SU1752819A1 - Antifriction cast iron - Google Patents

Abstract

Summary of the Invention 1 for parts operating under friction conditions under heavy loads, Antifriction cast iron with lower values of the coefficient of friction and hardness while maintaining high wear resistance contains aluminum and calcium in the following ratio of components, wt.%: C 2.8-4.2 , Si 3.6-5.8; MP 0.3-0.8, Cg 0.05-0.3; Mo 005-0.2; Si 0.6-1.8; AI 005 0.07; MD 0.01-0.05; Ca 0.005-0.02, RZM0.01-0.08; Fe the rest In the cast state, with a hardness of HB 223-255, it has a low coefficient of friction (without lubricant f 0.46-0.50) and high wear resistance (not lower than that of a known alloy) Table 2.

Description

The invention relates to metallurgy, in particular to nodular cast irons used in friction units.

Known cast iron, wt.%: Carbon 3-4

Silicon3,5-5

Manganese 0.5

Chrome 0.05-0.2

Vanadium 0.1-0.5

Magnesium 0.02-0.06

IronErest

This cast iron has high wear resistance and scaling resistance.

The disadvantages of cast iron are a tendency to ferritic fragility and a relatively high coefficient of friction.

The closest to the offer is cast iron containing, in wt.%: Carbon 3-3.8

Silicon2-3.5

Manganese 0.2-1.5

Chrome 0.03-0.3

Molybdenum 0.03-0.5

Vanadium 0.03-0.5

Nickel

Copper

Tin

Antimony

Magnesium

Rare earth metal

Iron

0.1-2.5 0.1-0.5 To 0 15 To 0 03 To 0.1 To 0.1 Else

Ca

WITH

Due to molybdenum, the tendency of iron to ferritic fragility is reduced. Cast iron has high strength and wear resistance,

The disadvantages of cast iron are a relatively high coefficient of friction, the possibility of forming a needle-like structure with a deterioration in workability by cutting, instability of the structure and properties of castings in a non-heat-treated condition.

The aim of the invention is to reduce the coefficient of friction and the hardness of cast iron in a cast state while maintaining high wear resistance.

This goal is achieved in that the iron containing carbon, silicon, martian, chromium, molybdenum, copper, magnesium, rare-earth metals and iron, additionally contains aluminum and calcium in the following ratio, wt.%:

Carbon2,8-4,2

Silicon3.6-5.0

Manganese 0.3-0.8

Chrome 0.05-0.3

Molybdenum0.05-0.2

Copper 0.6-1.8

Aluminum0.05-0.7

Magnesium0.01-0.05

Calcium 0.005-0, t) 2

- РЗМ0,01-0,07

IronErest

moreover, the contents of the components must comply with the following conditions, wt.%: 4 GN 81 + L 4.28-5.99;

P2 Mp + Cr + Cu 1.45-2.31; Pz MD + Ca + RZM 0.070 - 0.106, P1 - P2 2.59.

Sulfur (up to 0.03 wt.%) And phosphorus (up to wt.%) May be present as impurities in the iron.

The composition of cast iron is selected based on the following considerations.

Compared to the prototype, the silicon content is increased, which is explained by the fact that silicon must provide hetero-fermentation of ferrite (i.e., separation of ferrite into two phases - carbonaceous and siliceous ferrite). In turn, heterogeneous ferrite provides a low coefficient of friction and high adhesive wear resistance. With a silicon content of less than 3.6 wt.%, This effect is negligible. If the silicon content exceeds 5.8 msec.%, Then an increased amount of silicoferrite leads to embrittlement of the iron, increasing its hardness and reducing wear resistance.

Aluminum in cast iron provides two effects: together with silicocalcium, it has a modifying effect, grinding the structure and eliminating chill, together with silicon contributes to the formation of the structure of heterogeneous ferrite. Both of these effects lead to a decrease in the friction coefficient and stabilize the hardness of the iron. When the aluminum content is less than 0.05 May. % None of these effects are noticeable. Too much aluminum (more than 0.7% by weight) dramatically impairs the casting properties of the alloy.

The total content of silicon and aluminum, determined by the value of the parameter GI, should be in the range of 4.28-5.99%. If Hi is 4.28%, then

heterogenization of ferrite and low coefficient of friction. With P 5.99%, the hardness of the iron increases and its antifriction properties decrease.

Manganese, chromium, and copper belong to the perlitisation elements. The presence of separate isolated areas of perlite in the ferrite structure of cast iron corresponds to the Charpy principle and improves antifriction properties. The total content of the perlint elements of the stresses, expressed by the parameter P, with values less than 1.45% is not enough to form such a structure. When Pa is 2.31%, the amount of perlite increases, the principle of Charpy is violated and the cast iron deteriorates. The difference between the contents of the elements of ferritisers and gerlitisers (i.e., Hi-Pz) must be at least 2.59%. AT

Otherwise, the formation of pearlite mesh and reduced anti-friction properties,

The manganese content is recommended in the range of 0.3-0.8 May%. The lower limit corresponds to the content of manganese as a technical impurity. With a content of more than 0.8 wt.% (Taking into account the copper and chromium contents), manganese contributes to the formation of pearlite grid, which negatively affects the properties cast iron.

