CN117904536A - 50T axle load freight axle serving in 1200 MPa-level cold environment and heat treatment method and production method thereof - Google Patents
50T axle load freight axle serving in 1200 MPa-level cold environment and heat treatment method and production method thereof Download PDFInfo
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Abstract
The invention discloses a 50t axle load freight axle in service in 1200 MPa-level cold environment, which comprises the following chemical components: C. si, mn, cr, ni, mo, nb, V, cu, ca, la, [ N ], al; the anti-fatigue performance and the excellent low-temperature toughness are good, the fatigue limit R fL of a sample with a smooth surface is more than or equal to 450MPa, the fatigue limit R fE of a sample with a notch on the surface is more than or equal to 380MPa, the longitudinal impact energy KV 2 at-40 ℃ is more than or equal to 130J, the transverse impact energy KV 2 at-40 ℃ is more than or equal to 110J, the longitudinal impact energy KV 2 at-60 ℃ is more than or equal to 110J, the transverse impact energy KV 2 at-60 ℃ is more than or equal to 90J, the longitudinal impact energy KV 2 at-80 ℃ is more than or equal to 80J, the transverse impact energy KV 2 at-80 ℃ is more than or equal to 60J, and the anti-fatigue performance test can be applied to 50t axle weight freight vehicles running in a low-temperature environment above-60 ℃.
Description
Technical Field
The invention belongs to the technical field of freight axles, and particularly relates to a 50t axle weight freight axle serving in a 1200 MPa-level cold environment, and a heat treatment method and a production method thereof.
Background
In the process of circulating goods at home and abroad, the transportation of railway wagons is still an important component, the axle weight is the load weight shared by each axle on the freight vehicle, the axle weight is the most important index for measuring the load capacity of the freight vehicle, and the increase of the axle weight is the most effective and economical means for improving the freight efficiency of the railway. But the axle weight lifting is also limited by certain conditions, namely, the loading capacity of trucks is limited by line conditions such as elevated railways and railway bridges in highland areas and mountain areas, and the safe loading capacity of axles is the second.
Along with the increase of the axle weight of the train for goods, the axle has the defects of lower strength and toughness matching after the whole heat treatment and the like. The axle design and strength check of the large axle weight are carried out according to the related standard, the operation safety of the axle has a larger relation with the gap sensitivity coefficient q value (q= RfL/RfE) and the specification of the axle, in order to ensure the safety, the axle design is carried out by adopting a method for increasing the specification at present, but the dead weight of a train can be increased due to unlimited increase of the specification of the axle, the production cost of the axle is higher, the driving safety of the train is influenced, and the axle design is limited in practical application.
From the viewpoint of the running environment temperature, the lowest temperature of the running environment of the freight train reaches below minus 60 ℃, which is an extremely strict test on materials, and no related research on the axle of the large axle weight at minus 60 ℃ exists in the prior art, and no technical index, particularly low-temperature toughness index, of the axle material of the large axle weight at minus 60 ℃ exists. If a brand new axle material can be designed, the toughness level of the axle material at low temperature can reach the toughness level of the pearlite-ferrite steel axle material at normal temperature, the low-temperature service safety of the axle material can be ensured, and the safety of a 50t axle load freight train can be ensured.
Therefore, the new generation of 50t axle load freight axle with good fatigue resistance and service under 1200MPa grade cold environment has to solve the following technical problems: (1) axle lightweight structural design issues; (2) heavy duty axle materials and performance design issues. Therefore, development of an economic, cold-resistant, high-strength, high-toughness and long-fatigue-life large axle of a new material cargo train is urgently needed.
Disclosure of Invention
In order to solve the technical problems, the invention provides a 50t axle load freight axle which is served in a 1200 MPa-level cold environment, has good fatigue resistance and excellent low-temperature toughness, the fatigue limit R fL of a surface smooth sample is more than or equal to 450MPa, the fatigue limit R fE of a sample with a notch on the surface is more than or equal to 380MPa, the longitudinal impact power KV 2 at-40 ℃ is more than or equal to 130J, the transverse impact power KV 2 at-40 ℃ is more than or equal to 110J, the longitudinal impact power KV 2 at-60 ℃ is more than or equal to 110J, the transverse impact power KV 2 at-60 ℃ is more than or equal to 90J, the longitudinal impact power KV 2 at-80 ℃ is more than or equal to 80J, and the transverse impact power KV 2 at-80 ℃ is more than or equal to 60J, and the axle load freight vehicle with 50t axle load which runs in a low-temperature environment above-60 ℃.
The invention also provides a heat treatment method and a production method of the 50t axle weight freight car axle in service in a 1200 MPa-level cold environment.
The technical scheme adopted by the invention is as follows:
A50 t axle weight freight axle for service in 1200MPa grade cold environment comprises the following chemical components ：C：0.46～0.53％,Si：0.55～0.70％,Mn：0.45～0.60％,Cr：1.20～1.40％,Ni：1.65～1.85％,Mo：0.45～0.55％,Nb：0.020～0.050％,V：0.20～0.30％,Cu：0.40～0.60％,Ca：0.002～0.005％,La：0.010～0.020％,P≤0.010％,S≤0.008％,T[O]≤0.0010％,[N]：0.015～0.020％,Al：0.040～0.050％, in percentage by weight, and the balance of Fe and other unavoidable impurities.
Preferably, the following weight percentages of chemical components ：C：0.48～0.52％,Si：0.60～0.70％,Mn：0.50～0.60％,Cr：1.25～1.35％,Ni：1.70～1.80％,Mo：0.48～0.52％,Nb：0.030～0.040％,V：0.22～0.28％,Cu：0.45～0.55％,Ca：0.003～0.004％,La：0.012～0.018％,P≤0.008％,S≤0.006％,T[O]≤0.0008％,[N]：0.016～0.019％,Al：0.042～0.048％, are included with the balance being Fe and other unavoidable impurities.
The components of the 50t axle weight freight axle in service in 1200MPa grade cold environment meet the critical quenching thickness HI≥107.5,HI＝25.4×1/2×[(0.54×C)×(1.00+0.69×Si)×(1.00+3.41×Mn)×(1.00+1.99×(Cr+V))×(1.00+0.353×(Ni+Cu))×(1.00+2.98×Mo)].
The components of the 50t axle weight freight axle in service in the 1200MPa grade cold environment meet the corrosion resistance index I not less than 6.8, wherein I=26.01×Cu+3.88×Ni+1.20×Cr+1.49×Si+17.28×P-7.29×Cu×Ni-9.10×Ni×P-33.39 ×Cu 2.
