CN105838988B - The steel of axle of motor train unit containing niobium and its heat treatment process - Google Patents

The steel of axle of motor train unit containing niobium and its heat treatment process Download PDF

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CN105838988B
CN105838988B CN201610416945.0A CN201610416945A CN105838988B CN 105838988 B CN105838988 B CN 105838988B CN 201610416945 A CN201610416945 A CN 201610416945A CN 105838988 B CN105838988 B CN 105838988B
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axle
steel
temperature
heat treatment
train unit
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CN105838988A (en
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孙维
苏世怀
杜松林
高海潮
汪开忠
龚志翔
于文坛
谢世红
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Maanshan Iron and Steel Co Ltd
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Maanshan Iron and Steel Co Ltd
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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
    • 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")
    • 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
    • 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
    • C21D9/28—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for plain shafts
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • C21D2211/002—Bainite

Abstract

The present invention relates to the steel of axle of motor train unit containing niobium and its heat treatment process, contain C according to weight percent：0.24~0.30, Si：0.20~0.40, Mn：0.70~1.00, Cr：0.90~1.20, Ni：0.70~1.30, Mo：0.20~0.30, Cu：0.10~0.60, Zr：0.01~0.04, Nb：0.015~0.050, Ca：0.001~0.005, P≤0.010, S≤0.008, [N]：0.0040~0.0060, T [O]≤0.0015, Als：0.015~0.045, remaining is Fe and other inevitable impurity；The steel is organized as tempered sorbite+a small amount of lower bainite, wherein, axle near surface tempered sorbite content is 100%, and tempered sorbite content is 75~85% at 1/2 radius of axle.Its plasticity and toughness are substantially better than business steel after special thermal treatment, and fatigue limit will be significantly higher than business steel, show good strength and toughness cooperation and excellent anti-fatigue performance.

Description

The steel of axle of motor train unit containing niobium and its heat treatment process
Technical field
The present invention relates to field of alloy steel, and in particular to 750~900MPa of tensile strength, yield strength >=600MPa, -40 ℃KV2>=150J, while require the high-speed EMU axles steel and its heat treatment process of excellent anti-fatigue performance.
Background technology
Axle is one of most important movement safe involved in various vehicles and load bearing component.Due to axle subject it is dynamic Load, stress is more complicated, such as bending load, torsional load, bending combined load, and is subject to certain impact, particularly High-speed EMU axle, stress are increasingly complex.Therefore, high-speed EMU axle may be because of tired during military service Labor, bending, torsion or tensile stress etc. and be broken, wherein fatigue fracture is the universal fracture mode of high speed axle.To be true The safe operation of vehicle is protected, high-speed EMU axle must have enough reliability and fatigue safety coefficient.High-speed EMU Axle material is one of key factor for determining axle service life and reliability, therefore, is attached great importance to both at home and abroad to high quick-action The research and development of vehicle group axles steel and the research of fatigue behaviour.
With the fast development of China express railway, the needs of axle of motor train unit are sharply increased, but at present still mainly according to Rely in import, therefore, there is an urgent need to develop the high-strength and high ductilities and the green wood of long-fatigue life suitable for China railways development characteristic Matter axle steel.In recent years, the research and development of antifatigue destruction axle steel have been carried out both at home and abroad.Such as Chinese patent application Antifatigue destruction axle steel in 201110417295.9, still using the high C content thinking of carbon axle steel in tradition, C content (0.42~0.45%) is higher, this so that the toughness of steel is poor, can not meet requirement of the axle of motor train unit to toughness, and antifatigue The limited extent of performance improvement is high.A kind of novel hollow axle steel alloy in Chinese patent application 201210384581.4, Although carbon content is relatively low, there is preferable combination of strength and toughness, fatigue strength is still relatively low.The axle of motor train unit master introduced from Europe The steel alloy EA4T of modifier treatment is used, although giving chemical composition and mechanical property requirements, does not provide crucial heat Treatment process parameter, it is often more important that the alloying element content of the influence quenching degree in steel is relatively low, causes the EMU of big specification Tissue (existing does not allow existing ferrite) and performance (nearly center portion intensity, toughness and fatigue behaviour are relatively low) inside axle is past It is past to be difficult to the requirement for reaching standard.These are restricted in practical applications, more crucially axle steel fatigue resistance The amplitude that can improve is limited, influences its popularization and application.
