DE2223974C3 - Process and melting furnace for the production of a deoxidation and steel refinement coating - Google Patents

Description

The invention relates to the production of a complex deoxidizing alloy or deoxidizing alloy Multi-component alloy for steel finishing and a device for carrying out the same. In comparison to the known alloys, the new alloy produced according to the invention affects the mechanical properties of steel more favorable.

To the deoxidizing and refining alloys used in the manufacture of alloyed steels more and more diverse demands are made. One of the basic requirements concerns the grain size of the reacting substances of the alloy or their specific surface from which the speed of the reduction reactions taking place in steel finishing, primarily the the diffusion processes, depends to a large extent. In the process of making such alloys are fine-grain mixture components in a finely ground state, with or without different Binding agents can be briquetted or pelletized to prevent premature volatilization of the reducing agents Used to prevent alloy from furnace. The object of the invention is to reduce the grinding of the Alloy components up to the appropriate fineness and still those in the manufacture of the alloys to avoid the costly briquetting of the finely ground materials.

The second requirement for complex alloys consists in the fact that the individual mixture components generally in the form of chromic acid compounds should be present and thus the oxides formed from them already at the moment their formation with one another to form complex compounds whose melting point rclaii \ is low and thus a good coagulation siähiiikeit have, react. In addition to the good deoxidizing alloys, the complex alloys used can be used and possibly also other desulphurising effects from the point of view of the alloys Have properties. One such advantageous property is that the alloys are more stable to form Nitrides are suitable. Furthermore, the invention is based on the object of such an alloy, which not only has a good deoxidizing and desulfurizing effect, but also to form more stable Nitride helps provide.

The use of complex deoxidizing ur.H steel refining multi-component alloys is "* dealt with in the following specialist books: Helmut Knüppel, Deoxidation and Vacuum Treatment von Stahlschmelzen, Vol. I, 1970, Chapter 2 -V J.Javojszkij, Theory of Steel Production, Leipzig, 1969, p. 456..

Another important property of the alloys is the specific weight, since deoxidizing agents are used low specific gravity come into play primarily on the surface of the bath and so on the burn-off losses increase and the efficiency of the deoxidizer compared to deoxidizer with the same deoxidation capacity, but a higher specific weight, is lower. Furthermore, the object of the invention is to provide an alloy which also with regard to the specific Weight to meet the requirements to be generated. . .

In the manufacture of the alloy, the accessibility and cost of the mixture components play a role important role, since in steel production the alloys the production costs extraordinarily can increase. An important technical task is therefore to provide an alloy with such an alloy Composition, which gives an optimal effect and at the same time using a light accessible and modified starting material with only a few surcharges. According to the invention the latter requirement was met to a large extent and generation costs were reduced aimed at the alloy.

In the manufacture of the alloys, an important requirement is that the production in the present sjebräuchlichen systems can be done, since in the case of the need for new systems, the investment costs greatly increase the cost of producing the alloy. The inventively provided Alloy can be used in the melting furnace usually used for the production of ferroalloys are produced, so investment costs are not to be taken into account in the production of the alloy draw.

The above objects have been achieved according to the invention.

The subject of the invention is a process for the production of a deoxidation and steel refining alloy, which is characterized in that about 15 to 25 percent by weight volatile Substances, 15 to 25 percent by weight bound carbon and 2 to 6 percent by weight sulfur containing coal rock with an ash volume of 40 to 50 percent by weight and a Calorific value of 1500 to 2000 kcal / kg for a carbon-containing alloy, consisting of 25 to 50 percent by weight Silicon, 10 to 40 percent by weight aluminum. 2 to 10 percent by weight calcium,?

up to 2.5 percent by weight titanium, the remainder iron and manufacturing-related Impurities, and possibly traces of vanadium and boron, is melted.

Under bound coal is that after deducting the ashes, moisture and volatile components remaining part of the coal to understand.

Bound coal = 100 - (moisture in percent by weight -f ash in percent by weight + volatile components in percent by weight)

Esteines is in the labeling of a Kohleneben- • άιτ sulfur indicated separately, then in the calculation of the bound carbon, the sulfur must be of the volatile components are added to the fraction.

