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Dec 11 2018

Tundish Refractory

Tundish Refractory Description

The main function of tundish is keeping the temperature of steel liquid stable, making impurity float to the surface of steel liquid, promising the smooth going of the continuous casting during steel liquid shortage or steel ladle changing. The capacity of tundish is usually 15%~30% of steel ladle. Every continuous casting machine will equip 7~12 tundishes. Tundish Steel liquid temperature is 1510~1570℃. Learn more about the tundish refractory, please continue reading.

As a transition device between the ladle and the mold during the continuous casting process, the tundish is not only storage and distributor of the molten steel, but also a refining vessel of the molten steel. It can be used to stabilize the steel flow, reduce the scouring of the billet shell in the mold by the steel flow so that the molten steel has a reasonable flow field and a proper long residence time in the tundish. In order to ensure the uniform temperature of the molten steel and the separation and floating of non-metallic debris, the cleanliness of the molten steel and the continuous casting of multiple furnaces are an important part of improving the quality of steel and the efficiency of continuous casting. The structure diagram of the tundish is shown below.

Tundish refractory — Schematic Diagram of Tundish Structure

The Main Function of the Tundish

(1) Diversion of molten steel. For multi-stream and continuous casting machines, the molten steel is distributed to each mold through the tundish.
(2) Steady flow. Reduce the static pressure of the molten steel to maintain a stable liquid level in the tundish. Pour molten steel into the mold steadily.
(3) Store molten steel. When replacing the ladle with multiple furnace continuous casting, the drawing speed is not reduced. Create conditions for multiple furnace continuous pouring.
(4) Purify molten steel. In a long pouring time, the temperature of the molten steel is basically unchanged, and the inclusions in the molten steel are further raised. Avoid contact between molten steel and air, and avoid oxygen and nitrogen absorption.

Refractory Materials for Tundish

Refractory materials for tundish can be divided into three categories in terms of function.

The first category is lining materials. It is mainly composed of the thermal insulation layer, permanent layer, and working layer.
The second category is steady flow components. Including slag weir, slag baffle, impact plate, etc.
The third category is the flow control part. There are stoppers, sliding nozzles, sizing nozzles, and intrusive nozzles.

For billet continuous casting, the core of efficient continuous casting is high drawing speed. This requires that on the basis of the quality of the molten steel meeting the requirements, the continuous operating rate of the continuous caster and the casting speed should be increased as much as possible. To achieve higher billet temperature and cast billet quality. These technical indicators put forward two requirements for tundish refractories, one is a high performance, and the other is long life.

integral stopper

submerged nozzle

long nozzle

The Flow Control Part of the Tundish

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Composition of the Refractory Lining in the Tundish

The tundish is lined with refractory materials and generally includes the following parts. Refractory materials for different parts of the tundish are introduced respectively.

(1) Insulation layer (10-30mm), this layer is next to the steel shell of the tundish. Asbestos boards, insulation bricks, or lightweight castables are usually used. The best effect is aluminum silicate fiber felt, which has low thermal conductivity and is easy to build. Insulating lining. Insulating lining usually adopts clay bricks or insulating board, some steel mills may have no insulating lining.

(2) Permanent layer (100-200mm), which is in contact with the insulation layer. The material is generally clay bricks. The overall permanent lining is the most common, and the castable is generally high-alumina or mullite self-flowing castable. Permanent lining. The permanent lining is made from low cement or ultra-low cement alumina castable, which contains 60%~80% of Al2O3. The service life of permanent lining is between 200~1000 times, or even more.

(3) Working layer (20-50mm), this layer is in contact with molten steel and is the key part. Nowadays, insulation boards or coatings are commonly used. Insulation panels are generally siliceous, magnesia, or forsterite. The paint is magnesia, magnesia chromium, and magnesia calcium. The paint is sprayed mechanically or applied by hand. Corrosion lining. Corrosion lining is made from magnesia coating mix, insulating boards, or dry ramming mass.

(4) The Well Blocks are inlaid at the bottom of the tundish and used to install the tundish nozzle. The material is usually high alumina.

(5) The material of the bottom of the tundish is basically the same as that of the working layer. The bottom working layer of the tundish is easily damaged by the impact of molten steel, which requires corrosion resistance and wear-resistance. High-alumina bricks or dense high-alumina bricks and alumina-chrome bricks are generally used, and large, high-strength tar magnesia bricks are also used. The impact part of molten steel is reinforced with zircon bricks or prefabricated blocks.

(6) The tundish cover covers the tundish, which can play the role of heat preservation and molten steel splashing. The material is made of clay or high-alumina castable as the cover, usually adopts the alumina-silica castable with 60% of Al2O3.

