Where in England would a young man, 14-15, be sent to learn trade of an iron molder about 1815?

My ggf, Robert Stanton, was born somewhere in England about 1800. We do not know parents or siblings names.

The first record we have is a baptism of a daughter in St Ann, County Antrim, Belfast, with wife Elizabeth Crossley, no marriage record found in Belfast, in the year 1824, and second daughter baptism 1826. In that year they emigrated to the US to the port of New Orleans and made their way to Tennessee.

Robert is listed in census as an iron moulder or founder. He remarries in 1830, so I assume the first wife dies. Both daughters marry in Tennessee. He fathers an additional 6 children in Tennessee, none follow his occupation, and become farmers.

Where in England would someone be apprenticed to learn this trade, and then why leave to go to US and not remain to work in England in the time frame early 1800s?

Children names, Georgeann, Elizabeth, Martha, Woodman (William?), Benjamin Harrison, George W, Phoebe and Cora.

Maybe some names would have been his family members?

I have seen some birth records about 1805 in England with name Robert Stanton, most stayed and died in England.

How do I locate my Robert Stanton?