GB606540A - Improvements in methods of flame-cutting or flame-desurfacing metal bodies - Google Patents

Abstract

606,540. Cutting by fusion. LINDE AIR PRODUCTS CO. Jan. 15, 1946, No. 1418. Convention date, March 24, 1945. Addition to 568,397. Drawings to Specification. [Class 83 (iv)] In a method of flame cutting or desurfacing metal bodies, such as non-ferrous metals or alloys, or ferrous alloys, such as nickel-chromium stainless steel, that resist the removal of the molten metal by the oxidising gas flame, which consists in carrying a pulverised adjuvant powder into the oxygen stream prior to impingement on the work, the release of oxygen being in excess of that required for complete oxidation of the adjuvant material, as described in the parent Specification, the ratio of oxygen to powder is at least between 15 and 20 cubic feet of oxygen to one pound of adjuvent material and does not exceed 100 cubic feet per pound. The adjuvant material in addition to ferro-manganese, iron, steel, alloys of iron and tin, manganese, and mixtures of manganese with steel or cast-iron, as referred to in the parent Specification, may also consist of aluminium and mixtures of ferro-manganese with iron or steel. The ferro-manganese may contain 82 per cent of manganese and 0.75 to 1.5 per cent of carbon and may form up to 50 per cent, preferably 20 per cent, of a mixture with iron powder. The iron powder may be impure and contain 90 to 95 per cent of free iron, 0.15 per cent of carbon and the balance of iron oxides. In combination with steel powder containing more than 0.15 per cent of carbon the ferro-manganese may form 20 to 30 per cent of the mixture. Between 30 and 50 per cent of ferromanganese may be used with gray or white cast-iron powder. The powders are of fine mesh so as to reduce the necessary consumption of powder in relation to oxygen consumption. The 80-20 mixture of iron and ferro-manganese may contain 10 per cent of powder between 60 and 80 mesh, 30 per cent finer than 300 mesh and the remainder in the range from 80 to 300 mesh. If an impure iron or steel, such as formed by reduction of iron ore or reduction of mill scale &c. with hydrogen, carbon monoxide or natural gas, and containing 80 to 95 per cent of iron, less than 0.2 per cent of carbon and the balance FeO, SiO<SP>2</SP>, Mn and S, is used alone, the powder should pass through a 100 mesh screen, and 70 per cent through a 200 mesh screen. It is preferable also for about 50 per cent to pass through a 300 mesh screen. It is stated that in flame desurfacing a cold stainless steel, the speed of operation with coarse steel powder may be 8 feet per minute, whereas with fine powder the speed may be 12 feet per minute and with smaller powder consumption.