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(7) The slag retaining wall (weir), which is built in the tundish, can be a single wall or a double wall. The material of the slag retaining wall weir is usually high-alumina bricks, but can also be made into prefabricated blocks, and its purpose is to block. In order to improve the cleanliness of molten steel, a molten steel filter can also be installed on the slag retaining wall.

Impaction zone. Impaction zone can use high alumina precast blocks or high alumina bricks, magnesia precast blocks or magnesia carbon bricks can also be used.
Slag baffle. Slag baffles are mainly made from magnesia precast blocks. Magnesia calcium slag baffle which can adhere impurity in steel liquid is also under development.
Stopper. Alumina carbon integral stopper.
Metering nozzle. Zirconia metering nozzle. For small billet continuous casting, metering nozzle zirconia content can reach 94%, bulk density can reach 5g/cm3. Its service life can be longer than 20 hours.
Upper nozzle. Alumina carbon upper nozzle or sintering mullite upper nozzle.
Sliding gate. Alumina carbon sliding gate or alumina-zirconia carbon sliding gate.
Coating mix. Magnesia calcium coating mix can significantly decrease oxygen content and sulfur content in steel liquid, impurity index can decrease 37%.
Tundish nozzle. Corundum mullite nozzle or alumina carbon nozzle are usually used in the tundish. To avoid blockage during killed steel casting, there is also argon-blowing purging nozzle.

Tundish Refractory Materials Physiochemical Index

Item	LZ-1	LZ-2	LZ-3	LZ-4	LZ-5	LZ-6
Name	Magnesia chrome coating mix	Magnesia coating mix	Magnesia coating mix	Magnesia coating mix	Magnesia coating mix	Magnesia calcium coating mix
Cr2O3 %	5~10	/	/	/	/	/
MgO %≥	70	85	85	85	85	70
CaO%	/	/	/	/	/	≥10
SiO2 %≤	4	6	6	6	6	6
Bulk density g/cm3(110℃,24h)	≥2.2	≥2.2	1.8~2.0	1.4~1.6	1.1~1.25	≥1.80
Crushing strength Mpa (110℃,24h) ≥	4	5	4	3	3	3
Thermal conductivity W·(m·K)^-1(500 ℃) ≤	1.2	1.0	0.8	0.6	0.4	0.8
Reheating linear change rate(1500℃,3h)	0~-1.5	0~-2.0	0~-2.5	0~-2.5	0~-2.5	0~-3.5

Item	LZ-7	LZ-8	LZ-9	LZ-10	LZ-11	LZ-12
Name	Magnesia dry mix	Magnesia calcia dry mix	Silica insulating board	Silica insulating board	Magnesia insulating board	Magnesia insulating board
MgO %	≥90	CaO 93	/	/	≥85	≥94
CaO%	/	≥10	/	/	/	/
SiO2 %	≤2	≤2	≥94	≥94	≤6	≤3
Bulk densityg/cm3(110℃,24h)	≥2.45	≥2.4	≤1.4	≤1.6	≤1.5	≥2.6
Crushing strength Mpa	≥15 (1500℃,3h)	≥15 (1500℃,3h)	/	/	≥20	≥30
Thermal conductivity W·(m·K)^-1(500 ℃) ≤	1.5	1.3	0.45	0.6	0.6	1.8
Reheating linear change rate(1500℃,3h)	0~-1.0	0~-1.0	0~2	0~2	0~-1.5	±0.6

Item	LZ-13	LZ-14	LZ-15	LZ-16	LZ-17	LZ-18
Name	High alumina brick	High alumina castable	High alumina castable	High alumina castable	Mullite purging upper nozzle	Alumina carbon down nozzle
MgO %	75	≥60	61.9	62.1	81.25	80.85
CaO%	/	≥10	/	/	/	/
SiO2 %	≤2	≤0.7	0.64	0.68	/	/
Apparent porosity %	19-21	/	/	/	21	5.5
Bulk density g/cm3	≥2.5	≥2.55 (110℃,24h)	≥2.39 (110℃,24h)	2.41 (110℃,24h)	2.67	2.87
Crushing strength Mpa	≥60	≥20 (110℃,24h)	≥14.7 (110℃,24h)	≥17.6 (110℃,24h)	83.6	101
Refractoriness ℃	>1790	>1790	>1790	>1790	/	/
Reheating linear change rate(1500℃,3h)	-0.2~0	±0.5

Item	LZ-19	LZ-20	LZ-21	LZ-22	LZ-23
Name	Magnesia slag baffle	Magnesia carbon temperature measuring casing	Electric conduction brick	Clay brick	High alumina mortar
Al2O3 %	/	/	/	>40	82.36
MgO %	>90	>70	>80	/	/
(F.C) %	/	>15	>10	/	/
Apparent porosity %	<17	<5	<5	<18	/
Bulk density g/cm3	>2.80	>2.80	>2.80	2.2	/
Crushing strength Mpa	60	>20	>40	>40	Adhesion time: 1~3 Min
Modulus of rupture Mpa	>8	>10	>10	/	8(1500℃,2h)

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Steel industry refractories

Dec 11 2018

Heating Furnace Refractory

Heating Furnace Refractory Description

Heating furnace is thermal equipment used for heating steel billets or small steel ingots during steel rolling or steel forging. Heating furnace’s working temperature is usually below 1400℃. For continuous or circular heating furnaces, there are three temperature zones: low temperature zone, middle temperature zone and high temperature zone, i.e., preheating zone, heating zone and soaking zone, the temperature is 800~900℃, 1150~1200℃, 1200~1300℃, respectively.

