RU2365660C1 - Cast iron - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly to the composition of cast iron used to cast cylinder block for the vehicles with increased lift capacity. Cast iron contains, wt %: carbon 3.15-3.30; silicon 1.2-1.7; manganese 0.7-1.0; chromium 0.4-0.6; nickel 0.02-0.2; copper 0.6-0.9; titanium 0.03-0.08; zirconium 0.03-0.08; strontium 0.03-0.1;the rest is iron.

EFFECT: output of the cast iron with a high wearing capacity.

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Description

The invention relates to the metallurgy of foundry, in particular to the development of cast iron compositions for castings of cylinder blocks of heavy vehicles.

Known gray cast iron containing, wt.%:

carbon 2.8-4.2 silicon 1.3-3.0 manganese 0.3-0.8 phosphorus 0.5-1.6 sulfur 0.03-0.1 chromium 0.1-0.3 nickel 0.05-0.15 titanium 0.01-0.05 aluminum 0.02-0.06 molybdenum 0.03-0.1 calcium 0.01-0.05 vanadium 0.05-0.15 iron rest

(SU 1006531 A, 03/23/1983, IPC С22С 37/10).

Closest to the claimed is cast iron, containing, wt.%:

carbon 3.4-3.9 silicon 1.2-1.7 manganese 0.7-1.0 chromium 0.4-0.6 nickel 0.02-0.2 copper 0.6-0.9 titanium 0.03-0.08 aluminum 0.01-0.05 zirconium 0.03-0.08 strontium 0.03-0.1 antimony 0.01-0.08 barium 0.01-0.05 calcium 0.01-0.05 sulfur no more than 0,06 phosphorus no more than 0,1 iron rest

(RU 2281982, C22C 37/10).

The specified cast iron also has insufficient wear resistance.

The claimed technical solution is aimed at increasing the wear resistance of the obtained cast iron with dimensions of graphite inclusions in the range of 90-120 microns.

To solve this problem, we propose cast iron containing carbon, silicon, manganese, chromium, nickel, titanium, copper, zirconium, strontium and iron in the following ratio of components, wt.%:

carbon 3.15-3.30 silicon 1.2-1.7 manganese 0.7-1.0 chromium 0.4-0.6 nickel 0,0,2-0,2 copper 0.6-0.9 titanium 0.03-0.08 zirconium 0.03-0.08 strontium 0.03-0.1 iron rest.

The limits of carbon content in cast iron are determined in order to obtain in the structure of cast iron a large number of small inclusions of graphite (PGD 90-120 microns). If the carbon content is less than 3.15 wt.%, The size of graphite inclusions of PGD will be less than 90 microns, which can lead to increased cracking. If the carbon content is more than 3.3 wt.%, The size of graphite inclusions will be more than 120 microns, which will lead to a sharp decrease in hardness.

The silicon content in cast iron was chosen for the same reasons, as well as because of the need to obtain a pearlite structure with a pearlite dispersion of 0.1–0.3 μm. When the silicon content is less than 1.9 wt.% In the structure of cast iron, free iron carbides (cementite) are obtained, while "thin" is formed in thin sections. With a silicon content of more than 2.3 wt.%, The size of graphite inclusions of PGD will be more than 120 μm, which will lead to a sharp decrease in hardness.

Manganese is converted into pig iron from charge materials as a constant component of pig iron. With the selected composition of cast iron, the indicated limits of manganese (0.7-1.0 wt.%) Are defined as a condition for obtaining castings with a low sulfur content and with high mechanical properties in the cast state both in thin-walled (with a low manganese content) and in thick-walled (at the upper value of manganese) castings. With a manganese content of less than 0.7 wt.%, Hardness decreases, with a manganese content of more than 1 wt.%, The morphology of graphite worsens.

The chromium content in the range of 0.4-0.6 wt.% Is selected based on the considerations of producing cast iron of the required hardness and satisfactory machinability. When the chromium content is less than 0.4 wt.%, The dispersion of perlite increases and the size of graphite inclusions increases. When the chromium content in cast iron is more than 0.6 wt.%, Hardness increases and machinability deteriorates.

Copper and nickel are part of cast iron as alloying elements that strengthen the metal base and to align the structure and properties of cast iron over the cross section of castings. Nickel, in addition, increases the solubility of copper in cast iron, which has greater perlitizing and hardening ability. When the copper content is less than 0.15 wt.% And the nickel content is less than 0.02 wt.%, Ferrite is formed in the structure of cast iron, which reduces the wear resistance of cast iron. The upper copper content of 0.5 wt.% And nickel 0.2 wt.% Is limited due to the increase in hardness and deterioration of machinability.

