CN103729511A - Method for predicating ingredient segregation degrees in casting process of complex-structure casting - Google Patents

Abstract

The invention provides a method for predicating the ingredient segregation degrees in the casting process of a complex-structure casting. The method includes the steps of (1) calculating to obtain thermophysical parameters of alloy through a thermophysical parameter calculating module of commercialized JMatPro software, (2) carrying out analogue simulation on the casting filling and solidifying processes of the complex-structure casting through ProCAST finite element software, and obtaining temperature field data of various parts of the casting, (3) calculating secondary dendrite arm spacing values of the structural parts of the casting through a secondary dendrite arm spacing calculating module built in the ProCAST software, and (4) calculating MSIs of the structural parts of the complex-structure casting, and judging the micro-segregation degrees of the structural parts of the casting according to the MSIs. According to the method, the finite element software and thermodynamic calculation software are used, the casting practice is combined, the micro-segregation degrees of solute elements of the structural parts of the complex-structure casting are effectively predicted, and the application range is wide.

Description

The Forecasting Methodology of component segregation degree in a kind of Complicated structure casting casting process

Technical field

The present invention relates to steel industry component segregation analysis technical field, particularly, relate to the Forecasting Methodology of component segregation degree in a kind of Complicated structure casting casting process.

Background technology

Component segregation is aluminium alloy intrinsic characteristic while solidifying.When the solubleness of solute element in solid phase is less than its solubleness in liquid phase, solid-liquid interface will be got rid of solute in liquid phase; And when the solubleness of solute element in solid phase is greater than the solubleness in liquid phase, solute, from liquid phase to solid-state diffusion, will cause solid-liquid interface forward position to occur the poor district of solute.This reallocation due to solute in alloy graining process causes the uneven components after alloy graining, is component segregation.Conventionally, the solubleness of solute element in liquid phase is than high in solid phase, so solute has the solidifying phase of disengaging and be pulled to the tendency in the liquid of forward position, and end is solidified the grown dendritic arm of liquid that part is rich in solute and cut apart, forming component segregation region.Component segregation is one of major defect of foundry goods, reduces alloy solid solution strengthening effect, and meanwhile, the low melting point precipitated phase that interdendritic forms easily becomes formation of crack in the welding process of foundry goods, reduces mechanical property and the welding performance of foundry goods.

Known according to classical solidification theory, under general alloy graining condition, the solute redistribution behavior of micro-scale and the microsegregation of generation not only depend on that the physical parameter of alloy is (as solid-state diffusion coefficient D _s, Liquid Diffusion Coefficient D _l, solute distribution coefficient k) and external process condition as freezing rate V(or local solidification time t _f), thermograde G, but also closely related with factors such as the growth pattern of dendrite, dendrite morphologies.

The simplest analytic model is Lever analytic model and the Scheil analytic model under partial balancing's curing condition, and other is all correction type analytic model.Consideration based on back diffusion, lever model and Scheil model are two kinds of limiting cases.

Lever model is a kind of equilibrium freezing model, supposes that solute is in all fully diffusions of solid-liquid two-phase,

C _L＝C ₀[1-(1-k)f _s] ^-1①

Formula 1. in, C _lfor liquid phase solute concentration, C ₀for initial solute concentration, f _sfor fraction solid, k is solute distribution coefficient.

Scheil model is also referred to as non-equilibrium lever model, wherein suppose solute in liquid phase fully diffusion and solid phase without diffusion, in model, do not consider that forming core is excessively cold, the formation of dendritic arm alligatoring, macroscopic material transmission and pore,

C _L＝C ₀(1-f _s) ^(k-1)②

Obviously, as fraction solid f _s=1 o'clock C _ltrend towards infinity, so Scheil model can not accurately calculate to final solute concentration.

