The Overview of the Refractory Technology from

the Mini-Mill Application Perspective

Tomas Richter

General Manager Europe

HarbisonWalker International

Content

1. Type of Refractories

2. Raw Materials

3. Bonding Systems

4. Manufacturing Process

5. Wear Mechanisms

6. Standard Brick Shapes and Anchors

7. EAF Refractory Lining Considerations

8. Ladle Refractory Lining Considerations

9. Tundish Refractory Lining Considerations

Type of Refractories

Shaped

Products

Unshaped

Products

Hydraulic

Press

Fused

Cast

Isostatic

Press

Assem.

w/cast.

Gunning

Mixes Vibratables

Cast-

ables Mortars

Type of Refractories

Shaped

Products

Hydraulic

Press

Fused

Cast

Isostatic

Press

Prefab

Shapes

Type of Refractories

Unshaped

Products

Monolithics

Gunning

Mixes

Dry

Vibratables Castables Mortars

Manufacturing Process - Refractories

MUCH KNOW-HOW RAW MATERIALS

Equipment

Machinery MIXING

Kilns

etc. SHAPING

TEMP. TREATMENT

Final Product B R I C K

KNOW-HOW Installation

P R O D U C T I O N

B R I C K S

At Customer Site

M I X E S

P R O D U C T I O N

RAW MATERIALS KNOW-HOW

Equipment

MIXING

Semi-finished Product

M I X

At Customer Site

MIXING MUCH KNOW-HOW

Equipment

SHAPING Machinery

Service

TEMP. TREAT. etc.

Acid Neutral Basic

Silica Alumina

Chromic Oxide

Magnesia

Lime

Alumino-Silicate Magnesia-Chrome

Refractory Classifications

Refractory Classification for Steelmaking

Refractory

TypeSilica Fireclay Mullite High Alumina

Main Raw

MaterialQuartz Flint Clay KaoliniticClay

Bauxite and

Corundum

Dominant

Application

Coke Ovens

Blast Furnace

Coke Ovens

Blast Furnace

Blast Furnace

Reheat Furnace

Ladles

EAF

Refractory

Type

Magnesia

Chrome

Zirconia

ZirconDoloma Magnesia

Main Raw

Material

Magnesite

Chrome Ore

Zircon and

Zirconium OxideDolomite Magnesite

Dominant

Application

Secondary

Steelmaking

Ladles, EAF

Flow ControlLadles

AOD

Ladles

BOF

EAF

Mini-mill applications in red

1500

1600

1700

1800

1900

2000

2100

2200

2300

2400

2500

2600

2700

2800

2900

3000

SiO2 Al2O3 Cr2O3 CaO ZrO2 MgO

Te

mp

era

ture

[°C

]

Silica

1702 C

3128 ºF

Alumina

2050 C

3722 ºF

Chromia

2275 C

4127 ºF

Calcia

2600 C

4712 ºF

Zirconia

2700 C

4892 ºF

Magnesia

2800 C

5072 ºF

Melting points of pure refractory oxides

1530 C

2786 ºF

Steel

Melting points of mixed oxides

Ternary Diagram

Magnesia

Sintered and Fused Magnesia

MgO between 90 to 99%

Purity (impurities)

B2O3

SiO2

Al2O3

Fe2O3

(CaO)

Crystal Size between 10 to 1000 microns

Density (porosity of grain) 3.10 to 3.45 g/cc

Microstructure Magnesia

Sintered Magnesia Fused Magnesia

Bonding System Classification

Class Characteristics Result Of:

Ceramic Strong to high temps, brittle, High Temp Firing

low porosity

Chemical Strong to intermediate temps, flexible Acid/Alkali Reaction

continuous matrix

Hydraulic Strong to intermediate temps, Cement/water Reaction

low permeability, high porosity

Carbon Strong to very high temps, oxidation Resin decomposition

continuous matrix, low porosity Carbide development

Bonding Systems

CERAMIC BOND CARBON

BOND

SINTERING

NO

STRENGTH

CARBONISATION

CHEMICAL

BOND PYROLYSIS PYROLYSIS

MESO-

HYDRAU- PHASE

HYDRAULIC RESIN

BOND LIQUEFACTION NETWORK 100°C

500°C

1000°C

1500°C

CACement

Reactive Alumina

-Sodium Silicates

- Phosphates

- Sulphates

- Chromates

Petroleum Pitch Resin

Ceramic bond

Theory: Reality:

unsintered sintered unsintered sintered

Sintering will develop at

presence of:

- additions (binder/sinter aid)

- high temperature

- impurities

- pressure (e.g..: ferrostatic

pressure of steel bath)

- small crystals and grains

Carbon Bonding Resin

45%

Pitch

55 – 70% Carbon yield

- Environment

+ + Matrix strength + Structure

- + Oxydation resistance

Behaviour at process + +

-

-

0

100

200

300

400

212 444 525 1022

Temperature, °F

Wate

r V

apor,

cm

3/g

Casting Water

C3AH6 C3AH6

C3AH1.5

Source: DL Hipps and JJ Brown, Jr.

