Abstract: A method for manufacturing a high strength rail with good toughness, comprises cooling a rail to Ar.sub.3 transformation point or less after hot rolling; heating said cooled rail at a temperature of an austenite temperature zone ranging from Ac.sub.3 transformation point to 950.degree. C.; and cooling the heated rail. The chemical composition of the rail consists of 0.50 to 0.85 wt. % C, 0.50 to 1.50 wt. % Mn, 0.035 wt. % S or less, 0.10 to 1.00 wt. % Si, 0.035 wt. % P or less, 0.050 wt. % Al or less and the balance of Fe and inevitable impurities.

Abstract: A method for heat-treating a steel rail head, which comprises: heating a steel rail head to the austenization temperature; then, cooling the rail head by means of a hot water jet until a surface temperature of the rail head decreases to a temperature not below 420.degree. C.; and then cooling the rail head by means of an air jet at least to the pearlite transformation temperature, thereby transforming the structure of a surface portion of the rail head into a uniform and fine pearlite structure. The above-described method includes a method in which the rail head is previously cooled by means of a water spray until the surface temperature of the rail head decreases to a temperature not below 530.degree. C. prior to the cooling of the rail head by means of the above-mentioned hot water jet.

Abstract: In an evaporative cooling method by natural circulation of cooling water by the use of an evaporative cooling device comprising a cooling pipe fitted to an object to be cooled and a steam separator drum arranged above said cooling pipe, said cooling pipe and said steam separator drum being connected together by a downcomer and a riser, the cooling water in said cooling pipe is kept in complete liquid state and part of cooling water is evaporated only in said riser and said steam separator drum by setting parameters to satisfy the following formula:Q/V.sup.. .rho..sup.. c<.DELTA.T.sub.eq (P.sub.o, Ph.sub.3)WhereQ : Thermal load acting on said cooling pipeV : Amount of circulated cooling water in said cooling pipe.rho. : Lensity of cooling waterc : Specific heat of cooling waterP.sub.o : Pressure of said steam separator drumPh.sub.3 : Pressure of cooling water in the uppermost part of said cooling pipe.DELTA.T.sub.eq (P.sub.o, Ph.sub.3) : Boiling equilibrium temperature difference between P.sub.o and Ph.sub.

Abstract: A method of preventing occurrence of pulsation in a circulating liquid for evaporative cooling which, in the case of passing the circulating liquid received within a steam separator through a cooling stave of a blast furnace and feeding said circulating liquid back into the separator through an inlet thereof thereby to perform the evaporative cooling operation for said blast furnace, comprises the step of raising, where the fraction dryness of the circulating liquid fed back into the separator is not greater than a prescribed value, the surface level of the circulating liquid within the separator up to a position higher than said inlet, and the step of lowering, where said fraction dryness of said circulating liquid exceeds said prescribed value, said surface level up to a position lower than said inlet.