GB1131662A - A method and installation for the thermal treatment of steel rails - Google Patents

Abstract

1,131,662. Heat-treating steel rails. LORRAINE-ESCAUT S.A. April 27, 1966 [April 28, 1965; March 11, 1966], No. 18501/66. Headings C7A and C7N. Steel rails leaving the hot rolling mill are immersed in a cooling medium maintained at constant temperature, part of the surface of the rail flange being screened from the action of the coolant so that the cooling rate is equalized over the cross-section and the temperature being such that isothermal transformation to bainite or pearlite occurs. The cooling medium may be a fluidized bed into which the rails are immersed flange uppermost with the flat face of the flange horizontal so that there forms thereon a coating of stagnant bed particles acting as a thermal insulator. Transformation may occur completely in the bed, or may be initiated therein and completed in supplementary apparatus such as a furnace. As illustrated in Fig. 1 rail A on leaving the mill is raised, inverted, and lowered into a fluidized bed in vessel 2; after holding for an appropriate period it is then removed and deposited at H. The bed may be heated, as by resistance elements 6 or other suitable means, or cooled by the passage of coolant through pipes 7, in accordance with the indication of pyrometer 8. In the embodiment of Fig. 3 (not shown) a plurality of rails are traversed through the bed for such a time that transformation is complete, while in a further modification Fig. 4 (not shown) the rail is cooled to transformation temperature in afluidized bed and is then transferred to a furnace for completion of the transformation. Fig. 5 shows a variant in which the fluidized bed is supplied by two separate wind-boxes, the first zone of the bed being cooled and fluidized with cold air while the following zone is fluidized by air heated by burner 18 under the control of pyrometer 19. The rails may contain in percentage by weight C 0À4 - 1 Mn 0À5 - 2À5 Si 0À02 - 1À8 Cr 0 - 1-5 Mo 0 - 0À5 V 0 - 0À4 Nb 0 - 0À25 Fe balance. and may be transformed at 560‹ -620‹ C. for 200- 800 secs. to achieve a pearlitic structure or at 380‹ -460‹ C. for 300-900 secs. To achieve a bainitic structure.