The content of the invention
For above in the prior art the technical issues of, it is an object of the invention to provide a kind of use of axle of motor train unit containing niobium Steel and its heat treatment process realize 750~900MPa of steel tensile strength, yield strength >=600MPa, -40 DEG C of KV2>=150J, Require excellent anti-fatigue performance simultaneously.Specific technical solution is as follows：
The steel of axle of motor train unit containing niobium, contains C according to weight percent：0.24~0.30, Si：0.20~0.40, Mn： 0.70~1.00, Cr：0.90~1.20, Ni：0.70~1.30, Mo：0.20~0.30, Cu：0.10~0.60, Zr：0.01~ 0.04, Nb：0.015~0.050, Ca：0.001~0.005, P≤0.010, S≤0.008, [N]：0.0040~0.0060, T [O]≤0.0015, Als：0.015~0.045, remaining is Fe and other inevitable impurity；Steel be organized as tempered sorbite+ A small amount of lower bainite, wherein, axle near surface tempered sorbite content is 100%, tempered sorbite content at 1/2 radius of axle 75~85%.
Further, C is contained according to weight percent：0.28, Si：0.37, Mn：0.81, Cr：1.15 Ni：0.81, Mo： 0.27, Cu：0.38, Zr：0.01, Nb：0.046, Ca：0.001, P:0.006, S:0.001, [N]：0.0048, T [O]： 0.0010, Als：0.031, remaining is Fe and other inevitable impurity.
Further, the vertical mixing coefficient of steel can reach：Rm：750MPa~900MPa, ReLOr Rp0.2>=600MPa, A >=18%, Z >=40%, -40 DEG C of impacts of collision absorb work(KV2≥150J；Fracture toughness KQValue >=120MPam1/2；Smooth examination The endurance limit under rotating bending R of samplefL>=375MPa, the endurance limit under rotating bending R of notched specimenfE>=310MPa, notch sensitive Property RfL/RfE≤1.15；Interference volume is Fretting Fatigue Limit >=215MPa of 0.04mm samples；Salt air corrosion 14 cycles cycle examination The corrosion fatigue limit of sample is >=275MPa；The autstenitic grain size of steel is more than or equal to 8.0 grades.
The above-mentioned steel heat treatment process of axle of motor train unit containing niobium, includes the following steps：
(1) normalizing：Niobium high-speed EMU axles steel will be contained and be heated to 870~900 DEG C of temperature, heat and protect in the temperature section The warm time is calculated by 1.2~1.7min/mm, air-cooled；
(2) quench：Niobium high-speed EMU axles steel will be contained and be heated to 860~890 DEG C of temperature, heat and protect in the temperature section The warm time is calculated by 1.5~2.0min/mm, then carries out water quenching and oil cooling；
(3) it is tempered：Niobium high-speed EMU axles steel will be contained and be heated to 620~680 DEG C of temperature, heat and protect in the temperature section The warm time is calculated by 2~2.5min/mm, is then air-cooled to room temperature.
Further, firing rate is 50~100 DEG C/h in step (1)-(3).
Further, 900 DEG C of temperature is heated to 80 DEG C/h in step (1), heating and thermal insulation time 300min is air-cooled.
Further, 870 DEG C of temperature is heated to 80 DEG C/h in step (2), heating and thermal insulation time 270min is then, first The quick water cooling of underwater water-spraying is carried out to axle by nozzle in quenching tank, until axle surface temperature is down to 630 DEG C, after by vehicle Axis takes out from water, and cooling dipped in oil is until room temperature.
