CN100342038C - Cold-worked steels with packet-lath martensite/austenite microstructure - Google Patents
Cold-worked steels with packet-lath martensite/austenite microstructure Download PDFInfo
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Abstract
Strain-hardened steel alloys having a high tensile strength are prepared by cold working of alloys whose microstructure includes grains in which laths of martensite alternate with thin films of stabilized austenite. Due to the high dislocation density of this microstructure and the tendency of the strains to move between the martensite and austenite phases, the strains created by cold working provide the microstructure with unique mechanical properties including a high tensile strength. Surprisingly, this is achieved without the need for intermediate heat treatments (patenting, in the case of steel wire) of the steel between cold working reductions.
Description
Cross-reference to related applications
Present patent application requires in the right of priority of U.S.'s patent application formerly 60/427830 of submission on November 19th, 2002.The reference that the content of patent application formerly 60/427830 is quoted as this specification sheets with its whole content.
Background of invention
1, invention field
The present invention relates to low-carbon (LC) and medium carbon steel alloy technology, particularly those have high strength and flexible Steel Alloy, and the cold shaping of these alloys.
2, DESCRIPTION OF THE PRIOR ART
The important step of processing high-performance steel is cold working, generally includes by drawing, and pushes, and the cold forging or the operation of rolling are carried out a series of compressions and/or expansion.Cold working causes steel generation viscous deformation, produces strain hardening when making steel form final application of shape.Cold working realizes by wire drawing for steel wire, normally carries out with consecutive steps with intermediate heat treatment, and be " lead bath quenching " for its term of steel wire.
High-tensile steel wires are a kind of high-performance steels, are suitable for various engineerings and use, and comprise tyre cord, wireline and be used for the strand of prestressed concrete arrangement of reinforcement.The most frequently used steel is middle carbon or high carbon steel in the high-tensile steel wires.In forming the canonical process of steel wire, need be in some steps cold drawn hot-rolled rods with perlite microtexture, handle the softening cold drawn perlite that is used to continue by middle lead bath quenching.Such as can be in some steps being approximately 3 millimeters to diameter with the hot-rolled rods of about 5.5 mm dias is rough.Can carry out lead bath quenching at 850-900 ℃ then, make the steel austenitizing, make steel be transformed into the perlite thin slice at 500-550 ℃ subsequently.Then steel is immersed in the hydrochloric acid scale that forms when removing lead bath quenching.After soaking is some steps of further drawing, and makes reduced arrive about 1 millimeter, then further lead bath quenching and immersion.Divide some steps finally to draw then, such as being about 0.4 millimeter, obtain the character that intensity etc. requires up to the final diameter that requires.Be for further processing according to end-use subsequently, such as twisting with the fingers thigh.
The purpose of initial lead bath quench treatment is to form the wire rod with thin slice pearlitic texture, requires low transition temperature.For the temperature control that realizes requiring, in molten lead bath, carry out this process usually.Drawing in the step subsequently, draw wire rod to true strain (being defined as follows) and be 6-7, thereby obtain the high strength of about 3000 MPas.For conventional pearlitic wires, have only by a series of lead bath quenchings processing to obtain these high strain and intensity.Do not have these lead bath quenchings to handle, cold drawn meeting causes the perlite thin slice shear crack to occur.Owing to need to use molten lead bath,, also can cause damage to environment so whole process cost is very high.
Cold working also is used to make expandable steel tubular, and promptly expansible pipeline on the spot is underground sometimes.
Recently the development result in Steel Alloy field is to form to contain staggered martensite and austenite microtexture mutually, and martensite wherein exists with the lath form of being separated by austenite film.Microtexture is a fused grain, contains some martensite laths of being separated by austenite film in the single crystal grain, in some cases, has an austenite shell to wrap up each crystal grain.These structures are called as " dislocated lath martensite " structure or " trooping-the lath martensite/austenite " structure.The patent that discloses these microtextures is as described below, all as a reference with its whole content:
4170497 (Gareth Thomas and Bangaru V.N.Rao) are according to announcing on the October 9th, 1979 that applies for of submitting on August 24th, 1977.
4170499 (Gareth Thomas and Bangaru V.N.Rao) are according to announcing that this application is the continuation of 24, institutes submit applications in above-mentioned 1977 on August on the October 9th, 1979 that applies for of submitting on September 14th, 1978.
4671827 (Gareth Thomas, Nack J.Kim and Ramamoorthy Ramesh) are according to announcing on the June 9th, 1987 that applies for of submitting on October 11st, 1985.
6273968B1 (Gareth Thomas) is according to announcing the August 14 calendar year 2001 that applies for of submitting on March 28th, 2000.
Though these microtextures can both provide some performance advantage, such as high corrosion resistance, also do not know so far when these microtextures exist, can simplify or delete the procedure of processing that is usually used in Steel Alloy.
What have further potential relation with the present invention is open not use lead bath quenching that rod iron and wire rod are carried out cold worked two parts of United States Patent (USP)s.These patents are:
4613385 (Gareth Thomas and Alvin H.Nakagawa) are according to announcing on the September 23rd, 1986 that applies for of submitting to December 9 nineteen eighty-two.
