DE1433565A1 - Process and manufacture of cast iron using improved pig iron - Google Patents

Description

Method of making cast iron using improved cast iron

The invention relates to the manufacture of pig iron for remelting purposes. Contains normal foundry iron Carbon in the form of graphite or free carbide, v / although the greater part belongs to the graphitic type. The graphite consists of large columnar or horn-like Particles of cooking foam or primary graphite together with coarse secondary graphite in an irregular distribution.

For the ASiM-Ai ¹ S graphite classifieation, this type C graphite is called »

It is a concern of the invention to provide iron with compact or nodular graphite and significantly reduced proportions to produce stemmed cooking foam. In addition, the iron should be largely "exempted from elements that the formation of Favor flake graphite. After all, the iron should be the Good physical and mechanical properties to inherit. Details can be found in the following description and drawings.

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- 1 shows the typical Boheisen® cooking foam and lamellar graphite iron in a 100-faclier enlargement _. -,: _; -. ·.

Mg. 2 shows, on the same scale, one produced according to the invention Sahe iron with laiot-shaped and compact Lamellar graphite}

3 shows iron remelted from ordinary pig iron, cf. the zones with cooking foam graphite , ASP type Oj. . '

Fig. 4 shows a cast iron produced according to the invention remelted iron. You can see the practical freedom of cooking foam graphite and the improved Distribution of flake graphite, ASF type A.

It is well known that foundry iron always has a large share in the charging of a furnace for the production of Had iron castings. However, the proportion, in particular with consideration of the price ratio Eoheisen to cast and steel scrap changed within wide limits In most types of cast iron, however, there is a minimum salary Eoheisen has always been desirable, mainly because its chemical composition is known and certain advantageous Properties are transferred to the remelting. The proportion of pig iron in an average kanii '' between $ 10 and $ 100} but most of the time it is " about $ 25 to $ 40.

It is known in specialist circles that the type of ■■ -. Eoheisens. has a great influence on the second melt product. This property, often called "inheritance", has often been attributed to pig iron that is melted in a special iron, e.g. as charcoal iron, or that contains trace elements such as vanadium or titanium *

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But regardless of the issue, whether such statements are correct in detail, it is a certain knowledge that the type of pig iron has a considerable influence on the metallurgical and foundry-related behavior of the remelting produced with this pig iron _e

For several years, especially since the carburizing of Spheroidal graphite and the knowledge that small lengths of certain elements exert a great influence on the graphite in cast iron, the Ivletallurgians have in stone Extensive efforts to produce types of pig iron, which contain trace elements in small amounts, which the metallurgy of the Change end products decisively "

It has also been recognized that the size, shape and arrangement of the Graphite in pig iron that determines properties in the remelting process In general, a pig iron with large dimensions is used coarse lanellcing graphite and sticky cooking foam a cast iron with similar graphite, while pig iron with finer graphite flakes and less Gurschaum cast iron with linen jrapliitlL.ulichen brings out *

i) s: -ch-jint no jroliur difference between the Jießerei-Koheiö'jn to be used, you may need to see the length ratio; deo free carbides to graphite, co that an iiolieisen mottled or partially white 3oin kai in and then a cast iron with improved graphite delivers depending on the chemical composition and the melting and treatment process.

The Eoheisen part of a genus is usually also used. the purpose of introducing silicon into the melt, with usually such amounts of silicon are present in the Holieisen that the Bisen is completely gray

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I am completely gray iron but only give it to the metallurgist little possibility of the graphite structure of cast iron too to enhance·

It is well known that not all of them are in the pig iron during the smelting process occurring graphite flakes destroyed. Therefore, a pig iron with coarse graphite will produce an iron with a lower shock value than a pig iron with fine graphite because of the graphite more difficult to bring completely into solution and unresolved Graphite particles act as nuclei for the precipitation of further graphite from the melt.

