of martensitic transformation temperature DEG C;
Isothermal phase change: then at 320-350 DEG C, rail stacking is put into holding pit isothermal holding, is performed for more than isothermal phase change process in 5 hours;
Temper process: after isothermal phase change process, bainite rail is carried out temper, tempering temperature is 320-370 DEG C, insulation more than 9 hours after air cooling to room temperature.
The present invention additionally provides a kind of bainite rail adopting the heat treating method of above-mentioned bainite rail to prepare on the other hand, and described bainite rail performance meets following index: yield strength R
p0.2>1240MPa; Tensile strength R
m>1500MPa; Unit elongation A%>15; Ballistic work A
kuroom temperature >110J; Reduction of area Z%>50; FATIGUE FRACTURE TOUGHNESS K
1C>90MPam
1/2, rail section Hardness Control is at 39-42HRC.
Microstructure for carbon-free bainite rail is generally made up of lath ferrite and second-phase, and second-phase comprises carbide, martensite or residual austenite, namely so-called without carbon bainite steel.And transformation temperature to be obtained generally lower than the needle-like lower bainite sheet tissue of 350 DEG C.Its alloys producing and span of control as follows:
Carbon: carbon is the element producing gap solution strengthening and carbide precipitation strengthening in martensitic transformation, and be the principal element that steel obtains high strength.When carbon content is greater than 0.45%, easily generate hard and crisp high carbon martensite phase, easily produce at rolling surface and peel off and other layering.And carbon content is just difficult to obtain the intensity needed for bainite structure when being less than 0.15%, carbon content is too low, is just difficult to be formed in rolling resistance to the hard carbon compound that wear resistance plays an important role.Therefore, this is that steel carbon content is usually between 0.15% ~ 0.45%.In addition, carbon can also increase cold shortness and the aging sensitivity of steel.
Silicon: the elastic limit that can significantly improve steel, yield-point and tensile strength.Bainitic transformation district is moved to right, solution strengthening bainite, improve the wear resistance of bainite rail.Silicon can suppress the precipitation of cementite, when the add-on of silicon is enough, when certain cooling rate in bainitic transformation process, along with the formation of bainitic ferrite, carbon is to its adjacent supercooled austenite place enrichment, improve the stability of supercooled austenite, partial austenitic is retained to room temperature, and the precipitation defining the carbide-free Bainite cementite formed primarily of bainitic ferrite and residual austenite is completely suppressed.Si promotes to form retained austenitic film, again deferrable one-step temper embrittlement in bainite.Tempering temperature can be increased to 300 DEG C and increase toughness and anti-delayed fracture performance.When Si content is more than 2.0%, easily there is surface imperfection in rail.Therefore, bainite rail steel grade Si content is generally between 0.9% ~ 2.0%.Si and Cr, Mo can be in conjunction with, are improved erosion resistance and oxidation resistant effect.
Manganese: the effect of Mn, Cr element: be all suppress low Bs point element, improves bainite hardening capacity and intensity, improves the hot workability of steel.。When Cr, Mn content is more than 3.0%, easily produce too crisp carbide, reduce the toughness of bainite structure.Mn reduces Ms point, and after making quenching, in steel, remained austenite content increases, thus reduces the size distortion after quenching.Due to manganese aggravation temper brittleness and superheated susceptivity, should add with Cr, Mo, V compound.Mn content is too high easily causes microstructure segregation, therefore actual use in cross high Mn content bainitic steel all there is the large and military service unstable properties phenomenon of properties plastisied dispersion.Therefore, Mn content major part is between 1.4% ~ 2.0%.
Chromium: chromium is ferrite former, in Fe-Cr two component system, it reduces austenitic area, but in Fe-Cr-Ni three component system, situation is just in time contrary, and Cr does not only hinder the formation that can also promote austenite phase on the contrary.In order to obtain enough hardening capacity, dissolve in matrix and cause displacement solution strengthening, and Cr is to anticorrosive favourable with oxidation; Cr promotes cementite unstability and M
2c is formed, and replaces Mo
2in C, Mo forms (Mo, Cr)
2c, promotes secondary hardening reaction, forms small and dispersed precipitation.Cr content major part is between 0.5% ~ 2.0%
Nickel: nickel is unique intensity, hardening capacity that both can improve steel, can improve again the element of toughness; Be expand austenitic area element, can ensure that in steel, residual austenite has enough stability; Produce solution strengthening, reduce ductil-brittle transition temperature; The carbide precipitation of high Ni content and small and dispersed is the fundamental cause of this kind of steel high strength, high tenacity; The complexity of dislocation commutative Banach aglebra when the toughness of material depends on viscous deformation, Ni can make screw dislocation be not easy to decompose, and ensures the generation of commutative Banach aglebra, improves the toughness of steel.But to wear resistance, secondary hardening performance without contribution, and obviously worsen processing performance (forging property, the property of softening and machinability).Ni is added between 0% ~ 0.32%.
