SU1574669A1 - Cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of iron castings. The purpose of the invention is to increase the generation of cracks and reduce impact-erosive wear. New cast iron contains, wt%: C 2.6 - 3.2

SI 0.8 - 1.4

MN 0.4 - 1.2

CR 10 - 15

N 0.01 - 0.02

V 0.4 - 0.8

REM 0.013 - 0.055

NI 0.4 - 1.0

TI 0.05 - 0.1 and FE the rest. Additional input to the composition of the proposed cast iron TI and NI made it possible to increase the work of crack initiation by 1.3–2.08 times and reduce impact-erosion wear by 1.25–2.08 times. 1 tab.

Description

The invention relates to metallurgy, in particular, to the composition of cast iron for castings operating under conditions of increased impact loads and impact erosion wear.

The purpose of the invention is to improve the operation of air; Reduction of cracks under impact loading and reduction of impact erosion wear.

The choice of the boundary limits for the content of components in the iron of the proposed composition is due to the following.

The lower limits of carbon and silicon (2.6 and 0.8 wt.%) Are selected on the basis of the processability of the alloy — ensuring sufficient fluidity (as a rule, the alloy is used to manufacture a thin-walled cast — shot blast blades, impeller, etc., whose wall thickness is not exceeds 5-10 mm

and therefore ensuring good fluidity is an important factor in obtaining high-quality casting). The upper limits (3.2 and 1.4 wt.%), Respectively, are selected based on the required durability and wear resistance due to the formation, when the upper limit is reached, of fragile complex eutectic carbides and less heat-resistant MeES type carbide. Manganese is a carbide stabilizing element, reinforcing alloy. At the same time, it does not form its own carbides, and therefore the manganese content is limited to 0.4-1.2 wt.%. When the manganese content is below the lower limit, the austenite formed during crystallization in the case of rapid cooling, which occurs in the manufacture of thin-walled castings,

sl j

Ј

oh

&

partially decomposed into perlite and martensite. The presence of perlite in the cast iron structure leads to a sharp increase in the rate of impact-erosive wear of parts. The addition of manganese above the upper limit does not lead to a significant hardening of the alloy.

The chromium content in the range of 10–15 wt.% Provides the alloy crystallization according to a metastable diagram. Chromium and vanadium are strong carbide stabilizing elements. Moreover, their own carbides have significantly greater microhardness than iron carbides, and have a significant effect on the hardness and wear resistance of cast irons. The lower limit on the chromium content (10 wt.%) Garan 46694

the hardness of cast iron and especially wear resistance under the conditions of impact-erosion. The lower limit of its content of 0.01 wt.% Provides a sufficient amount of nitrides and carbonitrides to increase wear. alloy resistance. The upper limit (0.02 wt.%) Is set on the basis of the limited solubility of nitrogen in liquid iron-carbon alloys.

The use of rare earth elements Ce, La, Nd, Pr and Sm is based on their refining action. Binding 04, S and P in non-metallic inclusions, change the topography of the location of non-metallic inclusions, push them out from the grain boundaries and transfer the latter directly into the grain. With

ten

five

tirovaet required microstructure of the alloy. this clears the grain boundaries, meaning /

va (sufficient amount and distribution of carbides, to ensure wear resistance). Above the upper limit (15 wt.%), The form deteriorates and carbides become larger, which leads to a decrease in resistance to impact-erosion wear.

Vanadium in the composition of cast iron in quantities of 0.4-0.8 wt.% Contributes to the formation of carbides and carbonitrides, which are uniformly located in the metal matrix of the alloy. Vanadium carbides and carbonitrides are characterized by high dispersion (5-10 µm) and microhardness (NQV. 9000 - 10000 MPa), which contributes to the increase of the wear resistance of the alloy.

Nickel is a strong reinforcing element. The lower limit of 0.4 wt.% Provides sufficient hardening of the metal matrix. With an upper limit of 1.0 wt.%, In combination with the total content of vanadium, titanium, manganese and chromium, the maximum strengthening effect is achieved - the generation of cracks increases.

Titanium - a refining element, bonding Ot, S and P to non-metallic inclusions, contributes in part to their removal from the melt. The lower limit of 0.05% by weight of titanium is set by a sufficient refining effect, the upper limit is 0.1% by weight due to the stabilization of the refining effect.

