Investigation On Enhanced Heat Treatment Of Nanofluids

The CNTs nanofluids were prepared by two-step technique.In this method, thesynthesis of CNTs by chemical vapor deposition(CVD)are the first step and then theyare dispersed in the base fluid.The cooling curves of water,the water base-CNTsnanofluids,N46#oil and the oil base-CNTs nanofluids quenchant were measured byusing X-Y recorder function (LM20A-200)and quench probes with a diameter of22mm and a length of50mm were machined from45#steel.The CNTs nanofluidshave been investigated andtested by means of SEM, viscosity, PSD, wettability.Theinfluences of the concentration of the CNTs,surfactant （SDBS), quenchingtemperature on the cooling curves has been studied and the effect of CarbonNanotubes (CNTs) concentration on the cooling characteristic curves and mechanicalproperties of45#steel has been studied during immersion quenching in oilbase-CNTs nanofluids.The influence of heat treatment procedure parameters, originalmaterial and quenching medium on the yield and the mechanical properties of largercross section40Mn2steel forged grinding balls were researched.The results show that CNTs were treated by ball mill, the acid treatment, surfacemodification and ultrasonic dispersion and CNTs can be stably dispersed in a basefluid.CNTs content is0.2wt%, cooling capacity of nanofluids is greater than thewater and water base-CNTs nanofluids properties increased with further increase ofCNTs content reduced gradually, the cooling speed of adding dispersant SDBSnanofluids was lower than that without dispersant of SDBS fluid and coolingcharacteristics of water base-CNTs nanofluid quenching medium reduced graduallywith the increase of quenching temperature.The contact Angle of oil base-CNTs nanofluids were between12°to19°on45steel, larger than N46#oil, and the contact Angle is gradually increase with theincrease of CNTs content and the wettability has fallen with the addition of CNTs.Viscosity of CNTs oil base-CNTs nanofluids increase with the increase of CNTscontent, and greater than viscosity of N46#oil. With the addition of CNTs, thecooling rate of medium raised, and the cooling rate is gradually increase with the increase of the CNTs content. The properties of45#steel samples which werequenched by1.5wt%oil based-CNTs nanofluids quenchant and30#oil.The resultsshowed mechanical properties of45#steel with oil based-carbon nanotube nanofluidsquenchant is better than N46#oil.The results showed that water was not suitable to be used as quenching mediumfor product-ion of the larger cross section forged steel grinding balls in large scale onthe basis of the yield of the production. PAG quenching medium can be used toreduce scrap rate of product and enabled the thickness of the hardened layer to20mm,product quality stable, impact roughness higher for production of larger cross sectionforged40Mn2steel grinding balls in mass.