CN105143473A - Bainitic microalloy steel with enhanced nitriding characteristics - Google Patents
Bainitic microalloy steel with enhanced nitriding characteristics Download PDFInfo
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- CN105143473A CN105143473A CN201480016291.1A CN201480016291A CN105143473A CN 105143473 A CN105143473 A CN 105143473A CN 201480016291 A CN201480016291 A CN 201480016291A CN 105143473 A CN105143473 A CN 105143473A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/24—Nitriding
- C23C8/26—Nitriding of ferrous surfaces
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/20—Isothermal quenching, e.g. bainitic hardening
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/02—Pretreatment of the material to be coated
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
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Abstract
A forged, microalloyed, and nitrided steel part is disclosed to have a composition including 0.20 - 0.40 wt.% C, 0.50 - 1.60 wt.% Mn, 0.40 - 1.50 wt.% Cr, 0.07 - 0.30 wt.% Al, 0.03 - 0.20 wt.% V, 0.10 - 0.40 wt.% Si, and a balance of Fe and incidental impurities. The part may be produced by heating the steel part to austenization temperature of approximately 1100 degrees C to 1260 degrees C, hot forging the steel part, controlled air cooling the steel part after hot forging at a rate falling approximately in the range from 1 degree C per second to 5 degrees C per second as the steel part cools from approximately 900 degrees C to approximately 500 degrees C to produce a predominantly bainitic microstructure of greater than approximately 50% bainite. The steel part may then be machined to a desired configuration, and nitrided by heating in an atmosphere containing ammonia.
Description
Technical field
The present invention relates generally to bainite micro-alloyed steel, and relate more specifically to that there is the bainite micro-alloyed steel strengthening nitriding characteristics.
Background technology
Such as the power-transmitting part of axle, shaft coupling, gear, cam and sprocket wheel and so on usually will stand high pressure, torque loads and Impulsive load.The nitrided surface process of setting being called as " nitriding " generally include make mechanical workout at about 510 DEG C (950 Fahrenheit degrees) temperature to 538 DEG C (1,000 Fahrenheit degrees), stand containing nitrogen medium (normally ammonia) effect with heat treated parts.Nitriding adds surface hardness, wear resistance and the resistance to certain corrosion types and surface stress, which improves the fatigue resistance of nitrogenize parts.Therefore, Nitralloy object usually for gear, shaft coupling, axle and other need the application of wear-resistant and resistance to heavily stressed loading.
One group can hardening agent steel be AISI/SAE4100 series alloy steel after the heat treatment by nitriding.Especially, needing, in the various gear manufacture in conjunction with high surface hardness and core hardness, to have been found that AISI/SAE4140H steel alloy is useful.AISI/SAE4140H steel alloy has the composition of specifying as follows: weight percent accounts for the carbon of 0.37% to 0.44%; Weight percent accounts for the manganese of 0.65% to 1.10%; Weight percent accounts for the silicon of 0.15% to 0.35%; Weight percent accounts for the chromium of 0.75% to 1.20%; Weight percent accounts for the molybdenum of 0.15% to 0.25%; The iron of surplus and acceptable trace element.
Usually, first the parts with mentioned component are forged, or are rolled into by blank, and by modified mistake, are then machined and nitriding.Although AISI/SAE4140H steel alloy has been useful in some nitriding application, it has also had some shortcomings.Such as, this steel contains molybdenum, and this is expensive alloying element.In addition, have been found that the object with AISI/SAE4140H composition is easy to hardening break, and therefore usually need oil quenching.Still further, the nitrided surface hardness of AISI/SAE4140H is limited to about Rockwell C hardness (HRC) 55 or less usually.
