8499

7880

كارشناسي ارشد

ريخته گري

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1392

يازده،81ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

رحمت ا... عمادي، محمود مرآتيان

احمد رضائيان

14/11/92

بهزاد نيرومند، ابوذر طاهري زاده

مهندسي مواد

ID7880

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

82 Study the Effect of Titanium Addition on Creep Behavior of HP40 Heat Resistant Centrifugally Cast Steel Reformer Tube MEHDI ABBASI ABGARMI m abbasiabgarmi@ma iut ac ir Date of Submission august 17 2013 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M SC Language FarsiSupervisors Dr Rahmatollah Emadi Assoc Prof remadi@cc iut ac ir Dr Mahmood Meratian Assoc Prof meratian@cc iut ac ir abstractIn this research the creep behavior of heat resistant steel HP40 produced in Akhgar Steel Foundriesof Isfahan was studied These alloys are widely used in construction of steel tube of reformerfurnaces in petrochemical industries and in iron production industries to produce reducing gases Due to environmental conditions of reformer furnace the process of creep in the tubes is veryactive So the alloy used must be of high creep strength One way to increase the creep resistanceof heat resistant alloys is to add titanium as a good carbide stabilizing element to the compositionof the alloy Using horizontal centrifugal casting method in this study four samples with zerovalues 0 06 0 21 and 0 23wt of Ti were produced To gain knowledge of mechanical behaviorsof the samples tensile hardness and creep tests were performed Microstructures of the sampleswere examined by Optical and Electron Scanning Microscopy Titanium reduced the amount ofcontinuous grain boundary carbides also caused producing finer carbides and well deformation ofthe skeletal modes to the spherical shape Chromium carbides The 100 hour creep tests weredesigned at 40MPa constant stress and temperature of 900 The sample with 0 06 wt ofTitanium was the only specimen that resisted up to 100 hours with of steady state creep rate of6 10E 6 Longitudinal sections of the fractured specimens after the creep tests showed that understress cracks nucleates at the chromium carbides matrix interface and grow in the area Byincreasing titanium secondary formed carbide precipitated during creep tests were of niobium riched and titanium riched precipitates Linear and point analysis of phases showed that thepresence of titanium hinder the transformation of the composed niobium titanium carbides to theG destructive phase Based on data obtained from the creep tests and using the Larson Millerparameter approximate life of tubes at service condition i e 22 5MPa stress and 900 temperature was estimated to be more than 10 years Keywords Creep Niobium Titanium Carbide Reformer Heat Resistant Alloy HP40 HorizontalCentrifugal Casting

رحمت ا... عمادي، محمود مرآتيان

احمد رضائيان

بهزاد نيرومند، ابوذر طاهري زاده