The pillar, which weighs more than six tons, is said to have been fashioned at the time of Chandragupta Vikramaditya (375--413), though other authorities give dates as early as 912 BCE
Chandragupta Vikramaditya 2
iron
CHANDRAGUPTA
7î7
because i don't know.
The base of the pillar is tied to its foundations by small pieces of iron. It rises to a height of 7.20 m, with 93 cm buried below the present floor level
Imperial Gupta Dynasty......in 4th century.......
Firuz Shah Tughlak
The iron pillar of Delhi dates to 912 BC. The medieval period of European History dates to 476 to 1453 AD. There are periods of other places referred to as medieval because of some analogy to the European Middle Ages, but I do not know the dates for one in India. There is a link below.
asoka
asoka
This is not pure iron but a special steel.
Effect of acid rain on Iron Pillar of Qutub Minar is- When acid rain falls on the Iron Pillar the colour of Iron Pillar changes from red to black. Other factors like pollution and dust are also responsible. The government should take some strict actions on this issue.