GB513467A - Improved manufacture of cylinders and cooling jackets of internal combustion engines - Google Patents

Abstract

513,467. Alloys; heat-treatment. RENAULT, L. Feb. 12, 1938, No. 4463. Convention date, April 28, 1937. [Classes 72 and 82 (i)] Cylinders and cooling-jackets forged from a steel containing 0.85-1.25 per cent. of carbon and 1.5-2.4 per cent. of manganese (which may be partly-replaced by nickel or chromium in the proportion of two parts of nickel or chromium to one of manganese) are heated to obtain a homogeneous structure and softening of the metal, machined, heated to just above the Ac3 point to bring the metal into the austenitic state, quenched in a hardening bath at such a temperature that no transformation from the austenitic state takes place in the bath and finally cooled to effect the martensitic transformation. The above-referred to homogenizing treatment may consist of a heating for half-an-hour at 920‹C. followed by air-cooling and a reheating for half-an-hour at 790‹C. followed by slow cooling at 4‹C. per minute down to 550‹C. During machining a slight excess of material is left in the bore to permit rectification and final polishing after hardening : after machining the cylinder &c. is protected from decarburization by the use of an inert, reducing or carburizing atmosphere or by heating in a salt or lead bath or by coating with copper, aluminium or the substance known under the Registered Trade Mark " Bakelite." The hardening may consist of heating to 700‹C., then to 740-820‹C. and plunging in a bath of molten salt, e.g., the eutectic of sodium andpotassium nitrates at 300-400‹C. tongs to prevent distortion being used. The piece is then cooled in still air and tempered at 250‹C. for an hour. The cylinder is then cadmium-plated. The steel may also contain 0.1 or 0.15 per cent. of vanadium and up to 0.5 per cent. of molybdenum which may be wholly or partly replaced by three times the quantity of chromium or tungsten. According to the Specification as open to inspection under Sect. 91, the vanadium content may be wholly or partly replaced by titanium or aluminium. This subject-matter does not appear in the Specification as accepted.