The components of the 50t axle weight freight axle in service in the 1200 MPa-level cold environment meet the predicted value Y of Rm not less than 1200, and Y=9.8× (100C-100 (C-0.4)/3+10Si+25Mo+30Mn+6Ni+20Cr+60V).
The metallographic structure of the 50t axle weight freight axle in service in the 1200MPa grade cold environment is tempered sorbite and bainite, wherein the volume percentage of the tempered sorbite is 90-93%, the volume percentage of the bainite is 7-10%, and the content of the tempered sorbite on the near surface of the axle 0-40 mm is 100%.
The tensile strength of the freight axle with the axle weight of 50t serving in 1200 MPa-level cold environment is more than or equal to 1200MPa, and the yield strength is more than or equal to 850MPa; longitudinal impact energy KV 2 at minus 40 ℃ is more than or equal to 130J, and transverse impact energy KV 2 at minus 40 ℃ is more than or equal to 110J; longitudinal impact energy KV 2 at minus 60 ℃ is more than or equal to 110J, and transverse impact energy KV 2 at minus 60 ℃ is more than or equal to 90J; longitudinal impact energy KV 2 at-80 ℃ is more than or equal to 80J, and transverse impact energy KV 2 at-80 ℃ is more than or equal to 60J; the fatigue limit R fL of the sample with smooth surface is more than or equal to 450MPa; the fatigue limit R fE of the sample with the notch on the surface is more than or equal to 380MPa; the notch sensitivity index R fL/RfE is less than or equal to 1.20.
The invention also provides a heat treatment method of the 50t axle load freight axle in service in 1200 MPa-level cold environment, which comprises the following steps:
1) The preparation heat treatment comprises stress relief annealing and tissue homogenization normalizing;
2) And the performance heat treatment comprises two-phase zone quenching, biliquid sub-temperature quenching and medium temperature tempering.
In the step 1), the stress relief annealing specifically includes: the axle is heated to the temperature of 580-640 ℃ according to the heating speed of 100-120 ℃/h, the heating and heat preserving time in the temperature section is calculated according to 3min/mm by taking the maximum diameter as the reference, and the furnace is cooled. After the axle is forged, residual internal stress can be generated due to internal and external temperature difference caused by different cooling speeds of the surface and the core in the cooling process, and the internal stress is overlapped with internal attraction generated by subsequent process factors, so that the axle is distorted or cracked in subsequent performance heat treatment. In order to eliminate the internal stress, internal stress annealing treatment is needed, and meanwhile, the internal stress annealing can reduce the hardness and improve the dimensional stability.
In the step 1), the tissue homogenization normalizing specifically comprises: heating the axle to 960-1000 ℃ at a heating speed of 180-220 ℃/h, and air cooling the axle according to a heating and heat-preserving time of 0.8-1.2 min/mm calculated by taking the maximum diameter as a reference in the temperature section. The essence of normalizing is complete austenitization plus pseudo eutectoid transformation, and normalizing not only refines grains, but also improves the non-uniformity of the structure after normalizing because of lower transformation temperature, and prepares the structure for subsequent final property heat treatment. For alloy axles containing carbide forming elements such as V, cr, nb, etc., a higher heating temperature is necessary to sufficiently dissolve the carbide during the normalizing, and therefore the normalizing temperature of the present invention is set to 960 to 1000 ℃.
In the step 2), the two-phase zone quenching specifically comprises: heating the axle to 740-780 ℃ at a heating speed of 160-190 ℃/h, calculating according to 0.9-1.1 min/mm by taking the maximum diameter as a reference in the heating and heat preserving time of the temperature section, and then performing water cooling to below 150 ℃ and air cooling to room temperature. The purpose of the two-phase zone quenching is mainly that when the quenching is heated to above A c1 and the reverse transformation austenite just begins to form nuclei, atoms are not diffused actively due to low temperature, the migration of crystal boundaries is slow, austenite does not grow rapidly, but exists as fine grains, and fine laths or massive martensitic structures are formed in the subsequent quenching process, so that the effect of refining the grains is achieved.
In the step 2), the biliquid sub-temperature quenching specifically comprises the following steps: heating the axle to 840-870 ℃ at a heating speed of 170-200 ℃/h, calculating according to 0.9-1.1 min/mm based on the maximum diameter in the heating and heat preserving time of the temperature section, then cooling in alkaline solution for 40-50 s, transferring into an oil groove for continuous cooling, and cooling to below 150 ℃ for air cooling to room temperature. Therefore, the axle can be cooled quickly in the most unstable austenite areas such as pearlite and bainite transformation areas to prevent the axle from decomposing, cooled slowly in the martensite transformation, and reduced in the structural stress when the austenite is transformed into the martensite, thereby avoiding the axle from generating distortion and cracking. While ensuring that a fine lath-like martensitic structure is obtained.
Further, the alkali solution is 10% NaOH aqueous solution by mass concentration.
In the step 2), the medium temperature tempering specifically comprises the following steps: heating the axle to 640-670 ℃ at a heating speed of 130-160 ℃/h, taking the maximum diameter as a reference in the heating and heat preserving time of the temperature section, calculating the heat preserving time according to 1.4-1.6 min/mm, and then water-cooling to room temperature to avoid the second tempering brittleness of the steel. The tempering temperature is preferably 630-660 ℃, the martensite phase gradually disappears, the dislocation density is reduced, the carbide is fully precipitated and spheroidized, the structural form strength is lower, and the toughness is obviously increased. After tempering, a uniform and fine metallographic structure of tempered sorbite and bainite can be obtained, so that good toughness and plasticity and proper strength indexes can be obtained.
The maximum diameter of the blank axle subjected to heat treatment is 265-275 mm, and the maximum length is 2100-2300 mm.
The invention also provides a production method of the 50t axle weight freight axle in service in the 1200 MPa-level cold environment, which comprises the following steps: smelting in an electric arc furnace or a converter, refining in an LF furnace, RH or VD vacuum degassing, continuous casting, casting blank heating, axle blank rolling, axle blank forging, rough turning of an axle blank, axle alignment end face machining, heat treatment, rough turning of an axle outer circle, center deep hole machining, finish turning of the axle outer circle, outer circle grinding and flaw detection, wherein the heat treatment is carried out by adopting the heat treatment method.