4619714 (Gareth Thomas, Jae-Hwan Ahn and Nack-Joon Kim) are according to announcing that this application is the continuation of 6, institutes submit applications in above-mentioned 1984 on August on the October 28th, 1986 that applies for of submitting on November 29th, 1984.
These patents also with its whole content as a reference.Think that the steel microstructure in these patents is different from aforementioned four patents.
Summary of the invention
Have now found that to troop-unique distinction of lath martensite/austenite microstructure is its crystallographic characteristics, and how these features make it that cold working is produced reaction.Because it is mobile between mutually that the high dislocation density of this microtexture and the strain in the structure are easy at martensite and austenite,, cold working comprises the unique mechanical properties of high tensile so having microtexture.The result is, need not intermediate heat treatment and just can carry out cold working to these alloys, still can obtain the tensile strength that can be equal to the conventional steel alloys that processes through the cold working with intermediate heat treatment simultaneously.Troop for having-steel wire of lath martensite/austenite microstructure, lead bath quenching was handled and just can be carried out cold working in the middle of the present invention found need not.Therefore in the present invention, troop for having-carbon steel alloy of lath martensite/austenite microstructure, it is the carbon steel alloy that comprises the martensite lath that interlocks with the residual austenite film in the microtexture, preferably do not carry out intermediate heat treatment, and extremely such reduction of cold shaping: it is enough to obtain about 150 ksi or higher tensile strength, be equivalent to about 1085 MPas (that is newton/square millimeter) or more than.It is significant especially being cold working to 2000 MPas (290 ksi) or above tensile strength, in fact adopt method of the present invention, can obtain 3000 MPas (435 ksi) and up to the tensile strength of 4000 MPas (580 ksi).These numerical value are proximate; Being accurate to millesimal conversion factor is that 6.895 MPas equal 1 ksi.
Advantage of the present invention can be generalized to the simple cluster-lath martensite/austenite microstructure that does not contain ferrite or contain a little ferrite, can also be generalized to the microtexture that comprises with the trooping of ferrite crystal grain consolidation-lath crystal grain, be generalized to the variant of these structures, comprise trooping-structure that lath crystal grain is wrapped up by austenite shell, the structure that does not contain alternate carbide precipitation, and austenite film wherein has the structure of even orientation.With above-mentioned patent 4613385 and 4619714 disclosed contents, discovery troops-and to produce this reaction to cold working be astonishing to the lath martensite/austenite microstructure, is lower than martensitic yield strength because the ferrite in the microtexture of these patents has.The result is, ferrite preferably absorbs the strain that cold working produces, and martensite can not produce reaction to cold working, up to the processed degree that is higher than the martensite yield strength that is hardened to of ferritic phase.In microtexture of the present invention, the ferrite of lower aq, or do not contain ferrite, cause martensite to absorb strain in the stage early of cold working process.Martensite and ferrite are being diverse aspect crystalline structure and the sclerosis behavior.
Specify by following, can understand these and other features of the present invention better, purpose, advantage and embodiment.
Brief Description Of Drawings
Fig. 1 be two-phase troop-two kinds of Steel Alloys of lath martensite/austenite microstructure do not comprise that through the present invention tensile strength after the cold working of intermediate heat treatment is to the figure of true overall strain.
Fig. 2 be three-phase troop-the three kinds of Steel Alloys and the two-phase of lath martensite/austenite/ferrite microtexture troop-a kind of Steel Alloy of lath martensite/austenite microstructure do not comprise that through the present invention tensile strength after the cold working of intermediate heat treatment is to the figure of true overall strain.
Specifying of invention and preferred embodiment
When implementing cold working of the present invention, can use used cold processing technique and equipment in existing other Steel Alloys and the microtexture field.For the alloy of bloom, billet, shaped steel, slab or sheet form, can be included in steel rolling between pressure roller or other pressing units in the cold working, reduce its thickness and its length that stretches., can repeatedly repeatedly reduce when carrying out cold working by rolling by milling train.For bar-shaped or wire workpiece, cold working can comprise cold drawn or be pressed through drawing-die.For repeatedly reduction, workpiece is extruded the drawing-die of dwindling by a series of successives.With the axle that is positioned at annular drawing-die inside, draw steel by this drawing-die, can obtain tubing.For multi-pass operations, draw ducted axle this pipeline is further drawn by circlet shape drawing-die more with being positioned at.
Carry out cold worked temperature and be lower than the minimum temperature that recrystallization takes place.Therefore appropriate temperature can not cause any phase transformation in steel.For carbon steel, recrystallization takes place at about 1000 ℃ (1832 ) usually, is preferably lower than this temperature when therefore carrying out cold working of the present invention.Preferably carry out cold working at about 500 ℃ (932 ) or following temperature, be more preferably about 100 ℃ (212 ) or below, most preferably be below the about 25 ℃ envrionment temperature.
