aluminabricks, Author at RS Kiln Refractory Bricks

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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Steel industry refractories

Dec 4 2018

RH and DH Refractory

RH is vacuum argon blowing recycling degassing equipment for steel liquid refinery, and DH is vacuum degassing refinery equipment. By blowing high speed argon in immersion tube and vacuum chamber upper part, steel liquid in ladle will flow into bottom side of vacuum chamber and be degassed, and then flow back to ladle through the other dipping tube. Through vacuum recycling degassing, harmful gases such as nitrogen, hydrogen in steel liquid can be removed. If oxygen blowing is adopted, carbon content can be decreased to a very low extent. RH and DH refinery equipments are mainly used for low carbon steel, low nitrogen steel and low hydrogen steel. Under those working conditions, furnace lining refractory materials should have good scouring resistance, vacuum resistance and thermal shock resistance.

RH refinery

In concern of cleaning steel production, refractory materials should better contain no carbon, nitrogen and hydrogen. Usually, vacuum chamber can use magnesia chrome bricks, inner side of immersion tube can use magnesia chrome bricks, while the outer side can adopt alumina magnesia spinel castable. The service life of magnesia chrome bricks at vacuum chamber upper part can reach to 2000 times or more, but the lower part is only about 500 times. The service life of immersion tube is about 100 times, varies with working condition and maintenance quality.

RH furnace structure

Magnesia alumina spinel bricks can be a good replacement of magnesia chrome bricks, but the corrosion resistance is not as good as magnesia chrome bricks. Another replacement of magnesia chrome bricks is low carbon magnesia carbon bricks, which has good performance price ratio compared with MgO-Cr2O3 bricks. RH immersion tube can be integrally casted by magnesia alumina spinel castable or magnesia zirconia castable. Through patching, the service life of integrally casted immersion tube can reach to or exceed magnesia chrome bricks lining.

RH Refractory Material Physiochemical Index

Item	Basic mortar	Alumina magnesia castable	Insulating brick	Calcium silicate board	Direct bonded magnesia chrome brick
Application	Masonry of magnesia chrome brick	Immersion tube, vacuum chamber upper part	Vent pipe, vacuum chamber	Vacuum chamber	Vacuum chamber
MgO %	92	>2	/	/	80
Al2O3%	/	>90	51.2	/	/
Fe2O3 %	/	/	1.7	/	/
Cr2O3 %	/	/	/	/	6~13
SiO2 %	/	/	/	/	1.98
Apparent porosity %	/	/	/	/	15
Bulk density g/cm3	/	≥2.90	≤0.9	0.23	3.06
Compression strength Mpa	/	≥40(11o℃)	7.37	≥0.5	59.2
Rupture strength Mpa	/	≥8.4(110℃,24h)	/	0.52	≥6.0(1200℃)
Reheating linear change rate %	/	±0.5(1500℃,3h)	-0.43	1.5 (1500℃,3h)	/
Refractoriness ℃	>1790	>1790	/	Max.1000	/

Item	Magnesia gunning mix	Magnesia chrome gunning mix	Magnesia injection mix	Magnesia carbon brick	Magnesia spinel precast block
Application	Vacuum chamber lower part, immersion tube	Immersion tube, vacuum chamber upper part	Immersion tube, vacuum chamber upper part	Vacuum chamber lower part, immersion tube	Vacuum chamber lower part, immersion tube
MgO %	≥85	≥70	≥70	≥85	80
Al2O3%	/	4	3	F.C≤5	10
Fe2O3 %	/	≤5	≤5	/	/
Cr2O3 %	/	≥5	≥5	/	/
SiO2 %	≤6	≤4	≤5	/	≤2
Apparent porosity %	≤24	≤24	≤24	≤4	≤15
Bulk density g/cm3	≥2.2	≥2.3	≥2.4	≥3.10	3.06
Compression strength Mpa	≥25 (11o℃)	≥20(11o℃)	≥20(1600℃,3h)	≥30 (11o℃)	≥40 (11o℃)