Cement is a HYDRAULIC BONDING agent for castables, gunning mixes and some mortars which develops hydrates in contact with water.

The type and quantity of hydrates determine the properties of the final refractory concrete.

Classification of Castables (ASTM C401-91)

CaO Level Cement Level

Conventional

Castables

Low Cement

Castables

Ultra-Low Cement

Castables

Cement-Free

Castables

>2.5%

1.0-2.5%

<1.0%

<0.2%

15-30%

4-8%

<4%

No Cement

Category

2. Moisture Loss of Castables with Different

Cement Contents

0

20

40

60

80

100

0 200 400 600 800 1000 1200

Temperature, °F

Mois

ture

Loss,

%

ULC CAST LC CAST CON CAST HC CAST

3. Curing Temperature vs. Strength Castable with 15% Cement Dried 24 hrs. @ 220°F

0

200

400

600

800

1000

1200

1400

40 60 70 90

Curing Temperature, °F

Str

ength

, psi

Permeability of Bricks vs. Castables

0

1

2

3

4

5

6

7

0 250 500 750 1000 1250 1500 1750

Firing Temperature, °C

Rela

tive P

erm

eabili

ty

BRICK

CASTABLES

4. Curing Temperature vs. Permeability Castable with 15% Cement Dried 24 hrs. @ 220°F

0

10

20

30

40

50

60

70

80

40 60 70 90

Curing Temperature, °F

Perm

eabili

ty C

onsta

nt,

Englis

h u

nits x

10

6

Manufacturing Process - Refractories

MUCH KNOW-HOW RAW MATERIALS

Equipment

Machinery MIXING

Kilns

etc. SHAPING

TEMP. TREATMENT

Final Product B R I C K

KNOW-HOW Installation

P R O D U C T I O N

B R I C K S

At Customer Site

M I X E S

P R O D U C T I O N

RAW MATERIALS KNOW-HOW

Equipment

MIXING

Semi-finished Product

M I X

At Customer Site

MIXING MUCH KNOW-HOW

Equipment

SHAPING Machinery

Service

TEMP. TREAT. etc.

Refractory Manufacture - Brick

Standard Refractory Shapes

Standard Refractory Shapes

Standard Refractory Shapes

Standard Refractory Anchors

Standard Refractory Anchors

Wear Mechanisms

Corrosion by Slag

Chemical

Temperature Wear

Wear Mechanisms

Corrosion by Slag

Chemical

Thermal Expansion of Refractories

0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

0 500 1000 1500

Temperature [C]

Th

erm

al E

xp

an

sio

n [

%]

M agnesia

Dolomite

Chromite

90% Corundum

80% Bauxite

M ullite

SiC

Graphite

Mechanical Wear

Thermal Conductivity of Refractory Bricks

0.0

20.0

40.0

60.0

80.0

100.0

120.0

900 1,400 1,900 2,400

Temperature, [o F]

Th

erm

al

Co

nd

ucti

vit

y,

BT

U.i

n/(

hr.

ft2.oF

)

Mag Carbon 20% C

Mag Carbon 15% C

Mag Carbon 10% C

Mag Carbon 5% C

Dolomite or MgO - Fired

Dolomite C - Bonded

Alumina Magnesia

Carbon

Mag-Chrome Fired

80% Alumina - Fired

Mechanical Wear

One-sided heating

One-sided expansion

tensile + compression stresses

cracks

One-sided cooling down

One-sided shrinking

compression + tensile stresses

cracks

Reasons for thermal stresses

Wear Mechanisms

Corrosion by Slag

Chemical

Solutions consisting primarily of molten metal oxides

Float on top of the steel because of specific gravity

lower than that of molten steel

Primarily liquid at steel making temperatures

Play an essential role in the steel making process

2C + O2 2CO

2Fe + O2 2FeO

4Al + 3O2 2Al2O3

Si + O2 SiO2

4P + 5O2 2P2O5

2Mn + O2 2MnO

Slags

Larry Wolfe, Carmeuse Lime & Stone– AIST Practical Seminar

Charleston, S.C., 2/2012

Slag Formers – Lime and Dolo-lime

PRIMARY SOURCES OF SLAGS

Oxidation of metallic elements from scrap

Non metallics- Sulfur & Phosphorus

Flux Additions – Dolo & hi calcium lime, spar

Dissolved refractory – Hearth material, gun

material, brick

0

5

10

15

20

1 2 3 4 5

Lime-Silica Ratio of the Liquid Slag (CaO/SiO2)

