SU1331903A1 - Wear-resistant iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the manufacture of iron castings by the method of continuous casting. The goal is to increase the microhardness over the cross section of continuously cast billets, wear resistance and heat resistance. Cast iron contains, in May.%: Carbon 2.5-3.5; silicon 1.2-2.6; manganese 0.3-0.8; chromium 0.2-0.7; titanium 0.15-0.5; vanadium 0.05-0.15; aluminum 0.05-0.25; copper 0.35-0.85; REM 0.02-0.08; calcium 0.03-0.07; barium carbides 0.05-0.25; tungsten 0.02-0.35; nickel 0.07-0.25; nitrogen 0,13-0,27; iron - the rest. The introduction of barium and tungsten carbides, nickel and nitrogen carbides into the cast iron ensures the wear resistance of cast iron 2.5-6 times, heat resistance 3.1-4 times and microhardness in castings with a section of 030 and 120 mm from 2680 to 3100-3860 N / x 2 tab. (L with so about oo

Description

 one

The invention relates to metallurgy, in particular, to the development of compositions of gray wear-resistant cast irons used for the manufacture of blanks by the method of continuous casting.

The purpose of the invention is to increase the microhardness over the cross section of continuously cast billets, wear resistance and heat resistance.

The choice of the boundary limits of the components is determined as follows.

The content of the main components (carbon 2.5-3.5 wt.%; Silicon 1.2-2.6 wt.% And manganese 0.3-0.8 wt.%) Is determined from the practical production of wear-resistant and heat-resistant cast iron New with a high microhardness of matrices and with a stable structure. When carbon is concentrated up to 2.5 wt.%, Silicon up to 1.2 wt.% And manganese is more than 0.8 wt.%, The amount of cementite in the structure increases, its stability and thermal stability decrease. When the carbon content is more than 3.5 wt.%, Silicon is more than 2.6 wt.% And manganese is less than 0.3 wt.%, The segregation increases, the contamination of the cast iron with non-metallic inclusions and the stability of the structure and microhardness over the cross-section of the preforms decreases.

The content of micro-alloying additives (chromium 0.2-0.7 wt.%; Titanium 0.15-0.5; copper O, 35-0.85; vanadium 0.05-0.15; REM 0.02-0, 08; aluminum (0.05–0.26 wt.%) Is determined experimentally and within limits, ensuring a homogeneous structure and optimum strength and plastic properties, stable microhardness and increased heat resistance. With a lower content, the strength and frictional properties are insufficient, and with an increase in their concentration (above the upper limits), the impact resistance, resistance, dynamic stability and stability of the structure decrease, leading to a decrease in microhardness and other properties and their stability. The upper limits of the concentration of bleaching elements (chromium, vanadium, REM) are reduced, and their graphitization is reduced.

Calcium is introduced as an effective modifier that cleans the grain boundaries from non-metallic inclusions and increases the stability of the structure and microhardness.

The upper limit of calcium concentration is limited by its solubility in

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five

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perlite, and at a concentration of 0.03 wt.% the modifying effect is insufficient.

Introduction to the known cast iron of barium carbides in the range of 0.05-0.25 wt.% Provides an increase in the dispersion of the structure, hardness inside the profiles, the degree of perliteration of the metal base of the castings, an increase in the structure uniformity, impact resistance, heat resistance, wear resistance and microhardness, which leads to increased stability mechanical properties. The content of barium carbides above the upper limit is impractical, since in this case, in connection with their low solubility, their segregation to austenite increases, which reduces the uniformity of the structure and the dynamic strength of the iron. The introduction of barium carbides into the cast iron in an amount below the lower limit does not ensure obtaining the desired advantages in terms of structure homogeneity, wear resistance and heat resistance.

The introduction of tungsten into cast iron is due to the fact that it strengthens the matrix and grinds the cast grain in the central zone of the ingots, crushes graphite, changing its shape, the structure of the metal base in the castings, increases heat resistance, stability of microhardness, dynamic strength and other physical and mechanical properties,

The introduction of tungsten in cast iron in amounts of less than 0.02 wt.% Does not significantly affect the increase in microhardness stability, heat resistance, and physicomechanical properties, and the tungsten content above 0.35 wt.% Is inexpedient, since in this case the duration significantly increases. the smelting of cast iron and the complication of the technology of after-treatment, the impact resistance and uniformity of the structure and properties are reduced.