Disclosed for by being called that gas soft nitriding process carries out the alloy composition of non-hardened component manufacture, it is for the production of the low distortion steel of such as gear and other drive disk assembly.Core hardness is by adding alloy instead of being realized by thermal treatment.After by the steel bar of such as rolling or forging mechanical workout, the workpiece formed by steel alloy is by gas soft nitriding.Gas soft nitriding (being also referred to as " soft nitriding " in Japan) is faster than conventional nitriding, and forms extremely hard skin on steel and cast iron.When gas soft nitriding, under the air of the endogas (the reducing gas mixture of such as carbon monoxide and hydrogen) and ammonia that comprise moiety, parts are processed 2 hours to 6 hours under 566 DEG C (1050 Fahrenheit degree).The crust produced comprises iron carbon nitrogen complex compound.But the surface that the surface ratio of generation is obtained by nitriding is thinner, and there is no the growth of the toughness caused in the thermal treatment of nitriding in advance by workpiece.In addition, the cost that adding steel alloy increases with the core hardness realizing being comparable to quenched and tempered steel is worthless economically.
No. the 4th, 853,049, the United States Patent (USP) authorizing CalvinLoyd (' 049 patent on August 1st, 1989 submits to) in describe the trial of economic through hardening nitriding grade alloy steel.' 049 patent discloses a kind of steel alloy of through hardening nitriding grade, and it is because eliminating expensive alloys (such as molybdenum) but economy.Disclosed in the patent of ' 049, steel achieves the characteristic of expectation, comprise hardenability, to the resistance of Hardness loss during tempering, and the reaction greatly improved nitriding by using aluminium (Al) that is little, that carefully control its amount and vanadium (V).
Although disclosed in the patent of ' 049, steel alloy reduces the cost of steel alloy, and provides above-mentioned beneficial characteristics, further improvement is still possible.Especially, ' 049 patent describes and carry out multiple heat treatment process after the initial forge hot of the product produced by disclosed steel alloy.These heat treatment processes comprise the time period reaching about one hour by forging product being heated to about 870 DEG C (1600 Fahrenheit degrees) and to harden described forging product, and then with water or oil quenching to complete ferrite and pearlite microstructure to martensitic transformation.Carbide particle precipitated and to reunite and thus after providing the toughness of improvement, goods will optionally be machined into required final size, and then carry out nitriding to it being tempered to.
The bayesian micro-alloyed steel produced according to chemistry of the present invention and process solves one or more in the problems referred to above and/or other problem in the art.
Summary of the invention
In one aspect, the present invention relates to the forged steel component with the surface carburization layer formed by nitriding, described nitriding is carried out after not having thermal treatment in forging and controlled air cooling, and the composition that described forged steel component has comprises:
C:0.20 % by weight to 0.40 % by weight,
Mn:0.50 % by weight to 1.60 % by weight,
Cr:0.40 % by weight to 1.50 % by weight,
Al:0.07 % by weight to 0.30 % by weight,
V:0.03 % by weight to 0.20 % by weight,
Si:0.10 % by weight to 0.40 % by weight, and
The Fe of surplus and incidental impurities.
On the other hand, the present invention relates to the forged steel component being manufactured with and comprising following chemical constitution:
C:0.20 % by weight to 0.40 % by weight,
Mn:0.50 % by weight to 1.60 % by weight,
Cr:0.40 % by weight to 1.50 % by weight,
Al:0.07 % by weight to 0.30 % by weight,
V:0.03 % by weight to 0.20 % by weight,
Si:0.10 % by weight to 0.40 % by weight, and
The Fe of surplus and incidental impurities; And forged steel component is manufactured by following item step: forge hot, after forge hot, when not heat-treating further, controlled air cooling is greater than the main bainite microstructure of the bainite of 50%, mechanical workout and nitriding to produce at whole forged steel component.
In yet another aspect, the present invention relates to a kind of method of producing forged steel component.Described method can comprise steel billet forge hot, and then after forge hot, carries out nitriding when not heat-treating, and the composition that described steel has comprises by weight:
C:0.20 % by weight to 0.40 % by weight,
Mn:0.50 % by weight to 1.60 % by weight,
Cr:0.40 % by weight to 1.50 % by weight,
Al:0.07 % by weight to 0.30 % by weight,
V:0.03 % by weight to 0.20 % by weight,
Si:0.10 % by weight to 0.40 % by weight, and
The Fe of surplus and incidental impurities.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of the exemplary disclosed process removing typical heat treatment step;
Fig. 2 is microstructural continuous cooling transformation (CCT) figure for the production of exemplary embodiment of the present invention; With
Fig. 3 describes the schema that may be used for the exemplary open method of producing exemplary micro-alloyed steel with the nitriding characteristics strengthened.
