CN105838988A - Niobium-containing steel for axles of motor train unit and heat treatment process of niobium-containing steel - Google Patents

Niobium-containing steel for axles of motor train unit and heat treatment process of niobium-containing steel Download PDF

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CN105838988A
CN105838988A CN201610416945.0A CN201610416945A CN105838988A CN 105838988 A CN105838988 A CN 105838988A CN 201610416945 A CN201610416945 A CN 201610416945A CN 105838988 A CN105838988 A CN 105838988A
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steel
niobium
axle
axletree
percent
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CN105838988B (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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    • 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 invention relates to niobium-containing steel for axles of a motor train unit and a heat treatment process of the niobium-containing steel. The niobium-containing steel is prepared from the following components in percentage by weight: 0.24 to 0.30 percent of C, 0.20 to 0.40 percent of Si, 0.70 to 1.00 percent of Mn, 0.90 to 1.20 percent of Cr, 0.70 to 1.30 percent of Ni, 0.20 to 0.30 percent of Mo, 0.10 to 0.60 percent of Cu, 0.01 to 0.04 percent of Zr, 0.015 to 0.050 percent of Nb, 0.001 to 0.005 percent of Ca, smaller than or equal to 0.010 percent of P, smaller than or equal to 0.008 percent of S, 0.0040 to 0.0060 percent of [N], smaller than or equal to 0.015 percent of T[O], 0.015 to 0.045 percent of Als, and the balance being Fe and inevitable impurities. The structure of the steel is tempered sorbate plus a little part of bainite, wherein the content of the tempered sorbate on an axle near surface is 100 percent, and the content of the tempered sorbate at one second radius of an axle is 75 to 85 percent. After special treatment, the plasticity and the toughness of the steel are remarkably superior to those of commercial steel, and the fatigue limit of the steel is significantly higher than that of the commercial steel; and the steel shows good matching of strength and toughness and excellent fatigue resistance.

Description

Containing niobium axle of motor train unit steel and Technology for Heating Processing thereof
Technical field
The present invention relates to field of alloy steel, be specifically related to tensile strength 750～900MPa, yield strength >=600MPa ,-40 DEG C of KV2 >=150J, requires EMU axles steel and the Technology for Heating Processing thereof with the anti-fatigue performance of excellence simultaneously.
Background technology
Axletree is to relate to one of safe most important motion and load bearing component in various vehicle.Owing to axletree subjects dynamic loading, Stress is more complicated, such as bending load, torsional load, bending combined load, and by certain impact, particularly at a high speed Axle of motor train unit, its stress is increasingly complex.Therefore, EMU axletree under arms during may because of tired, Bending, reverse or tensile stress etc. and rupture, wherein fatigue fracture is the universal fracture mode of high speed axletree.For guaranteeing car Safe operation, EMU axletree must have enough reliabilities and fatigue safety coefficient.Motor train unit axial wood Material is one of key factor determining axletree service life and reliability, therefore, attaches great importance to both at home and abroad EMU axletree With research and development and the research of fatigue behaviour of steel.
Along with the fast development of China Express Railway, the needs of axle of motor train unit are sharply increased, but still depend at present into Mouthful, therefore, it is applicable to the high-strength and high ductility of China railways development characteristic and the plastics on new materials axle steel of long-fatigue life in the urgent need to exploitation. In recent years, carry out resisting fatigue both at home and abroad and destroy the research and development of axle steel.In Chinese patent application 201110417295.9 Resisting fatigue destroys axle steel, still uses the high C content thinking of carbon axle steel in tradition, and C content (0.42～0.45%) is higher, This makes the toughness of steel poor, it is impossible to meet the axle of motor train unit requirement to toughness, and the limited extent that anti-fatigue performance improves is high. A kind of novel hollow axletree steel alloy in Chinese patent application 201210384581.4, although carbon content is relatively low, has preferably Combination of strength and toughness, but fatigue strength is the most relatively low.The axle of motor train unit introduced from Europe mainly uses the steel alloy of modifier treatment EA4T, although give chemical composition and mechanical property requirements, but do not provide crucial heat treatment process parameter, it is often more important that The alloying element content affecting quenching degree in steel is on the low side, causes the tissue within the axle of motor train unit of big specification (to exist and do not allow Exist ferrite) and performance (nearly heart portion intensity, toughness and fatigue behaviour are on the low side) be often difficult to the requirement of the standard that reaches.This Being restricted the most in actual applications a bit, the amplitude that the most crucially axle steel anti-fatigue performance improves is the most limited, affects it Popularization and application.
