Am I obligated to pray at my workplace if the factory management prevents me from going to the mosque for prayer and threatens to dismiss me from my job?

Congregational prayer is obligatory, and it is not permissible to abandon it except for a valid excuse. If you are compelled to this work and cannot find an alternative, then there is no blame upon you for praying in the factory. You should seek out someone to pray in congregation with you inside it. Otherwise, pray alone, while striving to find work in which you do not miss congregational prayers.