SU1320015A1 - Method of inoculating cast iron in mould - Google Patents

Abstract

The invention relates to foundry, in particular to the modification of cast iron in a mold. The purpose of the invention is to improve the quality of differential iron castings using modifying additives of one fractional composition - achieved by pouring the melt through one hundred to 1 modifier 2, divided into layers by gasifying plates 3, placed in the reaction chamber 4. The modifying additive is dissolved in layers. Magnesium is introduced into the volume of the plates during their manufacture in the form of i-wound, supporting the effect of modifying during the transition from layer to layer of additive. The number of layers d. at least three. 1 silt, 1 tab. with sh (L

Description

X / XU "/ X //,

01

one . one

The invention relates to foundry, in particular to the modification of cast iron in a mold.

The purpose of the invention is to improve the quality of differential iron castings using modifying additives of one fractional composition in all its parts. Portions of the modifying additive in the reaction chamber are arranged in at least three layers. Plates of lightweight material, mainly expanded polystyrene, are placed between the layers. Magnesium granules are distributed in the amount of these plates in the amount of 4–9% by weight of the plates.

The drawing shows the implementation of the proposed cnocoda.

The melt through a hundred to 1 is poured into the gating system. It interacts with modifier 2, which is divided into at least three layers by the burning plates 3. Mutual

effect of the melt with the modifier pro25

35

40

proceeds in the reaction chamber 4. When liquid molten iron interacts with the overlying modifier layer, it is washed out and dissolved. The thickness of the modifier layer is unevenly reduced: from the melt inlet side into the chamber faster due to the faster heating of the modifier and the presence of a dynamic velocity component the incoming flow is liquid, and from the melt inlet side of the chamber, more slowly. Therefore, in the final stage of interaction of liquid cast iron with the sm modifier of the layer, when the area of their contact decreases, the modifier is completely washed out from the entrance to the chamber, and the liquid cast iron through the channel that formed as a result of the destruction of the polystyrene insert comes to the surface of the next layer and also washes on both sides of the remaining modifier of the previous layer. This makes it possible to increase the surface interaction of the liquid iron with the modifier and thereby level the content of the modifier in the iron over the entire period of filling the mold. However, when going from one layer of the modifier to the next one, the mass fraction of the modifier in the cast iron decreases due to insufficient heating of the back side of the previous one and the surface of the next layers.

50

55

152

This reduces the magnesium content in the iron. The mechanical properties of cast iron are also reduced in the appropriate places.

castings.

To eliminate this drawback, granulated magnesium is introduced into the polystyrene plate during manufacturing. During the period of filling the gap between the layers, it interacts with liquid iron and increases the magnesium content in the melt. This makes it possible to virtually eliminate the non-uniformity of the modified cast iron in the transition from one layer of the modifier to the next.

Reducing the number of layers of the modifier (less than three) leads to an increase in the thickness of the modifier layer, slows down the process of dissolution of the modifier and penetration of liquid iron to the polystyrene insert, which leads to heterogeneity of the microstructure, reduction and heterogeneity of mechanical properties over the section and height of the casting.

A decrease in the magnesium content in the polystyrene plate below 4% leads to the formation of local volumes in the casting with an underestimated magnesium content and, as a consequence, to a decrease in the mechanical properties of the iron in these volumes.

An increase in the magnesium content above 9% leads to an additional consumption of magnesium, the possible release of metal from the gating system, and the appearance in local volumes of free-structured cementite.

The thickness of the modifier layer in the reaction chamber can be determined by the formula

Bt

(1 +

and) -

g de hp is the initial height of the modifier in the reaction chamber without taking into account the thickness of the plates; L - permissible deviation of Mg content from the average value,%.

The number of plates n is determined according to the expression

P

(I

- one) ,

and the thickness of the plates is determined from the condition of the possible filling of the channel formed by the polystyrene foam

313

plate, and can be in the range of 5-10 mm, and reducing plates of less than 5 mm can lead to stopping the flow of metal, and an increase of 10 mm leads to an unreasonable increase in metal consumption.

