SU1439147A1 - Wear-resistant cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the manufacture of impellers, etc. The purpose of the invention is to increase the hardness in the temperature range of 600-900 ° C and wear resistance in the heat-treated condition. The proposed cast iron contains, wt%: C 2, -2-3,2; Si 0.1-1.0; Mp 0.4-1.5; - C 12-14; Ni 0.3-1.5; V 0.5-3.5; Si 0.5-1.2; La 0.005-0.01; Ti 0.001-0.003; Mg 0.01-0.03; Na 0.001-0.003 and Fe else. The addition of La, T1, Mg, and Na to the cast iron provides an increase in hardness in the range of 600–900 ° C by 10–15% and wear resistance by 2.6–4.8 times. 2 tab. F

Description

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The invention relates to metallurgy, in particular to the development of cast iron compositions for the manufacture of impellers, etc.

The purpose of the invention is to increase the hardness in the range of 600-900 s and wear resistance in the heat-treated state. .

The choice of boundaries for the content of components is determined by the following.

The carbon content (2.2 wt.%) And silicon (0.1 wt.%) Less than their lower limit significantly increases the impact strength and decreases the hardness — not only in the molten state, but also after heat treatment, which adversely affects wear resistance.

The content of these elements (each separately), exceeding the upper limit (3.3 and 1.0 wt.%), Sharply reduces wear resistance due to the formation of brittle, complex, large eutectic carbides in the cast iron structure. At the same time, the impact strength decreases.

Manganese increases the residual austenite content in the cast iron structure, which increases crack resistance in the process of working parts. The manganese content in cast iron of 1.5 wt.% Contributes to the appearance of stable austenite in the structure, which reduces wear resistance. When the content of manganese is less than 0.4 wt.% In the structure of cast iron, a decrease in the proportion of austenitic component is observed and the proportion of martensitic component increases, which reduces wear resistance and increases brittleness.

The introduction of chromium in the range of 12–24 wt.% At the indicated carbon limit ensures the formation of type carbides. If the ratios are up or down, they can lead to the formation of carbides of the type Me.jCj or type. This leads to a decrease in the values of the specific energy of destruction of the carbide phase and a decrease in microhardness, which directly reduces wear resistance.

When the chromium content is less than 12 wt.%, The formation of complex carbides of the type with low microhardness, and consequently, low total hardness, is

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It has a detrimental effect on reducing wear resistance. With an increase in the chromium content above the upper limit (24 wt.%), The cast iron salinity decreases due to the appearance of large primary carbides in the structure.

Introduction of nickel and copper to cast iron allows to significantly improve the complex of strength and performance properties of the metal, to increase its crack resistance during casting and heat treatment. The content of nickel and copper below the lower limit (0.3 and 0.5 wt.%) Does not significantly affect the increase in the strength of the austenitic component and its microhardness. The nickel and copper contents above the upper limit (1.5 and 1.2 wt.%) Lead to a decrease in the martensite point and the appearance of stable austenite in the cast iron structure, which leads to an increase in toughness, a decrease in hardness and wear resistance.

Vanadium is used as a doped carbide phase element. At the indicated concentrations of carbon and chromium, the content of vanadium in cast iron is less than the lower limit (0.5 wt.%), Its effect is insignificant, and above the upper (3.5 wt.%) Leads to the formation of significant sizes of vanadium carbides in the structure, which increases the fragility of cast iron. The polyhardness of the carbide phase, when introduced into the cast iron, vanadium in the range of 0.5-3.3 wt.% Increases from 1370 to 1600 kg / kg.

Tellurium changes the morphology of the carbide phase. Introducing it into cast iron in the range of 0.001-0.003 wt.% Contributes to the relative spheroidization of eutectic and secondary carbides, which significantly reduces the cracking and, consequently, increases the impact strength and wear resistance. The tellurium content is less than 0.001 masv% and has almost no effect on the spheroidization of carbides, and above 0.003 mass%, the strength properties decrease due to the release of compounds based on it on the boundaries of the primary grains during crystallization.

To refine the melt from harmful impurities (sulfur, phosphorus and oxygen), to bind them to nonmetallic inclusions of a rounded shape and to remove them both from the liquid pig and from the granular grains, blunt, lanthanum and natrin are introduced into the cast iron. By removing the concentration of impurity elements, they increase fluid-fluidity, increase the density of the metal, and also reduce internal stresses in the cast structure.

The content of lanthanum and magnesium is less than the lower limit (0.005 and 0.01 wt.%) Insufficiently affect the sulfur content, i.e. changes in the shape, size, amount and nature of the distribution of phosphides and sulfides formed during eutectic crystallization. The addition of these elements over the upper limit (0.01 and O,.%) Leads to the appearance of a significant amount of oxides in the iron structure, which negatively affect the impact properties of the parts.

The introduction of sodium less than 0.001 wt.% Does not effectively influence the deoxidation process, and above 0.003 wt.% Leads to an increase in sodium oxides in the structure of a complex form in the form of clusters, which leads to additional sources of destruction during the work of parts.

The smelting of iron is carried out in an induction furnace with a base lining. In the molten iron at 1480-1510 C, alloying elements are introduced; nickel, ferrovanadium and copper. Before pouring, magnesium, lanthanum, sodium and tellurium are introduced into the ladle. Liquid cast iron at 1440- 1470 ° C is poured into lined chill, obtaining standard test specimens, which are then subjected to heat treatment according to the above regime.

The compositions of the known and iipe; viaraeMO-cast irons are given in Table. one; the results of tests of properties by known methods - in table. 2

Wear tests are carried out directly on parts (shot blasting impeller) under production conditions.

As follows from the table. I and 2, will add an additional input to the composition of the proposed cast iron Na, La, Te and Mg. Provides an increase in hardness in the range of 600–800 ° C by 10–15% and an increase in wear resistance by 2.6–4.8 times.

Claims (1)

Invention Formula Wear-resistant cast iron containing carbon, silicon, manganese, chromium, nickel, vanadium, copper and iron, characterized in that, in order to increase hardness in the temperature range of 600-900 C and wear resistance in the heat-treated state, it additionally contains lanthanum , tellurium, magnesium and sodium in the following ratio, wt.% 0 five Carbon Silicon Manganese Chromium Nickel Vanadium Copper Lanthanum Tellurium Magnesium Sodium Iron Rest PTS about about