SU1694334A1 - Centrifugal casting of piston rings and the corresponding moulds - Google Patents

Abstract

The invention relates to the industry of foundry and can be used in centrifugal casting of piston rings made of modified cast iron. The purpose of the invention is to improve the quality of the metal, which is achieved by modifying the mold 1 of the hollow rod 2 and pouring the metal, modifier is fed into the cavity of the rod 4, and the mold is rotated at a rate of 70 90 ° C above the liquidus temperature of the metal. After 15-20 seconds after pouring, the rotation speed is increased to 1650-1750 rpm, and the cavity of the rod 4 communicates with the working cavities 3, for which, in the holes communicating the cavity of the rod 4 with the working cavities 3, quick-insert inserts 5 are installed. sp ff-ly. S Il.

Description

cl

with

The invention relates to foundry and can be used in centrifugal casting of piston rings made of modified cast iron.

The purpose of the invention is to improve the quality of the metal.

The method is as follows.

A hollow core is installed into the mold, forming the working cavities for casting the piston rings, and the mold is rotated. The rotation is carried out at a speed n less critical and is calculated from the following ratio

p (0.7-0.8) "9.6 V (q-d) (7 - dVD2, where d is the diameter of the free surface of the flow, m;

D is the outer diameter of the flow, m q is the acceleration of the force of tin, m / s.

Such a rotational speed makes it possible to chaos the movement of the metal poured into it, which, in turn, contributes to the uniform and complete assimilation of the modifier, previously, within 7–13 s, fed into the rod cavity before the liquid metal is poured into it.

The metal pouring temperature is above the liquidus temperature, which allows for modification and compensates for the heat loss in the core cavity during the mixing period.

The mixing time is 15-25 seconds, and then the rod cavity is connected to the working cavities and the rotation speed is increased to 1650-1750 rpm.

A mold device for centrifugal casting of piston rings is presented on

Os

h w with

N

FIG. 1-3. FIG. 1 is a longitudinal section; in fig. 2 is a cross-section of a stationary form; in fig. 3 is a cross-section of a shape brought into rotation.

The centrifugal casting mold consists of a mold 1, a hollow rod 2, which forms the working cavity 3 with the mold.

The core has an internal cavity 4 and channels of feeders 5, covered with quick-burning inserts 6.

On the inner cavity of the rod 2 is made of longitudinal protrusions 7. The mold is provided with a cover 8, a pouring chute 9 and a pusher 10.

An example of the implementation of the proposed method of casting thin-walled castings.

The original cast iron of chemical composition, wt.%: 3.2-3.6 C; 2.0-2.2 SI02; 0.8-1.0 MP; to 0.01 P, 0.01-0.018 S melted in an IST-0.25 furnace.

Casting piston rings with a diameter of 130 A27.05.02. 118 according to the prototype and the claimed method, centrifugal casting machines were obtained in the mold, mode 52. Six heats were carried out - one according to the prototype, five according to the claimed method. Before pouring, as in the implementation of the known method, and in the implementation of the centrifugal casting machine proposed in the mold 1, a central hollow rod 2 with radial channels 5 was installed.

The rods were made of sand-liquid glass mixture, cured by the CO-process.

In the implementation of the proposed method, the channels 5 of the rods 2 overlapped with inserts 6 thick (in mm) of polystyrene with copper coating. In the cavity 4 of the rods 2 there were four longitudinal protrusions 7 parallel to the axis of rotation of the machine. The tabs in the section are triangles 16 mm high.

In the implementation of the known method (prototype) inserts and protrusions in the rod was not.

To carry out the proposed method, the ligature modifier LCGMg2 (8% MD) pos. 11 in the amount of 0.8% by weight of the cast iron 12. The particle size of the ligature does not exceed 1.0 mm.

The mold 1 was reported to rotate at a speed ni and rotated for a time ti, then the original cast iron 12 was filled, the temperature T of which exceeded 70-90 ° above the liquidus line, the mold was rotated at the same speed and additionally randomized

the melt movement during period t2, then the inserts 6 were burned and the cavity 4 of the rods 2 was connected to the working cavities 3; the cast iron was poured into the working cavities 3

and from that moment on, the rotation of the mold was reported at a rate of P2 until the full crystallization of the castings. Then casting was made.

The value of the rotational speeds u and P2

rpm, the rotation time ti and t2 (s), the thickness of the inserts (mm), the pouring temperature T (° C), were determined by the method of planning the experiment using a computer. As a criterion for the quality of castings

The difference between the hardness values in one part was used as a parameter characterizing the uniformity of the microstructure. For this casting, PCr - 242 rpm, d 100 mm, D 142 mm.

To compare castings obtained by the known and proposed methods, the shape and size of the inclusions of graphite (PTM 23 4.427-79) in the cross section of the ring at different distances from the outer diameter were determined.

hardness and difference of hardness values in one part according to GOST 621-87. The data of comparative measurements are given in table. 2

Castings obtained by a known method and according to five variants of the proposed

method, meet the requirements of GOST in hardness, its value is 98-112 HRB. However, the difference between the hardness values in one part of the prototype and in the prohibitive zone of the optimal values of the parameters of the proposed method exceeds 4 units required by GOST.

The parameters of the fill (2-4), are given in table. 1, provide stable results in obtaining castings with uniform microstructure and uniform hardness.

Uniform hardness over the outer diameter of the ring provides uniform wear, which improves the structural and operational properties of the part.

Claims (2)

1. Method of centrifugal casting of piston rings, including installation of a hollow rod in the mold, which forms the working cavities, rotation of the mold with a rod, the metal is poured into it and rotated until the metal is fully crystallized, which is characterized by the fact that, in order to obtain castings that are homogeneous in microstructure, 7–13 s before the metal is poured into the rod5 cavity, the modifier is fed; p proposed from the following relation; p - (0.7 - 0.8) -9.6 V T / d TT / D f where d is the diameter of the free surface of the stream, m; D is the outer diameter of the flow, m-q is the acceleration of the force of gravity, m / s, and the metal is poured at an overheating temperature 70-90 ° C above the liquidus temperature, and 15-25 seconds after the metal is poured, the core cavity is connected to the workers cavities, and the speed of the mold is increased to 1650-1750 rpm. 2. A mold for centrifugal casting of the pores of the ring rings, containing a mold with a hollow rod installed in it, which forms the working cavity, characterized in that, in order to improve the quality of the metal, it is equipped with quick-burning inserts installed in the floor of the rod and communicating its internal cavity with the working cavities. Table 1 Table 2 ; / "/ && „H x XXj H fj I a j. -and U L. Jr / I 4 .. T ... d N. X X SXXXXXVXNXXX XN XN // W / 27 7 12 5 "/ &&% Ј „H x XXj // H // A N. X X YH7 four //