The European Union's powerful anti-trust authority had in June vetoed the deal, finding that it would have "reduced competition and increased prices for different types of steel".
It also found that proposed solutions would not adequately mitigate the problem. But ThyssenKrupp has now turned to the General Court of the European Union, as it argued that the Commission has "set out a restrictive market definition that unduly extends the scope of the existing competition law".
The German company also claimed the European Commission had failed to take into "adequate account the structural importance of imports into Europe".
"Overcapacities and high import pressure from Asia create an environment in which the planned joint venture with Tata Steel would not have impaired competition," said Kaufmann.
The European steel industry has been hit by a wave of problems, including overcapacity, cheap Asian imports and punishing US tariffs.