H.D.Brody & M.C, Flemings considers the antidiffusion of solute element in process of setting, has

C _L＝C ₀[1-(1-2αk)f _s] ^{(k-1)/(1-2αk)}③

Formula 3. in, α is nondimensional solute invasin, or claims nondimensional diffusion time (Fourier number), it has represented the diffusion boundary layer thickness δ in solid phase _swith the proportionate relationship of system dimension L, can be expressed as:

$\mathrm{\α}=\frac{D_s{t}_f}{L^2}$ ④

When α=0 is nothing diffusion in solid phase, 3. formula is reduced to Scheil model;

When α=0.5,3. formula is reduced to lever model.

The people such as W.Kurz revise α value, propose with α ' replacement α,

${\mathrm{\α}}^{\′}=2\mathrm{\α}[1-\exp (-\frac{1}{\mathrm{\α}})]-\exp (-\frac{1}{2\mathrm{\α}})$ ⑤

Although scholars have studied most advanced and sophisticated cold, the impact that the solute assigning processs such as cold-peace coagulated volume variation are crossed at eutectic interface of coagulating property, the solid-back diffusion in process of setting, the limited diffusion of liquid, dendritic arm alligatoring, dendrite that the alloying component of multicomponent alloy changes energetically with excessivelying in recent years, set up in some process of setting solute concentration with microsegregation analytic model and the numerical model of fraction solid increase.But the microsegregation model that existing solute distributes is all based upon the variation that in research process of setting, solute concentration increases with fraction solid, can only represent interfacial concentration

with fraction solid f _sfuntcional relationship, can not determine accordingly the component distributing of final solid phase, and must consider this dynamic parameter of fraction solid, and can not judge for a large and complex structure part different structure position, by the segregation degree under many factors acting in conjunction, cannot instruct the Foundry Production of large and complex structure foundry goods.

Summary of the invention

For defect of the prior art, the Forecasting Methodology that the object of this invention is to provide component segregation degree in a kind of Complicated structure casting casting process, this Forecasting Methodology can predict that parts with complex structures different structure position, in the microsegregation degree of different curing conditions, has directive significance to the Foundry Production of large and complex structure foundry goods.

For realizing above object, the invention provides the Forecasting Methodology of component segregation degree in a kind of Complicated structure casting casting process, the method comprises:

(1) obtain calculating thermal physical property parameter

Utilize the thermophysical parameter computing module of commercialization JMatPro software to calculate the thermal physical property parameter that obtains alloy, parameter comprises solute balance partition factor k, Liquid Diffusion Coefficient D _l, solid-state diffusion coefficient D _s, alloy initial solidification temperature T _l, eutectic reaction temperature T _s;

(2) obtain the temperature field data at each position of foundry goods

Application ProCAST finite element software carries out analogue simulation to the casting filling of Complicated structure casting, process of setting, obtains the temperature field data at each position of foundry goods, and data comprise setting rate V, the local setting time t of molten metal _f; Or local setting time t _f, the setting rate V method that also can combine with sunykatuib analysis by precision-investment casting obtains.

(3) obtain the secondary dendrite arm spacing λ of each structure position place of foundry goods ₂

Utilize secondary dendrite arm spacing computing module that ProCAST software carries to calculate the secondary dendrite arm spacing λ of each structure position of foundry goods ₂; Or, secondary dendrite arm spacing λ ₂the method that also can combine with sunykatuib analysis by precision-investment casting is obtained.

(4) calculate each structure position place segregation index M of foundry goods SI value

The Solidification Parameters obtaining from ProCAST: the setting rate V of molten metal, local setting time t _f, secondary dendrite arm spacing λ ₂, and the thermophysical parameter of JMatPro calculating: solute balance partition factor k, Liquid Diffusion Coefficient D _l, solid-state diffusion coefficient D _sin substitution microsegregation deciding degree index M SI formula, and by the ViewCAST module of ProCAST, calculate the segregation index M SI of each structure position of Complicated structure casting, according to the size of the segregation index M SI value of each structure position of Complicated structure casting, judge the microsegregation degree of each structure position of foundry goods: SI is larger for segregation index M, microsegregation is more serious, solidifies the interdendritic precipitated phase content forming latter stage just higher; Wherein:

