What would doubled lance tube life do for your blast furnace efficiency?
By switching to grade Sandvik 253 MA*, Brazilian steel manufacturer Usiminas has been able to halve lance tube consumption and increase productivity.
Usiminas is a major Brazilian steel manufacturer. The company's Ipatinga plant operates 3 blast furnaces and produces 5 million tons per year. The plant's ASTM 310 stainless steel lance tubes had a relatively short life span, caused by fast outer surface oxidation and high inner erosion. With the aim of increasing lance tube service life, the company decided to find a more heat resistant tube material. Following a proposal from Sandvik, the R&D department of Usiminas agreed to run trials with tubes in a different grade.
The Sandvik solution
Sandvik recommended replacing 310 grade tubes with Sandvik 253 MA, an austenitic chromium nickel steel grade, which is characterized by very good resistance to isothermal and cyclic oxidation, as well as maintaining structural stability at high temperatures. It includes the rare earth metal cerium, making it oxidation resistant and perfectly suited to the lance tube environment.
Usiminas began trials, and after promising test results the new tubes in Sandvik 253 MA were installed in the main plant in Ipatinga. The tubes were customized by Sandvik to meet the dimensions required by the Usiminas furnace design.
The changeover to Sandvik 253 MA has increased the service life of the lance tubes by 100%, resulting in fewer maintenance stops and increased productivity. By further fine-tuning the lance installation, powder mixtures and injection pressure, Usiminas expects to increase lance tube life even further.
* 253 MA is a trademark owned by Outokumpu OY.