DE1933389B2 - PROCESS FOR FEEDING ALUMINUM IN THE PRODUCTION OF NON-AGING DEEP-DRAWING STEEL - Google Patents

Description

The invention relates to a method for supplying < viumirium in the production of non-aging Deep drawing steel and in particular a method for adding aluminum ι id nitrogen liquid steel.

The content of dissolved Al and N ₂ in the steel produced by the process according to the invention should be in the most suitable range so that the best possible deep-drawability is achieved. To achieve this, an aluminum wire with a diameter of more than 5 mm is fed _{into the liquid steel at a feed speed of more than 5 m / s and N 2} gas or nitrogen-rich argon is blown into the liquid steel, which is done through a refractory material takes place through it, which is well permeable and attached to the pouring ladle bottom.

It is known that in the manufacture of low carbon Al killed steel, either a process in which lump Al is thrown into the tap stream of liquid steel or a process in which cast Al is attached to the ladle prior to tapping is common to use. Likewise, it is common practice to increase the nitrogen content in steel by adding an Fe-Mn-N alloy to the liquid steel. In Fig. 2 shows the distribution of dissolved Al and N ₂ in the steel, as it results from the known processes mentioned above.

In general, the deep-drawability of a cold-worked steel is strongly influenced by the content of dissolved Al and N ₂ in the steel. The mutual relationships between dissolved Al and N ₂ in steel, which resulted from many experiments, are shown in FIG. 4 shown. From this it can be seen that the most suitable range, which raises the Lankford value r for deep drawability to more than 2.00, is between a content of dissolved Al of 0.020 to 0.050% and of nitrogen of 0.0045 to 0.0080% lies. A comparison of FIG. 2 with F i g. 4 shows that the range of dissolved Al and N ₂ in the known steel (FIG. 2) is far from the most suitable range (FIG. 4) for obtaining excellent deep drawability. The reason for such results is that the distribution of dissolved Al and N _{2 is} remarkably large. That is, the deep drawability. which depends on the content of dissolved Al and N ₂ and the highest frequency in FIG. 2 for a value for

ίο has dissolved Al of 0.045 and for N ₂ of 0.0038. not above that from FIG. 4 apparent Lankford value r of 1.8 or close to this value.

It has also been found that such

Procedure has the following disadvantages: There is the

is tendency to re-release of phosphorus (rephosphorization) through the slag and for a higher content of dissolved Al due to it. At the same time, the inclusions of the aluminum oxide system will float up and separate the imperfect stirring effect after deoxidizing is very poor, which leads to many mill chip defects and leads to segregation of the constituents.

These disadvantages can be eliminated by the method according to the invention in that aluminum and nitrogen are added to the liquid steel. According to the invention, the Aluminum is continuously added at high speed to the molten steel in the ladle and gaseous nitrogen blown into the liquid steel through the bottom of the ladle.

The aim of the present invention is to provide a method according to which the optimum content of dissolved Al and N ₂ as shown in FIG. 4th

shown is achieved. The process should have the lowest distribution of the contents of dissolved Al and N ₂ in the steel, and the steel produced according to the invention should be a non-aging deep-drawing steel, which allows good yield and has an excellent surface quality.

An exemplary embodiment of the present invention is illustrated with reference to the drawings.

F i g. 1 shows in a view how, according to the invention, the aluminum and the nitrogen the liquid steel added in the ladle.

F i g. Fig. 2 is a histogram showing the distribution of dissolved Al and N ₂ in steel when the aluminum and nitrogen are each added to the liquid steel by the known methods.

F i g. 3 is a histogram showing the distribution of dissolved Al and N ₂ in steel when the aluminum and nitrogen are added to the liquid steel according to the invention.

F i g. 4 shows in a diagram the change in the Lankford value r, depending on the content of dissolved Al and N ₂ .
The in F i g. 1 shows schematically how the aluminum and nitrogen are added to the liquid steel in the ladle. The steel melt, to which no aluminum has been added, is drawn off into the pouring ladle 4. Aluminum wire wound around a drum 1 is then introduced into the liquid steel by a feed device 2 via a guide 3. In this case it is necessary that aluminum wire of more than 5 mm in diameter with a speed of 5 m / s

is admitted. At the same time, gaseous nitrogen or nitrogen-rich argon is introduced into the liquid steel through refractory material with good permeability, for example through a porous stone 5. which is attached to the bottom of the ladle. blown by a cylinder 6 standing outside. The bubble lasts more than 1 minute. One can expect the liquid steel to be fully stirred as shown. As a result, the steel retains the appropriate dissolved Al and Ni contents. If the diameter of the aluminum wire is less than 5 mm and the feed speed is less than 5 m s., It is found that the added aluminum cannot reach the deep layers of the liquid steel. Is less than 1 minute, the Blaszeil for the N, gas, ^ o i ~ is the implementation of the liquid steel as well as insufficient, and the N content in the steel _r hardly increases.