Titanium grinds the structure, increases the strength of cast iron. With an amount of less than 0.03 wt.%, Its effect on the mechanical properties is insignificant, with a content of more than 0.08 wt.%, There is a danger of the appearance of non-metallic inclusions and a decrease in the mechanical properties of cast iron.

Zirconium in the proposed quantities grinds the crystalline structure of cast iron, prevents the propagation of cracks, refines the melt in nitrogen, forming refractory zirconium carbides. At a content of less than 0.03 wt.% Its effect is negligible, an increase in the zirconium content of more than 0.08 wt.% Leads to the formation of a large number of zirconium carbides and nitrides, which are brittle phases that worsen the properties of cast iron.

Strontium promotes graphitization of cast iron, significantly reduces the formation of "whitened" in thin-walled castings. When the strontium content is less than 0.03 wt.%, Its effect is negligible, when the strontium content is more than 0.1 wt.%, The strength of cast iron decreases.

Tests of the proposed cast iron were made at the foundry of OJSC "KAMA3-Metallurgy". Cast iron was smelted in an electric arc furnace, the necessary additives of ferroalloys (ferrosilicon, ferrochrome, ferrotitanium) and alloying elements (nickel, copper) were introduced into the furnace, and the modification was carried out by adding ferrosilicon containing strontium and zirconium to the bottom of the bucket. At the same time, granular graphite and ferromanganese were introduced to the bottom of the bucket. Vertical samples were cast with a diameter of 30 mm and a height of 250 mm, from which samples were made to study the structure, mechanical properties and hardness of cast iron. An indicator of wear resistance is the shape, distribution, size of graphite inclusions and the dispersion of perlite, which were determined by the method of quantitative metallography. The structure of cast iron was studied in the fracture zone of the samples after testing. The chemical compositions of the studied cast irons are given in table 1. The research results are shown in table 2. As follows from the tests, the proposed composition of cast iron allows to stabilize the size of graphite inclusions of a uniformly distributed rectilinear shape and reduce the perlite dispersion.

Table 1 Structure The content of elements, wt.% FROM Si Mn Cr Ni Cu Ti Zr Ba Sa Al Sr Sb S P Proposed one 3.29 1.99 0.76 0.39 0,028 0.19 0,038 0,038 0,031 0,031 0,044 2 3.2 2.12 0.85 0.48 0.15 0.35 0,052 0,068 0,088 0,032 0.056 3 3.2 2,3 0.92 0.45 0,029 0.48 0,045 0,045 0.058 0,042 0,054 four 3.16 2.22 0.73 0.52 0,045 0.32 0.058 0,052 0,075 0,054 0,063 5 3.18 2.18 0.85 0.58 0.19 0.29 0,078 0,071 0.09 0,028 0,045 6 3.18 2.15 0.66 0.53 0.14 0.22 0,034 0,041 0,081 0,025 0,048 7 3.27 2.22 0.60 0.41 0.13 0.31 0,032 0,064 0,066 0,031 0,049 Famous 8 3.82 1.25 0.85 0.58 0.15 0.75 0,052 0,048 0,038 0.015 0,046 0,07 0,035 0,032 0.056 9 3.66 1.22 0.83 0.52 0,045 0.72 0.058 0,052 0,035 0,037 0,021 0,082 0,032 0,054 0,063 10 3.42 1.68 0.95 0.58 0.19 0.89 0,078 0,071 0,028 0,038 0,038 0,089 0,032 0,028 0,045

table 2 Cast iron Physical and mechanical properties Microstructure Tensile strength, MPa Hardness HB, GPA Graphite Metal base The form Distribution PGD size Perlite PD Ferrite Proposed one 26 220 PGF1 PGr1 90-120 one hundred 0.1 0 2 27 233 PGF1 PGr1 90-120 one hundred 0.1 0 3 28 240 PGF1 PGr1 90-120 one hundred 0.1 0 four 28 230 PGF1 PGr1 90-120 one hundred 0.1 0 5 27 225 PGF1 PGr1 90-120 one hundred 0.1 0 6 26 230 PGF1 PGr1 90-120 one hundred 0.1 0 7 28 240 PGF1 PGr1 90-120 one hundred 0.1 0 Famous 8 27 233 PGF1 PGr1 250-450 one hundred 0.1 0 9 28 230 PGF1 PGr1 250-450 one hundred 0.1 0 10 27 225 PGF1 PGr1 250-450 one hundred 0.1 0

Claims (1)

Cast iron containing carbon, silicon, manganese, chromium, nickel, copper, titanium, zirconium, strontium and iron, characterized in that it contains components in the following ratio, wt.%:
carbon 3.15-3.30 silicon 1.2-1.7 manganese 0.7-1.0 chromium 0.4-0.6 nickel 0.02-0.2 copper 0.6-0.9 titanium 0.03-0.08 zirconium 0.03-0.08 strontium 0.03-0.1 iron rest.