GB279149A - Improved rolls for rolling metals - Google Patents

Abstract

279,149. Corbin, F. D., Llanelly Foundry & Engineering Co., Ltd. and Nevill & Co., Ltd., R. July 7, 1926. Drawings to Specification. Annealing; case-hardening.-A roll for rolling metals is made of case-hardened alloy steel and has its case-hardened portion of a martensitic, troostitic, cementitic or allied structure and its remaining portion of a soft pearlitic or allied structure, the proportion of carbon contained in ther carburized zone being regulated so that the relative proportions of carbon and the alloying element or elements are such that, for any given percentage of such elements, the percentage of carbon shall be sufficiently high on the one hand that the carburized zone shall remain in the martensitic &c. state even after slow cooling and on the other hand sufficiently low to ensure that when nickel or manganese are the elements used, this zone shall not be in the austenitic state. Examples of the proportions of carbon and the alloying elements are as follows :-Nickel 5 per cent, carbon 0.9-1.25 per cent; chromium 7 per cent, carbon 1.4 per cent; tungsten 4 per cent, carbon 1.25 per cent; molybdenum 1.25 per cent, carbon 1 per cent; vanadium 0.75 per cent, carbon 1 per cent; manganese 3.5 per cent. carbon 0.9- 1.1 per cent; nickel 5 per cent, chromium 0.8 per cent, carbon 1 per cent. In an example a roll is made of steel containing approximately nickel 5 per cent, chromium 0.8 per cent, and carbon 0.2 per cent. The roll is annealed at a temperature of about 750‹ C., cooled to room temperature and machined. The roll is then case-hardened in a box having removable ends, side or top, being embedded in a mixture of 60 per cent of oak or beech charcoal and 40 per cent of barium carbonate, and heated to a temperature of 900‹ C. for such a period as to give approximately 1 per cent of carbon in the case of the roll. The roll is then allowed to cool in the box to a temperature below the critical point, then reheated to 840‹ C. for a considerable time, and removed from the box and allowed to cool in the air. After the first cooling, the roll may be reheated up to, and furnace-cooled from, a temperature above the critical temperature and then reheated to just below the said temperature and cooled. Specification 23331/04 is referred to.