Further, 650 DEG C of temperature is heated to 80 DEG C/h in step (3), heating and thermal insulation time 420min is air-cooled.
Further, the quick water cooling of underwater water-spraying is first carried out to axle by nozzle in quenching tank in step (2), until Axle surface temperature is down to 600~650 DEG C, after axle is taken out from water, cooling dipped in oil is until room temperature；And/or water cooling Cooling velocity control in 1.5~2.5 DEG C/s.
Further, it is applied in the axles steel production technology of high-speed EMU containing niobium, which includes the following steps： Electric arc furnaces or converter smelting → LF stoves refining → RH or VD vacuum outgas → continuous casting → heating strand stove heat → axle blank rolling → axle blank forging → blank axle is rough turn → the neat end face processing of axle → normalizing+quenching (water quenching+oil cooling)+high tempering heat at Reason, alternatively, normalizing+quenched (quenching+high tempering) heat treatment → axle outer circle finish turning processing → axle internal bore boring processing → Cylindricalo grinding → flaw detection.
Compared with currently available technology, chemical composition using the present invention, technological process and heat treatment process technological parameter The axles steel of high-speed EMU containing niobium of production, the vertical mixing coefficient for measuring steel can reach：Rm：750MPa~900MPa, ReLOr Rp0.2>=600MPa, A >=18%, Z >=40%, -40 DEG C of impacts of collision absorb work(KV2≥150J；Fracture toughness KQValue >= 120MPa·m1/2；The endurance limit under rotating bending R of SpecimensfL>=375MPa, the endurance limit under rotating bending of notched specimen RfE>=310MPa, notch sensitivity RfL/RfE≤1.15；Interference volume is Fretting Fatigue Limit >=215MPa of 0.04mm samples；Salt The corrosion fatigue limit of 14 Xun Huan cycle sample of mist corrosion is >=275MPa；The autstenitic grain size of steel is more than or equal to 8.0 grades； Steel is organized as tempered sorbite after high-speed EMU axle " normalizing+quenched (quenching+high tempering) " heat treatment+shellfish is descended on a small quantity Family name's body, wherein, axle near surface tempered sorbite content is 100%, at 1/2 radius of axle tempered sorbite content 75~ 85%.
Specific embodiment
The present invention will be described in detail below, is a kind of preferred embodiment in numerous embodiments of the present invention.
In a preferred embodiment, the steel of axle of motor train unit containing niobium contains C according to weight percent：0.24~0.30, Si：0.20~0.40, Mn：0.70~1.00, Cr：0.90~1.20, Ni：0.70~1.30, Mo：0.20~0.30, Cu：0.10 ~0.60, Zr：0.01~0.04, Nb：0.015~0.050, Ca：0.001~0.005, P≤0.010, S≤0.008, [N]： 0.0040~0.0060, T [O]≤0.0015, Als：0.015~0.045, remaining is Fe and other inevitable impurity；It is described Steel is organized as tempered sorbite+a small amount of lower bainite, wherein, axle near surface tempered sorbite content is 100%, axle 1/ Tempered sorbite content is 75~85% at 2 radiuses；Heat treatment process includes the following steps：(1) normalizing：The high quick-action of niobium will be contained Vehicle group axles steel is heated to 870~900 DEG C of temperature, is calculated in the temperature section heating and thermal insulation time by 1.2~1.7min/mm, It is air-cooled；(2) quench：Niobium high-speed EMU axles steel will be contained and be heated to 860~890 DEG C of temperature, in the temperature section heating and thermal insulation Time is calculated by 1.5~2.0min/mm, then carries out water quenching and oil cooling；(3) it is tempered：Niobium high-speed EMU axles steel will be contained 620~680 DEG C of temperature is heated to, is calculated in the temperature section heating and thermal insulation time by 2~2.5min/mm, is then air-cooled to room temperature.