Item	Magnesia chrome brick	Magnesia chrome brick	Magnesia chrome brick	High alumina castable	Direct bonded magnesia chrome brick
Application	RH vacuum chamber upper part	RH lower part, recycling tube and immersion tube	OB gunning machine for RH	Vacuum chamber	Immersion tube
MgO %	80	76.9	69.9	/	65
Al2O3%	/	/	/	92.8	/
Fe2O3 %	/	/	/	/	/
Cr2O3 %	8.4	10.9	18.67	/	19
SiO2 %	1.6	1.46	1.52	/	≤2
Apparent porosity %	16	15	15	/	15
Bulk density g/cm3	3.05	3.11	3.00	2.79(1500℃,3h)	≥3.12
Compression strength Mpa	60	66	61	≥30(1500℃,3h)	60
Rupture strength Mpa (1480℃)	10	7.6	9.1	≥8.4（110℃）	60
Reheating linear change rate %	/	/	/	-0.27 (1500℃,3h)	-0.27 (1500℃,3h)
Refractoriness under load ℃	>1650	>1700	>1700	/	>1700

Item	RH gunning mix	RH injecting mix	CAS immersion tube castable	KIP spray gun castable
Application	Masonry of magnesia chrome brick	Immersion tube, vacuum chamber upper part	Vent pipe, vacuum chamber	Vacuum chamber
MgO %	/	/	≥4	/
Al2O3%	≥92	≥92	≥87	≥95
Refractoriness ℃	>1790	>1790	/	/
Bulk density g/cm3(110℃,24h)	≥2.90	≥2.60	≥2.95	≥3.00
Compression strength Mpa(1500℃,3h)	≥50	/	≥40	/
Rupture strength Mpa (110℃,24h)	≥4.0	≥4.0	/	≥4.0
Linear change rate %(1500℃,3h)	±1.0	±1.0	/	0~2.0

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Steel industry refractories

Dec 4 2018

Nozzle Refractory For Continuous Casting System

Nozzle Refractory Description

Nozzle series refractory can be divided into long nozzle, metering nozzle, submerged nozzle and separation ring.

Long Nozzle

Long nozzle is the connection part between steel ladle and tundish. Head end of long nozzle connects to steel ladle down nozzle, bottom end embeds into tundish steel liquid. Long nozzle can keep steel liquid from contacting with air during transferring from ladle to tundish, so steel liquid won’t splash, impurity won’t enter into steel liquid. The working condition suggests that long nozzle should not only endure strong thermal shock, steel liquid scouring and corrosion, but also suffer the corrosion of tundish cover flux. With the increasing requirement on steel quality, protecting casting ratio is continuously growing, so long nozzles using ratio is surging.

elongated nozzle

Quartz long nozzle is earliest used, which has very low linear expansion rate or nearly no thermal expansion, excellent thermal shock resistance, but it’s corrosion resistance is weak, especially for the casting of special steel such as high Mn steel, the service life is even shorter. With the developing of continuous casting technique, especially the casting of special steel, quartz long nozzle can also have unfavorable effect on steel quality, so new type of alumina carbon long nozzle is developed. Alumina carbon long nozzle’s service life is significantly longer than quartz long nozzle, but alumina carbon long nozzle’s main components are corundum, mullite, graphite and molten quartz, although mullite and quartz can large scale increase thermal shock resistance, the corrosion resistance to Mn steel and other special steel is not very good.

long nozzle

To solve this problem, composite long nozzle is developed, i.e., slag line magnesia carbon material, zirconia carbon material, main body adopts alumina zirconia carbon material, to meet low carbon steel casting needs, inner layer adopts alumina magnesia and Sialon ceramic carbon free material.

In recent years, unshaped long nozzle is also developed. Casting molding method is used to replace isostatic pressing molding for the production of alumina carbon quartz long nozzle and alumina magnesia long nozzle.

