Masters Theses

Abhilash Dash

Abstract

"The fill lengths of Ni alloyed Cr-Mo steels obtained from fluidity studies (Paper 1) varied linearly with superheat. A 5% Ni steel showed a maximum fill length compared to other steels tested. Ni decreased the liquidus, solidus, and dendritic coherency temperature, but it did not have any significant effect on volume fraction (0.27-0.31) of the solid phase at the dendrite coherency point. The filling time obtained experimentally at 150 C⁰ superheat for 5% Ni steel (HY 130) was close to 1.4 s. For similar conditions, the predicted fill time using a Magmasoft model was close to 1.9 s. Modeling results suggest a high interfacial heat transfer co-efficient of 10,000 W/m²K between mold wall and the solidified shell. Other parameters adjusted in the model were solid fraction profile, viscosity of liquid steel, and pressure profile at the bottom of the inlet. The predicted fill lengths for 5% Ni steel were close to the experimental results. However, the predicted fill lengths for 9% Ni steel were higher than experimental results. This suggested that surface tension and viscosity of liquid metal due to the change in Ni contents affected the fill lengths, but these effects were not taken into account in the model.

The article on fracture toughness (Paper 2) highlights the effect of various deoxidation practices on dynamic fracture toughness of HY130. the use of filters in Al-killed and Ca-treated steel resulted in the highest observed fracture toughness value of 165 kJ/m². The ferro-titanium killed steels that were not treated with mischmetal resulted in the least fracture toughness value of 58 kJ/m². At similar yield strength (YS -970 MPa) and ultimate tensile strength (UTS -1180 MPa) levels, the Al-killed and Ca-treated steels had twice the percentage elongation to failure and three times the percentage reduction in area as compared to the ferro-titanium treated steels which were not treated with mischmetal. The planar spacing between the inclusions, planar inclusion density, volume fraction of inclusions, average inclusion diameter, and aspect ratio of inclusions were determined. Fracture toughness increased with increasing inclusion spacing, increasing average inclusion diameter, and decreasing volume fraction of inclusions. Type II sulfides and a high number density of Ti(C,N) inclusions contributed to low fracture toughness in the ferro-titanium treated steels"--Abstract, page iv.

Advisor(s)

Van Aken, David C.

Committee Member(s)

Peaslee, Kent D., 1956-2013
Richards, Von

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Materials Science and Engineering

Sponsor(s)

Benét Laboratories

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2011

Journal article titles appearing in thesis/dissertation

  • Dynamic fracture toughness of HY-130
  • Effect of nickel on fluidity of Cr-Mo steels
  • Effect of deoxidation practices on dynamic fracture toughness of HY-130 cast steels

Pagination

xii, 85 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2011 Abhilash Dash, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Chromium-molybdenum steel -- TestingMaterials -- Dynamic testingNickel

Thesis Number

T 9814

Print OCLC #

790610517

Electronic OCLC #

908643447

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