CN1128051A - Strain-induced transformation to ultrafine microstructure in steel - Google Patents

Abstract

Steel with ultrafine grains is produced by altering the transformation from one which normally proceeds with grain boundary nucleation followed by intragranular nucleation at deformation bands and other defects, to one which induces a substantially instantaneous transformation homogeneously over the austenite grain. This is favoured by a reduction or minimisation of grain boundary nucleation, (for example by enlargement of the austenite grain size), prior to or during the transformation. In an embodiment, a partially cooled austenite phase steel is deformed in a single pass at a temperature in the range of 700-950 DEG C to obtain ferrite grain size of 5 mu m or less.

Description

Strain-induced transformation to ultrafine microstructure in the steel

The present invention relates to steel production and processing to obtain ultra-fine microstructure.For example, in containing ferritic a kind of steel, hyperfine microstructure is meant the size of occupying very big ratio in general carbon steel less than 5 microns grain structure, or in microalloyed steel size less than 3 microns the grain structure that occupies very big ratio.

One of main purpose of modern steel working method is the refinement ferrite crystal grain.Require little ferrite grain size, can improve the intensity and the toughness of steel.

In recent years, the existing many pieces of reports of different technologies that in scientific literature, have the low-carbon microalloyed steel of ultra-fine ferrite crystal grain about production.One class methods are that imagination is producing tiny crystal grain to the temperature of ferrite transformation temperature spot (Ar3) by dynamic recrystallization a little more than austenite.Utilization is reversed to experimentize with compression testing and is simulated, and exploring the dynamic recrystallization after the deformation accumulation, thereby designs the controlled rolling system.

Obtain the production method that grain-size is reduced to 1 to 4 micron austenite crystal in Nb-V microalloyed steel that Kaspa etc. had once reported in compression testing, the ferritic average grain size that this microalloyed steel is transformed in process of cooling is less than 5 microns (" Thermec 88 " Proc.Iht.Conf.on Physical Metallurgy ofThermomechanical Processing of Steels and Other Metals, I.S.I.J.1988,2,713).Utilize the multi-pass accumulation strain to cause the such deformation technique of dynamic recrystallization, reports such as Samuel carry out twisting test to Nb-microalloying steel, have produced grain-size and have been respectively 5 and 3.7 microns austenite and ferrite (I.S.I.J.Int., 1990,30,216).

The United States Patent (USP) 4466842 of Yada etc. has been described a kind of hot rolled ferrite steel, and this steel is by 70% or more be of a size of 4 μ m or axle ultra-fine ferrite crystal grain such as littler is formed.This steel is to make carrying out hot-work near the Ar3 point, makes its minimum draft reach 75% at least by one or multi-channel hot rolling.The hot-work meeting causes austenitic dynamic phase trasnsition and/or ferritic dynamic recrystallization.

To plain carbon stool, Malsumura (I.S.I.J.1987,27,492 and " Thermec88 " I.S.I.J.1988,1,200 and Yada) discloses with laboratory compression and 3 microns ferritic hot-work schemes of following grain-size of rolling test production.Generation (although deformation heat can elevate the temperature) impose big strain meeting induced transformation in deformation process a little more than the above temperature of Ar3 point makes ferrite carry out sufficient dynamic recrystallization then.Rapid quenching can prevent the alligatoring of ferrite crystal grain after the deformation, also can cause martensitic formation.Apply dependent variable and reach at 4 o'clock, can make in the tissue 70～80% ferrite grain size refine to 1～2 micron.Reduce the critical zone dependent variable ferrite volume fraction is reduced, and average grain size increases.

Other technology of producing superfine crystal particle has also been studied a lot.Ameyama etc. (" Thermec 88 ", I.S.I.J.1988,2,848) a kind of low temperature deformation and short period of time austenitizing circulation means are disclosed, austenite nucleation rate when adding 3%Mn and 1%Mo with the enhancing reheat in the steel, this method can make the austenite crystal diameter drop to 1 micron.Kurzydlowski etc. (Z.Metallkande, 1989,80,469) also disclose a kind of repeatedly cold deformation and anneal cycles and have produced the austenitic stainless steel of crystal grain diameter to 1 micron with the method that boron is handled.Although it is these methods all have strict science, then too expensive for producing ultra-fine grain steel.

Recently, (Material Forum such as Beynon, 1992,16,37) reported the hot torsional test method in a kind of laboratory, can produce ultra-fine Nb alloying ferritic steel, its average grain size almost reaches 1 micron, test is adopted in about 1050 ℃ of control thermal distortions, carries out six to eight finishing distortion and cooling fast since 900 ℃ then.Each distortion makes dependent variable reach 0.3 with the coaxial strain rate that is equal to 2.3/s, and last texturing temperature is near the Ar3 point, and can observe maximum degree of grain refinement this moment.The best structure of producing is made up of the perlite of uniform axle ferritic structure such as tiny and 5%, and the ferrite average grain size is 1.3 microns.Can think that this grain refining is to cause the generation of strain-induced transformation to cause owing to the original austenite tissue having been carried out controlled rolling significantly, in this process, distortion has strengthened the forming core particle density of austenite to ferritic transformation.Report in Matsumura that the mechanism of this ferrite crystal grain refinement is listed in front and the Yada document.Priestner (" Thermomechanical Processing ofMicroalloyed Austenite ", Met.Soc.A.I.M.E., 1981,455) also once obtained close grain in the rolling sample in some laboratories, its phase transformation occurs in the operation of rolling between roll gap.And need bigger dependent variable, but its phase-change product mixes very large crystal grain is arranged.Beynon etc. have science equally with the technology that Priestner is reported, but lack practicality.

Primary and foremost purpose of the present invention provides a kind ofly can produce the actual process with super fine organization steel, and tissue comprises various phases or mixed phase in the steel, also comprises the tissue as bainite.

Second purpose of the present invention provides the actual process that a kind of production has the ultra-fine ferrite organization steel.

The 3rd purpose of the present invention provides a kind of steel with super fine organization, particularly a kind of steel of ultra-fine ferrite tissue.

The 4th purpose of the present invention provides the device that is used to produce the ultra-fine ferrite organization steel.

The present invention comes from the discovery of once making us frightened: a kind of steel with very big austenite crystal as greater than 80 microns, after once being out of shape, can obtain ultra-fine ferrite crystal grain after the phase transformation.This and the preceding austenite crystal of the phase transformation that it is generally acknowledged must the very little ferritic viewpoint that could obtain less grain-size after phase transformation be made a world of difference.But the present invention comes from this section particular content perception of this discovery, but recognized further thus by changing the phase mode and can obtain ultra-fine ferrite crystal grain, general phase transformation mode is by normal crystal boundary forming core, intracrystalline forming core at deformation bands or other fault location carries out then, utilized another kind of phase transformation mode among the present invention, promptly in whole austenite crystal, bring out one almost be instantaneous finish to ferritic even transformation.Will help this phase transformation mode if reduce the forming core of ferrite crystal boundary before phase transformation or in the phase transition process.Increasing austenite grain size is a kind of minimizing crystal boundary forming core method, because can reduce crystal boundary like this, but also can use other method.

Also recognize, when a local refrigerative austenitic state steel carries out single pass when distortion in 700～950 ℃ of intervals, to ferritic transformation do not resemble it is generally acknowledged before distortion, take place, but take place immediately in deformation process or after just being out of shape.

Also recognize, make in the steel grain-size become big, and under the austenitizing state,, can obtain ultra-fine ferrite crystal grain by austenite to ferritic transformation then local cooling of steel and distortion by austenitizing.This is that traditional viewpoint is not allowed, and causes AUSTENITE GRAIN COARSENING can cause changing in the process of cooling thickization of back ferrite crystal grain because it is generally acknowledged the reheat of steel.

Find that further the present invention is not limited to the production of ultra-fine ferrite tissue, but can produce the super fine organization of various phases or mixed phase, comprises the tissue that bainite is such.

