SU1439148A1 - Cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of castings operating under conditions of high temperatures in a gas atmosphere. The purpose of the invention is to increase the scaling resistance and growth stability when heated to 700-950 ° C and for a long time. New cast iron contains components in the following ratio, wt.%: C 3.2-3.6; Si 2.3-3.0; Mp 0.1-0.4; Mo 0.1-0.35; Rb 0.05-0.1; Ni 1-2,0; Ca 0.001-0.02; A1 0.5-0.9; Hf 0.06-0.38 and Fe else. Additional input to the composition of cast iron A1 and Hf will increase the oxidation resistance of 1.5-3.8 times and the resistance to 1.4-4.2 times. 2 table.3

Description

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The invention relates to metallic iron, in particular, to the development of cast iron compositions for castings, operating in conditions of prolonged heating to temperatures of 950 ° C in a gas atmosphere. The purpose of the invention is to improve the quality of the glazing-resistant and high durability when heated to temperatures of 700-950 ° C and prolonged extrusion.

The choice of boundaries for the content of components in the cast iron of the proposed composition is determined by the following.

The carbon content i of silicon is chosen on the basis of the required graphitization of the alloy. The lower limits for carbon (3.2 wt.%) And silica (2.3 wt.%) Are set to chill in castings. The carbon carbon concentrations (up to 3.6 wt.%) and silicon (up to 3.0 wt.%) contribute to the crystallization of the melt according to a stable diagram without structurally free carbides. Increasing silicon (over 3.0 May,%) reduces the ductility cast iron due to the latter alloying of ferrite, which, when operating castings under shock loads (for example, grates), leads to their breakdown. The addition of carbon over 3.6 wt.% leads to flotation of graphite and creating loose inside the castings, which oxidation is oxidation me gall.

Molybdenum compounds modify the oxide film on the surface of the cast iron, reinforcing it. In ripoi, the ecce of passivation of the molybdenum compound is embedded in the passive film and adsorbed on the walls of corrosive ulcers. brake z-ix growth. The lower limit of the molybdenum content (0.1 wt.%) Does not have a significant effect on the gas-correction rate. The addition of molybdenum in excess of 0.35 wt.% Leads to the formation of carbides and the consolidation of the matrix, which adversely affects the process of hardening by the oxide film.

The presence of nickel in the range of 1.0-2.0 wt.% Together with manganese (0, -0.4 wt.%) And molybdenum. Allows to obtain a solid solution of the -phase with a relatively small number of fine dispersed carbides of complex composition. located inside

ri eutectic grains; which, with prolonged supernatures in the temperature range 650–950 ° C, dissolve in the matrix and additionally jr c ijpyio:.

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The optimum ratio of manganese and nickel in the alloy is A: 1 n: 3, 5.

Calcium, which has a great agent for sulfur, hydrogen chloride, hydrogen, nitrogen and phosphorus, prevents the interaction of aluminum with dashtsy elements and the formation of non-metallic inclusions at the grain boundaries during solidification of the alloy. The addition of calcium in the amount of 0.001-0.02 wt.% Is sufficient to significantly reduce the concentration of sulphides, oxides, hydrates and nitrides in the solid solution 06 phase.

Calcium input more than 0.02 wt.% Is not economically feasible.

Aluminum reduces the formation of cementite in the alloy structure. The concentration of aluminum less than 0.5 wt.% Does not provide an increase in the scaling resistance and the stability of the alloy. With the addition of aluminum of more than 0.9 wt.%, Despite the increase in scaling resistance due to the passivation of the surface of the cast iron by the refractory compound, a decrease in the stability of the walls is observed.

. With the introduction of hafnium iron into the composition, a deep refining of the alloy and an increase in oxidation resistance occur. Samples of the hafnium-free alloy showed a more significant weight loss due to oxidation compared with g of the afnium-containing alloy. On the surface of the cast iron, containing aluminum and hafnium, it forms at high temperatures a scale containing AlzOj and HfOj. With an increase in temperature, the oxidized inclusions llfOz acquire a more distinct pattern of veins that grow into the metal base of the alloy, forming a protective film on the surface of the monolithic C. The lower limit of hafnium content in cast iron (0.06 wt.%) Is established by the formation of a strong oxide film. With an increase in the content of hafnium to 0.38 us,% adhesion of Tia calx alloys. The increase is due to the increase in the amount of hafnium oxide growing into the alloy matrix. Improving the additive of hafnium (0.38 wt.% Powder) does not give a further increase in) the resistance of pig iron.

