The ladle (or steel ladle) carries the dual tasks of transporting molten steel and performing refining outside the furnace. With the advancement of steelmaking technology, my country’s ladle refractory materials have also made great progress. Especially since the 1980s, my country’s refractory research institutions, production enterprises, and end-users have worked closely together, taking into account my country’s national conditions, to continuously develop new types of ladle refractory materials. This has enabled my country’s ladle refractory materials to advance at a relatively fast pace, meeting the needs of the rapid development of my country’s steelmaking industry.
Refractory materials for ladle
From the 1950s to the 1970s, my country’s ladle linings primarily used aluminum silicate refractories, including various clay bricks and high-alumina bricks. Since the 1980s, my country has developed a series of new ladle refractories, including aluminum-magnesium (carbon), magnesium-carbon, and magnesium-calcium (carbon). Among them, aluminum-magnesium (carbon) refractories, with their diverse variety and comprehensive specifications, are the primary ladle refractory material in my country.
Aluminosilicate ladle refractory
Clay bricks
Clay bricks were the first refractory materials used in my country’s ladle refractory industry. In the 1950s and 1960s, the main refractory materials used in my country’s ladle were various clay bricks. Due to their low cost, some steel mills still used clay bricks in their ladles until the 1980s. The physical and chemical indicators of clay bricks used in the ladle of a certain steel mill are: Al2O3 44.10%, SiO2 52.10%, Fe2O3 1.72%, apparent porosity 16% to 18%, and room temperature compressive strength 54.9 to 96.0 MPa. The service life of clay ladle lining bricks varies depending on the operating conditions of each steel mill. Although clay bricks are no longer used in my country’s ladles, clay bricks made significant contributions 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.
High alumina bricks
With the continuous development of steelmaking technology and the continuous improvement of steel production and quality, clay lining bricks have a short service life. Since the late 1960s, some steel mills in my country have begun to use various high-aluminum lining bricks for their ladles, which has greatly increased the service life of the ladles.
The 270t ladle used in Wuhan Iron and Steel’s open-hearth furnace began to use second-grade high-aluminum bricks in 1968[1]. By 1970, the ladle life reached 25.7 times, which is 2.5 times that of clay lining bricks. In 1974, the ladle life reached 31.5 times[2]. The 70t ladle used in Wuhan Iron and Steel’s No. 2 steelmaking converter began to use high-aluminum bricks with an Al2O3 content greater than 72% in 1980[3]. The ladle life is 34 times, with a maximum of 50 times.
Baosteel’s 300t ladle has used first-grade high-aluminum bricks produced by a refractory material factory for its entire ladle wall since June 1986, with an average ladle life of about 50 times. After the continuous casting machine went into operation, ladle operating conditions deteriorated, shortening the service life of the ladle lining. Baosteel, in collaboration with certain refractory manufacturers, developed high-alumina, slightly expanded bricks with excellent performance. Starting in April 1992, Baosteel began using products from Plant A, achieving an average service life of 81.5 cycles, with a maximum of 100. Products from Plant B achieved an average service life of 78.6 cycles, with a maximum of 122 cycles (continuous casting ratio of 55.73%).
TISCO’s 70t ladle, using high-alumina lining bricks, achieved a service life of 64.3 cycles.
In short, the use of high-alumina lining bricks in my country’s ladle industry has significantly increased its service life, ensuring smooth steelmaking operations and promoting the further development of the steelmaking industry.
High alumina ramming mass
In the late 1970s, some Chinese steel mills used high-alumina ramming mass for ladle linings, achieving excellent results. High-alumina ramming mass is a highly plastic, monolithic refractory material made from high-quality high-alumina bauxite clinker (aggregate and fines) and industrial phosphoric acid as a binder. The material is mixed and blended to create a monolithic refractory material. Using integral ramming technology, this monolithic lining achieves a long service life.
