Iron is an element, even though admitting all metal sold over the years as Iron, were not elementally pure, while steel is "Always" an alloy, the most basic form being simply Iron & Carbon, though there is usually a little silicon, sulfur & often phospherous present. Many other constituents have been alloyed into steel over the years to gain some advantage for a given purpose.
Normal Cast Iron has a large amount of free carbon & while compartively strong in tension or compression is rather brittle to an impact, smack your Lodge skillet across a rock to test this.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra