SU1235912A1 - Method of producing castings of high-quality cast iron - Google Patents

Description

The invention relates to a foundry, specifically for iron foundries, smelting conventional gray structural eutectic cast iron with lamellar graphite, to significantly increase the strength properties of castings.

The purpose of the invention is to reduce the temperature and duration of graphitizing annealing,

The use of structural eutectic gray cast iron with lamellar graphite as a starting material for producing high-quality cast iron, due to the high content of carbon and silicon in it, ensures the flow of graphitization at low temperatures and in a short time.

The introduction of boron in an amount of 0.06-0.08 wt.% Is aimed at suppressing crystallization of lamellar graphite and converting gray eutectic cast iron with lamellar graphite into white, but able to graphitize during annealing. The content of 0.06-0.08% of boron is critical, in which annealing of pig iron is still possible within reasonable time limits, but it is not enough to guarantee suppression of crystallization of lamellar graphite, for example, with an elevated silicon content in the iron. Subsequent modification of 0.10–0.15% cerium stabilizes carbides, enhances the bleaching effect of boron casting and increases the compactness of carbon annealing. The combined use of boron and cerium ensures stable production of cast iron with a fully supplied

Laminated graphite release, but not deprived of the ability to anneal, but on the contrary, with a lightweight annealing ability.

Sequential transformation of gray structural eutectic iron (by doping 0.06-- 0.08% B and modifying - 0.15% Ce) into white with completely suppressed release of lamellar graphite allows to obtain castings with compact graphite by graphitizing annealing. and high strength. At the same time, the original gray cast iron, which reaches 8 redistribution, is free from the limitations of the composition typical of high-strength nodular cast iron and ductile cast iron.

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The npej3 araeMb method is as follows.

Structural eutectic gray cast iron with lamellar graphite by electric furnace or cupola melting is alloyed in the melting unit with boron in the amount of 0.06-0.08% of meta-welding. The calculation of the addition of boron is carried out only on fresh materials, since the waste from its return is insignificant. Before the metal is released from the furnace, the rare-earth modifier SCMICh or SIITMISH is added to the casting ladle at the rate of introducing 0.10-0.15% cerium. The molds are poured no later than 5–7 minutes after the assimilation of the rare-earth modifier.

Castings obtain a white iron structure and are nugged in a graphitic-fusher annealing in order to give them specified strength properties,

Graphitizing annealing of castings takes place at 820-850 s for 12-15 hours. Before obtaining the pearlite structure after graphitizing annealing, the cooling of the castings is carried out in air, The synthesis of the ferritic structure after the graphitizing annealing is obtained by cooling the castings first. d t for 2-3 hours in the range of temperatures 740-710 ° C, and then cooled in air,.

Example, To obtain castings according to the proposed method, crucible cast iron is used as the initial cast iron, having the composition, in wt%: 3.27 ° C; 2.05 Si; 0.71 MP; 0.12 Cr; 0,14 S. ° The specified cast iron has a strength of MPa and chill on the wedge sample, 35 mm. The original cast iron is melted in an IST-016 induction furnace. The melt is alloyed in a furnace with boron, modified in a ladle with a series and. poured fractionally, varying the concentration of boron and cerium. The resulting metal is poured into samples, which are monitored on a saucer and subjected to graphitizing annealing according to the following conditions: heating to a temperature of 820-850 0 for 2.5 hours, isothermal aging at this temperature for 13 hours, and air cooling. Samples of wiping in cast iron chips dp reduce oxidation and decarburization

The characteristics of the microstructure and mechanical properties of the cast samples with different variants of the proposed method are shown in the table.

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To compare the proposed s-graphite and mechanical properties

soba with known ductile iron, b 330 MPa, and HB-136.

having a chemical composition, wt.%: Thus, the proposed SPO2, 6 C; 0.90 Si; 0.54 MP; 0.08 S; Collecting castings from high-grade, 05 Cr, cast samples. Domestic iron cast iron allows for the casting of alloyed in a furnace to add 0.035% of the original metal using a tool and modify ordinary ladlee cast iron in the ladle without

eating 0.02% and bismuth 0.003%. Having severe restrictions on hit points is also annealed in cast iron chips, which are typical of high mode: heating up to 950 ° C during JQ coarse and ductile iron, but

4 h, holding at 950 C for a period of 8 hours for castings, cooling to 740 ° C during the high-strength properties typical of these, cooling to 710 ° C, for less high-quality cast iron

4h and Next on the air. Imb-energy consumption samples by reducing the temperature of the ferritic structure with co-shaped J5 and annealing time.

Claims (1)

METHOD FOR PRODUCING CASTINGS FROM HIGH-QUALITY CAST IRON, including smelting, alloying of molten metal with boron, modification, casting and graphitizing annealing, distinguished by the fact that, in order to reduce the temperature and duration of graphitizing annealing, gray cast iron is melted as initial cast iron the modification is carried out with cerium in an amount of 0.10-0.15% by weight of the metal, and boron is introduced in an amount of 0.06-0.08% by weight of the metal. bj with joint venture 1 1235912