Africa's biggest steel producer, which is majority-owned by ArcelorMittal, said its headline loss had increased to 2.613 billion rand (119.59 million pounds) for the six months to June 30 from a loss of 638 million rand a year earlier.
ArcelorMittal South Africa said some parts of its business would remain idle until demand recovered, including placing the melting operations at its Vereeniging Works on care and maintenance from the third quarter.
The company said it expected steel demand to be at between 70% to 75% of pre-lockdown levels for the foreseeable future.
"On the back of a demanding 2019, the first half of 2020 proved to be incredibly difficult with the widespread health, social and business impact brought about by the global COVID-19 pandemic," ArcelorMittal South Africa Chief Executive Kobus Verster said.
The steel producer, which has long battled against cheap imports, rising costs and a flagging local economy, said last month it had begun talks to cut an unspecified number of jobs as it slashes costs to deal with the impact of the pandemic.
Job cuts are politically sensitive in a country where unemployment stands at a record high of about 30%.
During the period, liquid steel production fell 54% to 1.1 million tonnes and sales volumes dropped 47% to 1.1 million tonnes.
The company's earnings before interest, taxes, depreciation, and amortisation (EBITDA) fell from a profit of 167 million rand to a loss of 1.256 billion rand.
(Reporting by Tanisha Heiberg; Editing by Edmund Blair)