Embodiment
Disclose microalloying, the hardenable main bainitic steel with the nitriding characteristics of enhancing of air.The bainitic steel of microalloying can produce when not needing previously to have thought before nitriding increases surface hardness and realize the necessary multiple heat treatment process of required hardness, toughness and strength characteristics economically.As shown in fig. 1, the heat treatment process after the forge hot of steel part can comprise cooling, reheat to austenitizing temperature, Quench and temper.Conventional hot forging process needs these heat treatment steps to obtain desirable strength and property of toughness, and final utilization can not be difficult to very much the suitable of mechanical workout and exempts from machined components simultaneously.If at least some in these intermediate heat treatment processes can be removed, just can be cost-saving significantly.For the capital investment of heat treatment capacity, and the maintenance cost be used on smelting furnace and miscellaneous equipment can reduce.
The main bainite microstructure that each carries into execution a plan according to the present invention be by volume comprise at least 50% the microstructural microstructure of bainite.Some embodiment by volume can have the bainite microstructure of at least 70%.Other embodiment by volume can have the bainite microstructure of at least 85%.Bainite is a kind of microstructure forming steel in about 250 DEG C to the temperature of 550 DEG C (depending on alloy content).Bainite is one of degradation production, and it can be formed when being cooled exceeding critical temperature 727 DEG C (1340 Fahrenheit degree) when austenite (occuping the face at the cubic crystal structure center of iron).Bainite microstructure can be similar to tempered martensite in outward appearance and hardness property.
The bainite of meticulous non-flaky texture generally includes cementite and is rich in the ferrite of dislocation.The ferritic high density dislocation existed in bainite makes harder than under normal circumstances of this ferrite.As shown in the anisothernal transformation in Fig. 2, be transformed into the temperature range of bainite (250 DEG C to 550 DEG C) between pearlitic temperature and martensitic temperature.When being formed during continuous coo1ing, the speed of cooling forming bainite is quicker than the speed of cooling formed needed for perlite, but than the speed of cooling formed needed for martensite more not fast (in the steel of identical component).Difference according to the present invention carries into execution a plan, and first the micro-alloyed steel with chemical property discussed in more detail below can be heated to about 1100 DEG C to 1250 DEG C or higher austenitizing temperature.Then steel can be caused desired shape by forge hot, and from forging temperature controlled cooling model to realize bainite microstructure.For the cooling after forge hot, gas blower can be used to carry out air cooling or force air cooling.Substitutingly to carry into execution a plan at each, steel can be quickly cooled to about eutectoid, and be then cooled to the scope between about 900 DEG C to 500 DEG C lentamente.Substitutingly to carry into execution a plan other, steel can be rapidly cooled to about 500 DEG C to 300 DEG C after forge hot, and can when from about 500 DEG C to remaining on equilibrium temperature when 300 DEG C of scopes to promote bainite transformation.
By reference to anisothernal transformation to learn the scope of the rate of cooling by bainite transformation district, and thus the rate of cooling scope determined can be controlled to.Anisothernal transformation can prepare in advance, stores in a database, or is made in addition and can be used for controlled cooling model process.When cooling between about 900 DEG C and 500 DEG C, forging product can use other component of fan or circulating cooling air to carry out air cooling with obtain fall into about per second 1 DEG C to 5 DEG C or per minute 60 DEG C per second to the rate of cooling in the scope of per minute 300 DEG C.Although the temperature that most of alloying element will reduce needed for maximum rate formation bainite, carbon is the most effective in the case.The hardness that bainite has usually is greater than pearlitic representative hardness and is less than martensitic hardness.Perlite in microstructure can cause toughness to reduce.Select according to the composition of the micro-alloyed steel of each embodiment of the present invention and process to avoid or at least to minimize the pearlitic amount of existence.In business practice, although a small amount of perlite (such as, being less than 2% by volume) inevitably may be there is, particularly in the center of large section, should note minimizing pearlitic existence and impact.