Long Nozzle Physiochemical Index

Item	Alumina carbon long nozzle	Alumina carbon long nozzle		Quartz nozzle	Quartz nozzle	Al2O3-C long nozzle
Item	Alumina carbon long nozzle	Main body	Purging ring	Quartz nozzle	Quartz nozzle	Al2O3-C long nozzle
Al2O3 %	43.81	≥40	≥85	/	/	≥50
F．C %	30.65	≥27	/	/	/	≥25
SiO2 %	/	/	/	≥99	≥99	/
Bulk density g/cm3	2.24	/	/	≥1.82	≥1.84	/
Apparent porosity %	17	≤20	/	≤19	≤18	12~20
Compression strength Mpa	25.2	≥20	/	≥40	≥40	≥15
Rupture strength Mpa	7.82	≥6	/	/	/	≥4
Air flow rate L/min	229	/	100	/	/	/
Thermal shock resistance/times	229	/	100	/	/	/

Item	Alumina carbon quartz long nozzle	Alumina magnesia carbon long nozzle		Alumina zirconia carbon long nozzle	Alumina carbon long nozzle
Item	Alumina carbon quartz long nozzle	Main body	Slag line	Alumina zirconia carbon long nozzle	Main body	Purging part
Material	Alumina carbon	Alumina carbon	Magnesia carbon	Alumina zirconia carbon	Alumina carbon compound	Alumina carbon compound
Al2O3 %	50	≥40	MgO, 74	≥40	50	90
F．C %	30	≥27	25	≥27	31	/
SiO2 %	14	/	/	/	/	/
ZrO2 %	/	/	/	6~10	/	/
Bulk density g/cm3	2.50	2.38	2.40	≥2.50	2.25	/
Apparent porosity %	14	≤20	16	≤18	17	/
Compression strength Mpa	/	≥20	/	≥20	24.4	/
Rupture strength Mpa	/	≥6	/	≥6	/	/
Air flow rate L/min(0.1Mpa)	/	/	/	/	/	210
Thermal shock resistance/times	/	≥5	/	≥5	5	/

Metering Nozzle

Metering nozzle is mainly used for the continuous casting of small billet. It is installed at the bottom of tundish. Metering nozzle should not have diameter enlargement or erosion under the strong scouring and corrosion of steel liquid. Inserting metering nozzle’s inner layer is made from zirconia ceramic refractory, which has excellent performance, outer layer is made from high alumina refractory. Inserting metering nozzle’s performance cost ratio is very high, so is popularly used. Integral metering nozzle is made by single type of refractory material, but performance cost ratio is not so high as inserting type metering nozzle. Worthy to be mentioned is that, a lot of steel mills insert pocket bricks and metering nozzles together and form a whole body, which is convenient for construction and safer for production.

metering nozzle

To prolong metering nozzle’s service life, zirconia content and zirconia ceramic’s density should be improved. The content of zirconia is raised from 65% to 94%, the density is increased from 3.4g/cm3 to 5.0g/cm3. To improve thermal shock resistance, semi stable zirconia is usually adopted, CaO is used as stabilizer.

zirconia metering nozzle

Metering Nozzle Physiochemical Index

Item	DJ-65	DJ-70	DJ-75	DJ-80	Zirconia metering nozzle	Zirconia metering nozzle	WG-70	WG-80
Position	Whole body and inner core						Outer layer and pocket block
ZrO2%≥	65	70	75	80	90	94	/	/
Al2O3 %	/	/	/	/	/	/	≥70	≥80
Apparent porosity% ≤	20	21	21	22	22	23	19	19
Bulk densityg/cm3≥	3.70	3.75	3.90	4.10	4.30	4.50	2.60	2.80

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Dec 3 2018

LF-VD Furnace Refractory Material

LV-VD furnace is steel liquid refinery equipment, which’s working condition is very harsh, should endure all kinds of high temperature corrosion, chemical corrosion, mechanical stress and thermal stress. So high quality refractory products should be adopted in according parts of LF-VD furnaces.
Magnesia carbon bricks are mainly used at furnace bottom and working lining. Corundum precast block which has high mechanical strength is mainly used at furnace bottom impacting zone. Magnesia chrome ramming mass is mainly used at furnace wall corner. Magnesia chrome mortar can be used for the masonry of magnesia chrome bricks.

