Patent RU-94027088-A (RU)
Inventor: AKSENOV A A
IPC: F02F3/00
Filed: 1994-07-21
Abstract: FIELD: metallurgy and motor-car building. SUBSTANCE: light alloys piston for internal-combustion engines has body with inner cavity and hole for piston pin and head linked with body by metal. Head has groove for compression ring, bottom and combustion chamber. In the case at least part of head is made of compound material layer. Method of similar piston production provides for production of at least one sintered porous blank, setting the blank in casting mould, preparation of light alloy molten bath, its casting into mould, impregnation and crystallization in terms of all-round compression, removal of ingot and mechanical working. Difference of the piston design from previously known designs is that alloys based on aluminum and magnesium are used as light alloy and as compound material they use material, that has ceramic formations in the form of fibrous particles in amount of 11 - 188 vol. % and in the form of nonfibrous particles - 0.1 - 0.5 vol. %, light alloy is balance.. Based on AlO, SiO and SiC fibers are used as ceramic formations in the form of fibrous particles. In the case length of fibrous particles exceeds their diameter by more than 30 fold. Maximum size of nonfibrous particles does non exceeds three diameters of fibrous particles. Dimensions of piston corresponds to following ratios: h / D <0.58 and L/h <0.43, with D - piston diameter, L - distance from piston bottom to its inner cavity, h - distance from piston bottom to axis of hole for piston pin. Layer of compound material, part of head is made of which, has thickness B corresponding to following ratio B = t + (0.1 - 0.5) t, with t - distance from bottom to lower edge of groove for compression ring. Piston design differs from known piston designs by the fact, that bottom and combustion chamber are made of layer of compound material, thickness of which meets following ratio L - H > b > 3 mm, with H - maximum depth of combustion chamber. Groove for compressing ring is made of compound material layer or it is made of "Niresit alloy layer" (that has composition, weight % : 2.4 - 2.8 C; 1.8 - 2.4 Si; 1.0 - 1.4 Mn; 13.5 - 17.0 Ni; 1.3 - 1.6 Cr; 5.0 - 7.0 Cu; iron - balance) with thickness by 2 - 2.5 fold more, than width of groove for compressing ring. The new thing in the method of piston production, as compared with previously known methods, is that porous blank is produced from material, that has ceramic fibers and binder with temperature of melting equal to (0.5 - 0.8) of temperature of ceramic fibers melting using calcining under temperature of binder melting. Preparation of molten bath is prepared by its treatment with chlorine-bearing compositions or inert gasses under temperature by 250 - 350 C higher than temperature of liquidus and following holding for 0.1 - 0.7 under the temperature. Before casting in casting form molten bath is filtered, cooled to temperature of by 50 - 100 C higher than temperature of liquidus with speed of 100 - 200 C/s and crystallization is carried out with cooling speed of 200 - 350 C/minute and pressure of 150 - 200 MPa to temperature of (1.2 - 1.4) temperature of solvus with following pressure removal. Blank of Niresit alloy, that is also set in casting mould, is preliminary subjected to shot-blasting treatment for 5 - 10 minutes with following clearance in fat-removing solution using ultrasonic treatment in cavitation mode and holding in molten bath of light alloy under temperature of 700 -750 C for 5 - 10 minutes. Distinguishing properties of method also are additional treatment of molten bath with phosphorous-bearing preparations under temperature of 250 - 350 Cover temperature of liquidus and casting cooling immediately after removal from casting mould with speed of 100 - 150 C/minute with following age hardening under temperature of 180 - 220 C for 1 - 4 hours. Design and method of production allow to produce pistons with high level of physical-mechanical properties and correspondingly high operational characteristics and long service life ( minimum by 3 times) as compared with existing analogues. EFFECT: increased level of physical mechanical properties, improved operational characteristics, increased service life.