The invention provides a 50t axle weight freight axle serving in 1200MPa grade cold environment, which comprises the following components:
C: the element C is necessary for the steel to attain high strength and hardness. The C content in the axle below the 50t axle weight is high. While a high C content is advantageous for strength, hardness, etc. of the steel, it is extremely disadvantageous for plasticity and toughness of the steel, and decreases yield ratio, increases decarburization sensitivity, and deteriorates fatigue resistance and workability of the steel. Therefore, the content of C in the steel is properly reduced, the toughness of the steel is improved, but too low content of C can affect the strength of the steel, and the content of C is controlled to be 0.46-0.53% by combining the requirement of HI value and the addition of other elements. More preferably 0.48 to 0.52%.
Si: si is a main deoxidizing element in steel, has strong solid solution strengthening effect, but too high content of Si can reduce plasticity and toughness of the steel, increase activity of C, promote decarburization and graphitization tendency of the steel in forging and heat treatment processes, make smelting difficult and form inclusion easily, and deteriorate fatigue resistance of the steel. In the comprehensive consideration, the Si content is controlled to be 0.55 to 0.70%, more preferably 0.60 to 0.70%.
Mn is the main alloying element in steel, and is the effective element for deoxidation and desulfurization, and Mn has the advantages of improving the austenite stability in steel and the hardenability and strength of steel. However, when quenched steel is tempered, mn and P have strong grain boundary co-segregation tendency, so that tempering brittleness is promoted, toughness of the steel is deteriorated, and the Mn content is controlled to be 0.45-0.60% comprehensively. More preferably 0.50 to 0.60%.
Cr: cr can effectively improve the hardenability and tempering resistance of steel to obtain the required high strength; meanwhile, cr can reduce the activity of C, reduce the decarburization tendency of the steel surface in the heating, rolling and heat treatment processes, and can be utilized to obtain high fatigue resistance. However, too high a content deteriorates the toughness of the steel, and the Cr content is controlled to be 1.20 to 1.40% in consideration of the total. More preferably 1.25 to 1.35%.
Ni: the main alloying element in the steel, ni can improve the strength and toughness of the steel, strengthen the grain boundary in a low-temperature environment, are the essential alloying elements for obtaining high toughness and low-temperature toughness, reduce the impact toughness transition temperature, improve the hardenability and corrosion resistance of the steel, ensure the toughness of the steel at low temperature, and comprehensively consider that the Ni content is controlled to be 1.65-1.85%. More preferably 1.70 to 1.80%.
Mo: mo is a substitutional solid solution alloy element, and when the Mo is dissolved in austenite, the hardenability of steel can be improved, and simultaneously, the tempering resistance and the tempering brittleness can be improved. When the Mo content is too low, the above effect is limited, and when the Mo content is too high, the above effect is saturated, and the cost of the steel is increased. Comprehensively considering, the Mo content is controlled to be 0.45-0.55%. More preferably 0.48 to 0.52%.
Nb: nb is a very effective microalloying element for refining grains, and is characterized in that Nb in steel increases the recrystallization temperature of austenite, thereby achieving the purpose of refining the austenite grains and improving the strong plasticity of the steel. The steel of the invention also utilizes the relatively stable effect of Nb carbide, can fix carbon to promote more alloying elements such as chromium, molybdenum and the like to dissolve into solid solution, and promote solid solution strengthening at high temperature. However, the strengthening effect of the excess Nb is no longer obvious and increases the crack sensitivity of the steel. The Nb content is controlled to be 0.020-0.050%. More preferably 0.030 to 0.040%.
V content: the toughening effect of V on steel is mainly represented by precipitation strengthening, V (C, N) refined austenite grains can be precipitated during forging and rolling, and a large amount of V (CN) nanometer second phase refined reheated austenite grains are precipitated during heat treatment reheating, and the excessive V content can cause the excessively high V (CN) precipitation temperature, the excessively large precipitation amount and the easily coarse grain size, thereby being unfavorable for refining austenite grains and being unfavorable for strength, toughness and the like of steel. The combined effect above V which is too low is not obvious. Comprehensively considering that the V content is controlled to be 0.20-0.30 percent. More preferably 0.22 to 0.28%.
Cu content: copper is also a non-carbide forming element in steel, can promote austenite to form, has large solubility change in the steel, has the functions of solid solution strengthening and precipitation dispersion strengthening, and can improve yield strength and tensile strength; meanwhile, the cathode contact between the steel and Cu secondarily precipitated on the surface can promote the anodization of the steel, form a rust layer with better protection, improve the corrosion resistance of the steel, and particularly remarkably improve the corrosion resistance of the steel when Cu and Ni, cr, mo, V are combined. Cu and Ni can form infinite solid solution, so that the melting point of the solid solution is improved, and cracking on the surface of steel is prevented. The Cu content is lower than 0.40%, the Cu plays a small role, the corrosion resistance of the steel is poor, the Cu content is higher than 0.60%, cracks are easily generated on the surface of the steel, and the Cu content is controlled to be 0.40-0.60% comprehensively. More preferably 0.45 to 0.55%.
Ca: ca has the functions of deoxidizing and desulfurizing and modifying nonmetallic inclusion, so as to improve the toughness and fatigue resistance of steel. The Ca content of less than 0.002% does not exert the above-mentioned effect, but the content exceeding 0.005% makes the addition quite difficult and increases the amount of inclusions. Therefore, the Ca content is controlled to be 0.0020 to 0.0050%, and more preferably 0.0030 to 0.0040%.
La: the addition of proper amount of La element in steel can make MnS, A1 2O3 and other impurities become rare earth impurities, and has good deoxidization and desulfurization effects. The La element tiny solid particles provide heterogeneous crystal nucleus or are biased to gather on a crystallization interface, so that the growth of a unit cell is hindered, and the normal-temperature mechanical property of the steel is improved. The effect of excess La is no longer evident. The La content is controlled to be 0.010-0.020%. More preferably, la is 0.012 to 0.018%.
P: p can form micro segregation when molten steel is solidified, and then is biased to grain boundary when heated at austenitizing temperature, so that brittleness of steel is obviously increased, and the content of P is controlled below 0.010%. More preferably 0.008% or less.
S: unavoidable impurities in the steel form MnS inclusions and grain boundary segregation worsen toughness and fatigue resistance of the steel, so that the content thereof is controlled to be 0.008% or less. More preferably 0.006% or less.
T [ O ]: oxygen forms various oxide inclusions in the steel. Under the action of stress, stress concentration is easy to occur at the oxide inclusions, so that microcrack initiation is caused, and the mechanical properties, particularly toughness and fatigue resistance, of the steel are deteriorated. Therefore, in metallurgical production, measures must be taken to reduce the content as much as possible. The content thereof is controlled to be 0.0010% or less in view of economy. More preferably 0.0008% or less.
