286 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Skptkmbkr, 



cold hammering produce.!, as is usual, a most beautifully smooth sur- 

 face, in which good workmen delight.), again heated to a dull red heat, 

 and laid down to cool at its leisure; being then at temperature 60", it 

 was placed over the edge of the anvil as before, and after receiving 



105 of the most vigorous blows 

 of the same sledge hammer as 

 was employed in the preceding 

 experiments, it exhibited the 

 most extraordinary evidence of 

 tenacity, by resisting all at- 

 tempts to break it, having 

 passed into the form as given 

 at Fig. 2, that is, bent quite 

 double, and the excessive dis- 

 tention across the part B— C 

 causing the width across at E 

 to decrease at least I of an inch, 

 while the compression at the 

 centre of bending caused the 



^^ metal to expand a like quantity 



at F G Every practical man knows that this is a most severe test 

 of the tenacity of iron, and which the piece in question stood with the 

 most perfect success, for even after having received 105 blows, no 

 evidence of fracture was visible. 



This third experiment then brings us to this most important con- 

 clusion, that there is no inherent evil or ill etfect produced by cold 

 hammerin<r, hut far othenme, namely, that by subjecting wrought iron 

 to the mos"t violent hammering or compression at a low temperature, 

 and then submitting the iron work so treated to the simple process of 

 heating red hot and slow cooling, that we have enhanced its tenacity 

 or shock-sustaining qualities at least twenty times. Here, then, we 

 eet hold of some/acts which I trust I may consider to bear with some 

 important efifects on the treatment and use of iron, especially in the 

 ca^e of its application to railway axles, as from their very required 

 form the process of cold hammering and swaging is all but absolutely 

 necessary in forging the bar of iron out of which they are formed into 

 the requisite shape. 



Fig. 3. 



Fig. 4. 



The above Fig. 3 is the form of a railway axle (one half the length 

 only is shown) as they are generally made, the bearings being at A, 

 the wheels being keyed on the part B. In forging such an axle, the 

 bearings are formed with the requisite collars at the ends by hammer- 

 ing the iron at that part by a series of direct blows of the hammer, and 

 givinf them the requisite finish or precision of form, so far as can be 

 done previous to being finished on the turning lathe, by means of tools 

 called swages, which consist of two pieces of iron covered with steel, 

 and made smooth ; and being of very nearly the same curve as the 

 bearingof the axle, they enable the smith to transmit his blows with 

 much greater precision, and also avoid all hammer marks. 



Fig. 4 may perhaps serve to convey some idea of what is termed a 

 swage. A and B are the upper and under swages, which enable the 

 smith to transmit the blows from the sledge hammer with the greatest 

 precision, and to convert the blow of the hammer into a compressing 

 effect over a very considerable surface of the cylindrical bearing of 

 the axle. During the process the axle C would be laid in the semi- 

 circular hollow of the under swage B, while the upper swage would 

 be kept firmly pressed upon the axle bearing, so as to cause it to 

 receive the blow the instant it was given on the top of the upper 

 swawe A. I have been the more anxious to detail this process, as it 

 is to the effects of this swaging that we are to ascribe the majority of 

 cases of broken axles. Not that the process is bad in itself— far 



otherwise ; it is only bad in its effects, provided we stop there. But 

 if we only take the" trouble to anneal such a swaged axle after it has 

 received the most severe compression, by swaging or hammering at 

 low temperature {i. e. GO^ or thereabouts,) by simply heating it 

 to a dull red heat, and laying it down to cool at leisure, we should then, 

 as in the case of experiment 3rd., have a most extraordinary degree 

 of toughness and shock-resisting quality conferred on it, in place of 

 such a state as detailed in experiment 2nd., with, in all probability, 

 such disastrous results as there are but too truly sad records of. 



I have also been anxious to detail these experiments, as they appear 

 to me to bear directly upon the subject of railway accidents which 

 have arisen from broken axles, in the investigation of which the 

 appearance of the fracture of the broken axle has been made the cri- 

 terion of fitness or otherwise of the iron for such use, and in many 

 cases the iron has been condemned in consequence, when the real 

 truth might in all probability be that it was simply the result of cold 

 hammering, without the subsequent process of annealing at a dull red 

 heat, as before named. 



In the case of experiment 2nd we have what would in general be 

 considered evidence (so far as texture or grain of the fracture goes) 

 of very fine quality of iron ; but what was its actual fitness I leave my 

 readers to judge by the result of that experiment. 



With all due reverence for scientific research, I cannot but think that 

 in this subject, as in many others of the same nature, there is too 

 great a tendency to hunt after explanations of causes and modes of 

 prevention which, as liefore said, we find a much shorter and satis- 

 factory road to, by searching for them in our workshops rather than 

 in our laboratories. I trust my readers will in general agree with me, 

 that the result of these simple experiments tends to illustrate what I 

 state on this head. Our workshops are (if rightly looked into) the 

 true schools of practical science, wherein theory may be seen in its 

 really true state, namely, accompanied with all the circumstances 

 which conspire to give the true result. 



Experiment 4. 



Being desirous to try the effect of temperature in influencing the 

 appearance of fracture as regards crystalline texture, a part of the 

 same bar, as in all the preceding experiments, was taken and warmed 

 from 60° to 100". Such was the effect of this 40° of additional heat, 



