Limitations in calculating of optimized temperature-/time...

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Fachgebiet Fertigungstechnik

Univ.-Prof. Dr.-Ing. habil. Johannes WildenSTAR Surface Technologies Advanced ResearchProf. Dr.-Ing. habil. Johannes Wilden, HS-Niederrhein

Prof. Dr. rer. nat. habil. Wolfgang Müller, TU Berlin

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Limitations in calculating of optimizedtemperature-/time-cycles in brazing using

Thermo-Calc and Dictra

Oliver Stahn, M. Sc.

HS Niederrhein

Maschinenbau und Verfahrenstechnik

Funktionswerkstoffe und Beschichtungen

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Agenda

A brief introduction to brazing

Thermo Calc property diagrams for Ni-based filler materials

TC DICTRA simulation for the joint 16Mo3 – Ni 650

o model

o source code with emphasis on non-default options

o post processing

o results

Application of DICTRA results to produce actual joints

Summary

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Brazing

- metal-joining process using filler-materials- only the filler-materials melts, not the parts themselfs- filler-materials are usally based on Ni, Fe, Cu, Au, Ag- no flux agent- brazing temperature > 900 °C- protective gas or vacuum atmosphere- can be used to join a lot of materials, e.g., metals, ceramics- tensile strength of the joints can be in the order of

magnitude of the base materials- brazing can be done by furnaces, induction, torch,

resistance, electric arcs

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[1] http://technicalmaterials.umicore.com/Brazetec/en/Applications/kreissaegeblatt/kreissaegeblatt.htm[2] http://www.protorque.com/picts/protorque-furnace-brazed-torque-converter-turbine.jpg[3] http://airec.se/wp-content/uploads/2014/09/cross-30.jpg[4] http://www.siemens.com/press/pool/de/pressebilder/2014/corporate/soaxx201412/072dpi/

soaxx201412-04_072dpi.jpg

[1]

[2]

[3] [4]

Applications

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1.4301 – BNi60CrPSi‐980/102020 min, 1090 °C

100 µm brazing gap

50 µm

50 µm

1.4301 – BNi60CrPSi‐980/102090 min, 1090 °C

100 µm brazing gap

• problem: brittle phases in the joint• countermeasures

o small brazing gaps, less than50 µm

o heat treatment• both increase production effort

signaficantly• our approach:

o increase in temperature leedsto faster diffusion

o right dwelling time → fewer brittle phases

o homogenization of the joint

Brazing with nickel-based filler materials

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element wt.-%

Cr 19

Si 10

Ni bal.

filler: Ni 650database: TCNI5

solidus and liquidustemperature according toDIN EN ISO 17672:

solidus: 1080 °Cliquidus: 1135 °C

Property diagramm of Ni 650

temperature (°C)

fraction (

%)

Ni m. c.

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element wt.-%

Cr 7

Si 4.5

B 3

Fe 3

Ni bal.filler: Ni 620database: TCNI5

solidus and liquidustemperature according toDIN EN ISO 17672:

solidus: 970 °Cliquidus: 1000 °C

fractio

n (

%)

temperature (°C)

Ni m. c.

Property diagramm of Ni 620

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• calculations with Thermo-Calc are not valid for all materials ofinterest→ the derivation of temperature-/time-cycles is limited

• calculations with Thermo-Calc foro Ni 650 are possibleo Ni 620 are unsureo B-Ni60CrPSi-980/1020 are not possible (6 wt.-% P)

Limitations of Thermo-Calc

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DICTRA simulations

• TC Dictra: Moving phase boundary model• defining two areas, filler and base material• model offers clear separation of base und filler materials• symmetry is applied → only half a joint is treated in the

simulation• brazing gap width is an output variable of the model

(Position of Interface)