Wax stone bricks
Aluminum bricks are a type of fired product made from talc as the main raw material. In the early 1970s, a refractory material factory in Fujian produced aluminum bricks for ladle use on different types of ladles at steel mills such as Maanshan Iron and Steel, Anshan Iron and Steel, Shanghai No. 3 Steel Plant, and Sanming Steel Plant. The results showed that the performance of aluminum bricks was superior to the clay bricks and third-grade high-aluminum bricks used at the time. When used on Maanshan Iron and Steel’s 15t ladle, the lifespan reached 66 times. The 70t ladle of Wuhan Iron and Steel’s No. 2 Steelmaking Plant also tried aluminum bricks with a SiO2 content of 72% produced by the plant, but the results were not ideal, with a service life of only 14 times. Baosteel’s 300t ladle used aluminum bricks imported from Japan from September 1985 to 1988, with an average lifespan of 38 times[4]. The physical and chemical indicators of wax stone bricks for steel 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 room temperature compressive strength 32.9~62.9MPa. Due to various reasons, wax stone bricks have not been promoted and applied in steel ladles in my country.
Aluminum-magnesium (carbon) ladle refractory materials
Since the 1980s, my country’s steelmaking industry has entered a period of rapid development. The widespread application of modern steelmaking technologies such as continuous casting and refining, as well as the increase in clean steel production, have made the operating conditions of ladle refractories even more challenging. The increase in molten steel temperature, the prolonged residence time of the molten steel in the ladle, the erosion of the ladle refractories by the molten steel and slag, and the chemical attack of the slag on the ladle refractories have all become more severe. Previous ladle refractories are no longer able to meet the needs of modern steelmaking. To this end, my country has developed a variety of aluminum-magnesium (carbon) ladle refractories. During use, Al2O3 and MgO react at high temperatures to form magnesia-aluminum spinel, a mineral with excellent high-temperature properties. This significantly improves the refractory’s erosion and spalling resistance. Therefore, the use of aluminum-magnesium (carbon) ladle refractories can significantly extend the service life of the ladle.
Aluminum-magnesium integral ramming material
In the early 1980s, the Luoyang Refractory Research Institute, Anshan Coking and Refractory Research Institute, and Anshan Iron and Steel Corporation jointly developed an aluminum-magnesium ladle ramming mass. This ramming mass is a highly plastic, monolithic refractory material made from premium high-alumina bauxite clinker as the aggregate, a mixture of premium high-alumina bauxite clinker powder and sintered magnesia powder as the matrix, and liquid water glass as the binder. Used in Anshan Iron and Steel’s No. 3 Steelmaking Plant’s 200-ton ladle, its service life is 5 to 7 times longer than clay bricks, with an average lifespan of 85.15 cycles and a maximum of 108 cycles. The refractory material consumption is 2.7 kg per ton of steel. In June 1982, this ramming mass passed the appraisal of the former Ministry of Metallurgy. Subsequently, many steel mills across China adopted this aluminum-magnesium ladle ramming mass, achieving excellent results.
Aluminum-magnesium castables
Following the development of aluminum-magnesium ramming materials, my country has developed aluminum-magnesium castables using high-quality high-alumina bauxite clinker and sintered magnesia as raw materials and liquid water glass as a binder. This castable was first promoted and applied to small ladles during the Sixth Five-Year Plan period, achieving good results. For example, the 10t and 14t ladles of a steel plant in Hebei Province used aluminum-magnesium castables combined with water glass, with an average ladle life of 109.7 times, which is more than 8 times that of clay brick lining. The 15t and 13t ladles of a steel plant in Heilongjiang Province used aluminum-magnesium castables, with an average ladle life of 53 times, while the clay brick lining life was only 6 to 10 times. During the Seventh Five-Year Plan period, the integral casting lining technology of the ladle was listed as a key new technology promotion project of the former Ministry of Metallurgy and promoted nationwide. By the third quarter of 1987, most of the medium and small ladles (capacity below 45t) for converters below 30t in my country adopted integral casting lining. The service life of the integral casting ladle lining is generally 40 to 60 times, and some small ladles can reach 90 times. The consumption of refractory materials and the cost of the ladle lining have been greatly reduced, achieving significant economic benefits. The physical and chemical indicators of the water glass combined with aluminum-magnesium castable for the ladle of a certain steel plant are Al2O3 75.20%, MgO 9.47%, SiO2 10.25%, bulk density (110℃×24h) 2.67～2.73g./cm3, and room temperature flexural strength (110℃×24h) 14.9MPa.