Correspondingly the invention provides, first, a kind of production method with one or more ultra-fine microstructures zone steel comprises before the phase transformation processing to austenitizing state steel, and this processing will induce one or more microstructures zone that transformation to super fine organization takes place fast substantially completely.

Second, the present invention includes a kind of production method that has super fine organization steel in one or more zones, the austenitizing that comprises steel, austenitizing state steel pre-cooled, to the processing of steel, this processing will induce one or more microstructures zone that transformation to super fine organization takes place fast substantially completely before the phase transformation.

Pre-cooled preferential employing natural air cooling, forced air-cooling or the water-cooled of austenitizing state steel, rate of cooling is between 50～2000K/min.

The 3rd, the present invention comprises a kind of production method that has super fine organization steel in one or more zones, comprise local pre-cooled to the austenitizing state steel that just cast out, to the processing of steel, this processing will induce one or more microstructures zone that transformation to super fine organization takes place fast substantially completely before the phase transformation.

Term used herein " austenitizing state steel " is meant the steel that is the austenite phase time.Should know, in some steel,, before entering austenitic state, have some other and form mutually as the steel that has just cast out.

To the processing of austenitizing state steel,, in the time of preferred 700 ℃-950 ℃ soft steel is out of shape preferably at 600～950 ℃.

The 4th, the present invention comprises a kind of production method that has super fine organization steel in one or more zones, before being included in phase transformation austenitizing state steel is out of shape, in the tissue of steel, form a strain face or a strain gradient in advance with this, can induce one or more microstructures zone that transformation to super fine organization takes place fast substantially completely like this.

Ultra-fine microstructure district preferably comprises a complete transverse section of this tissue, preferably a uniform super fine organization district.Its another embodiment is that ultra-fine microstructure zone should comprise one or more upper layers of steel.Be to reach back one purpose, strain face is included in one or more upper layers of steel quite high strain is arranged in advance in a fourth aspect of the present invention, and the center, its dependent variable is very low.Transformation to ultra-fine microstructure takes place in one or more upper layers then.This nonhomogeneous strain can be strengthened by the Frotteurism that is rolled between steel surface (as steel strip surface) and the roller surface.In addition, in fourth aspect, be rolled coefficient of friction between steel and the roller surface, can in steel, obtain a complete transverse section tissue and be transformed into ultra-fine microstructure, preferably basic super fine organization uniformly by adjustment.

Term " strain face " preferentially refers to an Effective strain face herein, and Effective strain comprises shear strain and compressive strain, and the former causes owing to steel band and contacting of roller, the latter then only with thickness reduce relevant.

The distortion of mentioning in the others of invention that austenitizing state steel is applied preferentially refers to be out of shape rolling.Rolling speed is preferably between 0.1～5.0m/s.For producing better strain face, (ratio of (Ld) and roll gap or rolling thickness (Hm) is more preferably greater than 10 for rolling lonely degree.

Term used herein " fast substantially completely change " refers to that 90% the transformation to final super fine organization occurs in the distorted area or in a second to be finished in the deviation.If phase-change product is a ferrite, being understood to ferritic transformation is a transformation substantially completely rapidly, otherwise the time is long again, and ((cementite) will form carbide.If phase-change product is bainite, whole phase transformation meeting occur in the distorted area or 1 second deviation in.

Indication distortion of first, second, third and fourth aspect of the present invention preferentially comprises, preferably includes only steel rollingly in a pair of reverse rotation roller, and this roller can make steel depress 20～70% at thickness direction, preferably 30～60%, until the value that roll gap load is limited.Preferably only adopt once distortion,, with regard to roller, comprise the orphan that contacts of steel and roll in the above-mentioned distorted area, finish at the roll gap place as in a pair of reverse rotation roller, carrying out one-pass roller.The geometrical dimension of roller, as the draft relevant with thickness of steel product, or roller diameter, should select it more favourable to said transformation substantially completely fast.Can further be rolled processing before and after changing, but before the distortion, Ovshinsky state steel does not preferably have processed mistake, or only be subjected to slight processing.

Preferably make almost changing uniformly of deformation inductdion to super fine organization.Change best major part and in deformation process, take place, although some transformation may the distortion after soon the generation.Being preferably in the distortion back to the transformation of super fine organization finished in one second.This transformation is called as " strain-induced transformation ".

Consistent with a second aspect of the present invention, steel should be heated between 1000～1400 ℃, are preferably between 1100～1300 ℃.

In aspect first, second, third and fourth, steel are preferably in the phase transformation postcooling.

Super fine organization comprises, for example, mainly is ultra-fine ferrite crystal grain, more for example, also may be bainite structure.

The average grain size of austenitizing state steel is more preferably greater than 50 microns, and is better greater than 80 microns.And its austenite grain size is 40 microns in traditional hot-strip before phase transformation.The austenitizing steel can be equiaxial.

In addition, if or in the austenitizing steel in the not described in the above scope of austenite grain size, available a kind of effective means carries out steel that pre-treatment reduces or eliminate the nucleation rate of ferrite crystal grain at crystal boundary in a large number, thereby just helps said fast transition.This pre-treatment comprises that the average austenite grain size that can make selected steel increases, or replaces the chemical process processing, for example, adds a component (as boron) and weakens the crystal boundary reaction.This pre-treatment preferentially comprises pre-cooled from high temperature to cryogenic steel, for example, is cooled to foregoing temperature range, 600-950 ℃ from 1000-1400 ℃.

The speed of cooling of steel needn't be fast especially after the phase transformation, and this can be determined by forced air-cooling, for example, can make speed of cooling reach 500 ° of K/min, is preferably between 50-2000 ° of K/min, and certainly, the present invention does not get rid of more slow or quicker cooling.If like this it be there is no disadvantageous words.In one embodiment of the present of invention the cooling liqs reverse jetting is arrived roll gap to adjust the grain-size that changes the back steel surface, as ferrite grain size.

The steel that is out of shape is band, plate, thin plate, line or bar preferably, although the present invention also is applicable to other type steel such as blank or slab.The thickness of band, plate, thin plate, line or bar preferentially selects less than 20mm, preferably less than 10mm.Can think the present invention be suitable for substantially the strip of general indication (＜5mm) because in this band, can be with the distribution optimization of super fine organization.

The 5th aspect the invention provides a kind of steel with ultra-fine microstructure, for example has ultra-fine ferrite crystal grain, and these crystal grain are local superfine in one or more zones evenly and at least not only, and in these zones, average grain size is not more than 3 microns.Best, steel heart portion average grain size≤10 microns, upper layer≤2 micron.If quite the ferrite crystal grain tissue of vast scale for example has 30% at least, its ferrite grain size is better during less than 3 microns.The tissue of steel can layering, and for example, its upper layer has super fine organization, and organizing of its central core is comparatively thick.Preferably in this laminated tissue, the size of 80% crystal grain is less than 3 microns in the thin crystal layer.

Texturing temperature is selected according to the requirement of required finished steel.For example, if soft steel, then texturing temperature is just more higher.

Generally in above-mentioned distortion, to be accompanied by the cooling of steel, as a heat conduction path is provided.Adopt on record lubricant and/or force cooling roller just can increase this effect.

Ferritic phase preferably in the Finished Steel just can make the ferrite grain size of portion of organization center be not more than 10 times than upper layer crystal grain particle size so when ferritic transformation.

Ultra-fine microstructure generally is equiaxial, but of course not essential.

Available preheating and local cooling are carried out pre-treatment to increase the crystal grain ratio that changes to ultra-fine microstructure to steel.

Austenitizing state steel is soft steel (C＜0.3%) and low-carbon microalloyed steel preferably.But, during with art breading of the present invention, also can form super fine organization for high any the steel of carbon content.

