CN105177460B - A kind of method for preparing unimach using the multiple brilliant means of control - Google Patents

Abstract

The invention discloses a kind of method for preparing unimach using the multiple brilliant means of control, including following content：1st, added in smelting process into molten steel and control brilliant agent, utilized " gradient fusing point ", increase Enhancing Nucleation Density in molten steel, refine steel body initial grain；2nd, during solidification of molten steel, " combination pinning " crystal boundary, limitation crystal grain is grown up；3rd, solution strengthening；4th, function reparation.The ultra-fine grain steel obtained using the technology of the present invention is not only carried out in Cheng Ganghou; but by controlling crystal grain to grow up to obtain ultra-fine grain steel in smelting process; the combination property of steel is greatly improved; inexpensive production is realized, is advantageous to accomplish scale production using existing steel producing equipment.

Description

A kind of method for preparing unimach using the multiple brilliant means of control

Technical field

The present invention relates to the control of the initial grain of steel, metal material strengthen, the technology such as performance repairing and the smelting of steel, continuous casting Field, be a kind of method for preparing unimach using the brilliant means of multiple control, have production cost it is low, into the high spy of hardness of steel Point.

Background technology

With human social development and scientific and technological progress, the demand of high strength steel is increasing, thus how to realize low cost, Industrialization manufacture a new generation unimach turns into one of most important problem in steel research field.

At present, the high intensity of ferrous materials, generally use is based on crystal grain thinning theory, with deformation induced trans- formation, shape Become the forms such as heat treatment, microalloying, it is specific as follows：

The theoretical foundation of 1-1 crystal grain thinnings

The theoretical foundation of crystal grain thinning is from Hall and Page effect.Early in the fifties in last century, Hall and Page (Hall-Petch) research is found that the relation of crystallite dimension and steel body material intensity, is named as Hall-Page (Hall- Patch) relational expression：

σ in formula_yFor the yield limit of material；σ₀For lattice friction caused by mobile single dislocation；k_yFor constant, with The species property of material is relevant；D is average crystal grain diameter.

Hall-Page (effect) discloses material crystals size and there is a critical crystalline size on strength relationship (about 10 nanometers), when crystallite dimension is in more than this critical dimension latitude, crystallite dimension is smaller, and the strength of materials is bigger；If but After this critical dimension, crystallite dimension is smaller, and the intensity of material reduces on the contrary.Because Hall-Page by testing hand at that time The influence of section, after being proved with modern science and technology and laboratory facilities, although there are some deviations, its trend rule disclosed still may be used Using the basic theory as the strength of materials and crystallite dimension relation.

The evolution of 1-2 crystal grain thinnings

Theoretical according to Hall-Page, the main path for improving the performance of material is the grain structure of refiner material matrix, is enclosed Theoretical around this, in recent decades, people come in terms of the means of the intensity of raising steel are focused on refinement steel body crystal grain, achieve Many real achievements.The end of last century, most crystal grain thinning technology concentrates on to be carried out using steel phase transformation theory and technology to steel body The experimental study of crystal grain refinement, including：1. utilize phase transformation and the heat treatment (or thermomechanical treatment) of recrystallization；2. molten steel is rapidly cold But；3. mechanical alloying (is milled)；4. ultrafine particle sinters；5. noncrystal recrystallization etc., obtain certain progress.Into 21 century Since, with deepening constantly for crystal grain thinning technical research, means are also variation, by laying particular stress on non-smelting means (deformation heat Reason etc.) expand to the crystal grain refinement of smelting process.Main method includes：

1) deformation induced trans- formation crystal grain thinning.

Deformation induced trans- formation (deformation induced ferrite transformation) is to add mild steel Heat arrives austenite transition temperature Ac₃More than, it is incubated through a period of time, makes its austenitizing first, then with certain cooling speed Rate is cooled to Ar₃And Ac₃Between, then heavy reduction deformation is carried out, so as to obtain ultra-fine ferrite crystal grain.

Using deformation induced trans- formation technology, the combination property of ferrous materials can be increased substantially, is closed without increasing Gold dollar cellulose content.Deformation-induced ferrite transformation crystal grain thinning technology can be used for industrialized production, but solve the problems, such as hardly possible Degree is also very big, such as the difficulty in terms of the rolling equipment that brings of super large roll-force, test-material yardstick is limited bring be used for large-scale structure Part integrally roll or welding in terms of problem etc..In addition, its application limitation is in being only suitable in phase transition process that Austria can occur The low-carbon alloy steel of family name's body-ferrite transformation.

2) Refinement By Thermomechanical Treatment crystal grain method.

Thermomechanical treatment (deformation heating treatment) is effectively to comprehensively utilize shape to metal material Become and strengthen (processing hardening) and phase transformation strengthening, pressure processing is combined with heat treatment, make moulding process with obtaining final performance A kind of method united.More ripe thermomechanical treatment process has two classes：First, in relatively low austenitizing temperature model (slightly above Ac in enclosing₃) deformation process is carried out, then quench；Second, the steel after quenching is subjected to cold deformation, then austenitizing Quenching.

The characteristics of technique is that deformation temperature is low, and is carried out under the very big martensitic state of hardness, so material Resistance of deformation it is larger, have many difficulties applied to actual production, but the effect of its crystal grain thinning is fairly obvious.It is former using this Reason, 0.91um ultra-fine grain has been obtained on middle low carbon steel, has been applied on 304 austenitic stainless steels, obtains the super of 0.3um Fine grain structure.

Thermomechanical treatment process, in some steel fields, particularly have been obtained for being widely applied on small parts.

3) microalloying crystal grain thinning.

Make molten steel microalloying in smelting process, the positive effect of crystal grain thinning, steel can be improved to a certain extent Performance.A kind of micro alloying element improves the recrystallization temperature of steel matrix, while can reduce the coarsening rate of crystal grain, such as element W, Mo etc.；Another kind of is the alloying element to form carbon or nitrogen nanometric compound, such as V, Ti, Nb, and these compounds are brilliant to steel Grain length plays greatly strong inhibition, under refined crystalline strengthening and dispersion-strengtherning double action, as long as adding 0.03%- in steel 0.05% niobium, the yield strength of steel can improve more than 30%.

Before micro alloyed steel crystallisation solidification, due to the presence of the disperse phase of microalloy carboritride, austenite recrystallization When, relatively fine crystal grain is formd, in deformation process afterwards, crystal grain will not grow up, and its mechanism has the following aspects：① Austenite crystal grows up during prevention soaking；When heating of the ordinary steel steel before forging or rolling, soaking, austenite lattice is general Different degrees of it can grow up, with growing up for lattice, showing the matrix strength of tapping can decline.Micro alloyed steel V, Ti, Nb Carboritride undissolved particle pinning effect is played to austenite grain boundary, prevent growing up for its crystal grain.2. the Ovshinsky bodily form The recrystallization of austenite crystal is prevented during change.Because the carbon nitrogen of the microalloy element of strain induced precipitate in hot procedure Compound particles preferential precipitation on austenite grain boundary, sub boundary and dislocation line, so as to effectively prevent crystal boundary, sub boundary and The motion of dislocation line, so as to prevent recrystallization.3. the precipitation enhancement after ferrite transformation., will after ausforming The ferritic phase transformation of generation, now, there is substantial amounts of microalloy carboritride particle to be separated out in ferrite grain boundaries, what these were separated out Particle can equally play pinning effect to ferrite grain boundaries, prevent growing up for crystal grain.These particles also play precipitation strength Effect, improve the performances such as the intensity of steel matrix.Research shows, the size and its body of microalloy carboritride precipitation particles Fraction serves decisive role to ferrite lattice size, and precipitation particles is smaller, and volume fraction is bigger, then ferrite crystal grain It is smaller.Therefore precipitation particles is had less size and have larger volume fraction, in terms of being crystal grain refinement research One important topic.

But the simple crystal grain by microalloying refinement steel matrix, ultra-fine grain is realized, is very limited, often to tie Close the means such as deformation hot-working and realize that comprehensive refinement can just obtain preferable effect.But the method for microalloying crystal grain thinning is necessary By the alloy of costliness：V, Ti, Nb, particularly V, Nb alloy acquisition, can be brought greater impact to human environment.