The in Fig. The histogram shown in Fig. 3, which results from the data of 53 lots, relates to the present invention. The x value of dissolved Al and N ₂ is 0.0297% and 61.2 ppm, respectively. The Lankford value r, which depends on these x values, is more than 2.00, as in FIG. 4 is shown. The method according to the invention is thus far superior to the known methods in which the .x value of the dissolved Al and N _{2 is} 0.0439% or 38.2 ppm and the corresponding r value is about 1.70 in FIG. 4 is. In addition, FIG. 3 that the scattering of dissolved Al and N ₂ according to the present invention is very small.

The following examples are carried out in comparison with the known methods. The chemical The composition and process conditions are as follows:

Table I.
Chemical composition (by weight)

C. Mn P. S. N solved. Al A. 0.05 0.30 0.011 0.016 0.0037 0.028 B. 0.06 0.32 0.012 0.015 0.0034 0.057 C. 0.05 0.30 0.012 0.016 0.0039 0.041 D. 0.05 0.29 0.018 0.018 0.0056 0.034 E. 0.05 0.27 0.014 0.016 0.0063 0.026

Procedural conditions

Steel A, B and C known processes

Steel D and E according to the invention

procedure

Amount of Al added approx. 1 kg t

Feed speed .... 6ms Injected nitrogen

volume approx. 4 m ^J 100 t

Blowing time 6 minutes

Warm whale / stadium

Hand treatment temperature N30 C

Temperature in the wound state. . 520 C F. final thickness "2.S mm

Potash stage

Final thickness 0.8 mm

Annealing treatment condition 15h. at 700 C

in the chamber furnace after-treatment roller ¹ ,! . . . 0.7 ".,

The mechanical properties of the steels listed above are given in Table II.

Table II
Mechanical properties

Stretch train
firm Deh Erich-
sen- Kege! -
bowl-
-
r grain
size border speed tion Cupping value ASTM kg mm ² kg mm ² 0 -.in the mm No. A. 18.7
31.3 47.8 10.8 37.6 1.34 9.0 B. 18.4 31.0 46.5 11.0 37.8 1.44 8.6 C. 16.7 29.4 48.6 11.3 36.8 1.74 7.5 D. 15.4 28.9 50.2 11.7 36.5 1.87 7.1 E. 15.1 28.5 50.8 11.8 36.1 2.01 6.9

35

40

45 From Table II it can be seen that the steels produced according to the invention are far superior to the known steels. Based on the most suitable range of 0.020 to 0.040% dissolved Al or 50 to 70 ppm N ₂ , the proportion of dissolved Al and N ₂ achieved is approximately 95%. The method according to the invention and the steel produced by this method have the following advantages:

1. The floating and separation of inclusions of the alumina system accelerated.

2. The rephosphorization of the steel in the ladle is considerably reduced.

3. No segregation or separation of constituents can be found in the steel.

4. There is little oxidation loss of added Al through the atmosphere and the Slag before.

For this purpose 2 sheets of drawings

Claims (1)

Claim: A method for supplying aluminum in the production of non-aging deep-drawing steel, characterized in that molten steel refined in a furnace is drawn off into a ladle in a state where no aluminum has yet been added. that aluminum wire with a diameter of more than 5 mm is continuously fed into the liquid steel in the Gief3 pan at a feed rate of more than 5 ms and the content of dissolved Al in the steel in the range from 0.020 "to 0.050%. preferably 0.020 to 0.040%. And at the same time gaseous nitrogen or nitrogen-rich argon is blown into the liquid steel through refractory material of good permeability, which is attached to the ladle bottom. And that the N ₂ content in the steel is in the range of 0.0045 to 0.0080 %, preferably 0.0050 to 0.0070%, is set.