SU836180A1 - Cast iron modifier - Google Patents

Description

(54) CAST IRON MODIFIER

The invention relates to foundry production, in particular, to the modification of ductile iron.

It is known to use as a modifier for ductile iron tellurium, which provides for the formation of white iron during crystallization with a high amount of graphitizing elements and significant thickness of castings. In castings with a size of 100x100x200 mm of cast iron, containing 2.65% carbon, 1.2% silicon and modified 0.01% tellurium, the fracture is half (there is a weak patchiness) f1}.

It is known to use as a modifier for ductile iron bismuth, which is adopted (T is considered to be the main bleaching additive. Its high whitening ability is combined with an absolutely insignificant slowdown of solid state graphitization 2.

These modifiers have a number of significant drawbacks. Increasing the silicon content in the pig iron as one of the ways to reduce the duration of graphitizing annealing. causes the need to increase the content of input modifiers.

those. an increase in consumption of either expensive tellurium or bismuth in short supply. The relatively low melting temperature (452, tellurium and 271 ° C in bismuth) make it difficult to introduce modifiers into the metal in its pure form, which causes their significant losses and insufficient absorption due to significant carbon loss.

The closest to the invention in its technical essence and the effect achieved is a modifier for cast iron, which is a mixture of 50 wt.% Bismuth and 50 wt.% Tellurium GZ.

However, modifying the cast iron by jointly introducing bismuth and tellurium in the form of a mechanical mixture or separately has the same drawbacks as in modifying only one of the elements, since the properties (melting point, unit weight, etc.) of each of components remain unchanged, they have almost no effect on each other's digestibility, and their losses are also large.

The aim of the invention is to improve the processability and modifying effect.

This goal is achieved by the fact that the proposed modifier contains components in the following ratio, wt.%;

Bismuth40-48

Tellurium Else The modifier contains bismuth and tellurium in the form of an alloy.

In these alloys, BijTe compounds are formed and, significantly, the elasticity (partial pressure) of tellurium and bismuth vapors decreases and, thus, improves their absorption. The effectiveness of these alloys is also enhanced due to the fact that, unlike powdered technical tellurium, they are easily crushed into pieces of the optimal size and are well absorbed by the liquid metal, since they have a greater density and quickly fall under the mirror of the liquid metal.

In addition, the melting point of the alloy (586C) is higher than that of each of the components separately, which also ensures less of their frenzy when entering into the hammer, and, consequently, better absorption and efficiency of the proposed modifier.

The modifiers are entered at two levels: 0.001% and 0.005% by weight of the liquid metal. The effect of the proposed modifier was compared with the action of bismuth and tellurium when they were introduced into the metal in a mechanical mixture at the same levels.

Alloy: bismuth - 48% tellurium - 52%

Alloy: bismuth - 44% tellurium - 56%

mixture: bismuth + tellurium

One sample was cast from the original cast iron, without entering modifiers.

The chemical composition of the modified cast iron and the description of the fracture macrostructure of the stepped samples are given in Table. 1 and 2.

Table 1

2.98 1.76 0.40 0.13 0.120.07

3.10 1.70 0.42 0.12 0.100.08 3.08 1.73 0.43 0.20 0.100.08

2.91 1.79 0.39 0.12 0.110.07

2.95 1.75 0.40 0.12 0.100.07

3.00 1.75 0.45 0.13 0.100.07

3.00 1.71 0.44 0.13 0.120.07

table 2

Cutting through the 1st stage 4 mm

SLE (Enoy blew the whole sample

Partial bleached 2 steps (I 8 mm

Through churning of the entire sample

Through chill off the 1st stage (I, mm

Partial beat off the 5th step (I 20 mm

As follows from these tables, with the same amount of input, the chill depth of the pig iron modified with the proposed modifier is greater than that of the known, which indicates a better absorption and, consequently, a more effective action of the proposed modifier.

The use of the modifier reduces its input quantity by 1.2-1.3 times to obtain bleached castings of the same thickness / as for the prototype and thereby reduces the cost of modifying in the production of ductile iron. : Formula-invention

1. The cast iron modifier, containing bismuth and tellurium, is distinguished by the fact that, with a chain of increasing modifying effect and manufacturability, it contains components in the following ratio, wt.%: Bismuth 40-48 Tellurium Else 2. Modifier pop.1 , characterized in that it contains bismuth and tellurium in the form of their alloy.

Sources of information taken into account in the examination

1. Author's certificate of the USSR 505684, cl. From 21 to 1/00, 1976.

2.Todorov R.P. The structure and properties of ductile iron. M., Metallur 5, 1974, p. 78-83.

3. Foundry production 2, 1978, p. 39.

Claims (2)

Claim 1. Cast iron modifier containing bismuth and tellurium, characterized in that, in order to increase the modifying effect. And manufacturability, it contains components in the following ratio, wt.%: Bismuth 40-48 - Tellur Rest 2. The modifier of claim 1, characterized in that it contains bismuth and tellurium in the form of their alloy.