DE1270057B - Process for melting gray-hardening cast iron - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C 21 c

German class: 18 b -1/08

Number: 1270 057

File number: P 12 70 057.1-24

Filing date: August 14, 1961

Opening day: June 12, 1968

For the production of gray-hardening cast iron, it is common to use an acid-lined cupola To feed pig iron, steel scrap, fluxes and fuel such as coke. In addition, various Alloy additives also in the form of briquettes to adjust the composition and Properties of the gray-solidifying cast iron to be melted added. The proportions of the various Ingredients in use depend to a large extent on the composition and the desired ones Properties of the metal to be produced. In addition, when dimensioning the additions the losses of delivered elements are taken into account.

The two most influential elements in terms of the physical and mechanical properties of gray cast iron are carbon and silicon. When operating acid lined cupolas the carbon content depends primarily on the amount of carbon that is with the metal components is added to the mixture. Since at least 90% of the coke is consumed during combustion, it only introduces a very small amount of carbon. Silicon is commonly used in Ferrosilicon form added to compensate for the lack of silicon in steel scrap.

Since the carbon for the gray-hardening cast iron mainly consists of the metal components of the When used, the carbon content of the gray-solidifying cast iron is increased by changing the Ratio of pig iron to scrap steel in use varies. The silicon content in the product is determined primarily influences the relationship between graphite and cementite in gray-hardening cast iron however, the total carbon content of those normally present in this iron only marginally Areas.

It would be desirable to consider the ratio of pig iron to scrap steel when operating cupolas could change to take advantage of changes in the price of both materials and In addition, the availability of the input materials must be taken into account. However, as the main source of carbon for the finished product comes from the carbon content of the pig iron and steel scrap, is the ratio of pig iron to scrap steel for the manufacture of any given type of gray cast iron within fairly narrow limits.

The invention relates to a method for melting gray-solidifying cast iron in an acid-lined cupola made of pig iron and steel scrap with the addition of silicon-containing briquettes, wel method for melting
gray cast iron

Applicant:

Union Carbide Corporation,

New York, N.Y. (V. St. A.)

Representative:

Dipl.-Chem. Dr. H.-G. Eggert, patent attorney,
5000 Cologne-Lindenthal, Peter-Kintgen-Str. 2

Named as inventor:

Frederick Albert Stephens, Lewiston, NY;
Oscar George Woodpecker, Allison Park, Pa. (V. St. A.)

Claimed priority:

V. St. v. America of August 29, 1960 (52 339)

Ches is characterized in that pig iron and steel scrap are used in such a ratio will be that they contain less than the amount of carbon required for the desired gray solid cast iron supply and that the missing carbon is introduced in the form of silicon-containing briquettes, which also contain 12 to 35 percent by weight carbon and in which the ratio silicon to Carbon ranges from 1: 1 to 3: 1.

The insert consisting of pig iron, steel scrap and briquettes is then delivered in the sour Cupola melted by conventional methods to produce the desired gray-solidifying cast iron. The briquettes are added to the cupola insert in such an amount that with them the missing Carbon and any desired amounts of manganese and / or chromium can be added.

The briquettes can be made from elemental metals, but are most conveniently made made of ferro-alloys. The carbon can be added in any form, but is preferred added in the form of natural or synthetic graphite. Typical alloys that are Suitable for the production of the briquettes are ferrochrome-silicon-ferrosilicon-chromium, Silicon manganese, ferromanganese, ferrosilicon, and high carbon ferrochrome. The carbon-rich ferrous

809 559/316

chromium is preferably used only for minor compositional corrections. as well can also use elemental silicon as needed for making minor compositional corrections to be needed. The briquette components are preferably available in two different size ranges used: 9 to 4 mm and 4 mm and smaller. The two different sized materials can be mixed as required to regulate the density of the briquette, so that briquettes of Standard size and standard weight as well as various compositions, the total mentioned Capture areas, can be produced. An inorganic pebble-like material can be used as the binder be used. The preferred binder is Portland cement, both the standard type as well as the fast curing type. The briquettes are made in the usual way by adding the ingredients mixed in the desired quantities, mixed with water and pressed in a briquette press the. No special methods need to be used or special precautionary measures observed to become.

A typical composition of the briquettes is 25 to 50 percent by weight silicon, 12 to 35 percent by weight Carbon, 0 to 25 weight percent chromium, 0 to 10 weight percent manganese, 5 to 20 percent by weight inorganic, silica-containing binder, the remainder being iron and impurities.

To illustrate the invention, hard, medium and soft gray cast iron is made using first the usual procedures and then the procedure according to of the invention were applied. The experiments are described in the following examples.

example 1

A cupola furnace was used to produce hard, gray-solidifying cast iron by known processes with 421.5 kg of tempered iron, 435.5 kg of steel scrap, 43 kg of ferrosilicon briquettes with 6.35 kg of cement charged as a binding agent (total input 900 kg). The ferrosilicon briquettes had a target composition of 40.0 percent by weight silicon, 9.0 percent by weight manganese, 8.6 percent by weight Chromium, the rest iron and binding agent. The insert was melted in the cupola furnace. In which on this Hard gray cast iron produced in this manner remains 80% silicon, 95.5% carbon 100% chromium and 90% manganese in the melt.

