The company says that over the next two months about 375 employees will complete processing and shipping of existing products and prepare the mill to be shut down.
The company says it will consider restarting operations as soon as market conditions improve.
A small crew will remain to maintain the site.
The company's Claymont operation makes steel plate and custom plate products for industrial customers. The work being done at Claymont will shift to EVRAZ facilities in Portland, Ore., and Canada.
The plant along Philadelphia Pike and the Delaware River is 93 years old.