The Edgar Thomson Works

Carnegie was not the first person to build a Bessemer steel plant. His first steel plant, the Edgar Thomson Works, was built in 1874 as the eleventh Bessemer facility in the United States. The facility was outfitted with everything that would be needed for an efficient steel operation, including “a 5-ton Bessemer plant [2 vessels]; a Rolling Mill containing a rail-train and a blooming train of the largest capacity, and a full compliment of Siemens furnaces.”¹ The facility also contained its own machine shop, offices, sore rooms, and material sheds. Most interesting of all was the installation of two five-ton open hearth furnaces, as the use of open hearth furnaces to make steel was not as popular as the Bessemer process when the plant was constructed.

This table displays the annual production of Bessemer steel rails by the Edgar Thomson Works, as reported to the American Iron and Steel Association, from 1875 to 1903.⁵

The output of the Edgar Thomson plant was incredible. Before Edgar Thomson was built, 1500 to 2000 tons of steel produced in a month was seen as fantastic output.² By 1880, the Edgar Thomson works was routinely outputting around 3000 tons of steel ingots per week.³ The plant was able to do this mostly in part to many upgrades of the existing systems and technology. In addition to the scrap heap policy that Carnegie adopted, the Edgar Thomson plant routinely tweaked many of the factors of production. By changing factors such as furnace dimensions and the amount of air blown into the molten metal, the plant was able to experiment and determine what combination of elements led to the greatest steel output. This led to the plant upgrading to four, 10-ton Bessemer vessels by 1890, while also managing to cut the blowing time in half.⁴ These factors helped contribute to the increase in output seen in the following years.

Another factor in the plant’s success was the continued adoption of new technology and machinery. A horizontal ingot stripper and casting on cars were both introduced to cut down on time spent working in the pit, an area beneath the Bessemer converter where the molten steel would be poured down into and molded into ingots. The ingot stripper was a machine that pulled the completed ingots out of the mold and put it in a waiting rail car. Casting on cars was a system where the ingot mold itself was also put on a rail car, allowing the car and mold to be moved out of the pit and letting another take its place.⁶ Both were designed to get the ingot out of the pit as fast as possible.

The Jones Mixer at the Edgar Thomson Works. Molten iron from the blast furnace is being poured into the top of the mixer (left).

Perhaps the most important innovation of the Edgar Thomson Works was a device known as a mixer. Patented by Bill Jones, the device acted as an intermediate storage for molten iron as it was transported between blast furnace and Bessemer converter. The key to the mixer was a simple chalk mark on the side of the vessel, a mark which was never to go beneath the floor. By keeping that chalk mark from going beneath the floor, the design of the mixer guaranteed that there was enough molten iron left over within the vessel to mix with any new iron being put in. This iron would mix with the new stuff constantly being put into the mixer, averaging out the high variability of the iron’s chemistry.⁷ This device played a huge role in ensuring the iron batches had a consistent quality, and use of the mixer was widely adopted across the industry.

Footnotes:

Holley, Letter, MSS#315, Box 36A, FF 1
Bridge, The Inside History of the Carnegie Steel Company, 93
Jones, On the Manufacture of Bessemer Steel and Steel Rails in the United States, 133
Kobus, City of Steel, 107
The Iron Age, 18
Kobus, City of Steel, 126
Ibid., 142