[ N ]: n and V, al in steel form carbonitride, which can effectively inhibit austenite grain growth, but excessive N content can cause the toughness and fatigue resistance of steel to be deteriorated, and the control range of N content is 0.015-0.020% comprehensively. More preferably 0.016 to 0.019%.
Al: in addition to reducing dissolved oxygen in the molten steel, aluminum can also act to refine the grains. However, excessive Al content reduces harmful elements such as Ti in steel, and the like, and molten steel is easy to pollute due to secondary oxidation during continuous casting, and the Al content is controlled to be 0.040-0.050% comprehensively. More preferably 0.042 to 0.048%.
Compared with AAR M-101F adopted by the axle load of less than 45t, the 50t axle load freight axle in service in 1200MPa grade cold environment provided by the invention has the advantages that the content of C element is properly reduced, the plasticity and toughness of steel are improved, trace Nb, V, N and other elements are added, the NbV (CN) precipitation strengthening effect is exerted, grains are refined, and the toughness and yield strength of the steel are improved, so that the fatigue resistance and peeling resistance of the steel are improved; cr and Mo elements are added into the steel to improve the oxidation resistance and corrosion resistance of the steel, improve the hardenability and tempering resistance of the steel and increase the fatigue limit of the surface of an axle; the steel is added with proper Ni and Cu elements, ni can improve the strength and toughness of the steel, strengthen grain boundary under low temperature condition, obtain high low temperature toughness, reduce impact toughness transition temperature, promote the anodization of the steel and form a rust layer with better protectiveness by cathode contact between the steel and Cu secondarily precipitated on the surface, improve the corrosion resistance of the steel, simultaneously form infinite solid solution by Cu and Ni, improve the melting point of the solid solution and prevent cracking on the surface of the steel. RE and La elements are added into the steel, so that the segregation of harmful impurity elements in the grain boundary is reduced, the grain boundary is improved and reinforced, the spheroidization of inclusions is promoted, the toughness of the steel is further improved, and the notch sensitivity index of the material is reduced. The contents of impurity elements T [ O ], P, S, etc. in the steel are strictly controlled to further improve the fatigue resistance of the steel.
Mn, si, ni, cr, mo, cu, V and other elements are main elements for influencing the hardenability of steel, and meanwhile, the influence factors of each element on the hardenability of the steel are different, so that the section of the axle is subjected to heat treatment to obtain tempered sorbite and bainite composed of uniform fine grain cementite and polygonal ferrite matrixes with excellent fatigue resistance, and the maximum effective thickness H of the axle from the surface to the inner surface of a central hole is obtained by combining the maximum diameter size (phi 275 mm) of the section of the axle and the diameter size (phi 60mm to phi 80 mm) of the central deep hole: the critical quenching thickness HI＝25.4×1/2×[(0.54C)×(1.00+0.69×Si)×(1.00+3.41×Mn)×(1.00+1.99×(Cr+V))×(1.00+0.353×(Ni+Cu))×(1.00+2.98×Mo)] is not less than 107.5mm, and the critical quenching thickness is not less than 107.5.
Meanwhile, in order to ensure the axle to have better corrosion resistance, the corrosion resistance index (I) of the steel needs to be ensured, and according to the influence factors of various elements on the corrosion of the axle, cr can form a compact oxide film on the surface of the steel, so that the passivation capability of the steel is improved. Cu can improve the corrosion resistance potential of steel, obviously improves the corrosion resistance, forms a corrosion resistance formula through reasonable matching of effective elements, and sets the corrosion resistance index I of the steel: i=26.01×cu+3.88×ni+1.20×cr+1.49×si+17.28×p-7.29×cu×ni-9.10×ni×p-33.39 ×cu 2.
With the increase of the running axle weight of the train, the fatigue life requirement of the axle increases exponentially. Compared with the cycle 10 7 without breaking of the axle fatigue performance requirement below 45t, the axle fatigue life requirement of the axle with 50t is improved by 1 order of magnitude, namely the cycle 10 8 without breaking of the fatigue performance requirement, the fatigue strength ratio R fL/Rm is approximately equal to 0.50 for the high cycle 10 7 fatigue, and the fatigue strength ratio R fL/Rm is approximately equal to 0.40 for the ultra-high cycle 10 8 fatigue. Therefore, if the axle requirement of 50t axle weight is met, the tensile strength Rm should be more than or equal to 1200MPa, and according to the action of alloy elements in steel, the Rm predicted value Y=9.8× (100C-100 (C-0.4)/3+10Si+25Mo+30Mn+6Ni+20Cr+60V) should be more than or equal to 1200.Y is an index for evaluating the influence of each element on the tensile strength of the quenched and tempered steel by weighting and adding.
In the above formula, the index value of each element is the content of the element corresponding to the component multiplied by 100;
Compared with the normalizing and tempering adopted by the AAR M-101F axle, the heat treatment method for the 50t axle freight axle in service under the 1200 MPa-level cold environment adopts the whole tempering heat treatment technology of 'preliminary heat treatment (stress relief annealing + tissue homogenization normalizing) +performance heat treatment (two-phase zone quenching + double-liquid sub-temperature quenching + medium-temperature tempering'), so that the whole section of the axle obtains tempered sorbite and bainite composed of uniform fine grain cementite and polygonal ferrite matrix, and has stronger toughness and higher yield ratio while obtaining high hardness and high strength compared with 'pearlite and ferrite', thereby further improving the fatigue resistance of the axle.
The traditional 45t axle weight axle adopts a solid axle design, the invention adopts a center deep hole light-weight design with the diameter of phi 80mm, reduces the dead weight of the axle, lightens the unsprung weight of a bogie, reduces the abrasion between wheels and rails, can directly and periodically carry out ultrasonic flaw detection on line under the condition that the bogie is not disassembled, checks the internal defect condition of the axle, and ensures the safety of wheel pairs.
Compared with the prior art, the invention has the following beneficial effects:
compared with the prior art, the cold-resistant freight large-axle-weight axle produced by adopting the chemical components, the technological process and the heat treatment technological parameters has the advantages of cold resistance, high strength and excellent fatigue resistance.
