Abstract: In a method of cooling a tank molded from thermoplastic plastic material, a molded tank is received from a metallic die assembly at a temperature somewhat lower than a melting point of the plastic material, the molded tank is retained in a jig frame, and cooling water is sprayed onto an external surface of the molded tank. Preferably, the method further comprises the step of blowing cooling air into the tank substantially at the same time as spraying cooling liquid onto an external surface of the molded tank. Thus, the molded plastic tank can be removed from the metallic die assembly at a relatively high temperature, and the use efficiency of the metallic die assembly can be improved. Also, because the tank is not subjected to any pressure or buoyant force, it is prevented from undesirably distorting. In particular, by blowing cooling air into the tank, the tank can be cooled even more quickly.

Abstract: In a method of cooling a tank molded from thermoplastic plastic material, a molded tank is received from a metallic die assembly at a temperature somewhat lower than a melting point of the plastic material, the molded tank is retained in a jig frame, and cooling water is sprayed onto an external surface of the molded tank. Preferably, the method further comprises the step of blowing cooling air into the tank substantially at the same time as spraying cooling liquid onto an external surface of the molded tank. Thus, the molded plastic tank can be removed from the metallic die assembly at a relatively high temperature, and the use efficiency of the metallic die assembly can be improved. Also, because the tank is not subjected to any pressure or buoyant force, it is prevented from undesirably distorting. In particular, by blowing cooling air into the tank, the tank can be cooled even more quickly.

Abstract: An anti-oxidation agent for preventing oxidation of a stainless steel strip during continuous annealing comprising a colloidal inorganic substance which can be crystallized at a temperature not higher than 1300.degree. C. at least one compound having a melting point not higher than 1300.degree. C., selected from the group consisting of silicates, borates and phosphates, a dispersion agent, and the balance substantially water. The anti-oxidation agent is applied to the surface of the stainless steel strip. During the annealing, the anti-oxidation agent enhances the heat absorption so that the stainless steel strip temperature is elevated to the annealing temperature in a short time. The anti-oxidation agent on the strip surface forms a film of a fine structure which keeps the strip surface away from oxidizing components of the annealing atmosphere so as to suppress generation of oxide scale. The film is easily separated due to thermal contraction in the course of the cooling after the annealing.

Abstract: A descaling method for removing oxide scale from a hot-rolled stainless steel strip. A solution of an alkaline earth metal chloride is applied to the surface of the oxide scale layer formed on the hot-rolled stainless steel strip, and the solution is allowed to penetrate into the oxide scale layer. In a subsequent annealing, the solution is heated and dehydrated to become solid matter and the dehydrated matter is melted and diffused into the oxide scale layer to soften the oxide scale layer. The oxide scale layer is then removed by a simple mechanical descaling by, for example, grinding brushes with or without a subsequent chemical descaling by a weak acid solution.