GB2045805A

GB2045805A - Alloying of cast iron

Info

Publication number: GB2045805A
Application number: GB7911505A
Authority: GB
Original assignee: Frank and Schulte GmbH
Current assignee: Frank and Schulte GmbH
Priority date: 1979-04-03
Filing date: 1979-04-03
Publication date: 1980-11-05
Also published as: GB2045805B

Abstract

Ferromanganese carbide is-used as the manganese carrier and silicon carbide as the silicon carrier in an alloying carrier for charging cupola furnaces in the form of briquettes bonded with cement and having the following composition by weight. 8 - 40% Mn 9 - 22% C 2 - 9% Fe 18 - 45% Si 15 - 30% Portland cement 4 - 8%H2O chemically bonded 2 - 7% remaining constituents. n

Description

SPECIFICATION Alloy The invention relates to alloy carriers for charging cupola furnaces in the form of briquettes bonded with cement and containing the alloying materials manganese and silicon. Known alloy carriers of this type contain the silicon in the form of ferrosilicon and the manganese in the form of ferromanganese. If the manganese alloying material is to disintegrate rapidly and be evenly distributed within the melt, the manganese carrier used in the known alloy carrier must be high-grade low-carbon ferromanganese of refined ferromanganese quality (carbon content 0.5 to 2%) or over-refined ferromanganese quality (carbon content 0.05 to 0.5%). All percentages throughout the specification are on a weight basis.

Ferromanganese carbide quality (carbon content 6 to 8%), which is far cheaper, cannot be used since such a high-carbon ferromanganese contains the manganese largely in the form of not readily decomposed carbides, i.e. in an unreactive state.

Prices for refined ferromanganese and over-refined ferromanganese grades are about 2 to 3 times higher than forferromanganese carbide grade, because of the considerably higher production costs. Apart from the extremely high price, the use of refined or over refined ferromanganese has the disadvantage that the manganese burns away relatively fiercely, particularly in hot-blast cupola furnaces. The burning takes place even in the upper part of the shaft of the furnace, where there are temperatures of 800 to 115000 and preponderantly oxidising conditions, so that the low-carbon ferromanganese is oxidised by virtue of its high affinity to oxygen.

Thus it would be desirable to make the alloy carrier of the above type considerably cheaper and to improve it in respect of fire loss.

The present invention provides alloying carriers for charging cupola furnaces in the form of briquettes bonded with cement and containing the alloying materials manganese, in the form of ferromanganese, and silicon, and having the following composition by weight.

8 - 40%Mn 9 - 22%C 2 - 9% Fe 18 - 45% Si 15 - 30% Portland cement 4 - 8% H2O chemically bonded 2 - 7% remaining constituents in which ferromanganese carbide is used as the manganese carrier and silicon carbide as the silicon carrier.

When the alloy carrier according to the invention is used in hot-blast cupola furnaces, oxidation of the alloying materials in the upper part of the shaft can largely be avoided. The high-carbon ferromanganese and particularly the silicon carbide are to a great extent resistant to oxidising gases. In addition, the highly resistant silicon carbide in the briquette forms a protective sheath for the ferromanganese. Above 11 50 C, i.e.

in the incipient siag zone, the ferromanganese and silicon carbide begin to break up and decompose with the disintegration of the briquette. The great heat which is liberated by oxidation of the constituents of the disintegrating silicon carbide leads to accelerated decomposition of the not-readily-decomposed carbides from the high-carbon ferromanganese, so that the manganese becomes free and fully effective at exactly the right time. The activating effect of the silicon carbide on the high carbon ferromanganese is so strong that better results, in respect of output and even distribution, can be obtained with this considerably cheaper starting material than with the expensive low-carbon grades of ferromanganese.In addition, the carbon liberated by the silicon carbide and high-carbon ferromanganese, which is in the reactive nascent state, produces lasting deoxidation of the slag. Tests have revealed a reduction in the manganese oxide and iron oxide content of the slag and cast iron and an improved yield of silicon and manganese in the cast iron.

There is also a considerable improvement in the desulphurization of the cast iron.

Two types of alloy carriers according to the invention, of the following composition, have proved particularly advantageous: Type I 30 - 40% Mn 9 - 15%C 5 - 9% Fe 18 - 25% Si from SiC 15 - 20% Portland cement 4 - 6% H2O chemically bonded 2 - 7% remaining constituents This is particularly suitable for alloying on cast iron with manganese and silicon and for deoxidation.

Type II 8 - 30% Mn 15 - 20%C 2 5%Fe 25 - 45% Si from SiC 20 - 30% Portland cement 5 - 8% H2O chemically bonded 2 - -7 /O remaining constituents This to a great extent avoids the formation of iron sulphide and manganese sulphide in the cast iron.

Claims

1. Alloying carriers for charging cupola furnaces in the form of briquettes bonded with cement and containing -the alloying materials manganese, in the form of ferromanganese, and silicon, and having the following compositions by weight 8 - 4p% Mn 9 - 22%C 2 - 9 h Fe 18 - 45%Si 15 - 30% Portland cement 4 - 8% H2O chemically bonded 2 - 7% remaining cpnsttuents, in which ferromanganese carbide is used as the manganese carrier and silicon carbide as the silicon carrier.

2. Alloying carriers as claimed in Claim 1 of the composition by weight: 30 -- 40%Mn 9 - 15%C 5 - 9% Fe 18 - 25% Si from SiC 15 - 20% Portland cement 4 - 6% H20 chemically bonded 2 - 7% remaining constituents.

3. Alloying carriers as claimed in Claim 1 of the composition by weight: 8 - 30% Mn 15 - 20%C 2 - -5% Fe 25 - 45% Si from SiC 20 - 30%-Portland cement 5 - 8% H2O chemically bonded 2 - 7% remaining constituents.