1 Kirkaldy's Experiments on Wrought Iron and Steel, Table H. 2 Ibid. Table F.

Average Tensile Strength And Ductility Of Steel Plates And Bars Made By Some Noted Manufacturers

Landore Steel

Tensile Strength and Ductility. - The mean breaking tensile stress for 101 samples of plates and angle irons, as given by Mr. Riley, was 28-16 tons per square inch, and the elongation 24 '25 per cent.

A series of tests by Mr. Kirkaldy2 gave the following results : -

These experiments show that the difference in the strength of the steel, when tested lengthwise and crosswise of the grain is almost imperceptible.

Whitworth's Compressed Steel

1 Extracted from Tables in Hutton's Practical Engineer's Handbook. 2 Proceedings Institute of Naval Architects. 3 Proceedings Institute of Mechanical Engineers.

The Elastic Limit of steel plates having a tensile strength of 27 .3 tons per square inch either way of the grain, may be taken at 16.6 tons.1 The elastic limit of other forms of steel are given at pages 320, 331.

Steel "Wire is sometimes made for special purposes, e.g. for pianos and for wire rope, with a tensile strength of 120 or even as much as 150 tons per square inch, and with an elongation of about 33 per cent.2

The Crushing Strength of steel varies greatly, according to the quality of the steel and the hardness to which it has been tempered.

Some cylinders of cast steel (of a height = 21/2 diameters) cut from the same bar3 were crushed under the weights given below.

In the experiments of the Committee of Civil Engineers (see p. 320), steel cylinders of 1 inch area and 1 diameter in height bulged but did not crack under 89 tons, and cylinders of the same area, but with height of 4 diameters, crushed with weights averaging 20 tons.

It must be remembered that the steel begins to fail when its elastic limit is passed. This was found by Mr. Berkley to be about 17 tons for Bessemer steel. In the experiments of the Committee of Civil Engineers it ranged between 27 and 15 tons, the average as deduced by Mr. Stoney being 21 tons4 (see also p. 307).

Shearing Strength Of Steel

Mr. Kirkaldy's experiments led him to the following conclusion : - "The shearing strain of steel rivets is found to be about a fourth less than the tensile strain." 5

The steel he experimented upon broke under a tensile stress of 381/2 tons per square inch of area, and the mean strain required to shear the rivets was 281/2 tons per square inch.

"The tests on torsion and transverse strain, tension and compression, show that the relations which subsist between the resistances to these strains in steel correspond very nearly with those found by previous experiments in wrought iron; that is to say, a bar of steel which has 50 per cent more tensile strength than a similar bar of wrought iron will also have approximately 50 per cent more strength in resisting compression, torsion, and transverse strain." 3

Effect Of Different Processes And Circumstances Upon The Strength Of Steel

Effect of Tempering. - After a series of experiments Mr. Kirkaldy came to the following conclusions as to the influence upon steel caused by its treatment in different ways.

"35th. Steel is reduced in strength by being hardened in water, while the strength is vastly increased by being hardened in oil.

"36th. The higher steel is heated (without of course running the risk of being burned) the greater is the increase of strength by being plunged into oil.

"37th. In a highly converted or hard steel the increase in strength and in hardness is greater than in a less converted or soft steel.

"38th. Heated steel, by being plunged into oil instead of water, is not only considerably hardened, but toughened by the treatment."

The following are extracts from the results of the experiments which led to these conclusions : -

1 Head, Institute Mechanical Engineers, 4th August 1885.

2 Percy, Iron and Steel Institute. 3 By Major Wade, U.S. Army.

4 Stoney On Strains. 5 Kirkaldy's Experiments in Iron and Steel.

6 Report by Committee appointed by Board of Trade, etc. etc.