In a further advantageous embodiment, following scheme may be employed：The technical solution adopted in the present invention is：(1) fit When reducing the C element content in traditional carbon axle, improve the toughness and plasticity of steel；(2) Ni, Cu element is added into steel to change The quenching degree and corrosion resistance of kind steel, and micro Zr, Nb, [N] element are added in crystal grain thinning, it is special so as to improve the toughness of steel It is low-temperature flexibility, and improves the intensity of steel and toughness cooperation, improves the anti-fatigue performance of steel；(3) suitable Ca elements are added in, it is right Field trash in steel carries out denaturation treatment, while the stringent content for controlling impurity element T [O], P, S etc. in steel, further to carry The anti-fatigue performance of Gao Gang.The present invention's it is critical that optimizing components adjustment has organically been combined with metallurgical quality control Come, while high intensity is obtained, obtain excellent antifatigue destructive characteristics and relatively low cost.
The specific chemical composition (weight %) of steel is as follows：C：0.24~0.30, Si：0.20~0.40, Mn：0.70~ 1.00 Cr：0.90~1.20, Ni：0.70~1.30, Mo：0.20~0.30, Cu：0.10~0.60, Zr：0.01~0.04, Nb：0.015~0.050, Ca：0.001~0.005, P≤0.010, S≤0.008, [N]：0.0040~0.0060, T [O]≤ 0.0015, Als：0.015~0.045, remaining is Fe and other inevitable impurity.
The effect of above-mentioned each element and proportioning are according to as follows：
C：C element is necessary to axle steel obtains high intensity, hardness.C content in traditional axle steel is higher, such as mesh Carbon content in preceding lorry axle steel LZ50 is 0.50%.Although high C content is favourable to intensity, hardness of steel etc., But it is totally unfavorable to the plasticity and toughness of steel, and make yield tensile ratio reduce, Decarburization Sensitivity increase, deteriorate steel anti-fatigue performance and Processing performance.Therefore the appropriate C content reduced in steel, is controlled below 0.30%.However, it is after quenching and high tempering High intensity and necessary fatigue behaviour needed for obtaining, C content must be more than 0.24%, thus C content preferably controls and is 0.24~0.30%.
Si：Si is main deoxidant element in steel, has very strong solution strengthening effect, but Si too high levels will make steel Plasticity and toughness decline, the activity increase of C, and decarburization and graphitization of the steel in rolling and heat treatment process is promoted to be inclined to, and Make smelting difficult and easily form field trash, deteriorate the anti-fatigue performance of steel.Therefore it is 0.20~0.40% to control Si contents.
Mn：Mn is the effective element of deoxidation and desulfurization, can also improve the quenching degree and intensity of steel, and content is less than 0.70% When, it is difficult to it functions as described above.But when quenching temper, Mn and P have strong grain boundary cosegregation tendency, promote temper brittleness, Deteriorate the toughness of steel, thus control Mn contents below 1.00%.
Cr：Cr can effectively improve the quenching degree and resistance to tempering of steel, to obtain required high intensity；Cr may be used also simultaneously The activity of C is reduced, the steel surface decarburizing tendency in heating, rolling and heat treatment process can be reduced, has utilization to obtain high resist Fatigue behaviour.But too high levels can deteriorate the toughness of steel, thus it is 0.90~1.20% to control Cr contents.
Ni：Ni can improve the quenching degree of steel, the toughness of corrosion resistance and guarantee steel at low temperature.In view of economy, control Ni contents are 0.80~1.30%.
Mo：Effects of the Mo in steel predominantly improves quenching degree, improves resistance to tempering and prevent temper brittleness.In addition, Mo The reasonable cooperation of element and Cr elements can make quenching degree and resistance to tempering be improved significantly.Mo contents are too low, and above-mentioned effect has Limit, Mo too high levels, then above-mentioned effect saturation, and improve the cost of steel.Therefore, it is 0.20~0.30% to control Mo contents.
