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I N T E R M E D I A T E A N N E A L I N G OF M O L Y B D E N U M WIRE*

E. P. I g n a s h e v a n d A. U. K h a r i n

Translated from Metal lovedenie i Termicheskaya Obrabotka Metal lov, No. 7,

p. 31, July, 1963

Relative elongation is the most important character is t ic of thin molybdenum wire used for the grids of radio tubes.

The elongation of wire by forging and drawing sintered blocks is often small and irregular, making the manu- facturing of grids difficult and costly because of the considerable loss of mater ia l . The mechanica l properties of molybdenum wire can be improved by heat t reatment [1]. It was shown in [1] that l ight recrystal l izat ion annealing (grain size 3-10 g after annealing) of wire 0.28 mm in d iameter followed by drawing to 80-100 g and addit ional annealing produces a high and uniform degree of elongation. The resistance to fracture of the annealed wire satis- fies the specifications.

of,,%

20

18

76

7~

12

10

g

#

o

e laaa

Batch A

] 1200 I~00 7500 ~s

Batch B

F- 7-7- 1 ?2

18

16

10

12

I0

6

Variation of the relat ive elongation of ~ bydenum wire 50 g in diameter in batches A and B. 1) After recrystal l izat ion an- nealing of wire 0.28 mm in diameter ; 2) without recrys ta l l iza- tion annealing.

The figure shows the effect of annealing temperature on the relat ive elongation of wire with a diameter of 50 ~. Without recrystal l izat ion annealing the necessary 16% elongation can be produced in batch A only after an- nealing at 1450-1540~ and cannot be produced at a!l in batch B. The wire was annealed by drawing it through a tubular furnace at the rate of 12-14 m/ra in .

The use of recrystal l izat ion annealing ensures a high and uniform degree of elongation. In this way the so- cal led "unannealable" 25-30% of molybdenum wire can be e l iminated .

The yearly production of molybdenum wire 50-100 g in d iameter has increased 3% and the return of wire from plants manufacturing grids because of irregular elongation has decreased 90%.

L I T E R A T U R E C I T E D

1. V. KoI' , TechnoIogy of Materials for Vacuum Tubes [ in Russian], Gos~nergoizdat (1957).

* V. A. Lushkina par t ic ipated in this work.

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