$\mathrm{MSI}=\frac{{\mathrm{Pe}}_L}{\mathrm{kF}{o}_S}=\frac{1}{8}\·\frac{1}{2k{D}_L{D}_S}\frac{V{\mathrm{\λ}}_2^3}{t_f}=\frac{1}{8}\·A\·\frac{V{\mathrm{\λ}}_2^3}{t_f},a=\frac{1}{2k{D}_L{D}_S}$

In formula: Pe _lfor dimensionless solute P é let number, characterize in the liquid phase of solid-liquid interface forward position by the determined driving force of solute degree of supersaturation; Fo _sfor dimensionless Fourier number, also become the solid-back diffusion factor; K is solute balance partition factor; D _lfor Liquid Diffusion Coefficient; D _sfor solid-state diffusion coefficient; V is setting rate; L is feature diffusion length; t _ffor local solidification time;

for comprising the physical parameter of alloy material, depend on the selection of material, for the different structure position on Same Part, A can think constant.

Preferably, in step (2), secondary dendrite arm spacing λ ₂computing formula be

λ ₂＝(Mt _f) ^1/3

Wherein:

$M=166\·\frac{{\mathrm{\ΓD}}_l\ln (C_{\mathrm{eut}}/C_0)}{m(1-k)(C_0-C_{\mathrm{eut}})}$

In formula, Γ is Gibbs-Thomson coefficient, C ₀for initial solute concentration, C _eutliquid phase solute concentration while there is eutectic reaction latter stage for solidifying, m is alloy liquid phase line slope, M is for following the relevant parameter of material.

More preferably, M value is calculated by each parameter from Thermodynamic Calculation Software JMatPro or list of references L.NASTAC.NUMERICAL MODELING OF SOLIDIFICATION MORPHOLOGIES AND SEGREGATION PATTERNS IN CAST DENDRITIC ALLOYS[J] .Acta mater.Vol.17.pp:4253-4262.1999. acquisition.

Preferably, at ProCAST, calculate in panel, according to different alloys, input corresponding initial solidification temperature T _l, eutectic reaction temperature T _sand the M value calculating, can calculate the secondary dendrite arm spacing value λ of each structure position of foundry goods ₂.

Compared with prior art, the present invention has following beneficial effect:

The present invention, by finite element software ProCAST and Thermodynamic Calculation Software JMatPro, can effectively predict the microsegregation degree of the solute element of each structure position of Complicated structure casting; By the application of the inventive method, not only can dissect foundry goods and can predict the segregation degree of a certain solute element of each structure position of foundry goods, for optimizing and revising casting technique and Technology for Heating Processing provides foundation, and the method can be to other solute element segregation degree of multicomponent alloy prediction, applied range.

Accompanying drawing explanation

By reading the detailed description of non-limiting example being done with reference to the following drawings, it is more obvious that other features, objects and advantages of the present invention will become:

Fig. 1 is one embodiment of the invention Casting Three-dimensional illustraton of model;

Fig. 2 is one embodiment of the invention foundry goods pictorial diagram;

Fig. 3 is one embodiment of the invention MSI segregation exponential forecasting result and Laves phase content experimental result comparison diagram.

Embodiment

Below in conjunction with specific embodiment, the present invention is described in detail.Following examples will contribute to those skilled in the art further to understand the present invention, but not limit in any form the present invention.It should be pointed out that to those skilled in the art, without departing from the inventive concept of the premise, can also make some distortion and improvement.These all belong to protection scope of the present invention.

In the present embodiment, microsegregation deciding degree index M SI's (Micro-segregation Index) determines based on following consideration.