Cold working can be carried out once or carry out repeatedly continuously.Under the both of these case, can carry out intermediate heat treatment (that is, being meant " lead bath quenching "), further improve character, but the character that is only produced by cold working is sufficiently high, does not need to carry out intermediate heat treatment, does not preferably carry out intermediate heat treatment for steel wire.Each economy can have nothing in common with each other to the present invention and non-key, but economy should the disruptive degree take place even as big as avoiding that hardening of steel is arrived under the less situation of reduction total amount.In most of the cases, preferred each economy is about 20% at least, be more preferably at every turn at least about 25%, and most preferably be each about 25% to 50%.Each economy depends in part on following factor at least: die angle and draw efficiency factor.Die angle is big more, avoids the generative center needed minimum reduction that ftractures big more.But it is low more to draw efficiency factor, and the steel maximum reduction that then has given strain-hardening index is low more.Usually between these two kinds of competition factors, obtain compromise.Aspect the tensile strength of the finished product, preferably carry out cold working and make tensile strength in about 150 to 500 ksi scopes.
Method of the present invention can be applied to as above referenced patents described have troop-carbon steel alloy of lath martensite/austenite microstructure, and the U.S. Patent application of submitting to December 15 calendar year 2001 10/017847 (name is called " the nano combined steel of three-phase ", the invention people is Kusinski, G.J., Pollack, D. and Thomas, G.) and in December 14 calendar year 2001 submit to 10/017879 (name is called " nano combined martensitic steel ", the invention people is Kusinski, G.J., Pollack D. and Thomas, the G.) carbon steel alloy described in, these patent applications are all with its whole content as a reference.Want to form and troop-the lath martensite/austenite microstructure, alloy composite has about 300 ℃ or above martensite usually and begins transition temperature M
s, preferably 350 ℃ or more than.Though alloying element can influence M usually
s, but to M
sThe alloying element that produces maximum effect is a carbon, can obtain M below being limited in 0.35 weight % by the carbon content with alloy
sAlloy greater than 300 ℃.In a preferred embodiment of the invention, carbon content is in about scope of 0.03 to 0.35%, and in preferred embodiment, this scope is about 0.05 to 0.33%, and these per-cents all are weight percents.Other alloying elements are enough to as forming the compact grained nucleation site such as the content of molybdenum, titanium, niobium and aluminium, but its concentration is low to moderate again and is enough to avoid influencing the character of finishing alloy.Its concentration also should be low to moderate to be enough to avoid forming inclusion and other big precipitations, and this can make steel that early fracture takes place easily.In certain embodiments of the present invention, it is favourable containing one or more austenite stable elements, such as nitrogen, manganese, nickel, copper and zinc.Wherein particularly preferably be manganese and nickel.When having nickel, preferred nickel concentration is in about scope of 0.25 to 5%, and when having manganese, preferred manganese concentration is in about scope of 0.25 to 6%.In many embodiment of the present invention, also contain chromium, when having chromium, its concentration preferably about 0.5 to 12%.All concentration here all are weight percents.
In the alloy of certain embodiments of the invention except troop-also comprise ferritic phase (triple-phase alloys) the lath martensite/austenite crystal grain, only contain in other alloys and troop-lath martensite/austenite crystal grain, do not comprise ferritic phase (two phase alloys).Generally speaking, whether exist ferritic phase by the type of heat treatment decision of initial austenite in the stage.Select appropriate temperature, steel can be transformed into the austenite phase or contain austenite and ferritic two phase structure.In addition, can select or regulate alloy composite, from the initial cooling stages of the alloy of austenite phase, form ferrite, perhaps avoid when cooling, forming ferrite, promptly form at further cooling austenite troop-the lath microtexture before, avoid forming ferrite crystal grain.
As mentioned above, use in some cases have troop-alloy of lath martensite/austenite microstructure is favourable, austenite film in wherein single trooping-lath crystal grain all almost is a same orientation, though crystalline orientation can have nothing in common with each other, the austenite film in perhaps single trooping-lath crystal grain all has identical high preferred orientation.By size of microcrystal is limited in 10 microns or below, can reach a back purpose.Preferred size of microcrystal in this case most preferably is about 5 to 9 microns in about 1 to 10 micron scope.
Preparation do not contain ferritic two-phase and troops-during lath martensite/austenite microstructure (i.e. " two-phase " microtexture), at first select alloy compositions, and with appropriate ratio with these components mixing.Then under sufficiently long time and sufficiently high temperature to blending ingredients homogenize (" soaking ") handle, form the even austenitic structure that all elements and component all are in solid solution state.Temperature is higher than austenite recrystallization temperature, can form very compact grained level but preferably be in.Austenite recrystallization temperature changes with alloy composition usually, but is conspicuous to those skilled in the art on the whole.In most of the cases, under the temperature of 800 to 1150 ℃ of scopes, carry out equal thermal treatment and can obtain best result.Under this temperature, can be rolled alloy, forging or combination operation.
