SU1252381A1 - Malleable cast iron - Google Patents

Description

 one

Ioretration refers to metallurgy and can be used in the manufacture of cast details of automobile and agricultural machines, which during operation are subjected to considerable stresses under conditions of repeated repetitions of shock loads.

The purpose of the invention is to increase the microhardness and impact-fatigue strength of cast iron.

Example. The cast iron of the proposed composition is melted in an acid lined induction furnace. As fir materials, pig iron, steel scrap, ferrosilicon, and ferromanganese are used. When the temperature reaches 1500 + 5 ° С, fractional casting of metal is performed. Release of the metal is dried in a heated up to 400 t10 ° C and scoop-free bucket with the calculated amounts of modifiers loaded to the bottom - cerium and samarium. After slag cleaning and reaching a temperature of 132T) t5 ° C, sand-clay forms are poured into cylindrical specimens with a diameter of 50 mm and a height of 200 mm. To obtain the known iron, the necessary amounts of molybdenum are added to the metal remaining in the furnace, and the sample is poured in with the same temperature and time parameters. The heat treatment is carried out in the following mode: heating to 350-400 ° C, holding for 4 hours, heating to 950-1050 ° C, holding for 8 hours, cooling with a furnace to 720 ° C, holding for 12 hours and final cooling with a furnace.

When establishing the required ratios of components take into account the following.

Carbon is the main regulator of the properties of ductile iron. At concentrations higher than the upper limit (2.9 wt.%), The number and size of graphite inclusions sharply increase, which causes a decrease in both strength and plastic properties. With a decrease in carbon concentrations below 2.5 May. The process of melting is difficult, the cost of the products is worse.

With the amounts of flint vpepe 1.2 May. % in raw castings are separated from graphite inclusions, which leads to a sharp decrease in the physicomechanical properties of ductile iron. Reduction

523812

The same concentrations of silicon below 0.8% by mass. This means a decrease in the strength characteristics of ductile iron.

At concentrations of 0.6 wt.% 5, manganese has a inhibitory effect on graphitization, increases the annealing time, and leads to a decrease in plastic characteristics. The properties of malleable cast iron with martian content of 10 ga below 0.3 may. The% deteriorates dramatically due to the release of graphite inclusions in the raw castings.

L / Pomini within the specified limits will improve impact fatigue strength

15 cast iron. However, it has become graphitized.

 element, aluminum at concentrations above 0.03 May. % causes you-. the division of graphite inclusions in these casts, which reduces the properties of someone who has cast iron. At concentrations below 0.02 May. % effect of aluminum is negligible

When selecting the elements; y1, simultaneously increasing the strength and plastic characteristics of ductile iron, proceed from the following. As is known, H, o, and both depend on the matrix, on the purity of the grain boundaries, and on graphite. Therefore, by improving the shape of graphite-.

30 inclusions, striving to obtain F - 0.95-1.0 with a ferritic matrix, we thereby increase the value of the. The studies performed allow us to choose elements from rare-earth elements, I

35 which are simultaneously spheroidizing (from graphite inclusions and increase the microhardness (and therefore strength) of ferrite. Such elements are cerium and samarium. Optimal limits for the contents of these elements, ensuring the maximum growth of the characteristics under consideration, are 0.10-0.15 mass% of each. With cerium or samarium concentrations below 10 May,%, their influence is insignificant. The shape factor of graphite compounds decreases to 0.65–0.70. With an increase in their concentrations of more than 0.15 May.% begins to prevail

50 matrix effect. Strength increases, and plastic properties drop. With the proposed concentrations of cerium and samarium, the impact fatigue strength of ductile iron 55 Ni has maximum values.

The chemical compositions of the cast iron and the test results are given in

abl 1 and 2

ny

gageun

2.5 0.90.320.020 0.50

2.9 1,250,580,024 0,82

2.5 1.20,60,030

1,20,60,020

0,80,60,030

0,80,60,020

1,20,30,020

1,20,30,030

0,80,30,020

0,80,30,030

1,00,450,025

1,00,45.0,025

1,00,450,025

1,00,450,025

1,00,450,025

Table 1

Rest

0.15 0.15

0.15 0.10 0.10 0.10 0.10 0.15 0.15 0.08 0.10 0.12 0.05 0.15 0.20

Rest

As a result of laboratory studies, it was found that the impact fatigue strength of the proposed cast iron increases by 52.4-57.2Z in comparison with the known cast iron, and the microhardness of the matrix increases 2.0-2.2 times.

The use of the proposed cast iron for casting car parts. The order is 4591/29. Circulation 567

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Random polygons pr-tie, Uzhgorod, st. Project, 4

Table 2

low-cost and agricultural engineering will increase the durability and reliability of MaimiH. The proposed cast iron will result in an increase in the properties of the castings, thereby increasing their operational durability by 50-60%. Godova will save 1369354 rubles.

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Claims (1)

MOVEMENT CAST IRON, containing carbon, silicon, manganese, aluminum and iron, characterized in that, in order to increase micro-hardness and shock-fatigue strength, it additionally contains cerium and samarium in the following ratio of components, May, Z: Carbon 2.5-2.9 Silicon 0.8-1.2 Manganese 0.3-0.6 Aluminum 0.02-0.03 Cerium 0.10-0, ι5 Samarium 0.10-0.15 Iron Rest