since 1871. He obtained coal and coke supplies from the Gelsenkirchener Bergwerks-AG mine, where his brother Emil worked as the director of sales. Kirdorf's strategy paid off and even though by 1887 the company was first among German steelworks, having produced roughly 500,000 tons of rough steel, by 1890 this figure had risen to over a million steel ingots produced.

On 1 January 1905, the steelworks entered into a partnership with the steelworks, which ended in a formal merger between