The Blast Furnace

During CF&I’s 121 year history, the method of steelmaking transitioned from Bessemer Converter to Blast Furnace and Open Hearth to Basic Oxygen Furnace to Electric Arc Furnaces. Blast furnaces were 50-100 foot cylinders constructed from fire bricks surrounded by a steel shell.  The fire bricks inside were heat resistant, but still needed to be cooled by water to withstand temperatures exceeding 3,000◦ F.  The purpose of a blast furnace was to extract the iron from the ore. To the iron other minerals would be added such as dolomite, calcite and limestone. This combination, when cooled and shaped, would result in an ingot of steel. Each furnace had four stoves, or tall round topped towers that were connected to it which supplied constant blasts of air.

Blast Furnace with the stoves, 1902

The Blast Furnace steelmaking process began with a precise mixture of iron ore, limestone, and other minerals loaded into skip cars, or small trolley-like vehicles that were hoisted to the top of the furnace on a track. The contents of the skip car would be dumped into the top opening of the furnace. The stoves, full of hot air, would ignite coke, a carbon like fuel that was put into the bottom of the furnace. The carbon in the ignited coke combined with oxygen in the air blast to produce carbon monoxide. Part of this gas combined with the oxygen in the iron ore liquefying the iron ore into a purer iron. Any escaping gas and dust from the process was captured in pipes at the top of the stack known as a down-comer which was later reused in the furnaces.

Blast Furnace cast house. The slag, or waste product, would be skimmed off the top,

The hot iron would flow through the channels to the awaiting ladles for shaping and cooling, 1966

The intense heat of the combustion process would melt the iron ore and limestone inside. The newly made iron would flow throughout the furnace in channels. The iron flowed into awaiting ladle cars that either went to the pig iron casting machines or the open hearth for further processing. The purpose of the melted limestone was to combine with any waste products in the mixture to form slag.  Because the iron was heavier than the slag, it would flow into the awaiting hearth and the slag would float to the top, be skimmed off and removed.

During an average month in the 1920s, each blast furnace would consume 29,000 tons of iron ore, 8,000 tons of limestone and 16,000 tons of coke. The furnaces were tapped every four hours and produced between 85 and 100 tons of metal each tap. About 2,000 tons of air was blown was blown through the furnace daily. Over 10 million gallons of water per day was necessary for cooling purposes. During these peak years of Blast Furnace use, the department employed 600-700 men, including bricklayers, laborers, ladlemen, furnace attendants, steel pourers, mechanics and electricians. Other furnace attendants closely watched each step of the process to guarantee production of the highest quality steel.  An extremely technical job, workers needed to know how to maintain proper temperatures, understand how to raise or lower the carbon content of the molten metal, know the proper time to tap the furnace, and operate the many complex machines.  Numerous tests were performed throughout the operation.

Blast Furnace reunion committee in the Steelworks Center parking lot after

giving an oral history about what it was like to work in the blast furnace. 2012

The first blast furnace, “Furnace Number 1”, was “blown in” a formal ceremony in September of 1881. It was the only furnace that had two names, the formal “Furnace Number 1” furnace, was also referred to as “Betsy” in honor of the first superintendent, Daniel Jones’ daughter, Betsy.

Blast Furnaces were utilized by CF&I until the early 1980s when a more environmentally friendly and economic method of steelmaking took precedence, with the company relying more on scrap metal rather than raw product for steel production.

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