METALLURGY. 



483 



forging, which may be effected without special 

 precaution and at a comparatively low tempera- 

 ture by the press rather than by the steam 

 hammer. 



In a paper read before the Iron and Steel In- 

 stitute on the changes of structure brought about 

 in steel by thermal and mechanical treatment 

 Mr. A. Sauveur showed that as the smaller the 

 grains of the metal the more ductile and tough 

 it will be, and as the finest possible structure 

 results from heating to Brinell's point W, the 

 temperature at which the passage of cement car- 

 bon into hardening carbon during the heating of 

 steel takes place namely, from 655 to 730 C. 

 it is evident that every finished piece of unhard- 

 ened steel should be heated to that temperature. 



The difficulty of machining so hard a metal 

 has hitherto prevented the use of manganese steel 

 in the construction of burglar-proof safes, for 

 which it is in other respects eminently adapted. 

 This difficulty has been at last overcome. Ex- 

 periments with gun cotton and dynamite on man- 

 ganese steel plates are said to have demonstrated 

 that the resistance of this metal to the action 

 of explosives is unequaled by that of any other 

 metal at present known. 



In the electric welding of tram-rail joints as 

 practiced at Buffalo, N. Y., the bar used for weld- 

 ing is 1 X 3 X 8, and this joining of steel to steel 

 and the increased carrying capacity owing to the 

 bars at the joints results in a joint being a place 

 of least resistance. The plant in operation for 

 the purpose of welding consists of five cars. One 

 of these is a sand-blast car that runs in advance 

 of the welding car and prepares the joint. The 

 other cars are the welding car, the transformer 

 car, the motor and booster car, and a car that 

 runs in the rear to smooth any rough places 

 about the joint. After the welding bars are 

 placed over the joint the jaws of the welder are 

 applied to them, and a pressure of about 1,400 

 pounds is given by means of a hydraulic jack 

 connected to the upper end. The current is then 

 turned on, and the metal becomes brighter and 

 brighter until the weld is completed, after which 

 the current is turned off and the pressure is in- 

 creased to about 35 tons. While under this pres- 

 sure the weld is allowed to cool, after which the 

 car is moved back about 6 inches and the jaws 

 are applied to the other end of the bar, where 

 the process is repeated. The other end is treated 

 in the same manner. In other words, the center 

 weld is made first, and then the end welds. Arti- 

 ficial means of cooling are used, and as the bars 

 cool they exert a powerful influence in bringing 

 the rail ends close, so as to make a tight joint. 

 The current for the operation of the plant is taken 

 from the trolley-wire service. It would be ex- 

 pected, from considerations of the action of heat 

 upon metals, that rails welded in this way would 

 buckle when they experienced a considerable rise 

 of temperature or snap when the temperature 

 was very low, but, as a matter of fact, welded 

 rails neither buckle nor break. By applying im- 

 mense pressure to the material during welding 

 the length of a continuous rail made by this 

 process is said to have no limit except the length 

 of the line itself. 



In special examinations of steel rails which had 

 broken under traffic Mr. W. G. Kirkaldy found 

 that the breakage resulted from failure begin- 

 ning at the top, and that the deterioration was 

 confined entirely to the top or running head. It 

 was of the nature of a mechanical hardening of 

 the surface under the action of the rolling load. 

 In some cases it further developed into a species 

 of disintegration by the formation of minute 



transverse cracks, which by gradual deepening 

 ultimately resulted in failure unless the rail was 

 removed in time. Sir W. C. Roberts-Austen 

 supplemented the reading of Mr. Kirkaldy ' paper 

 in the Institute of Civil Engineers with a state- 

 ment of the principles that guide microphotogra- 

 phy of steel rails. The most generally useful 

 information regarding the structure! of a steel 

 rail is obtained by treating a highly polished sur- 

 face of the section with an effusion of licorice 

 in water, which stains the pearlite a dark tint 

 and leaves the ferrite unacted upon. The most 

 convenient magnification is between 100 and 150 

 diameters. Normal rails have thus been shown 

 to consist of patches of pearlite set in ferrite, 

 and, although the structure is common to all 

 rails, the ratios of the areas differ widely, the 

 amount of carbon increasing with the area of 

 pearlite. If the ferrite is arranged in large, in- 

 closed polyhedrons, the temperature to which the 

 rail was raised before rolling was too high. The 

 strength and intensibility increase as the size of 

 the grain diminishes, and closely interlocking fer- 

 rite and pearlite represent the condition which 

 most favors the prolongation of the life of the 

 i ail. 



In a paper on the value of the microscope in 

 steel working, read before the British Iron and 

 Steel Institute, Mr. C. H. Ridsdale affirmed that 

 the time has arrived when it should be recognized 

 that composition only indicates such well-defined 

 effects as are generally understood within cer- 

 tain narrow limits of treatment, which are termed 

 " normal." Outside these limits the effect of the 

 treatment far outweighs that of the composition. 



It is represented that the Austrian and Rus- 

 sian governments print their bank notes from 

 steel-faced electrotypes made by the electrolytic 

 deposition of iron from a bath prepared accord- 

 ing to the formula of Klein (ferrous and mag- 

 nesium sulphates) under special conditions of 

 temperature and current density. Herr Haber 

 claims, in the Zeitschrift fur Elektrochemie, that 

 the advantage of plates prepared in this way lies 

 in the hardness and fineness of the metal which 

 is first deposited and in the delicacy of the copy 

 of the original which is thus obtained. 



The most remarkable magnetic effect produced 

 by aluminum upon steel was found by Prof. Bar- 

 rett to be the reduction of the hysteresis loss. 

 The permeability of nickel steel was shown to 

 be very much influenced by annealing. It was 

 found that the addition of a small quantity of 

 tungsten to iron hardly affects the maximum in- 

 duction, yet increases the retentivity and coercive 

 force. The experiments show that the best steel 

 for making permanent magnets is one containing 

 7| per cent, of tungsten. 



The removal of mill scale from forgings and 

 plates has always been a matter of considerable 

 difficulty, as the scale is in many instances one 

 twelfth of an inch in thickness. The usual prac- 

 tice is to place the iron in a solution containing 

 1 part of hydrochloric or sulphuric acid to 10 

 parts of water for from half an hour to twenty- 

 four hours. The British Admiralty specify that 

 all steel steam pipes, boiler and collector tubes, 

 and all plates for boilers shall be pickled in a solu- 

 tion consisting of 19 parts of water and 1 of 

 hydrochloric acid until the black oxide and scale 

 formed during the process of manufacture are 

 completely removed. During the process of pick- 

 ling large quantities of magnetic oxide and scale 

 become detached from the plates, which, if allowed 

 to remain in the pickle to be further acted on 

 by the acid, form a serious source of loss. In 

 an invention by Mr. Sherard Cowper-Coles for 