Summary of the invention
For above technical problem of the prior art, it is an object of the invention to provide a kind of containing niobium axle of motor train unit steel and Technology for Heating Processing, it is achieved steel tensile strength 750～900MPa, yield strength >=600MPa ,-40 DEG C of KV2>=150J, wants simultaneously Seek the anti-fatigue performance with excellence.Concrete technical scheme is as follows:
Containing niobium axle of motor train unit steel, contain C:0.24～0.30 according to percentage by weight, 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 for Fe with other inevitable impurity；Steel be organized as tempered sorbite + a small amount of lower bainite, wherein, axletree near surface tempered sorbite content is 100%, and at axletree 1/2 radius, tempered sorbite contains Amount is 75～85%.
Further, contain C:0.28, Si:0.37, Mn:0.81, Cr:1.15, Ni:0.81 according to percentage by weight, 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 merit KV2≥150J；Fracture toughness KQValue >=120MPa m1/2；The rotation of Specimens is curved Bent fatigue limit RfL>=375MPa, the endurance limit under rotating bending R of notched specimenfE>=310MPa, notch sensitivity RfL/RfE≤ 1.15；The magnitude of interference is the Fretting Fatigue Limit >=215MPa of 0.04mm sample；The corrosion that salt air corrosion 14 circulates cycle sample is tired The labor limit is >=275MPa；The autstenitic grain size of steel is more than or equal to 8.0 grades.
Above-mentioned containing niobium axle of motor train unit steel heat treatment process, comprise the steps:
(1) normalizing: niobium EMU axles steel will be contained and be heated to temperature 870～900 DEG C, and press in this temperature section heating and thermal insulation time 1.2～1.7min/mm calculates, air cooling；
(2) quenching: niobium EMU axles steel will be contained and be heated to temperature 860～890 DEG C, and press in this temperature section heating and thermal insulation time 1.5～2.0min/mm calculate, and carry out shrend subsequently and oil is cold；
(3) tempering: niobium EMU axles steel will be contained and be heated to temperature 620～680 DEG C, and press in this temperature section heating and thermal insulation time 2～2.5min/mm calculate, and air cooling is to room temperature subsequently.
Further, in step (1)-(3), firing rate is 50～100 DEG C/h.
Further, step (1) is heated to temperature 900 DEG C, heating and thermal insulation time 300min, air cooling with 80 DEG C/h.
Further, step (2) is heated to temperature 870 DEG C with 80 DEG C/h, heating and thermal insulation time 270min, subsequently, First in quenching tank, by nozzle, axletree is carried out the quick water-cooled of underwater water-spraying, until axletree surface temperature is down to 630 DEG C, after Being taken out from water by axletree, cooling dipped in oil is until room temperature.
Further, step (3) is heated to temperature 650 DEG C, heating and thermal insulation time 420min, air cooling with 80 DEG C/h.
Further, step (2) first carries out the quick water-cooled of underwater water-spraying by nozzle to axletree in quenching tank, until Axletree surface temperature is down to 600～650 DEG C, after axletree is taken out from water, cooling dipped in oil is until room temperature；And/or, The rate of cooling of water-cooled controls at 1.5～2.5 DEG C/s.
Further, it is applied to containing in niobium EMU axles steel production technology, and this technique comprises the steps: electricity Arc stove or converter smelting → LF stove refine → RH or VD vacuum outgas → continuous casting → strand heating furnace heating → axle blank rolling → Axle blank forging → blank axletree is rough turn → axletree neat end face processing → normalizing+quenching (shrend+oil is cold)+high tempering heat at Reason, or, normalizing+quenched (quenching+high tempering) heat treatment → axletree outer circle finish turning processing → axletree internal bore boring processing → cylindricalo grinding → flaw detection.
Compared with currently available technology, the chemical composition of the present invention, technological process and Technology for Heating Processing technological parameter is used to produce Containing niobium EMU axles steel, the vertical mixing coefficient measuring steel can reach: Rm: 750MPa～900MPa, ReL Or Rp0.2>=600MPa, A >=18%, Z >=40% ,-40 DEG C of impacts of collision absorb merit 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；The magnitude of interference is the Fretting Fatigue Limit >=215MPa of 0.04mm sample； It is >=275MPa that salt air corrosion 14 circulates the corrosion fatigue limit of cycle sample；The autstenitic grain size of steel is more than or equal to 8.0 Level；After EMU axletree " normalizing+quenched (quenching+high tempering) " heat treatment steel be organized as tempered sorbite+ A small amount of lower bainite, wherein, axletree near surface tempered sorbite content is 100%, tempered sorbite at axletree 1/2 radius Content is 75～85%.
