SU844637A1 - Cast iron - Google Patents

Description

(54) CAST IRON

The invention relates to the field of foundry, namely the production of ductile iron.

Known malleable cast iron containing b.w.%: carbon 2.2-2.6, silicon 1.0-1.3, manganese 0.3-0.4, phosphorus up to 0.18, sulfur up to 0.12, iron - the rest is 1.

The main disadvantage of the known composition of cast iron is a non-high level of physical and mechanical properties:

Strength of 30-37 kg / mm

Relative lengthening of 6-12%.

The closest in technical essence and the achieved result to the proposed is cast iron containing in wt.%:

3.2-3.6

Ugderod 1.6-2.6

Silicon 0.1-0.5

Manganese 0.02-0.05

Magnesium 0.01-0.05

Calcium 0.02-0.10

Copper 0.05-0.15

Aluminum Rare Earth Metals

0.01-0.06 (rare-earth metals)

2. The rest of the iron

However, in view of the comparatively high content of carbon and silicon in this iron, during primary crystallization, free graphite is released, which greatly reduces its strength and plastic properties.

The aim of the invention is to increase the strength and ductility.

ten

The goal is achieved by the fact that cast iron, carbon, silicon, manganese, magnesium, calcium, copper, aluminum, rare earth metals and iron, additionally 15 contains chromium in the following ratio of components, in weight1%

20

25

The upper limits for carbon and silicon in cast iron (2.7–30 and 1.7%, respectively) are selected with

Accounts prevent the formation of free graphite during the initial crystallization of iron and the acceleration of the process of nucleation and the increase in the number of graphite inclusions during graphiteration annealing. The lower limits of carbon and silicon (1.5 and 1,; 0%, respectively) are the edges, after which there is a significant decrease in the number of crystallization centers and the formation of an unfavorable primary structure of white iron, as well as deterioration of the foundry with alloy properties.

The manganese content in the pig iron in the range of 0.1-0.7% was chosen taking into account the preparation of the ferritic structure after the graphitizing annealing. Exceeding the manganese content in excess of 0.7% inhibits the first and second stages of graphitization, reduces the number of graphite centers and contributes to the perlithization of the metal base and the reduction of the plastic properties of cast iron. The lower limit (0.1% of the manganese content in the cast iron is selected with consideration of its minimum content in the initial charge materials.

Chromium, having a doping effect on the metal base of cast iron, increases its physical and mechanical properties. The lower limit (0.05%) of the chromium content in the cast iron is selected taking into account the onset of the manifestation of its alloying effect. The upper limit (0.15%) is the boundary after which chromium, despite the presence of elements such as carbon, silicon, copper, calcium, magnesium, RMZ in the alloy, begins to strengthen its carbide stabilizing effect, lowering the mechanical properties of the iron.

The introduction of copper into the composition of cast iron is justified by its positive effect on the graphitization process by reducing the stability of cementite. The optimal number of graphitization centers (carbon annealing) ensures high damage to the strength and plastic properties of cast iron. However, while simultaneously accelerating the first stage of graphitization, copper reduces the temperature of the eutectoid transformation and contributes to an increase in the amount of perlite during the second stage of graphitization. Therefore, its content in cast iron up to 0.10% is the limit; exceeding this limit contributes to the perlitetization of the metal base and the reduction of the plastic properties of the cast iron. When copper content in the pig iron is lower than the lower limit (0.01%), its influence on the graphitization process is insignificant.

The introduction of aluminum into cast iron is justified by the manifestation of it.

Strong graftizing effect during heat treatment. The lower limit (0.02%) is the limit, after which its graphitizing effect is most noticeable. The upper limit (0.20%) 5 is limited by the fact that exceeding it causes the release of free graphite during the primary crystallization of cast iron and has a de-pulping effect on the formation

0 graphite.

The lower limit (0.01%) of the magnesium content in the iron is the limit, after which magnesium, together with REM and calcium, begins

5 to exhibit its spheroidizing effect on the formation of graphite, enhancing the mechanical properties of cast iron. Exceeding the magnesium content in the iron over 0.05% causes the onset

Q effect of re-modifying the deterioration of the form of graphite inclusions) and, as a result, the reduction of the physical and physical properties of cast iron. Magnesium, in spite of the fact that it is a bleaching element, lowers the SUSTAINABILITY of cementite, weakens the carbide stabilizing effect of chromium and helps to accelerate the graphitization process during annealing. :

About Influence of rare-earth metals on the formation of the structure of cast iron is similar to the action of magnesium. The content of rare-earth metals in cast iron in the range of 0.01-0.10% is selected taking into account the optimal magnesium content.

5 and calcium. The action of rare-earth metals, magnesium and calcium is enhanced by their joint entry into the cast iron. Lowering the content of rare-earth metals below the lower limit of 0.01% reduces the globular effect, exceeding the upper limit (0.10%) causes the phenomenon of remodification. REM, in addition, has a doping effect on cast iron, creating additional conditions for enhancing its physical and mechanical properties.

Calcium has a graphitizing and spherical radiating effect on the structure of cast iron. Its content in the amount of 0.01-0.05% is optimal for the selected content of magnesium and rare-earth metals. Excess calcium content in the cast iron above the upper limit (0.05%) also causes a large amount of slag to form during the alloy preparation process.

The results of studies of the properties of the pig iron with respect to its composition are given in the attached test report.

QExample

Cast iron were smelted of the proposed composition and the well-known C2.

The results of the study of the mechanical properties of these cast irons are given in the table.

The smelting of iron was carried out in a high-frequency induction furnace MGI-52 at a charge consisting of pig iron and steel scrap. Liquid iron was reheated to a temperature of 1500–1520 ° C, kept for 10–15 min, and released into a bottling bucket, at the bottom of which a modifier was placed — a silicone-metal (SIMISH) containing 15-25% RMZ, 45-50% Si, 3-5% L1, 2-5% Ca, 3-5% Md, Fe the rest. Modified cast iron was poured in specimens to conduct tensile tests according to GOST 1215-59. The cast samples were rtyggued according to the mode: heating to B for 4 hours, holding at this temperature for 9 hours, then cooling to 760 ° C for 1.5 hours and slow, cooling from 760 to 8 hours, further cooling to 100-200s for 4 hours. In parallel with the manufacture of the cast irons proposed, the known cast iron was cast 2. The heat treatment mode of the byg is similar to that of the cast iron of the proposed composition.

The results of the studies show (table) that the cast iron of the proposed composition has a strength of 7-11 kgf / mm, and an elongation of 1.5-2.0 times INIR than the known cast iron 2.

The use of cast irons of the proposed composition makes it possible to reduce the weight of parts by 10–15% while simultaneously increasing their weight and durability by 20%.

The economic effect of using the cast iron of the proposed composition is 90 rubles for each ton of suitable casting.

Claims (2)

1.Aronovich MS, Lakhtin Yu.M. Fundamentals of metaplovedy and heat treatment. M., 1952, p. 2. USSR author's certificate hf 643638, cl. C 22 C.37 / 10, 1977.