The 6th aspect the present invention includes a cover casting and an anamorphic attachment for cinemascope, can produce a kind of steel that has ultra-fine microstructure in one or more zones.It comprises the device of cast austenitic state steel, reception and local precooling newly cast out the device of austenitizing state steel, and before a large amount of the transformation to the local refrigerative device of steel, induce one or more microstructures zone that transformation to super fine organization takes place fast substantially completely thus.

Poured apparatus can be a thin slab or band continuous caster, and treatment unit preferentially comprises reduction unit, as the roll of a pair of reverse rotation.

The 7th aspect the present invention includes a cover anamorphic attachment for cinemascope, can produce a kind of steel that has ultra-fine microstructure in one or more zones.It comprises the device that steel is heated to the austenitizing state, the device that austenitizing state steel is carried out local precooling, before a large amount of the transformation austenitizing steel is carried out local refrigerative device, it is quick substantially completely to the transformation of super fine organization to induce one or more microstructures zone to take place thus.

The included content of the present invention will be with case description, and accompanying drawing is illustrated:

Fig. 1 is the small-sized rolling line sketch according to the embodiment of sixth aspect present invention.

Fig. 2 illustrates according to the band reheat of seventh aspect present invention embodiment and rolling line sketch.

Fig. 3 is the single track rolling deformation sketch that uses in the embodiment according to the invention fourth aspect.

Fig. 4 is the cross-section strain face synoptic diagram that passes band among Fig. 3.

The continuous variation of the horizontal part of band microstructure in Fig. 5 explanatory view 3.

Fig. 6 is a light micrograph, shows the scanning electron photomicrograph of the surf zone ultra-fine ferrite crystal grain of steel according to embodiments of the present invention.

Fig. 7 A is the light micrograph of M06 steel strip surface zone ultra-fine ferrite crystal grain.

Fig. 7 B is the light micrograph of the thick ferrite crystal grain in M06 band central zone.

Fig. 7 C is the light micrograph of M06 sample after low temperature is gone into rolling system.

Fig. 8 A is the scanning electron photomicrograph of a M06 band low speed rolling back surface area super fine organization.

Fig. 8 B is the light micrograph of M06 band through high-speed rolling back surface area ferrite crystal grain.

Fig. 9 A is that the M06 band is through the rolling back surface area light micrograph of lubricant.

Fig. 9 B is unlubricated dose of rolling back surface area light micrograph of M06.

Figure 10 A is the scanning electron photomicrograph of M06 through air cooling back surface area distribution of carbides.

Figure 10 B is that M06 is through 650 ℃ of scanning electron photomicrographs that batch the back surface area distribution of carbides.

Figure 11 A is the light micrograph of 0.065C-0.099Mn steel (3373) surf zone ultra-fine ferrite and distribution of carbides.

Figure 11 B is 0.065C-0.99Mn steel (light micrograph of (3373) central zone acicular ferrite.

Figure 12 A is that ((3398) are through the light micrograph of 1250 ℃ of reheat back surface area ultra-fine ferrites for high Si steel.

Figure 12 B ferritic light micrograph that to be high Si steel (3398) compressed through 950 ℃ of reheat back surface areas.

Figure 13 A is Ti microalloyed steel (the microoptic photo of (3403) surf zone ultra-fine ferrite.

Figure 13 B is the light micrograph on thick ferrite in Ti microalloyed steel (3403) central zone and martensite island.

Figure 14 A is Ti-Mo microalloyed steel (3403) surf zone ultra-fine ferrite light micrograph.

Figure 14 B is the light micrograph on Ti-Mo microalloyed steel (3404) central zone acicular ferrite and martensite island.

Figure 15 A is the scanning electron photomicrograph of high Ti steel (33994) surf zone ultra-fine ferrite.

Figure 15 B is the scanning electron photomicrograph on high Ti steel (3394) surf zone acicular ferrite and martensite island.

Figure 16 A is the light micrograph of 0.21C-0.99Mn (3374) surf zone ultra-fine ferrite and carbide segregation.

Figure 16 B is 0.21C-0.999Mn steel (3374) central zone item chain acicular ferrite light micrograph.

Figure 17 A is the light micrograph of 1040 steel surf zone ultra-fine ferrites and carbide.

Figure 17 B is the light micrograph of 1040 steel central zone perlite and proeutectoid ferrite.

Figure 17 C is the scanning electron photomicrograph of 1040 steel air cooling back surface area distribution of carbides.

Figure 17 D is 600 ℃ of scanning electron photomicrographs that batch the back surface area distribution of carbides of 1040 steel.

Figure 18 A is the light micrograph of 0.27C-0.12V steel (3524) air cooling back surface area distribution of carbides.

Figure 18 B is that 0.27C-0.12V steel batches the light micrograph of back surface area distribution of carbides for (93524) 600 ℃.

Figure 19 A is the light micrograph of Ti-(3605) 1250 ℃ of reheat back surface area ultra-fine ferrites of B medium carbon steel.

Figure 19 B is the thick ferritic light micrographs that compressed of Ti-(3605) 950 ℃ of reheat back surface areas of B medium carbon steel.

Figure 20 A is the scanning electron photomicrograph of 1077 eutectoid steel surf zone ultra-fine ferrites.

Figure 20 B is the pearlitic scanning electron photomicrographs in 1077 eutectoid steel central zones.

Figure 21 is the stress-strain curves of soft steel (A06), and demonstrating does not have work hardening.

Figure 22 A is the stress-strain curves of soft steel (1062), demonstrates the very work hardening of high level.

Fig. 1 is the sketch of band casting and rolling line 10, and it comprises the content of inventing the 6th aspect.The hot steel band 11 of austenitizing state, its size vertically get off from band casting machine 12 preferably less than 10mm, directly enter pre-cooler 16.Here, available natural air, forced air-cooling or water-cooled are pre-chilled to steel between 700-950 ℃.The steel band that will still be in the austenitizing state then carries out an one-pass roller on milling train 18, depress 50%, just induces after the steel band strain so fast and spends mutually substantially completely.Steel band 19 after phase transformation is also rolling, this moment, thickness was original half, by a natural air, forced air-cooling or water cooler 20 are cooled to envrionment temperature or selected temperature with it again.Then the superfine crystal particle steel band is focused on reeling machine 22, the surface temperature before and after the deformed region is monitored by pyrometer 24,25 respectively, and this deformed region is limited by the milling train contact arc.

Fig. 2 is the sketch of small-sized rolling line 50, and it comprises invention the 7th aspect content.Steel band 51, its size be preferably less than 10mm, extracts out from reeling machine 52, and by a stove, and horizontal solvent induction furnace 54 for example, steel band are heated to austenite and balance each other more than the temperature and be transformed into austenite in stove.This austenitizing state steel 55 is pre-chilled to 700-950 ℃ at a natural air in forced air-cooling or the water cooler 56.The steel band 55 that is still austenitizing is delivered to milling train 58 once more and is depressed 50% one-pass roller, just induces after the steel band strain fast to change fully basically.Steel band 59 after phase transformation is also rolling, this moment, its thickness was original half, by a natural air, pressure cooling or water cooler 70, it was cooled to envrionment temperature or selected temperature again.Then the superfine crystal particle steel band is focused on reeling machine 72.By pyrometer 74,75 monitorings, this deformed region is that the milling train contact arc limits to surface temperature before and after the deformed region respectively.

Fig. 3 shows the fourth aspect technology that is suitable for carrying out an invention, the transverse section of steel band 100 after the one-pass roller distortion.Roll is 112, and Fig. 3 has also pointed out foregoing parameter L d and Hm.Fig. 4 is a cross-section strain face synoptic diagram, and thickness of strip is by of the present invention.The complex effect of Effective strain finger pressure shrinkage strain and shear strain.Compressive strain is provided by H/h, and wherein H is into roller place thickness of strip, and h is for going out roller place thickness of strip, and shear strain is decided by Frotteurism.Fig. 5 has illustrated the horizontal part 105 of the metal of the vertical section of steel band, puts the continuous variation of passing through deformed region in preset time.Fig. 6 has pointed out a layering microstructure that typically obtains (as upper layer mainly is super fine organization, and heart portion is thicker tissue).As can be seen, the width of layer is and the high strain surf zone the 30, the 31st shown in Fig. 4,5, and is corresponding.

