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1Copyright © ESI Group, 2006. All rights reserved.

微观组织设置教程

[email protected]

010-65544907ext243

曹栋良ESI中国

mailto:[email protected]


综述

Introduction

Set up of a Micro model

What’s new ?

Results interpretation

Guidelines Calibration of Run Parameters (SGI)Porosity

Microstructure and properties


介绍

Micro-模块可以计算得到基于合金的化学成分的各种微观组织结果,在凝固过程中能生成多种相

包括枝晶尺寸、枝晶间距和各种相的分数铸铁: 石墨化膨胀对缩松的影响机械性能

Fe-基: 布氏硬度其他基于设置的结果

与合金的计算材料热物性相关联

thermodynamic databases (Computherm)


Microstructure – 设置

按照通常要求设置热边界条件

计算材料热物性

在球铁(SGI)计算时别忘加入Mg元素!


run parameter MICRO 设置成1

选择合金种类 (推荐采用默认值)



形核参数 (枝晶)

undercooling最大形核密度Number of nuclei / unit volume

形核过冷度

Critical undercooling

标准方差

Transition undercooling



形核长大参数(eutectic共析钢)

Eutectic Growth



默认值

形核参数 (material properties and may depend upon the metal treatment)



Microstructure – Coupled/Uncoupled

计算慢结果更精确小步长

计算快结果精度一般需要控制时间步长


uncoupled

coupled

石墨球半径计算结果




uncoupled

coupled

铁素体分数


Microstructure – 结果

合金成分不同,

输出结果不同!


Microstructure - Iron and Steel

CE= 4.1 (Hypo-eutectic SGI)

MICRO Output

Automatically computed

钢铁

亚共析过共析


Microstructure – Iron and Steel

碳当量(CE) : CE = %C +%Si/3

Steel if CE ≤2

CE > 2, Mg added SGI(has to be added in the chemicalcomposition in the thermo-dynamic database)

Iron if CE > 2

GRAPHITE, MOLDRIG, MGTREAT


Microstructure – Iron and Steel

Example : hypo-eutectic Nodular Cast Iron:

Solidification sequence Primary austeniteEutectic solidification

Slow cooling : stable eutectic (Graphite+Austenite)“Fraction of eutectic”

Fast Cooling : metastable eutectic (Fe3C + Austenite, called ledeburite)

“Fraction of metastable phase”

Cooling and Eutectoïd transformation (720°C)Austenite is transformed into Ferrite (stable) and/or Pearlite(metastable)Slow cooling : Ferrite formation is favorableFast cooling : Pearlite formation is favorable


Microstructure – 铸铁

Default valuesDuctile Iron = SGI, Nodular Cast IronGray Iron

“Porosity related”GRAPHITE, FADING, MGTREAT

“Microstructure related”Dendrites : EQNMAX, EQSTD, EQUNDER

Eutectic : EUNUC, EUPOWER, EUGROW

+ MOLDRIG(Thermal R.P !)


Microstructure – 铸铁

Process-相关的运行参数R.PGRAPHITE :RP/Micro

1, High graphitization 铸件膨胀率大0, No graphitization 铸件无膨胀发生

MOLDRIG :RP/Thermal1, Mold totally rigid 铸型刚性无变形石墨膨胀可以很好的再次补缩;0, Soft mold 铸件膨胀引起铸型变形无补缩现象发生

MGTREAT and FADING :RP/MicroSGI is obtained by a Mg inoculation of the melt当FADING激活后, 石墨孕育和膨胀效应会随时间衰退.可以考虑孕育时间 : MGTREAT = time interval between inoculation of melt and start of the calculation孕育时间

Effect on porosity

Effect on porosity

Effect on porosity


Microstructure – Fading Model

“Fading Effect”Mg在合金中孕育处理. 石墨化膨胀效应会随着Mg的含量以及时间衰退 (fading effect).

FADING (between 0 and 1) 用来考虑衰退效应．Inoculation time（孕育时间） is the time between inoculation and solidification = “physical time + MGTREAT” It is not the same as the solidification time

FADING 1 : inoculation effect disappears after 20 minutes of inoculation time

快冷．小铸件 fast cooling, small partsUse MGTREAT to account for treatment time

FADING 0 : no fading, constant inoculation quality, maximum expansion

慢冷，大铸件 slow cooling, large parts


Microstructure – 验证

Trends for microstructure of Cast Iron增大 EUNUC and EUPOWER 值会减少 graphite nodule 和austenite grains晶粒越大,越容易生成珠光体奥氏体半径越小,铁素体数量越多bigger grains to more pearlite

凝固过程中冷却速率的影响快: metastable eutectic亚共析体 (lédéburite莱氏体)中: stable eutectic, small grains, thus more ferrite更多的铁素体慢: stable eutectic, larger grains, thus more perlite更多的珠光体

