Arrium will use the money to pay back some of its A$1.7 billion in debt, which has become a priority in light of the sliding iron ore price.
Iron ore prices have dropped to around US$82 a tonne, below Arrium's estimated production costs of US$89 a tonne.
"Debt reduction is a key priority for the company, and today's announced capital raising reduces our debt significantly in a single step," said acting chairman Peter Smedley.
Le Brun said the price slide meant the company had little choice but to raise money.
"The company's hands really were tied," he said.
"Shareholders are damned if they do and damned if they don't take up the capital raising because it's so heavily dilutive," he said.
The company's shares, which were placed in a trading halt, last traded at A65c.
- AAP