Tata employs 3,500 people in Port Talbot and 700 at Trostre.
Read more: Samsung giant to be tested at Narec
Tata Steel has supplied Nissan since it started UK production operations in Sunderland in the 1980s.
Speaking during his visit to Japan, Prime Minister David Cameron said: "Nissan's investment in the UK is a huge vote of confidence in the skills and flexibility of the UK workforce."
Read related article Nissan to create 1,000 new UK jobs here on Metal Supply.