The schoolteacher's son was from 1907 a professional soldier in the German Imperial Navy, and as of 1911 saw service on several submarines.
First, Steinbrinck functioned as a company director of the Organization of German Iron and Steel Industrialists, until he found a new post in 1924 at the Flick conglomerate, where he became First Associate in Friedrich Flick's private secretariat by 1925 and later rose to vice president.