SU1553568A1 - Cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the manufacture of pumps for pumping chemically aggressive media. The purpose of the invention is to increase the abrasive, impact-abrasive and abrasive-corrosion resistance, as well as increase the strength in the heat-treated state. New cast iron contains, wt.% C 1.8 - 2.8, SI 0.4 - 0.8, MN 0.5 - 1.5, CU 0.5 - 1.5, CR 26 - 30, TI 0 , 3 - 1.3, NB 0.5 - 2.2 and FE - the rest. The proposed method for producing pig iron includes loading charge materials, melting them, obtaining the basic chemical composition and subsequent processing of 5 to 15 wt.% Niobium-containing master alloy (NB 12 - 15%, C 4.5 - 5%, CR 26 - 30% and FE - the rest). Additional input into the composition of cast iron, obtained by the proposed method, NB and CU increases σ _and 1.2 - 1.3 times and abrasive resistance 1.5 - 2.6 times, impact-abrasive 5 - 5.5 times and abrasive - corrosion 1.5 times. 2 hp f-ly, 2 tab.

Description

The invention relates to metallurgy, in particular, to the development of compositions and methods for producing pig iron for pump parts for pumping chemically aggressive suspensions.

The purpose of the invention is to increase the abrasive, impact-abrasive and abrasive-corrosion resistance, as well as increase the strength in the heat-treated state.

The invention is illustrated by examples of specific performance.

The need for additional input to the composition of the proposed iron, copper and niobium due to the following.

Niobium is in the ligature as NbC carbides. With its introduction into the liquid; the iron is reacting

NbC + Ti (Ti, Nb) C

with the formation of complex carbide (Ti, Nb) C, having a density close to the density of the liquid alloy and uniformly distributed throughout its volume, so that

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eliminates the danger of formation of large segregation of carbides in castings and pshakometallichesky mixture as a result of their ascent

High abrasive resistance of the proposed cast iron is achieved due to the increased number of carbides compared to the prototype, in particular carbides (lib, Ti) C with high microhardness (HЈo 2000). Due to the uniform distribution of carbides and their dispersion, the proposed cast iron combines high abrasive resistance with high strength (Gu) and shock-abrasive resistance.

High corrosion resistance at low chromium to carbon ratios is ensured by the fact that a significant portion of carbon is consumed to form carbides (NbTi) C, while the concentration of chromium in the base remains quite high.

Copper is injected into cast iron to increase hardenability, i.e., to increase the abrasive resistance of massive castings.

4 The positive properties of copper also include the fact that, by increasing the stability of the austenta of the pearlite region, it slightly, compared with other elements, such as manganese, reduces the temperature of the onset of the martensitic transformation, i.e. provides a minimum amount of austenite in the structure. With the introduction of copper less than 0.5%, its effect on properties is insignificant, the upper limit is associated with its limited solubility in iron alloys.

Table 1 shows the chemical content and properties of the proposed and well-known cast iron.

The structure of the proposed cast iron consists of chromistocarbide eutectics, dispersed; carbides (MJbTi) C in solid solution.

The ratio Nb; Ti must be 2 so that the density of carbides (NbTI) C is equal to the density of liquid iron.

The content of Nb STs5-2,2. With a lower niobium content, the amount of carbides in the iron is insignificant and does not affect the properties of the alloy.

The ratio of Nb: Ti should be 2: t, since titanium replaces up to 50% niobium in NbC carbide, and its density is about 2 times lower. If more titanium is introduced, carbides are precipitated.

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TiC, which due to low density float and are removed from the melt. If, however, less titanium is introduced, the consumption of expensive and scarce niobium increases, and without improving the properties.

Thus, a stable production of the required amount of dispersed uniformly distributed carbides (NbTi) C, which are the centers of crystallization, is achieved, resulting in a crushing of the structure (primary grain) and increased wear resistance, strength, impact-abrasive resistance and corrosion resistance.

The technology for producing the proposed cast iron is as follows.

First, by loading fir materials into an induction furnace, heating, melting and adjusting the temperature to 1550 ° C, base iron is melted. Then, 2-3 min before the release, a niobium-containing ligature is added to the furnace in the amount of 3-17%, the chemical composition of which is given in the claims.

Data on the methods of smelting iron, its chemical composition and level of properties are given in Table. 1 and 2.

As follows from the data table. 1 and 2, additional input into the composition of cast iron Cu and lib allowed to increase 1, t 1.3 times, abrasive resistance 1.15-2.6 times, shock-abrasive resistance 5-5.5 times and abrasive - corrosion resistance 1.5 times.

Claims (3)

Claim 1. Carbon-containing iron, silicon, manganese, chromium, titanium, iron, characterized in that, in order to increase abrasive, impact-abrasive and abrasive-corrosion resistance, as well as to increase the strength in the heat-treated state, it additionally contains copper and niobium at the following the ratio of components, May. %: Carbon 1.8-2.8 Silicon0.4-0.8 Manganese 0.5-1.5 Copper 0.5-1.5 Niobium 0.5-2.2 Hrom26-30 Titan0.3-1.3. IronErest 2. A method for producing pig iron, comprising loading charge materials, ae 1.7-2.0 0.4-0.8 0.5-1.5 26-30 0.3-1.3 Else and fine-tuning to a predetermined 10 time setting for melting and copper is introduced into the charge. 3. A method according to claim 2, characterized in that the ligature of the next chemical tava, May, is introduced into the melt. %: Carbon4,5-5,0 Niobium .12-15 Hrom26-30 IronErest