SU996502A1 - Cast iron - Google Patents

Description

(5) CAST IRON

 The invention relates to metallurgy, in particular to cast iron for centrifugal casting. Known cast iron l has the following chemical composition, weight: Carbon -2.8-3.8 Silicon 1.6-2.6 Manganese 0.5-1.0 Calcium 0.05-0.1 Bor0.05-0-0.1 Nitrogen , 0.01-0.1 IronOstal The disadvantage of the known cast iron is: the technological effectiveness of the input of additives containing sampling and nitrogen, the difficulty of controlling the content of these additives in the iron. The closest to the proposed cast iron by its technical essence and the achieved result is cast iron 2 of the following chemical composition, weight,%: Carbon 3.0-3.6 - Manganese, 0-5.0 Silicon -. 2.0-2.5 Copper1.8-2.5 Aluminum 0, f-0.6 Iron Rest The disadvantage of this iron is a high copper content, over 1.8 weight .. Its low solubility in cast iron at low temperatures leads to that it is distributed primarily on the interfacial surfaces. Such a preferential distribution of copper inhibits the breakdown of cementite. In some cases, stabilization of cementite is desirable. However, for centrifugally cast pipes that are molded into a metal mold and have a large chill depth, stabilization of cementite is undesirable, since the pipes after casting are subjected to graphitizing annealing. The high content of manganese in the iron leads to an increase in chill and a sharp increase in the marriage of cold cracks. Obtaining through bleaching of pipes, which is difficult to prevent by annealing at 910 ° C, leads to a decrease in the modulus of ring strength below the allowable one.

The purpose of the invention is to increase the modulus of annular pipe strength.

The goal is achieved by the fact that cast iron containing carbon, silicon, manganese, copper, aluminum and iron, additionally contains tin in the following ratio of components, wt.%:

Carbon 3.2-3.8 Silicon 1.2-1.9 Manganese 0.2-0.8 Aluminum 0, -1.0 Copper0.4-0.6

Tin 0.1-0.2

Iron Else

Known A

3.4 2.3 4.2

Centrifugally cast pipes are subjected to heat treatment according to the mode: heating to 910 ° C, holding for 10 minutes, cooling in a furnace to 780 ° C, then air cooling. Determination of mechanical properties is carried out on ring specimens

Cast iron, R, MPa Ii

520 550 600

200

Experienced cast irons were smelted in a 16 t / h cupola with a base lining. The charge of the experimental heats consists of cast iron, kO%,

pig iron 50%, steel scrap 5%, secondary ferrool%. Secondary granular aluminum chemical composition according to GOST 295-73 is introduced into the tundish with a capacity of 3 tons.

Cast iron pipes with a diameter of 150 mm and a length of 400 mm are cast in a centrifugal method in water-rich metal molds on machines of the 543 model. The casting and crystallization time is 2 minutes.

In tab. 1. shows the chemical composition of the proposed and known iron.

Table 1

||

0.5

2.0

25 mm in diameter, cut from the pipe on the side opposite to the socket. The modulus of the ring strength of pipes 40 is determined according to GOST 9583-71).

In tab. Figure 2 shows the mechanical properties of the proposed and known cast iron.

Table 2

External surface hardness, HB

229 217 210

270

As can be seen from the table, the hardness of the outer surface of the pipes for the proposed iron corresponds. GOST 9583-75, where it is stated that it should not exceed HB 230. Cast iron of known composition after annealing in a continuous kiln in the conventional manner has a structure with a large number of undissolved cementite. This leads to the fact that the hardness on the outer surface is higher than the allowable GOST 9S83-75. The modulus of ring strength for these pipes is significantly lower than that required by GOST 9583-75 ("00 MPa). T | eubes from the proposed .chugun have mo; ring bore strength is 2.5-3 times more than the known one. The strength of cast iron pipes determines not only the scrap rate of the pipe-smelting shops, but also the destruction of the transportation and unloading times and, most importantly, during the operation. The destruction of a ONE pipe in a water supply network requires the cost of repairing it, which is approximately 3,000 rubles. The use of the proposed iron allows to increase the amount of steel scrap in the charge and reduce the consumption of ferromanganese and ferrosilicon. The annual economic effect in the production of pipes by one workshop of the proposed iron is 92,990 rubles.

Claims (2)

1. The USSR author's certificate number 6Y2367. cl. C 22 C 37/10. 1977. 2. USSR author's certificate number 428032, cl. C 22 C 37/10, 1972.