These alloys are employed in electric installations as current interrupters. Serving as conductors on a short length of circuit, they melt as soon as the current becomes too strong. Following is the composition of some of these alloys.

 

Fusing temperature

Lead

Tin

Bismuth

Cadmium

I...

203° F.

250

500

500

 

II...

193° F.

397

 

532

71

III...

168° F.

344

94

500

62

IV...

153° F.

260

148

522

70

V...

150° F.

249

142

501

108

VI...

145° F.

267

136

500

100

These alloys are prepared by melting the lead in a stearine bath and adding successively, and during the cooling, first, the cadmium; second, the bismuth; third, the tin. It is absolutely necessary to proceed in this manner, since these metals fuse at temperatures ranging from 850° F. (for lead), to 551° F. (for tin).

Fusible Safety Alloys For Steam Boilers

Bismuth

I..... 8

Lead 5

Zinc 3

Point pressure

212° F. 1

II..... 8

8

4

235° F. 1.5

III..... 8

8

3

253° F. 2

IV..... 8

10

8

266° F. 2.5

V..... 8

12

8

270° F. 3

VI..... 8

16

14

280° F. 3.5

VII..... 8

16

12

285° F. 4

VIII..... 8

22

24

309° F. 5

IX..... 8

32

36

320° F. 6

X..... 8

32

28

330° F. 7

XI 8

30

24

340° F. 8