Microalloying crystal grain thinning, the degree of refinement of crystal grain is limited (crystal grain >=5um, laboratory condition are issued to 1-2um), The yield strength of large-scale production ferrous materials substantially within 500MP ranks, increases cost on the contrary, noble metal alloy Adversely affected using to environment, so being limited using by a certain extent.

In recent years, also also deepened continuously from the research of molten steel crystallization process crystal grain thinning, the steel and materialogy of various countries Researcher also studies the method for obtaining ultra-fine grain ferrous materials in further investigated.At this stage, the above-mentioned of ultra-fine grain steel is produced Various means, it is most of still in research and development and the primary stage applied, current result of study is applied to actual production and also had very More difficult, the increase of the intensity of steel is difficult to have breakthrough.

At present, based on crystal grain thinning theory, carried in the form of deformation induced trans- formation, thermomechanical treatment, microalloying etc. The method of the intensity of high ferrous materials, some local domain of crystal grain thinning is mostly confined to, is difficult in the intensity of steel Breakthrough.Therefore, the breakthrough for improving ferrous materials comprehensive strength is realized, is the current steel task of top priority.

The content of the invention

To solve the above problems, the invention provides a kind of method for preparing unimach using the multiple brilliant means of control.

The present invention is a kind of method for controlling steel body crystallite dimension by multiple means, preparing superhigh intensity control crystalline substance steel.Control Brilliant steel is each Main Stage in the smelting of steel, crystallization process, and multiple control is realized to crystallite dimension, by the way that " refinement is initial The means of crystal grain, multiple reinforcing, combination pinning, recovery of performance ", the unimach of acquisition.

Main contents of the present invention are：

1st, added into raw material molten steel and control brilliant agent, utilized " gradient fusing point ", increase Enhancing Nucleation Density in molten steel, at the beginning of refining steel body Beginning crystal grain：

The addition opportunity for controlling brilliant agent is：After steel-making terminal and deslagging operation, added into molten steel and control brilliant agent.

It is target molten steel to add caused molten steel after controlling brilliant agent, and target molten steel carries out normal continuous casting through conticaster, in temperature Spend to require water quick cooling, 25~80 DEG C/min of intensity of cooling between 850~650 DEG C.

The percentage by weight of its raw material molten steel is：S≤0.01%, P≤0.01%；The control crystalline substance agent added into raw material molten steel Percentage by weight be：Cu 0.6-1.6, Sn 0.002-0.01, Zn0.001-0.05, Pb 0.002-0.01, Ni 0.2- 0.6, Mn 0.1-0.7, Ti 0.02-0.1, AL 0.02-0.2, Cr 0.2-0.5, N 0.008-0.05, Be 0.001-0.05, It the rest is iron and impurity.Note：The quality requirement (percentage by weight) of raw material molten steel is：S≤0.01%, P≤0.01%；

Its principle is in L+ δ and L+ γ regions, adds low melting point control crystalline substance element M, and M is diffused through in molten steel upon dissolution In journey oxide M is formed with the O elements in molten steel_nO_m, oxide is high melting compound；Or form carbon, nitrogen with C, N in steel Compound M_nC_m、MN.Each M_nO_m、M_nC_m, MN formed " gradient fusing point ", within the temperature range of molten steel progressively solidification crystallization (be less than After melting temperature), form trickle solid phase particle (micromicron level) of the disperse in molten steel, trickle particle under van der Waals interaction or Attract each other to form nanoscale molecular cluster." gradient fusing point " ensure that molten steel before liquid disappearance, and trickle particle turns into L+ δ With the core of iron carbon atom forming core in L+ γ regions.The nucleation process belongs to heterogeneous nucleation process, according to interface coherence principle, Iron carbon atom in cenotype is grown up in the different crystal plane of core particle for end liner, is grown up around nucleus particle Different Plane Crystal orientation is different between cenotype, turns into a different set of crystal (or having twin), and the particle as core finally turns into this group of crystal Public crystal boundary.

The addition of wafer element is controlled, is on the one hand [O] element in absorption steel, the less illeffects of [O], is on the other hand The Enhancing Nucleation Density of crystal in L+ δ and L+ γ regions is increased considerably.

Because Enhancing Nucleation Density is inversely proportional (cubic relationship) with crystallite dimension in unit volume, Enhancing Nucleation Density is bigger, crystal grain chi It is very little smaller.It is calculated, when Enhancing Nucleation Density improves about 800 times, grain size can drop to 500nm from 5um.In molten steel volume one In the case of fixed, solid phase particle or micel quantity are more, and number of nuclei is bigger, and the crystallite dimension of formation is smaller, thus refines The initial grain of L+ δ austenites and L+ γ austenites.

The core technology point of the present invention adds control wafer element in molten steel, the oxide and carbon, nitrogen of these control wafer elements Compound M_nO_m、M_nC_m, MN formed " gradient fusing point ", in L+ δ and L+ γ regions, liquid phase disappear before different temperatures section Interior formation solid phase particle, serves the effect of " continuing to increase Enhancing Nucleation Density ", ensure that between L+ δ austenites and L+ γ austenitic areas There is sufficiently large Enhancing Nucleation Density before interior all liquid phase crystallizations.According to this principle, the initial grain of steel body is refined, to finally give Fine grain steel body lays the foundation.

Specific method is：

1-1 refines austenite initial grain using the characteristics of controlling brilliant element tin (Sn) element：

On ordinary meaning, Sn is considered as harmful element in steel, and illeffects is mainly the high-temperature machinery for greatly reducing steel Performance, but in the scope that its content control present invention is specified and when being added according to application claims, initial grain can be refined And the intensity of steel is greatly improved, while the decay resistance of steel can be improved.

Simple substance Sn fusing point is low (231.89 DEG C), under steel smelting environment (1650 DEG C or so), there is the very big degree of superheat, because And have larger diffusion energy, dissolve in molten steel spread rapidly quickly, form the uniform molten steel of Sn elements.In diffusion process, most Just in the form of atom existing for [O] element reaction in Sn, with molten steel, generate SnO and SnO₂.SnO has volatility, but utilizes The addition manner of the present invention, because the effect of supersaturated [O] continues to aoxidize in molten steel, in addition to only a few SnO volatilizees, Sn is basic On be fully oxidized to SnO₂。

SnO₂It is high melting compound for tetragonal crystal system (a=b=0.4737nm, c=0.3186nm), fusing point is up to 1630 DEG C, boiling point is 1800 DEG C.The SnO generated in molten steel₂It is fine particle state, particle diameter is in skin less than its melting temperature In the range of rice (pm), it is considered as Secondary phase particle, turns into one of the core of δ austenitic iron carbon atom forming cores.

1-2 refines austenite initial grain using the characteristics of controlling brilliant element zinc (Zn) element：

Zinc does not add substantially in the smelting of steel.Simple substance Zn fusing point is low (419.5 DEG C), the disperse mechanism shape with element S n Together, there is the very big degree of superheat under steel smelting environment, thus have larger diffusion energy, dissolve in molten steel and spread rapidly quickly, Form the uniform molten steel of Zn elements.In diffusion process, initially in the form of atom existing for oversaturated [O] member in Zn, with molten steel Element reaction, generates ZnO.ZnO belongs to hexaplanar, is high melting compound, fusing point is up to 1975 DEG C.Aoxidize what is formed in diffusion ZnO is in Solid-State proton disperse with molten steel, in L+ δ regions, forming one of δ austenite matrix cores.

Thermodynamics experiment proves that part Zn is combined with S, generation ZnS (1020 DEG C of temperature below ZnS by isometric system α types It is changed into the β types of cubic crystal), 1700 DEG C of fusing point, solid phase particle is formed in L+ δ regions, forming core central role is played, adds Enhancing Nucleation Density, while reduce S illeffects.In addition, in 1600 DEG C of temperature and SiO₂Or AL₂O₃Under the conditions of plentiful, part The ZnO and SiO of disperse in molten steel₂Spend zinc silicate (Zn₂SiO₄, 1509 DEG C of fusing point), (part Zn and AL₂O₃Combine to form a kind of multiple Compound-ZnOAL₂O₃Gahnite thing phase), the free shape micel of nanoscale is formed, disperse is difficult to understand in L+ γ among molten steel Nucleation is still functioned as in family name's body crystallization process, increases number of nuclei, reduces crystallite dimension.

