Influence Of Eiectropulsing Treatment On The Microstructure And Properties Of HRB400Steel

In order to adapt to the rapid development of the construction industry needs, toimprove the safety and seismicity of buildings, high-rise building project have put forwardmore and more request to the performance and quality of construction steel. As theprincipal building steel, HRB400steel seriously affects the service life of buildingengineering structure, so it’s imperative to improve the properties of HRB400steel.Electropulsing treatment is an extreme non-equilibrium process under the coupling field ofheat-electricity-stress three-field, the new treatment technology has short time, highefficiency and other advantages. It has attracted much scientific researchers’ attention dueto it can obviously refine the organization and improve performance. The paper exploredthe effect of the high energy transient electropulse quenching treatment and electropulsetempering treatment on microstructure and properties of HRB400steel, and analyzed thestrengthening mechanism of pulse current on HRB400steel.The study found that, with the increase of pulse current and conduction time, themicrostructure of HRB400steel gradually transformed into martensite, and the mechanicalproperties increased first and then decreased. In addition, as the number of pulse currentquenching increased, martensite gradually coarsening and the mechanical propertiesdecreased. Under the conditions of this experiment,45KA-120ms and1times was theoptimal electropulse quenching treatment parameters. Under the optimal parameters, themartensite lath width (160nm-190nm) was compared with traditional quenching martensite(350nm-400nm) decreased significantly, and the average grain size of austenite (~6μm) isquenched’s austenite grain size (~18μm)1/3. Compared with the conventional quenching,the tensile strength and elongation of HRB400steel increased to21.6%and3.6%respectively. After electropulse quenching treatment, the HRB400steel’s fine grains hadfine grain strengthening, lath martensite’s formation had phase transformationstrengthening and dislocation strengthening. The current promoted dissolution of carbide ataustenitizing process, the increase of solid solubility had solid solution strengthening. Electropulsing-HRB400and quenching-HRB400, along with the increase ofelectropulse tempering time, the decomposition of martensite increased, the strengthdecreased while the plasticity increased. Electropulse tempering caused the intensity ofelectropulsing-HRB400decreased amplitude is greater than the traditional quenching.When electropulse tempering time is60ms， the comprehensive mechanical property ofboth were best. The tensile strength and elongation of them were σb=1890MPa,=21.1%(electropulsing-HRB400) and σb=1632MPa,=18.6%(quenching-HRB400) respectively.Compared with tempering treatment, the precipitation amount of carbide is less atelectropulse tempering process, and the carbon content of martensite is higher, mechanicalperformance is better. For electropulsing-HRB400, electropulse tempering treatmentimproved the elongation rate of20%and only reduced the tensile strength by4.7%. Whiletraditional tempering treatment improved the elongation of21.7%but sacrificed16.6%tensile strength. After electropulse tempered, the tensile strength of quenching-HRB400isbasically unchanged and the elongation is improved10%. However traditional temperingincreased the elongation of quenching-HRB400of7.7%, but the tensile strength decreasedby5%.Through the research above, we can draw a conclusion that improved the elongationat the same level, the intensity was higher after electropulse tempering treatment, namelythe comprehensive mechanical properties were better. By comparison, the product ofstrength and ductility of electropulsing-HRB400is the highest after electropulse temperedtreatment,39690MPa·%.The above studies have confirmed that, under certain conditions, electropulsingtreatment of appropriate parameters can partly replace the traditional heat treatment toimprove the microstructure and properties. And the electropulsing treatment can get bettermechanical properties, there are obvious time-saving, energy saving, high efficiency andenvironmental protection advantages.