Detailed description of the invention
Describing the present invention below, it is a kind of preferred embodiment in numerous embodiments of the present invention.
In a preferred embodiment, C:0.24～0.30, Si are contained containing niobium axle of motor train unit steel according to percentage by weight: 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 for Fe with other inevitable impurity；Described Steel be organized as tempered sorbite+a small amount of lower bainite, wherein, axletree near surface tempered sorbite content is 100%, axletree 1/2 At radius, tempered sorbite content is 75～85%；Technology for Heating Processing, comprises the steps: (1) normalizing: will contain niobium high speed motor car Group axles steel is heated to temperature 870～900 DEG C, in this temperature section heating and thermal insulation time by 1.2～1.7min/mm calculating, air cooling； (2) quenching: niobium EMU axles steel will be contained and be heated to temperature 860～890 DEG C, and press in this temperature section heating and thermal insulation time 1.5～2.0min/mm calculate, and carry out shrend subsequently and oil is cold；(3) tempering: niobium EMU axles steel will be contained and be heated to Temperature 620～680 DEG C, in this temperature section heating and thermal insulation time by 2～2.5min/mm calculating, air cooling is to room temperature subsequently.
In a further advantageous embodiment, following scheme can be used: the technical solution adopted in the present invention is: (1) suitably drops C element content in low tradition carbon axle, improves toughness and the plasticity of steel；(2) in steel, add Ni, Cu element to improve The quenching degree of steel and corrosion resistance, and add the Zr of trace, Nb, [N] element with crystal grain thinning, thus the toughness improving steel is special It is low-temperature flexibility, and improves intensity and the toughness cooperation of steel, improve the anti-fatigue performance of steel；(3) appropriate Ca element is added, Field trash in steel carries out degenerative treatments, and impurity element T [O], the content of P, S etc. in the strictest control steel, with further Improve the anti-fatigue performance of steel.The present invention's it is critical that adjust optimizing components and control organically to be combined with metallurgical quality Come, while obtaining high intensity, it is thus achieved that excellent resisting fatigue 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 for Fe with other inevitable impurity.
The effect of above-mentioned each element and proportioning are according to as follows:
C:C element is that axle steel obtains necessary to high intensity, hardness.C content in tradition axle steel is higher, as at present Carbon content in lorry axle steel LZ50 is 0.50%.Although high C content is favourable to the intensity of steel, hardness etc., but Plasticity and toughness to steel are totally unfavorable, and make yield tensile ratio reduction, Decarburization Sensitivity increase, and deteriorate the anti-fatigue performance of steel and add Work performance.The most suitably reduce the C content in steel, controlled below 0.30%.But, after quenching and high tempering it is High intensity needed for obtaining and necessary fatigue behaviour, C content must more than 0.24%, thus C content preferably control be 0.24～ 0.30%.
Si:Si is deoxidant element main in steel, has the strongest solution strengthening effect, but Si too high levels will make moulding of steel Property and toughness decline, the activity increase of C, promote steel decarburization in rolling and heat treatment process and graphitization tendency, and make Smelt difficulty and be easily formed field trash, deteriorating the anti-fatigue performance of steel.Therefore controlling Si content is 0.20～0.40%.
Mn:Mn is the effective element of deoxidation and desulfurization, it is also possible to improve quenching degree and the intensity of steel, when content is less than 0.70%, It is difficult to function as described above.But during hardened steel tempering, Mn and P has strong grain boundary cosegregation to be inclined to, and promotes temper brittleness, dislikes Change the toughness of steel, thus control Mn content below 1.00%.
Cr:Cr can be effectively improved quenching degree and the resistance to tempering of steel, the high intensity needed for obtaining；Cr also can drop simultaneously The activity of low C, it is possible to decrease heat, roll and steel surface decarburizing tendency in heat treatment process, have utilize obtain high anti-tired Labor performance.But too high levels can deteriorate the toughness of steel, thus controlling Cr content is 0.90～1.20%.
Ni:Ni can improve the quenching degree of steel, corrosion resistance and guarantee steel toughness at low temperatures.In view of economy, control Ni Content is 0.80～1.30%.