1-3 refines austenite initial grain using wafer element beryllium (Be) is controlled：

Beryllium is rare light metals element, and atomic radius is small (being less than various alkali metal), relative molecular weight small (9.01) etc.. Copper beryllium alloy (1100-1200 DEG C of fusing point) is added in steel, Cu and Be can be resolved into rapidly under the smelting condition of steel, because Be has Very strong oxidation potential (aoxidizing free energy close to AL), the Be of addition, mainly generates beryllium oxide BeO.Beryllium oxide is high-melting-point Compound, fusing point are up to 2353 DEG C, hexagonal crystal system, and without crystal transfer.Beryllium oxide forms solid phase particle size, brilliant less than control Every other element in element, trickle particle disperse in L+ δ austenites, can not only increase the shape in L+ δ regions well Cuclear density, it is not dissolved, can be distributed (dispersion-strengtherning) along crystal boundary with austenite after liquid phase disappearance.The characteristics of due to hexagonal crystal system, Crystal face slip system is seldom, therefore during strain is produced, dislocation motion is extremely limited, in addition beryllium oxide particle chi itself Very little small, hardness is high, and dislocation resistance has been increased considerably after being distributed along crystal boundary, the intensity to improving steel, especially yield strength Positive effect.

Copper-titanium alloy (970-1020 DEG C of fusing point) is added in steel, titanium dissolves generates TiN, TiC with [N] in steel, [C] afterwards, Fusing point distinguishes 2950 DEG C and 3067 DEG C.These high-melting-point carboritrides form trickle particle (micromicron level), act on above-mentioned member It is plain approximate, as one of core of L+ δ austenite forming cores in molten steel.

2nd, during solidification of molten steel, " combination pinning " crystal boundary, limitation crystal grain is grown up：

" the pinning combination " of precipitated phase is designed, the element for participating in pinning need to be selected.1. the principle of design alternative is Precipitate particle is small and disperse is as far as possible uniform；2. precipitate itself will have high rigidity and toughness simultaneously；3. Precipitation Temperature section Greatly, it is high to start Precipitation Temperature for part precipitate；4. drop out point is big to grain boundary dislocation resistance；It is 5. different with the reduction of temperature Precipitate separates out in gradient, the Precipitation Temperature distribution gradient of each precipitate, covers the temperature range that whole solid-phase grain is grown up.

In L+ δ and L+ γ regions, SnO₂, the dispersed part that is formed of the high melting compound such as ZnO, ZnO, BeO, TiN, TiC Number of nuclei greatly improved in point, has refined initial grain, is laid the foundation for refinement steel body crystal grain.In molten steel cooling and solidifying etc. During, because lattice free energy of growing up is negative value (△ G_j＜ 0) driving force that crystal grain is grown up be present.After the disappearance of steel body liquid phase Process of setting in, crystal grain in addition to itself grows up also have annex adjacent crystal, formed crystal stock trend.Now, limiter Growing up for grain, relies primarily on the means of pinning crystal boundary.

From after Zener proposes pinning theory, people are ceaselessly studied pinning theory, although various theoretical presence Difference, but it is believed that following relationship be present between the long large driving force of crystal grain (including subgrain) and pining force：

(γ/R_cr)-(K γ Z/ α)=0

Wherein：Crystal boundary energy between γ-initial grain；R_cr=initial grain critical radius；The ratio between K- crystal boundary energies (subgrain The ratio between crystal boundary energy between crystal boundary energy and initial grain between initial grain)；The Z- Zeners factor (mainly relevant with temperature)；α= Geometrical factor；

(γ/R_cr) it is driving force item, (K γ Z/ α) is pining force item (crystal grain grow up resistance).Above-mentioned relation formula shows, when When driving force is more than pining force, crystal grain continues to grow up, and when driving force and pinning dynamic balance, crystal grain stops growing up.

According to the achievement in research that China's researcher (Wang Xuelun etc.) is newest, two have been shifted out onto from the angle of power and energy The pinning formula of phase particle pinning crystal boundary, it is as follows：

N=(3/2-2/Z) * 1/8R* (4 /3v)^2/3*4□R²* 2r=(3/2-2/Z) * /r*R

WhereinFor critical Secondary phase particle number in unit volume；

N is the Secondary phase particle number required for the crystal grain that prevention radius is R is grown up；

R is the radius of matrix grain；

Z is the ratio between the radius of the adjacent crystal grain of crystal grain of growth (Z=1.5~1.7)；

R is Secondary phase particle radius：

WhenWhen, Secondary phase particle is less than the migration driving force of crystal boundary to the resistance of crystal boundary, and crystal grain may proceed to grow up； And work asWhen, crystal boundary will be lived by Secondary phase particle pinning, and crystal grain stops growing up.

The quantity N of Secondary phase particle, and proportional relations of crystal grain R, i.e. grain size R it is bigger, it is necessary to Secondary phase particle quantity It is more.

Because crystal grain is grown up in the presence of very big free energy, refined between L+ δ austenites and L+ γ austenitic areas Initial grain, before the pining force of formation is less than long large driving force, crystal grain can further grow up.Be limited the further of combinations grain Grow up, the means of " combination pinning " are employed herein, utilize a variety of pinning protons generated in different temperature ranges, nail Crystal boundary is pricked, hinders further growing up for crystal grain.

Specific method is：

2-1 aluminium nitride ALN pinning crystal boundaries：

In pneumatic steelmaking, EAF Steelmaking Process and LF refining furnace, metallic aluminium is added in steel, is the conventional means of steel-making. Purpose is the Strong oxdiative characteristic using metallic aluminium, realizes and residual oxygen is removed in steel, reduces influence of the oxygen field trash to the quality of steel, carries Gao Gang performance.Particle is separated out using ALN, pinning effect is played to crystal grain in crystal boundary, further growing up for crystal grain is prevented, is One of pith of " combination pinning " among the present invention.

Under the smelting of steel and cast cooling condition, meet AL₂O₃, ALN generation thermodynamic condition.According to thermodynamics Principle, the affinity of aluminium and oxygen is only second to calcium, magnesium, there is very strong oxidation potential energy (△_fG⁰=a+bT), therefore in steelmaking process The product being initially formed after middle addition metallic aluminium is AL₂O₃And AL₂O₃The compound of generation, most of AL₂O₃And AL₂O₃It is multiple Compound floats in smelting process enters slag phase, and small part is residued in molten steel.Under conditions of [N] is sufficient, with part [AL] Reaction generation ALN.

ALN is solid-solution in austenite due to being equally face-centred cubic structure, and with the decline of temperature, ALN is constantly analysed Go out.The ALN particle diameters that studies have shown that separates out are in 3-10nm, most hexagonal sheet, and part is conical, water chestnut shape or cube. After ALN is separated out, positioned at grain boundaries, the pinning proton to crystal boundary is formd, pinning effect is served to crystal boundary, sub boundary, simultaneously Hinder dislocation, it is suppressed that recrystallization, so as to limit further growing up for crystal grain.

ALN precipitations are relevant with temperature and AL, N content, and its relational expression is：

LgK_ALN=Lg [AL] [N]=- 7184/T+1.79

T is that ALN starts Precipitation Temperature (absolute temperature K) in formula, as shown in Figure 4.By finding out in figure, ALN solubility with Temperature declines and declined, and AL and N content are lower, and solubility is lower.

For AL contents when 0.04%, w [N] % are 0.018%, temperature is less than 1200 DEG C, and ALN starts to separate out, temperature in steel When dropping to 880 DEG C, about 90%ALN is separated out, and when temperature drops to 650 DEG C, almost all separates out.At that same temperature, ALN in steel Amount of precipitation increase with the increase of w (AL) % in steel.

ALN to the pinning effect of crystal boundary clearly.

It is pointed out that to ensure the ALN N element, it is necessary to enough that generates, added in this patent and control brilliant agent " nitridation Ferrochrome ", it is therefore an objective to the nitrogen pick-up in molten steel.

2-2 utilizes the compound of copper, forms the pinning particle to crystal boundary：

The fusing point of elemental copper is 1083.4 DEG C, and fusing point reduces after copper alloy, and control that brilliant agent uses in this case is bronze molten O'clock at 800 DEG C or so, the fusing point of brass because the trade mark is different and difference, typically at 950 DEG C or so, so in the bar of steel smelting It can rapidly be melted under part, and form compound and be solid-solution among the matrix of steel.After the liquid phase of steel disappears, it is solid-solution in austenite Copper compound, separated out with the reduction of temperature in crystal boundary, form the pinning particle for hindering crystal grain to grow up.

