RU2358032C1 - Iron - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: iron contains, wt %: carbon 3.85-4.05; silicon 1.95-2.2; manganese to 0.5; chromium to 0.1; magnesium 0.03-0.06; lanthanum 0.001-0.01; calcium 0.002-0.007; aluminium 0.003-0.01; sulphur to 0.022, phosphorus to 0.1; iron - the rest.

EFFECT: eliminating shrinking defects in casts.

3 tbl

Description

The invention relates to metallurgy of foundry, in particular, to the development of compositions of ductile iron with nodular graphite for complex composite castings.

Widely known are ductile iron with spheroidal graphite, containing carbon, silicon, manganese, chromium, magnesium and other elements used for the manufacture of cast parts of machines and mechanisms. These cast irons have high strength and wear resistance, however, they have a high tendency to shrink, and therefore to the formation of shrink defects.

Closest to the proposed composition and achievable properties is cast iron [1] of the following chemical composition, wt.%:

Carbon 3.4-3.8 Silicon 2.1-2.7 Manganese up to 0.4 Chromium up to 0.1 Magnesium 0.03-0.08 Sulfur up to 0.02 Phosphorus up to 0.1 Iron rest

The disadvantage of this cast iron is its great tendency to the formation of shrinkage defects (shells and porosity), especially in complex difference castings.

The technical task of this invention is the elimination of shrinkage defects in castings from ductile iron with nodular graphite.

The technical result is achieved by the fact that cast iron containing carbon, silicon, manganese, chromium, magnesium, sulfur and phosphorus, additionally contains lanthanum, calcium and aluminum in the following ratio of components, wt.%:

Carbon 3.85-4.05 Silicon 1.95-2.2 Manganese up to 0.5 Chromium up to 0.1 Magnesium 0.03-0.06 Lanthanum 0.001-0.01 Calcium 0.002-0.007 Aluminum 0.003-0.01 Sulfur up to 0.022 Phosphorus up to 0.1 Iron rest

Analogues containing the hallmarks of the proposed technical solution was not found. At GAZ OJSC, in the conditions of a foundry laboratory, experimental comparative melts were carried out with the known and proposed cast irons.

Cast iron was smelted in an IST-016 reduction furnace with acid lining. Pig cast iron, VCh50 cast iron return, steel waste and ferroalloys were used as picts. Lanthanum, calcium and aluminum were introduced as separate ferroalloys.

The metal was overheated in an oven to 1500 ° C and core samples were poured into volumetric shrinkage with intraform modification. The amount of modifier in the reaction chamber of the shrink sample is 40 g (1.25%), fractions 1-5 mm. Known cast iron was obtained by modification in the form of FSMg5 (Si - 52%; Mg - 5.6%.

The chemical composition of cast iron from the furnace is shown in table No. 1.

table number 1 Sample number FROM Si Mn Cr P S one 3.92 1,6 0.32 0,036 0,057 0.012 2 3.93 1,59 0.34 0,035 0.058 0.014

 The chemical composition of the proposed and well-known cast irons from samples for shrinkage after intraformal modification is shown in table No. 2.

 The microstructure and hardness of cast irons were determined from samples for shrinkage (presented in table No. 3).