Cooling rate effect arround eutectoïd transformation共析出转变温度附近(720°C)冷却速率的影响

快: more pearlite更多的珠光体慢: more ferrite更多的铁素体


Microstructure – calibration

Trends for microstructure of SG IronEffect of Eutectic parameters

EUNUC = 5000

EUPOW = 5

Default RP

EUNUC = 1000

EUPOW = 2.5




EUNUC = 5000

EUPOW = 5

Default RP

EUNUC = 1000

EUPOW = 2.5



Trends for microstructure of SG IronEffect of GRAPHITE on microstructure

Default RP

FADING 0

GRAPHITE 0.6 GRAPHITE 1



Trends for microstructure of SG IronEffect of FADING on microstrucutre

Default RP

FADING 1Default RP

FADING 0

GRAPHITE and FADING :Small effect on microstructure results (Phase fractions and grain

sizes)Large effect on piping and porosity



Trends for microstructure of SG IronEffect of FADING on microstructure

Default RP

FADING 1

Default RP

FADING 0


PERNUC=5.e6

PERGROW=8.4e-4

PERNUC=2.e4

PERGROW=2e-5

PERNUC=2e3

PERGROW=8.4e-4

PERNUC=1e6

PERGROW=2e-5


Microstructure – Calibration example

Guidelines for calibration

Step 1: Adjust the Process-related Run Parameters in order to obtain the right expansion and porosity. By order of importance : GRAPHITE, MOLDRIG, FADING and MGTREAT

GRAPHITE : 0.6 to 1 depending on inoculation quality (initial “Expansion Power”)MOLDRIG : 0.5 to 1 depending of mold hardness (sand = 0.7-0.8)FADING

large part with slow cooling rate : FADING 0 FADING = 0.8 to 1 for small parts, high cooling rateMGTREAT : Process Parameter (user should know this…)

Step 2: Adjust the “Eutectic” Run Parameters EUNUCL, EUPOWER and EUGROW (by order of importance) to match the microstructure observation results in terms of Nodule Count and graphite radius.

Suggested range of variation for these parameters were :EUNUC 1000 to 10000EUPOWER 2.5 to 4EUGROW unchanged SGI default value (3.86e-6)



Step 3: Guidelines for calibration : 2008.1 and 2009.0

According to the observed phase proportion (ferrite / pearlite) of the iron matrix, adjust PERNUC and PERGROW that govern the formation of pearlite vs ferrite (eutectoïdtransformation). Note that the value of these two new R.P were previously hard coded in the solver. The “hard coded” values usually lead to too much pearlite. In the present case, the range of variation for these parameters were

PERNUC 1e+4 to 5e+4PERGROW 5e-6 to 2e-5



Industrial case with experimental results Material : Eutectic SGINo porosity observed, very good inoculationMicrostructure observations

Nodule count (unit of surface)Size of graphite noduleRelative amount of phases

Mechanical testsYield StrengthElongationBrinell Hardness



Results7 analysis needed to obtain satisfactory resultsParameters used

GRAPHITE 1MOLDRIG 0.8 FADING 0.8 – MGTREAT 10s

Fading 0 gave NO porosity at all

EUNUCL 8.00000e+003EUPOWER 2.5 (default)EUGROW 3.86000e-006 (default)

PERNUCL 2.000e+004PERGROW 2.000e-005

CONFIDENTIAL


Microstructure – Calibration exampleResults

Graphite NoduleExperimental

2.0e+04 to 2.2e+04 nodules/cm2 15 to 30 microns radius

CONFIDENTIAL



Results : Graphite nodule count from volumetric to surface countThe microstructure module of ProCAST gives the Nodule Count as the number of graphite nodule per unit volume (default unit is cm-3). According to the Wiencek equation, the surface nodule count and the volume nodule count are related by :

Where g is the volume fraction of graphite nodules.The graphite nodules are spheres. If R is their Radius, one has :

So, the Surface Nodule Count is given by :

In Visual 4.5 one can calculate this and display this contour by using the User Defined Results command in the Results menu.

gNN S

V

3

=

VNRg *34 3π=

VS NRN **34 3/1

⎟⎠⎞

⎜⎝⎛= π



ResultsPhase ProportionExperimental : 90% to 100% ferritic

CONFIDENTIAL



Results : Mechanical PropertiesExperimental :

YS=315 - 323 MPaUTS = 448 – 473 MPa

CONFIDENTIAL



Results : Mechanical PropertiesExperimental :

Hardness : 168 – 172 HBElongation : 17 to 20 %

CONFIDENTIAL



Results : Mechanical PropertiesUse of User functions

\ProCAST\2008.0\dat\manuals\Pdf\MechanicalPropertiesManual.pdf

A. Catalina, X. Guo, D.M. Stefanescu Prediction of Room Temperature Microstructure and Mechanical Properties in Iron Castings , in Modelling of Casting, Welding and Advanced Solidification Processes –VIII, B.G Thomas and C. Beckermann Ed. The Minerals Metals and Materials Society, 1998, pp455-462.

Brinell Hardness

( ) NiwtMowtCrwtCuwtMnwtHBand

SiwtHBwith

fHBfHBgHB

pearl

ferr

pearlpearlferrferr

%10%%%%50223

%*3754

100

+++++=

+=

Yield Strength (MPa)

Ultimate Strength (MPa)

Elongation (%)

++=

( )pearlferrY ffg 8.5872.331)1( +−=σ

( )pearlferrUTS ffg 5.9912.482)1( +−=σ

( )pearlferr ffg 61.52.26)1( +−=ε


Microstructure - Conclusion

Cast Iron : Microstructure Module can now predict amount of phases and mechanicakproperties in a reliable manner

New R.P : PERNUC, PERGROW for pearliteformation (eutectoid reaction)Defect prediction : calibration work to be done

By Us ? By User ?Partnership

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