Concrete mode is：

2-2-1Cu₂S separates out the pinning to crystal boundary：

Add after controlling brilliant elemental copper, a part of Cu and harmful element [S] the reaction generation Cu in molten steel₂S is simultaneously solid-solution in steel In body.Relevant experimental study shows, when the temperature of steel is less than Cu₂(Cu solubility products are complete solid to S solution temperature (1300 DEG C) below The function of solubility temperature) when, Cu₂S starts to separate out.The main pattern of precipitate is spherical, is in granular form.

Cu in hot rolled plate₂S precipitates particle size is 10-30nm, and indivedual large-sizes are 40-60nm, and average diameter is 19nm, distribution density 1.3^*10¹⁴Individual/cm³.With the further reduction of temperature, Cu₂S is constantly separated out, the lower precipitate of temperature Particle diameter is smaller, or even at 400 DEG C, also small part separates out.

Cu₂It is distributed in after S precipitation between crystal boundary, forms pinning point, crystal grain is grown up and serves good inhibiting effect, It is the pith of " pinning combination " in the present invention.In addition in [Cu] element absorption steel [S], S is made to generate Cu₂S has formed pinning Secondary phase particle, the invigoration effect of steel body is served, so as to reduce S illeffects.

Pinning effects of the 2-2-2 intermetallic compounds Fe-Cu precipitate ε-Cu to crystal boundary

The copper in brilliant agent is controlled, except with Cu₂Outside S-shaped formula separates out, most copper is dissolved in formation Fe-Cu alloys in molten steel.

Cu plays the role of to expand γ phase regions, forms limit solid solution.After Fe-Cu alloy solid solutions, Cu is as solute atoms meeting Localized clusters, in the enrichment state of solute atoms.The domain of order that Cu is solid-solution in iron-based is uneven, particle diameter about 5- 20nm, when the external causes such as temperature change, this shortrange order farmland is broken, and Cu is from iron-based solid solution with ε-Cu frame mode Separate out.Cu content is dissolved in wherein in elements such as 80% or so, Ni in ε-Cu compositions, belongs to intermetallic compound.ε-Cu compositions It is relevant with coherent element in steel matrix, and vary with temperature and change.ε-Cu precipitated phases are fcc structure, initially with spherical precipitation Thing is separated out in crystal boundary, and final pattern is determined by machine direction and processing mode.

Experimental study shows, 1) three kinds of forms are distributed with Cu：1. in-situ precipitate；It is 2. rich to crystal boundary (sub boundary) Collection；3. to high temperature the second phase segregation through diffusion；2) when being tempered for 600 DEG C, based on the precipitation on dislocation line and crystal boundary enrichment, at Cu In coherent precipitate state.The copper-rich particle or ε-Cu of coherent precipitate, the tensile strength of steel can be made and yield strength while improved.

2-3 utilizes the characteristics of manganese element, participates in pinning combination, realizes solution strengthening：

Simple substance manganese, atomic weight 54.94, atomic radius 124pm, 1244 DEG C of fusing point, 1962 DEG C of boiling point.Effect of the manganese in steel Mainly deoxidation and alloying.Manganese is one of most important deoxidier in steel-making, and almost all of steel grade is required for using manganese deoxidation, First, because manganese has higher affinity with oxygen, second, because relatively low with caused oxide ester mp after manganese deoxidation, easily Make to float in slag on deoxidation products, improve the degree of purity of steel.In addition, use manganese deoxidation, moreover it is possible to increase the strong deoxidiers of Si and AL Deoxidation effect.

Manganese is in steel in addition to forming solid solution, moreover it is possible to forms MnS, Mn3C and a small amount of MnSi, FeMnSi, oxide (such as MnO, MnOSiO2, MnOAL₂O₃Deng) and nitride etc..When oxygen is relative to manganese abundance, the oxide of manganese is mainly Mn₃O₄, that be solid-solution in steel grade is mainly MnO.

In general, S presence is had in steel unavoidably, and solubility very littles of the S in solid solution, S form FeS in steel (1190 DEG C of fusing point), has very big damaging effect.FeS forms eutectiferous fusing point with iron in steel and there was only 988 DEG C, when steel coagulates Gu after, the analysis of FeS eutectics collects in primary grain boundaries, and the FeS of grain boundaries will be melted in the operation of rolling, be attenuated to crystalline substance significantly Adhesion between grain, cause " hot-short " phenomenon of steel.Steel grade, which adds enough rear S, can preferentially generate MnS.MnS is high-melting-point Compound (1620 DEG C of fusing point), so as to greatly reduce hot-short harm.

MnS has three kinds of forms, and α-MnS, β-MnS, γ-MnS.Under high temperature, i.e., under the conditions of steel-making in α-MnS (cube Crystallographic system) form, isometric system.MnS is distributed with what state in steel, depending on the composition such as O, AL, C, Si in steel.MnS distribution 1. state has without using in the steel of AL deoxidations, in spherical, random distribution；2. divide on a small quantity using in the steel of AL deoxidations in fan-shaped Cloth is distributed along crystal boundary；3. plus AL is high, when residual AL is more in steel, in block random distribution；It is desirable that be MnS along crystal boundary or Fan-shaped is distributed, and to improve dislocation resistance, improves steel body intensity.

Before starting precipitation with most of precipitate after liquid phase disappearance, crystal grain, which has, is grown up, and crystal grain is grown up early Control, can just ensure to refine the effect of initial product grain, this is one of key means of refined crystalline strengthening.It can be seen from figure below Even if in the case where sulfur content is relatively low, MnS starts Precipitation Temperature as 1220 DEG C or so.Because Precipitation Temperature is higher, precipitate MnS is one of pinning particle most formed early in crystal boundary, therefore has very strong refined crystalline strengthening effect.

MnS is complete, and solid solubility temperature is very high, is necessarily separated out in the cooling procedure of steel due to supersaturation.

In addition, in steel in the case of Mn abundances, MnC can be generated.MnS, MnO and MnC can separate out in crystal boundary, in boundary shape Into pinning particle, particle is smaller, and the effect of pinning crystal boundary is better.To prevent that Mn compounds are excessive in steel, promote growing up for crystal grain, In steel plus manganese is wanted to be less than 0.7%.

3 solution strengthening：

Solution strengthening is that alloying element is solid-solution in parent metal and causes a certain degree of distortion of lattice so that alloy is strong Spend the phenomenon improved.Its mechanism is：When the elastic distortion in solid solution caused by the atomic radius of solute and solvent, with dislocation Between caused elastic interaction, have inhibition to moving dislocation on slide surface；Second, the segregation on skid wire Constraint and pinning effect of the solute atoms (KESHI gas mass) to dislocation.The concrete measure of solution strengthening is as follows in the present invention：

3-1 utilizes the characteristics of nickel element, realizes solution strengthening：

Elemental nickel melts molecular weight 58.69, atomic radius 1.62,1453 DEG C of fusing point, 2732 DEG C of boiling point, density 8.09.Nickel is made It can make steel that there is advanced mechanical performance for alloying element, you can to make steel that there is toughness, anti-corrosion acid-resisting, high magnetic conductivity, and make Crystal grain refinement improves quenching degree, increase hardness etc..

Invigoration effect of the nickel in steel belongs to solution strengthening.Nickel expands γ phase regions in steel, forms unlimited solid solution.In α Maxima solubility is 10% or so in iron.Do not form stable compound in steel, mainly exist in the form of solid solution, not shape Into carboritride.Although invigoration effect is medium, the effect for having refined ferrite crystal grain is served, under the same conditions, Improve the plasticity and toughness of steel, particularly low-temperature flexibility.

Found in experimental study, precipitated phase nickel AL, Ti element forms a kind of transition compound Ni₃(AL, Ti), form a kind of With the γ ' phases with face-centred cubic structure, separated out after 760 DEG C of timeliness in crystal boundary.This Ni₃(AL, Ti)-γ ' phases, no matter In crystals or crystal boundary, very big dislocation resistance can be all produced, has and strengthens effect well.

