SU918326A1 - Cast iron composition - Google Patents

Description

(54) CAST IRON

.one

The invention relates to metallurgy, in particular to finding gray ones; graphite cast irons for the production of thin-walled (k-S mm) centrifugal-cast pipes.

Known gray cast iron for the production of pipes of the following composition, weight .:

Carbon 2.90-3.60. Silicon t, 60-2, tO

Manganese Oh, "0-0,80

Iron Else

As impurities, cast iron contains., Wt .: phosphorus up to 0.30 and sulfur up to 0.12 l.

The disadvantages of cast iron are low fluidity, low tightness and the presence of chill.

The closest to the proposed technical essence and the achieved effect is cast iron of the following chemical composition, weight .:

Carbon 2.80-3.60

Silicon 1, "0-2,60

0.80-1.60

Manganese

Yttrium 0.06-0.12

Zirconium 0.05-0.15

Rare earth

0.08-0.30

metals

Iron Else As impurities, iron contains, weight: phosphorus to 0.20, sulfur to; 0.13, chromium to 0.20, nickel to 0 ,.

However, this cast iron is characterized by poor fluidity in the temperature range 12bO, which is especially important for long-term casting (20-25 min) of cast iron into molds of small metal consumption, insufficient tightness of thin-walled castings from this iron and the presence of chill in them. In addition, with simultaneous modification with yttrium and zirconium (within the indicated concentration limits), the effect of the modification is retained for a short time. 39 Yttrium, zirconium and rare earth metals are introduced into the known cast iron in the form of expensive, specially eluted ligatures. The purpose of the invention is to increase the fluidity and elimination of chill. This goal is achieved by the fact that cast iron containing carbon, silicon, manganese, zirconium, rare earth metals and iron, additionally contains aluminum in the following ratio of components, weightD: 2, ZOGZ, 60 Carbon. 1.60-2.40 CRE / 1NI 0.40-0.80 Manganese0, 15-0.30 Zirconium Rare-earth 0.01-0.10 metals 0.05-0.30 Aluminum. Iron The introduction of zirconium, rare-earth metals and aluminum is carried out in the form of a mixture of powdered potassium fluoro-zirconate flux, a concomitant element in which lanthanum is found, and aluminum chips in a weight ratio of 3: 2. The amount of modifier introduced is 0,, 00 by weight of the liquid metal. When using carbon and silicon in the composition of cast iron at the lower limit, the amount of potassium fluorozirconate and aluminum should be deposited on the upper limit. Gray cast iron is melted in a cupola and released into a dispensing bucket (with a capacity of 1 ton) at 1350-1370 ° C. Before releasing the cast iron to the bottom of the bucket, which has a temperature of USO-HEO K, load: a modifier. Casting of modified iron is produced in a wider temperature range of 1200-1320 °. The lower limit of the temperature of casting of the modified iron is shifted by increasing the fluidity of the melt to ensure complete pouring of the metal from the dispensing bucket. The best is cast iron following weight.

its composition.

5.6 Carbon

1.8 Silicon

0.4 Manganese

0.3 Zirconium

0.1 REM

0.30

Aluminum

The rest of the iron

graphite graphite.

Hydrogen contributes to carbide formation and increases the stability of iron carbides, and also causes the formation of sieve porosity and gas pockets in castings.

Claims (2)

The introduction of aluminum has either direct or indirect effects. The mechanical properties of the proposed gray iron: Tensile strength, MPa. 150-290 Flexural strength, MPa 350-40 Examples of cast iron according to this invention and known are given in the table. The fluidity of the iron is determined by pouring a spiral sample. The degree of chill is determined by metallographic examination of samples cut from the tubes of experimental batches. The tightness of the pipes shall be assessed by the number of through gas shells, which were tested in the hydro stand. The concentration range of Ag, which corresponds to the achievement of the goal, is equal to 0.05. With the introduction of aluminum less than 0.05, there is a deterioration in fluidity, an increase in the foundry scrap in the gas shells and the degree of chill in the castings. An increase in the concentration of aluminum of more than 0.3 does not lead to a further improvement in the technological properties of cast iron, in particular, fluid leakage and tightness, and it is not economically feasible. The basis for choosing the specified concentration range of aluminum cast in the cast is based on its influence as an active degasser, reducing the gas content in the cast iron on the one hand, and an alloying element (graphitizer) that promotes the formation of crystallization centers and growth of graphite inclusions, on the other hand. Gases (O, H, N) have a significant effect on the nature of the crystallization of pig iron. Oxygen lowers the carbon activity in the melt. With a decrease in its concentration, a transition from the crystallization of the coarse fiber A g u iijjri wji riri I rj 1-L tinny to the formation of a thin plate is observed; As a result of a change in the lawn of iron content, i.e. reducing the content of O, H, N in the melt, improves its fluidity and decreases the propensity to form gas pockets, both due to the reduction of gases in the metal, and due to the improvement of fluidity. Microalloying of cast iron with aluminum binds most of the dissolved oxygen to oxides, nitrogen to nitrides, removes nitrogen from the boundary zones, facilitating the process of nucleation and growth of graphite centers. Aluminum, being graphitizatoro, helps to eliminate chill. in / castings. Due to the formation of refractory AbaO 3 and A6N refractory inclusions in the melt, which, in connection with grade 26, the parameters of the lattice with graphite, are the crystallization centers of graphite, the graphitization process (in this case) is more active and leads to the refinement of graphite inclusions. It is known that tightness depends on (| jurma, size and nature, location of graphite inclusions creating graphite porosity, gas saturation and fluidity of the metal, affecting the formation of gas holes in castings. The pressure tightness of cast iron due to the addition of aluminum is caused by a decrease in gas saturation of the metal, to improve its fluidity and reduce graphite porosity, due to the grinding of graphite inclusions. Invention Cast iron containing carbon, silicon, manganese, zirconium, rare earth metals and iron, which is distinguished by the fact that, in order to increase the fluidity and eliminate chill, it additionally contains aluminum in the following ratio of components, weightD: 2.9-3.6 Carbon 1.6-2.1 Silicon 0 ,, 8 Manganese at hand 197 Vf 6 Zirconium 0.15-0.3 Rare-earth 0.01-0.1 Metals Aluminum 0.05-0.30 Iron Else Sources of information taken into account during the examination 1. Collection of technological instkts in the pipe shop. Lipetsk, 2. 2. Authors certificate of the USSR 92887, cl. C 22 C 37/10, 1975