Theoretical by means of widely used Buckingham π non-dimension analysis in mathematical physics, solute in process of setting is distributed and carries out non-dimension analysis.The research of diffusion flux based on solid-liquid interface both sides liquid phase and solid phase solute atoms, the behavior that the antidiffusion alloy that the present invention considers the limited diffusion of solid-liquid interface forward position liquid phase solute and solid phase solute solidifies solute redistribution is studied.The employing P é let number of solid-liquid interface forward position solute diffusion represents, P é let number is dendrite end radius of curvature R and liquid phase solute Equivalent Boundary layer thickness δ _cratio, liquid phase solute Equivalent Boundary layer thickness δ _c(δ _c=2D _l/ V) represent that in diffusion length, contained whole solutes equal the contained solute total amount of infinite boundary layer.Solute concentration gradient due to dendrite end, can see approx it is the solute concentration gradient in the spheroid forward position of growing up, according to the way that solves in diffusion field around the globular crystal of growing, if only consider radial diffusion, the globular crystal of growing boundary layer thickness around equals the radius of ball, and the solute diffusion length L of dendrite end is approximately equal to the radius R of ball.Therefore, P é let number can be expressed as

${\mathrm{Pe}}_L=\frac{\mathrm{VL}}{2D_L}---\left(7\right)$

P é let number has characterized in the liquid phase of solid-liquid interface forward position by the determined driving force of solute degree of supersaturation.

Owing to usually there is eutectic in actual process of setting, liquid concentration can not continue to increase, and in order to describe truly the component distributing of solidification end, must consider the antidiffusion of solute atoms in solid phase.According to the principle of mass conservation, in solid phase, the speed degree of solute atoms antidiffusion depends on dimensionless group α, also referred to as Fo _s, it has characterized the ability of solute atoms antidiffusion in solid phase.

${\mathrm{Fo}}_S=\mathrm{\α}=\frac{D_S{t}_f}{L^2}---\left(8\right)$

According to the solute mass conservation, the segregation index M SI (Micro-segregation Index) that characterizes the solute segregation degree in process of setting can be expressed as

$\mathrm{MSI}=\frac{{\mathrm{Pe}}_L}{k{\mathrm{Fo}}_S}---\left(9\right)$

Wherein ${\mathrm{Pe}}_L=\frac{\mathrm{VL}}{2D_L},{\mathrm{Fo}}_s=\frac{D_S{t}_f}{L^2},$ Substitution (9)

$\mathrm{MSI}=\frac{{\mathrm{Pe}}_L}{k{\mathrm{Fo}}_S}=\frac{1}{2K{D}_L{D}_S}\frac{{\mathrm{VL}}^3}{t_f}=A\·\frac{{\mathrm{VL}}^3}{t_f}---\left(10\right)$

Wherein

be the physical parameter that comprises alloy material, depend on the selection of material.For the different structure position on Same Part, A can think constant.As seen from formula (10), the segregation index M SI value of the judgement microsegregation degree that the present invention proposes size, not only follows the thermal physical property parameter solute balance partition factor k of alloy, Liquid Diffusion Coefficient D _l, solid-state diffusion coefficient D _sbe correlated with, and also have local solidification condition setting rate V, feature diffusion length L and the local solidification time t of alloy _frelevant.

For general casting process, dendrite is to wait axle dendrite mode to grow.Now, secondary dendrite arm spacing λ ₂it is the characteristic length of solute diffusion.Therefore, half of getting secondary dendrite arm spacing is diffusion length,

Substitution formula (10)

$\mathrm{MSI}=\frac{{\mathrm{Pe}}_L}{\mathrm{kF}{o}_S}=\frac{1}{8}\·\frac{1}{2k{D}_L{D}_S}\frac{V{\mathrm{\λ}}_2^3}{t_f}=\frac{1}{8}\·A\·\frac{V{\mathrm{\λ}}_2^3}{t_f},a=\frac{1}{2k{D}_L{D}_S}---\left(11\right)$