3-2 utilizes the characteristics of chromium, realizes the reinforcing based on solid solution：

The atomic weight of chromium is 51.996,1857 DEG C of simple substance chromium fusing point, 2672 DEG C of boiling point, density 7.2g/cm3.Chromium is alloy One of most widely used element in steel production.Chromium can strengthen the mechanical performance and wearability of steel, increase quenching degree and the quenching of steel Non-deformability afterwards, strengthen elasticity, diamagnetism, corrosion resistance and the heat resistance of steel.

Form of the chromium in steel is more complicated, in addition to being partly present in iron solid solution, it is also possible to form carbide (FeCr) 3C, Cr3C2, Cr7C3, Cr23C6 etc.), nitride (CrN, Cr2N), sulfide (CrS, FeSCr2S3), oxide [CrxOy, (Fe, Mn) OCr2O3] and metallic iron compound (FeCr) and silicide (Cr3Si etc.).Wherein with the carbonization of chromium Thing and nitride state are relatively stable.

Chromium forms continuous solid solution with iron, reduces austenite phase field city.Chromium forms a variety of carbide with carbon, affine with carbon Power is more than iron and manganese and can form intermetallic compound σ phases (FeCr) with iron less than chromium such as tungsten, molybdenums.

Chromium is middle carbide, and the chromium part displacement iron in steel forms alloyed cementite, and it is stable to improve its Property；A part is dissolved in ferrite, is produced solution strengthening, is improved ferritic intensity and hardness.

Cr is infinitely dissolved in α iron, and maxima solubility is 12.5% in γ iron.The alloy of chromium is likely to form when content is low Cementite (Fe, Cr) 3C, and with the increase of chromium content, the carbide in steel is progressively changed into Cr23C6 and Cr7C3.Because chromium is in Austria Diffusion velocity in family name's body is smaller, hinders Carbon diffusion in addition, thus can improve the stability of austenite.Chromium is also because reducing phase Temperature, so as to make carbide be separated out in lower temperature, make tissue and carbide refinement.In the higher steel alloy of chromium content Chromium has the trend for making the scattered isolated distribution of carbide.

Cr₂₃C₆It is solid-solution in the matrix of steel, forms orderly γ ' phases, γ ' is in mutually face-centred cubic structure, is had very high Atomic binding forces, have very strong solution strengthening effect in crystal, even if at relatively high temperatures (≤760 DEG C), dislocation is cut Cut and pass through γ ' phase resistances, it is much bigger more than the other parts of matrix, therefore have good solid solution strengthening effect to steel, can be with very little Obtain high tensile strength and yield strength.

4 function reparations：

A variety of alloying elements are employed herein, the effect pros and cons that each alloying element is played coexist.To maximize favourable factors and minimize unfavourable ones, The whole synthesis performance of steel is improved, it is necessary to which the side effect to alloy part element carries out necessary reparation.

4-1 adds Ni elements, repairs " copper brittleness " because being brought using copper：

It is one of essential element to control Cu in brilliant steel, and to go the side effect of copper removal, Ni (the 1/ of Cu contents is added in steel More than 3) when, the generation of copper brittleness can be avoided.The solid solution that nickel is formed in steel, the effect of fining ferrite grains is served, The plasticity and toughness of steel are improved simultaneously.

Be elements are added in 4-2 steel：

Using BeO in steel the trickle particle of disperse characteristic, improve yield strength under identical stiffness conditions.

4-3 utilizes the combined characteristic for controlling wafer element：

The comprehensive tensile strength for improving steel body, yield strength, ductility, toughness, corrosion resistance, weldability, creep resistance Etc. performance, reach the purpose of comprehensive repair.

Brief description of the drawings

Fig. 1 is iron-carbon diagram in L+ δ and L+ γ regions

Fig. 2 is crystallite dimension R and critical binomial particle number N relation curve (r=10um)

Fig. 3 is crystallite dimension R and critical binomial particle number N relation curve (r=20um)

Fig. 4 is solubility curves of the ALN in steel

Fig. 5 is AL mass fraction and the graph of a relation of ALN amount of precipitations under different temperatures in steel

The graph of a relation of solid solution product and temperature that Fig. 6 is MnS

Fig. 7 is the performance indications figure of the high strength steel prepared with this method

Embodiment

This patent is described further with reference to embodiment：

A kind of method for preparing unimach using the multiple brilliant means of control, main contents of the present invention are：

1st, added into raw material molten steel and control brilliant agent, utilized " gradient fusing point ", increase Enhancing Nucleation Density in molten steel, at the beginning of refining steel body Beginning crystal grain：

The addition opportunity for controlling brilliant agent is：After steel-making terminal and deslagging operation, added into molten steel and control brilliant agent.

It is target molten steel to add caused molten steel after controlling brilliant agent, and target molten steel carries out normal continuous casting through conticaster, in temperature Spend to require water quick cooling, 25~80 DEG C/min of intensity of cooling between 850~650 DEG C.

The percentage by weight of its raw material molten steel is：S≤0.01%, P≤0.01%；The control crystalline substance agent added into raw material molten steel Percentage by weight be：Cu 0.6-1.6, Sn 0.002-0.01, Zn0.001-0.05, Pb 0.002-0.01, Ni 0.2- 0.6, Mn 0.1-0.7, Ti 0.02-0.1, AL 0.02-0.2, Cr 0.2-0.5, N 0.008-0.05, Be 0.001-0.05, It the rest is iron and impurity.

It is target molten steel to add caused molten steel after controlling brilliant agent, and target molten steel carries out normal continuous casting through conticaster, in temperature Spend to require water cooling between 850~650 DEG C.

Its principle is (see Fig. 1) in L+ δ and L+ γ regions, adds low melting point control crystalline substance element M, M is upon dissolution in molten steel In interior diffusion process oxide M is formed with the O elements in molten steel_nO_m, oxide is high melting compound；Or with C, N shape in steel Into carbon, nitrogen compound M_nC_m、MN.Each M_nO_m、M_nC_m, MN formed " gradient fusing point ", within the temperature range of molten steel progressively solidification knot Brilliant (after being less than melting temperature), trickle solid phase particle (micromicron level) of the disperse in molten steel is formed, trickle particle is in Van der Waals force Act on down or attract each other to form nanoscale molecular cluster." gradient fusing point " ensure that molten steel before liquid disappearance, trickle matter Point turns into the core of iron carbon atom forming core in L+ δ and L+ γ regions.The nucleation process belongs to heterogeneous nucleation process, according to interface Coherence principle, the iron carbon atom in cenotype are grown up in the different crystal plane of core particle for end liner, different around nucleus particle Crystal orientation is different between the cenotype that plane is grown up, and turns into a different set of crystal (or having twin), the particle as core finally into For the public crystal boundary of this group of crystal.

The addition of wafer element is controlled, is on the one hand [O] element in absorption steel, the less illeffects of [O], is on the other hand The Enhancing Nucleation Density of crystal in L+ δ and L+ γ regions is increased considerably.

Because Enhancing Nucleation Density is inversely proportional (cubic relationship) with crystallite dimension in unit volume, Enhancing Nucleation Density is bigger, crystal grain chi It is very little smaller.It is calculated, when Enhancing Nucleation Density improves 750 times, grain size can drop to 500nm from 5um.In molten steel given volume In the case of, solid phase particle or micel quantity are more, and number of nuclei is bigger, and the crystallite dimension of formation is smaller, has thus refined L The initial grain of+δ austenites and L+ γ austenites.

The core technology point of the present invention adds control wafer element in molten steel, the oxide and carbon, nitrogen of these control wafer elements Compound M_nO_m、M_nC_m, MN formed " gradient fusing point ", in L+ δ and L+ γ regions, liquid phase disappear before different temperatures section Interior formation solid phase particle, serves the effect of " continuing to increase Enhancing Nucleation Density ", ensure that between L+ δ austenites and L+ γ austenitic areas There is sufficiently large Enhancing Nucleation Density before interior all liquid phase crystallizations.According to this principle, the initial grain of steel body is refined, to finally give Fine grain steel body lays the foundation.

Specific method is：

1-1 refines austenite initial grain using the characteristics of controlling brilliant element tin (Sn) element：

On ordinary meaning, Sn is considered as harmful element in steel, and illeffects is mainly the high-temperature machinery for greatly reducing steel Performance, but in the scope that its content control present invention is specified and when being added according to application claims, initial grain can be refined And the intensity of steel is greatly improved, while the decay resistance of steel can be improved.

