DE1238221B - Nitrogen-containing master alloys for steel - Google Patents

Description

GERMAN WTWWt PATENT OFFICE

EDITORIAL

German class: 40 b -31/00

Number: 1 238 221

File number: S 95088 VI a / 40 b

1 238 221 filing date: January 21, 1965

Opened on: April 6, 1967

The invention relates to alloys that are used to deliver precisely metered, uniform amounts of nitrogen into the Introduce steel bath. It is known that during the mining of mild steel and iron the Metal is loaded with oxygen in inverse proportion to the carbon content and that the simultaneous The presence of oxygen and carbon leads to the formation of carbon oxide, which is deposited.

It is also known that the evolution of gas can be mitigated or even suppressed if the oxygen is replaced by a more powerful reducing agent than carbon, such as silicon or aluminum, binds. It is thus possible to control the development of gas until one is semi-calmed or receives killed steels.

This phenomenon occurs regardless of the mode of operation and is also present in the more recent smelting processes with pure oxygen. However, while the steels obtained is heavily loaded in the older smelting with nitrogen, whose excess is sometimes troublesome to have the steels obtained by the working with pure oxygen method generally have a low nitrogen content of less than 0.005%, namely less than 0.002 ° / _0th However, this is not always an advantage. For example, in the case of certain types of fluvial iron which are used for the production of tinplate, which must have a certain rigidity, it is expedient if the nitrogen content is above 0.010%.

It is known to introduce this nitrogen through various nitrated products. For example, was suggested the use of calcium cyanamide. However, this has the disadvantage that it is in the heat in the presence of iron, alkali carbonates and hydrogen (which are often present in the slag) partially converted into hydrocyanic acid and cyanide, which poses great danger to the personnel result. Furthermore, with calcium cyanamide, the nitrogen uptake is relatively low, namely 10 to 40%, and especially very irregular from one casting to the other.

In order to avoid these disadvantages and to eliminate the dangers of calcium cyanamide, it is also known nitrated ferro-alloys, in particular nitrated ferro-manganese, to use. These alloys are always with excellent nitrogen uptakes in the extraction of stainless steels or nitrogen-containing special steels are used.

It is true that the nitrogen intake that are achieved with mild steel ■ and fluent iron when using nitrided ferro alloys more evenly than other nitrogen-containing alloys that have already been proposed Nitrogen-containing master alloys for steel

Applicant:

Societe d ^ ectro-Chirnie, d'Electro-Metallurgie et des Acieries Electriques d'Ugine, Paris

Representative:

Dr. HG Eggert, patent attorney,
Cologne-Lindenthal, Peter-Kintgen-Str. 2

Named as inventor:
Francois Danis, Annecy;
Raymond Cloppet,

Jean Montanteme, Le Giffre, Haute Savoie
(France)

Claimed priority:

France January 22, 1964 (961173)

Products, however, their value is not always high, especially in the case of unskilled steels. This appearance was explained, among other things, by the fact that the oxygen dissolved in the steel forms an adsorption layer, which hinders the dissolution of nitrogen in iron.

One could assume that this adverse effect of the gas layer by introducing the nitrogen in the form of a combination with a strong reducing agent such as aluminum. the Experience has taught that aluminum nitride is unsatisfactory: because of its poorness Weight it floats on the surface of the metal. It] is not wetted by the molten steel and remains more or less encased in slag. This results in extremely small and very irregular Nitrogen uptakes.

It has now surprisingly been found that when aluminum is combined with manganese in an alloy, a very good nitriding of this alloy regardless of its carbon content is possible and that the rate of dissolution of these nitrided alloys in the steel melt is very high and very even

709 548/320

Claims (4)

Enables the addition of nitrogen with very high intake quantities. The invention thus relates to 1. complex alloys containing manganese, aluminum and nitrogen at the same time, and 2. their use for the nitriding of steel in the molten and calmed, semi-calmed steel or unsettled state regardless of the mode of operation and even for nitration of molten steels in welding or in aluminothermics. The alloys according to the invention are complex alloys which contain the following components: Mn 40 to 99% Al 0.5 to 10% N ₂ 0.5 to 10% C Obis 8% Fe any remainder They can also contain other constituents or impurities commonly found in engineering manganese alloys. These alloys are relatively dense. They are ^a 5 molten steel in the normal recovery methods wetted by and is easily soluble. Their melting point is well below the melting point of steel. The presence of the aluminum also facilitates the dissolution of the nitrogen in the steel and reduces the nitrogen losses during this dissolution. The alloys according to the invention can be produced by the classical methods. she are in homogeneous form as pieces or crushed or sintered either in the furnace before tapping or in the tapping channel, in the pouring funnel or in the ladle before or during the pouring. The amount of nitrogen found in the steel or iron when introduced with the aid of the invention Alloys is very high and remarkably uniform under similar working conditions. Of the Alloys according to the invention are particularly advantageous if they have the following composition: Mn 70 to 90 ° / o Al 2 to 4% N ₂ 4 to 6% C Obis 3 ° / o Si 0 to 2% Fe rest 15th 45 50 example 1 An alloy of the following composition was made: Mn 85.14% Al 3.63% N ₂ 5.70% C 0.61% Si 0.93% Fe rest A non-killed steel was nitrided with this alloy, which should contain the following components: C 0.08 to 0.10% Mn 0.40 to 0.50% N ₂ 0.010 to 0.012% For this purpose, 1.7 kg of the aforementioned nitrided alloy were poured into the steel melt per ton of liquid steel, in sintered and crushed form in metal cans that were dimensioned so that they contained 500 g of nitrogen. At the same time the normal complementary additives were added added to ferromanganese. The starting steel contained C 0.009% Mn 0.17% N ₂ 0.0028% The final analysis resulted in the following values: C 0.095% Mn 0.45% N ₂ 0.0107% This corresponds to a nitrogen uptake of 81%. B e i s ρ i e 1 2 A killed steel was nitrided, whereby a steel with the following proportions was desired: C 0.10 to 0.13% Mn 1.40 to 1.60% Si 0.30 to 0.50% Al 0.030 to 0.040% N ₂ 0.020 to 0.025% For this purpose, 4 kg of the above-mentioned nitrided alloy were added to the steel to be nitrided Form as in example 1 at the same time with the additional additions of reduced ferromanganese, silicon and aluminum added. The starting melt of the steel contained: C 0.10% Mn 0.19% Si 0.07% Al 0% N ₂ 0.002% The final analysis resulted in the following values: C 0.13% Mn 1.54% Si 0.40% Al 0.035% N ₂ 0.022% This corresponds to a nitrogen uptake of 89%. Patent claims: 1. Nitrogen-containing master alloys for steel, consisting of 40 to 99% manganese, 0.5 to 10% aluminum, 0.5 to 10% nitrogen, Up to 8% carbon, the remainder iron. 65 2. master alloys according to claim 1, consisting of 70 to 90% manganese, 2 to 4% aluminum, _r . 4 to 6% nitrogen,
0 to 3% carbon, 0 to 2% silicon,
Remainder iron. 3. master alloys according to claims 1 and 2, characterized in that they are the usual Contain impurities in technical manganese alloys. 4. Use of master alloys according to Claims 1 to 5 for introducing nitrogen in calmed, semi-calmed or unkilled steel melts and in molten steels during welding and with aluminum kinothermics. 709 548/320 3.67 © BundesdruckereiBerlin