SU1070196A1 - Cast iron - Google Patents

Abstract

ChU1UN containing carbon, silicon, manganese, chromium, vanadium, copper, molybdenum and iron, characterized in that, in order to increase and stabilize the hardness and wear resistance of cast iron, it contains components in the following ratio, May. %: Carbon2.8-3.4. Silicon2.2-3.2 Manganese 2.3-3.6 Chromium4.2-7.0 Vanadium 0.2-0.9 Copper 0.1-1.2 Molybdenum 0.2-2.55. Iron Ostal (L C

Description

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The invention relates to metallurgy, in particular, to the development of wear-resistant cast iron compositions for the manufacture of parts operating under conditions of wear such as micro-cutting.

Known cast iron of the following chemical composition, wt.%:

Carbon2,3-4,0

Silicon1,2-3,0

Manganese 1.5-5.0

Chrome11.5-18.0

Vanadium 0.2-2.5

IronErest

The hardness of the cast iron is in the cast state HRC 45-57, after heat treatment - HRC 60-62 CUf.

However, the cast iron has insufficient hardness in the cast state, which does not ensure its high wear resistance under the conditions of micro-cutting, therefore, to increase the hardness and wear resistance, parts from such cast iron are heat treated.

The closest to the technical essence and the achieved result to the proposed is cast iron 1 containing, wt.%:

Carbon 2.9-3.3

Silicon0.8-1.4

Manganese 0.4-0.8

Hrom12,0-15,0

Vanadium0,2-0,90

Copper. 0.3-0.5

Molybdenum1,4-1,6

IronErest

However, the S known cast iron has a HRC 60 hardness after heat treatment. In the cast state HRC 56, which also does not provide high wear resistance under MIC conditions

Raresani. The latter is especially important

in the manufacture of thin-walled items

difficult fopv1y, since the heat treatment causes their distortion and the need for subsequent machining (for example, for sealing the end of the tractor unit bearing unit |.

The purpose of the invention is to increase and stabilize the hardness and wear resistance of cast iron in a molded state.

,

This goal is achieved by the fact that cast iron containing carbon, silicon, manganese, chromium, vanadium, copper, molybdenum and iron contains components in the following ratio, wt%:

Carbon 2.8-3.40

Silicon 2.2-3.2

Manganese 2.3-3.60

Chrome 1.0-1-1.2

Vanadium 0.2-0.9

Copper4.2-7.0Molybdenum 0.2-2.55

IronErest

The content of chromium, carbon, silicon and vanadium corresponds to the following condition:

4, 0-0.2 (51 + V / 3 С - 3, 0 С g 4.0-0-, 5 (Si + V) С - 3.0

The content of manganese and copper corresponds to the following value:

2.5 Mp + 1/3 Cr 3.85

The optimum chromium content, determined by the dependence, ensures the formation of a white iron strugture with a carbide-based eutectic. Compared to cementite, these carbides are characterized by increased hardness and wear resistance, and their location in the eutectic ensures compliance with the principle of composition hardening and enhanced mechanical properties.

The chromium content, exceeding the optimum ratio, determined by dependence, causes the appearance of a significant amount of residual austenite in the structure of cast iron, which results in a decrease in its hardness and WEAR RESISTANCE. With a deficiency of chromium in the cast iron structure, a pedeburite appears, which leads to a decrease in the mechanical properties and wear resistance of the iron.

To obtain the highest possible hardness and wear resistance, the content of manganese and copper should ensure the formation in the cast iron structure of a metal matrix in the form of martensite, bainite and unstable austenite.

The lower the cooling rate of the casting, the greater the content of manganese and copper. The minimum in accordance with the known iron corresponds to thin-walled (up to 6 mm) chill castings. The maximum content of manganese and copper should be in castings poured into dry sand-clay forms, with a wall of 10 mm.

In order to increase the amount of martensite in the iron structure, increase and stabilize the hardness, molybdenum is introduced into the iron in an amount of 0.2-2.55% depending on the wall thickness of the casting. For castings produced in dry sandy-clay forms, with a wall thickness of 30-80 mm, the content of molybdenum in the cast iron should be 1.5-2.5%.

Melting of the proposed pig iron with the limiting and average contents of components and arcs with the chemical composition of the prototype and the analog was carried out.

Chemical compositions, hardness and wear resistance of the known and proposed cast iron are given in the table.

13,053,003,476,2

22,802,202,304,2

33,403,203,607.0

43,022,262,635,6

53,182,813,556,8

Izvesta3, 16 1.2 0.7 13.6 1.2 ny 6

52-55

2.18

1.4

0.4

With a wall thickness of 5 and 50 mm. The hardness and wear resistance of cast irons are determined in a cast state on samples with a wall thickness of 5 mm cast in dry sandy-clay forms. Tests for wear were carried out by friction on corundum sandpaper with grit No. 40-80 with an abrasive belt moving speed with a fixed abrasive of 5 and / min and a specific pressure of 7.0 hPa (7.0 kgf / cm). The test results showed that the proposed cast iron It has high hardness and wear resistance. In this case, the hardness values are stabilized within HRC 59-62, and the relative wear resistance is 2.80-3.48 units, which is higher than in cast irons used for similar purposes. Compared with the base object, for which white wear-resistant chromium cast iron used for the specified wear conditions in the heat-treated condition is adopted, the technical and economic efficiency of the proposed cast iron lies in the fact that the outer hardness and wear resistance are obtained without additional heat treatment and with relatively low content of alloying elements. The cast iron of the proposed composition can be used for the manufacture of sealing rings in the friction seal assemblies instead of those used for steel ShKh15 or teEMO treated white cast irons with cementitious carbides, as well as in other parts that require high hardness and wear resistance. The economic effect from the introduction of the invention is 90 thousand rubles.

Claims (4)

PIG IRON containing carbon, silicon, manganese, chromium, vanadium, copper, molybdenum and iron, characterized in that, in order to increase and stabilize the hardness and wear resistance of cast iron, it contains components in the following ratio, May.% S 2, 8-3,4 2.2- 3.2 2.3- 3.6 4.2-7.0 0.2-0.9 0.1-1.2 0.2-2.55 Else _ο <9 ω s I