Aluminum-magnesium unfired bricks
In addition to aluminum-magnesium ramming materials and aluminum-magnesium castables, my country has also developed aluminum-magnesium unfired bricks bonded with water glass for use in ladles, which have a longer lifespan than traditional aluminum silicate ladle bricks. Bengang’s 160t ladle, using aluminum-magnesium unfired bricks, has an average lifespan of 40.56 cycles, more than double that of third-grade high-alumina bricks (18.5 cycles). Tianjin No. 3 Steel Plant’s 20t ladle, using aluminum-magnesium unfired bricks, has an average lifespan of 38.8 cycles, with a maximum of 55 cycles, more than four times the lifespan of clay lining bricks (9 cycles).
The physical and chemical indicators of the water glass combined aluminum-magnesium unfired bricks produced by a certain factory are: Al2O3 68.46%~74.07%, MgO 7.65%~12.32%, SiO2 9.02%~13.37%, Fe2O3 1.12%~1.83%, bulk density 2.48~2.86g/cm3, apparent porosity 16%~23%, and compressive strength at room temperature 55.6~123MPa.
Magnesium aluminate spinel castable
In the early 1990s, with the industrialization of bauxite-based synthetic magnesia-aluminate spinel refractory materials in my country, numerous refractory research institutions and manufacturers developed a variety of bauxite-based magnesia-aluminate spinel castables for ladles with varying performance characteristics. These castables incorporate a certain proportion of pre-synthesized magnesia-aluminate spinel, significantly improving their corrosion and spalling resistance, surpassing waterglass-bonded aluminum-magnesium castables. They have demonstrated excellent performance in various ladles.
The bauxite-based aluminum-magnesium spinel castable, jointly developed by the Luoyang Refractories Research Institute and a refractory manufacturer in Henan Province, has been tested in a 70t ladle (DH vacuum lance argon-blown) at Taiyuan Iron and Steel Corporation and a 30t continuous casting ladle (continuous casting ratio of no less than 94%) at Hefei Iron and Steel Corporation. The castables achieved average service lives of 71 and 114 cycles, respectively, representing a 1-3 times improvement over waterglass-bonded aluminum-magnesium castables. A Hangzhou steel plant’s 25t continuous casting ladle (continuous casting ratio greater than 70%) uses magnesia-alumina spinel castable, achieving an average ladle life of 77 cast cycles, 1.2 times longer than a waterglass-bonded aluminum-magnesium castable. A 28t ladle at Jiangxi Xingang’s No. 1 Steelmaking Plant uses magnesia-alumina spinel castable, achieving an average life of 79 cast cycles, 1.6 times longer than a waterglass-bonded aluminum-magnesium castable.
Bauxite-based magnesia-alumina spinel castable uses high-quality high-alumina bauxite clinker as the aggregate, with a matrix composed of high-quality high-alumina bauxite clinker powder, synthetic magnesia-alumina spinel powder, and sintered magnesia powder. Binders include polyphosphate, SiO2 fine powder, Al2O3 fine powder, and pure calcium aluminate cement. The physical and chemical indicators of the bauxite-based magnesia-alumina spinel castable produced by a certain factory are: Al2O3 68.84%, MgO 14.63%, SiO2 11.27%, Fe2O3 1.74%, bulk density (110℃×24h) 2.73g/cm3, room temperature compressive strength 42.88MPa, room temperature flexural strength 55.1MPa.
Alumina-magnesia-carbon bricks
The 1990s saw rapid development of 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 meet the demands of this technology, my country developed aluminum-magnesium-carbon bricks for these ladles. These bricks are used in various types of continuous casting ladles, significantly extending their lifespan.
