Cast Steel Research

V. Richards and S. Lekakh

Missouri S & T

October 29, 2012

Steel Casting Capability

- Unique capability: melting high quality

complex alloys, high purity steels (alone

among US Universities)

- Diverse molding capability (green sand, no-

bake, ceramic investment, ingot molds)

- Advanced instrumentation: temperature,

active oxygen, chemistry, LECO (C, S, N, O),

thermal analysis

Projects overview

Liquid and solidified steel

Solidification kinetics

- thermal analysis

- thermodynamic modeling (FACTSAGE)

Fluidity phenomena and mold filling

- electric sensing of fill

- CFD (Fluent, Magma) modeling

Metal-mold interactions

- Ceramic molds

- Burn-in defects in sand molds

High temperature thermal properties of mold materials

- physical measurements

- inverse modeling

Solidification of high strength cast steel

Thermal probe with low Biot number Bi=hL/k

Important steel solidification parameters:

Tliq and Tsol

Fraction solid versus T

Dendrite coherency point

Solid fraction versus temperature is

significantly different as peritectic is

shifted

0.0

0.2

0.4

0.6

0.8

1.0

1450 1470 1490 1510 1530

So

lid

fra

cti

on

Temperature, ⁰C

Heat 1 (base)

Heat 2 (3% Ni)

Heat 3 (5% Ni)

Heat 4 (9% Ni)

Heat 5 (9% Ni, 3.5% Cu)

Fe(L)+FCC

Thermodynamic approach

using Factsage

Austenite Stabilizers Shift Peritectic

Use of low Biot number mold to analyze casting properties near a peritectic

Modeling confirmed with experimental approaches

Electric sensor

0

5

10

15

20

25

30

35

40

45

0 2 4 6 8 10

Fil

l len

gth

, cm

Ni content, wt%

20C(exp)20C(model)60C(exp)60C(model)80C(exp)80C(model)

Modeling combined with experimental verification using

electrical sensing and DAQ Calculated (Magma) and measured mold filling

2.40-2.50

2.30-2.40

2.20-2.30

2.10-2.20

2.00-2.10

1.90-2.00

1.80-1.90

1.70-1.80

1.60-1.70

1.50-1.60

1.40-1.50

1.30-1.40

1.20-1.30

1.10-1.20

1.00-1.10

0.90-1.00

0.80-0.90

0.70-0.80

3.20-3.30

3.10-3.20

3.00-3.10

2.90-3.00

2.80-2.90

2.70-2.80

2.60-2.70

2.50-2.60

2.40-2.50

2.30-2.40

2.20-2.30

2.10-2.20

2.00-2.10

1.90-2.00

1.80-1.90

Solidification properties data MST generated enabled

modeling to solve casting problems with new steel alloys

Gas pressure Velocity Temperature

Ceramic mold/steel melt interactions

Thermal condition:

- mold T exceeds Tliquidus

Thermo-chemical conditions:

- melt oxidation followed by

reaction with ceramic mold

0

0.2

0.4

0.6

0.8

1

800 1000 1200 1400 1600

Fra

cti

on

Temperature, 0C

Liquid slag

MeSiO3

Cristobalite +Mullite

Burn-in defects in sand molds

B

Quality of sand supporting wash is critical. Residual binder in mechanical

reclaim carries fluxing oxides. Loss of wash support

High temperature thermal properties of mold materials

0

200

400

600

800

1000

1200

1400

1600

0 200 400 600 800

Te

mp

era

ture

, 0C

Time, sec

Tcasting calTshell calTcasting exp

Tshell exp

High T thermal conductivity - novel laser flash method

Inverse experimental/modeling method

Potential Applications

• Solidification properties of new steels

– Effect of Austenite stabilizers (Ni, Mn,?)

– Critical temperatures-Tliq, Tsol,

– Fraction solid versus temperature

– Dendrite coherency point

• Casting sound plates/ingots for subsequent

processing (rolling, heat treatment)

• Full suite of processes after casting

• Thermal analysis of mold

powders/fluxes/coatings effects on heat transfer