It has now been found that a pig iron, which graphite in node form or partially in node form and little or no Contains cooking foam or primary graphite in lamellar form, when remelting cast iron with significantly improved mechanical properties Properties gives

It was also found that such pig iron is particularly suitable for the production of malleable cast iron according to the usual Process is suitable and that a malleable cast iron is obtained with a lower tendency to primary graphite in larger cast cross-sections. It can also be stated that a malleable cast iron produced according to the invention can be tempered better than malleable cast iron made with other common pig iron.

It was also found that no difficulties were encountered when using pig iron which already contains graphite in the form of nodules in the production of spheroidal graphite iron, which contains harmful elements that would otherwise be successful Prevent the graphite from being converted into the nodular form «

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The cause of the improvement of cast iron, which is produced according to the invention from improved pig iron, is not yet fully known, but it can be assumed that the improvement with the increased ability of the graphite is related to going completely into solution in the pig iron and perhaps also to the presence of a carbide metastabilizer Effect e.s in pig iron, which comes from the treatment of pig iron for the purpose of forming nodular graphite. Besides it is probable that in a pig iron already provided with spheroidal graphite all those elements are made unshädlieh, which would affect a cast iron melt in terms of graphite nodule formation, so that their influence on the Remelting is negligible.

The pig iron according to the invention can be produced in any known manner in a blast furnace or another shaft furnace or in an electric furnace. In the molten state, however, it is subjected to a treatment which converts the graphite into the form of nodules. For this treatment Oalzium can, magnesium, Oer, lithium or any other means known for this purpose means are used, and these may be added by bubbling under the '<Sohmelzenoberfläche means of inert gas, by direct surface treatment or in any other known manner.

Preference is given to the elements that are like the rare earth metals inherently the adverse influences of occasionally ' Occurring accompanying elements, * which pass from the ores when the pig iron is blown into it. So can small amounts Mischmetall (Oermischmetall) or fluoride of the rare earths used together with a reducing agent such as calcium silicide will. '|

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Thus, a coming from the blast furnace melt was, for example, untreated specimens in A, and after addition of 0.375 of a mixture fo 80 parts of calcium silicide and 20 "Jo ropes shed a ITuorids rare earths into test pieces B. A third portion of the melt was 0.75 i ° a mixture of 40 ropes of calcium silicide, 40 ropes of a magnesium-silicon alloy and 20 parts of calcium fluoride were added and test pieces 0 were poured.

rehearse

Graphite structure

tensile strenght

1 Cooking foam and coarser graphite 12th , 6 kg / mm B. compact graphite 40
Nodular graphite $ 60 i> with 50 , 6 kg / mm 0 compact graphite 50
Nodular graphite $ 50 ° / o and 47 ,8th kg / mm

Pie then resulted in operationally cast melt parts the advantages described below »

Which of the known processes for the production of graphite in the shape of a pebble "in the production of iron is also applied, it arises when remelting cast iron with special Properties even if streaky graphite occurs in the cast iron.

The invention is explained in more detail by the following examples

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example 1 1

A cupola batch of $ 50 steel scrap and $ 50 normal foundry iron had after the addition τοη $ 0.5 lumpy FeSi the composition

$ 4.20 Gesr-Carbon $ 2.40 Silicon $ 0.90 Manganese.

From this melt, 30.5 mm samples were cast with the following values:

$ 3.73 total carbon $ 1.72 silicon $ 0.70 manganese
Tensile strength 23.20 kg / mm ²

The same furnace was used with the same iron and steel scrap set continued to melt, but the pig iron had graphite in Nodular shape as a result of previous treatment with magnesium-ferrosilicon, the composition of cupola iron was:

$ 4.35 total carbon $ 2.52 silicon

$ 0.85 manganese, to which $ 0.5 lump PeSi was given.

30.5 mm cast samples showed the following values

$ 3.41 total carbon $ 1.69 silicon $ 0.74 manganese
Tensile strength 29 »53 kg / mm ² .

