Research on Heat Treatment Process of Q355B Steel for Hob Cutter Box of Tunneling Machine
The effects of different normalizing and quenching processes on the mechanical properties of Q355B steel are studied by tensile test,hardness test,impact test,compression test and microstructure ob-servation.The results show that the microstructure of Q355B steel after normalizing at 900 ℃ is ferrite and pearlite,and the band structure is eliminated completely.The yield strength,hardness and plasticity are all increased to a centain extent,and the impact toughness is significant increased.After quenching at 900 ℃and tempering at 200 ℃,the tensile yield strength and compressive yield strength of Q355B steel reach 743.5 and 756.7 MPa,respectively.Q355B steel exhibits excellent plasticity after different heat treatment,and the tensile fracture and impact fracture are characterized by micro pore aggregation fracture,with some of them exhibiting quasi-cleavage characteristics.Q355B steel meets the hob cutter box material perform-ance requirements of tunneling machine after quenching at 900 ℃ and tempering at 200 ℃,and there is no deformation of cutter box during service.
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