According to the method according to the invention, a cupola insert was made to the same hard Manufacture gray solid cast iron as above, however, a ratio of pig iron to scrap steel was used from a little over 0.26: 1 versus 0.96: 1 in previous case applied. The cupola insert consisted of 173.8 kg of tempered iron, 653 kg of steel scrap, 72 kg of the briquettes according to the invention with 5.9 kg of cement as a binder. In the, according to the In the hard gray cast iron manufactured in accordance with the invention, 80% of silicon and 85.5% of carbon remain 100% chromium and 95% manganese in the melt. Those made by the two processes Cast iron products had the same quality and properties. Changes to the melt flow were not required with the other ratio of pig iron to scrap steel.

Example 2

The procedure described in Example 1 was repeated, the inserts of the preparation of medium gray cast iron. The first use that melted in the usual way consisted of 436.5 kg of tempered iron, 381 kg of scrap steel, 52 kg of ferro-silicon briquettes with 7.7 kg of cement as a binding agent. After correction to account for losses to the slag the insert had a target size of 862 kg. The ferrosilicon briquettes had the following nominal composition: 36.4 weight percent silicon, zero carbon, 3.3 weight percent chromium, 1.8 weight percent Manganese, the rest iron and binding agent.

The second insert, assembled according to the invention, consisted of 117.1 kg of tempered iron, 662 kg Steel scrap, 90.1 kg of the iron-silicon briquettes according to the invention with 8.1 kg of cement as a binder. The target size of the insert after correction for losses to the slag was also here 862 kg.

The new iron-silicon briquettes had the following target composition: 30.8 percent by weight silicon, 23.0 percent by weight carbon, 1.8 percent by weight chromium, 3.4 percent by weight manganese, remainder Iron and binders. The silicon-to-carbon ratio was 1.34.

Each of the inserts was placed in an acidic cupola furnace in two separate operations and melted in it. Again, completely comparable products were made without changing the Melting control received, although the pig iron / steel scrap ratio in the first case was 1.17 and in the second case 0.18. In both cases it was 83% silicon, 100% chromium and 95% manganese recovered. The carbon became 96% for the standard use and for the use compiled according to the invention 84.5% recovered.

Example 3

The procedure was as in Example 1, the inserts on the production of soft gray Cast iron were turned off. The first insert, composed according to normal practice, contained 571 kg tempered iron, 254 kg steel scrap, 27 kg ferrosilicon briquettes with 4 kg cement as a binding agent. After correcting for losses to the slag, the nominal size of the insert was 848 kg. The ferrosilicon briquettes had the following target composition:

40.0 weight percent silicon; no carbon, chromium and manganese, the remainder iron and binders.

The second insert according to the invention contained 324.5 kg of malleable iron, 472 kg of steel scrap,

55.1 kg of the new iron-silicon briquettes according to the invention with 4.5 kg of cement as a binder. Even here the target size of the stake after adjustment to take account of losses to the Slag 848 kg. The new iron-silicon briquettes had the following nominal composition: silicon 31.0 percent by weight, carbon 23.4 percent by weight, chromium and manganese zero, the remainder iron and Binder. Its silicon-to-carbon ratio was 1.33.

Each insert was placed in a cupola and melted therein. Again they were comparable Products obtained without changing the smelting process, although the pig iron / steel scrap ratio

nis was 2.25 in the first mission and 0.69 in the second mission. The silicon was increasing in each case 84% recovered. The carbon became 87.5 for the standard insert and that of the invention 83.5% of the combined use was recovered.

From the examples it can be seen that the use of the briquettes according to the invention Ratio of pig iron to scrap steel in the inserts changed within a large margin can be, so that there is greater freedom of movement in the choice of starting materials.

Claims (2)

Patent claims: 1. Process for melting gray-solidifying cast iron in an acid-lined cupola furnace made of pig iron and steel scrap with the addition of silicon-containing briquettes, characterized in that that pig iron and steel scrap are used in such a ratio that ao they are less than the amount of carbon required for the desired gray cast iron supply and that the missing carbon is introduced in the form of silicon-containing briquettes, the also contain 12 to 35 percent by weight carbon and in which the ratio is silicon to carbon is in the range of 1: 1 to 3: 1. 2. The method according to claim 1, characterized in that that the briquettes consist of 25 to 50 percent by weight silicon, 12 to 35 percent by weight Graphite, 0 to 25 weight percent chromium, 0 to 10 weight percent manganese, 5 to 20 weight percent an inorganic silica-containing binder, in particular Portland cement, remainder Iron and impurities exist, with the ratio of silicon to graphite being 1: 1 to 3: 1 amounts to. Considered publications:
Austrian patent specification No. 149 667. 809 559/316 5.68 © Bundesdruckerei Berlin