The main damage reason of furnace lining is temperature fluctuation caused by discontinuous operation or alternative stop and open of furnace. Furnace bottom and furnace wall base part are mainly damaged by chemical reaction of molten iron oxide and firebricks. So different refractory materials should be chosen for different parts. If the working condition of heating furnace is good, the service life will be longer than 2 years.

Heating Furnace Refractory Classification

Alumina silica refractories are usually used in heating furnaces. Working lining of heating furnace is built by alumina silica firebricks, while outer lining is built by lightweight clay bricks, insulating boards and so on. For example, the roof of soaking zone and heating zone can adopt high alumina hoisting bricks. From inner layer to outer layer, furnace wall is built by high alumina bricks, clay bricks, lightweight clay bricks and insulating boards. Heating zone furnace bottom should resist iron oxide slag corrosion, so magnesia chrome bricks or magnesia bricks can be used here. At preheating zone, working layer can choose clay bricks.

With the development of castable, the ratio of casting refractory used in heating furnaces is increasing gradually. It brings great convenience for mechanization and automation. Meanwhile, the service life, heat preservation efficient and integration ratio are increased.

Item	JRL-1	JRL-2	JRL-3	JRL-4	JRL-5
Name	High alumina mortar	Clay mortar	Mullite bricks	Clay bricks	Clay bricks
Application	Furnace bottom	Furnace bottom furnace wall, flue	Furnace lining	Furnace bottom flue	Furnace bottom flue
Al2O3 %	66.26	33.92	>75	>50	≥40
Fe2O3 %	/	/	<0.5	/	1.78
Apparent porosity %	/	/	18	<18	18
Bulk densityg/cm3	/	/	2.60	2.27	2.30
Crushing strength Mpa	/	/	121.6	54.6	60
Refractoriness ℃	1790	1690	1830	1730	1750
Reheating linear change rate	/	/	/	-0.71(1500℃,3h)	Thermal shock resistance ≥8 times(1100℃,water cooling)

Item	JRL-6	JRL-7	JRL-8	JRL-9	JRL-10
Name	Semi silica bricks	Calcium silicate board	Insulating castable	Insulating castable	Clay insulating bricks
Application	Flue	Flue, inner lining	Flue	Flue, inner lining	Flue
Al2O3 %	19.49	/	>30	≥30	40.33
Fe2O3 %	1.91	/	<3	≤5	/
Apparent porosity %	17	/	/	/	/
Bulk densityg/cm3	2.12	0.218	1.8	1.10	0.90
Crushing strength Mpa	25.5	/	1.8	>6	3.58
Refractoriness ℃	1610	1000(Max working)	1200(Max working)	1100(Max working)	1710
Reheating linear change rate	/	1.34(1000℃,3h)	-0.4(1500℃,3h)	-0.5 (900℃)	-1.0 (1300℃,2h)

Item	JRL-11	JRL-12	JRL-13	JRL-14	JRL-15
Name	Magnesia chrome brick	Magnesia brick	Corundum SiC brick	Sintering chrome corundum brick	High alumina SiC brick
Application	Hot air tube	Hot air tube	Sliding rail, well block	Sliding rail, well block	Well brick
Al2O3 %	<4	/	>76	>90	60
MgO%	>60	>90	/	/	/
Cr2O3 %	>12	/	/	>3	SiC, 12~15
SiO2 %	<2	<4	SiC, 12~15	/	/
Fe2O3 %	<7	1.5	1.0	<1.5	2.0
Apparent porosity %	<22	<18	<18	<20	22
Bulk densityg/cm3	>3.10	>2.85	>2.90	>3.20	/
Crushing strength Mpa	≥30	>45	>70	>100	49.0
Refractoriness under load ℃	>1700	>1550	>1650(0.4Mpa)	>1700	1550(0.4Mpa)
Thermal shock resistance/ times	/	/	>18	/	>8

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Dec 10 2018

Sliding Nozzle System Refractory

Sliding Nozzle System Refractory Description

Sliding nozzle system are mainly used in two places, one is at the bottom of steel ladle, plays the role of steel liquid flowing rate control unit, the other is at the bottom of tundish, controlling steel liquid flowing rate from tundish to crystallizer. Sliding gate’s movement is controlled by operation unit, so the hole of up-sliding gate and down-sliding plate can be opened and closed at will, steel liquid flow rate is adjusted in this way.