Embodiment 1

Is surface temperature 1250 ℃, and observed its austenite grain size mainly at 100 to 200 microns soft steel steel band (C0.09%, Mn1.47%, Si0.08%, Nb0.027%, Ti0.025%, rest part are the relict element of iron and typical content) to be precooled to surface temperature with natural air cooling be 800 ℃.The chilled steel band that is 2.25mm to thickness is rolled into the steel band that thickness is 1.38mm with 38% the draft thermomechanical rolling that carries out single pass by the roll of a pair of counter-rotating.Steel band is 700 ℃ in the surface temperature of roll outlet.Steel band is chilled to room temperature in air then.

Ferrite grain size changes in less than 1 to 12 micrometer range, and the grain-size that accounts for most of cumulative volume (about 60%) is substantially in less than 1 micron to 3 microns scope.These ultra-fine regional centralized or approach the surface.Observe to find that the nipped steel of roll gap of local refrigerative is local or integrally change, and still is the austenite phase fully.In addition, suppose that phase-change mechanism is a strain-induced transformation, think to occur in or very approach roll roll gap back from austenite to ferritic transformation.Although in natural air cooling,, almost do not observe the sign of the ferrite crystal grain alligatoring that causes thus with the relatively low cooling rate cooling of inherent yet, this means that transformation is instantaneous fully, wherein crystal grain locks mutually in its position its volume can not be expanded.

Embodiment 2

Is surface temperature 1250 ℃, and observed its austenite grain size mainly at 100 to 200 microns soft steel steel band (C0.1%, Mn1.38%, Si1.4%, rest part are the resident element of iron and typical content) to be cooled to surface temperature with natural air cooling be 775 ℃.The pre-cooled steel band that is 2.13mm to thickness carries out the thermomechanical rolling of single pass with 39% draft by the roll gap of the roll of a pair of counter-rotating, is rolled into the steel band that thickness is 1.3mm.Steel band is 688 ℃ in the surface temperature of roll outlet.Steel band is chilled to room temperature in air then.

Ferrite grain size changes in less than 1 and 20 micrometer ranges, and the grain-size that accounts for most of cumulative volume (about 60%) is basically in less than 1 micron to 3 microns scope.These ultra-fine regional centralized or approach the surface.Observe to find that the nipped steel of roll gap of local refrigerative is local or integrally change, and still is the austenite phase fully.In addition, suppose that phase-change mechanism is a strain-induced transformation, think to occur in or very approach rolling roll gap back from austenite to ferritic transformation.Although in natural air cooling,, do not observe any sign of the ferrite crystal grain alligatoring that causes thus with the relatively low cooling rate cooling of inherent yet, this means that transformation is instantaneous fully, wherein crystal grain locks mutually in its position its volume can not be expanded.

Embodiment 3

Just having cast that finish or similar steel is not suitable for experimentizing.Yet a kind of surface temperature is that 1250 ℃ soft steel steel band (C0.07%, Mn0.4%, rest part are the resident element of iron and typical content) can be used for simulating and just casts the steel that finishes.The austenite grain size that this steel has is basically in 100 to 200 micrometer ranges.The steel that finishes is different with just casting, and the austenite crystal tissue is equiaxial in this steel.This steel is chilled to surface temperature in advance with naturally cooling in air be 800 ℃.The chilled steel band that is 1.8mm to thickness carries out the thermomechanical rolling of single pass with 45% draft by the roll gap of the roll of a pair of counter-rotating, is rolled into the steel band that thickness is 1.00mm.Steel band is cooled to 600 ℃ then in air, keep batching to simulate in 1 hour under this temperature, is cooled to room temperature again in air.

Product contains 95% ferrite, and it is distributed in the steel band unevenly.Ferrite grain size changes in 1 to 10 micrometer range, and the grain-size that accounts for most of cumulative volume (about 60%) is basically in 1 to 2 micrometer range.These ultra-fine regional centralized or approach the surface.Observe to find that the nipped steel of roll gap of local refrigerative is local or integrally change, and still is the austenite phase fully.In addition, suppose that phase-change mechanism is a strain-induced transformation, think to occur in or very approach roll roll gap back from austenite to ferritic transformation.Although in natural air cooling,, do not observe the sign of the ferrite crystal grain alligatoring that causes thus with the relatively low cooling rate cooling of inherent yet, this means that transformation is instantaneous fully, wherein crystal grain locks mutually in its position its volume can not be expanded.

Steel band has been carried out Elongation test, found that its yield strength is 460MPa, the maximum tensile strength is 480MPa.Breaking elongation is 28%, and uniform elongation is 20%.

Embodiment 4

Is surface temperature 1250 ℃, and observed its austenite grain size mainly at 100 to 200 microns soft steel steel band (C0.1%, Mn0.86%, Si0.29%, Nb0.037%, rest part are the resident element of iron and typical content) in air naturally cooling to be chilled to surface temperature in advance be 800 ℃.The chilled steel band that is 2.4mm to thickness carries out the thermomechanical rolling of single pass with 40% draft by the roll gap of the roll of a pair of counter-rotating, is rolled into the steel band that thickness is 1.43mm.The surface temperature of steel band in the roll exit is 696 ℃.Steel band is chilled to room temperature in air then.

Ferrite grain size changes in 1 to 12 micrometer range, and the grain-size that accounts for most of cumulative volume (about 60%) is basically in less than 1 to 2 micron scope.These ultra-fine regional centralized or approach the surface.Observe to find that the nipped steel of roll gap of local refrigerative is local or integrally change, and still is the austenite phase fully.In addition, suppose that phase-change mechanism is a strain-induced transformation, think to occur in or very approach roll roll gap back from austenite to ferritic transformation.Although in natural air cooling,, do not observe the sign of the ferrite crystal grain alligatoring that causes thus with the relatively low cooling rate cooling of inherent yet, this means that transformation is instantaneous fully, wherein crystal grain locks mutually in its position its volume can not be expanded.

Further embodiment

No matter be from big production or laboratory melt obtain a large amount of low, in, high carbon steel is rolling on milling train.The carbon content scope of these steel is 0.036 to 0.77%C, and overall composition is by shown in the table 1.Earlier the steel rough forge is become the thick band of 2mm, be cut into wide 100mm again, the piece of long 150mm.Steel band 10 to 15 minutes to 1250 ℃ of reheat in the stainless steel steel bushing, air cooling is to required rolling temperature then.Rolling mode with single pass is carried out, and the diameter of used roll is about 300mm.Sample allows air cooling then, or carries out 1 hour batch simulate in the husky bed of homothermic mobile, then is cooled to room temperature between two Kao Wuer felts 1.Rolling inlet and temperature out with pyrometer record roll both sides.The temperature of rolling entrance and exit sees Table 2.

Various machined parameters have been studied to the microstructural influence of steel band.Except the influence of carbon and other common alloying elements, in some steel, expection is such as Nb, and the existence of Ti and B micro alloying element is also influential to final microstructure.Breaker roll temperature in, draft, roll speed, influence lubricated and charging thickness are also studied.Table 2 has been listed the experiment condition scope to the research of all steel.

Use standard techniques to prepare metallographic sample, and use opticmicroscope and scanning electronic microscope that it is studied by rolling steel band.Measured Vickers' hardness, and prepared tension specimen by some steel bands.Elongation test carries out on the Sintech drawing machine, and rate of extension is 10 ^-4S ^-1

Microstructure

Listed steel is divided into common and soft steel microalloying, medium carbon steel and high carbon steel in the table one.The universals of all rolled sample are appearance of superfine tissue, and these super fine organizations are usually by being positioned near the ferrite crystal grain in sample surfaces zone and isolated carbide particle and forming in the alligatoring microstructure of central section.These super fine organization zones are penetrated into the degree of depth (Fig. 6) of about thickness of sample of 1/4 to 1/3 usually.Indivedual microstructures are described in detail following.