Be below the present invention's one application the present embodiment:

The present embodiment provides the Forecasting Methodology of component segregation degree in a kind of Complicated structure casting casting process, and the K4169 nickel base superalloy large-scale complex thin-wall foundry goods of casting is carried out to the prediction of microsegregation degree.The large-area thin plate that this casting design contains different-thickness, variable cross section, the structures such as cylinder.As shown in Figure 1, the foundry goods pictorial diagram that cast obtains as shown in Figure 2 for Casting Three-dimensional illustraton of model.The alloying element adding due to K4169 nickel base superalloy is many, and alloying level is high, and solidification temperature range is wide, and the solidifying segregation of alloying element is serious.Microsegregation is one of major defect of K4169 nickel base superalloy foundry goods, and the mechanical property of foundry goods, welding performance and processing characteristics are had to important impact.In K4169 nickel base superalloy casting solidification process, the solubleness of Nb solute atoms in matrix is little, in process of setting, solid-liquid interface will be got rid of a large amount of Nb solute atomss to liquid phase, while being cooled to 1180 ℃, there is γ+Laves eutectic reaction, in interdendritic, form Laves phase.If due to alloy graining process component segregation, solidify the Laves phase amount forming latter stage more, no matter their form and how distributing, because Laves has fixed the intensified elements such as a large amount of Nb in mutually, thereby reduce solid solution strengthening effect.Meanwhile, also reduced hardening constituent γ ' or γ " quantity, weakened precipitation strengthening effect, cause alloy mechanical property to worsen.Therefore, eliminate solute element Nb segregation and Laves is a gordian technique difficult problem for K4169 nickel base superalloy castings production mutually always.

(1) obtain calculating thermal physical property parameter

By JMatPro software, K4169 alloy is carried out to PHASE DIAGRAM CALCULATION, and in conjunction with list of references L.NASTAC.NUMERICAL MODELING OF SOLIDIFICATION MORPHOLOGIES AND SEGREGATION PATTERNS IN CAST DENDRITIC ALLOYS[J] .Acta mater.Vol.17.pp:4253-4262.1999. obtains and calculates each thermophysical parameter used, and each parameter is as follows:

Γ=3.65×10 ^-7(km)，k _Nb=0.48，D _l,Nb=3×10 ^-9(m ²s ^-1)，D _s,Nb=2.82×10 ^-13(m ²s ^-1)，C _0,Nb=4.316(wt.pct)，C _eut,Nb=19.1(wt.pct)，m _l=-10.9，T _l=1360℃，T _s=1180℃；

(2) obtain the temperature field data at each position of foundry goods

Application ProCAST finite element software carries out analogue simulation to casting filling, the process of setting of foundry goods as shown in Figure 1, obtains the temperature field data at each position of foundry goods, as the local setting time t of molten metal _f, setting rate V;

Or local setting time t _f, the setting rate V method that also can combine with sunykatuib analysis by precision-investment casting obtains.For fixing K4169 alloy, the cast model based on fixing and full form casting process condition, carry out actual investment cast and obtain foundry goods.In casting process, at foundry goods feature structure position, place in advance high temperature resistance tungsten-rhenium thermal couple, measure in real time the cooling curve of casting process molten metal.On the one hand, in conjunction with JMatPro software, K4169 alloy is carried out the beginning temperature of solidification T of PHASE DIAGRAM CALCULATION acquisition _land solidify end temp T _s, can obtain local setting time t _fwith cooling velocity R, local setting time t _fbe molten metal and start to solidify the time of experiencing to solidifying end, and cooling velocity R is by formula R=-(T _s-T _l)/t _fobtain.On the other hand, in conjunction with the equidistant position of the branched thermopair of layout, can obtain the thermograde G of appointed part, then according to formula R=-GV, can obtain the setting rate V of appointed part molten metal.Finally the actual measured value of thermopair and the analogue value are compared, if both are identical, think the local setting time t that this simulation obtains _f, setting rate V is the local setting time t of foundry goods _f, setting rate V, if instead two not identical, adjustment model boundary condition arranges, then simulates, until both are identical.