Sliding nozzle system is composed of well bricks, sprue bricks and sliding gate. As to ladle sliding gate, high quality alumina zirconia carbon sliding gate and alumina carbon sliding gate’s service life is about 2~4 times. For tundhish sliding gate, it should serve a continuous casting cycle, which means the service life is usually below 8 times. For ordinary steel casting, alumina carbon sliding gate and alumina zirconia carbon sliding gate can meet production requirement. For up-long nozzle, corundum bricks, alumina carbon bricks and chrome corundum bricks are usually adopted. Their service life is between 20~30 times.

Ordinary casting sliding gate system refractory

Item	Alumina carbon up nozzle	Alumina carbon mortar	Alumina zirconia carbon sliding gate	Alumina carbon down nozzle	Alumina down nozzle
Application	Steel ladle sliding nozzle	Sliding nozzle masonry	Steel ladle	Steel ladle	Steel ladle
Al2O3 %	90	≥65	≥70	75.6	≥60
F·C %	4.7	4.7	≥7	4.87	/
Fe2O3 %	/	1.60	ZrO2≥6	/	/
Apparent porosity %	4.7	/	2	5.7	13.6
Bulk density g/cm3	3.18	/	3.07	2.86	2.40
Crushing strength MPa	112.3	/	117	105.5	65
Modulus of rupture Mpa	/	3.8(1500℃, 3h)
Refractoriness under load(T2) ℃	>1700	/	≥1700	≥1700	/
Reheating linear change rate %	/	Setting time: 60~150min

Item	Up nozzle well block	Well block	Up nozzle	AC sliding gate	AZC sliding gate	Sliding gate mortar
Material	Corundum	High alumina	Chrome corundum	Alumina carbon	Alumina zirconia carbon	Alumina chrome
Al2O3 %	97	81.5	87	93	77.7	84
Cr2O3 %	/	/	10	/	/	4.5
SiO2 %	/	11	/	6.2	/	4
CaO %	2.4	TiO2: 3.3	/	/	/	/
ZrO2 %	/	P2O5: 2.2	P2O5: 2.0	/	6.5	P2O5: 5
C %	/	/	/	9	8.2	/
Apparent porosity %	/	22	17.5	16	9	/
Bulk density g/cm3	3.0	2.75	3.25	2.79	3.07	/
Crushing strength MPa	>50	80	/	>30	200	/
Modulus of rupture Mpa(1450℃)	2.8	/	/	>7	12	/
Refractoriness under load(T2) ℃	/	>1430	>1700	≥1700	/	/
Reheating linear change rate %(1450℃,3h)	/	1.0	/	/	/	/

Main Damage Reasons of Sliding Gate

Carbon boning sliding gate can be oxidized in middle temperature oxidizing condition and lose strength, the surface of sliding gate will be abraded irregularly. It is the main damage reason of sliding gate.
Another damage reason is thermal shock. Sliding gate will endure strong thermal shock and generate great thermal stress, which can induce sliding gate crack or crushing.
The third damage reason is steel liquid scouring and abrasion. Steel liquid flowing speed is very quick, can take away oxide granule and dissolve carbon in sliding gate, so the diameter of sliding gate’s hole is enlarged.

High Oxygen Steel Casting Sliding Gate

For high oxygen steel casting, alumina carbon sliding gate and alumina zirconia carbon sliding gate’s service life can greatly decline. Sliding nozzle system must have good oxidization resistance, good iron oxide corrosion resistance, as well as thermal shock resistance and abrasion resistance. Through numerous research and application cases, alumina magnesia spinel carbon sliding gate, magnesia spinel carbon sliding gate and magnesia carbon sliding gate are tested to have good service life.

High Oxygen Steel Casting Sliding Gate Index

Item	Alumina magnesia spinel carbon sliding gate	Magnesia spinel carbon sliding gate	Magnesia carbon sliding gate
Al2O3 %	80	10	/
MgO %	8	84	89.7
C %	8	5	3.5
Apparent porosity %	6	6	7
Bulk density g/cm3	3.05	2.98	2.78
Crushing strength MPa	150	100	160
Modulus of rupture Mpa(1400℃)	12	15	18
Thermal expansion rate(800℃)	0.90	0.92	0.82

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Dec 10 2018

Silicon Carbide Mullite Bricks

Silicon Carbide Mullite Bricks Description

Silicon carbide mullite bricks are also called high alumina silicon carbide bricks. SiC mullite brick main mineral phase is SiC and mullite. It can be produced by SiC and bauxite clinker. During high temperature application in kilns, silicon carbide can be oxidized and produce SiO2, which can react will Al2O3 to form mullite (3Al2O3·2SiO2).The synthesized mullite can not only enhance brick’s density and strength, but also form protection film to prevent further oxidization of SiC. The un-reacted SiC can enhance thermal shock resistance, abrasion resistance and corrosion resistance of silicon carbide mullite bricks.

