SU1219665A1 - Charge for melting - Google Patents

Description

one

The invention relates to metallurgy, in particular to the search for wear-resistant cast iron, working under the conditions of the greatest impact-abrasive wear (high-speed abrasive wear).

The purpose of the invention is to increase the toughness and durability under conditions of impact abrasive wear while maintaining hardness at elevated temperatures.

Example, Smelting-iron is conducted in an acid-lined induction furnace. Alloying elements are introduced into the molten iron at 1550 ° C: nickel, copper, ferromolybdenum, ferrovanadium, aluminum and nitrogen. Before pouring, cerium, lanthanum and yttrium were introduced into the ladle. Filling into single forms was carried out at 1490-1450 ° C.

The chemical composition of the melted chuns of guns is given in table. one.

The carbon and silicon content is less than the lower limit of the lead. to an increase in viscosity and a decrease in hardness not only in the molten state, but also after heat treatment, and consequently, to a decrease in wear resistance. An increase in their content above the upper limit leads to a sharp decrease in durability due to the formation of large eutectic carbides in the cast iron structure in the form of needles and less heat resistant composite carbide.

The doping of cast iron with manganese within the specified limits contributes to the formation of the austenitic-carbide structure of cast iron in the cast state. This precludes the formation of a pearlite structural compound;

When the manganese content is less than the lower limit, the austenite formed during crystallization during the passage of the temperature of the perlite transformation partially decomposes into perlite, which leads to a heterogeneous structure and a decrease in abrasive wear resistance. When the content of manganese is greater than the upper limit, the hardness of the cast iron decreases not only in the cast state, but also after heat treatment. Although this leads to an increase in the viscosity of the iron, wear resistance, as the main parameter, is significantly reduced due to the high content of residual austenite after heat treatment.

196652

The high content of chromium in the cast iron leads, depending on the carbon content, to the formation of a large amount of heat-resistant chromium carbides with a hexagonal grid, which are highly resistant to abrasive wear. When the chromium content is less than the lower limit, carbides are formed.

10 and, which is directly related to the decrease in wear resistance and, consequently, the operational resistance of the parts used. When the chromium content is higher than 20 wt.%, The carbide-based eutectic is reduced to 1 (its hardness and heat resistance to carbide Me (Jj. At the same time, parts made of cast iron with a chromium content of more than 20 wt.%) Become more prone to cracking in the cast state.

, The addition of nickel and copper results in the austenitic-carbide structure of high-alloyed cast iron

25 as-cast. Moreover, due to the introduction of copper into the iron, the thermal conductivity sharply increases, which directly leads to a decrease in the wear of parts operating under high-speed abrasive friction. This is due to the fact that copper during solidification of the melt forms interstitial solid solutions, providing, with subsequent heat treatment, obtaining the optimal structure with high wear resistance. These elements, in quantitative terms less than the lower limit, have practically no effect on the change in the initial structure, and therefore, the properties of cast iron.

Additive above the upper limit is impractical, since nickel in the amount of more than 3.5 wt.%, Affecting the stabilization of Aus45 tait, sharply increases its residual content after heat treatment, which leads to a decrease in hardness and wear resistance. The presence of more than 3.0 wt.% Copper leads to

50 that it begins to stand out in a free state, and this reduces uniformity in hardness, thermal conductivity, and wear resistance.

The addition of titanium and aluminum leads to the deoxidation of liquid iron,

the formation of fine nitrides, improving the properties of the melt and changing the conditions of crystallization. Eventually

the properties of the cast iron are stabilized and the resistance to thermal effects is increased, and hence the wear resistance is improved.

The introduction of titanium in the amount of less than the lower limit leads to the formation of branched dendrides of primary carbides, which reduce the abrasive resistance of parts. The content of this element above the upper limit creates technological difficulties in obtaining suitable castings.

The addition of aluminum below the lower limit does not change the properties of the melt, but above the upper limit. - contaminates the metal with oxides, creating additional difficulties in obtaining castings and increasing scrap.

The complex alloying of cast iron with vanadium and molybdenum leads to an increase in strength, hardness and other mechanical properties not only at room temperature, but also at high temperatures.

The addition of these elements to a lower limit leads to a decrease in carbides in the structure. As a result, the resistance of cast iron to abrasive wear drops sharply. With the introduction of them above the upper limit (each separately), the formation of a triple eutectic (A-US-Mo C) occurs. Moreover, the content of these elements in carbides reaches more than 50%, which reduces their presence in the solid solution, and as a result, the wear resistance decreases.

The doping of chromium cast iron with nitrogen leads to the grinding of the primary grain and an increase in resistance to high temperatures. The nitrogen content less than the lower limit does not lead to a positive effect, and Bbmie - the upper one - has a negative effect on the strength properties due to the formation

in the structure of cast iron titanium nitrides of large sizes.

To change the shape of non-metallic inclusions, their distribution

complex modification with lanthanum, cerium and yttrium is used in the metal base and removal from the grain boundaries. In particular, the effect of cerium affects the removal of

melt oxygen and sulfur to a minimum content, after which their effect on the properties of the melt does not affect. Yttrium and lanthanum perform the function of neutralizing phosphorus and demodifying elements, which also affects the improvement of melt properties. The addition of these elements to less than the lower limit (each separately) is ineffective, and the upper one leads to the formation of intermetallic compounds, which, during the operation of the part, adversely affect the properties of the iron. For example, cerium intermetallides, located at the grain boundaries, lead to embrittlement of the part and, consequently, to a decrease in durability.

Tests on the shock-abrasive resistance of parts from the known and

the proposed cast iron held on shot blasting drums.

The test results are shown in Table. 2

From tab. 2, it can be seen that the cast iron of the proposed composition has a higher toughness, hardness at temperatures up to 600 ° C and durability under conditions of impact abrasive wear.

Parts from white high-chromium cast irons without heat treatment are practically not used. Research results show that full-scale products (armor plates, impeller blades, etc.) from the proposed cast iron have a significantly greater wear resistance than the known.

Lime Suggested

3.5 2.0 1.0 20 1.5 1.0 1.5 0.6 0.6

Famous 3.0 - Suggested

0.1

0.20.005O

0.20,010.2

1,00,100,3

2,50,500,2

3,51,000,4

3,01,000,04

3,51,200,

Table 1

0.4

Rest

Cast iron

Shock

viscosity

with 12 gf M / cm

Famous

1.0

Proposed

Tables;

Hardness, HRC, at a temperature, ° С

Persistence h

20 I 20OT 400 T 600

63 60 58

50

86

Claims (1)

WHITE IRON containing carbon, silicon, manganese, chromium, nickel, molybdenum, copper, titanium, cerium, vanadium and iron, characterized in that, in order to increase toughness and resistance under conditions of impact-abrasive wear while maintaining hardness at elevated temperatures , it additionally contains aluminum, lanthanum, yttrium and nitrogen in the following ratio of components, wt.% :. Carbon 2.0-3.4 Silicon 0.1-1.0 Manganese 0.5-4.0 Chromium 12.0-20.0 Nickel 0.2-3.5 Molybdenum 0.1-4.0 Copper 0.5-3.0 Titanium 0.01-0.6 Cerium 0.02-0.04 Vanadium 0.2-3.5 3 Aluminum 0.01-1.0 © Lanthanum 0.02-0.05 / l Yttrium 0.02-0.05 y) Nitrogen 0.0005-0.01 from Iron Rest m N3 SO OZ 05 SP >