For example, with h 90 mm; z) j t-5%; J j -10% thickness of the layer modifier

g

h

0.3 90 (1 + 0.05)

0.3- 90 g (1 - 0.1)

 22 mm;

41 mm.

Hence the number of polystyrene plates.

90 22

90

41

3 pcs;

- 1) 1 pc.

Example. The test is carried out in the manufacture of the housing of a worm gearbox made of cast iron with a spherical shape of graphite, having the following dimensions, mm: height 600,

Indicators

The number of codifier layer in the reaction chamber I

1.2

1.05 1.05 - 1.05

150

540-495

3.6-1.8

247-195

3.0 4.0

132

120

9.0

112

540-510 560-520 575-562

4.4-3.1 4.4-3.8 7.1-6.7 235-205 228-224 230-228

Amount of ferrite

in cast iron, Z 56-30

54-36

53-47

five

fO

J5

20

25

154

width 620 and length 750. The mass of the casting is 245 + 5 kg.

As the initial cast iron for modification, use is made of cast iron of the following composition, wt%: C 3.3-3.4; Si 1.45-1.50; Mp 0.25-0.3; Ni 0.05; Cg 0.04; P 0.07; S 0.02-0.03.

The cast iron is melted in an electric arc furnace. Polystyrene plates 5–7 mm thick are used as gas-setting plates, which are obtained by an autoclave method (0.2–0.4 MPa, sintering time — 4 min, cooling — 6 min) from PSV-L previously foamed polystyrene foam. fractions 0.5–1.0 mm in water (water temperature 370 K, foaming time 3 min) and mixed with 4–9% magnesium granulated PGM fraction 0.05–0.1 mm.

The LCDM-2 alloy was used as a complex modifier. The temperature of the cast iron in the form 1680-1700 K.

The table shows the data on the modification of cast iron in the form, microstructure, and physicomechanical properties of cast iron.

1,03 1,05 1.05 1,05

9.0

6.0

11.0 8.0 6.0

115

370-535

7.2-6.6 232-227

33-50

139151115

360-520535-490560-535

4.3-2.9-3.5-1.7.5.0-4.2

232-198243-190228-221

35-34

34-29

54-18

513

In method 1, the content of mag: neither in the plate is less than 4%, and in method 5 - more than 9%. In the implementation of methods 6 and 7, respectively, used two and six layers of the modifier.

From the data of the table it can be seen that the proposed method of modifying cast iron reduces the maximum difference in the chemical composition of cast iron in magnesium and silicon in various parts of casting from 160 to 112-120%, reduces the difference in tensile strength of cast iron from 10 to 2.5-6.5%, in the magnitude of elongation - from 200 to 7-35% and hardness (HB) - from 26.0 to 2, O-15%. A study of the microstructure of cast iron from various parts of the castings showed that the proposed the modification method allows to obtain in the microstructure a small difference in the number of fer ita.

Editor E.Sligan

Compiled by T. Korolev

Tehred N.Glushchenko Proofreader A.Ilyin

Order 2559/12. Circulation 740 Subscription

VNIIPI USSR State Committee for Inventions and Discoveries 4/5, Moscow, Zh-35, Raushsk nab. 113035

Production and printing company, Uzhgorod, st. Design, 4.

five

0

156

Claims (1)

Invention Formula A method of modifying cast iron in a mold, which involves passing the melt through a reaction chamber with a modifying additive, which is characterized by the fact that, in order to improve the quality of differential iron castings using a modifying additive of one fractional composition in all its parts, a part of the modifying additive have in the reactor chamber at least three parallel horizontal layers, between which plates of lightweight material are installed, preferably foam listirol, with magnesium granules distributed in the volume of these plates in the amount of 4–9% of their mass.