SU789223A1 - Centrifugal casting method - Google Patents

Description

This invention relates to a foundry production of ferrous and non-ferrous metals, namely, centrifugal casting. The known method of centrifugal casting of blanks from ferrous and non-ferrous alloys with the supply of low-melting exothermic flux-forming mixtures in a pulverized state directly into the rotating form, which both bakes refining of the cast alloy from harmful impurities and non-metallic inclusions 1. The disadvantages of this method are the high consumption of mixtures, the intensive formation of dust and gas and the freezing of the flux on the casting device, which reduces their durability and refining capacity of the flux. There is also known a method of casting steel using exothermic flux-forming mixtures in granules, which & e is introduced onto the mirror of the inlet in the process of filling the incinerator 2. The disadvantage of this method is the low degree of refining of cast steel, since the optimum surface interaction of the metal with the flux is not achieved. The purpose of the invention is to develop a method for centrifugal casting of pipes and billets, which ensures an increase in the quality of casting due to an increase in the degree of refining of metal from harmful impurities and non-metallic inclusions. The goal is achieved. The granules are fed into the zone of the annular flow formed by the jet of the melt being poured at an angle of 15-60 to the axis of rotation of the mold. The drawing shows the device for the implementation of the method. The metering device 1 of the centrifugal machine is filled with granules 2 with a diameter of 4-8 mm. Liquid metal 4 is poured into the rotating mold 3. 2-3 seconds after the start of pouring the metal, c. using sensors and actuators on an inclined feeder 5 using a metering device serves for 5-8 s in the rotational form of the granule at the rate of 1.5% of the weight of the Poured Metal. By changing the angle within 15-60, the granules are directed to the zone of the annular flow 6, the most active from the hydrodynamic point of view, the zone where the most favorable conditions for flux emulsification in the metal occur in order to increase the surface of their interaction and, as a consequence, increase the degree of refining metal from harmful impurities and non-metallic inclusions.

In the zone of the ring flow, the granules ignite, forming a liquid synthetic flux, which due to the turbulence of the flow emulsifies in the metal and assimilates non-metallic inclusions and harmful impurities. The flux after refining the metals by centrifugal forces is carried out on

its free surface. As a result of metal refining, scrap is reduced by nonmetallic inclusions by 2-3 times and overall scrap is reduced by 1.2-1.5 times.

The angle from the supply of the granules provides their supply to the zone of the annular flow, the driving force in the turbulent mode and depends on the speed of pouring the metal. In tab. 1 shows the dependence of the angle of supply of granules on the speed of pouring metal.

Table 1

Feed angle,

60-50 49-40 39-30 29-20 19-15 granules, hail

When the angles of supply of granules are more than 60, they fall on the end of the form, mine its working surface, and when the angles of supply are less than IS, the granules do not flow into the annular metal flow at all values of the metal pouring speed.

The application of the proposed method allows to obtain centrifugally cast billets with a low content of non-metallic inclusions such as sulfide oxides and phosphides — the content of these inclusions is reduced by 1.5-2 times, and the total scrap is reduced by 1.2-1.5 times.

Example. Two batches of billets are cast, three castings each, with the feed of granules by the proposed method

The cast iron grade MF 24-44 is melted in an MGP-102 induction furnace. At 1350 ° C, cast iron is poured into a rotating form with a speed of 1200 rpm, at 1 Centrifugal casting with feeding the granules onto 2 metal mirrors directly in the mold (known method) 3 4 Centrifugal casting with feeding the granules at an angle of 55 ° to the horizontal axis of rotation 5 form (the proposed method) 6

This casting length is 300 mm, the outer diameter is 140 mm, the wall thickness is 20 mm, the pouring speed of the metal is 2 kg / s.

Granules with a diameter of 4-8 mm are fed at an angle of 55, which provides flux formation in the zone of turbulent motion of the metal in the annular flow.

The chemical composition of the granules, wt. %: silicocalcium-8, aluminum - 12, sodium nitrate -14, silicate-lump-g20, fluorspar-26, dross 20.

The preparation of the granules is carried out on a special granulator. The mold is formed of a loose lining consisting of sand and zircon. Lining thickness 3 mm.

The results of a study of experimental castings are given in tab. 2.,

Table 2 Near the inner surface of the casting, nonmetallic inclusions reach 0.5–1 mm, sulfur and manganese are removed to the center of the casting. The average content of non-metallic inclusions is 0.25%. Sulfides and other inclusions are distributed evenly throughout the thickness of the casting. The maximum size of inclusions is 0.1 mm. Phosphide eutectic has increased hardness, manganese and sulfur are not leveled.

As can be seen from the table. 2, the proposed method of centrifugal casting under flux provides effective refining of liquid iron with flux from large sulphides, a uniform distribution of nonmetallic flows through the thickness of the casting and reduces the segregation of chemical elements in the casting.

Using the proposed method of centrifugal casting provides an increase of 10-15% mechanical and operational properties of products by increasing the degree of refining of the alloy from non-metallic inclusions and reducing by 1.2-1.5 times the total casting by reducing large non-metallic / inclusions, which transfer from metal to flux.

The economic effect is 2-2.5 p per 1 ton of suitable casting.

Claims (2)

1. USSR author's certificate 5 532465, cl. On 22/13/00, 1975. 2. USSR author's certificate number 359092, cl. In 22 D 27/06, 1969.