(1) The high strength of over 1200MPa can be obtained, the plasticity and toughness of the steel are obviously superior to those of commercial steel, the fatigue limit of the steel is obviously higher than that of commercial steel, and the steel has good strength and toughness matching and excellent fatigue resistance. Wherein: the tensile strength (Rm) is more than or equal to 1200MPa, the yield strength is more than or equal to 850MPa, the longitudinal impact power KV 2 at 40 ℃ is more than or equal to 130J, the transverse impact power KV 2 at 40 ℃ is more than or equal to 110J, the longitudinal impact power KV 2 at 60 ℃ is more than or equal to 110J, the transverse impact power KV 2 at 60 ℃ is more than or equal to 90J, the longitudinal impact power KV 2 at 80 ℃ is more than or equal to 80J, the transverse impact power KV 2 at 80 ℃ is more than or equal to 60J, the fatigue limit R fL of a smooth surface sample is more than or equal to 450MPa, the fatigue limit R fE of a surface with a notch sample is more than or equal to 380MPa, the notch sensitivity index R fL/RfE is less than or equal to 1.20, and the safety performance requirement can be met on the premise of not increasing the specification on the basis of the axle of 45t axle weight, and the axle weight has the ductile-80 ℃ transition temperature.
(2) The austenite grain size is 10.0 or more. The structure of the heat treated steel is tempered sorbite and bainite, wherein the volume percentage of tempered sorbite is 90-93%, the volume percentage of bainite is 7-10%, and the content of tempered sorbite on the near surface of an axle of 0-40 mm is 100%.
(3) Compared with an axle with the axle weight below 45, the automobile axle can meet the safety performance requirement on the premise of not increasing the specification, and has the ductile-brittle transition temperature of minus 60 ℃.
Drawings
FIG. 1 is a 40mm metallographic structure under the axle surface of example 1, 100% tempered sorbite;
FIG. 2 shows a metallographic structure of 40mm below the surface of the axle in comparative example 1, which is pearlite+ferrite.
Detailed Description
The invention provides a 50t axle weight freight axle which is served in a 1200 MPa-level cold environment, and comprises the following chemical components ：C：0.46～0.53％,Si：0.55～0.70％,Mn：0.45～0.60％,Cr：1.20～1.40％,Ni：1.65～1.85％,Mo：0.45～0.55％,Nb：0.020％～0.050％,V：0.20～0.30％,Cu：0.40～0.60％,Ca：0.002～0.005％,La：0.010～0.020％,P≤0.010％,S≤0.008％,T[O]≤0.0010％,[N]：0.015～0.020％,Al：0.040～0.050％, in percentage by weight, and the balance of Fe and other unavoidable impurities.
Preferably, the following weight percentages of chemical components ：C：0.48～0.52％,Si：0.60～0.70％,Mn：0.50～0.60％,Cr：1.25～1.35％,Ni：1.70～1.80％,Mo：0.48～0.52％,Nb：0.030％～0.040％,V：0.22～0.28％,Cu：0.45～0.55％,Ca：0.003～0.004％,La：0.012～0.018％,P≤0.008％,S≤0.006％,T[O]≤0.0008％,[N]：0.016～0.019％,Al：0.042～0.048％, are included with the balance being Fe and other unavoidable impurities.
The components of the 50t axle weight freight axle in service in 1200MPa grade cold environment meet the critical quenching thickness HI≥107.5,HI＝25.4×1/2×[(0.54×C)×(1.00+0.69×Si)×(1.00+3.41×Mn)×(1.00+1.99×(Cr+V))×(1.00+0.353×(Ni+Cu))×(1.00+2.98×Mo)].
The components of the 50t axle weight freight axle in service in the 1200MPa grade cold environment meet the corrosion resistance index I not less than 6.8, wherein I=26.01×Cu+3.88×Ni+1.20×Cr+1.49×Si+17.28×P-7.29×Cu×Ni-9.10×Ni×P-33.39 ×Cu 2.
The components of the 50t axle weight freight axle in service in the 1200 MPa-level cold environment meet the predicted value Y of Rm not less than 1200, and Y=9.8× (100C-100 (C-0.4)/3+10Si+25Mo+30Mn+6Ni+20Cr+60V).
The heat treatment method of the 50t axle weight freight axle in service in 1200 MPa-level cold environment comprises the following steps:
1) The preparation heat treatment comprises stress relief annealing and tissue homogenization normalizing;
2) And the performance heat treatment comprises two-phase zone quenching, biliquid sub-temperature quenching and medium temperature tempering.
In the step 1), the stress relief annealing specifically includes: the axle is heated to the temperature of 580-640 ℃ according to the heating speed of 100-120 ℃/h, the heating and heat preserving time in the temperature section is calculated according to 3min/mm by taking the maximum diameter as the reference, and the furnace is cooled.
In the step 1), the tissue homogenization normalizing specifically comprises: heating the axle to 960-1000 ℃ at a heating speed of 180-220 ℃/h, and air cooling the axle according to a heating and heat-preserving time of 0.8-1.2 min/mm calculated by taking the maximum diameter as a reference in the temperature section.
In the step 2), the two-phase zone quenching specifically comprises: heating the axle to 740-780 ℃ at a heating speed of 160-190 ℃/h, calculating according to 0.9-1.1 min/mm by taking the maximum diameter as a reference in the heating and heat preserving time of the temperature section, and then performing water cooling to below 150 ℃ and air cooling to room temperature.
In the step 2), the biliquid sub-temperature quenching specifically comprises the following steps: heating the axle to 840-870 ℃ at a heating speed of 170-200 ℃/h, calculating according to 0.9-1.1 min/mm based on the maximum diameter in the heating and heat preserving time of the temperature section, then cooling in alkaline solution for 40-50 s, transferring into an oil groove for continuous cooling, and cooling to below 150 ℃ for air cooling to room temperature.
Further, the alkali solution is 10% NaOH aqueous solution by mass concentration.
In the step 2), the medium temperature tempering specifically comprises the following steps: heating the axle to 640-670 ℃ at a heating speed of 130-160 ℃/h, taking the maximum diameter as a reference for heating and heat preservation time in the temperature section, calculating the heat preservation time according to 1.4-1.6 min/mm, and then cooling to room temperature by water.
The production method of the 50t axle weight freight axle in service in 1200 MPa-level cold environment comprises the following steps: smelting in an electric arc furnace or a converter, refining in an LF furnace, RH or VD vacuum degassing, continuous casting, casting blank heating, axle blank rolling, axle blank forging, rough turning of an axle blank, axle alignment end face machining, heat treatment, rough turning of an axle outer circle, center deep hole machining, finish turning of the axle outer circle, outer circle grinding and flaw detection, wherein the heat treatment is carried out by adopting the heat treatment method.