Mo:Mo effect in steel predominantly improves quenching degree, improves resistance to tempering and prevent temper brittleness.Additionally, Mo element Quenching degree and resistance to tempering can be made to be improved significantly with the reasonable coordination of Cr element.Mo content the most above-mentioned too low limited use, Mo too high levels, the most above-mentioned effect is saturated, and improves the cost of steel.Therefore, controlling Mo content is 0.20～0.30%.
Cu:Cu is similar to Ni in terms of solution strengthening, raising quenching degree.Meanwhile, steel adds copper and also can improve the anti-of steel Corrosion Fatigue Properties, because tiny Cu precipitation has blocked the formation of the initial stage vein texture of fatigue, and copper precipitate There is good plasticity, the extension of fatigue crack can be hindered；The steel corrosion resistance effect it addition, Cu also improves；Thus carry The corrosion fatigue strength of Gao Gang.But Cu too high levels, steel easily causes hot-short in heating rolling or forging process.Consider, Range-controllable system is 0.10～0.60%.
Zr: adding a small amount of zirconium has degassing, purification and Grain refinement, be conducive to improving the low temperature impact properties of steel and intensity, Fatigue behaviour index.Considering, range-controllable system is 0.010～0.040%.
Nb:Nb mainly shows as crystal grain refinement, precipitation strength and phase transformation strengthening to the Strengthening and Toughening effect of axle steel.Nb in steel with Displacement solute atoms exists, and Nb atomic ratio iron atom size is big, easily segregation on dislocation line, and dislocation climb is produced strong dragging Drag effect, make Recrystallization nucleation be suppressed, recrystallization is had strong interception, improve the recrystallization temperature of austenite Degree, thus reach the purpose of fining austenite grains, crystal grain refinement can not only improve the obdurability of steel, and improves steel Cryogenic property.But it is expensive.Considering, the range-controllable system of Nb is 0.015%～0.050%.
Ca:Ca has deoxidization desulfuration and the effect to non-metallic inclusion degenerative treatments, thus improves toughness and the fatigue resistance of steel Energy.Ca content does not has above-mentioned effect less than 0.001%, but content is more than 0.005%, then add extremely difficult, and field trash Amount increases.Thus controlling Ca content is 0.001～0.005%.
P:P can form microsegregation when solidification of molten steel, and when austenitizing temperature heats, segregation, at crystal boundary, makes the crisp of steel subsequently Property significantly increase, so control P content below 0.012%.
S: inevitable impurity in steel, forms MnS and is mingled with and can deteriorate toughness and the anti-fatigue performance of steel at Grain Boundary Segregation, Thus control its content below 0.008%.
[N]: in the presence of having V, Al, Nb, Ti etc. in steel, nitrogen can form carbonitride with them, austenite can be stoped to tie again Crystalline substance, crystal grain thinning, improves the toughness of steel, and can improve the intensity of steel.As nitrogen content is higher, can exist with solid solution condition, from And deteriorate the toughness plasticity index of steel.Considering, range-controllable system is 0.0040～0.0060%.
T [O]: oxygen forms various oxide in steel and is mingled with.Under the effect of stress, easily produce at these oxide places of being mingled with Stress is concentrated, and causes the germinating of micro-crack, thus deteriorates mechanical property particularly toughness and the anti-fatigue performance of steel.Therefore, exist Metallurgical production must take measures reduce its content as far as possible.In view of economy, control its content below 0.0015%.
Present invention EMU axles steel technological process of production Han niobium is: electric arc furnace or converter smelting → LF stove refine → RH or VD vacuum outgas → continuous casting → strand heating furnace heating → axle blank rolling → axle blank forging → blank axletree is rough turn → and axletree holds together Face processing → normalizing+quenching (shrend+oil is cold)+high tempering heat treatment → axletree outer circle finish turning processing → axletree internal bore boring processing → cylindricalo grinding → flaw detection.
The Technology for Heating Processing step of present invention key is as follows:
(1) normalizing: by maximum gauge be 200mm, length reach 2200mm containing niobium EMU axles steel heating (add Thermal velocity is 50～100 DEG C/h) to temperature 870～900 DEG C, in this temperature section heating and thermal insulation time by 1.2～1.7min/mm calculating, Air cooling.After normalizing, not only refine crystal grain, and improved the inhomogeneities of tissue, carry out group for finished heat treatment subsequently Knit preparation.
