SU1571094A1 - Inoculant for cast iron castings - Google Patents

Abstract

The invention relates to the metallurgy of alloys, namely to alloys (master alloys, modifiers) for doping, and can be used in the manufacture of thin-walled castings from gray iron. The purpose of the invention is to improve the machinability of castings by completely eliminating chill. The modifier contains the following components, wt.%: Silico-metalmet 5-12

ferrosilicobarium 28-40

graphite else. 1 tab.

Description

The invention relates to the field of metallurgy of alloys (master alloys, modifiers) for doping and can be used in the production of castings from gray cast iron, in particular, castings of parts of working bodies of submersible centrifugal pumps for oil production, i.e. castings with wall thickness up to 5 mm ..

The purpose of the invention is to improve the machinability of castings by completely eliminating chill.

Cast iron containing,% May: carbon 3.5; silicon 2.0; manganese 0.6; chromium 0.12; sulfur 0.03; the rest is iron.

The iron is melted in an ISTT40 induction furnace. After melting, the cast iron is superheated to 1500-1520 ° C, carried out, the processing proposed by the modifier and the modifier-prototype.

After entering the modifier in the amount of 0.6% of the mass of molten iron and overheating it to 1500-1600 ° C, the cast iron was thoroughly mixed, the filling of the casting ladle and the metal were cast into forms,

Dry forms are cast into thin-walled castings of parts of the working parts of centrifugal pumps — an impeller, a guide apparatus, on which hardness is measured, the presence of chill is detected on the thin edges (blades) and the processability of the castings is evaluated. Simultaneously cast technological samples for chill and determination of the nature of macro-1 fracture. Experimental batches of castings are not subjected to heat treatment (annealing). The machinability of pilot batches of castings is evaluated by the durability of cutting tools, their heating, dulling and failure during operation on

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ate

J

same mode depending on the number of machined parts. .

The results of comparative tests of pig iron smelted with the addition of the proposed modifier and the known one are shown in the table.

The composition of the known modifier includes 15-50% of silica-metal, 30-v35% of which is the sum

rare-earth metals. At a modifier consumption of 0.4–0.8% (on average, 0.6% by weight of the molten metal, 0.09-0.3% of siliconomimetal is introduced into the cast iron at approximately 0.03–0%,% 2RZM. In these limits An increase in the addition of silico-metal leads to an increase in the chill on the edges of thin-walled castings due to an overdose of rare-earth metals in the pig iron, when their graphitizing effect is replaced by carbide-forming. silico Ishmetal (compounds 7-8) castings have chill (2-3 mm), which leads to poor machinability. At the same time, such castings have low mechanical strength due to large additions of graphite and, accordingly, the presence of large sizes of graphite in the cast iron structure , which leads to cracks and breaks during their machining.

Therefore, the main disadvantage of the known modifier is the presence of chill on the sharp edges of thin-walled castings, which makes it difficult or impossible to machine them without performing a heat treatment operation.

The modifier contains 5-1 2% silico-isom-metal. When the modifier is consumed on average 0.6% of the mass of liquid iron, 0.03-0.0272% of silico-metal or 0.01-0.0222%, i.e. within the limits of the most effective graphitizing effect (compounds 9-20).

50

55 60

65 70 75

80

0.30

0.27 0.24

0.21 0.18 0.15

0.12

0,100,30

0.090.33

0.080.36

0.070.39

0.060.42

0.050.45

0.040.48

12

II 9

15

20,120

180

250

Castings are not machined.

Overheating of the cutting edges of the incisors and their breakdown

Cracks and breakage of castings on edges

Failing to work out. due to chill

Workability is good

As can be seen from the table, the proposed modifier (compounds 9–20) contains a mixture of components of graphite, ferro-shhkobary and silico-ismetmetals in optimal ratios mutually reinforcing each other, which makes it possible to obtain castings without thinning in the thinnest edges of castings most of all, it allows to simplify the technology of their obtaining by eliminating the labor-intensive and energy-intensive heat treatment operation.

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Claims (1)

Claims Modifier for iron castings, including silico-metal and graphite, characterized in that, in order to improve the workability of castings by completely eliminating chill, it additionally contains ferrosilicobarium in the following ratio of components, wt.%:. Silikomishmetall5-12 Ferrosilicobarium28 - 40 GraphiteExtra