Finish homogenize after, alloy is cooled off combination operation with grain refining, up to the size of microcrystal that obtains to require, as indicated above having nothing in common with each other.Can carry out grain refining step by step, but final grain refining normally be higher than or medium temperature near austenite recrystallization temperature under realize.At first rolled alloy under homogenization temperature produces dynamic recrystallization, is cooled to medium temperature then, rolling once more further dynamic recrystallization.Medium temperature is in austenite recrystallization temperature with than between this its high about 50 ℃ temperature.For austenite recrystallization temperature is about 900 ℃ alloy composite, preferably alloy is cooled to the medium temperature between about 900 to 950 ℃, most preferably between about 900 to 925 ℃.For austenite recrystallization temperature is about 820 ℃ alloy composite, and preferred medium temperature is about 850 ℃.Can also adopt and forge or additive method well known by persons skilled in the art realization dynamic recrystallization.Dynamic recrystallization generation 10% or above grain size reduction, in many cases, grain size reduction is about 30 to 90%.
After the size of microcrystal that to require, alloy is cooled to martensite and begins transition temperature M from being higher than austenite recrystallization temperature
sQuench,, austenite matrix is transformed into troops-the lath martensite/austenite microstructure then by the martensitic transformation zone.When having the ferrite crystal in the austenite matrix, only change and in austenite matrix, take place.Best rate of cooling forms with alloy and the hardenability energy changes.The austenite crystal that making troops makes with rolling sequence have about equally than small particle size, but have only austenite remaining in these crystal grain to be arranged in film, be to be arranged in parcel each is trooped-shell of lath crystal grain in some cases.When austenite film on crystalline orientation single variation takes place, can obtain size of microcrystal less than 50 microns by control process.
Also can only realize grain refining, replace dynamic recrystallization, meet the requirements of size of microcrystal by thermal treatment.When making in this way, alloy is quenched, and then be heated to and approximate austenite recrystallization or lower slightly temperature greatly, quench once more, reach or get back to and troop-the lath martensite/austenite microstructure according to described in the leading portion.Preferably once more Heating temperature than in high about 50 ℃ of the austenite recrystallization temperature, such as being about 870 ℃.
Carry out following procedure of processing according to method as known in the art: the heating alloy composite is to the austenite phase, adopt controlled rollingly or forge cooled alloy and obtain the economy and the size of microcrystal that require, austenite crystal is quenched obtain to troop-the lath structure by the martensitic transformation zone.These methods comprise casting, thermal treatment and alloy hotwork, and such as forging or rolling, finishing under controlled temperature subsequently realizes best grain refining.The controlled rolling various effects of playing comprise helping the alloying element diffusion, form uniform austenite crystalline phase and store strain energy in the crystal grain.In the quenching step of this method, the controlled rolling martensitic phase that makes new formation be transformed into by the residual austenite divided thin film every the trooping of martensite lath-lath arrange.Rolling economy has nothing in common with each other, and this it will be apparent to those skilled in the art that.Preferably quench as early as possible, avoid forming deleterious microtexture, comprise perlite, bainite and particle or precipitation, particularly INTERPHASE CARBIDE PRECIPITATION and form particle, comprise forming disadvantageous carbide and carbonitride.Trooping-the lath martensite-austenite grains in, the residual austenite film accounts for about 0.5 to 15 volume % of microtexture, and is preferably about 3 to 10%, most preferably is that maximum is no more than about 5%.
Comprise two kinds of crystal grain in the microtexture of triple-phase alloys, be fused together the ferrite crystal grain that forms continuum and troop-lath martensite/austenite crystal grain.In two phase alloys, the particle diameter of single crystal grain is also non-key, can in very large range change.In order to obtain best result, crystal grain diameter common (or the linear dimensions of other appropriate features) is in about 2 to 100 microns scope, and is perhaps preferred in about 5 to 30 microns scope.Ferritic phase quantity with respect to martensite-austenite phase has nothing in common with each other.But in most of the cases, about 5 to 95% time when martensite/austenite grains constitute three-phase structure preferably about 15 to 60%, most preferably can obtain best result at about 20 to 40% o'clock, and these per-cents all are weight percents.
During the preparation triple-phase alloys, the appropriate component that at first will need is mixed, and forms the alloy that requires composition, carries out soaking then, obtains the even austenitic structure that all elements and component all are in the sosoloid form, described in above preparation two phase alloys.Preferred soaking temperature scope is about 900 to 1170 ℃.Form austenite mutually after, alloy composite is cooled to temperature in the ceitical region, the ceitical region is meant the zone of austenite and ferrite phases coexist at equilibrium.Cooling makes the part austenitic transformation become ferrite crystal grain, and remainder is an austenite.During balance in the two-phase relative quantity of each phase along with the temperature variation of this stage cooling compositions, also along with the content of alloying element.The distribution of carbon (when also being balance) is also along with this temperature variation between the two-phase.The biphase relative quantity is not a key factor to the present invention, has nothing in common with each other.The temperature of cooling compositions is preferably in about 800 to 1000 ℃ scope in order to obtain two-phase ferritic-austenitic structure.
After formation ferrite and the austenite matrix (that is, when under selected temperature, in critical phase, reaching balance), the alloy cooling is quenched by the martensitic transformation zone rapidly, austenite matrix is transformed into troops-the lath martensite/austenite microstructure.Used rate of cooling is high enough to avoid ferritic phase to change basically during transformation, and avoids disadvantageous austenite decomposing phenomenon.According to alloy composition and hardenability energy thereof, may need to carry out water-cooled, obtain the rate of cooling of requirement, but some alloy uses air cooling just much of that.In some alloy, particularly contain the triple-phase alloys of 6%Cr, the rate of cooling of requirement is very low, uses air cooling just much of that.The above-mentioned Consideration relevant with the two-phase alloy also can be used for triple-phase alloys.