table number 2 Cast Iron No. FROM Si Mn Cr Mg La Ca Al P S Proposed
one 3.80 2.25 0.32 0,036 0,042 0,0009 0.001 0.002 0,057 0.012 2 3.85 2.20 0.33 0,037 0,043 0.001 0.002 0.003 0.058 0.014 3 3.95 2.1 0.32 0,035 0,044 0.003 0.004 0.007 0,057 0.012 four 4.05 1.95 0.34 0,038 0,043 0.01 0.007 0.01 0.059 0.014 5 4.1 1.8 0.33 0,035 0,048 0.015 0.008 0.015 0,057 0.012 6 3.85 2.2 0.33 0,037 0,042 0.001 - 0.003 0,057 0.012 7 3.9 2.19 0.32 0,036 0,041 - 0.002 0.003 0.058 0.014 8 3.95 2.12 0.31 0,035 0,043 0.001 0.002 - 0.056 0.012 Famous 3.78 2.1 0.35 0,037 0,041 - - - 0.059 0.012 9 10 3.80 2.2 0.34 0,040 0,046 - - - 0.056 0.014 table number 3 Cast Iron No. Microstructure according to GOST 3443-87 Hardness, HB Shrink% one 2 3 four one ShGf4.3, VGf3-Shgd25, 45-ShGr2-ShG12 P8 (Fe92) 150-170 1.78-1.95 2-4 ShGf5-Shgd15.25 - ShGr1-ShP12 P6 (Fe94) 140-155 1.66-1.69 5 ShGf5-Shgd15, 25-ShGr1-ShG12 P10 (Fe90), there are captives 140-160 1.97-2.45 6 ShGf5-Shgd15, 25-ShGr1-ShG12 P15 (Fe85) 176 3.2 7 ShGf4, 3-Shgd25, 45-ShGr2-ShG12 P30 (Fe70) 192 3.8 8 ShGf4, 5-Shgd15, 25-ShGr1-ShP2 P20 (Fe80) 183 3.0 9-10 ShGf5, 4, 3-Shgd25, 45-ShGr2-ShG10 P10 (Fe90) 150-170 3.4-4.6

The proposed amount of lanthanum, calcium and aluminum (cast iron No. 2-4, Table 2) provides the maximum effect of increasing the temperature of the melt due to their interaction with sulfur and oxygen of cast iron, which improves the solubility of the modifier, cleans the grain boundaries, gives the maximum graphitizing effect and minimal shrinkage (column 4, cast iron 2-4, table No. 3).

With an increase in the total content of lanthanum, calcium, and aluminum (cast iron 5, Table 3), the modifier is poorly absorbed, less graphite is released, the number of nonmetallic inclusions increases, and shrinkage increases.

The decrease in the content of these elements (cast iron No. 1, table No. 3) does not provide the modifier with a good desulfurizing ability, which also does not allow to obtain, when processing high-sulfur cast iron, graphite of a completely spheroidal shape.

When the carbon and silicon contents are within the limits indicated in cast iron No. 2-4, table No. 2, the shrinkage of the alloy is the smallest (cast iron No. 2-4, table 3).

With a lower content of carbon and silicon (cast iron No. 1, table No. 2), the fluidity of cast iron decreases [2] and shrinkage increases (cast iron No. 1, table No. 3).

With a higher content of carbon and silicon (cast iron No. 5, table No. 2), graphite flotation occurs and the formation of captives and shrinkage of cast iron increases (cast iron No. 5, table 3).

In the known cast iron (cast iron No. 9,10, table No. 2) without the addition of La, Ca, Al, the shrinkage increases sharply (cast iron No. 9, 10, table No. 3).

The rear wheel hubs cast in the foundry with the proposed chemical composition (cast iron No. 2-4, Table 3) had no shrinkage defects. Hubs previously cast from famous cast iron (cast iron No. 9-10, Table 3) after machining in the machine shop had shrinkage defects on the working part of the part and were rejected.

The effect of reducing the shrinkage of ductile iron (cast iron No. 2-4, table No. 3) and the exclusion of shrinkage defects on castings is obtained only with the combined introduction of lanthanum, calcium, aluminum and other elements within the specified limits (cast iron 2-4, table 2). A separate input of these elements (calcium and aluminum lanthanum, cast iron No. 6, 7, 8, Table 2) did not reduce shrinkage (cast iron 6, 7, 8, Table 3).

Bibliography

1. "Guide to iron casting" edited by N. G. Girshovich, L., Engineering, 1978, pp. 670-672.

2. IV Gavrilin "Pre-expansion as a result of internal pressure in metals and alloys", g. “Metallurgy of mechanical engineering”, No. 6 (9). 2002.

Claims (1)

Cast iron containing carbon, silicon, manganese, chromium, magnesium, sulfur, phosphorus and iron, characterized in that it additionally contains lanthanum, calcium and aluminum in the following ratio, wt.%:
Carbon 3.85-4.05 Silicon 1.95-2.2 Manganese Up to 0.5 Chromium Up to 0.1 Magnesium 0.03-0.06 Lanthanum 0.001-0.01 Calcium 0.002-0.007 Aluminum 0.003-0.01 Sulfur Up to 0.022 Phosphorus Up to 0.1 Iron Rest