The present invention will be described in detail with reference to examples.
Examples 1 to 4
A50 t axle weight freight axle with good fatigue resistance in 1200MPa grade cold environment is provided, the chemical compositions and weight percentages of which are shown in Table 1, and the balance of Fe and unavoidable impurities which are not shown in Table 1.
Comparative example 1-comparative example 3
A heavy truck axle under 45t axle weight is provided, which has chemical composition and weight percentage shown in Table 1, the balance not shown in Table 1 being Fe and unavoidable impurities.
Table 1 examples and comparative examples smelting chemistry mass percent (wt%) and critical quench thickness (in) and corrosion resistance index
Examples 1 to 4
The maximum diameter of the axle in the examples is 265 mm-275 mm and the maximum length is 2100-2300 mm.
The method comprises the following steps: smelting in an electric arc furnace or a converter, refining in an LF furnace, RH or VD vacuum degassing, continuous casting, casting blank heating, axle blank rolling, axle blank forging, axle rough turning of a blank, axle end face machining, stress relief annealing, tissue homogenization normalizing, two-phase zone quenching, double-liquid sub-temperature quenching and medium temperature tempering, axle outer circle rough turning, center deep hole machining, axle outer circle finish turning, outer circle grinding and flaw detection.
The specific heat treatment process of each example is as follows:
Example 1:
Stress relief annealing: heating to 640 ℃ at 120 ℃/h, heating and preserving the heat for 795min, and cooling to below 100 ℃.
Tissue homogenization normalizing: heating to 1000 ℃ at 180 ℃/h, heating and preserving the heat for 290min, and air cooling to below 200 ℃.
Quenching in a two-phase region: heating to 780 ℃ at 160 ℃/h, heating and preserving the heat for 250min, cooling to below 150 ℃ by water, and cooling to room temperature by air.
And (3) double-liquid sub-temperature quenching: heating to 870 ℃ at 200 ℃/h, heating and preserving time 275min, cooling for 40s by 10% NaOH aqueous solution, transferring into quenching oil, cooling to below 150 ℃, and air cooling to room temperature.
Medium temperature tempering: heating to 660 ℃ at 130 ℃ per hour, heating and preserving the heat for 410min, and cooling to room temperature by water, so as to avoid secondary tempering brittleness.
Example 2:
stress relief annealing: heating to a temperature of 580 ℃ at 100 ℃/h, heating and preserving heat for 825min, and cooling to below 100 ℃.
Tissue homogenization normalizing: heating to 960 ℃ at 220 ℃/h, heating and preserving heat for 330min, and air cooling to below 200 ℃.
Quenching in a two-phase region: heating to 740 ℃ at 190 ℃/h, heating and preserving time of 275min, cooling to below 150 ℃ by water, and cooling to room temperature by air cooling
And (3) double-liquid sub-temperature quenching: heating to 840 ℃ at 170 ℃/h, heating and preserving time for 250min, cooling for 45s by 10% NaOH aqueous solution, transferring into quenching oil, cooling to below 150 ℃, and air cooling to room temperature.
Medium temperature tempering: heating to 640 ℃ at 130 ℃ per hour, heating and preserving heat for 420min, and cooling to room temperature by water, so as to avoid secondary tempering brittleness.
Example 3:
stress relief annealing: heating to 590 ℃ at 110 ℃/h, heating and preserving the heat for 800min, and cooling to below 100 ℃.
Tissue homogenization normalizing: heating to 970 ℃ at 210 ℃/h, heating and preserving the heat for 300min, and air cooling to below 200 ℃.
Quenching in a two-phase region: heating to 750 ℃ at 180 ℃/h, heating and preserving heat for 290min, cooling to below 150 ℃ by water, and cooling to room temperature by air cooling
And (3) double-liquid sub-temperature quenching: heating to 850 ℃ at 180 ℃/h, heating and preserving time for 260min, cooling for 44s by 10% NaOH aqueous solution, transferring into quenching oil, cooling to below 150 ℃ and air cooling to room temperature.
Medium temperature tempering: heating to 640 ℃ at 140 ℃/h, heating and preserving heat for 430min, and cooling to room temperature by water, so as to avoid secondary tempering brittleness.
Example 4:
Stress relief annealing: heating to 620 ℃ at 110 ℃/h, heating and preserving the heat for 810min, and cooling to below 100 ℃.
Tissue homogenization normalizing: heating to 990 ℃ at 190 ℃/h, heating and preserving the heat for 290min, and air cooling to below 200 ℃.
Quenching in a two-phase region: heating to 770 ℃ at 170 ℃/h, heating and preserving heat for 300min, cooling to below 150 ℃ by water, and cooling to room temperature by air cooling
And (3) double-liquid sub-temperature quenching: heating to 860 ℃ at 190 ℃/h, heating and preserving time 280min, cooling for 48s by 10% NaOH aqueous solution, transferring into quenching oil, cooling to below 150 ℃ and air cooling to room temperature.
Medium temperature tempering: heating to 650 ℃ at 150 ℃ per hour, heating and preserving heat for 430min, and cooling to room temperature by water, so as to avoid secondary tempering brittleness.
Other process flows are carried out according to conventional techniques.
Comparative example 1-comparative example 2
The method comprises the following steps: smelting in an electric arc furnace or a converter, refining in an LF furnace, RH or VD vacuum degassing, continuous casting, casting blank heating, axle blank rolling, axle blank forging, rough turning of an axle blank, axle alignment end face processing, normalizing, tempering, axle excircle finish turning processing, excircle grinding and flaw detection.
The heat treatment processes of the cold-resistant freight large-axle-weight vehicle axles produced in comparative examples 1 and 2 comprise twice normalizing and tempering, and specific heat treatment process parameters are as follows:
Comparative example 1:
normalizing: heating to 870 ℃ at 120 ℃/h, heating and preserving the heat for 280min, and cooling to below 200 ℃;
Normalizing: heating to 820 ℃ at 120 ℃/h, heating and preserving the heat for 280min, and cooling to below 200 ℃;
Tempering: heating to 560 ℃ at 100 ℃ per hour, heating and preserving the heat for 420min, and cooling to room temperature.
Comparative example 2:
Normalizing: heating to 860 ℃ at 110 ℃/h, heating and preserving the heat for 280min, and cooling to below 200 ℃;
Normalizing: heating to 800 ℃ at 120 ℃/h, heating and preserving heat for 280min, and cooling to below 200 ℃;
tempering: heating to 550 ℃ at 100 ℃ per hour, heating and preserving the heat for 420min, and cooling to room temperature.
