SU1328400A1 - Cast iron - Google Patents

Abstract

The invention relates to the field of foundry, in particular, to compositions of high-strength cast irons, and can be used in the manufacture of critical castings operating under conditions of high impact loads. As the initial melt for the production of high-strength cast iron, cupola cast iron is used. The aim of the invention is to increase the dynamic strength and crack generation work. The proposed cast iron contains components in the following ratio, May. %: carbon 3.2 - 3.7; silicon is 2.8-3.3; manganese 0.2 - 0.8; chromium 0.05-0.2; titanium 0.01-0.05 cerium 0.005-0.02; magnesium 0.04-0.07; aluminum 0.001-0.01; copper 0.05-0.2; nickel 0.05-0.4; lanthanum 0.004-0.01; neodymium 0.001-0.01; Praseodymium 0.001-0.01; barium 0.01-0.03; iron else. The advantage of cast iron of the proposed composition is the presence of a complex of elements: barium, neodymium, lanthanum and praseodymium, which, together with the ferritizing effect (barium), ensure the purity of the alloy at the grain boundaries, thereby preventing embrittlement under shock loads. The proposed solution can be adopted in the production of castings from high-strength cast iron with increased dynamic fracture toughness, as applied to parts of the DT-75 tractor family (rear support, shoe). with SL

Description

The invention relates to foundry, in particular, to high-strength cast iron compositions, and can be used to make high-quality castings obtained by spheroidizing modification of the crucible melt cast iron melt and intended for working under dynamic load conditions. The purpose of the invention is to increase the dynamic strength and the work of cracking under the shock loading of cast iron,

The proposed cast iron contains components in the following ratio, masD Carbon 3.2-3.7

Silicon2.8-3.3

Manganese 0.2-0.8

Chrome 0.05-0.2

Titan0,01-0,05

Cerium0.05.05-0.02

Barium0.01-0.03

Magnesium 0.04-0.07

Aluminum 0.001-0.01 Copper0.05-0.2

Nickel0.05-0-, 4

Lanthanum 0.004-0.01

Neodymium 0.001-0.01

Praseodymium 0,001-0,01 IronEstal

Impurities, May. %: sulfur up to 0.03,. phosphorus to 0.05.

Entering barium cast iron into the composition ensures the crystallization of the alloy according to a stable diagram, preventing the formation of structurally free carbides and contributes to an increase in the ferrite component in the iron structure, thereby increasing its viscosity properties. The lower limit of the barium content (0.01%) is due to the production of at least 40% ferrite, the upper (0.03%) is limited by complete ferritization of the metal base with the content of stabilizing elements (Mn, Cr, Cu) at the lower level, and silicon at the upper level. The dynamic strength of the cast iron in this case is reduced.

It should also be noted the high refining ability of barium, especially in relation to cast iron cupola melt containing an increased amount of impurities (S to 0.1%, P to 0.05%) and gases.

Binding impurities and gases to stable chemical compounds, barium promotes their partial removal from the melt, while grain boundaries are cleaned, which is important because nonmetallic inclusions, located along grain boundaries, inhibit the movement of dislocations during plastic deformation of the metal, causing its destruction.

The use of the rare-earth elements Nd, La and Pg is also based on their

refining action and is particularly effective for cupola iron smelting. At the same time, Nd, La, and Pr, in contrast to Ba, transfer S and other impurities from the regions located along the boundaries

Grains, directly inside the grain, in the crystallization process create additional graphitization centers. In addition, Nd, La and Pr as well as Ce, contribute to the spherolitic crystallization of graphite, increasing the time of the spheroidizing modification, which is very important for the current production. The lower limit for La, Nd and Pr (0.004, 0.001,

0.001%), respectively, due to the low efficiency of their action. The upper limit (0.01, 0.01, 0.01%), respectively, is due to the increase in the degree of supercooling, and the danger

their whitening effect on cast iron. The action of these elements is especially effective when they are introduced together, grain-restricted segregation of phosphorus is eliminated, and silicon microloquation in the HSGH is reduced, which has a positive effect on the dynamic strength and crack generation performance.

Example. Smelting alloys

The proposed composition is carried out by a duplex process: an acid-lined Vagrande - an induction crucible mixer.

.With quality materials

cast iron, steel waste, return of own production, ferroalloys and special additives are used. Obtaining the required concentration of carbon in cast iron is achieved by varying the composition of the metal mill. The adjustment of the content of silicon, manganese, chromium, titanium is carried out by addition to the filling of ferrosilicon FS, ferromanganese

FMN75, ferrochrome FH650, ferrotite-Ti1.

Alloying additives sit down after finishing the alloy in chemical

3

composition directly in an induction crucible mixer.

Barium, lanthanum, neodymium, and praseodymium are introduced into the ladle before the metal is released from the furnace for subsequent spheroidizing treatment, in the form of -Si Ba (15%) and mischmetal МЦ-40. The absorption of Si Ba is 60%, of rare-earth metals of the cerium group from Mishmetal MC-40 70-90%. The spheroidizing treatment is carried out at 1420 ° C with an LCS-2 ligature in the reaction chamber of a mold.

Samples for the preparation of samples for mechanical tests were cast in wet sand mold (type II). Then, standard 10 x 10 x 55 mm cross-sectional samples were cut out without an incision for impact bend tests. Impact tests are carried out on a rotary scraper of the RSO type with oscillography of the destruction process, which allows using the fracture diagrams to evaluate the workings of cracks and the dynamic strength of the alloys under study.

According to this technology, five compositions of the proposed alloy (on the lower, middle, upper, as well as lower than the lower and higher upper limits of the content of ingredients) and the known alloy are melted.

The proposed composition of cast iron has a higher dynamic strength and work of cracking in comparison with the known alloy.

The optimal composition of cast iron, wt.%;

Carbon3,45

Silicon3.05

Manganese 0.5

Chromium 0.13

Titanium0.03

Cerium 0,012

Magnesium0,055

Aluminum 0.005

Copper 0.12

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VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

1328400

Nickel

Lanthanum

Neodymium

Praseodymium

Barium

Iron

Impurities, May. %;

Sulfur

Phosphorus

0.22

0,007

0,005

0,005

0.02

Rest

Up to 0.03 To 0.05

The proposed cast iron can be used in the production of critical castings from high-strength cast iron, operating under dynamic load conditions as applied to parts of the DT-75 tractor family (rear support, shoe, etc.).

Claims (1)

Invention Formula Cast iron containing carbon, silicon, manganese, chromium, titanium, cerium, magnesium, aluminum, copper, nickel, barium, neodymium, lanthanum, praseodymium and iron, characterized in that, in order to increase the dynamic strength and the generation of cracks during impact cast iron loading, it contains components in the following ratio, May. %: five 0 five Carbon Silicon Manganese Chrome Titanium Cerium Magnesium Aluminum Copper Nickel Barium Neodymium. Lanthanum Praseodymium Iron 3.2-3.7 2.8-3.3 0.2-0.8 0.05-0.2 0.01-0.05 0.005-0.02 0.04-0.07 0.001-0 , 01 0.05-0.2 0.05-0.4 0.01-0.03 0.001-0.01 0.001-0.01 0.004-0.01 Else