| China's rapid industrialization and urbanization drive the rapid development of the construction industry,the output of construction steel bar has reached 20% of the total steel output.In 2018,the steel bar output was about 200 million tons,of which the proportion of 400 MPa steel bars has reached 96%.Microalloying technology is one of the main technical for enhancing of high-strength steel bars.China's high-strength steel bars are mainly based on vanadium microalloying.However,due to the scale of the steel bar market,the implementation of new standards and environmental protection factors,the market demand for vanadium resources has been further increased,resulting in a substantial increase in the cost of hot rolled ribbed steel bars of vanadium microalloying.According to the mechanical properties and stable chemical properties of and rich in vanadium,further reduce the production cost of steel,the HRB400 E hot-rolled ribbed steel is produced by niobium microalloying technology.This topic combines the actual production of hot-rolled ribbed steel bar HRB400 E in a steel plant in China,and formulates a reasonable and feasible test process plan.Five diameter of ?12,?16,?20,?22 and ?28 were produced by niobium microalloying technology.The microstructure and mechanical properties of hot-rolled ribbed steel bars were studied by optical microscope,transmission electron microscope and other means.The yield strength,tensile strength,yield ratio the strengthening mechanism of niobium of niobium microalloyed steel were studied.The production technology of hot-rolled ribbed steel bars with niobium instead of vanadium was developed.(1)The microstructure of HRB400 E hot-rolled ribbed steel bars is mainly composed of ferrite + pearlite + a small amount of Weinite phase,and is in match woth the production standards;(2)The increase of Weinite phase in microstructure affects the mechanical properties of steel bar.;(3)Five kinds of HRB400 E hot-rolled ribbed steel with yield strength ?400MPa,the average value is 450 MPa,tensile strength ?540MPa,the average value is 610 MPa,A?16%,Agt?9.0%.The mechanical properties meet the standard GB/T 1499.2-2018;(4)The five specifications of the HRB400 E were aging.After 15 days of storage of?28 steel,the yield strength decreased by 11.3 MPa and the tensile strength increased by 4.1 MPa;(5)Five size of HRB400 E hot rolled ribbed steel bars were produced by 20 MnSiNb,and the tensile yield platform was obvious.(6)The economic benefit of HRB400 E hot rolled ribbed steel bar produced by niobium iron substituted vanadium microalloying is significantly improved.. |
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