Silicon Carbide Mullite Bricks Characteristics

Abrasion Resistance

SiC mullite brick’s principle phases are high rigidity SiC, mullite and corundum, meanwhile, SiC mullite bricks has high structural density, its bulk density is between 2.7 and 3.0g/cm3. So SiC mullite bricks have good abrasion resistance. Silicon carbide mullite brick’s density, strength and abrasion resistance is significantly better than high alumina bricks and magnesia alumina spinel bricks.

Spalling Resistance And Thermal Shock Resistance

SiC in silicon carbide mullite bricks has high thermal conductivity, small thermal expansion rate, so SiC carbide mullite bricks have good thermal stability, max. thermal shock times can reach to 46 times(1100℃, water cooling).

Insulating Performance

Silicon carbide mullite brick’s thermal conductivity(≤2.3W·(m·K) is lower than spinel bricks, and thus have better heat preservation effect.

High Temperature Performance

SiC mullite brick’s refractoriness under load is above 1500℃, max. is 1690℃, can endure high temperature impact and won’t soften or deform.

SiC Mullite Bricks Physiochemical Index

Item	GM1650	GM1600	GM1550	GM1680
Al2O3 %	63	60	57	63
SiO2+SiC %	30	30	30	30
Apparent porosity %	17	17	19	17
Cold crushing strength Mpa	85	90	90	100
Refractoriness under load ℃ (0.2Mpa)	1650	1600	1550	1680
Thermal shock resistance(11oo℃, water cooling)	10	10	12	13
Bulk density g/cm3	2.65	2.60	2.55	2.65
Cold abrasion resistance cm3	5	5	5	5
Thermal conductivity(w/m·k)	1.7	1.7	1.7	1.7

Silicon Carbide Mullite Bricks Application

Due to silicon carbide mullite brick’s good abrasion resistance, high refractoriness and thermal shock resistance, it is popularly used in rotary cement kiln sintering zone, transition zone and so on, where material rolling friction, high temperature thermal stress, temperature fluctuation and material corrosion are severe.

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Dec 10 2018

Submerged Nozzle

Submerged Nozzle Description

Submerged nozzle ‘s top end connects to the bottom of tundish, bottom end extends into crystallizer, so steel liquid flows from tundish won’t expose to air. The advantages of submerged nozzle are: avoiding steel liquid splashing, reducing impurity entry and protecting steel liquid from oxidization.

Submerged nozzle’s working condition is very harsh, such as very strong thermal shock, steel liquid scouring and erosion, crystallizer protection slag intense corrosion. As protection slag is low melting point, low viscosity material which contains strong corrosive fluorite, K oxide and Na oxide, its corrosion to submerged nozzle is severer than long nozzle, submerged nozzle’s technical requirement is much higher than elongated nozzle.

Submerged Nozzle Types

Silica submerged nozzle is primary used in steel mills, but the corrosion rate is very quick, can only be used in those with lower continuous casting times. Quartz submerged nozzle is not suitable for high continuous casting level or special steel continuous casting mills. Composite submerged nozzle is improved on basis of molten quartz nozzle, slag line adopts composite refractory which has better corrosion resistance to improve service life.

To meet the quick development of continuous casting technique, alumina carbon submerged nozzle is designed. Its service life is significantly prolonged, but thermal shock resistance of alumina carbon submerged nozzle is not very good. To meet thermal shock resistance, some ratio of mullite and molten quartz are added into alumina carbon submerged nozzle. Composite submerged nozzle, such as alumina zirconia carbon submerged nozzle, zirconium boride submerged nozzle are developed, which have good slag corrosion resistance and steel liquid corrosion resistance.

Submerged Nozzle Physiochemical Index

Item	Composite submerged nozzle-1			Composite submerged nozzle-2		Quartz submerged nozzle
Item	Main body	Slag line	Purging part	Main body	Slag line	Quartz submerged nozzle
Material	Al2O3-C	ZrO2-C	Al2O3-C	Al2O3-C	ZrO2-C	Quartz
Al2O3 %≥	48	/	80	45	/	/
C %≥	30	15	15	20	12	/
ZrO2%	/	77	/	/	80	/
SiO2 %	≤15	/	/	≤20	/	≥99
Apparent porosity %≤	17	18	/	20	18	19
Cold compression strength Mpa ≥	17	/	/	16	/	40
Cold rupture strength Mpa	≥6	/	/	≥4	/	/
Thermal shock resistance/ times	≥5	/	/	≥5	/	≥5

For aluminum killed steel casting, nozzle will be blocked by clots, so argon blowing method can be used to avoid this problem, inner lining of submerged nozzle can adopt carbon free refractory and calcium zirconate to get better performance. Submerged nozzle also has another important problem, i.e., surface oxidation, which can make submerged nozzle lose structural strength and damaged. So, a layer of anti-oxidation material can be coated to the surface of submerged nozzle.