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The samples produced according to the invention showed a largely refined flake graphite, which is noticeable in the considerable increase in tensile strength

Example 2:

In the electric furnace v. 100 / "o pig iron was converted into a melt

4.52 ^ total carbon 1.30 ^ silicon O ₃ 35f ° Llangan 0.01 5 ^c / i sulfur

melted.

The melt was 1.5 / ° of a magnesium-Perro-silicon with 9.5 kg and 40 ^ Si added. The ones poured from it Samples showed about. 50 / i Iüiötchen- and 50> i> j? curl graphite »The composition was:

3.90 ^ 0 total carbon 2.72yo silicon 0.38> ί llangan 0.012 ^ 3chv / efel 0.030 / "b magnesium

and the ability properties were

49.6 kg / mm tensile strength 31.8 kg / mm yield point 5f ° elongation

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A second melt in the same furnace was made from 1ΌΟ? Ο Pig iron is produced, which is an additive in the blast furnace of 0.3755 * 0 of an 80:20 mixture of calcium silicide and had received rare earth chloride.

In the pig iron, about 50y ° of the graphite was in the form of nodules, the rest in the form of claws The composition was:

4.60? Ö total carbon 1.38 '/ i silicon
O, 28i? O manganese

sulfur

This melt was made of $ 1.5 magnesium perro-silicon 9f5 kg and .40 $ Si added »This second adding one Spherolite former was less than when the pig iron contained graphite of the type Ö AlS and not in the blast furnace would have been pretreated with a rod of a spherulite maker.

The cast samples showed more than 90% graphite and nodules

> i total carbon 2.65> ό silicon
0.29 ^c / £ manganese.
0.01 ΐ; ό sulfur
0.028 '/ ό magnesium

The physical properties were there

Tensile strength 57.6 kg / mm ² yield point 33.8 kg / mm elongation 17, (

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The example clearly shows that Tdei equality of all other influencing variables the pig iron, in which previously nodular graphite was produced, was easier to provide after remelting with nodular graphite than normal pig iron same composition

The method according to the invention and also according to the examples can be carried out in such a way that the starting point is a liquid pig iron which, cast without treatment, would essentially ^{contain the graphite as type C Ai 1} S, i.e. would contain stalky Grarschaumgraph.it, whereupon A first effective partial amount of a spheroidizing agent is added, poured and cooled so that the iron has at least some graphite in the form of nodules and "practically no cooking foam. Such iron is now charged in proportions of 10 to 100 $, the batch is melted, and this Melt the second portion of the spheroidizing agent added. The amount is less than if no first addition has taken place · Finally, it is poured into castings that contain the graphite in the form of nodules *

According to the invention, however, a pig iron can also be used, v / elches after the first addition of the spheroidizing agent still has cooking foam «With such an iron, the Uuischmelzen also achieved a better iron than with untreated iron first melt. The cast iron shows J-uin £ .ber also! "Curly graphite *

Patent claims:

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Claims (3)

Claims 1) Process for the production of cast iron with spheroidal graphite or nodular graphite, characterized in that one of Bisen went out, the casting of which was essentially Graphite of type G APS with stalky cooking foam would contain ι and that this Uisenschmelze a first effective Amount of an agent leading to spheroidal graphite was added receives, then poured and cooled, and that this pig iron, which at least partially Contains spheroidal graphite or lump graphite and no cooking foam, added to a furnace charge, then this charge is melted and then with a second addition of a ball or Nodular graphite causing agent added and finally to cast iron with spheroidal or nodular graphite potted v / ird, the second addition being kept lower can be as if the base iron (with 0 APS graphite) has not been treated with spheroidal graphite-producing agent were. 2) _ Method according to claim 1, characterized in that the starting iron in proportions of 10 to 100 $ the. Remelting batch is added 3) Method according to claim 1 or 2, characterized in that a pig iron is used which is cast untreated Type 0 APS graphite contains T.lirde, im Remelting iron, however, causes type A AP3 graphite, whereupon the second addition of spheroidal graphite-producing Medium flake graphite caused after pouring. 809809/0476