Bainite microstructure has the two-phase microstructure be made up of ferrite and iron carbide substantially.According to the austenitic composition during hot forging process and the rate of cooling after forge hot, there is change in the form of gained bainite.Gained microstructure is called as upper bainite or lower bainite.Upper bainite can be described as and is usually found in parallel group to form the aggregate of the ferrite lath of plate like region.The Carbide Phases relevant with upper bainite is deposited in original austenite crystal prevention (interior lath regions) place, and according to carbon content, these carbide can form almost complete carbide membrane between lath boundaries.Lower bainite also comprises the aggregate of ferrite and carbide.Carbide precipitation is in the inside of ferrite sheet.Carbide precipitation scale is very meticulous and be generally clavate or blade-shaped.Therefore, bainite microstructure is conducive to when not carrying out extra heat treatment obtaining the hardness value between perlitic steel and the hardness value of martensitic steel after initial cooling.The material behavior of microalloying and forged steel can according to the particular type of the alloying element be included in composition and quantity in wide variation.The composition of the alloying element that each embodiment according to the present invention comprises produce have previously only by being included in intermediate heat treatment step after the forge hot that reheats to austenitizing temperature, the steel part of intensity, hardness and property of toughness that Quench and temper obtains.
Above-mentioned favourable material behavior is found to obtain along with the increase of the microstructural volume percent of bainite largely.Therefore, by volume the microstructural parts of the bainite of 70% can present than by volume 50% larger intensity, hardness and the property of toughness of the microstructural parts of bainite.In addition, by volume the microstructural parts of the bainite of 85% or higher can present than by volume 70% the microstructural parts of the bainite intensity, hardness and the property of toughness that further enhance.As shown in Figure 1, carry into execution a plan according to of the present invention each, before final mechanical workout and nitrogenize forging product, can remove reheat to the intermediate heat treatment of austenitizing temperature, quenching, tempering, second time reheat, second time quenching and second time tempering.Can also select to be added to according to the alloying element of the composition of each embodiment of the present invention to obtain the bainite microstructure of the volume required percentage ratio of whole parts, and the different cooling rate that no matter may stand in the different segment of parts with different thickness or part.
As hereafter discussing in further detail, carry into execution a plan according to of the present invention each, two key elements in micro-alloyed steel composition are aluminium (Al) and vanadium (V).Al and V improves the nitriding ability of alloy in nitriding process.In order to realize bainite microstructure during the controlled process of cooling performed in the present invention, Al and V a small amount of in micro-alloyed steel is reacted by the nitrogen (N) be dissolved into when solidifying in steel with a small amount of (being equivalent to the magnitude of 150/1000000ths parts), contributes to the strengthening of steel.V and Al and the reaction of N of dissolving form the throw out of fine granular or vanadium nitride (VN) and aluminium nitride (AlN), thus contribute to the lattice strengthening micro-alloyed steel.Because the quantity of the N dissolved is very little, so be left unreacted V and Al after the cooling process, and the N that can diffuse into the surface of object during nitriding process after mechanical workout is combined.
Various different nitriding method can be used.Conventional nitriding method is gas nitriding.
Alternative method can comprise salt bath nitriding and plasma nitriding.In gas nitriding, donor is a kind of nitrogen-rich gas, normally ammonia (NH
3), this is also why sometimes it is called as ammonia nitriding.When ammonia touches by heated parts, it is separated into nitrogen and hydrogen.Then the surface that nitrogen is diffused into material forms nitride layer.The thickness of gained nitride layer and phase composite can be passed through select and for process described in required specified property optimization.