Simple substance Sn fusing point is low (231.89 DEG C), under steel smelting environment (1650 DEG C or so), there is the very big degree of superheat, because And have larger diffusion energy, dissolve in molten steel spread rapidly quickly, form the uniform molten steel of Sn elements.In diffusion process, most Just in the form of atom existing for [O] element reaction in Sn, with molten steel, generate SnO and SnO₂.SnO has volatility, but utilizes The addition manner of the present invention, because the effect of supersaturated [O] continues to aoxidize in molten steel, in addition to only a few SnO volatilizees, Sn is basic On be fully oxidized to SnO₂。

SnO₂It is high melting compound for tetragonal crystal system (a=b=0.4737nm, c=0.3186nm), fusing point is up to 1630 DEG C, boiling point is 1800 DEG C.The SnO generated in molten steel₂It is fine particle state, particle diameter is in skin less than its melting temperature In the range of rice (pm), it is considered as Secondary phase particle, turns into one of the core of δ austenitic iron carbon atom forming cores.

1-2 refines austenite initial grain using the characteristics of controlling brilliant element zinc (Zn) element：

Zinc does not add substantially in the smelting of steel.Simple substance Zn fusing point is low (419.5 DEG C), the disperse mechanism shape with element S n Together, there is the very big degree of superheat under steel smelting environment, thus have larger diffusion energy, dissolve in molten steel and spread rapidly quickly, Form the uniform molten steel of Zn elements.In diffusion process, initially in the form of atom existing for oversaturated [O] member in Zn, with molten steel Element reaction, generates ZnO.ZnO belongs to hexaplanar, is high melting compound, fusing point is up to 1975 DEG C.Aoxidize what is formed in diffusion ZnO is in Solid-State proton disperse with molten steel, in L+ δ regions, forming one of δ austenite matrix cores.

Thermodynamics experiment proves that part Zn is combined with S, generation ZnS (1020 DEG C of temperature below ZnS by isometric system α types It is changed into the β types of cubic crystal), 1700 DEG C of fusing point, solid phase particle is formed in L+ δ regions, forming core central role is played, adds Enhancing Nucleation Density, while reduce S illeffects.In addition, in 1600 DEG C of temperature and SiO₂Or AL₂O₃Under the conditions of plentiful, part The ZnO and SiO of disperse in molten steel₂Spend zinc silicate (Zn₂SiO₄, 1509 DEG C of fusing point), (part Zn and AL₂O₃Combine to form a kind of multiple Compound-ZnOAL₂O₃Zinc-aluminium point product stone thing phase), the free shape micel of nanoscale is formed, disperse is difficult to understand in L+ γ among molten steel Nucleation is still functioned as in family name's body crystallization process, increases number of nuclei, reduces crystallite dimension.

1-3 refines austenite initial grain using wafer element beryllium (Be) is controlled：

Beryllium is rare light metals element, and atomic radius is small (being less than various alkali metal), relative molecular weight small (9.01) etc.. Copper beryllium alloy (1100-1200 DEG C of fusing point) is added in steel, Cu and Be can be resolved into rapidly under the smelting condition of steel, because Be has Very strong oxidation potential (aoxidizing free energy close to AL), the Be of addition, mainly generates beryllium oxide BeO.Beryllium oxide is high-melting-point Compound, fusing point are up to 2353 DEG C, hexagonal crystal system, and without crystal transfer.Beryllium oxide forms solid phase particle size, brilliant less than control Every other element in element, trickle particle disperse in L+ δ austenites, can not only increase the shape in L+ δ regions well Cuclear density, it is not dissolved, can be distributed (dispersion-strengtherning) along crystal boundary with austenite after liquid phase disappearance.The characteristics of due to hexagonal crystal system, Crystal face slip system is seldom, therefore during strain is produced, dislocation motion is extremely limited, in addition beryllium oxide particle chi itself Very little small, hardness is high, and dislocation resistance has been increased considerably after being distributed along crystal boundary, the intensity to improving steel, especially yield strength Positive effect.

Copper-titanium alloy (970-1020 DEG C of fusing point) is added in steel, titanium dissolves generates TiN, TiC with [N] in steel, [C] afterwards, Fusing point distinguishes 2950 DEG C and 3067 DEG C.These high-melting-point carboritrides form trickle particle (micromicron level), act on above-mentioned member It is plain approximate, as one of core of L+ δ austenite forming cores in molten steel.

2nd, during solidification of molten steel, " combination pinning " crystal boundary, limitation crystal grain is grown up：

" the pinning combination " of precipitated phase is designed, the element for participating in pinning need to be selected.1. the principle of design alternative is Precipitate particle is small and disperse is as far as possible uniform；2. precipitate itself will have high rigidity and toughness simultaneously；3. Precipitation Temperature section Greatly, it is high to start Precipitation Temperature for part precipitate；4. drop out point is big to grain boundary dislocation resistance；It is 5. different with the reduction of temperature Precipitate separates out in gradient, the Precipitation Temperature distribution gradient of each precipitate, covers the temperature range that whole solid-phase grain is grown up.

In L+ δ and L+ γ regions, SnO₂, the dispersed part that is formed of the high melting compound such as ZnO, ZnO, BeO, TiN, TiC Number of nuclei greatly improved in point, has refined initial grain, is laid the foundation for refinement steel body crystal grain.In molten steel cooling and solidifying etc. During, because character free energy of growing up is negative value (△ G_j＜ 0) driving force that crystal grain is grown up be present.After the disappearance of steel body liquid phase Process of setting in, crystal grain in addition to itself grows up also have annex adjacent crystal trend.Now, limiter grain is grown up, Rely primarily on the means of pinning crystal boundary.

From after Zener proposes pinning theory, people are ceaselessly studied pinning theory, although various theoretical presence Difference, but it is believed that following relationship be present between the long large driving force of crystal grain (including subgrain) and pining force：

(γ/R_cr)-(K γ Z/ α)=0

Wherein：γ -- crystal boundary energy between initial grain；R_cr=initial grain critical radius；The ratio between K-- crystal boundary energies (two para-crystals The ratio between crystal boundary energy between crystal boundary energy and initial grain between grain and initial grain)；The Z-- Zeners factor (mainly relevant with temperature)；α =geometrical factor；

(γ/R_cr) it is driving force item, (K γ Z/ α) is pining force item (crystal grain grow up resistance).Above-mentioned relation formula shows, when When driving force is more than pining force, crystal grain continues to grow up, and when driving force and pinning dynamic balance, crystal grain stops growing up.

According to the achievement in research that China's researcher (Wang Xuelun etc.) is newest, two have been shifted out onto from the angle of power and energy The pinning formula of phase particle pinning crystal boundary, it is as follows：

N=(3/2-2/Z) * 1/8R* (4 /3v)^2/3*4□R²* 2r=(3/2-2/Z) * /r*R

WhereinFor critical Secondary phase particle number in unit volume；

N is the Secondary phase particle number required for the crystal grain that prevention radius is R is grown up；

R is the radius of matrix grain；

Z is the ratio between the radius of the adjacent crystal grain of crystal grain of growth (Z=1.5~1.7)；

R is Secondary phase particle radius：

WhenWhen, Secondary phase particle is less than the migration driving force of crystal boundary to the resistance of crystal boundary, and crystal grain may proceed to grow up； And work asWhen, crystal boundary will be lived by Secondary phase particle pinning, and crystal grain stops growing up.

The quantity N of Secondary phase particle, and proportional relations of crystal grain R, i.e. grain size R it is bigger, it is necessary to Secondary phase particle quantity It is more.When the relation curve that Secondary phase particle radius is 10nm cun, crystallite dimension R and critical binomial particle number N, as shown in Figure 2.

When Secondary phase particle radius is 20nm, crystallite dimension R and critical binomial particle number N relation curve, such as Fig. 3 institutes Show.

Because crystal grain is grown up in the presence of very big free energy, refined between L+ δ austenites and L+ γ austenitic areas Initial grain, before the pining force of formation is less than long large driving force, crystal grain can further grow up.Be limited the further of combinations grain Grow up, the means of " combination pinning " are employed herein, utilize a variety of pinning protons generated in different temperature ranges, nail Crystal boundary is pricked, hinders further growing up for crystal grain.