Cu：Cu is similar to Ni in terms of solution strengthening, raising quenching degree.Meanwhile addition copper can also improve steel in steel Corrosion fatigue resistant performance, because tiny Cu precipitations have blocked the formation of the initial stage vein texture of fatigue, and copper is precipitated Object has good plasticity, can hinder the extension of fatigue crack；In addition, Cu also improves, steel corrosion resistance acts on；So as to Improve the corrosion fatigue strength of steel.But Cu too high levels, steel easily cause hot-short in heating rolling or forging process.Synthesis is examined Consider, range-controllable system is 0.10~0.60%.
Zr：Adding in a small amount of zirconium has degassing, purification and Grain refinement, is conducive to improve the low temperature impact properties of steel and strong Degree, fatigue behaviour index.Consider, range-controllable system is 0.010~0.040%.
Nb：Nb is mainly shown as crystal grain refinement, precipitation strength and phase transformation strengthening to the Strengthening and Toughening effect of axle steel.Nb is in steel In to replace solute atoms presence, Nb atomic ratio iron atom sizes are big, the segregation easily on dislocation line, dislocation climb generated strong Effect of dragging, be suppressed Recrystallization nucleation, to recrystallization have strong interception, improve tying again for austenite Brilliant temperature, so as to achieve the purpose that fining austenite grains, crystal grain refinement can not only improve the obdurability of steel, and improve steel The cryogenic property of material.But its is expensive.Consider, the range-controllable system of Nb is 0.015%~0.050%.
Ca：Ca plays an important role of deoxidization desulfuration and to non-metallic inclusion denaturation treatment, so as to improve the toughness of steel and anti- Fatigue behaviour.Ca contents do not have above-mentioned effect less than 0.001%, but content is more than 0.005%, then add in it is extremely difficult, and It is mingled with object amount to increase.It is 0.001~0.005% thus to control Ca contents.
P：P can form microsegregation in solidification of molten steel, and then when austenitizing temperature heats, segregation in crystal boundary, makes steel Brittleness significantly increase, so control P content below 0.012%.
S：Inevitable impurity in steel forms MnS and is mingled with and can deteriorate the toughness of steel and antifatigue in crystal boundary segregation Performance, thus its content is controlled below 0.008%.
[N]：In the presence of having V, Al, Nb, Ti etc. in steel, nitrogen can form carbonitride with them, can prevent austenite again Crystallization, crystal grain thinning improves the toughness of steel, and can improve the intensity of steel.If nitrogen content is higher, can exist with solid solution condition, from And deteriorate the toughness plasticity index of steel.Consider, range-controllable system is 0.0040~0.0060%.
T[O]：Oxygen forms various oxides in steel and is mingled with.It is easy at these oxide places of being mingled under the action of stress Stress concentration is generated, causes the germinating of micro-crack, so as to deteriorate the mechanical property of steel particularly toughness and anti-fatigue performance.Cause This, must take measures to reduce its content as far as possible in metallurgical production.In view of economy, control its content 0.0015% with Under.
The axles steel technological process of production of high-speed EMU containing niobium of the invention is：Electric arc furnaces or converter smelting → LF stoves refining → RH or VD vacuum outgas → continuous casting → heating strand stove heat → axle blank rolling → axle blank forging → blank axle is rough turn The neat end face processing of → axle → normalizing+quenching (water quenching+oil cooling)+high tempering heat treatment → axle outer circle finish turning processing → axle Internal bore boring processing → cylindricalo grinding → flaw detection.
Crucial heat treatment process step of the invention is as follows：
(1) normalizing：It is 200mm by maximum gauge, the axles steel of high-speed EMU containing the niobium heating of length up to 2200mm (add Thermal velocity is 50~100 DEG C/h) to 870~900 DEG C of temperature, in the temperature section heating and thermal insulation time based on 1.2~1.7min/mm It calculates, it is air-cooled.Crystal grain has not only been refined after normalizing, and has improved the inhomogeneities of tissue, has been done for subsequent final heat treatment Good tissue prepares.