The temperature decline scope of roller mill exit record is at 70 to 180 ℃, and is most of at 70 to 100 ℃.Most of draft is between 30% to 40%.

Ordinary low-carbon steel

Carried out rolling to four kinds of ordinary low-carbon steels: M06, A06,3373 and 3398, its most of experiment condition press M06 and A06 changes.

M06

835,795,775 with 740 ℃ (respectively counter sample M06-1,2 and 3) four different delivery temperatures under the influence of rolling four samples research roll temperature in.Preceding two temperature do not have very big change to microstructure, this microstructure contain a grain-size that penetrates 1/4 thickness of sample be 1-3 μ m etc. the grain-size of axle ferrite central section (Fig. 7 A) and an alligatoring be the axle ferrite central sections (Fig. 7 B) such as wedge angle of 5-15 μ m.The 3rd temperature in may cause the formation of some proeutectoid ferrites at the original austenite crystal boundary near the surface.Yet, as previously mentioned near surface region, ultra-fine ferrite crystal grain is arranged; At the center, the wedge angle tissue of alligatoring is arranged.Minimum delivery temperature produces the microstructure of being made up of a large amount of proeutectoid ferrites (Fig. 7 C) in entire sample.

Relatively four kinds of roll speeds 0.18,0.27,0.37 (standard speed) and 1.0m/s study the influence of roll speed.Because the time that contacts with cold roller is longer, lower roll speed (M06-5 and 6) causes temperature loss bigger in roll gap.This compares generation more proeutectoid ferrite (M06-4) with the rolling speed of standard under similar temperature in (M06-4).When the roll speed of 0.18m/s, produced diverse microstructure.The center of sample and surface all are made up of a kind of ultra-fine bainite class microstructure, and this ultra-fine microstructure has high crystallographic characteristics (Fig. 8 A).The surface batten is more more tiny than those of center.This microstructure has reflected the big temperature loss (losing about 170 ℃) in roll gap.The highest roll speed that obtains is 1.0m/s (M06-16), and this speed causes a kind of laminate structure, although the ferrite crystal grain of surf zone is not superfine (Fig. 8 B).

On roll, use the agent of boron nitride mist lubrication to carry out rolling to five samples.A rolling sample (M06-8) depresses 57% under 790 ℃, and it is by a large amount of proeutectoid ferrites that spreads all over entire sample and a phase composite that shows as ultra-fine bainite, and this is with observed similar in M06-5.Second sample (M06-10) in slightly high temperature so that only 41% draft is rolling.This sample is chilled to the different temperature with sample M06-5 by roll.It is made up of a spot of proeutectoid ferrite, also has relatively thin ultra-fine (1-3 a μ m) ferrite area and thick (5-15 a μ m) wedge angle ferrite center.Sample M06-18 and 19 makes with lubricator rolling under 800 and 775 ℃, produces different slightly tissues once more, and it has even more serious surf zone of temper grade and proeutectoid ferrite still less.These difference may be to be caused by the variation of lubricating thickness.(M06-17) caused near quenching microstructure on lubricated surface and ferritic structure (Fig. 9) in apparent surface's a relative refinement.Compare with unlubricated sample, draft does not almost increase (Fig. 9 B).Two (promptly not in bag reheat) sample of descaling be rolled (M06-21 and 22), cause thick relatively axle ferrite surface microstructure (near 10 μ m) and the thick central section (10-20 μ m) of waiting.Oxide skin is considered to play a part a kind of lubricant, though it has reduced the roll load slightly and has increased total draft, the existence of oxide skin does not produce the structure when being similar on roll splash lubrication agent.Yet oxide skin has played a kind of effect of thermally-insulated body really, makes the temperature drop reduce about 40 ℃.

To the M06 material, the final condition that changes is to batch the influence that steel band brought of rolling (M06-15) in the husky bed that flows.Though the distribution of carbide is changed by coiling process, the surface of sample M06-15 or the grain-size at center significantly do not change (Figure 10 A).In the sample that has batched, in crystal boundary and triple point place carbide ratio bigger (Figure 10 B).

A06

Though the reheat temperature is lowered in some cases, traditional A06 is still rolling under the condition similar to M06.Though it is microstructure is having more variation along thickness and rolling direction, usually still similar to the microstructure of M06 acquisition.

The roll temperature in is pressed sample A06-1,2,3 and 8 and is changed.A06-8 uses 905 ℃ of temperature ins the highest, produces an equiaxed structure preferably, wherein at the crystal grain that 1 to 4 μ m is arranged near the surface, the coarsened grain of the nearly 15 μ m of size is arranged in the central section.855 ℃ of A06-2 delivery temperature produce degree of depth similar to A06-8 wait an axle ferrite area, simultaneously by one by thick, be orientated the center that different wedge angle ferrite crystal grain is formed, its length is usually greater than 20 μ m.Temperature in reduce 50 ℃ (A06-1) though the time some proeutectoid ferrites can appear, but still obtain similar tissue.Though the superfine surface region is still keeping under 755 ℃ of minimum rolling temperatures (A06-5), has produced a large amount of thick proeutectoid ferrites.

As a technique change factor, studied roll speed, observed the trend similar to M06.When low roll speed 0.18m/s (A06-4), though the temperature drop surpasses 100 ℃, and produces a large amount of proeutectoid ferrites, it organizes still similar to sample (A06-1) rolling under uniform temp.Though sample (A06-7) rolling under the moderate speed 0.27m/s is to be rolled, but still cause the microstructure of the alligatoring of entire area under a higher temperature.

To sample A06-5 and 6, reduce reheat temperature to 1050 and ℃ reduce volume fraction significantly at the superfine crystal particle of surface region, increase the rugosity of center crystal grain.Sample (A06-5) rolling under higher temperature in has the ferrite crystal grain district of some grain-sizes less than about 4 μ m, but these zones are isolated, and not directly near the surface.Lower delivery temperature (A06-6) produces ultra-fine ferrite district still less, and in whole microstructure scope, even extend to the surface, very thick wedge angle crystal grain is arranged.Some significantly ferrite crystal grains of temperature processing are also arranged.

3373

The steel of this trade mark (be made up of a upper layer that penetrates (Figure 11 A) ultra-fine ferrite crystal grain (1-2 μ m) of about 1/4 sample degree of depth by the microstructure of 0.065%C-1%Mn), some poly-partially carbide districts are arranged simultaneously, and these carbide seem into multirow and arrange.Center (Figure 11 B) is made up of volume fraction very big stratiform Wei Shi body or acicular ferrite, and having simultaneously significantly may be pearlitic second phase.

3398

The steel of this high Si trade mark provides the understanding of some original austenite grains sizes to final microstructure influence, and the original austenite grains size is mainly determined by the temperature of reheat.High reheat temperature 1250 ℃ (Figure 12 A) produces the tissue that adds heat similarity with 3373, though upper layer is not tiny on the whole, and the center is made up of the blocky ferrite crystal grain that more demonstrates of alligatoring, and some dispersive martensite islands are arranged simultaneously.Carbide appears at the ferrite crystal boundary, and is continuous distribution around a large amount of ferrite crystal grains.Reheat sample to only 950 ℃ (3398-2) produce tangible surface and central section as in the previous, yet (Figure 12 B) formed by the mixture of the ferrite crystal grain of superfine crystal particle or subgrain and big compression in the surface.The center is by waiting axle ferrite (about 5 to 10 μ m), discrete carbide and the martensite island that some are little to form preferably.

The micro-alloying low-carbon steel

The Ti additive

3403 steel (0.024%Ti) produce the equally distributed ultra-fine ferrite crystal grain district (Figure 13 A) of one the 1/4 sample degree of depth and one by wedge angle, some are centers (Figure 13 B) that acicular ferrite crystal grain, dispersive carbide and isolated martensite island are formed.Add in the similar steel (3404) of 0.20%Mo, though upper layer forms by more tiny ferrite crystal grain (＜1-2 μ m) (Figure 14 A), and the ferrite at sample center more tiny with have more needle-like (Figure 14 B), its tissue is similar.There are some little martensite bundles to occur equally again.

