Whitworth's Fluid Compressed Steel was just that. He had the cast ingot solidify under pressure to keep gas (carbon monoxide) bubbles from forming.
That carbon monoxide formed from the reaction between all the oxygen in the steel, and the carbon. Maybe 0.4% in Whitworth's steel.
Later the steel mills learned to add the right amount of silicon, then aluminum, to react with the oxygen. This step is called "deoxidizing" or "killing" the molten steel. Killing, because the ingot is quiet as it freezes/solidifies, otherwise it would be boiling. One old boss of mine said that aluminum killed steel made a "dry weld" when they tried to forge weld it. He was born about 1905. I suppose that dry weld (didn't really stick together) was from the tiny amount of aluminum oxide in the steel.
The last heat of wrought iron made in the USA was about 1960 in Western Pennsylvania.
Walter Cline's book shows a couple of guys hand forging a barrel, I assume of wrought iron, around the 1920's or maybe 1930's.
I remember when Jerry Kirklin gave me a left-over bit from an old wrought iron barrel on a rifle he was restoring. When I looked at it under the microscope . . . THAT was a weld?
So @!*% full of holes it shoulda been able to float. About then I stopped shooting any old guns.
The lines in this forged Belgian Colt Brevete revolver frame are from slag in the wrought iron used -
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