LF-VD Furnace Refractory Material Physiochemical Index

Name	Magnesia carbon brick	Corundum precast block	Magnesia mortar	Magnesia chrome ramming mass	Magnesia carbon brick
Application	Bottom, wall working lining	Bottom impacting zone	Steel ladle working lining	Wall corner	Below slag line, free surface working lining
MgO %	92.5	/	96	52	92.5
CaO %	2.5	/	2.2	Cr2O3,19	2.5
Fe2O3 %	4	/	0.3	19	4
SiO2 %	/	/	1	0.5	0.6
Al2O3 %≥	/	97	/	6	/
F.C % ≥	5	/	/	/	10
Apparent porosity %	≤7	/	/	/	<7
Bulk density g/cm3 ≥	3.07	2.98	/	/	2.98
Compression strength Mpa	>.40	80	/	25(110℃)	>30

Name	Magnesia carbon brick	Magnesia chrome brick	Magnesia chrome mortar	Magnesia castable (ramming mass)	Chrome silica ladle filler sand
Application	Slag line working lining	Slag line permanent lining	Magnesia chrome brick	Ladle nozzle	Tapping hole
MgO %	96	60	52	91	6~12
CaO %	2.3	Cr2O3, 18	Cr2O3, 19	2.0	Cr2O3 >30
Fe2O3 %	0.3	14	19	5.8	20
SiO2 %	1.2	0.5	0.5	0.5	30
Al2O3 %≥	/	6	6	0.3	5~10
F.C % ≥	10	/	/	/	/
Apparent porosity %	≤7	<15	/	/	/
Bulk density g/cm3 ≥	3.00	3.26	/	/	/
Compression strength Mpa	>30	>30	/	30(110℃)	/

Name	Corundum block	Magnesia block	Corundum brick	Magnesia brick	Corundum mullite brick
Application	Purging plug, sleeve brick, pocket block	Purging plug, sleeve brick, pocket block	Purging plug, sleeve brick, pocket block	Dispersive type Purging plug	Purging plug core plate
MgO %	/	97	/	97	/
CaO %	1.8	1.7	2.4	1.9	/
Fe2O3 %	/	/	/	/	/
SiO2 %	0.1	0.6	0.1	0.5	9
Al2O3 %≥	88	/	97	/	90
F.C % ≥	/	/	/	/	/
Apparent porosity %	/	<25	/	26	/
Bulk density g/cm3 ≥	3.22	2.75	3.00	2.60	2.95
Compression strength Mpa	>60	>30	>50	>30	>60
Thermal conductivity w.(m.K)^-1(1000℃)	/	3.0	2.8	3.0	/

Name	Alumina magnesia castable	Alumina chrome castable	Corundum castable	Magnesia chrome castable	Alumina chrome chamotte
Application	Purging brick surrounding	Purging brick surrounding	Purging brick surrounding	Lower Dispersive purging brick	Purging brick
MgO %	8	/	/	77	/
CaO %	1	1.8	2.4	/	/
Cr2O3 %	/	10	/	12	2.0
SiO2 %	0.1	/	0.1	/	7
Al2O3 %≥	88	88	97	/	84
F.C % ≥	/	/	/	/	/
Apparent porosity %	/	/	/	26	/
Bulk density g/cm3 ≥	3.00	3.22	3.00	2.60	/
Compression strength Mpa	>60	>60	>50	>30	/
Rupture strength Mpa(1400℃)	12	15	8	/	/

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Nov 28 2018

VOD Furnace Refractory Material

VOD Furnace Introduction

VOD is the acronym of vacuum oxygen de-carbonization, i.e., steel liquid vacuum degassing, oxygen blowing de-carbonization treatment can be carried out in VOD refinery furnace. Oxygen blowing VOD furnace’s temperature can be higher than 1700℃, desulfurization and reduction reaction are also carried out in VOD furnace, slag alkalinity will change greatly, high smelting temperature and vacuum atmosphere will also do huge damage to furnace lining refractory material. Therefore, VOD furnace should adopt high grade refractory material.