Comparative example 3
The method comprises the following steps: smelting in an electric arc furnace or a converter, refining in an LF furnace, RH or VD vacuum degassing, continuous casting, casting blank heating, axle blank rolling, axle blank forging, rough turning of an axle blank, axle alignment end face processing, normalizing, quenching and tempering, axle excircle finish turning processing, excircle grinding and flaw detection.
The heat treatment process of the large-axle-weight axle produced in the comparative example 3 comprises normalizing, quenching and tempering, and specific heat treatment process parameters are as follows:
Normalizing: heating to a temperature of 870 ℃ at 70 ℃ per hour, and cooling to below 200 ℃ according to 400 ℃ per hour for 360 min;
quenching: heating to 850 ℃ at 70 ℃ per hour, heating and preserving heat for 390min, and cooling to room temperature by water;
Tempering: heating to 670 ℃ at 70 ℃ per hour, heating and preserving heat for 560min, cooling to below 150 ℃ at 400 ℃ per hour, and then cooling to room temperature.
Comparative example 4-comparative example 5:
The axles in comparative examples 4 to 5 had maximum diameters of 265mm to 275mm and maximum lengths of 2100 to 2300mm.
The method comprises the following steps: smelting in an electric arc furnace or a converter, refining in an LF furnace, RH or VD vacuum degassing, continuous casting, casting blank heating, axle blank rolling, axle blank forging, axle rough turning of a blank, axle end face machining, stress relief annealing, tissue homogenization normalizing, two-phase zone quenching, double-liquid sub-temperature quenching and medium temperature tempering, axle outer circle rough turning, center deep hole machining, axle outer circle finish turning, outer circle grinding and flaw detection.
The specific heat treatment process of each example is as follows:
stress relief annealing: heating to a temperature of 580 ℃ at 100 ℃/h, heating and preserving heat for 825min, and cooling to below 100 ℃.
Tissue homogenization normalizing: heating to 960 ℃ at 220 ℃/h, heating and preserving heat for 330min, and air cooling to below 200 ℃.
Quenching in a two-phase region: heating to 740 ℃ at 190 ℃/h, heating and preserving time of 275min, cooling to below 150 ℃ by water, and cooling to room temperature by air cooling
And (3) double-liquid sub-temperature quenching: heating to 840 ℃ at 170 ℃/h, heating and preserving time for 250min, cooling for 45s by 10% NaOH aqueous solution, transferring into quenching oil, cooling to below 150 ℃, and air cooling to room temperature.
Medium temperature tempering: heating to 670 ℃ at 130 ℃ per hour, heating and preserving heat for 420min, and cooling to room temperature by water, so as to avoid secondary tempering brittleness.
Comparative example 5:
Stress relief annealing: heating to 620 ℃ at 110 ℃/h, heating and preserving the heat for 810min, and cooling to below 100 ℃.
Tissue homogenization normalizing: heating to 990 ℃ at 190 ℃/h, heating and preserving the heat for 290min, and air cooling to below 200 ℃.
Quenching in a two-phase region: heating to 770 ℃ at 170 ℃/h, heating and preserving heat for 300min, cooling to below 150 ℃ by water, and cooling to room temperature by air cooling
And (3) double-liquid sub-temperature quenching: heating to 860 ℃ at 190 ℃/h, heating and preserving time 280min, cooling for 48s by 10% NaOH aqueous solution, transferring into quenching oil, cooling to below 150 ℃ and air cooling to room temperature.
Medium temperature tempering: heating to 650 ℃ at 150 ℃ per hour, heating and preserving heat for 430min, and cooling to room temperature by water, so as to avoid secondary tempering brittleness.
The performance indexes of the axles in examples and comparative examples are shown in tables 2, 3, and 4.
Table 2 mechanical properties and corrosion resistance of examples and comparative examples
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Table 3 metallographic structures and comparative examples, hardness values and deviations of axle sections
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The above-mentioned organization and performance detection method is as follows:
performance tests were performed with reference to GB/T13299, GB/T6394, GB/T228, GB/T229, GB/T231, GB/T21143, GB/T19746, YB/T5345.
From the above, it can be seen that the chemical components of the steel in examples 1 to 4, and the production method are properly controlled, so that the HI is more than or equal to 107.5, the I is more than or equal to 6.8, and the strength, plasticity, toughness and contact fatigue resistance of the steel are good. Comparative examples 1 and 2 are chemical components and the heat treatment process is not suitable, and the heat treatment process of comparative example 3 is not suitable. The chemical composition and heat treatment process of comparative example 1 and comparative example 2 were improperly controlled, resulting in excessively low strength, cross-sectional hardness, and fatigue resistance of the steel. Comparative example 3 has the same chemical composition as example 2, but the heat treatment process is not reasonable resulting in lower strength. The chemical components and the heat treatment process of comparative example 4 meet the requirements, but the Y value does not meet the requirements of the strength prediction formula, so that the final mechanical energy does not meet the requirements, and the chemical components and the heat treatment process of comparative example 5 meet the requirements, but the I value does not meet the requirements of the corrosion resistance index formula.
The foregoing detailed description of a 50t axle load freight axle and its heat treatment method and production method in a 1200MPa grade cold environment with reference to the embodiments is illustrative and not limiting, and several embodiments may be listed in the scope of the disclosure without departing from the general inventive concept, and therefore, should fall within the scope of the disclosure.
Claims (16)
1. A50 t axle weight freight axle for service in 1200MPa grade cold environment is characterized by comprising the following chemical components ：C：0.46～0.53％,Si：0.55～0.70％,Mn：0.45～0.60％,Cr：1.20～1.40％,Ni：1.65～1.85％,Mo：0.45～0.55％,Nb：0.020～0.050％,V：0.20～0.30％,Cu：0.40～0.60％,Ca：0.002～0.005％,La：0.010～0.020％,P≤0.010％,S≤0.008％,T[O]≤0.0010％,[N]：0.015～0.020％,Al：0.040～0.050％, in percentage by weight and the balance of Fe and other unavoidable impurities.
2. The 50t axle load freight axle for service in a 1200MPa grade cold environment of claim 1 comprising the following weight percent chemical components ：C：0.48～0.52％,Si：0.60～0.70％,Mn：0.50～0.60％,Cr：1.25～1.35％,Ni：1.70～1.80％,Mo：0.48～0.52％,Nb：0.030～0.040％,V：0.22～0.28％,Cu：0.45～0.55％,Ca：0.003～0.004％,La：0.012～0.018％,P≤0.008％,S≤0.006％,T[O]≤0.0008％,[N]：0.016～0.019％,Al：0.042～0.048％, balance Fe and other unavoidable impurities.
