The growth of the open hearth or what is known as the Siemens-Martin process of making steel, during the interval from 1869 to the present time, has been no less remarkable than that of the Bessemer process; for though it has not attained the enormous dimensions of the latter, it has risen from smaller beginnings. Mr. Ramsbottom started a small open-hearth plant at the Crewe Works of the London and North-Western Railway, in 1868, for making railway tires, and the Landore Works were begun by Sir W. Siemens in the same year. On the Continent there were a few furnaces at the works of M. Emile Martin, at the Firming Works, and at Le Creuzot. None of these works, I believe, possessed furnaces before 1870, capable of containing more than four-ton charges, ordinarily worked off twice in twenty-four hours. The ingots weighed about 6 cwt., and the largest steel casting made by this process, of which I can find any account, did not exceed 10 cwt. At the present day, we have furnaces of a capacity of from 15 to 25 tons, and by combining several furnaces, single ingots weighing from 120 to 125 tons have been produced at Le Creuzot. The world's production of open-hearth steel ingots for ship and boiler plates, propeller shafts, ordnance, wheels and axles, wire billets, armor plates, castings of various kinds, and a multiplicity of other articles, cannot have been less than from 800,000 to 850,000 tons in 1882.
The process itself has followed two somewhat dissimilar lines. In this country, iron ores of a pure quality are dissolved in a bath of pig iron, with the addition of only small quantities of scrap steel and iron. At Le Creuzot large quantities of wrought iron are melted in the bath. This iron is puddled in modified rotating Danks furnaces containing a charge of a ton each. The furnaces have a mid-rib dividing the product into two balls of 10 cwt., which are shingled under a 10-ton hammer. The iron is of exceptional purity, containing less than 0.01 per cent. of phosphorus and sulphur. I should add that the two rotating furnaces produce 50 tons of billets in twenty-four hours.