DE1017507B - Process for reducing the maximum required pressure when extruding pyrophoric cerium (mischmetal) iron alloys - Google Patents

Description

GERMAN

The forming of ingots made of pyrophoric cerium (mischmetal) -Ei sen alloys with iron contents of 4.5 to 40% by extrusion to form ignition metal strands with commercially available diameters between 2 and about 6 mm requires high pressing pressures, even in the most favorable temperature range between 400 and 500 °. According to literature and our own measurements, the pressing pressures fluctuate within wide limits between 5000 and 16,000 kg / cm ² . The higher the iron content of the alloy and the lower the pressing temperature, the higher they are. These high compression pressures place high demands on the extrusion press and the pressing tools. This manifests itself in a heavy wear of the tools and the risk of their premature destruction. Both factors are of crucial importance for the profitability of the extrusion process.

For these reasons, there has been no lack of efforts to extrude the ingots from pyrophoric cerium (mischmetal) -iron alloys by lowering the required pressing pressure to enhance. In a method that does not yet belong to the state of the art, this goal is achieved special alloy additions to the pyrophoric base alloy made of cerium (mixed metal) iron achieved by that such alloy elements are added, their molar heat of formation, based on 1 gram atom of oxygen is at least 110 kcal. As additives that meet this condition, have the elements calcium, magnesium, beryllium, barium, aluminum, zirconium and titanium as suitable proven. The addition of small amounts of titanium has a particularly strong effect on reducing the pressing pressure.

Extensive operational tests have shown, however, that these special additives have disadvantages can. Titanium and zircon are relatively sparingly soluble elements that under the same melting conditions longer melting times than titanium and zirconium-free alloys otherwise of the same composition require. This is inevitably linked to increased metal burn-off, which is undesirable is. In the case of the other alloy additives mentioned, an increased burn-off is less of a consequence, however, they adversely affect the pyrophoricity and shelf life of the flint, so that their application is only possible to a limited extent.

It has now been found that the undesirable side effects of the abovementioned compressive pressure reducing agents Alloy additives can be avoided if the molten cerium (mischmetal) -iron alloy low copper contents up to a maximum of 0.45% are added. The surprisingly small amounts of copper

Procedure for reduction
the maximum required pressure

in extrusion molding

of pyrophoric cerium (mixed metal!) -

Iron alloys

Applicant:

Th. Goldschmidt A.-G. _r
Essen, Heilermannstr. 15th

Dr. Walter Bungardt, Essen-Bredeney,
has been named as the inventor

tied decrease, the pressing pressure is for the pyrophoricity and the shelf life of the pressed flint without any disadvantage.

In what way small copper contents the pressing pressure can be found in Table 1.

Table 1

attempt composition
of the alloy in% Fe Cu Pressing pressure (kg / cm ² )
at 480 ° No. cerium after 30 minutes (Mixed 19.4 Preheating metal) 19.4 0.14 468 a 80.6 19.4 0.24 5100 469 80.46 19.4 0.31 3500 470 80.36 19.3 0.45 2450 471 80.29 19.3 0.55 2250 471a 80.25 2100 471b 80.15 no longer press cash (partial liquefaction)

For a cerium (mischmetal) iron alloy with around 19.4% Fe, it shows how the pressing pressure changes changes when increasing copper contents of up to 0.55% are added to the alloy. The pressure reduction, which already cause small copper contents is very pronounced. The addition of higher Copper amounts of more than 0.45% are useless, however, since extrusion deformation is above this copper content is no longer possible at 480 °. This is due to the fact that with these copper contents one Partial liquefaction of the starting ingot occurs, making the pressing process impossible. These relationships have already been referred to in German Patent 891,824.

709 70 (1/93

In order to avoid this difficulty, one could think of lowering the pressing temperature as far as until partial liquefaction of the ingot is avoided. Have attempts in this direction However, it has been shown that such a measure does not lead to the desired aim. So shows z. B. Table 2 in comparison to Table 1 shows that when the pressing temperature is lowered from 480 to 440 ° the copper content tolerable for extrusion can be increased from 0.45 to 0.90%; however, the advantage of lowering the pressure by adding copper is largely lost.

Together
cerium
(Mischmetal) establishment of the Legie
^: Fe Tabel 2 Pressing temperature /
Preheating time Press pressure
(kg / cm ² ) attempt
No. 80.15
79.7
79.5 19.3
19.4
19.5 tion in%
Cu 4407-15 min.
440715 min.
440715 min. 4550
4300
no longer pressable
(Partial liquefaction) 471c
471 d
471 e 0.55
0.90
1.00

The pressure-reducing influence of small copper additions, which is very desirable for economic reasons can therefore only be fully utilized at the highest possible pressing temperatures.

Claims (1)

PATENT CLAIM: Process for reducing the maximum required pressure during extrusion molding of pyrophoric cerium (mischmetal) -iron alloys with an iron content of 4.5 to 40%, characterized by the addition of Copper in amounts from 0.05 to 0.45%. Considered publications:
Austrian Chem. Zeitung 40, 1937, p. 302. © 70S 700/83 10.57