Aluminum-magnesium-carbon bricks, developed jointly by the Luoyang Refractories Research Institute, Baosteel, and a refractory material manufacturer in Jiaozuo, are now used in Baosteel’s 300t continuous casting ladles. The ladles’ service life has increased from over 20 cycles using first-grade high-aluminum bricks to over 80 cycles, with a maximum of 126 cycles. Ansteel’s 200t ladle, which is fully continuous cast and undergoes off-furnace refining, uses aluminum-magnesium-carbon bricks, achieving an average service life of 64 cycles, with a maximum of 73 cycles. In 1993, the promotion and use of high-quality aluminum-magnesium-carbon bricks for ladles began in my country. Many steel mills, adapting to their specific needs, began using aluminum-magnesium-carbon ladle lining bricks, significantly extending the lifespan of their ladles. For example, after using aluminum-magnesium-carbon lining bricks, the average lifespan of Panzhihua Iron and Steel’s 160t ladle increased to 90 cycles, with a maximum of 115 cycles.
Aluminum-magnesium-carbon bricks are unfired products made from premium high-alumina bauxite clinker, fused or sintered magnesia, and graphite, using liquid phenolic resin as a binder.
Magnesia alumina spinel carbon brick
Building on the development of aluminum-magnesium carbon bricks, my country has also developed magnesium-aluminum spinel carbon bricks for ladles. These bricks incorporate a certain proportion of pre-synthesized magnesium-aluminum spinel into the brick material, resulting in superior performance compared to comparable aluminum-magnesium carbon bricks.
A magnesium-aluminum spinel carbon brick developed in collaboration with Baosteel and used in Baosteel’s 300t continuous casting ladle boasts an average service life of 105 cycles, with a maximum of 200 cycles. A magnesium-aluminum spinel carbon brick developed by the General Research Institute of Building Research is used in Anshan Iron and Steel’s 200t continuous casting ladle with off-furnace refining, with an average service life of 73.3 cycles, with a maximum of 82 cycles. A magnesium-aluminum spinel carbon brick developed in collaboration with a Xinxiang refractory manufacturer and used in Shougang’s 90t ladle for the Second Steelmaking Plant has seen its service life increased from 20 cycles for aluminum-magnesium carbon bricks to 40 cycles, with a maximum of 51 cycles.
The development and use of alumina-magnesia spinel carbon bricks have further improved the service life of my country’s continuous casting ladles.
High-grade aluminum-magnesium unfired bricks
Carbon-containing ladle lining bricks can cause carbonization of the molten steel during use, which is highly detrimental to the production of clean, low-carbon, and ultra-low-carbon steels. To meet the demands of clean, low-carbon, and ultra-low-carbon steel production, high-grade aluminum-magnesium unfired bricks (carbon-free unfired bricks) have been developed. These high-grade aluminum-magnesium unfired bricks represent a qualitative leap compared to the water glass-bonded aluminum-magnesium unfired bricks developed in the early 1980s. In addition to utilizing high-purity raw materials (such as corundum, high-purity fused magnesia, and high-purity aluminum-magnesium spinel), they also utilize a high-performance composite binder.
High-grade aluminum-magnesium unfired bricks have demonstrated excellent performance in ladle applications, achieving a service life equal to or exceeding that of carbon-containing ladle lining bricks while also reducing carbonization of the molten steel. For example, an aluminum-magnesium unfired brick developed by a Henan refractory company, used in a steel mill’s 100t ladle and LF refining ladle, has a lifespan 1.5 times that of aluminum-magnesium carbon bricks.
Ansteel’s 200t ladle, using unfired aluminum-magnesium bricks, has a lifespan of over 110 cycles, with a maximum of 128 cycles. The service life of a 170t continuous casting ladle has reached 119 cycles, exceeding that of aluminum-magnesium carbon bricks. Baosteel’s 300t continuous casting ladle stopped using aluminum-magnesium carbon bricks in June 1998 and began using high-grade aluminum-magnesium unfired bricks.