The starting material of the manufactured according to the invention Alloy therefore already contains the necessary for the reduction processes even in fine distribution Carbon.

According to one embodiment of the invention, the inventive method is applied to the production an above alloy, but in which the sum of the aluminum and silicon content is at least 55 percent by weight is applied.

If necessary, additives, preferably waste products or oxides, can cause the Alloy composition within the specified limits when using one and the same starting material can be achieved.

The invention also relates to a melting furnace for carrying out the method according to the invention, which is characterized in that it has a shaft for the simultaneous discharge of the combustion gases and for preheating and at least partially Has degassing of the insert

The complex deoxidation alloy and steel refining alloy produced according to the invention are combined the advantages of the well-known two-component deoxidizer, like ferrosilicon, Silici'.m-aluminum, Ferrotitanium and silicon-manganese, and also has an additional beneficial effect on the final oxygen content of the steel as well as the type and amount of metallic inclusions and thus the mechanical ones Properties of steel. The beneficial effects and properties of the alloy are in are explained individually using numerical values in the example below.

Another advantage of the invention is that the complex deoxidation and steel finishing alloys manufactured in the electric furnaces commonly used for the production of ferro-alloys without interruption of production, for example from the production of ferrosilicon for the production of the complex deoxidation and steel refining alloys to be obtained according to the invention can be passed over. In the case of the electric furnaces commonly used for the production of ferro-alloys, the Combustion gases formed in the course of the reduction processes, advantageously through a charging shaft, in which the charge while it is in countercurrent to the combustion tanks after sinks at the bottom, is preheated and partially degassed, discharged.

The invention is illustrated by the following non-limiting examples explained.

example

In order to produce the alloy, large quantities of those found in coal mines were used: " and carbon-containing secondary rocks selected from the following composition:

Weight percent

Humidity (air dry) 8.10

Ashes 48.96

Volatile components 19.70

Bound carbon 20.24

Sulfur 3.99

Composition of the ash residue

SiO., 37.31

A1., Austria ₃ 21.83

FcO ₃ 8.90

CaO 19.19

TiO, 1.62

V..O, 2.27

MgO 2.97

B..O, 3.28

MnO 0.14

P ₂ O ₅ 11.05

The rock of the composition above was melted in an electric arc furnace to produce ferro-alloys. There The fine distribution of carbon in the rock was sufficient to meet the need for reducing agents to cover, it was not necessary to introduce a separate carbon carrier into the mixture, so that the production without any / uschkui-ioif was made. The alloy was tapped every two hours when the furnace was in operation without any problems.

The following is the average composition added to the alloy obtained during tapping:

Si 37.8 percent by weight

Fe 31.8 percent by weight

Al 21.7 percent by weight

About 5.2 percent by weight

Ti 1.5 percent by weight

Mn 0.1 2 percent by weight

Mg 0.7 percent by weight

C G 03 percent by weight

S 0.03 percent by weight

O 0.0025 weight percent

H 50 Ncm ³ M 00 g

fs 0. (11 (jew'iditspM.veni

With the alloy obtained in this way, winds in one 15 t electric arc furnace for steel production i-iiu Test batch produced. For 15t of steel, kg of the alloy were used, i.e. 5.3 kg per ton. The alloy was poured into the kettle and the Batch abandoned. In the following table i is the chemical composition of the steel \ or α-. ■ ··. Racking and indicated during the casting.

Table 1

Chemical composition of steel

Alloy components Before tapping the steel

After racking and the
Melting the alloy

Mn
Ni
Cr

Si
Al
Ti
O
N
H

0.18 percent by weight 1.38 percent by weight 1.23 percent by weight 0.08 percent by weight

0.22 percent by weight of 0.00 percent by weight of 0.00 percent by weight 0.0097 0.0061 percent by weight percent by weight of 9 Ncm ^3/100 g

0.18 percent by weight
1.40 percent by weight
1.22 percent by weight
0.12 percent by weight

0.42 percent by weight
0.05 percent by weight
0.01 percent by weight
0.0063 weight percent
0.0087 weight percent
8.5 Ncm / 100 {;

The following degrees of utilization can be derived from the changes in the composition of the steel:

Si usage around 100%

Al usage around 50%

Ti usage around 100%

The Al content of the alloy could be increased to a value of 25 to 40 percent by weight by adding more than 40 percent by weight of Al ₂ O ₃ rock or in one stage with the aid of metal scrap containing Al.