Specific method is：

2-1 aluminium nitride ALN pinning crystal boundaries：

In pneumatic steelmaking, EAF Steelmaking Process and LF refining furnace, metallic aluminium is added in steel, is the conventional means of steel-making. Purpose is the Strong oxdiative characteristic using metallic aluminium, realizes and residual oxygen is removed in steel, reduces influence of the oxygen field trash to the quality of steel, carries Gao Gang performance.Particle is separated out using ALN, pinning effect is played to crystal grain in crystal boundary, further growing up for crystal grain is prevented, is One of pith of " combination pinning " among the present invention.

Under the smelting of steel and cast cooling condition, meet AL₂O₃, ALN generation thermodynamic condition.According to thermodynamics Principle, the affinity of aluminium and oxygen is only second to calcium, magnesium, there is very strong oxidation potential energy (△_fG⁰=a+bT), therefore in steelmaking process The product being initially formed after middle addition metallic aluminium is AL₂O₃And AL₂O₃The compound of generation, most of AL₂O₃And AL₂O₃It is multiple Compound floats in smelting process enters slag phase, and small part is residued in molten steel.Under conditions of [N] is sufficient, with part [AL] Reaction generation ALN.

ALN is solid-solution in austenite due to being equally face-centred cubic structure, and with the decline of temperature, ALN is constantly analysed Go out.The ALN particle diameters that studies have shown that separates out are in 3-10nm, most hexagonal sheet, and part is conical, water chestnut shape or cube. After ALN is separated out, positioned at grain boundaries, the pinning proton to crystal boundary is formd, pinning effect is served to crystal boundary, sub boundary, simultaneously Hinder dislocation, it is suppressed that recrystallization, so as to limit further growing up for crystal grain.

ALN precipitations are relevant with temperature and AL, N content, and its relational expression is：

LgK_ALN=Lg [AL] [N]=- 7184/T+1.79

T is that ALN starts Precipitation Temperature (absolute temperature K) in formula, as shown in Figure 4.By finding out in figure, ALN solubility with Temperature declines and declined, and AL and N content are lower, and solubility is lower.Fig. 4 has reacted different aluminum contents of ALN in steel and nitrogenous Precipitation Temperature under the conditions of amount starts Precipitation Temperature.

For AL contents when 0.04%, w [N] % are 0.018%, temperature is less than 1200 DEG C, and ALN starts to separate out, temperature in steel When dropping to 880 DEG C, about 90%ALN is separated out, and when temperature drops to 650 DEG C, almost all separates out.At that same temperature, ALN in steel Amount of precipitation increase with the increase of w (AL) % in steel, as shown in Figure 5.

ALN to the pinning effect of crystal boundary clearly.

It is pointed out that to ensure the ALN N element, it is necessary to enough that generates, added in this patent and control brilliant agent " nitridation Ferrochrome ", it is therefore an objective to the nitrogen pick-up in molten steel.

2-2 utilizes the compound of copper, forms the pinning particle to crystal boundary：

The fusing point of elemental copper is 1083.4 DEG C, and fusing point reduces after copper alloy, and control that brilliant agent uses in this case is bronze molten O'clock at 800 DEG C or so, the fusing point of brass because the trade mark is different and difference, typically at 950 DEG C or so, so in the bar of steel smelting It can rapidly be melted under part, and form compound and be solid-solution among the matrix of steel.After the liquid phase of steel disappears, it is solid-solution in austenite Copper compound, separated out with the reduction of temperature in crystal boundary, form the pinning particle for hindering crystal grain to grow up.

Concrete mode is：

2-2-1Cu₂S separates out the pinning to crystal boundary：

Add after controlling brilliant elemental copper, a part of Cu and harmful element [S] the reaction generation Cu in molten steel₂S is simultaneously solid-solution in steel In body.Relevant experimental study shows, when the temperature of steel is less than Cu₂(Cu solubility products are complete solid to S solution temperature (1300 DEG C) below The function of solubility temperature) when, Cu₂S starts to separate out.The main pattern of precipitate is spherical, is in granular form.

Cu in hot rolled plate₂S precipitates particle size is 10-30nm, and indivedual large-sizes are 40-60nm, and average diameter is 19nm, distribution density 1.3^*10¹⁴Individual/cm³.With the further reduction of temperature, Cu₂S is constantly separated out, the lower precipitate of temperature Particle diameter is smaller, or even at 400 DEG C, also small part separates out.

Cu₂It is distributed in after S precipitation between crystal boundary, forms pinning point, crystal grain is grown up and serves good inhibiting effect, It is the pith of " pinning combination " in the present invention.In addition in [Cu] element absorption steel [S], S is made to generate Cu₂S has formed pinning Secondary phase particle, the invigoration effect of steel body is served, so as to reduce S illeffects.

Pinning effects of the 2-2-2 intermetallic compounds Fe-Cu precipitate ε-Cu to crystal boundary

The copper in brilliant agent is controlled, except with Cu₂Outside S-shaped formula separates out, most copper is dissolved in formation Fe-Cu alloys in molten steel.

Cu plays the role of to expand γ phase regions, forms limit solid solution.After Fe-Cu alloy solid solutions, Cu is as solute atoms meeting Localized clusters, in the enrichment state of solute atoms.The domain of order that Cu is solid-solution in iron-based is uneven, particle diameter about 5- 20nm, when the external causes such as temperature change, this shortrange order farmland is broken, and Cu is from iron-based solid solution with ε-Cu frame mode Separate out.Cu content is dissolved in wherein in elements such as 80% or so, Ni in ε-Cu compositions, belongs to intermetallic compound.ε-Cu compositions It is relevant with coherent element in steel matrix, and vary with temperature and change.ε-Cu precipitated phases are fcc structure, initially with spherical precipitation Thing is separated out in crystal boundary, and final pattern is determined by machine direction and processing mode.

Experimental study shows, 1) three kinds of forms are distributed with Cu：1. in-situ precipitate；It is 2. rich to crystal boundary (sub boundary) Collection；3. to high temperature the second phase segregation through diffusion；2) when being tempered for 600 DEG C, based on the precipitation on dislocation line and crystal boundary enrichment, at Cu In coherent precipitate state.The copper-rich particle or ε-Cu of coherent precipitate, the tensile strength of steel can be made and yield strength while improved.

2-3 utilizes the characteristics of manganese element, participates in pinning combination, realizes solution strengthening：

Simple substance manganese, atomic weight 54.94, atomic radius 124pm, 1244 DEG C of fusing point, 1962 DEG C of boiling point.Effect of the manganese in steel Mainly deoxidation and alloying.Manganese is one of most important deoxidier in steel-making, and almost all of steel grade is required for using manganese deoxidation, First, because manganese has higher affinity with oxygen, second, because relatively low with caused oxide ester mp after manganese deoxidation, easily Make to float in slag on deoxidation products, improve the degree of purity of steel.In addition, use manganese deoxidation, moreover it is possible to increase the strong deoxidiers of Si and AL Deoxidation effect.

Manganese is in steel in addition to forming solid solution, moreover it is possible to forms MnS, Mn3C and a small amount of MnSi, FeMnSi, oxide (such as MnO, MnOSiO2, MnOAL₂O₃Deng) and nitride etc..When oxygen is relative to manganese abundance, the oxide of manganese is mainly Mn₃O₄, that be solid-solution in steel grade is mainly MnO.

In general, S presence is had in steel unavoidably, and solubility very littles of the S in solid solution, S form FeS in steel (1190 DEG C of fusing point), has very big damaging effect.FeS forms eutectiferous fusing point with iron in steel and there was only 988 DEG C, when steel coagulates Gu after, the analysis of FeS eutectics collects in primary grain boundaries, and the FeS of grain boundaries will be melted in the operation of rolling, be attenuated to crystalline substance significantly Adhesion between grain, cause " hot-short " phenomenon of steel.Steel grade, which adds enough rear S, can preferentially generate MnS.MnS is high-melting-point Compound (1620 DEG C of fusing point), so as to greatly reduce hot-short harm.