Have been found that after forge hot process of cooling in of the present invention each carries into execution a plan after, remaining V and Al strengthens the nitriding feature of micro-alloyed steel, thus strengthens wear resistance and strengthen machined components.The bainite microstructure with V and Al carries out also can present same forge hot after controlled air cooling after quenching, reheat, the same or analogous hardness that obtains of Quench and temper and strength characteristics again.The body-centered teteragonal crystalline structure of the martensitic microstructure that the rapid quenching after micro-alloyed steel does not have because of forge hot produces is cooled according to controlled air according to the present invention.By can martensitic microstructure be presented at oil or quenching-in water from the micro-alloyed steel after hot forging temperature cools fast.The Rockwell C hardness (HRC) that can have after martensitic microstructure quenching is 50.Then, the typical method processing this martensitic microstructure steel can comprise the austenitizing temperature reheating to about 870 DEG C, again quench, and then by again reheating about 550 DEG C of tempering to 590 DEG C, thus make steel soften to Rockwell C hardness about 30.Carry into execution a plan according to of the present invention each, for the production of be mainly the microstructural controlled air process of cooling of bainite can when not quenching completely, reheat, Quench and temper etc. previously required step produce the Rockwell C hardness of same rigidity 30.As mentioned above, main bainite microstructure can containing the bainite microstructure being greater than 50% by volume.About 35 Rockwell C hardness can be fallen into in the scope of 45 Rockwell C hardness according to the hardness of the present invention after air cooling.
The micro-alloyed steel that each carries into execution a plan according to the present invention can have chemical constitution by weight as listed in Table 1:
Table 1: the composition of micro-alloyed steel by weight percentage.
Carbon is containing helping accessible hardness level, and hardening depth.Carry into execution a plan according to of the present invention each, amount is at least 0.20 % by weight to maintain suitable core hardness after tempering, and is no more than about 0.40 % by weight to guarantee the resistance to hardening crack and the appropriate reaction to nitriding.Have been found that so water quenching can cause breaking of complicated shape goods or be out of shape if carbon content is greater than about 0.34 % by weight, and in the case, not fiercer quench medium may be needed, such as oil.Air cooling can be carried out according to selecting on the anisothernal transformation of Fig. 2 cooling curve according to the microalloy bainitic steel that each carries into execution a plan of the present invention.
Manganese contributes to dark hardenability and is therefore present in all hardenable steel alloy grades.The manganese that disclosed steel alloy contains at least 0.50 % by weight is to guarantee suitable core hardness and containing being no more than about 1.60% to prevent from breaking.Except allow 0.50 % by weight to 1.60 % by weight wide region except, from 1.00% to 1.30% compared with the manganese of close limit be conducive to keep to thermal treatment reaction homogeneity.
Chromium contributes to the hardenability of Steel Alloy of the present invention, but also is a kind of excellent nitride forming composition, thus strengthens nitriding characteristics.In order to realize these effects, more advantageously at least should there is the chromium of 0.90% in the chromium of minimum needs 0.40%.In order to avoid embrittlement, the amount of chromium should be limited in maximum 1.50%, and preferably no more than about 1.20%.
Aluminium contributes to hardenability, and is a kind of good nitride forming composition.The content that aluminium exists should at least 0.07%, and is preferably at least 0.10%.If the content that aluminium exists is less than about 0.07%, so not only almost do not observe the improvement of hardenability or nitride reaction, and its benefit is also inconsistent.And have been found that when the amount of aluminium is greater than 0.30% contribute to nitriding ability, but surperficial embrittlement also has the trend of increase.Therefore, expect to make the upper limit of aluminium keep being not more than 0.30%, and be advantageously not more than about 0.20%.Have been found that the aluminium that has in steel alloy of the present invention is consistently improving in the stated limit of hardenability.
Vanadium is also a kind of composition in alloy composition of the present invention, and its amount existed must be at least 0.03%, to realize the conforming great enhancing on surface and core hardness.The vanadium that content is greater than 0.20% obviously can't strengthen the hardenability of nitride reaction or material.Due to these reasons, the limit value of vanadium is at least 0.03%, and is not more than 0.20%; And advantageously from 0.05% to 0.10%, to realize the optimal economic purposes of this composition.
Have been found that aluminium and the vanadium unique combination in stated limit contributes to improving nitride reaction very much, thus the nitriding time needed for reducing, and increase surface hardness and the degree of depth.In addition, aluminium and the vanadium unique combination in stated limit contributes to hardenability and temper resistance.