(2) (water quenching+oil cooling) is quenched：By maximum gauge be 200mm, length reaches the axle of high-speed EMU containing vanadium of 2200mm (firing rate is 50~100 DEG C/h) is heated with steel to 860~890 DEG C of temperature, the temperature section heating and thermal insulation time by 1.5~ 2.0min/mm is calculated, and then, first carries out underwater water-spraying quick water cooling (cooling velocity control to axle by nozzle in quenching tank System is in 1.5~2.5 DEG C/s), until axle surface temperature is down to 600~650 DEG C, after axle is taken out from water, it is dipped in oil Cooling is until room temperature.
(3) it is tempered：It is 200mm by maximum gauge, the axles steel of high-speed EMU containing the niobium heating of length up to 2200mm (add Thermal velocity is 50~100 DEG C/h) to 620~680 DEG C of temperature, in the temperature section heating and thermal insulation time based on 2~2.5min/mm It calculates, is then air-cooled to room temperature.By tempering, the metallographic structure of uniform fine and closely woven tempered sorbite+lower bainite can be obtained, so as to Obtain good toughness plasticity and suitable intensity index.
In a further advantageous embodiment, following scheme may be employed：The axles steel production technology of high-speed EMU containing niobium Flow is：Electric arc furnaces or converter smelting → LF stoves refining → RH or VD vacuum outgas → continuous casting → heating strand stove heat → axle Base rolling → axle blank forging → blank axle is rough turn → axle neat end face processing → normalizing+quenched (quenching+high tempering) heat Processing → axle outer circle finish turning processing → axle internal bore boring processing → cylindricalo grinding → flaw detection.
The melting chemical composition of present invention high-speed EMU containing niobium axles steel, main heat treatment process parameter and performance Embodiment is as follows：
Heat treatment process step and parameter are：
(1) normalizing：900 DEG C of temperature is heated to 80 DEG C/h, heating and thermal insulation time 300min is air-cooled.
(2) (water quenching+oil cooling) is quenched：870 DEG C of temperature is heated to 80 DEG C/h, heating and thermal insulation time 270min is then, first Carry out the quick water cooling of underwater water-spraying (cooling velocity is controlled in 1.5~2.5 DEG C/s) to axle by nozzle in quenching tank, until Axle surface temperature is down to 630 DEG C, after axle is taken out from water, cooling dipped in oil is until room temperature.
(3) it is tempered：650 DEG C of temperature is heated to 80 DEG C/h, heating and thermal insulation time 420min is air-cooled.
Maximum gauge is Φ 200mm, length reaches the melting chemical composition mass percent of 2200mm high-speed EMU axles (wt%) 1 is shown in Table, performance indicator of the high-speed EMU axle after being heat-treated above is shown in Table 2.
The melting chemical composition mass percent (wt%) of 1 high-speed EMU axle steel of table
Performance indicator after the heat treatment of 2 high-speed EMU axle of table
Performance indicator after the heat treatment of 2 high-speed EMU axle of continued
The present invention has the advantages that intensity is high, anti-fatigue performance is excellent compared with prior art.More than 700MPa can be obtained High intensity, plasticity and toughness is substantially better than business steel, and fatigue limit will be significantly higher than business steel, shows good strong Spend toughness cooperation and excellent anti-fatigue performance.Wherein：Rm：750MPa~900MPa, ReLOr Rp0.2>=600MPa, A >=18%, Z >=40%, -40 DEG C of impacts of collision absorb work(KV2≥150J；Fracture toughness KQValue >=120MPam1/2；The rotation of Specimens Bending fatigue limit RfL>=375MPa, the endurance limit under rotating bending R of notched specimenfE>=310MPa, notch sensitivity RfL/RfE ≤1.15；Interference volume is Fretting Fatigue Limit >=215MPa of 0.04mm samples；Salt air corrosion 14 cycles the corrosion of cycle sample Fatigue limit is >=275MPa；The autstenitic grain size of steel is more than or equal to 8.0 grades；" the normalizing+quenched of high-speed EMU axle Steel is organized as tempered sorbite+a small amount of lower bainite after (quenching+high tempering) " heat treatment, wherein, the tempering of axle near surface Sorbite percentage is 100%, and tempered sorbite content is 75~85% at 1/2 radius of axle.
