Study on high temperature plasticity of economical acid resistant steel Q345NS
The high temperature plasticity of economical acid resistant steel Q345NS were analyzed using a thermal simulation testing machine,optical microscope,and scanning electron microscope under two composition designs of 0.2％Ni and Ni free.The results show that the high temperature plasticity of the two test steels have similar tem-perature variation patterns,with the high-temperature plasticity reaching its maximum at 700 ℃ and then reaching its minimum at 800 ℃.The addition of Ni mainly improves the high-temperature plasticity of acid resistant steel in the third low-temperature brittle zone.The cross-sectional shrinkage of the 0.2％Ni test steel at 700 ℃ is twice that of the non Ni test steel,mainly related to the finer and more uniform ferrite structure at the fracture surface of the 0.2％Ni test steel.The poor high-temperature plasticity of the two test steels at 800 ℃ is related to the en-richment of Cu and other elements at grain boundaries,which causes grain boundary segregation and thermal embri-ttlement.The above experimental results have certain guiding value for the straightening and lifting of acid resistant steel billets.When the typical billet widths of 2000 mm and 1500 mm are straightened during the casting process,u-sing a pulling speed of 0.8 m/min and 1.05 m/min respectively can reduce the risk of corner cracks in acid resistant castings,respectively.It should also be avoided to carry out slab lifting operations near 600 ℃ and 800 ℃.
economic typeacid resistant steelnickelhigh temperature plasticitycasting billet crack
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