Except the element of nonessential or residual quantity that may exist to very low amount, the surplus materials of alloy composition is essentially iron.Such as, the silicon (Si) of commercial generally acknowledged specified amount is used to the deoxidation of molten steel, but also contributes to being formed the bainite with the carbides-free improving toughness.For this purpose, the content that silicon exists can be at least 0.10%.The amount of providing of titanium (Ti) can also between about 0.02% to 0.06%, with the grain coarsening before and after preventing from forging.The permission content of sulphur (S) (a small amount of sulphur can help lend some impetus to mechanical workout) is not more than about 0.10%, and is preferably not more than 0.04%, to prevent from losing ductility.Content can cause embrittlement higher than the phosphorus (P) of 0.05%, and preferably its upper limit should more than 0.035%.Usually within the tolerance that the content existing for other element being regarded as incidental impurities can commercially be generally acknowledged.
The finished product (such as axle, shaft coupling and gear) with mentioned component advantageously, after austenitizing temperature micro-alloyed steel being heated to about 1100 DEG C to 1250 DEG C, are begun to take shape as desired shape by forging or rolling.Then, shaping goods, as mentioned above by controlled cooling model, to generate main bainite microstructure, are then processed into required final size, and then by nitriding.
Fig. 3 shows according to the illustrative methods that may be used for generating main bainite microalloying and nitriding steel parts that each carries into execution a plan of the present invention.Fig. 3 will discuss in detail, to further illustrate disclosed concept in hereafter fragment.
Industrial applicibility
According to the steel that each carries into execution a plan of the present invention and steel producing method, the heat treatment step usually carried out after can passing through to remove forge hot is to reduce costs.Disclosed microalloying, forging, gas can harden and nitriding steel parts can provide the hardness similar with heat-treated steel parts to aforementioned forge hot and intensity.After carrying out controlled air cooling from hot forging temperature, add the microalloy element of vanadium and aluminium to generate main bainite microstructure, and the nitriding heat treatment process after strengthening mechanical workout.
As shown in Figure 3, in step 320, the micro-alloyed steel with composition shown in table 1 above can be heated to the austenitizing temperature of about 1100 DEG C to 1260 DEG C.Each exemplary types of parts of manufacturing of carrying into execution a plan according to the present invention can comprise the transmission gear ring of various machine, engine gear, wheel hub, axle and other drivetrain components.The size of parts determines the size of steel billet, and first steel billet is heated to austenitizing temperature according to step 320.
In step 322, the blank of heating can be become required structure by forge hot.After forge hot, step 324 can comprise with certain rate of cooling air cooling hot forging product, makes in whole hot-forged parts, define main bainite microstructure.As shown in the anisothernal transformation of Fig. 2, rate of cooling can be selected to avoid martensitic microstructure or to be mainly the microstructural formation of ferrite and pearlite.In of the present invention each carries into execution a plan, along with steel be cooled to about 500 DEG C from about 900 DEG C time, forge hot steel can to fall into about 1 DEG C of speed to 5 DEG C of scopes cooling per second.At whole forge hot steel part, main bainite microstructure can be the microstructure with the bainite being greater than 50%, or be more advantageously the microstructure with the bainite being greater than 70%, or be more advantageously also the microstructure with the bainite being greater than 85%.
In step 326, the microalloy element of vanadium (V) and aluminium (Al) can react to be formed at solidificating period and the nitrogen dissolved in steel the finer precipitates or particulate of strengthening the microstructural lattice of steel.The amount of nitrogen (N) is usually quite little, and can be 150/1000000ths (ppm) rank.Therefore, most of V and Al remains freely, with during nitriding process with can be combined by more N of introducing of subsequent stage after machining.
In step 328, after steel part carries out air cooling, it can use conventional mechanical processing technology to carry out mechanical workout.After machining, in a step 330, machined components can use following technology to carry out nitriding, and described technology can be included in has such as ammonia (NH
3) nitrogen-rich gas air in heated mechanical processing component.Nitriding is to produce the heat treatment process on case-hardened surface in surface nitrogen being diffused into parts.After some V and Al react at solidificating period and the N dissolved in steel, remaining V and Al by with nitriding process during the N increased response that provides nitriding process.
Those of ordinary skill in the art, by aobvious and easily know without departing from the scope of the invention, can make various modifications and changes to disclosed micro-alloyed steel and method steel being formed finished product.By considering specification sheets disclosed herein and practice, those of ordinary skill in the art easily know alternate implementations by showing.Specification sheets and example are intended to be regarded as merely exemplary, and true scope of the present invention is pointed out by appended claims and equivalent thereof.
