In the past, hot gunning material, hot baking material, etc. have been used as hot repair material for repairing damaged portion of furnace wall, furnace bottom, etc. in various types of refinery furnaces, containers, etc. such as converter, AOD (argon oxygen degassing) furnace, electric furnace, LF ladle, etc. To produce this type of hot baking material, refractory material such as dolomite, magnesia, etc. is kneaded with coal tar binder, and mass of this material having some consistency is supplied and brought into contact with the damaged portion in the furnace through furnace inlet after molten steel has been delivered in case of converter and the baking material is molten, spread and developed by heat inside the furnace and the damaged portion is repaired.
The properties required for this type of baking material are: no change over time, good spreading property in hot working process, good adhesive property, high durability, and short baking and hardening time. The baking material produced by the use of coal tar binder has no problem in such factors as the change over time, spreading property, and durability, while it is disadvantageous in that longer hardening time is required.
In this respect, to overcome the problem of long baking time of the conventional paste type baking material using coal tar binder, a slurry type baking material has been proposed to reduce the baking time. This material has viscous and fluidizing property and uses liquid novolak type phenol resin, and satisfactory effect has been attained (JP-B-5-41594 and JP-B-6-31161). Because solvent is contained in the phenol resin solution, there are less carbon components when it is carbonized. For this reason, it has such problems that it has lower strength when hardened and it is subject to changes over time due to sedimentation and separation of coarse particles during storage because it is a baking material having viscous and fluidizing property.
Also, a powder type baking material has been proposed (JP-A-4-170370) to reduce the baking time and to improve durability. This is produced as follows: A mixed powder type basic refractory material is coated with pitch and/or creosote oil, and to this powder material, aromatic petroleum resin containing heavy oil and C.sub.9 fraction as main components is added as auxiliary combustion agent and wetting agent. By this material, it is possible to reduce the hardening time and it can also provide high strength by carbon bond when it is hardened. However, it has such problems that it is solidified during storage in summer season because of creosote oil or heavy oil, which are added as auxiliary combustion agent and wetting agent.
Further, another type of baking material has been proposed (Japanese Patent Publication No.2555850), which is produced by adding a material to form carbon bond in hot working process and also by adding lactam as auxiliary fluidizing agent. However, it has disadvantages in that lactam has high deliquescence and is changed to polyamide through ring-opening polymerization in the presence of water and alkali metal and it is also solidified during storage in summer season or under high temperature and high humidity conditions.
Still another baking material has been proposed (JP-A-8-169772), which is produced by adding diphenyl or diphenylamine as auxiliary fluidizing agent to a material to form carbon bond in hot working process. However, its adhesive strength is not high enough compared with the conventional products.
It is an object of the present invention to provide a hot repair mix, which is suitable for use to carbon bonded brick such as magnesia-carbon brick used in various types of refinery furnaces and which has sufficient adhesive property with base material and durability suitable as repair material. Further, it forms carbon bond in hot working process, shows neither sedimentation separation nor changes over time, has high spreading property in hot working process, is shorter in the baking time after the processing and has high durability.