The rapid development of my country’s steelmaking industry, the promotion and application of modern steelmaking technologies such as continuous casting and refining outside the furnace, and the increase in the output of clean steel have made the use conditions of ladle refractory materials even worse. The increase in molten steel temperature, the extension of the residence time of molten steel in the ladle, the scouring of molten steel and slag on the ladle refractory materials, and the chemical erosion of slag on the ladle refractory materials are all more serious. The previous ladle refractory materials can no longer meet the needs of modern steelmaking production. For this reason, my country has successively developed a variety of aluminum-magnesium (carbon) refractory materials for ladle. During the use of aluminum-magnesium (carbon) refractory materials, Al2O3 and MgO react at high temperature to form magnesium-aluminum spinel, a mineral with excellent high-temperature performance, which significantly improves the erosion resistance and spalling resistance of the refractory materials. Therefore, the use of aluminum-magnesium (carbon) refractory materials for ladle can greatly increase the service life of the ladle.
Aluminum-magnesium integral ramming mass
In the early 1980s, Luoyang Refractory Research Institute, Anshan Jiao Refractory Institute and Anshan Iron and Steel Group jointly developed an aluminum-magnesium ladle integral ramming mass. The ramming mass is a kind of amorphous refractory material with good plasticity, which is made of super-grade high-alumina bauxite clinker as aggregate, a mixed powder of super-grade high-alumina bauxite clinker powder and sintered magnesia powder as matrix, and liquid water glass as binder. It is used on the 200t ladle of Anshan Iron and Steel Group’s third steelmaking plant. Its service life is 5 to 7 times longer than that of clay bricks, with an average life of 85.15 times, the highest reaching 108 times, and the consumption of refractory materials per ton of steel is 2.7kg. In June 1982, the ramming mass passed the appraisal of the former Ministry of Metallurgy. After that, many steel mills across the country have successively used this aluminum-magnesium ladle integral ramming mass for ladles, and have achieved good results.
Aluminum-magnesium castable
Following the development of aluminum-magnesium ramming material, my country has developed aluminum-magnesium castables that use 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 and achieved good results. For example, the 10t and 14t ladles of a steel plant in Hebei Province use aluminum-magnesium castables combined with water glass, with an average lifespan of 109.7 times[12], which is more than 8 times that of clay brick lining. The 15t and 13t ladles of a steel plant in Heilongjiang Province use aluminum-magnesium castables, with an average lifespan of 53 times, while the lifespan of clay brick lining is only 6 to 10 times.
During the Seventh Five-Year Plan period, the integral casting lining technology of ladles 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 mostly 40 to 60 times, and some small ladles can reach 90 times [13]. The consumption of refractory materials and the cost of 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%, volume density (110℃×24h) 2.67～2.73g./cm3, and room temperature flexural strength (110℃×24h) 14.9MPa.
Aluminum-magnesium unfired brick
In addition to aluminum-magnesium ramming materials and aluminum-magnesium castables, my country has also developed aluminum-magnesium unfired bricks combined with water glass, which are used in ladles and have a longer lifespan than traditional aluminum silicate ladle bricks. Bengang’s 160t ladle uses aluminum-magnesium unfired bricks, with an average lifespan of 40.56 times, more than double the use of third-class high-aluminum bricks (lifespan of 18.5 times). Tianjin No. 3 Steel Plant’s 20t ladle uses aluminum-magnesium unfired bricks with an average lifespan of 38.8 times, with a maximum of 55 times, more than four times the lifespan of clay lining bricks (9 times).
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%, volume density 2.48~2.86g/cm3, apparent porosity 16%~23%, and room temperature compressive strength 55.6~123MPa.
Magnesium aluminate spinel castable
In the early 1990s, with the industrialization of alumina-based synthetic magnesium-aluminum spinel, a refractory raw material in my country, many refractory research institutions and production enterprises in my country have successively developed a variety of alumina-based magnesium-aluminum spinel castables for ladles with different performance. Since a certain proportion of pre-synthesized magnesium-aluminum spinel is added to this type of castable, the erosion resistance and spalling resistance of the castable are greatly improved, and its performance is better than that of aluminum-magnesium castables combined with water glass. It has achieved good results in various types of ladles.
The alumina-based aluminum-magnesium spinel castable jointly developed by Luoyang Institute of Refractory and a refractory material factory in Henan Province has been tried in 70t (DH vacuum spray gun argon blowing) ladle of Taigang and 30t continuous casting ladle of Hegang (continuous casting ratio not less than 94%), and the average lifespan reached 71 times and 114 times respectively, which is 1 to 3 times higher than that of aluminum-magnesium castables combined with water glass. A 25t continuous casting (continuous casting ratio greater than 70%) ladle in a steel plant in Hangzhou uses magnesium-aluminum spinel castable, with an average ladle life of 77 times, which is 1.2 times higher than that of aluminum-magnesium castable combined with water glass. A 28t ladle in a steelmaking plant in Jiangxi New Steel uses magnesium-aluminum spinel castable, with an average life of 79 times, which is 1.6 times higher than that of aluminum-magnesium castable combined with water glass.
