SU1537692A1 - Method of producing 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 obtain uniform hardness in thin-walled castings, reducing the cost of iron while maintaining the level of mechanical properties. The proposed method for producing pig iron includes loading into the smelting unit of pig iron, carbon semi-finished product and its own return, overheating the melt to 1580 - 1650 ° C, modifying the melt with a ligature containing rare earth elements at the 1st stage, and ferrosilicon at the 2nd stage. Use as a component of the mixture of carbon semi-product / C * 983.5%, SI, MN, CR and up to V 0.1%

TI is up to 0.03% and FE is the rest / in the amount of 5-30% of the mass of the charge, the introduction of the cerium group into the RZM melt and the prostrating Ferrosilicon modification allows to obtain a uniform hardness in different sections of the castings. 2 hp f-ly, 2 tab.

Description

The invention relates to metallurgy, in particular to the development of methods for producing pig iron for thin-walled castings - piston rings.

The purpose of the invention is to obtain uniform hardness in thin-walled castings, reducing the cost of iron while maintaining the level of mechanical properties.

The use of carbon semi-finished product in the charge, which is pure in silicon and manganese, instead of traditional blast furnace cast iron, makes it possible to make full use of the resulting own doped return.

This reduces the calculated addition of alloying elements and due to a more uniform distribution of the main part of alloying elements in their own return as compared with high-percentage refractory nickel, vanadium, chromium and molybdenum ferroalloys, it is easier to produce liquid pigment microhomogeneous in alloying elements. This is critical to obtaining uniform hardness and structure in particularly thin-walled castings.

Carbon intermediate containing,%: carbon 3.5-4.5; silicon 0,02sl

00

one

O5

with

0.1 manganese 0.02-0.1 - chromium 0.02- 0.1, vanadium 0.02-0.1; titanium 0.01-0.1 iron else, obtained by processing vanadium-containing tantano-magnetite ores to ferrovanadium by blowing air (oxygen) in the converter of pig iron from low temperatures with an additive of oxidizer - cooler (agglomerate). The purge mode provides the maximum degree of oxidation of silicon and the deanation. The resulting semi-carbonaceous semi-product is mainly used for further processing into steel during open-hearth smelting.

The compositions of the carbonaceous intermediate depending on the purge mode are listed in Table 1.

The most optimal for the proposed method of smelting is composition 2, containing,%: carbon 3.5–4.5 (silicon 0.02–0.1; manganese 0.02– 0.1. The presence in its composition is 0, 02-0.1% of chromium, 0.02-0.1% of vanadium and 0.01-0.1% of titanium to a large extent provide the required level of alloying of cast iron with these elements.

However, due to its nature of production, it is additionally saturated with gases (oxygen and nitrogen), which does not ensure the required quality of the castings. Therefore, a preliminary overheating of the melt, obtained on the basis of the carbonaceous semiproduct and its own return to 1580-1650 C, is provided, which ensures high microhomogeneity of the melt, complete dissolution and uniform distribution of the alloying elements throughout the melt. Active boiling of the melt helps to remove large non-metallic inclusions and dissolve dispersed particles. This creates a favorable situation for the subsequent two-stage modification. Measurement of the activity of the dissolved acidic (wasp) showed that when preheated to 1580-1650 ° C, a0 is (4-6) 10 and decreases sharply to (1, 5-, 2) 00 due to the introduction of active elements (REM) with the first stage of modification is above the equilibrium temperature of the crucible reaction. For cast irons of which piston rings are made, the equilibrium temperature of the crucible reaction is J360-1400 ° C. Repeated remelting of its own return reduces the susceptibility of the melt to subsequent modification. The use of coal 11-rodstogo of the intermediate product, together with additional overheating up to the suggested temperature range, makes it possible to increase the susceptibility to the subsequent two-stage modification.

The lower limit of the superheat temperature (1580 ° C) is necessary to achieve the required melt homogeneity and oxygen activity when using the charge based on the carbonaceous intermediate. Above the upper limit (1650 ° C), this effect does not increase, however, carbon loss increases, energy consumption increases, and wear of the furnace lining.

Subsequent double processing (above and below the equilibrium temperatures of the crucible reaction) provides a high graphitizing effect. The input limits for the carbon semi-product are determined by the yield during the casting of piston rings (lower limit 1-10), as well as increased consumption of silicon and other ferroalloys (upper limit 1-5).

The tests are carried out in the smelting of pig iron containing,%: C 3.5-3.8; Si 2.3-2.8; Mp 0.5-0.8, Cr 0.2-0.4; Ni 0.15-0.35 Mo 0.3-0.5, P 0.3-0.6, in an induction furnace with a capacity of 40 kg.

The method is carried out as follows.

The induction furnace is charged with charge materials consisting of carbon semi-finished cast iron and a return of its own production in a certain respect. The melt is overheated to 1580–1650 ° C, refractory alloying agents are introduced at this temperature: ferromolybdenum — 50% molybdenum, ferrochrome — 75% chromium, ferromanganese — 75% manganese, ferrovanadium — 55% vanadium. Next, the melt is heated to the temperature of the first stage of modification, poured at 1460 ° C into an intermediate ladle, in which it is treated with a 0.05% complex modifier containing 30% REM (cerium group), 5% barium, 1% strontium, and up to the temperature of the second stage (1380 C) and at overflow in the casting ladle 0.5% is introduced

ferrosilicon (FS-75). Next, the molds are cast.

Special samples are poured with section 4) (4 mm, 100 mm long into raw forms through one end feeder. This sample simulates the conditions for producing thin-walled piston ring castings. The microstructure is found and the variation of hardness over the sample length of five is determined points on 10 samples.

The properties of cast iron, obtained by the proposed and known methods, are presented in table 2.

As it follows from the above data, the proposed method for producing pig iron allows, through the use of carbon precursor melt overheating as a component of the charge, to obtain uniform hardness in different cross sections of piston rings before modifying, to reduce the cost of 1 ton of pig iron.

Claims (3)

1. Method for producing pig iron, preferably for piston blanks 0 rings, including loading the charge into the melting unit, fine-tuning the melt to a predetermined temperature, modifying the melt with a cerium-containing substance in the first stage and silicon-containing substance in the second stage, characterized in that, in order to obtain uniform hardness in the piston rings, to reduce the cost of iron, 5–30% of the carbonaceous intermediate product is introduced into the mixture, and the melt is superheated to 1580–1650 ° C before modification. 2. A method according to claim 1, characterized in that the carbon semi-product contains the ingredients in the following ratio, wt%: Carbon Silicon Manganese Chromium Vanadium 5 Titan Iron 3. The method according to claim 1, u and with the fact that 0 ferrosilicon is used in the low-containing substance. 3.5-4.5 0.02-0.10 0.02-0.10 0.02-0.10 0.02-0.10 0.02-0.10 Else about ton l and h ago - quality cream Note. According to a known method, an alloy is used as a modifier, containing May.2: REM 30; Ba 5; Sr I; Si and Fe else, table 2