Tata Ryerson, a joint-venture of Tata Steel and US-based Ryerson Inc, is planning to invest Rs 100 crore in setting up three steel service plants in Pune, Chennai and Pantnagar over the next 18 months. The plants will have a rated capacity of 2 million tonne. The company is also planning to enter into the lucrative stainless steel servicing segment. It presently has five plants - two each in Jamshedpur and Faridabad and one in Pune.