Nitrogen in wear-resistant cast iron in an amount of 0.13-0.27% is introduced as an effective alloying component, which binds titanium, rare-earth metals, aluminum, vanadium and other elements in cast iron to disperse nitrides and carbonitrides, ensuring improved structure homogeneity, microhardness, heat resistance and thermal resistance. When the nitrogen content is less than 0.13 wt,% is not provided

a significant increase in microhardness and its stability over the cross section of continuously cast ingots, a noticeable increase in the thermal stability of cast iron. An increase in nitrogen concentration (more than 0.27 wt.%) Reduces the structure homogeneity, impact strength, and stability of mechanical structures.

Nickel in the specified range of 0.07 - 0.25 wt.% Contributes to the improvement of plastic properties, grinding and stabilization of the structure, which provides increased microhardness stability and thermal stability. When the nickel content is below 0.07 wt.%, The stability of the structure, microhardness and thermal stability is not achieved, and with an increase in its content (more than 0.25 wt.%). Shock resistance and microhardness are reduced.

The introduction of barium, tungsten, nickel and nitrogen carbides into the known cast iron ensures a more homogeneous structure in the castings, stable microhardness, a complex of new properties that combine high values of operational properties, and dynamic

durability, wear resistance and heat resistance, wear resistance and heat resistance.

Cast iron melted in induction furnaces. Ferroalloys are used to micro-alloy cast iron. Modification of RGM cast iron, barium carbides and aluminum is carried out in casting ladles with the cast iron being released from the furnace after purging with nitrogen.

The temperature of the metal prior to release from the electric furnace for modifying into a 2 t bucket is 1480-1500 ° C, and the temperature of the pig iron when pouring the melt into the mold of the continuous casting machine is 1410-1430 ° C.

On UNGL-2 installations, round billets 030 and 120 mm are pulled.

The mechanical properties and heat resistance of cast irons are determined on specimens cut from 30 mm profiles. Microhardness of metal base op- g

40

45

bone, it additionally contains carbides barium, tungsten, nickel and nitrogen in the following ratio, wt.%:

Carbon

Silicon

Manganese

Chromium

Vanadium

Titanium

Aluminum

Rare earth

items

Calcium

Copper

Barium carbide

Tungsten

Nickel

2.5-3.5

1.2-2.6

0.3-0.8

0.2-0.7

0.05-0.15

0.15-0.5

0.05-0.25

Nitrogen Iron

0.02-0.08 0.03-0.07 0.35-0.85 0.05-0.25 0.02-0.35 0.07-0.25 0.13-0.27 Else

They are determined on a PMT-3 microhardness meter on samples taken from blanks of 30 and 120 mm.

The chemical composition of the cast iron is given in table. one; mechanical properties, microhardness and heat resistance - in the table. 2

The waste of rare-earth metals is 26-32%, barium carbides 12-16%. The assimilation of tungsten from ferro-tungsten, set in the furnace, 100%, nickel 89-93%.

As can be seen from the table. 1 and 2, the additional input of barium, tungsten, nickel and nitrogen carbides into the composition of the cast iron ensures microhardness over the cross section of continuously cast billets, wear resistance 2.5-6 times and heat resistance 3.1-4.0 times.

Claims (1)

Invention Formula Wear-resistant cast iron containing carbon, silicon, manganese, chromium, vanadium, titanium, aluminum, rare earth elements, calcium, copper and iron, characterized in that, in order to increase the microhardness over the cross section of continuously cast, 5 0 products, wear resistance and heat 0 five bone, it additionally contains barium carbides, tungsten, nickel and nitrogen in the following ratio, wt.%: Carbon Silicon Manganese Chromium Vanadium Titanium Aluminum Rare earth items Calcium Copper Barium carbide Tungsten Nickel 2.5-3.5 1.2-2.6 0.3-0.8 0.2-0.7 0.05-0.15 0.15-0.5 0.05-0.25 Nitrogen Iron 0.02-0.08 0.03-0.07 0.35-0.85 0.05-0.25 0.02-0.35 0.07-0.25 0.13-0.27 Else IfeKpoTBepfloCTb, H in the center of the profile # 30 mm 2680 3280 Table 1 3360 3460 3070 2710 The continuation of the table.2 Properties Indicators for the composition of cast iron l ZLll lIIZI ZL Z in the surface area profile 9 30 mm 3710 3820 3840 3860 3620 5140 in the center of the profile is 120 mm 2430 3100 3140 3280 2890 2450 in the surface area profile "120mm 3580 3680 3700 3790 3140 3570 Thermal stability when heated to lOOO C, cycles543. 1718 1830 2160 1212 590 Impact resistance Daklov 887 1192 1236 1268 1164 .920