Breaking weight per sq. inch, in tons.

Contraction of area per cent.

Elongation per cent.

Highly heated, and cooled in oil ...

96

3.5

3.3

Do. do. in water .

40

0.0

0.0

Do. do. ,, yellow temper

45

0.0

0.0

Do. do. ,, spring ...

47

0.0

07

Do. do. ,, blue..

50

0.0

07

Do. do. in ashes, slowly ...

54

12.9

7.0

Medium heat, and cooled in oil ...

82

3.5

27

Do. do. in tallow..

79

3.4

27

Do. do. in coal tar ...

75

6.4

6.0

Do. do. slowly..

53

9.4

7.7

Low heat, and cooled in oil ..

73

6.8

5.0

Do. do. in tallow ....

64

6.6

7.0

Do. do. in coal tar

63

131

8.7

Do. do. slowly ....

56

16.5

10.0

Effect Of Annealing Steel Plates

Hard steel plates are greatly improved in ductility by being annealed. With soft steel, however, the increase of ductility is not necessary, and the tensile strength is lessened.

Influence Of Carbon Upon Strength Of Steel

The following Table1 contains the relation between the specific gravity and tensile strength of Bessemer steel of various degrees of carbonisation, made at Sandriken, in Sweden : -

Percentage of Carbon.

Specific Gravity.

Tensile Strength.

Soft.

Hardened.

Tons per sq. inch.

1.5

7.785

7.736

34.39

1.2

7.832

7.771

37.40

0.9

7.874

7.808

56.59

0.6

7.879

7.807

37.41

0.4

7.893

7.839

30.34

The absolute strength appears to be greatest when the steel contains from 1 to 11/4 per cent of carbon.

1 From Bauermann's Metallurgy.