VOD Furnace Refractory Materials

VOD slag line: Slag line zone usually adopts re-bonding magnesia chrome bricks or pre-reaction magnesia chrome bricks. Ladle wall can use low grade magnesia chrome bricks. Although magnesia chrome bricks can prolong VOD furnace’s service life, but the production cost is high. So in Europe, where dolomite refractory is abundant, VOD furnace slag line zone mainly adopts ultra high temperature sintered magnesia dolomite bricks. Furnace wall can choose lower grade sintered magnesia dolomite bricks or pitch binding unburned magnesia dolomite bricks. Magnesia dolomite refractory lining’s service life is slightly shorter than magnesia chrome refractory lining, but steel smelting cost is significantly decreased, it can bring in good economic benefits.

Below slag line: With the development of magnesia carbon bricks, for furnace body, below slag line, low carbon content magnesia carbon bricks or magnesia dolomite carbon bricks become a reasonable choice, VOD molten bath’s service life can reach to 40 times or more. After proper maintenance or patching, molten bath’s service life can be higher than 60 times. Another developing trend of molten bath refractory material is alumina magnesia castable or precast block, it can ultimately eliminate carbon in furnace lining caused adverse effect.

Cr Free Refractory Bricks for VOD Furnace

Cr2O3 in magnesia chrome bricks will finally be oxidized into Cr6⁺, which has great environment pollution, so magnesia chrome bricks’ application is constrained. Ultra high temperature sintered high purity magnesia dolomite brick is a good replacement of slag line magnesia chrome bricks. Molten bath can adopt low carbon magnesia carbon bricks or low carbon magnesia dolomite carbon bricks.

VOD Furnace Refractories Physiochemical Index

Item	High alumina spinel castable	High alumina castable	Direct binding dolomite brick	Direct binding magnesia dolomite brick	Resin binding dolomite carbon brick	Resin binding magnesia dolomite carbon brick
Application	Ladle cover	Vacuum cover	Molten bath	Molten bath, slag line	Slag line, molten bath	Slag line, molten bath
Al2O3%	92	70	/	/	/	/
SiO2 %	/	22	/	/	/	/
TiO2 %	/	2.8	/	/	/	/
MgO %	5	/	41	59	43	65
CaO %	2	3	57	39	55	33
C %	/	/	/	/	<3	<5
Bulk density g/cm3	3.0	2.80	2.82	3.00	2.94	2.92
Apparent porosity %	/	/	<17	<13	<5	<5
Compression strength Mpa	/	/	65	60	>60	>60

Item	Alumina chrome precast block	Corundum precast block	Magnesia chrome brick	Magnesia chrome brick	Unburned corundum spinel brick	Magnesia chrome joint material
Application	Ladle cover	Ladle cover	Slag line, molten bath	Molten bath, slag line	Molten bath	Magnesia chrome bricks lining
Al2O3%	92	94	<6	<6	>90	<7
Cr2O3 %	>3	/	18~23	12~18	/	18~23
Fe2O3%	/	/	<12	<12	/	<12
SiO2 %	/	/	<1.5	<1.5	/	<1.5
MgO %	/	/	>60	>65	6~12	>55
CaO %	2	2	/	/	/	/
Bulk density g/cm3	3.0	3.0	>3.15	>3.10	>3.05	>2.80
Apparent porosity %	<15	<15	<17	<17	<15	/
Compression strength Mpa	>30	>40	>35	>40	>40	>20

Item	Magnesia spinel bricks	Alumina magnesia castable	Alumina magnesia precast block	Low carbon magnesia carbon brick	Magnesia chrome gunning mix	Magnesia chrome gunning mix
Application	Molten bath	Molten bath	Molten bath	Molten bath, slag line	Molten bath, slag line	Molten bath, slag line
Al2O3%	8~12	>90	>90	/	<8	<8
Cr2O3 %	/	/	/	/	18~23	12~18
Fe2O3%	/	/	/	/	<12	<12
SiO2 %	/	/	/	/	<3	<3
MgO %	>80	4~8	4~8	>90	>55	>55
CaO %	/	<2	<2	/	/	/
C %	/	/	/	<5	/	/
Bulk density g/cm3	>2.90	>3.00	>3.00	>3.05	>2.50	>2.40
Apparent porosity %	<15	<15	<15	<5	/	/
Compression strength Mpa	>60	>30	>30	>80	>10	>10