(2) quenching (shrend+oil is cold): by maximum gauge be 200mm, length reach 2200mm containing vanadium EMU axletree With steel heating (firing rate is 50～100 DEG C/h) to temperature 860～890 DEG C, press in this temperature section heating and thermal insulation time 1.5～2.0min/mm calculate, and subsequently, (cooling is fast first by nozzle, axletree to be carried out the quick water-cooled of underwater water-spraying in quenching tank Degree controls at 1.5～2.5 DEG C/s), until axletree surface temperature is down to 600～650 DEG C, after axletree is taken out from water, immerse oily Middle cooling is until room temperature.
(3) tempering: by maximum gauge be 200mm, length reach 2200mm containing niobium EMU axles steel heating (add Thermal velocity is 50～100 DEG C/h) to temperature 620～680 DEG C, in this temperature section heating and thermal insulation time by 2～2.5min/mm calculating, Air cooling is to room temperature subsequently.Through tempering, the metallographic structure of uniform fine and closely woven tempered sorbite+lower bainite can be obtained, thus can obtain Good toughness plasticity and suitably intensity index.
In a further advantageous embodiment, following scheme can be used: the EMU axles steel technological process of production containing niobium is: Electric arc furnace or converter smelting → LF stove refine → RH or VD vacuum outgas → continuous casting → strand heating furnace heating → axle blank rolling → Axle blank forging → blank axletree is rough turn → axletree neat end face processing → normalizing+quenched (quenching+high tempering) heat treatment → axletree Outer circle finish turning processing → axletree internal bore boring processing → cylindricalo grinding → flaw detection.
The present invention is containing the embodiment of the melting chemical composition of niobium EMU axles steel, main heat treatment process parameter and performance As follows:
Technology for Heating Processing step and parameter be:
(1) normalizing: be heated to temperature 900 DEG C, heating and thermal insulation time 300min, air cooling with 80 DEG C/h.
(2) quenching (shrend+oil is cold): be heated to temperature 870 DEG C with 80 DEG C/h, heating and thermal insulation time 270min, subsequently, First in quenching tank, by nozzle, axletree is carried out the quick water-cooled of underwater water-spraying (rate of cooling controls at 1.5～2.5 DEG C/s), until Axletree surface temperature is down to 630 DEG C, after axletree is taken out from water, cooling dipped in oil is until room temperature.
(3) tempering: be heated to temperature 650 DEG C, heating and thermal insulation time 420min, air cooling with 80 DEG C/h.
Maximum gauge is Φ 200mm, length reaches the melting chemical composition mass percent (wt%) of 2200mm EMU axletree Being shown in Table 1, EMU axletree performance indications after above heat treatment are shown in Table 2.
The melting chemical composition mass percent (wt%) of table 1 EMU axletree steel
Performance indications after table 2 EMU axletree heat treatment
Performance indications after continued 2 EMU axletree heat treatment
The present invention compared with prior art has the advantage that intensity is high, anti-fatigue performance is excellent.Can obtain more than 700MPa's High intensity, its plasticity and toughness is substantially better than business steel, its fatigue limit business to be significantly higher than steel, presents good strong Degree toughness coordinates and the anti-fatigue performance of excellence.Wherein: Rm: 750MPa～900MPa, ReLOr Rp0.2>=600MPa, A >=18%, Z >=40% ,-40 DEG C of impacts of collision absorb merit KV2≥150J；Fracture toughness KQValue >=120MPa m1/2；The rotation of Specimens Turn bending fatigue limit RfL>=375MPa, the endurance limit under rotating bending R of notched specimenfE>=310MPa, notch sensitivity RfL/RfE≤1.15；The magnitude of interference is the Fretting Fatigue Limit >=215MPa of 0.04mm sample；Salt air corrosion 14 circulates 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；EMU axletree is " just Fire+quenched (quenching+high tempering) " steel is organized as tempered sorbite+a small amount of lower bainite, wherein, axletree after heat treatment Near surface tempered sorbite content is 100%, and at axletree 1/2 radius, tempered sorbite content is 75～85%.
Above the present invention is exemplarily described, it is clear that the present invention implements and is not subject to the restrictions described above, as long as Have employed method design and the various improvement that carry out of technical scheme of the present invention, or the most improved directly apply to other occasion , all within protection scope of the present invention.