MnS has three kinds of forms, and α-MnS, β-MnS, γ-MnS.Under high temperature, i.e., under the conditions of steel-making in α-MnS (cube Crystallographic system) form, isometric system.MnS is distributed with what state in steel, depending on the composition such as O, AL, C, Si in steel.MnS distribution 1. state has without using in the steel of AL deoxidations, in spherical, random distribution；2. divide on a small quantity using in the steel of AL deoxidations in fan-shaped Cloth is distributed along crystal boundary；3. plus AL is high, when residual AL is more in steel, in block random distribution；It is desirable that be MnS along crystal boundary or Fan-shaped is distributed, and to improve dislocation resistance, improves steel body intensity.

Before starting precipitation with most of precipitate after liquid phase disappearance, crystal grain, which has, is grown up, and crystal grain is grown up early Control, it can just ensure to refine the effect of initial grain, this is one of key means of refined crystalline strengthening.It can be seen from figure below Even if in the case where sulfur content is relatively low, MnS starts Precipitation Temperature as 1220 DEG C or so.Because Precipitation Temperature is higher, precipitate MnS is one of pinning particle most formed early in crystal boundary, therefore has very strong refined crystalline strengthening effect.

Shown in Fig. 6, MnS is complete, and solid solubility temperature is very high, is necessarily separated out in the cooling procedure of steel due to supersaturation.

In addition, in steel in the case of Mn abundances, MnC can be generated.MnS, MnO and MnC can separate out in crystal boundary, in boundary shape Into pinning particle, particle is smaller, and the effect of pinning crystal boundary is better.To prevent that Mn compounds are excessive in steel, promote growing up for crystal grain, In steel plus manganese is wanted to be less than 0.7%.

3 solution strengthening：

Solution strengthening is that alloying element is solid-solution in parent metal and causes the distortion of a certain degree of character so that alloy is strong Spend the phenomenon improved.Its mechanism is：When the elastic distortion in solid solution caused by the atomic radius of solute and solvent, with dislocation Between caused elastic interaction, have inhibition to moving dislocation on slide surface；Second, the segregation on skid wire Constraint and pinning effect of the solute atoms (KESHI gas mass) to dislocation.The concrete measure of solution strengthening is as follows in the present invention：

3-1 utilizes the characteristics of nickel element, realizes solution strengthening：

Elemental nickel melts molecular weight 58.69, atomic radius 1.62,1453 DEG C of fusing point, 2732 DEG C of boiling point, density 8.09.Nickel is made It can make steel that there is advanced mechanical performance for alloying element, you can to make steel that there is toughness, anti-corrosion acid-resisting, high magnetic conductivity, and make Crystal grain refinement improves quenching degree, increase hardness etc..

Invigoration effect of the nickel in steel belongs to solution strengthening.Nickel expands γ phase regions in steel, forms unlimited solid solution.In α Maxima solubility is 10% or so in iron.Do not form stable compound in steel, mainly exist in the form of solid solution, not shape Into carboritride.Although invigoration effect is medium, the effect for having refined ferrite crystal grain is served, under the same conditions, Improve the plasticity and toughness of steel, particularly low-temperature flexibility.

Found in experimental study, precipitated phase nickel AL, Ti element forms a kind of transition compound Ni₃(AL, Ti), form a kind of With the γ ' phases with face-centred cubic structure, separated out after 760 DEG C of timeliness in crystal boundary.This Ni₃(AL, Ti)-γ ' phases, no matter In crystals or crystal boundary, very big dislocation resistance can be all produced, has and strengthens effect well.

3-2 utilizes the characteristics of chromium, realizes the reinforcing based on solid solution：

The atomic weight of chromium is 51.996,1857 DEG C of simple substance chromium fusing point, 2672 DEG C of boiling point, density 7.2g/cm3.Chromium is alloy One of most widely used element in steel production.Chromium can strengthen the mechanical performance and wearability of steel, increase quenching degree and the quenching of steel Non-deformability afterwards, strengthen elasticity, diamagnetism, corrosion resistance and the heat resistance of steel.

Form of the chromium in steel is more complicated, in addition to being partly present in iron solid solution, it is also possible to form carbide (FeCr) 3C, Cr3C2, Cr7C3, Cr23C6 etc.), nitride (CrN, Cr2N), sulfide (CrS, FeSCr2S3), oxide [CrxOy, (Fe, Mn) OCr2O3] and metallic iron compound (FeCr) and silicide (Cr3Si etc.).Wherein with the carbonization of chromium Thing and nitride state are relatively stable.

Chromium forms continuous solid solution with iron, reduces austenite phase field city.Chromium forms a variety of carbide with carbon, affine with carbon Power is more than iron and manganese and can form intermetallic compound σ phases (FeCr) with iron less than chromium such as tungsten, molybdenums.

Chromium is middle carbide, and the chromium part displacement iron in steel forms alloyed cementite, and it is stable to improve its Property；A part is dissolved in ferrite, is produced solution strengthening, is improved ferritic intensity and hardness.

C_rInfinitely it is dissolved in α iron, maxima solubility is 12.5% in γ iron.The alloy of chromium is likely to form when content is low Cementite (Fe, Cr) 3C, and with the increase of chromium content, the carbide in steel is progressively changed into Cr23C6 and Cr7C3.Because chromium is in Austria Diffusion velocity in family name's body is smaller, hinders Carbon diffusion in addition, thus can improve the stability of austenite.Chromium is also because reducing phase Temperature, so as to make carbide be separated out in lower temperature, make tissue and carbide refinement.In the higher steel alloy of chromium content Chromium has the trend for making the scattered isolated distribution of carbide.

Cr₂₃C₆It is solid-solution in the matrix of steel, forms orderly γ ' phases, γ ' is in mutually face-centred cubic structure, is had very high Atomic binding forces, have very strong solution strengthening effect in crystal, even if at relatively high temperatures (≤760 DEG C), dislocation is cut Cut and pass through γ ' phase resistances, it is much bigger more than the other parts of matrix, therefore have good solid solution strengthening effect to steel, can be simultaneously Obtain high tensile strength and yield strength.

4 function reparations：

A variety of alloying elements are employed herein, the effect pros and cons that each alloying element is played coexist.To maximize favourable factors and minimize unfavourable ones, The whole synthesis performance of steel is improved, it is necessary to which the side effect to alloy part element carries out necessary reparation.

4-1 adds Ni elements, repairs " copper brittleness " because being brought using copper：

It is one of essential element to control Cu in brilliant steel, and to go the side effect of copper removal, Ni (the 1/ of Cu contents is added in steel More than 3) when, the generation of copper brittleness can be avoided.The solid solution that nickel is formed in steel, the effect of fining ferrite grains is served, The plasticity and toughness of steel are improved simultaneously.

Be elements are added in 4-2 steel：

Using BeO in steel the trickle particle of disperse characteristic, improve yield strength under identical stiffness conditions.

4-3 utilizes the combined characteristic for controlling wafer element：

The performances such as the comprehensive ductility for improving steel body, toughness, corrosion resistance, weldability, creep resistance, reach comprehensive repair Purpose.

The above-described embodiments are merely illustrative of preferred embodiments of the present invention, not to the guarantor of the present invention Shield scope is defined, all using listed control wafer element is added in molten steel under the premise of design spirit of the present invention is not departed from, and is increased Add Enhancing Nucleation Density to refine the method for initial grain, each fall within the scope of this patent；The listed control wafer element of all uses, in liquid phase After disappearance for prevent crystal grain grow up (or crystal stock) utilize pinning suites of measure, form pinning phase, continuous limitation crystal grain chi in crystal boundary It is very little, with crystal grain thinning, the method for the combination property for improving steel, each fall within the scope of this patent.

Claims (2)

1. A kind of 1. method for preparing unimach using the multiple brilliant means of control, it is characterised in that in steel-making terminal and deslagging behaviour After work, added into molten steel and control brilliant agent, the percentage by weight of the brilliant agent composition of control is：Cu 0.6-1.6, Sn 0.002- 0.01, Zn 0.001-0.05, Pb 0.002-0.01, Ni 0.2-0.6, Mn 0.1-0.7, Ti 0.02-0.1, Al 0.02- 0.2, Cr 0.2-0.5, N 0.008-0.05, Be 0.001-0.05, the rest is iron and impurity.
2. A kind of 2. method for preparing unimach using the multiple brilliant means of control according to claim 1, it is characterised in that It is target molten steel to add caused molten steel after controlling brilliant agent, and target molten steel carries out normal continuous casting through conticaster, temperature be 850~ Water quick cooling, 25~80 DEG C/min of intensity of cooling are required between 650 DEG C.