Molybdenum: molybdenum can make the grain refining of steel, increases hardening capacity, produces solution strengthening, also has the effect suppressing temper brittleness; Suppress and delay the gathering of alloy carbide and grow up, thus making age softening process shift to higher temperature, can corrosion stability be improved.Mo can make steel keep enough intensity and creep resisting ability (be at high temperature subject to stress for a long time, deform, claim creep) when high temperature; Improve anti-superheated susceptivity and obdurability.Add molybdenum in structure iron, can mechanical property be improved.The fragility that steel alloy causes due to tempering can also be suppressed.Most Mo content is between 0.20% ~ 0.45%.
Vanadium: the strong crystal grain thinning of vanadium, strong raising wear resistance and secondary hardening ability, improves anti-superheated susceptivity; But what content too much obviously can worsen steel can forgeability and grinding performance, therefore the content of vanadium in steel is generally at about 0.2%-2%.
Copper: copper can improve intensity and toughness, particularly atomospheric corrosion performance.Shortcoming easily produces hot-short, and copper content significantly reduces more than 0.5% plasticity.When copper content is less than 0.5% to weldability without impact.
Phosphorus: in the ordinary course of things, phosphorus is harmful element in steel, increases the cold shortness of steel, welding property is degenerated, and reduces plasticity, cold-bending property is degenerated.Therefore usually require that in steel, phosphorus content is less than 0.045%, bainitic steel requirement is some more low is less than 0.015%.
Sulphur: sulphur is also harmful element under normal conditions.Make steel produce red brittleness, reduce ductility and the toughness of steel, cause crackle when forging and rolling.Sulphur is also unfavorable to welding property, reduces erosion resistance.So bainitic steel sulphur content is less than 0.015%.
Steel medium trace element such as boron, titanium and hydrogen etc. can produce certain influence to its toughness.Boron significantly postpones ferrite forming core by segregation at austenite grain boundary.For avoiding the formation of boron nitride, affect the effect of boron, therefore suitably add aluminium with fixed nitrogen.The Hydrogen Embrittlement of the above steel of 1000MPa level significantly increases, and controls hydrogen richness at below 2.0ppm.Other gas content oxygen, nitrogen also need strict restriction, are beneficial to the control of inclusion pattern and size.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of bainite rail prepared by the present invention;
In figure: 1, rail head the 1st is apart from surperficial 5mm, and all the other dot spacings are 5mm; D, E line and lower jaw distance 5mm; B, C line is the angular bisector of A, E line; 2, web of the rail spacing 15mm; 3, flange of rail spacing 20mm.
Embodiment
Be described in detail the production method of steel alloy of the present invention and finish rolling deformed bar thereof and finish rolling deformed bar below in conjunction with embodiment, the steel product ingredient of each embodiment is in table 1.
In an embodiment, the invention provides a kind of alloy system of bainite rail, the composition of described alloy system is as follows by percentage to the quality: C:0.22 ~ 0.27; Si:1.65 ~ 1.85; Mn:1.60 ~ 1.80; Cr:1.30 ~ 1.90; Mo:0.25 ~ 0.85; Ni:0.25 ~ 0.95; V:0.040 ~ 0.060 or Nb:0.020 ~ 0.040, P :≤0.015, S :≤0.015; Surplus is Fe and inevitable impurity element; Wherein impurity element is strictly controlled: (1) gas content: molten steel [H]≤2.0ppm, strand [H]≤1.5ppm, [O]≤25ppm, [N]≤70ppm; (2) residual element: Al≤0.006%, Cu≤0.15%, Sn≤0.010%, Sb≤0.010%.