High-grade aluminum-magnesium (spinel) castable
In the mid-1990s, my country developed high-grade aluminum-magnesium castables for large and medium-sized ladles. The raw materials used in high-grade aluminum-magnesium (spinel) castables include corundum (electrofused corundum, sintered corundum, etc.), high-purity fused magnesia, high-purity aluminum-magnesium spinel (electrofused and sintered), etc. The binders include pure calcium aluminate cement, Al2O3 micropowder, high-purity SiO2 micropowder, etc.
Baosteel’s 300t ladle began to trial the use of high-grade aluminum-magnesium castables developed by several refractory material factories in my country in December 1996. By 2000, the average service life was 258 times [4]. The high-grade aluminum-magnesium spinel castable developed by Shougang No. 3 Steelmaking Plant and a refractory company in Xinxiang was used on the 90tLF refining ladle of Shougang No. 3 Steelmaking Plant, with a service life of 138 times and an erosion rate of 0.62mm/time.
Ansteel’s No. 3 Steelmaking Plant uses high-grade aluminum-magnesium (spinel) castables for its 200t continuous casting ladles, achieving a service life of 150 cycles. Other steel mills have also achieved excellent results using precast blocks of castables. For example, Benxi Steel’s ladles, which used aluminum-magnesium carbon bricks, had a service life of 65 cycles. After switching to high-grade aluminum-magnesium spinel precast blocks, the average service life increased to 118 cycles, with a peak of 126. By 2000, 90% of Benxi Steel’s ladles were lined with high-grade aluminum-magnesium castable precast blocks.
Magnesia-carbon ladle refractory
Magnesia carbon bricks
Magnesia carbon bricks offer excellent corrosion and spalling resistance. Magnesia carbon bricks are primarily used in the slag line of the ladle, while other refractory materials (such as castables and unfired bricks) are used in non-slag line areas. This ensures a longer service life while reducing refractory material costs. The physical and chemical properties of magnesia carbon bricks used in the slag line of a certain steel plant’s ladle are: MgO 77.4%, C 16.75%, apparent porosity 3.1%, bulk density 2.90 g/cm³, and room-temperature compressive strength 38.6 MPa.
In September 1981, Wuhan Iron and Steel’s No. 2 Steelmaking Plant pioneered the use of magnesia carbon bricks in the slag line of its 70t ladle. The bricks achieved a service life of 50 cycles before being discontinued due to severe damage to high-alumina bricks in non-slag line areas. Baosteel began using MT-14A magnesia carbon bricks in its 300t ladle slag line in July 1989, achieving a slag line life of over 100 cycles. The slag line of a steel mill’s 90tLF refining ladle uses magnesia-carbon bricks with a carbon content of approximately 16%, resulting in a lifespan of 95 cycles. Some steel mills also use all-magnesium-carbon brick linings for their ladles. For example, a steel mill’s 60tLF-VD refining ladle, lined with all-magnesium-carbon bricks, has an average lifespan of 47 cycles, with a maximum of 57 cycles.
Low carbon magnesia carbon bricks
The use of magnesia carbon bricks in the ladle slag line has been linked to the problem of increased carbonization in the molten steel. In recent years, some steel mills have collaborated with refractory manufacturers to develop low-carbon magnesia carbon bricks for ladle slag lines.
Baosteel’s 300t ladle slag line has tested low-carbon magnesia carbon bricks with carbon contents of less than 7% and less than 5%, achieving a service life of approximately 110 cycles, comparable to conventional magnesia carbon bricks and generally meeting the operational requirements of a 300t ladle. Ansteel’s ladle slag line also uses low-carbon lining bricks with a carbon content of less than 5%, with good results.
Magnesia-calcium (carbon) ladle refractory materials
Magnesia-calcium refractories offer excellent high-temperature stability and resistance to high-basicity slag. In particular, the free CaO in them purifies molten steel, making them ideal for ladle applications. As clean steel production continues to increase, the application of magnesia-calcium refractories will continue to expand.
