cast steel research · 2020. 7. 24. · steel casting capability -unique capability: melting high...
TRANSCRIPT
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