Item	Magnesia calcia gunning mix	Dolomite gunning mix	Magnesia gunning mix	Magnesia calcia joint material
Application	Magnesia calcia lining	Magnesia calcia lining	Magnesia calcia and magnesia chrome lining	Magnesia calcia brick lining
MgO %	40	65	>92	43
CaO %	50	25	/	55
SiO2 %	<3	<3	<3	<3
C %	/	/	/	<5
Bulk density g/cm3	>2.40	>2.40	>2.40	>2.80
Compression strength Mpa	>20	>25	>25	>30

Methods for Prolonging VOD Furnace Lining Service Life

Apart from choosing high grade furnace lining refractory material, the following methods can be taken to prolong VOD furnace’s service life.

Improve smelting condition. Dolomite slag making method and properly decreases smelting temperature are effective measures to prolong furnace lining service life. Speeding up turnover speed and enhancing heat preservation can also significantly prolong furnace lining service life.

2. Enhancing furnace protection and furnace patching. Usually, gunning mix which has same composition with lining bricks are adopted for furnace lining patching. For example, magnesia chrome bricks lining should be patched by magnesia chrome gunning mix, magnesia dolomite bricks lining should be patched by magnesia calcia gunning mix.

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Nov 28 2018

Factors Affecting VOD Furnace Refractories Serving Life

AOD furnace smelting temperature is very high, acid slag and basic slag are formed in different smelting period, meanwhile, fierce gas fluxing is occurred during oxygen blowing. Under synthesized action of various smelting conditions, AOD furnace lining refractories will be damaged gradually.

Factors Affect AOD Furnace Lining Refractories Service Life

Rebinding magnesia chrome bricks is easier to be corroded with the increasement of slag alkalinity. Service life is longest when slag alkalinity is between 1.2~1.5.
The higher MgO, Cr2O3 and Al2O3 ratio is in slag, the slower magnesia chrome bricks corrosion rate will be.
Reductant is apt to react with Cr2O3 and FeOn in magnesia chrome bricks, thus bricks’ structure is destroyed and brick grains will be scoured by steel liquid. Cr content in steel liquid is also hard to be controlled.
During smelting Al/Si killed steel, Al killed steel will have lower refractory material corrosion rate than Si killed steel. Because Si and Mn in alloy steel will increase corrosion rate of refractory lining.
Between 1600℃~1750℃, per increasement of 100℃, magnesia chrome refractory material’s dissolving rate will increase 4~5 times, while magnesia calcia refractory will increase 2~3 times.
Magnesia chrome bricks will suffer smelting atmosphere influence, Cr and Fe in magnesia chrome bricks will have valance alternation and generate large volume change effect, brick’s structure is destroyed.
Fluorite in slag and Al2O3 will react with magnesia calcia brick and form low viscosity, low melting point eutectics, so corrosion rate is accelerated.
Magnesia calcia material has better low basicity slag corrosion resistance than magnesia material, while MgO refractory has better high Al2O3 slag or high iron slag corrosion resistance than magnesia calcia refractory.
Air blowing angle will have great influence on corrosion rate, generally, back angle of inclination is between 5°~7°.
For low alkalinity slag, magnesia chrome bricks have better corrosion resistance than magnesia calcia bricks, for high alkalinity slag, magnesia calcia bricks have better corrosion resistance than magnesia chrome bricks.
The dissolution rate of magnesia chrome refractory and magnesia calcia refractory in acid slag is in proportion to the 0.7 power of rotation speed.
When slag alkalinity is less than 1.3, high temperature solid phase magnesia chrome refractory’s slag corrosion resistance ability is Cr2O3>MgO-Cr2O3>MgO>MA>Al2O3.
The lower porosity rate is, the better slag corrosion resistance ability is.
In magnesia calcia bricks, slag permeation resistance and spalling resistance is increased with the increase of MgO content.
The denser raw material is, the evener composition distribution is, the better slag corrosion resistance is.
Rebinding magnesia chrome bricks has poor spalling resistance than direct binding magnesia chrome bricks.
The decrease of Cr2O3 in firebricks will weaken its permeation resistance, crack resistance and corrosion resistance.
The higher sintering temperature is, the slower corrosion rate is.