(3) obtain the secondary dendrite arm spacing λ of each structure position place of foundry goods ₂

Utilize secondary dendrite arm spacing computing module that ProCAST software carries to calculate the λ of each structure position of foundry goods ₂value.The M value that obtains as calculated K4169 alloy is 19.43(um ³s ^-1); Secondary dendrite arm spacing λ ₂computing formula be

λ ₂＝(Mt _f) ^1/3 （12）

Wherein:

$M=166\·\frac{{\mathrm{\ΓD}}_l\ln (C_{\mathrm{eut}}/C_0)}{m(1-k)(C_0-C_{\mathrm{eut}})}---\left(13\right)$

In formula (13), Γ is Gibbs-Thomson coefficient, C ₀for initial solute concentration, C _eutliquid phase solute concentration while there is eutectic reaction latter stage for solidifying, m is alloy liquid phase line slope, M is for following the relevant parameter of material.At ProCAST, calculate in panel, according to different alloys, input corresponding initial solidification temperature T _l, eutectic reaction temperature T _s, and the M value calculating according to formula (13), can calculate the secondary dendrite arm spacing λ of each structure position of foundry goods ₂value.

Or, secondary dendrite arm spacing λ ₂the method that also can combine with sunykatuib analysis by precision-investment casting is obtained.For fixing K4169 alloy, the cast model based on fixing and full form casting process condition, carry out actual investment cast and obtain foundry goods, and foundry goods is carried out to subdivision, by each structure position intercepting metallographic specimen, adopts 10gCuCl ₂the mix reagent of+100 alcohol+100ml hydrochloric acid slightly corrodes, and then carries out metallographic observation statistics secondary dendrite arm spacing λ ₂mean value, the actual secondary dendrite arm spacing λ finally subdivision foundry goods being obtained ₂value and the analogue value contrast, if both identical or errors are in 5%, think that this analog result is the secondary dendrite arm spacing λ of foundry goods ₂value, if instead two not identical, adjustment model boundary condition arranges, then simulates, until both are identical or in error range.

(4) calculate each structure position place segregation index M of foundry goods SI value

The temperature field data of obtaining from ProCAST: the setting rate V of molten metal, local setting time t _f, secondary dendrite arm spacing λ ₂, and the thermophysical parameter of the calculating of JMatPro: solute balance partition factor k, Liquid Diffusion Coefficient D _l, solid-state diffusion coefficient D _s, in substitution formula (11), and by the ViewCAST module of ProCAST, calculate the MSI segregation index of each structure position of Complicated structure casting; According to the size of each structure position MSI segregation index, judge the microsegregation degree of each structure position of foundry goods; Wherein:

$\mathrm{MSI}=\frac{{\mathrm{Pe}}_L}{\mathrm{kF}{o}_S}=\frac{1}{8}\·\frac{1}{2k{D}_L{D}_S}\frac{V{\mathrm{\λ}}_2^3}{t_f}=\frac{1}{8}\·A\·\frac{V{\mathrm{\λ}}_2^3}{t_f},a=\frac{1}{2k{D}_L{D}_S}---\left(11\right)$

In formula (11): Pe _lfor dimensionless solute P é let number, characterize in the liquid phase of solid-liquid interface forward position by the determined driving force of solute degree of supersaturation; Fo _sfor dimensionless Fourier number, also become the solid-back diffusion factor; K is solute balance partition factor; D _lfor Liquid Diffusion Coefficient; D _sfor solid-state diffusion coefficient; V is setting rate; L is feature diffusion length; t _ffor local solidification time.

Predict the outcome and obtain the subdivision result contrast (comparing result is as shown in Figure 3) of foundry goods with investment cast, visible, predict the outcome and coincide with subdivision result, segregation index is larger, and microsegregation is more serious, and the interdendritic Laves phase content that solidifies formation in latter stage is just higher.

