BlueScope could shed 69 operators from its Port Kembla plant if a proposed restructure is given the green light.
The Australian Workers Union says the company is keen to merge the plant's current operator and trade roles, forcing tradesmen to perform both jobs.
The move would leave 32 people out of work in the plant's ore preparation arm, along with 29 employees in the freight mill area, the union said.
Eight more operators in the plant's hot strip mill could be replaced, with fitters already working in the division.
The union, with representatives from the manufacturing and electrical unions, have taken the battle to Fair Work Australia, lodging the case two weeks ago.
AWU South Coast branch secretary Wayne Phillips said operators were "extremely angry".
"It's just about the company trying to get rid of operators," he said.
"It's not about efficiency or productivity, it's just the philosophy the company has; it's a deliberate move by BlueScope to change the nature of the industry and to have no demarcation in there."
Mr Phillips said tradesmen were not qualified to perform operator roles and would require training.
"The manager has said it's only a low-level operator job but that's not the point," he said.
"The point is that it's not their job to do it. You either lose your skills as a tradesperson eventually or you lose your skills as an operator - you can't do both."
The union believes any attempts to reclassify the positions should wait until the workers' award expires in December next year.
BlueScope's manufacturing general manager John Nowlan said the plant had to rein in escalating costs to remain competitive.
"We are not proposing wholesale changes - individual departments are reviewing their operations on an ongoing basis to find the most productive, efficient and flexible way of meeting these challenges.
"As part of this process, BlueScope's senior management regularly consult with our employees and their union representatives to work through how best to implement any proposed changes.
"While most discussions are still at the early phase of consultation, it is inevitable that some ... changes will regrettably lead to some of our people leaving the business.
"As always, we would first look to redeployment opportunities within the business," Mr Nowlan said.