PoI

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DICTRA simulations

wt.-% C Cr Fe Mo Ni Si

Ni 650 10-5 19 10-5 10-5 bal 10

16Mo3 0.07 0.17 bal 0.3 0.016 0.28

• dwelling time: 90 min, 150 min• brazing temperature: 1170 °C, 1195 °C, 1220 °C

PoI

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DICTRA simulations – basic system definition

goto_module data

switch_database tcfe7

define_system ni cr si fe c mo

reject phases *

restore phases fcc liq

get_data

append_database mobfe2

define_system ni cr si fe c mo

reject phases *

restore phases fcc liq

get_data

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DICTRA simulations – geometry, regions, phases and time

goto_module dictra_monitor

set_condition global t 0 1493.15; * n

enter_geometrical_exponend 0

enter_region ni650

enter_region 16mo3 ni650 y

enter_grid_coordinates ni650 25e-6 geo 25 0.97

enter_grid_coordinates 16mo3 10e-3 geo 200 1.03

enter_phase_in_region active ni650 matrix liq

enter_phase_in_region active 16mo3 matrix fcc_a1#1

set_simulation_time 9000 y 10 1e-10 1e-12

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DICTRA simulations – geometry, regions, phases and time


set_condition global t 0 1493.15; * n

enter_geometrical_exponend 0

enter_region ni650

enter_region 16mo3 ni650 y

enter_grid_coordinates ni650 25e-6 geo 25 0.97

enter_grid_coordinates 16mo3 10e-3 geo 200 1.03

enter_phase_in_region active ni650 matrix liq

enter_phase_in_region active 16mo3 matrix fcc_a1#1

set_simulation_time 9000 y 10 1e-10 1e-12

set_simulation_time

END TIME FOR INTEGRATION /.1/: 9000

AUTOMATIC TIMESTEP CONTROL /YES/: y

MAX TIMESTEP DURING INTEGRATION /.01/: 10

INITIAL TIMESTEP /1E-07/: 1e-10

SMALLEST ACCEPTABLE TIMESTEP /1E-07/: 1e-12

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DICTRA simulations – simulation settings

set_simulation_condition 0 1 2 NO ACTIVITIES YES YES

1 2 NO YES NO

homogenization_model y n NO YES 10000 LOG 0.2 NO NO

n .98 3e-6 1 .005 20

utilities_homogenization NO NO NO NO NO NO NO NO NO NO

y 3 NO NO NO NO NO NO

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1 2 NO YES NO


n .98 3e-6 1 .005 20



set_simulation_condition

NS01A PRINT CONTROL : /0/: 0

FLUX CORRECTION FACTOR : /1/: 1

NUMBER OF DELTA TIMESTEPS IN CALLING MULDIF: /2/: 2

CHECK INTERFACE POSITION /NO/: NO

VARY POTENTIALS OR ACTIVITIES /ACTIVITIES/: ACTIVITIES

ALLOW AUTOMATIC SWITCHING OF VARYING ELEMENT /YES/: YES

SAVE WORKSPACE ON FILE (YES,NO,0-999) /YES/: YES

DEGREE OF IMPLICITY WHEN INTEGRATING PDEs(0 -> 0.5 -> 1)/.5/: 1

MAX TIMESTEP CHANGE PER TIMESTEP : /2/: 2

USE FORCED STARTING VALUES IN EQUILIBRIUM CALCULATION /NO/: NO

ALWAYS CALCULATE STIFFNES MATRIX IN MULDIF /YES/: YES

CALCULATE RESIDUAL FOR DEFENDENT COMPONENT /NO/: NO

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1 2 NO YES NO


n .98 3e-6 1 .005 20



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DICTRA simulations – simulation settingshomogenization_model y n NO YES 10000 LOG 0.2 NO NO