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Dec 7 2018

Continuous Casting System Stopper

Continuous Casting System Stopper description

Continuous casting system stopper is installed above tapping nozzle. Through adjusting the gap between stopper and nozzle, steel liquid flowing speed can be controlled. The earliest sleeve bricks of stopper are high alumina bricks or clay bricks. Stopper end is made by alumina carbon refractory. They need to assemble with steel structural controlling rod for using. The service life of combined stopper is not very high, usually less than 6 hours. The main damage reasons of stopper are: On one hand, steel structure is softened in long term high temperature environment and loses controlling effect, on the other hand, sleeve brick is corroded too quickly. To solve this problem, steel controlling rod should have good high temperature performance, sleeve brick should have excellent corrosion resistance and stopper end should properly match with nozzle bowl part.

Another method to solve the problem of combined stopper’s low service life is adopting integral stopper, i.e., alumina carbon integral stopper. Alumina carbon integral stopper is made by isostatic pressing molding, solidifying, mechanical processing and carbonizing, there is no metal rod in alumina carbon stopper and avoids the problem of metal rod softening. The service life of alumina carbon integral stopper can reach to 10h. But stopper end and nozzle bowl part will be scoured irregular and not smooth, it will cause difficulty for flow speed control, or even can’t close. That is key factor constraining the service life of alumina carbon stopper.

Continuous Casting System Stopper Physiochemical Index

Item		Chemical composition (w %)					Cold CS/Mpa ≥	Apparent porosity % ≤	High Temp. rupture strength Mpa	Thermal shock resistance /times
Item		Al2O3 ≥	C≥	ZrO2	SiO2	MgO	Cold CS/Mpa ≥	Apparent porosity % ≤	High Temp. rupture strength Mpa	Thermal shock resistance /times
Integral stopper		60	25	/	/	/	16	19	≥5	≥5
Integral stopper		55	23	/	/	/	15	/	≥4	≥5
Combined stopper	Sleeve brick	60	/	/	≤30	/	40	18	/	≥20
	Sleeve brick	42	/	/	≤52	/	40	18	/	≥20
	Stopper end	80	10	/	/	/	40	18	≥12	/
	Stopper end	75	10	≥6~9	/	/	40	6	≥12	/
Composite stopper	Main body	60	25	/	/	/	16	19	≥5	≥5
	Slag line	/	14	/	/	80	30	5	≥10	/
	Slag line	75	10	≥6~9	/	/	25	10	≥8	/
	End	/	5	≥90	/	/	/	/	/	/
	End	85	5	/	/	/	/	/	/	/

Continuous Casting System Stopper applications

For steel mills using converter to produce ordinary construction steel , steel liquid supply is sufficient, it needs the long service life of stopper, the longer the better. For steel mills producing special steel, different types of steel have different corrosion to stopper, so stoppers which can resist different kinds of steel liquid corrosion is needed. For this reason, slag line part of stopper adopts magnesia carbon refractory, stopper end part adopts alumina zirconia carbon refractory.

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Dec 7 2018

Iron Trough Castable

Iron Trough Castable Description

Different iron smelting factories have different design of blast furnace iron troughs, such as iron storing trough and non storing iron trough, single iron trough and multi iron troughs. Blast furnace iron troughs can also be divided into main trough, branch channel, swing channel and slag channel. Different types of refractory materials can be used as per the types of iron troughs. Iron storing troughs in middle and large scale steel mills usually adopt Al-Si-C series castable.

Iron Trough Castable Characteristics

Blast furnace iron trough should endure iron liquid and molten slag intense scouring, high temperature iron liquid and molten slag chemical corrosion & permeation. So iron trough and slag trough castable should have enough mechanical strength and corrosion resistance. Once there is damage in the trough, it should be patched as soon as possible, which requires iron trough castable has good flowability, few water addition quantity and can be quickly dried. Besides, iron trough lining’s temperature fluctuates greatly, so iron trough castable should also has excellent thermal shock resistance.

