RU2148673C1 - Cast iron - Google Patents

Abstract

FIELD: metallurgy of casting production. SUBSTANCE: invention relates to development of cast iron compositions for carcass ingots of different wall thickness. Proposed cast iron has components at the following ratio, weight %: carbon 3.0-3.5; silicon 1.7-2.2; manganese 0.5-0.8; chrome 0.15-0.3; copper 0.5-0.8; sulfur 0.05-0.12; phosphorus ≤ 0.2; barium 0.003-0.015; calcium 0.007-0.025 and iron - the rest. EFFECT: stabilization and improved cast iron properties at different carbon equivalents, decreased cost. 2 tbl

Description

 The invention relates to foundry metallurgy, in particular to the development of cast iron compositions for case castings with different wall thicknesses.

Known cast iron [1] the following chemical composition, wt.%:
Carbon - 2.5 - 2.8
Silicon - 1.8 - 2.5
Manganese - 0.3 - 0.7
Aluminum - 0.05 - 0.10
Cerium - 0.02 - 0.15
Copper - 0.4 - 0.8
Iron - Else
The disadvantage of cast iron is its low carbon content, which leads to bleaching in thin sections of castings, despite the presence of aluminum and copper.

 A cerium content of more than 0.05% in cast iron leads to the release of structural free cement, and aluminum in cast iron billets, poured into raw sand-clay forms, provokes the formation of sieve gas porosity.

Closest to the proposed cast iron in technical essence and the achieved result is cast iron [2] of the following chemical composition, wt. %:
Carbon - 3.15 - 3.35
Silicon - 2.20 - 2.40
Manganese - 0.6 - 0.8
Chrome - 0.2 - 0.3
Nickel - 0.1 - 0.35
Sulfur - Up to 0.12
Phosphorus - 0.18 - 0.25
Iron - Else
The disadvantage of this cast iron is the absence of a lower limit for the sulfur content, which makes cast iron with a sulfur content of less than 0.05% less susceptible to modification, and the presence of a large amount of manganese and chromium at a given nickel content at a low carbon equivalent leads to the appearance of structure-free cast iron in the structure cementite and high hardness, which leads to a deterioration in machinability and embrittlement of shaped castings. At high carbon equivalents, a high silicon content leads to the appearance of ferrite, low hardness and low mechanical properties of castings.

 The aim of the present invention is to stabilize and increase the level of properties of cast iron at different carbon equivalents.

This goal is achieved in that the cast iron containing carbon, silicon, manganese, chromium, sulfur, phosphorus and iron, additionally contains copper, barium and calcium in the following ratio, wt.%:
Carbon - 3.0 - 3.5
Silicon - 1.7 - 2.2
Manganese - 0.5 - 0.8
Chrome - 0.15 - 0.30
Copper - 0.5 - 0.8
Sulfur - 0.05 - 0.12
Phosphorus - ≤ 0.2
Barium - 0.003 - 0.015
Calcium - 0.007 - 0.025
Iron - Else
Analogues containing the distinguishing features of the proposed technical solution were not found.

 At GAZ, in the conditions of the laboratory research department, in the foundry, experimental comparative melts were conducted with the well-known and proposed cast iron. Cast iron was smelted in an induction furnace IST-016 with acid lining. As a charge, pig-iron pig irons, SCh25 cast iron return, steel waste, cathode copper and ferroalloys were used. Barium was introduced as FS65Ba4, and calcium as silicocalcium.

The metal was overheated in a furnace at 1500 ^o C and samples were poured: a wedge on bleached, blanks for mechanical properties and fluidity.

 In the table. 1 shows the chemical composition of the proposed and known cast irons.

 In the table. 2 shows the values of mechanical properties, the depth of the bleached wedge, the presence of cementite in the structure of the samples of the proposed and known cast irons. As can be seen from the table. 2, the known cast iron does not have stability in structure, hardness and depth and the level of mechanical and technological properties is low: fluctuations in hardness are very large and amount to 115 HB, the structure has cementite due to improperly selected chemical composition of cast iron.

 The proposed cast iron (table. 2, options 2-4) with different carbon equivalents bleached depth - zero, the minimum difference in hardness, a higher level of mechanical and technological (higher fluidity) properties than the known.

 With a very low content of graphitizing elements: C, Si, Cu, Ba, and Ca, cementite appears in the cast iron structure, and its hardness increases, which leads to a sharp drop in mechanical and technological properties (Table 2, option 1).

 At a high content of carbide-forming elements, despite the large carbon equivalent (Table 2, option 5), carbides reappear in the cast iron structure, hardness increases sharply, and strength properties decrease.

 Calcium content of 0.007 - 0.025% increases fluidity and graphitizes cast iron, preventing the formation of cementite.

 A lower Ca content is not enough to obtain the above properties, and a larger amount leads to unnecessary costs.

 The selected limits of barium content (0.003 - 0.01%) provide due to effective graphitizing modification the exclusion of thin-walled castings from the proposed alloy of structurally free cementite and the absence of ferrite. The introduction of Cu, Ba and Ca in cast iron at a selected ratio of the remaining elements gives a positive effect on the stabilization and increase the level of properties of the proposed cast iron.

Sources of information
1. D. N. Khudokormov, V. M. Korolev, S. N. Lekah et al. "Cast iron", auth. 1109460, cl. C 22 C 37/10.

 2. A guide to iron casting edited by N.G. Girshovich. - L .: Engineering, 1978, p. 554-555.

Claims (1)

Cast iron containing carbon, silicon, manganese, chromium, sulfur, phosphorus and iron, characterized in that it additionally contains copper, barium and calcium in the following ratio, wt.%:
Carbon - 3.0 - 3.5
Silicon - 1.7 - 2.2
Manganese - 0.5 - 0.8
Chrome - 0.15 - 0.3
Copper - 0.5 - 0.8
Sulfur - 0.05 - 0.12
Phosphorus - ≤ 2
Barium - 0.003 - 0.015
Calcium - 0.007 - 0.025
Iron - Else

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