بررسی تغییر خواص استحکامی و سختی فولادH13طی خزش کوتاه مدت

سراجان, زهیر; ناطق, سعید; نجفی دژده, حمیدرضا

doi:10.22076/me.2018.75276.1158

بررسی تغییر خواص استحکامی و سختی فولادH13طی خزش کوتاه مدت

نوع مقاله : مقاله پژوهشی

نویسندگان

¹ دانشجوی دکتری، گروه مهندسی مواد، دانشکده فنی و مهندسی، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی

² استاد، گروه مهندسی مواد، دانشکده فنی و مهندسی، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی،

³ استادیار، گروه مهندسی مواد، دانشکده فنی و مهندسی، واحد علوم و تحقیقات، دانشگاه آزاد اسلامی،

10.22076/me.2018.75276.1158

چکیده

تغییر در خواص استحکامی و سختی آلیاژها عامل اصلی در تغییر نرخ کرنش طی خزش است. بنابراین، اندازه گیری این خواص و مطالعه ارتباط آنها با مقاومت خزشی دارای اهمیت می‌باشد. در این پژوهش، ارتباط بین داده‌های سختی و مقاومت به خزش فولاد H13 طی خزش کوتاه مدت مورد مطالعه قرار گرفته است. آزمون‌های خزش تا شکست و نیز کرنش 1% در بازه دمایی C 600 ـ500 و تنش MPa 5/926 ـ872 انجام شد. سختی‌سنجی بر روی کلیه نمونه‌ها و آزمون کشش بر روی نمونه های خزش با کرنش 1% و در دمای محیط صورت پذیرفت. برپایه نتایج، میانگین توان خزشی 4/5 در تمام بازه‌های تنشی و دمایی مبین غالب بودن مکانیزم خزش نابجائی بود. انرژی فعال سازی خزش این فولاد نیز کم‌تر از انرژی فعال‌سازی نفوذ در خود آهن آلفا (برابر 109 کیلوژول بر مول) بود که بیانگر نقش تنش در انرژی فعال سازی ظاهری این آلیاژ بود. همچنین، ارتباط خطی بین نسبت تغییرات سختی به نسبت عمر خزشی این آلیاژ مشاهده شد، هرچند که شیب آن برای دو بخش سر و گیج نمونه‌های خزش مقداری تفاوت از خود نشان ‌داد. چنین ارتباطی، بررسی مقاومت خزشی و تخمین دقیقتر عمر باقیمانده فولاد H13 را امکان‌پذیر می‌سازد.

کلیدواژه‌ها

20.1001.1.15631745.1397.21.2.8.1

عنوان مقاله [English]

Study of changes in the strength and hardness of H13 steel during short-term creep

نویسندگان [English]

Zohair Sarajan ¹
Said Nategh ²
Hamidreza Najafi ³

¹ Ph.D. Candidate, Department of Materials Engineering, Science and Research Branch, Islamic Azad University,

² Professor, Department of Materials Engineering, Science and Research Branch, Islamic Azad University,

³ Assistant professor, Department of Materials Engineering, Science and Research Branch, Islamic Azad University,

چکیده [English]

Changes in strength and hardness of alloys are the main factor affecting the strain rate during creep. Thus measuring these properties and studying their correlations to creep resistance is an important issue. In the current study, the relationship between hardness and creep resistance for H13 steel was investigated during short-term creep. Creep fracture and 1% creep ductility tests were carried out at 500-600 C and stress of 872-926.5 MPa. Hardness test was carried out on all specimens and tensile test was performed on 1% creep ductility specimens at room temperature. The stress power of 4.5 indicated that dislocation creep was the dominant mechanism. The creep activation energy was lower than the activation energy of the self diffusion of alpha iron (109 kJ/mol), which indicated the role of stress in the apparent activation energy of this alloy. A linear relationship has been observed between hardness variation ratio and creep life ratio, although the slopes for the head and gage were slightly different. This linear relationship makes it possible to more accurately predict the life of H13 steel in creep condition.

کلیدواژه‌ها [English]

Creep
H13 steel
Yield strength
Hardness
Modulus of Elasticity

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