Contain about carbon of 0.04 to 0.12%, 0 to about 11.0% chromium, 0 to about 2.0% manganese and 0 to about 2.0% silicon in the preferred two-phase alloy composite, these per-cents all are weight percents, and remainder is an iron.Contain about carbon of 0.02 to 0.14%, 0 to about 3.0% silicon, 0 to about 1.5% manganese and 0 to about 1.5% aluminium in the preferred triple-phase alloy compositions, these per-cents all are weight percents, and remainder is an iron.
In microtexture, form precipitation during cooling or other small-particles are collectively referred to as " tempering automatically ".In some application of the present invention,,, can avoid automatic tempering consciously by using rate of cooling faster no matter be two-phase or triple-phase alloys.From the transformation-temperature-time diagram of alloy as can be known, can avoid the minimum rate of cooling of automatic tempered is clearly.In typical figure, the Z-axis representation temperature, transverse axis is represented the time, and the curve among the figure is represented each phase Individual existence or is mixed the zone of existence mutually with other.Typical figure is as shown in the United States Patent (USP) 6273968B1 of above-mentioned reference Thomas.In these figure, minimum rate of cooling is a temperature to the decline straight line of time, links to each other with the left side of C sigmoid curve.There is carbide in the Regional Representative on the curve right side, and the straight line representative that therefore remains on the curve left side avoids forming the rate of cooling of carbide.Therefore have minimum slope with the straight line of contact of a curve, can use the slow rate that to avoid forming carbide.
Here use term " interphase precipitation " and " interphase precipitates " to be illustrated in martensite and austenite intermediate formation primary alloy particle mutually, promptly at lath with separate between the film of lath." interphase precipitates " is not to refer to austenite film itself.Interphase precipitates is different from " throw out mutually ", and the latter is precipitated in the martensite lath, rather than along the interphase precipitate between martensite lath and the austenite film.Diameter is that about 500 dusts or following interior mutually throw out do not have disadvantageous effect to toughness, in fact may add obdurability.Therefore, tempering might not be deleterious automatically, as long as automatic tempering is limited in interior mutually precipitating action and does not cause interphase precipitation.Here use term " to be substantially free of carbide " if there is carbide in expression, then its distribution and quantity are negligible to the effect that performance characteristic produces, and particularly finish the corrosion characteristics of alloy.
According to alloy composition, be high enough to prevent to form carbide or automatic tempered rate of cooling take place by the air cooling realization or need carry out water-cooled usually.Can use air cooling to avoid in the automatic tempered alloy composite, when the content of some alloying element reduces because other alloying element contents raise, still can carry out air cooling.Such as, carbon, chromium or silicone content reduce the rising that can compensate manganese content.
Process of listing in the above-mentioned references to U.S. patent and condition, particularly thermal treatment, grain refining, online forging and use milling train form circle, flat or other shapes, may be used in the enforcement of the present invention, the heating alloy composite is to the austenite phase, triple-phase alloys is cooled to critical phase mutually from austenite, and cooling is by the martensitic transformation zone then.Preferably in austenitizing and fs process of cooling, carry out the rolling of one or more stages in a controlled manner, such as, help alloying element to diffuse to form uniform austenite crystalline phase, make the strain energy in crystal grain distortion and the storage crystal grain then, in the subordinate phase process of cooling, the rolling martensitic phase that can make new formation be transformed into by the residual austenite divided thin film every the trooping of martensite lath-lath arrange.Rolling economy has nothing in common with each other, and this it will be apparent to those skilled in the art that.Trooping-lath martensite-austenite matrix in, the residual austenite film accounts for about 0.5 to 15 volume % of microtexture, and is preferably about 3 to 10%, most preferably is that maximum is no more than about 5%.The ratio that austenite accounts for the whole three-phase microtexture is that maximum is no more than 5%.The developed width of single residual austenite film preferably in the scope of about 50 to 250 dusts, preferably about 100 dusts.The ratio that austenite accounts for the whole three-phase microtexture normally maximum is no more than about 5%.Form the cold working of carrying out after the trooping of two-phase or part three-phase structure-lath martensite/austenite microstructure among the rolling the present invention of being different from who discusses in this section.
Following examples just as an illustration.
Present embodiment explanation has troops-distortion of the carbon steel rod of lath martensite/austenite microstructure, and adopting cold drawing process of the present invention to make area reduction is 99%.
The experiment of present embodiment report is that 6 millimeters, alloy composition are to carry out on 0.1% carbon, 2.0% silicon, 0.5% chromium, 0.5% manganese and the balance ionic rod iron at diameter, all per-cents all are weight percents, the crystal grain of forming microtexture has about 50 microns diameter, each thickness of forming the martensite lath is approximately the crystal grain of 100 nanometers and interlocks with the austenite film that thickness is about 10 nanometers, do not have ferritic phase, each crystal grain all is the austenite shell parcel of about 10 nanometers by thickness.Adopt above-mentioned reference to prepare rod iron in method described in the U.S. Patent application 10/017879 of submission on December 14 calendar year 2001.