The present invention, by finite element software ProCAST and Thermodynamic Calculation Software JMatPro, in conjunction with foundry practice, can effectively predict the microsegregation degree of the solute element of each structure position of Complicated structure casting; By the application of the inventive method, not only can dissect foundry goods and can predict the segregation degree of a certain solute element of each structure position of foundry goods, for optimizing and revising casting technique and Technology for Heating Processing provides foundation, and the method can be to other solute element segregation degree of multicomponent alloy prediction, applied range.

Above specific embodiments of the invention are described.It will be appreciated that, the present invention is not limited to above-mentioned specific implementations, and those skilled in the art can make various distortion or modification within the scope of the claims, and this does not affect flesh and blood of the present invention.

Claims (6)

1. a Forecasting Methodology for component segregation degree in Complicated structure casting casting process, is characterized in that, the method comprises the steps:

(1) obtain calculating thermal physical property parameter

The thermal physical property parameter that utilizes the thermophysical parameter computing module acquisition alloy of commercialization JMatPro software, parameter comprises solute balance partition factor k, Liquid Diffusion Coefficient D _l, solid-state diffusion coefficient D _s, alloy initial solidification temperature T _l, eutectic reaction temperature T _s;

(2) obtain the temperature field data at each position of foundry goods

Application ProCAST finite element software carries out analogue simulation to the casting filling of Complicated structure casting, process of setting, obtains the temperature field data at each position of foundry goods, and data comprise setting rate V, the local setting time t of molten metal _f; Or local setting time t _f, the method that combines with sunykatuib analysis by precision-investment casting of setting rate V obtains;

(3) obtain the secondary dendrite arm spacing λ of each structure position place of foundry goods ₂

Utilize secondary dendrite arm spacing computing module that ProCAST finite element software carries to calculate the secondary dendrite arm spacing λ of each structure position of foundry goods ₂; Or secondary dendrite arm spacing λ ₂the method combining with sunykatuib analysis by precision-investment casting is obtained;

(4) calculate each structure position place segregation index M of foundry goods SI value

The Solidification Parameters obtaining from ProCAST finite element software: the setting rate V of molten metal, local setting time t _f, secondary dendrite arm spacing λ ₂, and the thermophysical parameter that obtains of JMatPro software: solute balance partition factor k, Liquid Diffusion Coefficient D _l, solid-state diffusion coefficient D _sin substitution microsegregation deciding degree index M SI formula, and by the ViewCAST module of ProCAST finite element software, calculate the segregation index M SI of each structure position of Complicated structure casting, according to the size of the segregation index M SI value of each structure position of Complicated structure casting, judge the microsegregation degree of each structure position of foundry goods: SI is larger for segregation index M, microsegregation is more serious, solidifies the interdendritic precipitated phase content forming latter stage just higher; Wherein:

$\mathrm{MSI}=\frac{{\mathrm{Pe}}_L}{\mathrm{kF}{o}_S}=\frac{1}{8}\·\frac{1}{2k{D}_L{D}_S}\frac{V{\mathrm{\λ}}_2^3}{t_f}=\frac{1}{8}\·A\·\frac{V{\mathrm{\λ}}_2^3}{t_f},a=\frac{1}{2k{D}_L{D}_S}$

In formula: Pe _lfor dimensionless solute P é let number, characterize in the liquid phase of solid-liquid interface forward position by the determined driving force of solute degree of supersaturation; Fo _sfor dimensionless Fourier number, also become the solid-back diffusion factor; K is solute balance partition factor; D _lfor Liquid Diffusion Coefficient; D _sfor solid-state diffusion coefficient; V is setting rate; L is feature diffusion length; t _ffor local solidification time;

for comprising the physical parameter of alloy material, depend on the selection of material, for the different structure position on Same Part, A thinks constant.

