The company notified 614 workers about potential layoffs in Lorain and 142 in Houston, adhering to laws mandating 60 days advanced warning.
The Lorain plant produces about 780,000 tonnes of seamless tubular steel products annually, while Houston produces 120,000t.
The plants will be put into idle in early March, with company spokeswoman Courtney Boone pointing the finger at "softening market conditions influenced by oil prices and trade", according to worldoil.com.
The news comes five months after US Steel announced it would halt two unprofitable tube mills in Pennsylvania and elsewhere in Texas.