Example. To obtain pig iron, three compositions of pig iron are melted down to the bottom 1 /.

it is average, upper and lower to the content of components and a known alloy with an average content of components.

The chemical composition of the known and the preliminary composition of cast iron is given in Table I.

Melting is carried out in a quartz lined induction furnace.

The materials used include pottery and pig iron, steel scrap, ferroalloys and dopants: ferromolybdenum (62% Mo), granulated nickel (97.6% Ni), metallic manganese (95.0% Mp) , ferrosilicon (78% Si), antimony (99.6% Sb), aluminum, silicocalcium (33.5% Ca).

Hafnium is introduced into the furnace 8-10 minutes before the end of smelting in the form of ferro-gafni. (21% Ilf) with the subsequent release of metal into the ladle and cast iron. The casting temperature is I320-ZbO C. Samples are poured, from which samples are cut for testing the scaling resistance and the stability of cast iron, as well as metallographic analysis,

Scaling is determined by the gravimetric method on samples K 25 at 700 and 950 C for 500 and 100.0 hours in a gaseous environment. As a heating unit using the pass. Known Medium.

3.2 1.8 0.0223 0.25 0.08 1.5 0.011

Proposed 1

2 3

Lower

Middle upper

3.2 2.3 0.1 0.1 O, 05 1.0 0.001 0.5 0.06. , A 2.65 0.25 0.23 0.07 1.5 0.01 0.7 0.22

3.6 3.0 0.4 0.35 0.1 2.0 0.02 0.9 0.38

our chamber furnace samples ;; which is suspended on a wire.

Table 2 shows the indicators of durability and stability at 700 and 950 C. The test time is 50 and 1000 h for each temperature.

As follows from Table 2, an additional input to the composition of cast iron A1 and Hf provides more than 5–8.8 times the oxidative stability and 1.4–4.2 times the stability,

ten

For5u. la invention

ChuGun containing carbon, silicon, manganese, molybdenum, antimony, nickel, calcium, and iron, which also

increase scaling resistance and growth-. stability when heated to 700-950 ° C with long-term exposure, it additionally contains aluminum and hafnium in the following ratio of com ..

ponent, wt.%:

0

five

Carbon

Silicon

Manganese

Molybdenum

Antimony

Nickel

Calcium

Aluminum

Hafnium

Iron

3.2-3.6 2.3-3.0 0.1-0.4 0.1-0.35 0.05-0.1 1.0-2.0 0.001-0.02

0.5-0.9 0.06-0.38 Else

Table 1

- The rest

Known 0.1 0.9

0.95 1.2A

0.068 0.34 0.065 0.26 0.064 0.24

0.3

0.24

0.20

Table 2

0.09 0.25

0.16 0.38

0.065 0.07 0.075 0.09 0.04 045 0.06 0.06 0.07 0.04 0.06 0.07 0.07 0.08

Claims (1)

Claim ChuGong containing carbon, silicon, manganese, molybdenum, antimony, nickel, calcium and iron, with the fact that, in order to increase the scale resistance and growth. stability when heated to 700,950 C with prolonged exposure, it additionally contains aluminum and hafnium in the following ratio com., ponents, wt.%: Carbon 3.2-3.6 Silicon 2.3-3.0 Manganese 0.1-0.4 Molybdenum 0.1-0.35 Antimony 0.05-0.1 Nickel 1.0-2.0 Calcium '0.001-0.02 Aluminum 0.5-0.9 Hafnium 0.06-0.38 Iron Rest Table 1 < Cast iron Component Level Content of components, wt.% - FROM Si ' Mp Mo Sb Ni Sa Al Hf Fe Famous Average 3.2 1.8 0,023 Proposal May 1 Lower 3.2 2,3 0.1 2 Average 3.4 2.65 0.25 3 Upper 3.6 3.0 0.4 0.25 0.08 1,5 0.01 1 Rest 0.1 0.05 1,0 0.001 0.5 0.06. 0.23 0,07 1,5 0.01 0.7 0.22 0.35 0.1 2.0 0.02 0.9 0.38 Table 2 Cast iron Scale resistance, g / m ² · temperature, ° C h at Resistance to temperature ° ,% growth, at FROM 700 950 700 950 500 h 1000 h 500 h 1000 h 500 h 1000 h 500 h YuOO.ch Famous 0.1 0.9 0.95 1.24 0.09 0.25 0.16 0.38 Suggested 1 0,068 0.34 oh s 0.6 0,065 0,07 0,075 0.09 2 0,065 0.26 0.24 0.38 0.04 0,045 0.06 0.07 3 0,064 0.24 0.20 0.32 0.04 0.06 0,07 0.08