PL180082B1 - Method of obtaining inoculated grey cast iron from steel scrape - Google Patents

Abstract

1. A method of producing modified gray cast iron from steel scrap, in which, scrap of sorrow it feels like fuggling is bad and it falls down abrobcz żarzaSzmpzraSurawzj, characterized by the fact that the Sapizfiz is carried out in a pizzeria and a production Plasma Sraf shaped into a pizca packet, azafavis plasma, and what a fawęglacz S O 1460-1500 ° C and in Szj SempzrySurzz for 10-15 mifuS, and fasSęp ^ c abm ^ The chancellery of mzSal will reach 1400 ° C and the content of chica and maftaf is complemented by adpowiydajczj wżp0łceoffikawifysoczfia zuSekSoczfzaa (Sc) = 0.8 -1.0 i paddajz eabieaowi madyOikacji jzdfym zz zfoch spasabów.

Description

The subject of the invention is a method for the production of modified gray cast iron from steel scrap.

In the previously known methods of smelting modified gray cast iron, pig iron, foundry's own scrap and external scrap are used as charge materials, and the melting process is carried out in cupolas or electric, induction or arc furnaces. Cast iron made of these materials with a suitable chemical composition is subjected to a modification treatment using one of the known methods.

There is also a known method of producing cast iron from steel scrap, the so-called synthetic cast iron in electric furnaces, consisting in enrichment of steel scrap with carbon, silicon and other elements. The most important process in the production of synthetic cast iron is the carburizing of steel to the carbon content required in cast iron and high-temperature treatment of the liquid metal in order to change the physicochemical state of the liquid metal.

Currently, there are two methods of carburizing steel scrap in an induction furnace. The first consists in melting the scrap together with a solid carburizer, the second in blowing powdered carburizer into the liquid metal in a stream of nitrogen or air. The carburizing efficiency of both methods ranges from 40-70%.

The new method of producing modified gray cast iron is based on the advantages of an induction-plasma furnace for carburizing steel scrap and refining liquid metal.

The method of obtaining cast iron according to the invention consists in melting steel scrap together with solid carburizer and subjecting it to high-temperature treatment. The essence of the invention consists in the fact that the melting process is carried out in an induction furnace equipped with an argon plasma generating plasmatron, where graphite carburite is used as the carburite. The liquid metal is superheated to the temperature of 1460-1500 ° C and kept at this temperature for 10-15 minutes. Then the metal temperature is lowered to 1400 ° C and the content of silicon and manganese is adjusted to the content corresponding to the eutectic saturation coefficient Sc of the produced cast iron in the range from 0.8-1.0 and subjected to a modification treatment using one of the known methods.

Preferably, after completing the chemical composition, a slag is applied to the surface of the liquid metal, and the liquid metal is subjected to additional treatment under the slag heated with plasma.

180 082

The use of an induction furnace equipped with a plasmatron located in the furnace cover, generating argon plasma, gives more favorable conditions from the metallurgical point of view, and the use of argon as plasma gas promotes the desorption of gaseous pollutants from the liquid metal, reduces the loss of alloy elements and ensures high efficiency of carburizing liquid metal exceeding 90 %.

The high temperature of the plasma arc quickly liquefies the slag and activates the metallurgical processes between the slag and the metal.

The subject of the invention is presented in the following examples.

Example I. Steel scrap and graphite carbite were charged to the induction-plasma furnace in the amount of 3% of the charge with the chemical composition given in Table 1.

Table 1

Chemical composition of input materials

Material Chemical composition, % C. Si Me P. S. Steel scrap 0.21 0.36 0.64 0.014 0.017 Graphite carburite 96.88 - - - 0.14

The charge was plasma-induction melted. After melting the loaded part of the charge, the plasmatron operation was stopped and the steel scrap left to fill the furnace was recharged. After melting the steel scrap, the liquid metal was kept under argon plasma at the temperature of 1460-1480 ° C for 10 minutes, and then the metal temperature was lowered to 1400 ° C. Then, the melting slag was removed, the plasmatron was turned on and FeSilicon Si75 was added in an amount of 1.2% by weight of the liquid metal and FeMn40 ferromanganese in an amount of 0.25% by weight of the liquid metal. The chemical composition of the starting cast iron for modification is given in Table 2.

Table 2

Chemical composition, % c Si Me P. S. 3.05 1.16 0.83 0.025 0.029

Cast iron was modified with an Inoculin 25 type modifier in the amount of 0.6% of the charge weight. Gray cast iron was obtained with the chemical composition and properties specified in Table 3.

Chemical composition and properties of synthetic gray cast iron

Table 3

Chemical composition, % Mechanical properties C. Si Me P. S. Rm " hb ²⁾ 2.99 1.68 0.85 0.025 0.031 299 MPa 207

1- tensile strength,

2- Brinell hardness.

Example II. Steel scrap and graphite carburite were loaded into the induction-plasma furnace in the amount of 3% of the charge mass with the chemical composition given in Table 1.

The charge was plasma-induction melted. After melting the loaded part of the charge, the plasmatron operation was stopped and the steel scrap left to fill the furnace was recharged. After melting the steel scrap, the liquid metal was kept under argon plasma at temperature4

180,082 at 1460-1480 ° C for 15 minutes, after which the metal temperature was lowered to 1400 ° C. Then, the melting slag was removed, the plasmatron was turned on and ferrosilicon in the amount of 1.6% of the weight of the liquid metal was added and the glass cullet slag was applied. The liquid metal was refined under the slag heated with argon plasma for 10 minutes. The cast iron was obtained with the chemical composition given in Table 4.

Table 4

Chemical composition of the starting cast iron for modification

Chemical composition, % c Si Me P. S. 2.87 1.58 0.62 0.15 0.023

Cast iron was modified with a Si75A12 type modifier in the amount of 0.5% of the charge weight. The cast iron was obtained with the chemical composition and properties given in Table 5.

Chemical composition and properties of synthetic gray cast iron

Table 5

Chemical composition, % Mechanical properties C. Si Me P. S. Rm " hb ²⁾ 2.79 2.16 0.62 0.016 0.023 452 MPa 256

-tensile strength, 2- Brinell hardness.

Publishing Department of the UP RP. Circulation of 60 copies

Price PLN 2.00.

Claims (2)

Patent claims 1. Method for the production of modified gray cast iron from steel scrap, in which the steel scrap is melted with solid carburizer and subjected to high-temperature treatment, characterized in that the melting is carried out in an induction furnace equipped with a plasmatron placed in the furnace cover, generating argon plasma, and graphite carburite is used as a carburite, then the liquid metal is overheated to a temperature of 1460-1500 ° C and kept at this temperature for 10-15 minutes, then the metal temperature is lowered to 1400 ° C and the content of silicon and manganese in cast iron is supplemented to a content corresponding to the eutectic saturation factor (Sc) = 0.8-1.0 and subjected to a modification treatment according to one of the known methods. 2. The method according to p. The method of claim 1, wherein a slag is applied to the surface of the liquid metal and the liquid metal is subjected to additional treatment under a plasma reheating slag.