n .98 3e-6 1 .005 20



homogenization_model

ENABLE HOMOGENIZATION /NO/: y

USE DEFAULT SETTINGS /YES/: n

ADD IDEAL FLUX CONTRIBUTION /NO/: NO

USE INTERPOLATION SCHEME /YES/: YES

ENTER NUMBER OF STEPS BETWEEN XMIN AND XMAX /10000/: 10000

LINEAR OR LOGARITHMIC DISCRETISATION /LOG/: LOG

FRACTION OF FREE PHYSICAL MEMORY TO BE USED /.01/: 0.2

USE GLOBAL MINIMIZATION /NO/: NO

REFRESH JACOBIAN EVERY ITERATION /NO/: NO

DEFAULT GRID PARAMETER VALUES /YES/: n

GEOMETRICAL COEFFICIENT (0+ -> 1) /.98/: .98

FIXED INTERFACE WIDTH (<0 DISABLES) /-1/: 3e-6

GRID FINENESS AWAY FROM INTERFACE /1/: 1

INTERFACE WIDTH FRACTION (0+ -> 0.1) /.005/: .005

CONSECUTIVE CRITICAL DT TO DELETE REGION /20/: 20

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1 2 NO YES NO


n .98 3e-6 1 .005 20



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DICTRA simulations – simulation settingsutilities_homogenization NO NO NO NO NO NO NO NO NO NO


utilities_homogenization

SET TEMP ACCORDING TO SOLIDUS TEMPERATURE /NO/: NO

DUMP RESULTS TO TEXT FILES /NO/: NO

READ INITIAL COMPOSITION FROM TEXT FILE /NO/: NO

ENTER GHOST PHASE /NO/: NO

ENTER INACTIVE PHASES INTO ONE REGION /NO/: NO

EXPLICITLY SET SUBSTUTUTIONAL/INTERSTINIAL /NO/: NO

SAVE AVERAGE FINITE VOLUME COMPOSITION /NO/: NO

SET CONSTANT PHASE ADDITION /NO/: NO

USE ELEMENT MOBILITY PREFACTOR /NO/: NO

ENTER ELEMENT MOBILITY ESTIMATE /NO/: NO

ENTER MINIMUM SAVE INTERVAL /NO/: y

SAVE INTERVAL [S]: /1/: 3

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DICTRA simulations – saving and starting the simulation

set-log 2

save_workspaces output.dic

simulate_reacion

set_interactive

• This simulation can be started from a macro-file• Post processing is done in another macro-file

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DICTRA simulations – post processing


read output.dic

post_processor

label_curves y

set_raster_status y

set_plot_format 17 YES 25 .4

@@position of interface plot

set_diagram_axis x time

set_diagram_axis y pos ni650 upper

plot_diagram PoI.ps

make_experimental_datafile PoI.exp

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DICTRA simulations – post processing

set_diagram_axis dist global

set_scaling_status x n 0 0.0001

set_plot_condition time 0

@@plot amount of elements

set_diagram_axis y w-p fe

plot_diagram fe.ps

make_experimental_datafile fe.ps

set_diagram_axis y w-p cr

plot_diagram cr.ps

make_experimental_datafile cr.ps

.

.

.

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DICTRA simulations – results

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dwelling time (min)

dis

tan

ceb

etw

een

fro

nts

of

solid

ific

atio

n(µ

m)

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Ni 650 – 16Mo3: 1220 °C, 270 min, brazing gap width 50 µm

Results of proposed temperature-/time-cycles

w/o normalising w/ normalising930 °C, 30 min

50 µm50 µm

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Results of proposed temperature-/time-cycles

0

100

200

300

400

500

600

tensile strength 16Mo3 -- Ni 650

1195 °C, 20 min 1220 °C, 270 min

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Summary A brief introduction to brazing Thermo Calc property diagrams for Ni-based filler materials

o good results for Ni 650o problems with other filler materialso material composition is import when applying

Thermo Calco calculation of temperature-/timecycles is limited

TC DICTRA simulation for the joint 16Mo3 – Ni 650o knowledge of useful option is vitalo applicable for some material combinations in brazing

Application of DICTRA results to produce actual jointso brazed joints without brittle phaseso significant increase in joint tensile strength

Limitations in calculating of optimized temperature-/time...

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Transcript of Limitations in calculating of optimized temperature-/time...