Per

cent

of

MgO

Dis

solv

ed in

the

Liq

uid

3100ºF*

3000ºF**

2750ºF

2900ºF

Solubility of Magnesia in a

Steelmaking Slag

• Four Variables:

– MgO content

– FeO content

– Temperature

– Basicity

• ISD’s show phase

relations of MgO

and FeO content at

fixed basicity and

temperature

Isothermal Stability Diagram

Solubility of Magnesia in Steelmaking Slag

Carmeuse Technical Training

EAF Refractories

• Magnesia Carbon: fused / sintered

- Carbon content 10-15%

- Metal additions for oxidation and strength

• Burned Magnesite: impregnated with pitch

• Hearth / Anode: 70 - 80% Magnesia

• Gunning; 60 to 98% Magnesia

• Delta: 80-85% alumina

EAF Bottom Designs

EAF Bottom Designs

Hearth Installation

De-air using pitchforks, vibrators or

walking on until proper compaction is

attained

Repeat these steps several times until

desired depth is achieved

Final compaction should be very firm

Final grade may be finished off by

using vibrating sled if desired

Examples or Refractory Applications – Electric Arc Furnace at

Installation

Magnesia-Carbon Bricks

Carbon Levels (usually 5-20%)

Higher levels : more slag resistant

Higher levels : resist EAF and LMF arc flare

Higher levels : more thermal shock resistant

Higher levels : less oxidation resistant

Magnesia- Carbon Bricks

Metal Additions

Higher levels yield stronger bricks.

Higher levels yield more oxidation resistant bricks.

Higher levels cost much more.

Higher levels – Bricks more brittle

Welded Door Jambs

NUCOR - NARCO

October 2009

One Piece Assembly

February 16-17, 2010 ANH Refractories Company

EAF Taphole Designs

EAF Straight Bore Taphole

EAF Conical Bore

EAF Delta and Roof •Primary function of Delta is to protect the roof from the electrode arc generated

during the melting operation.

•It is exposed to arc flare, thermal shock, oxidation, chemical corrosion, post

combustion and high temperatures.

Furnace Mono Installation Equipment

Furnace Gunning

Steel Ladles

Steel Ladles Safety Lining

Brick Safety Lining Monolithic Safety Lining

Steel Ladles

INSULATION

Insulation – Brings Freeze Plane into

Brick

Best Scenario - No Insulation

2nd Best - Minimize Insulation

Insulation versus no Insulation

Steel Ladles – Working Linings

US Steel Market

35%

50%

15%

Si-killed

Integrated

Al-killed

Steel Ladles

Lip Ring Constructions

Steel Ladles - Bottom

Precast and Composite Bottoms

Gas Purging Systems

Stir Plugs - Multiple Designs

and Compositions in Both Porous and Directional

Pocket Blocks – Multiple Compositions

Conventional Cast

Compression Cast

ISO Pressed

Plug Asssemblies – Could have some safety and life benefits

Plug Exchange Systems Multiple Systems ussually

supplied by the plug manufacturer

Well Blocks

Steel Ladles

Successful Monolithic Installations

Castables & Shotkast &Gunning Mixes

Material & Water Above 70 F

Cure at 70 to 90 F for High Strength

Use Recommended Amount of Clean,

Drinkable Water

Follow Recommended Heat-Ups

Tundish Technologies

Tundish Baffles

Tundish Impact Pads

Cast Tundish lining

Dry Vibe vs. Spray Technology

Profile with dry vibe Profile with spray

2.0 inch

1.5 inch

0.5 inch

2.0 inch

1.25 inch

2.0 inch

Tundish Spray Machines

What is important?

Reliable Control Equipment.

Easy operation.

Simple maintenance.

Recycle options.

Rapid, reliable spray application.

Auxiliary material handling systems.

Manual Spray systems.

Full Robotic systems for

high volume shops.

Spraying Tundish

Sprayed Tundish w/Baffle

Tundish Dryer

Dry-Vibe Mandrel/Curing Unit

Dry-Vibe Working Lining

Thank You