Iron Trough Castable Physiochemical Index

Item	DCTC-1	DCTC-2	DCTC-3	DCTC-4
Material	Alumina silicon carbide carbon castable	Alumina silicon carbide carbon castable	Alumina silicon carbide carbon castable	High alumina silicon carbide castable
Application	Main trough slag line	Main trough iron line	Main trough iron line	Main trough slag line
Al2O3 %	60	83	77	56.9
SiC %	37	12	11	32
SiO2 %	2.5	2.5	/	/
C %	1~3	1~3	2	2
Bulk density g/cm3(1450℃,3h)	2.78	2.98	2.84	2.69
Compression strength Mpa(1450℃,3h)	50	50	35.8	/
Reheating linear change rate %(1450℃,2h)	-0.2~0.6	-0.2~0.6	-0.2~0.6	-0.1~0.2

Item	DCTC-5	DCTC-6	DCTC-7	DCTC-8
Material	Alumina silicon carbide carbon castable	Alumina silicon carbide carbon castable	High alumina silicon carbide castable	High alumina silicon carbide castable
Application	Main trough cover top	Main trough cover sides	Iron trough	Slag trough
Al2O3 %	65.3	67.1	49.1	60.4
SiC %	15	15	9.33	14
SiO2 %	/	/	/	/
C %	/	/	/	1~3
Bulk density g/cm3(1450℃,3h)	2.78	2.98	2.84	2.69
Compression strength Mpa(1400℃,3h)	2.52	2.56	2.38	2.68
Reheating linear change rate %(1400℃,3h)	0.22	±0.35	-0.12	±0.5

So alumina silicon carbide carbon castable is mainly used for the casting of blast furnace iron trough. Alumina silicon carbide carbon castable’s main materials are fused corundum(or sintered corundum, special grade bauxite clinker), graphite contains 90%~95% fixed carbon, silicon carbide and so on. During construction, additives should be added and fully mixed before casting. For slag trough, lower grade of alumina silicon carbide carbon castable can be used, It can not only meet production requirement but also has better economic benefits. High alumina silicon carbide castable, which has excellent abrasion resistance is the best choice for slag line.

In recent years, quick dry Al-SiC-C castable is developed for casting houses which only have one iron running trough. The development of self flow Al-Si-C castable brings lots of convenience for casting construction. The unit refractory consumption of per ton iron is significantly decreased with the improvement of castable quality.

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Dec 6 2018

Non-Stick Aluminum Castable

Non-Stick Aluminum Castable Description

Non-stick aluminum castable is mainly used in aluminum smelting furnace, aluminum press casting heat preserving furnace and so on. Although the melting point of aluminum is not high, only about 660℃, aluminum liquid has low viscosity, high permeation ability and high activation property, which makes it have drastic corrosion to refractory furnace lining.

The Damage Mechanism Of Refractory Lining

Aluminum liquid can react with SiO2 in Al2O3-SiO2 series refractory material and produce Al2O3+Si. So the structure of Al2O3-SiO2 refractory will be destroyed, meanwhile, impurity Si will also contaminate aluminum liquid.
Aluminum liquid can infiltrate into refractory material pores, increases the contacting area of refractory material and change the composition. When the infiltration reaches to a certain depth, accompanied with the reaction of aluminum and SiO2, refractory material will have structural spalling.

Non Stick Aluminum Castable Property

To solve this problem, refractory material contacting with aluminum liquid should adopt non-stick aluminum castable. Non-stick aluminum castable has high density(low porosity), good high temperature, middle temperature and room temperature strength, and the strength is positively correlated to temperature. Meanwhile, non-stick aluminum furnace castable has good volume stability at different temperature. With the addition of ultra micro powder component, the porosity of non-stick aluminum processing castable is lower than 10%, the average pore aperture is only 0.5μm. So aluminum liquid can’t permeate into non-stick aluminum castable lining. What’s more, composite additives added in castable can increase aluminum liquid’s contact angle with castable lining and significantly strengthen lining’s aluminum liquid permeation resistance.

Non-Stick Aluminum Castable Physiochemical Index

Item		BZL-1	BZL -1A	BZL-M	BZL-F	BZL-G
Chemical composition	Al2O3≥	60	65	65	70	80
	Fe2O3≤	0.6	0.5	0.4	0.4	0.3
	BaO+ZnO+B2O3≥	3	3	3	4	4
Bulk density g/cm3≥		2.4	2.5	2.65	2.7	2.8
Compression strength Mpa≥	110℃*24h	35	40	40	45	45
	1300℃*16h	40	45	45	50	50
Rupture strength Mpa≥	110℃*24h	5	10	10	12	14
	1300℃*16h	10	13	13	15	16
Linear change rate % (1300℃*3h)		0～+0.2	0～+0.2	0～+0.2	0～+0.1	0～+0.1

Non-Stick Aluminum Castable Application

Non-stick aluminum castable is specially developed for aluminum processing industry, it is mainly used in aluminum melting furnace wall, furnace bottom, degassing tank, launder and fore-tank. No stick aluminum castable is also used for the furnace lining of keeping furnace, aluminum liquid heat preserving furnace, aluminum ladle and so on. Especially suitable for the integral casting of heat preserving furnace and lining of high purity aluminum smelting equipment. Non-stick aluminum castable synthesizes the characteristics of organic binders and inorganic binders, added in certain quantity of new type composite material, can effectively avoid the infiltration of aluminum liquid and significantly prolong the service life of refractory castable lining.