Rod iron without coating is carried out cleaning surfaces and lubricated, cold drawn by lubricated dies 15 times under 25 ℃ temperature then, to diameter be 0.0095 inch (0.024 centimetre).The final steel filament diameter is 0.0105 inch (0.027 centimetre), and the expression total area reduction is 99%, and the tensile strength of steel wire is 390 ksi (2690 MPas).
Present embodiment from the explanation of another aspect according to the inventive method troop to having-carbon steel rod of lath martensite/austenite microstructure carries out cold working.In this embodiment, use two kinds of different alloys, Fe/8Cr/0.05C and Fe/2Si/0.1C, the crystal grain of forming microtexture has about 50 microns diameter, each thickness of forming the martensite lath is about the crystal grain of 150 nanometers and interlocks with the austenite film that thickness is about 10 nanometers, do not have tangible ferritic phase, each crystal grain all is the austenite shell parcel of about 10 nanometers by thickness.
The rod iron diameter is 6 millimeters, through cleaning surfaces and lubricated, cold drawn by a series of lubricated dies under 25 ℃ temperature then.The Fe/8Cr/0.05C alloy is used the drawing process shown in the table 1, the Fe/2Si/0.1C alloy is used similar drawing process.In this table, A
0The expression initial rod diameter, A is the excellent diameter after the specific times.
Table 1
Drawing process with the Fe/8Cr/0.05C that does not contain ferritic trooping-lath martensitic microstructure substantially
| Number of times | Diameter (millimeter) | True overall strain (ln (A/A 0)) | Single area reduction (%) | Total area reduction (%) |
| (initially) | 6.000 | 0.0 | 0.0 | 0.0 |
| 1 | 4.3 | 0.7 | 48.2 | 48.2 |
| 2 | 3.4 | 1.1 | 37.0 | 67.3 |
| 3 | 2.7 | 1.6 | 37.1 | 79.4 |
| 4 | 2.2 | 2.0 | 34.0 | 86.4 |
| 5 | 1.8 | 2.5 | 36.6 | 91.4 |
| 6 | 1.4 | 2.9 | 38.5 | 94.7 |
| 7 | 1.0 | 3.5 | 45.4 | 97.1 |
Measure tensile strength in initial rod with after drawing at every turn, the result is mapped in accompanying drawing 1 to true overall strain, square data representation Fe/8Cr/0.05C alloy wherein, rhombus data representation Fe/2Si/0.1C alloy.The tensile strength that accompanying drawing is represented two kinds of alloys is at the end of whole stretching order, is all to reach about 2000 MPas at 97% o'clock in total area reduction.
The cold working that the present embodiment explanation is carried out according to the inventive method, use has troops-carbon steel rod of lath martensite/austenite microstructure, wherein contain ferrite crystal as third phase (except martensite lath and austenite film, i.e. three-phase microtexture).
In this embodiment, alloy is Fe/2Si/0.1C, comprises in its microtexture with described in the foregoing description 1 and 2 similarly trooping-lath crystal grain fused ferrite, contains with the staggered martensite lath of austenite film and is wrapped in the austenite shell.Prepare rod iron according to above-mentioned reference in method described in the U.S. Patent application 10/017847 of submission on December 14 calendar year 2001, used reheat temperature is 950 ℃, makes ferrite content reach 70 volume % of microtexture.Initial rod diameter is 0.220 inch (5.59 millimeters), and cold working is included under 25 ℃ the temperature, draws rod iron by lubricated conical dies 15 times, and each economy approximately is 36%, and final diameter is 0.037 inch (0.94 millimeter).
Drawing process as shown in Table II, A
0The expression initial rod diameter, A is the excellent diameter after the specific times.
Table II
Drawing process with Fe/2Cr/0.1C of three-phase microtexture
| Number of times | Diameter (millimeter) | True overall strain (ln (A/A 0)) | Single area reduction (%) | Total area reduction (%) |
| (initially) | 6.050 | 0.00 | 0.00 | 0.00 |
| 1 | 4.580 | 0.56 | 42.69 | 42.69 |
| 2 | 3.650 | 1.01 | 36.49 | 63.60 |
| 3 | 2.910 | 1.46 | 36.44 | 76.86 |
| 4 | 2.320 | 1.92 | 36.44 | 85.29 |
| 5 | 1.870 | 2.35 | 35.03 | 90.45 |
| 6 | 1.660 | 2.59 | 21.20 | 92.47 |
| 7 | 1.320 | 3.04 | 36.77 | 95.24 |
| 8 | 1.090 | 3.43 | 31.81 | 96.75 |
| 9 | 0.910 | 3.79 | 30.30 | 97.74 |
| 10 | 0.756 | 4.16 | 30.98 | 98.44 |
| 11 | 0.624 | 4.54 | 31.87 | 98.94 |
| 12 | 0.526 | 4.89 | 28.94 | 99.24 |
| 13 | 0.437 | 5.26 | 30.98 | 99.48 |
| 14 | 0.390 | 5.48 | 20.35 | 99.58 |
| 15 | 0.359 | 5.65 | 15.27 | 99.65 |
The tensile strength of final steel wire is 2760 MPas (400 ksi).