In another embodiment, present invention also offers a kind of heat treating method of the bainite rail using above-mentioned alloy system to prepare, described heat treating method is specific as follows:
Normalizing+adjustment process: normalizing temperature is 900-940 DEG C of austenite warm area heating, and stove inside holding was more than 8 hours, and air cooling of coming out of the stove is to room temperature;
Quenching: at Ac3+50 ~ 70 DEG C austenite (about 830-900 DEG C) warm area scope inside holding after 7 hours, water-cooled direct quenching is between the above 320-350 of martensitic transformation temperature DEG C;
Isothermal phase change: then at 320-350 DEG C, rail stacking is put into holding pit isothermal holding, is performed for more than isothermal phase change process in 5 hours;
Temper process: after isothermal phase change process, bainite rail is carried out temper, tempering temperature is 320-370 DEG C, insulation more than 9 hours after air cooling to room temperature.
In another embodiment, present invention also offers a kind of bainite rail adopting the heat treating method of above-mentioned bainite rail to prepare, described bainite rail performance meets following index: yield strength R
p0.2>1240MPa; Tensile strength R
m>1500MPa; Unit elongation A%>15; Ballistic work A
kuroom temperature >110J; Reduction of area Z%>50; FATIGUE FRACTURE TOUGHNESS K
1C>90MPam
1/2, rail section Hardness Control is at 39-42HRC.
The thermal treatment process of the bainite rail of the embodiment of the present invention 1 ~ 4 is given in table 1; The bainite rail mechanical property that table 2 gives the embodiment of the present invention 1 ~ 4 improves situation; The bainite rail section hardness that table 3 gives embodiment 1 ~ 4 can improve situation.
Table 1 bainite rail thermal treatment process
Table 2 bainite rail mechanical property improves situation
Table 3 bainite rail section hardness can improve situation HRC
The above; be only the present invention's preferably embodiment, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.
Claims (3)
1. an alloy system for bainite rail, is characterized in that: the composition of described alloy system is as follows by percentage to the quality: C:0.22 ~ 0.27; Si:1.65 ~ 1.85; Mn:1.60 ~ 1.80; Cr:1.30 ~ 1.90; Mo:0.25 ~ 0.85; Ni:0.25 ~ 0.95; V:0.040 ~ 0.060 or Nb:0.020 ~ 0.040, P :≤0.015, S :≤0.015; Surplus is Fe and inevitable impurity element; Wherein impurity element is strictly controlled: (1) gas content: molten steel [H]≤2.0ppm, strand [H]≤1.5ppm, [O]≤25ppm, [N]≤70ppm; (2) residual element: Al≤0.006%, Cu≤0.15%, Sn≤0.010%, Sb≤0.010%.
2. a heat treating method for the bainite rail using the alloy system described in claim 1 to prepare, is characterized in that, described heat treating method is specific as follows:
Normalizing+adjustment process: normalizing temperature is 900-940 DEG C of austenite warm area heating, and stove inside holding was more than 8 hours, and air cooling of coming out of the stove is to room temperature;
Quenching: DEG C austenite warm area scope inside holding is after 7 hours in Ac3+50 ~ 70, water-cooled direct quenching is between the above 320-350 of martensitic transformation temperature DEG C;
Isothermal phase change: then at 320-350 DEG C, rail stacking is put into holding pit isothermal holding, is performed for more than isothermal phase change process in 5 hours;
Temper process: after isothermal phase change process, bainite rail is carried out temper, tempering temperature is 320-370 DEG C, insulation more than 9 hours after air cooling to room temperature.
3. adopt the bainite rail that the heat treating method of bainite rail according to claim 3 prepares, it is characterized in that, described bainite rail performance meets following index: yield strength R
p0.2>1240MPa; Tensile strength R
m>1500MPa; Unit elongation A%>15; Ballistic work A
kuroom temperature >110J; Reduction of area Z%>50; FATIGUE FRACTURE TOUGHNESS K
1C>90MPam
1/2, rail section Hardness Control is at 39-42HRC.
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Address after: 100081 No. 76 South College Road, Beijing, Haidian District Co-patentee after: Advanced Steel Technology Co., Ltd. Patentee after: Central Iron & Steel Research Institute Co-patentee after: Zhejiang Bell Rail Equipment Co., Ltd. Address before: 100081 No. 76 South College Road, Beijing, Haidian District Co-patentee before: Advanced Steel Technology Co., Ltd. Patentee before: Central Iron & Steel Research Institute Co-patentee before: Zhejiang Bell Communication Group Co., Ltd. |