Claims (10)
1. have a forged steel component for the surface nitride layer formed by nitriding, described nitriding is carried out after cooling through forge hot and controlled air but do not heat-treat, and the composition of described forged steel component comprises:
C:0.20 % by weight to 0.40 % by weight,
Mn:0.50 % by weight to 1.60 % by weight,
Cr:0.40 % by weight to 1.50 % by weight,
Al:0.07 % by weight to 0.30 % by weight,
V:0.03 % by weight to 0.20 % by weight,
Si:0.10 % by weight to 0.40 % by weight, and
The Fe of surplus and incidental impurities.
2. forged steel component according to claim 1, wherein said steel part was first heated to about 1230 degrees Celsius ± 30 degrees Celsius before forge hot.
3. forged steel component according to claim 1, wherein after described controlled air cooling, the microstructure of described forged steel component is greater than the bainite of 50% by volume.
4. forged steel component according to claim 1, wherein after the cooling of described controlled air, the microstructure of described forged steel component be greater than by volume 85% bainite.
5. forged steel component according to claim 1, the Rockwell C hardness that at least one surface of wherein said forged steel component has after described controlled air cooling is at least 25.
6. forged steel component according to claim 1, wherein the hardness of whole described forged steel component falls in the scope between about 25 Rockwell C hardness to 30 Rockwell C hardness.
7. forged steel component according to claim 1, wherein after forging, described controlled air cools between about 900 degrees Celsius to 500 degrees Celsius to carry out from 1 degree Celsius per second to the speed in 5 degree Celsius range per second.
8. produce a method for forged steel component, comprising:
By steel billet forge hot, and then after described forge hot, carry out nitriding when not heat-treating, the composition that described steel has comprises by weight:
C:0.20 % by weight to 0.40 % by weight,
Mn:0.50 % by weight to 1.60 % by weight,
Cr:0.40 % by weight to 1.50 % by weight,
Al:0.07 % by weight to 0.30 % by weight,
V:0.03 % by weight to 0.20 % by weight,
Si:0.10 % by weight to 0.40 % by weight, and
The Fe of surplus and incidental impurities.
9. method according to claim 8, by the austenitizing temperature of described heating steel billet to about 1100 degrees Celsius to 1260 degrees Celsius before being also included in described forge hot.
10. method according to claim 9, also comprises:
After described forge hot, forged steel component described in air cooling, comprises, and along with described forged steel component cools between about 900 degrees Celsius and 500 degrees Celsius, controls air cooling speed and makes in its scope falling into about 1 degree Celsius to 5 degrees Celsius per second per second.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US13/848,812 US20140283954A1 (en) | 2013-03-22 | 2013-03-22 | Bainitic microalloy steel with enhanced nitriding characteristics |
| US13/848812 | 2013-03-22 | ||
| PCT/US2014/031398 WO2014153491A1 (en) | 2013-03-22 | 2014-03-21 | Bainitic microalloy steel with enhanced nitriding characteristics |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN105143473A true CN105143473A (en) | 2015-12-09 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201480016291.1A Pending CN105143473A (en) | 2013-03-22 | 2014-03-21 | Bainitic microalloy steel with enhanced nitriding characteristics |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US20140283954A1 (en) |
| EP (1) | EP2976436A1 (en) |
| JP (1) | JP2016519715A (en) |
| KR (1) | KR20150133759A (en) |
| CN (1) | CN105143473A (en) |
| WO (1) | WO2014153491A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105586528A (en) * | 2015-12-18 | 2016-05-18 | 天津市东达伟业机车车辆有限公司 | Alloy steel and heat treatment technique thereof |