Present embodiment further specify according to method of the present invention troop to comprising in the microtexture-lath martensite/austenite and ferrite crystalline carbon steel rod carry out cold working.
In the present embodiment, alloy is the Fe/2Si/0.1C among the embodiment 3, comprise in its microtexture being similar to described in above embodiment 1 and 2 and trooping-lath crystal grain fused ferrite, contain with the staggered martensite lath of austenite film and by austenite shell and wrap up.The rod iron of this composition is to prepare in the general method described in the U.S. Patent application 10/017847 of submission on December 14 calendar year 2001 according to above-mentioned reference.In this case, at first rod iron is rolled into 0.25 inch (6.35 millimeters) diameter, be heated to 1150 ℃ then and continue about 30 minutes, make the composition austenitizing, then at the cryosel quenching-in water, make austenitic transformation become basic 100% martensite, heating once more rapidly makes structural transformation become about 70% ferrite and 30% austenite.Rod iron is quenched, make austenitic transformation become to troop-lath martensite/austenite structure.Cold drawn then rod iron 7 times, each economy are 35%, to the final diameter of 0.055 inch (1.40 millimeters), produce the tensile strength of 1875 MPas (272 ksi).In parallel laboratory test, rod iron is formed identical, and treatment process is identical, and cold drawn 13 times, each economy is 35%, to the final diameter of 0.015 inch (0.37 millimeter), produces the tensile strength of 2480 MPas (360 ksi).
Present embodiment further specify according to method of the present invention troop to comprising in the microtexture-lath martensite/austenite and ferrite crystalline carbon steel rod carry out cold working, proved to change to troop-effect of lath martensite/austenite and ferrite relative quantity.
Steel Alloy is the Fe/2Si/0.1C of embodiment 3 and 4, described in embodiment 4, prepare rod iron, use different reheat temperature, make ferrite content be respectively 0%, 56%, 66% and 75%, the content of respective cluster-lath martensite/austenite is respectively 100%, 44%, 35% and 25%, and all per-cents all are volume percent.These four kinds of microtextures are adopted the similar drawing process shown in the Table II, the tensile strength that obtains is mapped as shown in accompanying drawing 2 to true overall strain, wherein square data representation 100% troops-the lath alloy, trooping-the lath alloy of trilateral data representation 44%, circular data is represented 34% troop-the lath alloy, the trooping-the lath alloy of rhombus data representation 25%.The figure shows the extraordinary tensile strength that all four kinds of microtextures all obtain to surpass 2000 MPas, when troop-when the lath martensite/austenite partly surpasses 25%, can produce than troop-lath partly accounts for 25% the higher tensile strength of microtexture.
Foregoing mainly is for illustration purpose.Can under the situation that still embodies fundamental sum novel concepts of the present invention, make further improvement and variation to each parameter of alloy composition and the course of processing and condition.These improvement and variation will be apparent to those skilled in the art, and belong in the scope of the present invention.
Claims (19)
1. method of making high strength, high ductibility alloy carbon steel, described method comprises:
(a) form have comprise with the carbon steel alloy of the microtexture of the staggered martensite lath of residual austenite film and
(b) carbon steel alloy is cold working to such reduction: it is enough to obtain is the tensile strength of 150 ksi at least, does not wherein carry out intermediate heat treatment.
2. the method for claim 1, it is characterized in that described step (b) comprises carbon steel alloy is cold working to such reduction: it is enough to obtain the tensile strength of 150 to 500 ksi.
3. the method for claim 1, it is characterized in that described step (b) comprises carbon steel alloy is cold working to: each sectional area economy is 20% at least.
4. the method for claim 1, it is characterized in that described step (b) comprises Steel Alloy is cold working to: each sectional area economy is 25% at least.
5. the method for claim 1, it is characterized in that described step (b) comprises carbon steel alloy is cold working to: each sectional area economy is 25 to 50%.
6. the method for claim 1, it is characterized in that step (b) comprises carries out a series of cold working with carbon steel alloy, does not have thermal treatment between each cold working.
7. the method for claim 1 is characterized in that step (b) carries out 100 ℃ or lower temperature.
8. the method for claim 1 is characterized in that step (b) carries out under 25 ℃ envrionment temperature.
9. the method for claim 1 is characterized in that carbon steel alloy is bar or wire rod, and step (b) comprises draws carbon steel alloy through a drawing-die.
10. the method for claim 1 is characterized in that carbon steel alloy is a sheet material, and step (b) comprises rolling carbon steel alloy.
11. the method for claim 1 is characterized in that step (a) comprises
(i) form the carbon steel alloy composition that martensite begins at least 300 ℃ of transition temperatures,
(ii) heat carbon steel alloy composition to sufficiently high temperature, make its austenitizing, form all alloying elements and all be the sosoloid form even austenite phase and
(iii) cool off described even austenite mutually by the territory, martensite range, its rate of cooling is enough fast, and making does not have carbide to be formed between martensite lath and the residual austenite film at the interface substantially in the microtexture of acquisition.