2. the Forecasting Methodology of component segregation degree in a kind of Complicated structure casting casting process according to claim 1, is characterized in that described local setting time t _f, the method that combines with sunykatuib analysis by precision-investment casting of setting rate V obtains, be specially: for fixing K4169 alloy, cast model based on fixing and casting technique condition, carry out actual casting and obtain foundry goods, in casting process, at foundry goods feature structure position, place in advance high temperature resisting thermocouple, measure in real time the cooling curve of casting process molten metal, on the one hand, in conjunction with JMatPro software, K4169 alloy is carried out to phasor and obtain beginning temperature of solidification T _land solidify end temp T _s, can obtain local setting time t _fwith cooling velocity R, wherein: local setting time t _fbe molten metal and start to solidify the time of experiencing to solidifying end, and cooling velocity R is by formula R=-(T _s-T _l)/t _fobtain; On the other hand, in conjunction with the position of branched thermopair, obtain the thermograde G of appointed part, then according to formula R=-GV, obtain the setting rate V of appointed part molten metal;

Finally the actual measured value of thermopair and the analogue value are compared, if both are identical, think the local setting time t that this simulation obtains _f, setting rate V is the local setting time t of foundry goods _f, setting rate V, if instead two not identical, adjustment model boundary condition arranges, then simulates, until both are identical.

3. the Forecasting Methodology of component segregation degree in a kind of Complicated structure casting casting process according to claim 1, is characterized in that described secondary dendrite arm spacing λ ₂the method combining with sunykatuib analysis by precision-investment casting is obtained, be specially: for fixing K4169 alloy, cast model based on fixing and full form casting process condition, carry out actual investment cast and obtain foundry goods, foundry goods is carried out to subdivision, by each structure position intercepting metallographic specimen, adopt 10gCuCl ₂the mix reagent of+100 alcohol+100ml hydrochloric acid slightly corrodes, and then carries out metallographic observation statistics secondary dendrite arm spacing λ ₂mean value, the actual secondary dendrite arm spacing λ finally subdivision foundry goods being obtained ₂value and the analogue value contrast, if both identical or errors are in 5%, think that this analog result is the secondary dendrite arm spacing λ of foundry goods ₂value, if instead two not identical, adjustment model boundary condition arranges, then simulates, until both are identical or in error range.

4. the Forecasting Methodology of component segregation degree in a kind of Complicated structure casting casting process according to claim 3, is characterized in that, in step (2), and secondary dendrite arm spacing λ ₂computing formula be

λ ₂＝(Mt _f) ^1/3

Wherein:

$M=166\·\frac{{\mathrm{\ΓD}}_l\ln (C_{\mathrm{eut}}/C_0)}{m(1-k)(C_0-C_{\mathrm{eut}})}$

In formula, Γ is Gibbs-Thomson coefficient, C ₀for initial solute concentration, C _eutliquid phase solute concentration while there is eutectic reaction latter stage for solidifying, m is alloy liquid phase line slope, M is for following the relevant parameter of material.

5. the Forecasting Methodology of component segregation degree in a kind of Complicated structure casting casting process according to claim 4, it is characterized in that, M value is calculated by each parameter from Thermodynamic Calculation Software JMatPro or list of references L.NASTAC.NUMERICAL MODELING OF SOLIDIFICATION MORPHOLOGIES AND SEGREGATION PATTERNS IN CAST DENDRITIC ALLOYS[J] .Acta mater.Vol.17.pp:4253-4262.1999. acquisition.

6. according to the Forecasting Methodology of component segregation degree in a kind of Complicated structure casting casting process described in claim 1-5 any one, it is characterized in that, at ProCAST, calculate in panel, according to different alloys, input corresponding initial solidification temperature T _l, eutectic reaction temperature T _sand the M value calculating, can calculate the secondary dendrite arm spacing value λ of each structure position of foundry goods ₂.

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