Alumina-based magnesium-aluminum spinel castable uses high-quality high-alumina bauxite clinker as aggregate, high-quality high-alumina bauxite clinker powder, synthetic magnesium-aluminum spinel powder and sintered magnesia powder as matrix, and binders include: polyphosphate, SiO2 micropowder, Al2O3 micropowder, pure calcium aluminate cement, etc. The physical and chemical indicators of alumina-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 brick
The 1990s was a period of rapid development of continuous casting technology in my country, and efficient continuous casting technology became the focus of its development. In order to improve the service life of continuous casting ladles and meet the needs of the development of efficient continuous casting technology, my country has developed aluminum-magnesium-carbon bricks for ladles, which are used in various types of continuous casting ladles, greatly improving the service life of ladles.
The aluminum-magnesium-carbon ladle bricks jointly developed by Luoyang Institute of Refractory Engineering, Baosteel and a refractory material factory in Jiaozuo are used on Baosteel’s 300t continuous casting ladle. The ladle life has increased from more than 20 times using first-class high-aluminum bricks to more than 80 times, with a maximum of 126 times. The 200t ladle of Anshan Iron and Steel’s third steelmaking plant, which is fully continuous cast and refining outside the furnace, uses aluminum-magnesium-carbon bricks, with an average life of 64 times, and a maximum of 73 times. In 1993, the promotion and use of high-quality aluminum-magnesium-carbon bricks for ladles was fully launched in my country. Many steel mills across the country, according to the actual situation of their enterprises, have successively used aluminum-magnesium-carbon ladle lining bricks, which has significantly increased the life of the ladle. For example, after using aluminum-magnesium-carbon lining bricks for Panzhihua Steel’s 160t ladle, the average life has increased to 90 times, and the highest has reached 115 times. Aluminum-magnesium-carbon bricks are unburned products made of special high-alumina bauxite clinker, fused magnesia or sintered magnesia and graphite as raw materials, and liquid phenolic resin as a binder.
Magnesia Alumina Spinel Carbon Brick
On the basis of developing aluminum-magnesium carbon bricks, my country has developed magnesium-aluminum spinel carbon bricks for ladles. Aluminum-magnesium spinel carbon bricks are bricks with a certain proportion of pre-synthesized magnesium-aluminum spinel added to the brick material, and their performance is better than that of aluminum-magnesium carbon bricks of the same grade.
The magnesium-aluminum spinel carbon bricks developed by a refractory material factory in Jiaozuo and Baosteel are used on Baosteel’s 300t continuous casting ladle, with an average service life of 105 times and a maximum of 200 times. The magnesium-aluminum spinel carbon bricks developed by the General Research Institute of Building Research are used on Anshan Iron and Steel’s 200t full continuous casting and off-furnace refining ladle, with an average life of 73.3 times and a maximum of 82 times. The aluminum-magnesium spinel carbon bricks developed by Shougang and a refractory material factory in Xinxiang are used on Shougang’s 90t ladle for the second steelmaking plant, and the service life is increased from 20 times using aluminum-magnesium carbon bricks to 40 times, with a maximum of 51 times. The development and use of aluminum-magnesium spinel carbon bricks have further improved the service life of my country’s continuous casting ladle.
High-grade aluminum-magnesium unfired brick
Carbon-containing ladle lining bricks will cause carbonization of molten steel during use, which is very unfavorable for 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 unfired bricks (carbon-free unfired bricks) have been developed. Compared with the aluminum-magnesium unfired bricks combined with water glass developed in the early 1980s, high-grade aluminum-magnesium unfired bricks are a qualitative leap. In addition to using high-purity raw materials (corundum, high-purity fused magnesia and high-purity aluminum-magnesium spinel, etc.), the binder also uses a high-performance composite binder.
High-grade aluminum-magnesium unfired bricks have achieved good results in the use of ladle, and their service life has reached or even exceeded that of carbon-containing ladle lining bricks, while reducing the carbonization of molten steel. For example, the aluminum-magnesium unfired bricks developed by a refractory material company in Henan Province are used in the 100t ladle and LF refining ladle of a steel plant, and their service life is 1.5 times that of aluminum-magnesium carbon bricks.
Anshan Iron and Steel’s 200t ladle uses aluminum-magnesium unfired bricks, and the service life of the ladle is more than 110 times, with the highest reaching 128 times. The service life of the 170t continuous casting ladle reaches 119 times, exceeding the aluminum-magnesium carbon bricks. Baosteel’s 300t continuous casting ladle stopped using aluminum-magnesium carbon bricks in June 1998 and began to use 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 for high-grade aluminum-magnesium (spinel) castables include corundum (fused corundum, sintered corundum, etc.), high-purity fused magnesia, high-purity aluminum-magnesium spinel (fused and sintered), etc. The binders include pure calcium aluminate cement, Al2O3 powder, high-purity SiO2 powder, etc.
Since December 1996, 300t steel ladles have been using high-grade aluminum-magnesium castables developed by several refractory material factories in my country. 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.
The steel plant’s 200t continuous casting ladle uses high-grade aluminum-magnesium (spinel) castables with a service life of 150 times. Other steel plants have also used castable precast blocks and achieved good results. For example, the service life of Bengang’s ladle using aluminum-magnesium carbon bricks was 65 times. After switching to high-grade aluminum-magnesium spinel precast blocks, the average service life increased to 118 times, and the highest reached 126 times.