3. The 50t axle load freight axle in service in a 1200MPa grade cold environment of claim 1, wherein the composition of the 50t axle load freight axle in service in a 1200MPa grade cold environment meets a critical quench thickness HI≥107.5,HI＝25.4×1/2×[(0.54×C)×(1.00+0.69×Si)×(1.00+3.41×Mn)×(1.00+1.99×(Cr+V))×(1.00+0.353×(Ni+Cu))×(1.00+2.98×Mo)].
4. The 50t axle load freight axle for service in a 1200MPa grade cold environment of claim 1, wherein the composition of the 50t axle load freight axle for service in a 1200MPa grade cold environment satisfies the corrosion resistance index I being no less than 6.8, I = 26.01 xcu +3.88 xni +1.20 xcr +1.49 xci +17.28 xcu-7.29 xcu x Ni-9.10 xni x P-33.39 xcu 2.
5. The 50t axle load freight axle for service in a 1200 MPa-grade cold environment of claim 1, wherein the composition of the 50t axle load freight axle for service in a 1200 MPa-grade cold environment satisfies a predicted value Y of Rm greater than or equal to 1200, Y = 9.8× (100C-100 (C-0.4)/3+10si+25mo+30mn+6ni+20cr+60v).
6. The 50t axle load freight axle in service in a 1200MPa grade cold environment of any one of claims 1-5, wherein the 50t axle load freight axle in service in a 1200MPa grade cold environment has a metallographic structure of tempered sorbite and bainite.
7. The 50t axle load freight axle in service in a 1200MPa grade cold environment of any one of claims 1-5, wherein the 50t axle load freight axle in service in a 1200MPa grade cold environment has a tensile strength of greater than or equal to 1200MPa and a yield strength of greater than or equal to 850MPa; longitudinal impact energy KV 2 at minus 40 ℃ is more than or equal to 130J, and transverse impact energy KV 2 at minus 40 ℃ is more than or equal to 110J; longitudinal impact energy KV 2 at minus 60 ℃ is more than or equal to 110J, and transverse impact energy KV 2 at minus 60 ℃ is more than or equal to 90J; longitudinal impact energy KV 2 at-80 ℃ is more than or equal to 80J, and transverse impact energy KV 2 at-80 ℃ is more than or equal to 60J; the fatigue limit R fL of the sample with smooth surface is more than or equal to 450MPa; the fatigue limit R fE of the sample with the notch on the surface is more than or equal to 380MPa;
the notch sensitivity index R fL/RfE is less than or equal to 1.20.
8. The heat treatment method of a 50t axle load freight axle in service in a 1200MPa grade cold environment of any one of claims 1-7, wherein the heat treatment method comprises the steps of:
1) The preparation heat treatment comprises stress relief annealing and tissue homogenization normalizing;
2) And the performance heat treatment comprises two-phase zone quenching, biliquid sub-temperature quenching and medium temperature tempering.
9. The heat treatment method according to claim 8, wherein in step 1), the stress relief annealing is specifically: the axle is heated to the temperature of 580-640 ℃ according to the heating speed of 100-120 ℃/h, the heating and heat preserving time in the temperature section is calculated according to 3min/mm by taking the maximum diameter as the reference, and the furnace is cooled.
10. The heat treatment method according to claim 8, wherein in step 1), the tissue homogenization normalization is specifically: heating the axle to 960-1000 ℃ at a heating speed of 180-220 ℃/h, and air cooling the axle according to a heating and heat-preserving time of 0.8-1.2 min/mm calculated by taking the maximum diameter as a reference in the temperature section.
11. The heat treatment method according to claim 8, wherein in step 2), the two-phase zone quenching is specifically: heating the axle to 740-780 ℃ at a heating speed of 160-190 ℃/h, calculating according to 0.9-1.1 min/mm by taking the maximum diameter as a reference in the heating and heat preserving time of the temperature section, and then performing water cooling to below 150 ℃ and air cooling to room temperature.
12. The heat treatment method according to claim 8, wherein in step 2), the two-liquid sub-temperature quenching is specifically: heating the axle to 840-870 ℃ at a heating speed of 170-200 ℃/h, calculating according to 0.9-1.1 min/mm based on the maximum diameter in the heating and heat preserving time of the temperature section, then cooling in alkaline solution for 40-50 s, transferring into an oil groove for continuous cooling, and cooling to below 150 ℃ for air cooling to room temperature.
13. The heat treatment method according to claim 8, wherein in step 2), the medium temperature tempering is specifically: heating the axle to 640-670 ℃ at a heating speed of 130-160 ℃/h, taking the maximum diameter as a reference for heating and heat preservation time in the temperature section, calculating the heat preservation time according to 1.4-1.6 min/mm, and then cooling to room temperature by water.
14. The heat treatment method according to claim 8, wherein the maximum diameter of the axle of the blank subjected to the heat treatment is 265mm to 275mm and the maximum length is 2100 to 2300mm.
15. The method for producing a 50t axle load freight axle for service in a 1200MPa grade cold environment of any one of claims 1-7, comprising the steps of: smelting in an arc furnace or a converter, refining in an LF furnace, RH or VD vacuum degassing, continuous casting, casting blank heating, axle blank rolling, axle blank forging, axle rough turning of a blank, axle alignment end face machining, heat treatment, axle outer circle rough turning machining, center deep hole machining, axle outer circle finish turning machining, outer circle grinding and flaw detection, wherein the heat treatment is carried out by adopting the heat treatment method according to any one of claims 8-14.
16. Use of a 50t axle load freight axle in service in a 1200MPa grade cold environment as claimed in any one of claims 1-7 in a freight vehicle.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410055895.2A CN117904536A (en) | 2024-01-15 | 2024-01-15 | 50T axle load freight axle serving in 1200 MPa-level cold environment and heat treatment method and production method thereof |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410055895.2A CN117904536A (en) | 2024-01-15 | 2024-01-15 | 50T axle load freight axle serving in 1200 MPa-level cold environment and heat treatment method and production method thereof |
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| CN117904536A true CN117904536A (en) | 2024-04-19 |
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| CN202410055895.2A Pending CN117904536A (en) | 2024-01-15 | 2024-01-15 | 50T axle load freight axle serving in 1200 MPa-level cold environment and heat treatment method and production method thereof |
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