The present invention is exemplarily described above, it is clear that present invention specific implementation is not subject to the restrictions described above, As long as it employs the various improvement of inventive concept and technical scheme of the present invention progress or not improved directly applies to other fields It closes, within protection scope of the present invention.

Claims (3)

1. the steel heat treatment process of axle of motor train unit containing niobium, which is characterized in that the steel of axle of motor train unit containing niobium, according to weight percent Than containing C：0.28, Si：0.37, Mn：0.81, Cr：1.15 Ni：0.81, Mo：0.27, Cu：0.38, Zr：0.01, Nb： 0.046, Ca：0.001, P:0.006, S:0.001, [N]：0.0048, T [O]：0.0010, Als：0.031, remaining is Fe and its Its inevitable impurity；The steel is organized as tempered sorbite+a small amount of lower bainite, wherein, axle near surface tempering rope Family name's body content is 100%, and tempered sorbite content is 75~85% at 1/2 radius of axle；Include the following steps：
(1) normalizing：Niobium high-speed EMU axles steel will be contained, 900 DEG C of temperature is heated to 80 DEG C/h, be heated to temperature 870~ It 900 DEG C, is calculated in the temperature section heating and thermal insulation time by 1.2~1.7min/mm, heating and thermal insulation time 300min is air-cooled；
(2) quench：Niobium high-speed EMU axles steel will be contained, 870 DEG C of temperature is heated to 80 DEG C/h, and heated and protect in the temperature section The warm time is calculated by 1.5~2.0min/mm, heating and thermal insulation time 270min, and then, elder generation is in quenching tank by nozzle to axle Carry out the quick water cooling of underwater water-spraying, until axle surface temperature is down to 630 DEG C, after axle is taken out from water, it is dipped in oil cold But until room temperature；
(3) it is tempered：Niobium high-speed EMU axles steel will be contained, 650 DEG C of temperature is heated to 80 DEG C/h, and heated and protect in the temperature section The warm time is calculated by 2~2.5min/mm, and heating and thermal insulation time 420min is then air-cooled to room temperature.
2. the steel heat treatment process of axle of motor train unit containing niobium as described in claim 1, which is characterized in that axle of motor train unit containing niobium It can reach with the vertical mixing coefficient of steel steel：Rm：750MPa~900MPa, ReLOr Rp0.2>=600MPa, A >=18%, Z >= 40%, -40 DEG C of impacts of collision absorb work(KV2≥150J；Fracture toughness KQValue >=120MPam1/2；The rotoflector of Specimens Fatigue limit RfL>=375MPa, the endurance limit under rotating bending R of notched specimenfE>=310MPa, notch sensitivity RfL/RfE≤ 1.15；Interference volume is Fretting Fatigue Limit >=215MPa of 0.04mm samples；The corrosion that salt air corrosion 14 cycles cycle sample is tired The labor limit is >=275MPa；The autstenitic grain size of steel is more than or equal to 8.0 grades.
3. the steel heat treatment process of axle of motor train unit containing niobium as described in claim 1, which is characterized in that it is applied to containing niobium at a high speed With in steel production technology, which includes the following steps axle of motor train unit：Electric arc furnaces or converter smelting → LF stoves refining → RH or VD vacuum outgas → continuous casting → heating strand stove heat → axle blank rolling → axle blank forging → blank axle is rough turn → axle Neat end face processing → normalizing+quenching:Water quenching+oil cooling+high tempering heat treatment → axle outer circle finish turning processing → axle endoporus boring Cut processing → cylindricalo grinding → flaw detection.
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