The addition of higher Ti is as causing superfine ferrite upper layer (Figure 15 A) and in the ultrafine acicular ferrite structure (Figure 15 B) of central section in welding bar steel (3393 and 3394).Ultra-fine ferrite can not be differentiated with opticmicroscope, yet electron microscope shows that it is a sub-micron grain.Moreover isolated martensite island is scattered here and there in whole acicular ferrite.

The Nb additive

Processed two kinds of traditional steel XF400 and XF500 that not only contain Nb but also contain Ti, produced by the little similar surperficial microstructure of forming to the ferrite crystal grain of about 1 μ m of size, but central tissue's difference slightly.The central section of XF400 sample is made up of the granular ferrite crystal grain of wedge angle, and this ferrite crystal grain is all inconsistent on size and dimension, and size range is about 5 to 15 μ m.Yet the XF500 sample produces more tiny, a slightly more uniform acicular ferrite microstructure.

3370 samples that contain Nb0.037% be used to study increase charging thickness, lubricated and rolling after the influence of batching.Initial thickness is that the standard model (3370-1) of 2mm is made up of the common ultra-fine ferrite that penetrates sample 1/4 degree of depth, and wedge angle and acicular ferrite mixture are arranged at the center simultaneously.When charging thickness increases to 4mm (3370-2 sample), the grain-size of surf zone so not tiny (near about 4 μ m), and penetration depth is so not big yet, may only arrive the degree of depth of 1/5 sample.Temperature drop in the roll gap is just above 50 ℃.3370-3 samples are lubricated, and temperature drop has surpassed 140 ℃, is most likely caused by the heat-conduction effect of lubricant.The grain-size of surface region is similar, but more inhomogeneous, and this regional degree of depth reduces manyly.The microstructure of central zone is similar basically.Sample 3370-4 (thickness 2mm nips) batches at 600 ℃ 750 ℃ of rolling backs, and wherein delivery temperature is lower than first three sample.The degree of depth of ultra-fine surface region is near 1/3 sample thickness, and this may be a penetration depth maximum in all samples.In the grain-size in that district less than 1um.As if the central zone relatively remains unchanged, therefore batch and change indistinctively the microstructure of integral body.

Other additive

Sample 3607 and 3608 all contains Mo and Ti, and wherein 3608 contain 0.002% B.As if the interpolation of B also changes microstructure indistinctively, and two samples all are made up of superfine crystal particle with standard depth and wedge angle ferrite crystal grain at the center.Sample 3608-1 just has a non-ultra-fine district on its surface, this may be because the result of decarburization.3607 steel also batch under 600 ℃ in rolling (3607-2) back, yet it is gone into roll temperature and is lower than 3607-1 sample for 50 ℃.After batching, microstructure does not almost change.

3399 steel contain 0.48%Cr, the zone that produces 1-2um ferrite crystal grain on nearly surface, and acicular ferrite is arranged and with the martensite island of the large volume fraction of acicular ferrite at the steel band center.

Medium carbon steel

The steel of these trades mark contains 0.2 to 0.4% carbon, also contains Ti, V and B in some situation.Normal carbon steel sample 3374 contains 0.21%C, is to be that surf zone of the equiaxed ferritic grain of 1-3 μ m constitutes by grain-size, wherein ferrite crystal grain and tiny carbide that gather to become number to arrange partially accompany (Figure 16 A).There is acicular ferrite to occur at the center, and the item chain ring (Figure 16 B) that around the original austenite crystal boundary, has some to constitute by tiny ferrite crystal grain.Second general carbon steel (1040) processed under three conditions; Just rolling down 750 ° and 700 ℃, then air cooling, rolling down and batch during at 600 ℃ at 750 ℃.All samples have the distinctive ultra-fine microstructure that penetrates 1/3 thickness of sample.In this zone, spread all over distributing very tiny ferrite and the carbide of high-volume fractional (Figure 17 A).Be formed centrally proeutectoid ferrite in the steel band, the draw profile of original austenite crystal boundary of structure, however major part is perlite (Figure 17 B) in this zone.In this case, batch as and if change indistinctively the distribution (Figure 17 C and D) of carbide.

Sample 3521 (adding Ti) all is to process under the condition identical with 1040 steel with 3524 (adding Ti and V).Almost to all conditions, two compositions all have similar microstructure.Though in two samples of this after 600 ℃ are batched, that carbide becomes is more tiny, divided particles more, at surf zone, its microstructure is still formed (comparison diagram 18A and B) by ultra-fine ferrite crystal grain and carbide.In the rolling sample, superfine crystal particle is slightly refinement (3521-3 and 3524-3) also under lower temperature.The central section is made up of the acicular ferrite crystal grain that spreads all over whole pearlite matrix distribution.In containing the sample of V, these acicular structures generally are refinements, and particularly meticulous in sample 3524-3.

Last a kind of medium carbon steel (3605) contains Ti and B.Though according to expectation is such, it has more carbide to occur, and especially at ultra-fine surface region (Figure 19 A), its microstructure is similar to soft steel sample 3607 and 3608 (with Ti, Mo and B alloying).Similar to sample 3398-2; second sample (3605-2) before rolling reheat only to 950 ℃; it is by the ferrite crystal grain of the thick relatively of surf zone and compression, and constitutes (Figure 19 B) in conjunction with the zonule that some tangible carbide and superfine crystal particle or subgrain are formed.The ferrite crystal grain of central section have wait preferably the axle property.This identical materials is reheat to 950 and 1205 ℃ also.Quench and the etch austenite grain boundary.Lower reheat temperature produces the crystal grain of 10-20 μ m, and the grain-size that higher reheat temperature produces is in the scope of 100 to 400 μ m.

High carbon steel

Two kinds of perlitic steels 1062 are all rolling under three conditions identical with processed sample 3521,3524 and 1040 with 1072.The microstructure of these two samples of handling under various different conditions does not almost have difference.Surf zone at these two kinds of steel has shearing again, simultaneously, ultra-fine ferrite crystal grain (size is less than 1um) and discontinuous carbide (Figure 20) is arranged in these zones.Yet the depth ratio of ultra-fine ferrite is observed littler in the soft steel sample, although this may be because lower draft (being generally 20 to 25%) is.The central section is made of the perlite colony, similar (Figure 20) that expects in the high carbon steel of its microstructure and conventional processing.

Mechanical characteristics

The mechanical characteristics of all steel is listed in the table 3.To higher carbon steel, because it does not have definite top and bottom yield point, so measured 0.2% permissible stress.These results' least ordinary aspect is the planeness of many stress-strain curves, especially to lower C content.This is reflected in the LYS/UTS ratio, and its value is near 1.00 under many situations.An example of no work hardening is embodied in the stress-strain curves of sample A06-8 (Figure 21), and wherein maximum stress occurs in upper yield point.After this, stress decrease also remains under the initial level.The steel of higher carbon has work hardening really in a very large scope, especially in 1040, the 1062 and 1077 commercial trades mark., a typical curve (sample 1062-1) as shown in figure 22.

The result shows that this class course of processing has obtained very high intensity.A kind of ordinary low-carbon steel (M06-9) has obtained the yield strength of 590MPa, and 16% breaking elongation, and the unit elongation of A068 is that its twice and yield strength are 430MPa.The third straight carbon steel (3373) that contains 0.065%C also has superior performance: LYS and UTS to be respectively 520 and 580MPa, and breaking elongation is 23%.To lower carbon steel, in two kinds of welding bar steels (3393 and 3394), obtained maximum strength characteristics, its LYS is respectively 745 and 830MPa.In sample 3398 and 3605, reduce the reheat temperature and cause that very big intensity increases, although opposite the influence of extending.Suppose that ultra-fine ferrite microstructure behind the high temperature reheat is transformed into the alligatoring behind the low temperature reheat and the ferritic structure of compression, this result is significant.

