Cryogenic treatments of hot work tool steel type (56nicrmov7)‎

مقدم أطروحة جامعية

Ahmad, Ibrahim Abd al-Karim

مشرف أطروحة جامعية

Thamir, Amin Daway

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم هندسة الإنتاج و المعادن

دولة الجامعة

العراق

الدرجة العلمية

ماجستير

تاريخ الدرجة العلمية

2010

الملخص الإنجليزي

This research is concerned with a new horizon of tool steel heat treatment.

Hot work tool steel (56NiCrMoV7) was used in manufacturing of hot die and punch chosen as a raw material in this research.

Knowing that, these materials were conventionally treated by austinitizing, quenching and two step tempering.

Cryogenic treatments have been used in this research in connection with conventional treatments mentioned above.

It is hoped to eliminate the percentage of retained austenite that developed in the case of conventional treatments.

To accomplish this target, a cryogenic system was assumed, designed and manufactured to meet the requirements of material quenched after austinitizing step.

This system used liquid nitrogen as coolant fluid.

Multi variables were studied such as quenching temperature and soaking time at the coolant.

All the results obtained were compared with conventionally treated samples.

Microstructures were studied carefully supported by image analysis to calculate the percentage of retained austenite and other developed phases.

Tensile, impact and hardness properties were studied carefully to optimize the treatments variables.

Regarding to the best results obtained from samples in oil hardening group C8 with hardness 61 HRC and impact 82J in temperature (-150°C) with soaking time (1hr), while the best results were obtained from samples in air forced hardening group C3 with hardness 60 HRC and impact 72J in temperature(-150°C) with soaking time (1hr).

The maximum tensile strength was obtained for specimens C10 (2188) Mpa with low elongation percentage (6 %).

The basic theory of this treatment is concerned with the accomplished transformation of retained austenite, strengthening of steel by precipitation of sub micro carbides and then a reduction of the tendency to the micro-cracking.

التخصصات الرئيسية

هندسة المواد والمعادن

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-305174