Chromium is introduced in the amount of 0 05–0.3 wt.% With the stabilization of eutectoid cementite in isolated pearlite sites. At the lower level it is

With a technical impurity, with a content of more than 0.3% by weight of chromium, secondary carbides can be released along the boundaries of ferrite i-s grains with embrittlement of cast iron and a decrease in its properties

Copper is reduced to form in

the structure of cast iron in isolated areas of perlite with the inclusion of the copper phase, which significantly reduces the coefficient of friction and increases the wear resistance of cast iron.

a copper content of less than 0–6 May.% only the first effect appears weakly, which slightly affects the properties of cast iron. In the amount of more than 1 8 May% copper almost does not lead to further improvement of the properties of cast iron, but it significantly increases its cost.

Molybdenum in cast iron is used to eliminate or reduce ferritic brittle ™. With a content of less than 0 02 May% of molybdenum, this role is practically not manifested, and with a content of more than 0 2 msec.%, The iron becomes significantly more expensive, its hardenability increases and its hardness increases.

The carbon content provides the necessary structure and properties of cast iron in the cast state. When the carbon content is less than 2.8 wt.%, The degree of ferritization of the structure decreases, it becomes possible to form a pearlite mesh with an increase in the coefficient of friction. If the pig iron contains more than 4.2 wt.% Carbon, its structure becomes hypereutectic, which leads to an increase in the amount of graphite and adverse segregation phenomena, manifested in a decrease in strength and wear resistance.

The parameter Pz, which characterizes the total content in the cast iron of the elements of the complex modifier, must be at least 0.070%. Otherwise, the degree of spheroidization of graphite turns out to be insufficient. At Pz 0.106%, the increased consumption of the modifier increases the cost of the cast iron and does not lead to an increase in its properties, on the contrary, it is even possible to remodify the cast iron.

Magnesium content is recommended in the range of 0.01-0.05% May. If the residual magnesium content is less than 0.01 wt.%, Then the results of the modification are unstable. An increase in the magnesium content of more than 0.05 wt.% Is not advisable, since it improves the properties of the cast iron.

Calcium plays the role of desulphurizer and deoxidizing agent, significantly reducing the consumption of magnesium and rare-earth metals. In optimal amounts, calcium contributes to graphitization of pig iron and thereby reduces the coefficient of friction. Calcium content less than 0.005 wt.% Corresponds to non-modified calcium iron. Calcium consumption is too high, corresponding to a residual content of more than 0.02 wt.%, Increases the amount of nonmetallic inclusions, impairs modifier absorption, and reduces the properties of iron.

REMs are introduced in order to neutralize elements that have a desfer- oidizing effect on graphite (aluminum, copper). At a content of less than 0.01 wt.% REM, the complete spheroidization of graphite is not provided. The increase in the content of rare-earth metals (more than 007 wt.%) Is impractical because it does not have a positive effect, but it increases the cost of cast iron.

The iron smelting is carried out in open induction crucible furnaces with an acidic lining on the charge consisting of carbon steel waste, electrode bo, ferroalloys (ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum), waste copper and aluminum. Ferroalloys are introduced into the melt at 13501380 ° С. After melting the ferroalloys, copper and aluminum are introduced. Aluminum is partially used in the composition of the complex modifier

When the metal is poured from the furnace into the casting ladle, the complex modification of cast iron is carried out using a sandwich process by loading the modifying mixture with a specially cast iron grid. The temperature of the modified metal is 1420-1450 ° C.

Liquid iron is poured into dry sandy-clay forms. Standard 30 mm thick cast molds from which samples are cut for metallographic analysis, mechanical testing and wear testing. The wear tests were carried out on the MI-1M machine under dry troni conditions according to a rotating disk-stationary block. The counterbody's disc with a diameter of 50 mm was made of steel 45 and heat-treated on HNSE 46. The tests were carried out at a disc rotation speed of 250 rpm with a specific load of 3 MPa. Wear is determined by the weight loss of the sample during wear. In parallel, the coefficient of friction is determined

The chemical compositions of the alloys and the results of their tests are given in Table. 1 and 2.

The cast iron of the proposed composition (alloys 1-5) differs from the prototype by a combination of higher and more stable properties. When the content of the components in the iron is exceeded (alloys 6-8), its properties are significantly impaired (reduced wear resistance, coefficient of friction increases).

Claims (1)

Claims of the invention Antifriction cast iron containing carbon, silicon, manganese, chromium, molybdenum, copper, magnesium, rare earth metals and iron, characterized in that in order to reduce the coefficient of friction and hardness while maintaining high wear resistance in the cast state, it additionally contains aluminum and calcium in the following ratio, wt.%: Carbon2,8-4,2 Silicon3,6-5,8 Manganese 0.3-0.8 Chrome 0.05-0.3 Molybdenum0.05-0.2 Copper 0.6-1.8 Calcium0.005-0.02 Magnesium0.01-0.05 Aluminum0.05-0.7 Rare earth metals 0,01-0,07 IronErest moreover, the parameter of the content of components satisfy the following ratios, wt.%: Hi-SH AI-4.28 5.99, P2 Mp I Cr + Cu - 1.45 2.31; Pz - Mg f Ca i RZM - 0.070 0 106 P1-P2 2.59  Also contains 0.47% V, 1.84% N1 and 0 01% Sb Editor N. Gumko Tehred M.Mbrgental Order 2736 Circulation: Subscription VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moskvl, Zh-35, Raushsk nab. 4/5 Table 1 table 2 Proofreader M. Keretsman