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What are the types of refractory materials used in ladles?

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This article describes what castables and refractory bricks are used in ladles.

Keywords: ladle; castable; refractory bricks

A ladle is an important container in the metallurgical industry, used for storing and transporting molten steel, and performing refining tasks outside the furnace. With the advancement of steelmaking technology, refractory materials for ladles in my country have also seen significant development. The service life of a ladle is crucial as it not only affects the consumption of refractory materials but also directly impacts the normal production of steelmaking.

As the lifespan of converters increases, the continuous casting ratio rises, and out-of-furnace refining technology advances, ladles face increasingly harsh conditions. These include large capacity, multiple steel types, high temperatures, and extended usage times. Consequently, the requirements for refractory materials for ladles are continually improving.

Countries around the world are actively researching and developing new refractory materials to enhance the quality of existing ones. The goal is to extend the service life of refractory materials and reduce the tonnage consumption of these materials.

Introduction to the use of pouring ladles

In my country, ordinary converter ladles with a nominal capacity of less than 50 tons without refining typically have their working linings formed by integral pouring with castables. The one-time service life of the working lining is generally about 50-60 times, with the highest being around 70-80 times, and in some steel plants, even more than 100 times.
To reduce refractory material consumption per ton of steel, many steel mills clean the remaining steel and residue on the ladle working lining after a certain number of uses. This process, known as peeling, involves pouring a certain thickness of castables on a tire mold, drying, and baking it for reuse, which significantly reduces costs. This method is called sleeve pouring.
The residual lining from the first use acts as a permanent lining, lasting for 2-3 services. Ladle working lining materials include alumina-magnesite and high-alumina spinel. Based on the binder, they are categorized into low cement, ultra-low cement, and cement-free refractory castables.

High alumina spinel castable

Since the promotion and application of amorphous refractory materials lined with ladles in the 1980s, the original ordinary aluminum-magnesium castables have been developed into aluminum-magnesium spinel castables, and the performance of the castables has been significantly improved. Aluminum-magnesia spinel castable has the advantages of high density, high strength, corrosion resistance, spalling resistance, and low wear rate. It can significantly increase the package age, so it is adopted by many manufacturers. The lining construction process has evolved from ramming, projection, and vibration to tire mold vibration. The tire mold vibration reduces the consumption of ladle refractory materials. Achieving good results, the average ladle wrapping age can reach 70-80 times. It has the advantages of uniform vibration, easy operation, high labor efficiency, and can realize continuous ladle lining casting. Its physical and chemical indicators are shown in Table 1.

Table 1 Physical and chemical indicators of high alumina spinel casting materials

projectContentIndicators
    chemical composition,%   MgO+Al₂O₃ 80-90
Bulk density, g/cm³   110℃×16h
   1550℃×3h
 2.85
2.80
  Flexural strength, MPa   110℃×16h
   1550℃×3h
8
10
    Line change rate, %   110℃×16h
   1550℃×3h
 ±0.1
±4.0

Low cement refractory castable

Low-cement refractory castables are developed on the basis of clay combined with refractory castables. They are also a new generation of refractory castables that flourished in the 1980s. Its main varieties include low cement, ultra-low cement and cement-free refractory castables. It combines the advantages of various refractory castables and has the characteristics of high density, low porosity, high strength, low wear, thermal shock resistance and corrosion resistance. , it also has the characteristics of strong volume stability and low construction water consumption, so it is widely used, has good use effects and significant social and economic benefits. Table 2 shows the performance data statistics of low cement, ultra-low cement and cement-free castables.

Table 2 Performance of low cement, ultra-low cement and cement-free castables

Element

A

B

C

LCA

LCB

ULC

CFA

CFM

 

