410 NATURE [JANUARY 25, 1917+ 
THE INFLUENCE OF PHOSPHORUS AND | of o'1 per cent. of this element is comparable with 
SULPHUR ON THE eel 
PROPERTIES OF STEEL. 
iy drawing up specifications of the Phemical 
composition of carbon steels the following five 
elements are invariably included: carbon, sili- 
con, manganese, phosphorus, and sulphur. With 
respect to the first three it is always specified that 
the percentage present shall fall within certain 
limits, whereas as regards the last two only an 
upper limit is demanded. These specifications are 
based on the assumptions that while carbon, sili- 
con, and manganese confer desirable properties 
on the iron with which they are alloyed, the char- 
acter and degree of which can be regulated by the 
amount introduced, phosphorus and sulphur act 
unfavourably, and should be kept down to the 
lowest possible figures. They are universally re- 
garded as embrittling agents, which must on no 
account be present above a certain limit in any 
particular case. In fact, if it were possible to 
reduce the percentage of these elements to nil in 
commercial steels, few, if any, engineers would 
hesitate to specify that such steels should be 
absolutely free from them. 
The war, however, has upset a number of views 
which previously were regarded as well estab- 
lished, and in a paper presented at the autumn 
meeting of the Iron and Steel Institute in London 
entitled “The Influence of Some Elements on the 
Mechanical Properties of Steel” Dr. Stead has 
given a distinct jog to the opinion that sulphur and 
phosphorus are always and necessarily deleterious 
to the properties of the steel with which they are 
alloyed. The paper is one of considerable length, 
and deals not only with the five elements men- 
tioned above, but also with copper and tin. It is 
in the nature of a stocktaking of the results 
reached in researches bearing on the influence of 
these particular constituents. Naturally carbon 
and the heat treatment of steel come in for the 
lion’s share of attention, but it is only in the case 
of sulphur and phosphorus that Dr. Stead has 
arrived at conclusions which challenge generally 
accepted opinions, and which deserve—and on 
account of their far-reaching practical significance 
are certain to obtain—the most searching scrutiny 
and, indeed, criticism. 
From first to last the word “shell” is never 
mentioned in the paper. Nevertheless it is the fact 
that it was the bombardment of Hartlepool, Scar- 
borough, and Whitby in December, 1914, by the 
German battle-cruiser squadron which gave the 
impetus to Dr. Stead’s investigation. Pieces of 
German shells were analysed by him and found to 
contain considerably higher percentages of sulphur 
and phosphorus than are permitted in British 
specifications of similar material. This at once 
raised in his mind the question whether it is 
really necessary to adhere to the particular per- 
centages in vogue, and caused him to study anew 
the evidence upon which existing specifications 
have been bz sed, 
Considering phosphorus in the first instance, it 
would appear from the researches of Dr. Stead 
and d’Amico that within certain limits the effect 
NO. 2465, VOL. 98] 
that of carbon, as the following table shows :-— 
‘The effect of ovr per 
The effect of cent, of phosphorus 
o'r per cent, 
of carbon. Stead d'Amico. 
Tonsper Tonsper Tons per 
: 4 : sq. in. sq. in, sq. in, 
Yield point, raised... 22...) “1°70 ees!) 2h) see 
Maximum stress, raised. 4.5, 4°18) “3... 2°4) ee 
y Per cent. Percent. Per cent. 
Elongation, reduced 4°35) fcc Os, 1°36 
Reduction of area, reduced... 7°40 ... 1°5 ... 38 
It will be observed that carbon causes a pro- 
portionately greater reduction of ductility tham 
phosphorus, and, judged by this test, is a more 
powerful embrittling agent. Furthermore, it 
appears from Dr. Stead’s experiments that a steel 
containing 0°30 per cent. of carbon and o-50 per 
cent. of phosphorus resisted long-continugd rotary 
stresses better than a steel with the same carbon 
percentage and only o’04 per cent. of phosphorus. 
These steels were in the forged condition, and 
their structure was “very fine.” Dr. Stead also 
claims that “there is no reliable record showing 
that sound steel rails containing from 0-07 to 0’09 
per cent. of phosphorus break up on the track more 
frequently than those containing less phosphorus,” 
and that “phosphoretic rails undoubtedly resist 
wear better than the same rails with less of that 
element present.” He recalls the fact that pre- 
vious to the use of steel rails, when iron was 
employed, it was customary “to have iron very 
rich in phosphorus in the heads of the rails, for 
it was recognised that the phosphoretic iron wore 
better than the purer material.” His general 
conclusion is :—‘ When judging the properties of 
steel note should be made of the fact that in many 
cases when carbon is rather low phosphorus may 
be an advantage, for it has similar influence to 
carbon which it replaces. Phosphorus has got a 
bad name, like many other elements, but, far from 
always being an enemy, is often a friend.” — 
As regards the influence of phosphorus om 
wrought iron, Dr. Stead affirms that the best York- 
shire and Staffordshire irons contain between o*10 
and o'15 per cent. of this element, and that for 
structural purposes they are superior to the best 
Swedish irons, which contain a smaller amount. 
The elastic limit, yield point, and ultimate stress 
are all raised, and the irons weld more easily. 
The danger limit is put by him at from 04 to © 
0'5 per cent., in which range brittleness develops 
and also a tendency to very coarse crystallisation 
if such iron is heated to high temperatures. 
Ever since’ the pioneering work of Brinell, 
Wahlberg, and Arnold, it has been recognised that 
provided rather more than sufficient manganese 
is present to form manganese sulphide with the 
sulphur in steel, no red-shortness occurs. Arnold 
and Waterhouse showed this in 1903 for a steel of 
the following composition :— 
Carbon Silicon Manganese Phosphorus 
0'460 0°369 1060 0°055 
which rolled perfectly, and was found to be ductile 
both in the tensile and impact tests. They also 
proved conclusively that while sulphide of man- 
ganese in steel is not deleterious, sulphide of iron 
Sulphur 
0560 
