594 



REPORT — 1886. 



maintaining a current of blast through the tuyeres after the blow was finished and 

 during the process of tapping, producing undesirable oxidation of the metal, and 

 describes M. Wittnofftt's suggestions for dealing with the difficulty, also the Clapp 

 and Griffiths diSerential piston valve for closing up the backs of the tuyeres. 



The type of converter as constructed by the writer at Bilston is next described. 

 It consists of a vessel, not unlike an ordinary Bessemer vessel in outward shape, 

 supported and rigidly fixed on four* cast-iron columns; the lower section, containing 

 the charge of metal, having tuyeres through the sides and a solid bottom of silica 

 bricks, is removable, and can readily be replaced by means of a hydraulic ram, 

 ■which raises it into position or lowers it for removal, as required. The blast boxes 

 are fixed around the casing of the upper section in a position above the metal-line, 

 connection from these to the tuyeres being through cast-iron down pipes, each fitted 

 with a ' bafiler " valve (one to each tuyere). These valves are simultaneously 

 closed at the termination of the blow, a small hole through each valve admitting 

 enough blast to support the metal in the converter and keep it out of the tuyeres. 



It is claimed that softer and more reliable material is obtained in this vessel 

 than in the ordinary Bessemer one. Owing to the action being less violent, there is 

 less risk of oxidation, as the final changes take place less rapidly; as, instead of the 

 whole bath being constantly penetrated and oxidised — as in the bottom-blown 

 Yessel — only about a third of the charge is under treatment at once, a further 

 indirect process of oxidation at the same time being carried on by circulation and 

 admixture of the oxidised iron with the remaining portion of the bath. 



This converter has an advantage over small Siemens plants, inasmuch as soaking 

 pits caa be used. 



Some analyses are given both of soft st«el produced and of steel castings, for the 

 manufacture of which this converter is well adapted. 



4. The Influence of Remelting on tlie Projjerties of Cast Iron. 

 By Thomas Turner. 



In the ' Report of the British Association ' for 1853 (p. 87) an account is given 

 of an elaborate series of experiments undertaken by Sir William Fairbairn to 

 ascertain the effect of remelting on the mechanical value of cast iron. The metal 

 used was Eglinton hot blast grey iron, which was melted 18 times in an air furnace, 

 tests being performed at each remelting. It was found that the material gradually 

 improved up to the 12th melting, then rapidly deteriorated, becoming white, hard, 

 and weak at the 18th melting. The following analyses, given in the original paper, 

 are due to Professor Calvert : — 



Percentage of 



These experiments have been largely quoted in the principal v^orks on engineer- 

 ing, metallurgy, and technical chemistry, and various suggestions have been made 

 to account for the effect observed, and the absence of any apparent connection 

 between chemical composition and mechanical value. 



The author has examined specimens of the original bars, belonging to Professor 

 Unwin, who assisted in these experiments. The identity of the specimens is fully 

 assured, and the results obtained have been confirmed by separate analyses per- 

 formed by Mr. J. P. Walton. In six cases also Professor Unwin retains sufficient 

 for examination at any futui-e time, if such shoidd be necessary. The author's 

 results are as follows : — ' 



> Journ. Chem. Soc. 1886, p. 498. 