Aluminum oxide, %

Silicon oxide, %

Calcium Oxide,%

Amount of water added, %

9459

9459

9638

98426

9527

99  <1  6

100 2 4-5

92  8  2  4-5

Volume density, g/em3

110℃×16h1000℃×3h1500℃×3h1650℃×3h

2.812.672.8

2.962.82.932.94

2.952.932.99

2.872.842.952.96

3.2  3  3.1  3.1

3.2 3.2 3.2 3.2

3  3  3.1  3.1

Porosity, %

110℃×16h1000℃×3h1500℃×3h1650℃×3h

17.525.523.7

15.323.719.5  

18.321.919.7

11191715

15.718.516.5

14.817.913.9

13.6 12.7 11.7

Flexural strength, MPa

110℃×16h1000℃×3h1500℃×3h1650℃×3h

5.35.44.5

4.73.76.5

2.52.17.2

4.711.0

3010.012.013.0

3.09.012.020.0

3.0 9.0 18.0 15.0

Introduction to refractory bricks for ladles

Aluminum silicate material

Clay bricks

Clay bricks are the earliest refractory materials used in ladles in my country. In the 1950s and 1960s, the refractory materials used in ladles in my country were mainly various clay bricks. Due to their low cost, some steel plants still used clay bricks in their ladles until the 1980s. . The physical and chemical indicators of clay bricks used for ladles in a steel plant are: Al2O3 44.10%, SiO2 52.10%, Fe2O3 1.72%, apparent porosity 16% ~ 18%, and normal temperature compressive strength 54.9 ~ 96.0MPa. The service life of clay ladle lining bricks varies depending on the usage conditions of each steel plant. Although clay bricks are no longer used in ladles in my country, clay bricks made a significant contribution to the recovery and subsequent development of my country’s steelmaking industry in the early days of the founding of the People’s Republic of China.

Refractory bricksHigh alumina bricks

With the continuous development of steelmaking technology and the continuous improvement of steel output and quality, clay ladle lining bricks have a short service life. Since the late 1960s, some steel plants in my country have begun to use various high-aluminum lining bricks for ladles. The service life of the ladle is greatly improved.

Wuhan Iron and Steel’s 270t open-hearth ladle began to use second-grade high-alumina bricks in 1968. By 1970, the ladle age reached 25.7 times, which was 2.5 times that of clay lining bricks. In 1974, the age reached 31.5 times. The 70t ladle for the No. 2 steelmaking converter of Wuhan Iron and Steel Co., Ltd. has been using high-aluminum bricks with an Al2O3 content greater than 72% since 1980. The ladle age is 34 times and the highest is 50 times.

Since June 1986, Baosteel’s 300t ladle has used first-class high alumina bricks produced by a refractory material factory for the entire wall, with an average ladle age of about 50 times. After the continuous casting machine was put into operation, the usage conditions of the ladle deteriorated and the service life of the ladle lining was shortened. Baosteel cooperated with some refractory material manufacturers to develop micro-expanded high-alumina bricks with excellent performance. In April 1992, the products produced by Factory A were officially used. The average service life is 81.5 times, and the maximum service life reaches 100 times. The average service life of products from Factory B is 78.6 times, with a maximum of 122 times (continuous casting ratio 55.73%).

Taigang’s 70t ladle uses high-aluminum lining bricks and has a service life of 64.3 times.

In short, the use of high-aluminum lining bricks for ladles in my country has significantly improved the service life of ladles, ensured the smooth progress of steelmaking production, and promoted the further development of the steelmaking industry.

Wax stone bricks

Pyrophyllite brick is a fired product made primarily from pyrophyllite. In the early 1970s, a refractory bricks factory in Fujian produced waxstone ladle bricks, which were tested on various ladles at Maanshan Iron and Steel, Anshan Iron and Steel, Shanghai Steel No. 3 Plant, and Sanming Steel Plant. The results showed that waxstone bricks performed better than the clay bricks and third-grade high alumina bricks used at the time. For example, Maanshan Iron and Steel’s 15t ladle achieved a service life of 66 times.

Wuhan Iron and Steel No. 2 Steelmaking Plant also tested waxstone bricks with 72% SiO2 content on its 70t ladle, but the results were less favorable, with a service life of only 14 times. From September 1985 to 1988, Baosteel’s 300t ladle used waxstone bricks imported from Japan, achieving an average lifespan of 38 times.

The physical and chemical indicators of waxstone bricks for ladles produced by a certain factory are: SiO2 78.95%, Al2O3 18.85%-19.51%, Fe2O3 0.44%-0.52%, apparent porosity 14%-18%, and normal temperature compressive strength 32.9-62.9 MPa. Despite these promising indicators, waxstone bricks have not been widely adopted in ladles in my country due to various reasons.