Nitrogen is an element that forms strong compounds with titanium, vanadium, such as nitrides and carbonitrides, being evenly distributed in the matrix, they increase the overall

25

thirty

35

40

45

50

55

The strength of molecular-mechanical bonding increases, which is important, since non-metallic inclusions, located on the grain boundaries, inhibit the movement of dislocations during plastic deformation of the metal, causing its destruction. The work of cracking under shock loading increases. The lower limit of Ce, La, Nd, Pr, and Sin (0.005; 0.001; 0.001; 0.005; 0.001 wt.%) Is due to their low efficiency. The upper limit (0.02; 0.01; 0.01; 0.01; 0.005 wt.%), Respectively, is due to the increase in the degree of supercooling and the danger of their bleaching effect on the cast iron. The effect of these elements is especially effective when they are introduced together, grain-bound segregation of phosphorus is eliminated, and silicon micro-quenching is reduced, which has a positive effect on cracking generation rates.

The cast iron was melted in a 50 kg induction crucible furnace with an acid crucible lining. After overheating of the melt to 1450 ° C, the alloy was refined using basic and alloying elements. As ferroalloys and special additives used: nitrided ferrochrome PF 400N, GOST 4757-67, (Cr-68%, N-5%); ferromanganese FMP 0.5, GOST 4755-70, (Mn-35%); ferro-titanium Ti1, GOST 4761-67, (Ti 30%); ferrovanadium Vd1, GOST 4760-69, (V - 40%); electrolytic nickel, cerium mischmetall MTs-40, TTsTU-05- -20-67, (Ce 36%). The assimilation of elements.

This clears the grain boundaries, which

The strength of molecular-mechanical bonding increases, which is important, since non-metallic inclusions, located on the grain boundaries, inhibit the movement of dislocations during plastic deformation of the metal, causing its destruction. The work of cracking under shock loading increases. The lower limit of Ce, La, Nd, Pr, and Sin (0.005; 0.001; 0.001; 0.005; 0.001 wt.%) Is due to their low efficiency. The upper limit (0.02; 0.01; 0.01; 0.01; 0.005 wt.%), Respectively, is due to the increase in the degree of supercooling and the danger of their bleaching effect on the cast iron. The effect of these elements is especially effective when they are introduced together, grain-bound segregation of phosphorus is eliminated, and silicon micro-quenching is reduced, which has a positive effect on cracking generation rates.

The cast iron was melted in a 50 kg induction crucible furnace with an acid crucible lining. After overheating of the melt to 1450 ° C, the alloy was refined using basic and alloying elements. As ferroalloys and special additives used: nitrided ferrochrome PF 400N, GOST 4757-67, (Cr-68%, N-5%); ferromanganese FMP 0.5, GOST 4755-70, (Mn-35%); ferro - titanium Ti1, GOST 4761-67, (Ti 30%); ferrovanadium Vd1, GOST 4760-69, (V - 40%); electrolytic nickel, cerium mischmetall MTs-40, TTsTU-05- -20-67, (Ce 36%). The assimilation of elements.

from ferroalloys,%: Cg 70-85; N 65 75; Mp 85-90; V 70; Ti 60-70. Ni absorption is 85-90%, Ce, La, Nd, Pr and Sin - 70-90%. The achievement of equal concentrations of neodymium, lanthanum and praseodymium was carried out by introducing into the cast iron the pure elements of neodymium, lanthanum and praseodymium.

Samples for the manufacture of samples for mechanical tests were cast in a dry sand mold (type II according to GOST 7293-79). Then, standard specimens with a 10x10x55 mm section were cut out without an incision for impact testing. Percussion tests were carried out according to GOST 9454-78 on a rotating scraper of the RSO type with oscillography of the destruction process, which allows using the impact fracture diagrams to evaluate the generation of cracks. ,

Impact erosion wear was investigated on impact erosion installation at a counter-jet velocity of 70 m / s with a sample with a diameter of 8 mm with a tap water pressure of 0.2 MPa.

Impact erosion wear was assessed by weight loss of the test samples.

The chemical composition of the pig iron, the performance of the nucleus

No cracks and impact erosion wear are presented in the table.

As follows from the table, the additional input to the composition of the proposed cast iron Ti and Ni makes it possible, compared with the known cast iron, to increase the work of crack initiation by 1.3–2.08 times and reduce the impact-erosion wear by 1.25–2.08. times.

Claims (1)

Invention Formula Cast iron containing carbon, silica, manganese, chromium, nitrogen, vanadium, rare earth metals and iron, characterized in that, in order to increase the generation of cracks and reduce impact-erosion, it also contains nickel and titanium in the following ratio, wt.%: 25 thirty L. Chcholinsk. Compiled by I.Kostornaya Tehred L. Serdyukova Proofreader V. Kabatsy Order 1759 Circulation 484 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Production and publishing plant Patent, Uzhgorod, st. Gagarin, 101 Table continuation Subscription