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Dec 6 2018

Coating Resistant Silicon Carbide Castable

Coating Resistant Silicon Carbide Castable Description

Silicon carbide castable is also call coating resistant silicon carbide castable. It takes SiC as main raw material, pure calcium aluminate cement as binder, added with high efficient water reducing agent and ultra micro powder. Silicon carbide is high grade synthesized refractory material, has a wide range of application in refractory industry. Due to its particular characteristic, SiC has very low adhesion ability with cement raw material.

Coating resistant castable’s aggregate mainly compromise low bauxite aggregate, scrap ceramics, scrap electroceramics, SiC and so on. Aluminate cement is usually used as binders of SiC coating resistant castable. Usually, cement raw material is hard to adhere to the surface of SiC castable, so the chance of cement raw material agglomeration at kiln tail is greatly decreased. The application of silicon carbide castable in cement kiln, can avoid the coating of cement in kiln, so the output of cement production line will raise correspondingly.

Coating Resistant Silicon Carbide Castable properties

Coating resistant SiC castable has good abrasion resistance and corrosion resistance.

Good high temperature mechanical strength, high thermal conduction coefficient.

Small linear expansion coefficient, excellent thermal shock resistance.

Won’t react with cement raw material.

Silicon carbide castable has good coating resistance, can significantly decrease coating times.

Coating Resistant Silicon Carbide Castable physiochemical index

Item	SiC-30	SiC-50
Al2O3 % ≤	35	25
SiC ≥	30	50
Bulk density g/cm3(110℃,24h)	2.40	2.50
Cold compression strength Mpa (110℃,24h) ≥	80	70
Cold rupture strength Mpa (110℃,24h) ≥	9	8
Permanent linear change rate % (1100℃,3h)	±0.4	±0.4
Alkali resistance grade	I	I
Max. working temperature ℃	1350	1400
Water addition %	6.0~7.0	5.5~6.5

Coating Resistant Silicon Carbide Castable Applications

Based on SiC content, coating resistant SiC castable can be classified into two types: one is SiC-30, which’s SiC content is no less than 30%, the other is SiC-50, which’s SiC content is no less than 50%. Both SiC-30 and SiC-50 SiC castable can be used in places of new type middle large scale dry cement kiln pre-heater feeding slope, ascending flue, decomposing furnace cone and so on, where cement coating is easy to form.

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Dec 5 2018

Tabular corundum castable

Tabular Corundum Castable

Tabular corundum castable is high grade monolithic refractory which is composed of tabular corundum aggregate, fines and high alumina binder. Based on different applications, different kinds of ingredients can be added into tabular corundum castable to enhance its thermal, chemical and mechanical performances. For example, chrome corundum castable which has high refractoriness can be applied in carbon black furnace, coal gasifier lining. zirconia corundum castable which has excellent glass corrosion resistance is suitable for glass kiln. Composite corundum castable with specific composition can be used for various industrial kilns and furnaces such as cement rotary kiln, nonferrous metal smelting furnace, steel industry and so on.

Tabular Corundum Castable Property

High mechanical strength, good abrasion resistance.

Excellent thermal shock resistance, creep resistance.

High refractoriness, good high temperature volume stability.

Excellent Slag corrosion resistance, chemical corrosion resistance.

Convenient for construction, maintenance and patching.

Tabular Corundum Castable Physiochemical Index

Item	Tabular corundum castable	High alumina castable
Model	GYJ-90	GLJ-80
Refractoriness / ℃	1810	1790
Bulk Density / g/cm3 ≥	2.85	2.85
Al2O3 % ≥	90	80
Thermal shock resistance (1100℃) /times ≥	80	70
Alkali resistance >	2	1
110℃ Wear resistance ，≤	6	6
Rupture Strength，(110℃, 3h) Mpa ≥	13	10
Compressive Strength (110℃, 3h) Mpa ≥	110	100

Corundum Castable Application

Corundum castable has a wide range of application in various kinds of industrial kilns and furnaces, one main application of tabular corundum castable is iron and steel industry. For example, for the casting of steel ladle working lining, sliding gate valve and tapping nozzle, long nozzle, submerged nozzle, tornado tank working lining, purging plug, pocket brick, iron runner and the integral casting of electric arc furnace cover triangle zone. Other applications of tabular corundum castable are rotary kiln front mouth, coal injection tube, circulating fluidized bed boiler, RH furnace immersion tube outer lining, petrochemical industry high temperature catalytic cracking reactor working lining, etc.

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Author: aluminabricks

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