The result of rolling under various conditions M06 shows that several processing factors can influence its final properties.Though high rolling temperature produces the best steel band of ductility, roll temperature in (M06-1,2 and 4) also changes the intensity of material indistinctively.As the rolling situation of comparatively high temps (M06-16), batching after rolling makes material softening, and increases unit elongation.The performance that reheat under the low temperature (M06-13) produces is only omited the steel band (M06-14) inferior to reheat under the normal high temperature, although the microstructure that their form is different fully.As from expecting the microstructure, high more a lot of than the sample that removes descaling with the intensity of the sample after the Roller Machining of adding lubricant.Not at all surprising, the softest steel band in all material that the thick relatively microstructure of the sample M06-21 of descaling causes up to now being tested.

The steel of higher carbon demonstrates successive surrender property, therefore tests its permissible stress to replace LYS.These steel demonstrate the bigger work hardening of steel of comparison low-carbon (LC), and produce some very high intensity levels.Although its carbon content is lower, owing to added Ti and V, sample 3524 has obtained than 1040 higher bullet and has limit and tensile strength, and identical ductibility.Though perlitic steel 1062 and 1077 its total unit elongation are lower, intensity is bigger than what obtain under industrial condition (with the bar steel form) usually.In all and in the high carbon steel, batching in the time of 600 ℃ makes PS and UTS all reduce (in 1077 situations, decrease surpasses 100MPa), but to almost not influence of ductibility.Except 3524 heating, the roll temperature in reduces by 50 ℃ makes intensity increase 30MPa at least.

Up to the present, austenite phase steel is transformed into the not understanding fully of cutter reason really of a kind of ultra-fine microstructure.In theory, rely on to reduce the crystal particle crystal boundary area of austenite in mutually, precooling then will make that being transformed into ferritic motivating force becomes very big.Yet for forming forming core, the area of crystal boundary is not enough.Therefore, rely on the even transformation of steel being handled (even steel distortion) meeting generation strain inducing at the austenite phase time with before any extensive transformation takes place to ferritic phase.This even phase transformation takes place very soon, and ferrite grain size is very little.

As described in United States Patent (USP) 4466842, this transformation to tiny ferrite crystal grain is owing to even phase transformation, rather than the ferritic kinetics recrystallize that has transformed.

All technical requirementss and below claim in, unless in addition requirement in the literary composition, " comprising " speech, with and variant, all be understood to include the whole or whole group of being stated, but do not get rid of any other whole or whole group.

Table 1

All are studied the composition INVESTIGATED (weight %) of steel

C P Mn Si S Cr Mo Al Nb Ti V B N ID 3394 0.036 0.017 1.39 0.62 0.012 0.019 0.006 0.013＜0.005 0.12 0.005＜0.0003 0.0056 3607 0.043 0.018 1.67 0.21 0.011 0.008 0.26 0.034 0.022 0.016＜0.003＜0.0003 0.0035 3608 0.044 0.019 1.73 0.22 0.01 0.009 0.26 0.03 0.022 0.017＜0.003 0.0019 0.0035 A06 0.06 0.013 0.21 0.005 0.011 0.017 0.002 0.04 0.0036 3373 0.065 0.018 0.99 0.27 0.006 0.004 0.002 0.03＜0.005＜0.003＜0.003＜0.0003 0.0018 M06 0.075 0.015 0.51 0.26 0.008 0.018 0.002 0.005 0.003 3393 0.08 0.018 1.34 0.63 0.013 0.019 0.007 0.017＜0.005 0.16 0.006 0.0003 0.0077 XF400 0.09 0.015 0.71 0.015 0.005 0.02 0.002 0.03 0.027 0.025 0.0034 3403 0.10 0.017 1.50 0.76 0.011 0.017 0.005 0.026＜0.005 0.024＜0.003 0.0004 0.0047 XF500 0.10 0.018 1.47 0.08 0.005 0.037 0.004 0.03 0.045 0.031 0.004 0.0005 0.0063 3370 0.105 0.005 0.86 0.29 0.005 0.004 0.002 0.019 0.037 0.006＜0.003＜0.0003 0.0041 3398 0.105 0.018 1.38 1.40 0.011 0.017 0.004 0.026＜0.005 0.004＜0.003＜0.0003 0.0038 3399 0.105 0.018 1.38 0.16 0.011 0.48 0.004 0.024＜0.005＜0.003＜0.003＜0.0003 0.0041 3404 0.105 0.017 1.50 0.31 0.012 0.017 0.20 0.022＜0.005 0.022＜0.003＜0.0003 0.0051 3605 0.175 0.019 1.68 0.20 0.013 0.008 0.003 0.038＜0.005 0.017＜0.003 0.0016 0.0043 3374 0.21 0.02 0.99 0.29 0.006 0.003 0.002 0.033＜0.005＜0.003＜0.003＜0.0003 0.0025 3524 0.27 0.005 1.67 0.36 0.034 0.008 0.003 0.036＜0.005 0.014 0.12＜0.0003 0.014 3521 0.29 0.018 0.85 0.21 0.008 0.014 0.009 0.037＜0.005 0.02 0.003 0.0006 0.0023 1040 0.38 0.019 0.76 0.20 0.008 0.022 0.003 0.04＜0.005＜0.002＜0.002＜0.0003 0.004 1062 0.63 0.023 0.75 0.22 0.019 0.04 0.01 0.03 0.003 1077 0.77 0.018 0.71 0.184 0.007 0.01 0.04 0.01 0.004

Table 2

The processing conditions of all steel bands

The reheat roll speed is rolling/and go into roller and go out stagnation pressure sample title after the rolling

The cooling of temperature (m/sec) sample temperature temperature is rate down

( ℃ ) ( ℃ ) ( ℃ ) ( ％ ) M06-1 1250 0.37 835 710 41M06-2 1250 0.37 795 685 35M06-3 1250 0.37 740 675 35M064 1250 0.37 775 685 35M06-5 1250 0.18 775 605 30M06-6 1250 0.27 785 660 35M06-8 1250 0.37 790 630 57M06-9 1250 0.27 800 670 35M06-10 1250 0.37 800 690 41M06-13 950 0.30 775 29M06-15 1250 0.30 790 720 650℃ 29M06-16 1250 1.0 800 715 29M06-17 1250 0.30 1 800 31M06-18 1250 0.30 800 37M06-19 1250 0.30 775＜670 40M06-21 1250 0.30 810 770 31M06-22 1250 0.30 780 745 31A06-1 1250 0.37 800 720 40A06-2 1250 0.37 855 745 45A06-3 1250 0.37 755 685 35A06-4 1250 0.18 810 625 33A06-5 1050 0.37 805 700 35A06-6 1050 0.37 750 650 33A06-7 1250 0.27 900 705 43A06-8 1250 0.37 905 760 453370-1 1250 0.37 800 695 403370-2 1250 0.37 800 745 493370-3 1250 0.37 805 660 543370-4 1250 0.30 750 670 600℃ 443373-1 1250 0.37 800 675 353374-1 1250 0.37 755 690 403393-1 1250 0.37 770 680 403394-1 1250 0.37 800 680 413398-1 1250 0.37 775 690 403398-2 950 0.30 775 635 303399-1 1250 0.37 800 675 373403-1 1250 0.37 810 700 383404-1 1250 0.37 765 650 373605-1 1250 0.37 765 695 413605-2 950 0.30 775 660 313607-1 1250 0 37 795 690 353607-2 1250 0.30 750 660 600℃ 333608-1 1250 0.37 800 715 41XF400-1 1250 0.37 800 700 38XF500-1 1250 0.37 775 675 41

Cont

Table 2 (continuing)

The reheat roll speed is rolling/and go into roller and go out stagnation pressure sample title after the rolling