| CN106119705A (en) * | 2016-06-22 | 2016-11-16 | 陕西法士特齿轮有限责任公司 | A kind of Nitriding on Gear steel and manufacture method |
| CN116200657A (en) * | 2022-12-23 | 2023-06-02 | 西安法士特汽车传动有限公司 | Bainite steel, thin-wall annular part of Bainite steel and manufacturing method thereof |
| WO2023109106A1 (en) * | 2021-12-15 | 2023-06-22 | 河北工业职业技术学院 | Short-process bainite hot-work die and preparation method therefor |
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| KR102009635B1 (en) * | 2015-03-24 | 2019-08-12 | 제이에프이 스틸 가부시키가이샤 | Steel for nitrocarburizing and nitrocarburized component, and methods of producing same |
| KR101676244B1 (en) * | 2015-04-14 | 2016-11-29 | 현대자동차주식회사 | Carbon steel compositions reduced thermal strain for steering rack bar and method for manufacturing the same |
| ES2733805T3 (en) * | 2015-11-16 | 2019-12-03 | Deutsche Edelstahlwerke Specialty Steel Gmbh & Co Kg | Structural fine steel with bainitic structure, forged part manufactured from it and procedure for manufacturing a forged part |
| FR3082529B1 (en) * | 2018-06-18 | 2020-09-11 | Institut De Recherche Tech Materiaux Metallurgie Procedes | NITRURATION CURING PROCESS |
| CN114480971A (en) * | 2022-01-26 | 2022-05-13 | 包头钢铁（集团）有限责任公司 | 38CrMoAl steel and preparation method thereof |
| EP4464810A4 (en) * | 2022-01-28 | 2025-11-19 | Jfe Steel Corp | STEEL COMPONENT AND MANUFACTURING METHOD FOR IT |
| PL449407A1 (en) * | 2024-07-30 | 2025-02-03 | Politechnika Warszawska | Method of heat treatment of medium or high carbon alloy steel, high carbon alloy steel produced by this method and its use |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07116502B2 (en) * | 1988-12-03 | 1995-12-13 | マツダ株式会社 | Steel member manufacturing method |
| JPH0892687A (en) * | 1994-09-22 | 1996-04-09 | Kobe Steel Ltd | High strength and high toughness non-heattreated steel for hot forging and its production |
| JP2991064B2 (en) * | 1994-12-15 | 1999-12-20 | 住友金属工業株式会社 | Non-tempered nitrided forged steel and non-tempered nitrided forged products |
| JP4305891B2 (en) * | 2000-10-26 | 2009-07-29 | 日立金属株式会社 | Hot forging die steel and hot forging die |
| JP5123335B2 (en) * | 2010-01-28 | 2013-01-23 | 本田技研工業株式会社 | Crankshaft and manufacturing method thereof |
-
2013
- 2013-03-22 US US13/848,812 patent/US20140283954A1/en not_active Abandoned
-
2014
- 2014-03-21 KR KR1020157029165A patent/KR20150133759A/en not_active Withdrawn
- 2014-03-21 CN CN201480016291.1A patent/CN105143473A/en active Pending
- 2014-03-21 WO PCT/US2014/031398 patent/WO2014153491A1/en not_active Ceased
- 2014-03-21 JP JP2016504369A patent/JP2016519715A/en active Pending
- 2014-03-21 EP EP14768272.8A patent/EP2976436A1/en not_active Withdrawn
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105586528A (en) * | 2015-12-18 | 2016-05-18 | 天津市东达伟业机车车辆有限公司 | Alloy steel and heat treatment technique thereof |
| CN105586528B (en) * | 2015-12-18 | 2018-02-23 | 天津市东达伟业机车车辆有限公司 | A kind of steel alloy and its Technology for Heating Processing |
| CN106119705A (en) * | 2016-06-22 | 2016-11-16 | 陕西法士特齿轮有限责任公司 | A kind of Nitriding on Gear steel and manufacture method |
| WO2023109106A1 (en) * | 2021-12-15 | 2023-06-22 | 河北工业职业技术学院 | Short-process bainite hot-work die and preparation method therefor |
| CN116200657A (en) * | 2022-12-23 | 2023-06-02 | 西安法士特汽车传动有限公司 | Bainite steel, thin-wall annular part of Bainite steel and manufacturing method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| US20140283954A1 (en) | 2014-09-25 |
| JP2016519715A (en) | 2016-07-07 |
| WO2014153491A1 (en) | 2014-09-25 |
| EP2976436A1 (en) | 2016-01-27 |
| KR20150133759A (en) | 2015-11-30 |
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Application publication date: 20151209 |