12. method as claimed in claim 11 is characterized in that carbon steel alloy composition has at least 350 ℃ martensite and begins transition temperature.
13. method as claimed in claim 11 is characterized in that the residual austenite film is evenly to be orientated.
14. method as claimed in claim 11, it is characterized in that carbon steel alloy composition is made up of iron and alloying element, this alloying element comprises 0.04 to 0.12% carbon, 0 to 11% chromium, 0 to 2.0% manganese and 0 to 2.0% silicon, and all per-cents all are weight percents.
15. method as claimed in claim 11 is characterized in that step temperature (ii) is 800 to 1150 ℃.
16. the method for claim 1 is characterized in that step (a) comprises
(i) form the carbon steel alloy composition that martensite begins at least 300 ℃ of transition temperatures,
(ii) heat described carbon steel alloy composition to sufficiently high temperature, make its austenitizing, forming all alloying elements all is the even austenite phase of sosoloid form,
(iii) cool off described even austenite phase, make the part austenite be transformed into the ferrite crystal mutually, thus form comprise with the ferrite crystalline two-phase microtexture of austenite matrix consolidation and
(iv) under such condition cooling two-phase microtexture by the martensitic transformation zone: the microtexture that austenite matrix is transformed into contain the martensite lath that interlocks with the residual austenite film.
17. method as claimed in claim 16 is characterized in that step comprises that (iii) the described even austenite to 800 of cooling is to 1000 ℃ temperature.
18. method as claimed in claim 16 is characterized in that step (ii) comprises heating carbon steel alloy composition to 1050 to 1170 ℃ temperature, step comprises that (iii) the described even austenite to 800 of cooling is to 1000 ℃ temperature.
19. method as claimed in claim 16 is characterized in that described carbon steel alloy composition is made up of iron and alloying element, this alloying element comprises 0.02 to 0.14% carbon, 0 to 3.0% silicon, 0 to 1.5% manganese and 0 to 1.5% aluminium, all per-cents all are weight percents.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US42783002P | 2002-11-19 | 2002-11-19 | |
| US60/427,830 | 2002-11-19 | ||
| US10/645,833 | 2003-08-20 |
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| CN (1) | CN100342038C (en) |
| UA (1) | UA80009C2 (en) |
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| CN110366602A (en) * | 2017-02-27 | 2019-10-22 | 纽科尔公司 | Thermal cycle for Austenite Grain Refinement |
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| CN103966417B (en) * | 2013-01-31 | 2016-04-20 | 张家港市骏马钢帘线有限公司 | A kind of processing method improving ultra-fine high-carbon steel wire surface quality and drawing property |
| FR3013737B1 (en) * | 2013-11-22 | 2016-01-01 | Michelin & Cie | HIGH TREFILITY STEEL WIRE COMPRISING A MASS CARBON RATE OF BETWEEN 0.05% INCLUDED AND 0.4% EXCLUDED |
| CN104561830B (en) * | 2015-01-05 | 2017-06-13 | 张建利 | A kind of adjustable austenite martensite two-phase clad steel of thermal coefficient of expansion and preparation method thereof |
| CN110964892B (en) * | 2018-09-27 | 2022-02-15 | 西门子股份公司 | Method for balancing strength and ductility of metal material |
| CN115074637B (en) * | 2022-06-25 | 2023-04-28 | 上海交通大学 | Ultra-high-strength high-toughness ultra-fine tissue low-carbon low-alloy steel and preparation method thereof |
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| US4170499A (en) * | 1977-08-24 | 1979-10-09 | The Regents Of The University Of California | Method of making high strength, tough alloy steel |
| US4613385A (en) * | 1984-08-06 | 1986-09-23 | Regents Of The University Of California | High strength, low carbon, dual phase steel rods and wires and process for making same |
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2003
- 2003-11-18 UA UAA200505981A patent/UA80009C2/en unknown
- 2003-11-18 CN CNB2003801033553A patent/CN100342038C/en not_active Expired - Fee Related
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2005
- 2005-04-15 ZA ZA200503080A patent/ZA200503080B/en unknown
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| US4170497A (en) * | 1977-08-24 | 1979-10-09 | The Regents Of The University Of California | High strength, tough alloy steel |
| US4170499A (en) * | 1977-08-24 | 1979-10-09 | The Regents Of The University Of California | Method of making high strength, tough alloy steel |
| US4613385A (en) * | 1984-08-06 | 1986-09-23 | Regents Of The University Of California | High strength, low carbon, dual phase steel rods and wires and process for making same |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110366602A (en) * | 2017-02-27 | 2019-10-22 | 纽科尔公司 | Thermal cycle for Austenite Grain Refinement |
| CN110366602B (en) * | 2017-02-27 | 2022-10-11 | 纽科尔公司 | Thermal cycling for austenite grain refinement |
Also Published As
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| CN1711363A (en) | 2005-12-21 |
| ZA200503080B (en) | 2006-08-30 |
| UA80009C2 (en) | 2007-08-10 |
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