The total oxygen content decreased from 0.0097 percent by weight to 0.0063 percent by weight, and the hydrogen content also decreased, so the steel was not contaminated by the alloy. The nitrogen content was increased somewhat, in part as a result of the alloying material introduced nitrogen, which because of the refining effect of the aluminum and titanium nitrides

25 is part. ^{Bars with a cross section of 100 mm 2 were} forged from the upper, middle and lower parts of one of the 51 heavy forging blocks cast from the batch and heat-treated for the purpose of investigating the mechanical properties.

The mechanical properties are summarized in Table 2 below; in this they have Symbols have the following meanings

ob = tensile strength,

fTf - yield point,

δ = elongation,

.4 k = notched impact strength.

Table 2

Mechanical properties of the test batch

Position of the test bar Normal annealing 960 ° C, air 60O ⁰¹ C, oil

in the block _{σΒ in Of jn (5 jn Ak m Πβ in}

kp / mm ¹ "/" % mkp / mm ^! kp / mm ^s

Age hardening 88O ⁰ C, oil 650 ⁰ C, oil
CTr in (5 in

mkp / cm ^s

upper part
of the block 59.9 40.7 28 19.0 59.9 45.9 26th 25.0 Middle part
of the block 62.4 43.3 28 22.5 59.7 46.4 29 26.5 Lower part
of the block 59.9 43.3 28 21.5 58.6 44.5 28 26.0

For the steels used in chemical apparatus construction, a notched impact strength of at least 2.8 mkp / cm ² at -40 ° C is prescribed. The notched impact strength of the refined with the alloy samples was at the temperatures of +20 ⁰ C, 0 ° C, -20 ° C, -40 C ^{0 0} C and -6O determined at three impact bars; The figure shows the mean values of the notched impact strengths obtained in each of three tests. The diagram illustrates the dependence of the notched impact strength on the temperature and the excellent cold resistance of the steel batch. Mκ mkg / cm ¹ «means the specific impact strength, measured with a standard-compliant test rod with a V-notch, expressed in mkg / cm ² .

A denotes tempered, B normalized, C

ί>

Tempered and aged and D normalized and aged and not aging and an increased yield strength filtered sample bars. forged chemical apparatus construction - From the result of the experiment the conclusion 5.3 kg of the conclusion obtained according to the invention can be drawn that with a steel for plexing alloy per ton of steel a better result for even at -4O ⁰ C is not exert a brittle 5 kung than, for example

4.5 kg / t SiZr (40 percent by weight Si and 23 percent by weight Zr) j 1.4 kg / t Al
or

3.0 kg / t FeSi (75 percent by weight Si) + 0.8 kg / t Al - (- 3.0 kg / t FeTi (32 percent by weight Ti)

The advantageous properties of the alloy used for the test batch are primarily that ascribing good utilization of the elements, d. H. the fact that in addition to the deoxidizing elements Si and Ca, the also deoxidizing but also nitrogen-binding elements Al and Ti, practically come into effect without loss.

1 sheet of drawings

Claims (3)

Patent claims: 1. Process for the production of a deoxidation and steel finishing alloy, characterized in that about 15 to 25 percent by weight of volatile substances, 15 to Containing 25 percent by weight bound carbon and 2 to 6 percent by weight sulfur Coal rock with an ash content of 40 to 50 percent by weight and a calorific value from 1500 to 2000 kcal / kg to a carbonaceous alloy consisting of 25 to 50 percent by weight Silicon, 10 to 40 percent by weight aluminum, 2 to 10 percent by weight calcium, 0.5 to 2.5 percent by weight titanium, the remainder ice; n and production-related impurities, and optionally Vanadium and boron in traces, melts. 2. Application of the method according to claim 1 to the production of an alloy according to claim 1, but in which the sum of the aluminum and silicon content is at least 55 percent by weight amounts to. 3. Melting furnace for performing the method according to claim 1, characterized in that that the furnace has a shaft for the simultaneous discharge of the combustion gases and for preheating and at least partially degassing the insert.