Originally Posted by
Recycled Cycler
I Googled it. Amazing tool that Google.
"By the time the modern "safety" bicycle was developed in the late 1800s most frames were made with steel tubing instead of wood or cast iron. While the steel bicycles were quite strong they were also very heavy. It was not uncommon for a bicycle of that era to weigh in at over 80 pounds."
So seems steel was the material in late 1800's.By 1900, Karl Siemens in Germany replaced Bessemer steel with a better method. You still started with a big batch of melted blast furnace steel (“pig iron”), but instead of cold air you slowly added wrought iron (which has a lot of oxygen in it) or
rust (iron oxide) until you had the right amount of oxygen in the steel. Then you added
limestone as before.
Cheap steel leads to hundreds of new inventions
An open-hearth process allowed for making "cheap steel" and was invented in 1900 and was easier to control and could make even bigger batches of steel. The price of steel kept on going down, while the quality got better and better. People started to make all kinds of things out of steel including bicycles.
Hope that helps. 
So basically the steel used back then was what I said it was, GAS PIPE, because gas pipe contained cast iron, later when French steel manufacture Ateliers de la Rive in cohoots with Vitus came out with the first dedicated bicycle tubing in the 1930's it did not contain pig iron, or cast iron. Gas pipe that contained cast iron, not pig iron, pig iron was crude made from iron ores, cast iron was a result of remelting pig iron with coke and Limestone. Cast iron was used in gas pipe and the first "steel" bikes, but that steel made bicycles heavy at around 80 pounds. Pig iron was not used in bicycle frames because it was too weak, and not used for gas pipe because it was not good at holding pressure.