Refractory bricksAluminum-magnesium (carbon) materials

Refractory bricksAluminum-magnesium unburned bricks

In addition to aluminum-magnesium ramming materials and aluminum-magnesium castables, my country has also developed aluminum-magnesium unburned bricks bonded with water glass, which are used on ladles and have a longer life than traditional aluminum silicate ladle bricks. Benxi Iron and Steel’s 160t ladle uses aluminum-magnesia unburned bricks, with an average service life of 40.56 times, which is more than double that of using third-grade high-alumina bricks (lifespan of 18.5 times). The average service life of the aluminum-magnesium unburned bricks used in the 20t ladle of Tianjin No. 3 Steelmaking Plant is 38.8 times, with a maximum of 55 times, which is more than four times the service life of clay lining bricks (9 times).

Refractory bricksAlumina-magnesia carbon brick

The 1990s saw rapid development in continuous casting technology in my country, with high-efficiency continuous casting becoming a key focus. To improve the service life of continuous casting ladles and support efficient casting technology, aluminum-magnesia carbon bricks were developed for ladles. These bricks are used in various continuous casting ladles, significantly extending their service life.

The aluminum-magnesium carbon ladle bricks, developed jointly by Luonai Institute, Baosteel, and a refractory bricks factory in Jiaozuo, are used in Baosteel’s 300t continuous casting ladles. The ladle age increased from over 20 times with first-class high alumina bricks to over 80 times, with a peak of 126 times. Angang No. 3 Steelmaking’s 200t fully continuous casting and out-of-furnace refining ladle uses alumina-magnesia carbon bricks, achieving an average lifespan of 64 times and a maximum of 73 times.

In 1993, the promotion of high-quality aluminum-magnesia-carbon bricks for ladles was fully launched in my country. Many steelmaking plants began using these bricks, significantly improving ladle life. For instance, Panzhihua Iron and Steel Co., Ltd.’s 160t ladles saw their average service life increase to 90 times, with a maximum of 115 times after using alumina-magnesia carbon lining bricks.

Alumina-magnesia carbon bricks are unfired products made from special-grade high-alumina clinker, fused or sintered magnesia, graphite, and liquid phenolic resin as a binder.

High-grade aluminum-magnesium unburned bricks

Carbon-containing ladle lining bricks will cause carbonization of molten steel during use, which is very detrimental to the smelting of clean steel, low carbon steel and ultra-low carbon steel. In order to meet the needs of clean steel, low carbon steel and ultra-low carbon steel smelting, high-grade aluminum-magnesium non-burning bricks (carbon-free non-burning bricks) were developed. Compared with the water glass-bonded aluminum-magnesium unburned bricks developed in the early 1980s, high-grade aluminum-magnesium unburned bricks are a qualitative leap forward. In addition to using high-purity raw materials (corundum, high-purity fused magnesite and high-purity aluminum-magnesium spinel, etc.), the binder also uses high-performance composite binders.

High-grade aluminum-magnesium unburned bricks have achieved good results when used on ladles. Their service life reaches or even exceeds that of carbon-containing ladle lining bricks, while reducing the carbonization of molten steel. For example, the aluminum-magnesia non-burning bricks developed by a refractory bricks company in Henan are used on 100t ladles and LF refining ladles in a steel plant. Their service life is 1.5 times that of aluminum-magnesia carbon bricks. Angang’s 200t ladle uses aluminum-magnesium unburned bricks for more than 110 times, with a maximum of 128 times. The service life of the 170t continuous casting ladle reaches 119 times, which exceeds that of alumina-magnesia carbon bricks. Baosteel’s 300t continuous casting ladle stopped using alumina-magnesia carbon bricks in June 1998 and began to use high-grade alumina-magnesia unburned bricks.

magnesium carbonaceous material

Refractory bricksMagnesia carbon brick

Magnesia carbon bricks have excellent corrosion and spalling resistance. They are primarily used in the slag line area of the ladle, while other refractory materials like castables and unfired bricks are used in non-slag line areas. This approach not only achieves a higher service life but also reduces refractory material costs.

The physical and chemical indicators of magnesia carbon bricks used in the ladle slag line of a steel plant are: MgO 77.4%, C 16.75%, apparent porosity 3.1%, bulk density 2.903 g/cm³, and normal temperature compressive strength 38.6 MPa. In September 1981, Wuhan Iron and Steel No. 2 Steelmaking Plant first used magnesia carbon bricks in the 70t ladle slag line, achieving a service life of 50 times. However, the high alumina bricks in non-slag line parts were seriously damaged and discontinued.

Since July 1989, Baosteel’s 300t ladle slag line has used MT-14A magnesia carbon bricks, with a life exceeding 100 times. A 90t LF refining ladle slag line in another steel plant uses magnesia carbon bricks with about 16% carbon content, achieving a slag line life of 95 times. Some steel plants use all-magnesia carbon bricks for ladle lining. For instance, a 60t LF-VD refining ladle in an electric furnace has an average service life of 47 times, with a maximum of 57 times.

Refractory bricksLow carbon magnesia carbon bricks

The use of magnesia-carbon bricks in ladle slag lines has the problem of carbonization of molten steel. In recent years, some steel mills have cooperated with refractory manufacturers to develop low-carbon magnesia-carbon bricks for ladle slag lines. Baosteel’s 300t ladle slag line has tried low-carbon magnesia-carbon bricks with a carbon content of less than 7% and less than 5%. The service life can reach about 110 times, which is equivalent to ordinary magnesia-carbon bricks and can basically meet the usage requirements of a 300t ladle. The slag line of Anshan Iron and Steel Ladle also uses low-carbon lining bricks with a carbon content of less than 5%, and the results are good.

Refractory bricksMagnesium calcium (carbon) materials

Refractory bricksUnfired magnesia calcium bricks

In the early 1990s, Luonai Institute developed unburned magnesia-calcium bricks for ladles using synthetic magnesia-calcium sand and fused magnesia sand as raw materials, and solid inorganic salts and inorganic salt solutions as binding agents. Used on 40tLF-VD refining ladles, the service life is more than 40 times, and the oxygen content in the steel dropped from 12.2×10-6 to 11.13×10-6. In 1992, the product passed the appraisal of the former Ministry of Metallurgy, and was later used in Great Wall Special Steel It is used on the refining ladles of steel plants such as factories.

In recent years, a refractory material bricks company has developed anhydrous resin-bonded unburned magnesia-calcium bricks, which are used in a steel company’s 100tLF refining ladle, with a service life of 80 to 85 times and an erosion rate of 1.28 to 1.37mm/time.

From July to August 2006, Shandong Magnesium Mine cooperated with a refractory material bricks factory to develop unburned magnesia-calcium bricks, which were used in the non-slag line part of the wall of a 90tLF refining ladle (refining rate 100%) in a steel plant, with a service life of More than 60 times. The breathable bricks at the bottom of the package were discontinued due to serious corrosion. The thickness of the remaining unburned magnesia calcium bricks is about 130mm and can still be used. It is expected that the normal package age can reach 80 to 100 times.

Unfired magnesia-calcium carbon bricks

At the beginning of this century, Shougang No. 2 Steelmaking Plant cooperated with a refractory bricks company to develop unburned magnesia-calcium carbon bricks using synthetic magnesia-calcium sand, fused magnesia sand and high-purity graphite as raw materials and anhydrous resin as a binder. It is used in the non-slag line part of the 225t ladle of Shougang No. 2 Steelmaking Plant (magnesia carbon bricks for slag line), with an average service life of 116.8 times. Compared with the original alumina-magnesia carbon bricks, when the ladle wall is thinned by 20mm, the average Lifespan increased by 37.57 times. Moreover, the oxygen content and non-metallic inclusions in steel have been reduced.

There are also some steel plants that use magnesia-calcium carbon bricks in the slag lines of various refining ladles such as SKF and LF-VD, and have achieved good results.

LMM YOTAI established in 2007. Our production technology comes from Japanese Yotai. As an experienced and international player in the refractories industry. We have succeeded in expanding both the breadth of its product range and the depth of its services. From raw material selection, refractory portofio & optimization, installation & services & recycle of used refractories on site to further reduce client’s Opex & Capex in refractory consumption per ton steel output, meanwhile improve product quality of client.

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