Dolomite ramming material
In the early 1980s, TISCO used dolomite ramming mass made of ordinary sintered dolomite as raw material and medium-temperature asphalt as binder on 70t ladle, achieving good results with an average lifespan of 76 times and a maximum of 112 times.
Unfired magnesia-calcium bricks
In the early 1990s, Luoyang Refractories Institute used synthetic magnesia-calcium sand and fused magnesia sand as raw materials and solid inorganic salts and inorganic salt solutions as binders to develop unburned magnesia-calcium bricks for ladles [22]. The bricks were used in a 40t LF-VD refining ladle at a Shanghai steel plant, with a service life of more than 40 times and a reduction in the oxygen content in the steel 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 subsequently used in the refining ladles of steel plants such as Great Wall Special Steel Plant. In recent years, a refractory material company has developed anhydrous resin-bonded unburned magnesia-calcium bricks, which were used in a 100t LF refining ladle at a steel company, with a service life of 80 to 85 times and an erosion rate of 1.28 to 1.37 mm/time. Between July and August 2006, Shandong Magnesium Mine collaborated with a refractory material manufacturer to develop unfired magnesia-calcium bricks. These bricks were used in the non-slag line area of a 90tLF refining ladle (100% refining rate) at a certain steel mill, achieving a service life of over 60 cycles. The ladle was shut down due to severe wear and tear on the air-permeable bricks at the ladle bottom. The remaining unfired magnesia-calcium bricks, approximately 130mm thick, are still usable, with an estimated service life of 80 to 100 cycles.
Unfired magnesia calcium carbon bricks
At the beginning of this century, Shougang No. 2 Steelmaking Plant collaborated with a refractory materials company to develop unburned magnesia-calcium carbon bricks using synthetic magnesia-calcium sand, fused magnesia, and high-purity graphite as raw materials and anhydrous resin as a binder. These bricks were used in the non-slag line area of Shougang No. 2 Steelmaking Plant’s 225t ladle (magnesia-carbon bricks for the slag line). The bricks have an average service life of 116.8 cycles, an increase of 37.57 cycles compared to the original aluminum-magnesium carbon bricks, even with a 20mm thinner ladle wall. Furthermore, the oxygen content and non-metallic inclusions in the steel were reduced. Some steel mills in my country also use magnesia-calcium carbon bricks in the slag line of various refined ladles such as SKF and LF-VD, and have achieved good results.
Zirconium bricks
From September 1985 to 1989, Baosteel’s 300t ladle used zirconium lining bricks imported from Japan, with an average service life of 90 cycles. During this period, a refractory materials manufacturer in Wuxi also developed zirconium lining bricks using domestic raw materials. These were tested on Baosteel’s 300t ladle and achieved a service life of 88 cycles before being discontinued due to a malfunction in the ladle bottom slide mechanism. The physical and chemical properties of these domestically produced zirconium lining bricks are: ZrO2 60.80%, Al2O3 1.76%, Fe2O3 0.60%, bulk density 3.53g/cm3, apparent porosity 19%, and room-temperature compressive strength 62.9MPa.
In summary, since the 1950s, with the continuous development of my country’s steelmaking technology, my country’s ladle refractory materials have also been continuously developing. New product varieties have been continuously increasing, product quality has been continuously improving, and the use effect has become better and better, meeting the needs of the continuous development of my country’s steelmaking industry. According to the development trend of my country’s steelmaking industry, it is recommended that the development of ladle refractory materials in the future should be carried out from the following aspects.
(1) Develop ladle refractory materials with longer service life to meet the needs of efficient continuous casting and off-furnace refining.
(2) Develop low-carbon, carbon-free and magnesium-calcium series ladle refractory materials with better corrosion resistance and spalling resistance to meet the needs of smelting clean steel, low-carbon steel and ultra-low-carbon steel.
(3) Develop energy-saving ladle refractory materials, such as amorphous refractory materials and unfired bricks.
(4) Develop resource-saving and environmentally friendly ladle refractory materials.
(5) Carry out research on the reuse of various residual ladle refractory materials after use.