Claims (10)

1. the axle of motor train unit steel Han niobium, it is characterised in that contain C:0.24～0.30 according to percentage by weight, 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；Institute That states steel is organized as tempered sorbite+a small amount of lower bainite, and wherein, axletree near surface tempered sorbite content is 100%, axletree At 1/2 radius, tempered sorbite content is 75～85%.
2. the axle of motor train unit steel Han niobium as claimed in claim 1, it is characterised in that contain C according to percentage by weight: 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, its Remaining is Fe and other inevitable impurity.
3. the axle of motor train unit steel Han niobium as claimed in claim 1 or 2, it is characterised in that longitudinal mechanical property of steel Can reach: Rm: 750MPa～900MPa, ReLOr Rp0.2>=600MPa, A >=18%, Z >=40% ,-40 DEG C of impacts of collision are inhaled Receive merit KV2≥150J；Fracture toughness KQValue >=120MPa m1/2；The endurance limit under rotating bending R of SpecimensfL>=375MPa, The endurance limit under rotating bending R of notched specimenfE>=310MPa, notch sensitivity RfL/RfE≤1.15；The magnitude of interference is 0.04mm Fretting Fatigue Limit >=the 215MPa of sample；It is >=275MPa that salt air corrosion 14 circulates the corrosion fatigue limit of cycle sample； The autstenitic grain size of steel is more than or equal to 8.0 grades.
4. the axle of motor train unit steel heat treatment process Han niobium as described in claim 1-3, it is characterised in that include walking as follows Rapid:
(1) normalizing: niobium EMU axles steel will be contained and be heated to temperature 870～900 DEG C, and press in this temperature section heating and thermal insulation time 1.2～1.7min/mm calculate, air cooling；
(2) quenching: niobium EMU axles steel will be contained and be heated to temperature 860～890 DEG C, and press in this temperature section heating and thermal insulation time 1.5～2.0min/mm calculate, and carry out shrend subsequently and oil is cold；
(3) tempering: niobium EMU axles steel will be contained and be heated to temperature 620～680 DEG C, and press in this temperature section heating and thermal insulation time 2～2.5min/mm calculate, and air cooling is to room temperature subsequently.
5. the axle of motor train unit steel heat treatment process Han niobium as claimed in claim 4, it is characterised in that step (1)-(3) Middle firing rate is 50～100 DEG C/h.
6. the axle of motor train unit steel heat treatment process Han niobium as described in claim 4 or 5, it is characterised in that step (1) In be heated to temperature 900 DEG C, heating and thermal insulation time 300min, air cooling with 80 DEG C/h.
7. the axle of motor train unit steel heat treatment process Han niobium as described in claim 4-6, it is characterised in that in step (2) It is heated to temperature 870 DEG C, heating and thermal insulation time 270min with 80 DEG C/h, subsequently, in quenching tank, first passes through nozzle to car Axle carries out the quick water-cooled of underwater water-spraying, until axletree surface temperature is down to 630 DEG C, after axletree is taken out from water, immerse oil Middle cooling is until room temperature.
8. the axle of motor train unit steel heat treatment process Han niobium as described in claim 4-7, it is characterised in that in step (3) It is heated to temperature 650 DEG C, heating and thermal insulation time 420min, air cooling with 80 DEG C/h.
9. the axle of motor train unit steel heat treatment process Han niobium as described in claim 4-8, it is characterised in that in step (2) First in quenching tank, by nozzle, axletree is carried out the quick water-cooled of underwater water-spraying, until axletree surface temperature is down to 600～650 DEG C, After axletree is taken out from water, cooling dipped in oil is until room temperature；And/or, the rate of cooling of water-cooled controls at 1.5～2.5 DEG C /s。
10. the axle of motor train unit steel heat treatment process Han niobium as described in claim 4-8, it is characterised in that it is applied to contain In niobium EMU axles steel production technology, this technique comprises the steps: electric arc furnace or converter smelting → LF stove essence Refining → RH or VD vacuum outgas → continuous casting → strand heating furnace heating → axle blank rolling → axle blank forging → blank axletree is thick Car → axletree neat end face processing → normalizing+quenching (shrend+oil is cold)+high tempering heat treatment, or, normalizing+quenched (is quenched Fire+high tempering) heat treatment → axletree outer circle finish turning processing → axletree internal bore boring processing → cylindricalo grinding → flaw detection.
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CN112176255A (en) * 2020-09-25 2021-01-05 马鞍山钢铁股份有限公司 Carbon steel high-speed rail axle with speed per hour being more than or equal to 400 kilometers and modification method thereof

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