The cooling of temperature (m/sec) sample temperature temperature is rate down

(℃) condition (℃) (℃) (%) 3521-1 1,250 0.30 730 660 batch 600 ℃ of 303521-2,1,250 0.30 750 660 air 343521-3,1,250 0.30 705 625 air 303524-1,1,250 0.30 750-air 293524-2,1,250 0.30 750-and batch 600 ℃ of 293524-3,1,250 0.30 700-air 291040-1 1,250 0.30 750 615 and batch 600 ℃ of 261040-2,1,250 0.30 750 615 air 261040-3,1,250 0.30 700 600 air 241062-1 1,250 0.30 760 655 and batch 600 ℃ of 261062-2,1,250 0.30 755 640 air 301062-3,1,250 0.30 690 600 air 261077-1 1,250 0.30 735 610 and batch 600 ℃ of 211077-2,1,250 0.30 755 620 air 261077-3,1,250 0.30 700 580 air 21

Table 3

The mechanical property of all steel

(from stress before not losing efficacy be 517 and the sample 3608 of 538MP the sample of extraction)

LYS 0.2%PS UTS LYS/UTS TE (%) sample title

(MPa) (MPa) (MPa) PS/UTS (75mm)3394-1 745 748 1.00 113607-1 495 507 0.98 173607-2 446 494 0.90 19A06-8 432 432 1.00 323373-1 520 580 0.90 23M06-1 490 507 0.97 25M06-2 471 497 0.95 13M064 502 520 0.97 19M06-9 589 589 1.00 16M06-10 540 552 0.98 17M06-11 481 523 0.92 22M06-13 481 538 0.89 14M06-15 435 472 0.92 22M06-16 428 490 0.87 23M06-18 566 607 0.93 14M06-21 306 360 0.85 163393-1 830 874 0.95 16XF400-1 576 576 1.00 113403-1 535 609 0.88 26XF500-1 670 672 1.00 113370-1 603 617 0.98 1733704 633 633 1.00 83398-1 580 634 0.91 203398-2 662 720 0.92 113399-1 520 605 0.86 223404-1 530 695 0.76 203605-1 490 499 0.98 233605-2 521 557 0.94 133374-1 500 505 0.99 263524-1 742 873 0.85 173524-2 696 792 0.88 143524-3 745 840 0.89 123521-1 545 607 0.90 183521-2 581 631 0.92 183521-3 611 664 0.92 161040-1 517 731 0.71 131040-2 542 733 0.74 141040-3 575 768 0.75 131062-1 573 864 0.66 81062-2 613 875 0.70 81062-3 671 945 0.71 91077-1 627 959 0.65 81077-2 729 1067 0.68 71077-3 777 1094 0.71 6

Claims (32)

1. a production has the method for the ultra-fine microstructure steel in one or more zones, it be included in any essence change before to the processing of austenite phase steel, induce fast with this, change substantially completely, this transformation makes in one or more microstructures zone and forms ultra-fine microstructure.

2. a production has the method for the ultra-fine microstructure steel in one or more zones, it comprises that the heating to steel makes it austenitizing, to the precooling of austenite phase steel and before any essence changes to the processing of austenite phase steel, so that induce fast, substantially completely change, this transformation makes in one or more microstructures zone and forms ultra-fine microstructure.

3. a production has the method for the ultra-fine microstructure steel in one or more zones, it comprises newly casting out the local precooling of austenite phase steel, before any essence changes to the processing of austenite phase steel, so that induce fast, transformation almost completely, this transformation make one or more microstructures zone form ultra-fine microstructure.

4. method according to claim 2 or 3 wherein, is by natural air cooling to the precooling of austenite phase steel, forced air-cooling or water-cooled, rate of cooling is between 50-2000K/min.

5. one kind according to each method in the aforementioned claim, and wherein, the processing that austenite phase steel is applied is distortion.

6. method according to claim 5, wherein, distortion is finished between 600-950 ℃ of temperature.

7. method according to claim 5, wherein, for the production of soft steel, distortion is finished between 700-950 ℃ of temperature.

8. a production has the method for the ultra-fine microstructure steel in one or more zones, it is included in the preceding deformation process to austenite phase steel of any essence transformation takes place, make the strain face or the strain gradient that form a horizontal tissue that collapses in the steel, induce fast, change substantially completely with this, this transformation makes in one or more microstructures district and forms ultra-fine microstructure.

9. method according to Claim 8, wherein, ultra-fine microstructure district comprises a complete transverse section tissue, preferably uniform ultra-fine microstructure.

10. method according to Claim 8, wherein, ultra-fine microstructure district comprises one or more upper layers of steel.

11. a method according to Claim 8, wherein, predetermined strain face is included in has relatively large strain in one or more upper layers, and the strain of heart portion is relatively low.

12. the method according to claim 11, wherein, the strained heterogeneity can be strengthened by the surface friction state that is deformed between steel and the texturing machine.

13. the method according to claim 5 or 8, wherein, distortion comprises steel by a pair of reverse rotation roll, and can make it depress 20～70% in the thickness of steel product direction.

14. the method according to claim 13, wherein, the thickness of steel product direction is depressed 30～60%.

15. the method according to claim 13 wherein, is only carried out a deformation.

16. the method according to claim 13, wherein, roll speed is taken between 0.1-5.0m/s.

17. the method according to claim 13, when relevant with claim 8, wherein, the ratio of the rolling radian (Ld) of roll and roll gap or rolling thickness (Hm) is greater than 10.

18. the method according to claim 2, wherein, the steel temperature is heated between 1000 ℃-1400 ℃.

19. the method according to claim 2, wherein, the steel temperature is heated between 1100 ℃-1300 ℃.

20. one kind according to each method in the aforementioned claim, wherein, steel is to cool off after phase transformation.

21. one kind according to each method in the aforementioned claim, wherein, austenitic average grain size is greater than 50 microns in the austenite phase steel.

22. one kind according to each method in the aforementioned claim, wherein, with the steel pre-treatment, reducing or to eliminate the forming core of crystal grain at the crystal boundary place in a large number, thereby more helps fast saidly with a kind of effective means, changes substantially completely.

23. the method according to claim 22, wherein pre-treatment comprise that the average austenite grain size that makes selected steel increases or other or comprise that also selected chemical treatment method weakens the crystal boundary reaction.

24. the method according to claim 22, wherein pre-treatment requires from comparatively high temps steel to be carried out precooling.

25. the steel with homogenous superfine microstructure, and be local superfine in one or more zones at least, its average grain size is not more than 3 microns in these zones.

26. the steel according to claim 25, centre average grain size≤10 of steel micron, upper layer grain-size≤2 micron.

27. the steel according to claim 26, wherein, the ferrite grain size of the ferrite crystal grain microstructure of most of volume is basically less than 3 microns.

28. the steel according to claim 25, wherein, the microstructure of steel is stratified.

29. the steel according to claim 28 have a plurality of ultra-fine microstructures district in one or more upper layers of steel, and heart portion layer has thicker microstructure.

30. cover production has the casting and the distortion set composite of the ultra-fine microstructure steel in one or more zones, the device that comprises casting Ovshinsky phase steel, receive and newly cast out the austenite device of steel mutually with local precooling, and any essence change before to the local refrigerative device of steel, induce one or more microstructures zone that transformation to ultra-fine microstructure takes place fast substantially completely thus.

31. a cover is according to the casting of claim 30 and distortion set composite, wherein, pouring device comprises a thin slab or band liquid filling machine and the treatment unit that comprises rolling equipment.

A 32. cover anamorphic attachment for cinemascope, can produce a kind of steel that has ultra-fine microstructure in one or more zones, it comprises the device that steel is heated to the austenite phase, the device that austenite phase steel is carried out local precooling, any essence is carried out local refrigerative device to austenite phase steel before changing, induce one or more microstructures zone to take place fast thus, substantially completely to the transformation of ultra-fine microstructure.

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