Measures to Prolong AOD Furnace Lining’s Service Life

Increase MgO and Al2O3 content in slag, when their contents approach saturation state, magnesia chrome brick lining can have a longer service life. Increase MgO and CaO content (dolomite slag making) in slag to a saturation state, magnesia calcia brick lining’s serving life can be prolonged.
Properly decrease smelting temperature is beneficial for prolonging service life.
Speed up smelting tempo, shorten smelting time can contribute to prolonging service life.
Enhancing furnace heat preservation, reducing temperature fluctuation are very important for reducing furnace lining spalling.
Choose high density, high strength and highly direct bonded magnesia chrome bricks and magnesia calcia bricks.
According to operation condition, especially slag alkalinity and interval time to choose corresponding Magnesia chrome bricks and magnesia calcia bricks.

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Nov 27 2018

AOD Furnace Refinery Refractories

With the development of steel smelting technique, there is higher and higher demand on high quality steel. To meet market requirement and clean steel development trend, out-furnace refinery ratio is continuously increasing. Therefore, refractory materials for out-furnace refinery application is developing rapidly.

AOD Furnace Description

AOD furnace is mainly used for stainless steel production. At the beginning, oxygen is blown for oxidized de-carbonization. During oxidization period, slag’s oxidization ability is increasing and temperature can reach to more than 1700℃. Next comes to reduction period, silicon, iron or aluminum is added to reduce chrome in slag, at this period, slag alkalinity is still low. Finally, lime is added to remove sulfur, as desulfurization needs high alkalinity. In the whole smelting process, slag will transform from acid to basic, atmosphere will also change from oxidization to reduction. Because of non-continuous operation, furnace lining temperature is high and has large fluctuation. So AOD furnace lining’s service life is very low, only 30 times or so, by improving smelting condition and gunning patching maintenance, the service life can reach to 70 times or more.

$AOD furnace refractory$

For AOD furnace, earlier, magnesia chrome bricks are widely used. But magnesia chrome bricks requires complicated production craft and ultra high sintering temperature, energy consumption is huge, cost is high, what’s more, magnesia chrome refractory has severe environmental contamination problem, so are gradually replaced by magnesia calcia bricks.

AOD Furnace Lining Damage Reason

The main damage reasons of AOD furnace lining are: 1) permeation and dissolution corrosion caused by high smelting temperature and long acid slag action time. 2) thermal spalling and structural spalling caused by temperature fluctuation. 3) Fierce gas-slag-steel liquid scouring and erosion. 4) Under changing AOD furnace atmosphere, Cr2O3 and FeO_n in magnesia chrome bricks can have oxidization and reduction reaction, which will destroy firebrick’s structure and volume stability.

Tuyere part main damage is thermal spalling and structural spalling, tuyere ambient place mainly suffers eddy and low alkalinity slag corrosion. Slag line’s main damage is high basicity slag permeation caused structural spalling. Furnace bottom’s main damage is high alkalinity slag corrosion and permeation. So, AOD furnace firebricks should have low porosity, high temperature strength, high thermal shock resistance and high slag permeation resistance.

AOD Furnace Lining Refractories

Magnesia calcia bricks have gradually replaced magnesia chrome bricks and are more and more popularly used in AOD furnace linings. Magnesia calcia bricks can be divided into sintered dolomite bricks, pitch binding dolomite bricks, resin binding dolomite bricks and so on. Different grades of dolomite refractory bricks can be used for different parts of AOD furnaces. When smelting temperature is very high, carbon containing refractories will have oxidation and reduction reaction and is not suitable for using. Except for dolomite bricks, magnesia calica lining joint material, magnesia calcia lining gunning mix, magnesia calcia chamotte and so on.

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Author: aluminabricks

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