PREVENTION OF INGOT CRACKING BY HOT TOPPING.
Abstract
The simple and highly effective approach of eliminating solidification cracks in arc-melted ingots by hot topping with a ductile material has been clearly demonstrated. Sound ingots of 3.5 in. diameter of the high-strength, crack-prone Mo-3 alloy (nominally 1.25% Ti, 0.5% Zr, and 0.1% C) have for the first time been produced, using unalloyed molybdenum as the hot-topping material. The Mo/Mo-3 interface has been defined by a combination of macroscopic, microscopic, hardness, and electron microprobe analyzer techniques. The interface zone is shown to be characterized by porosity and alloy depletion, which, however, does not extend to a depth of more than 0.25 in. into the alloy. Tensile and rupture tests have been conducted on extruded and swaged materials. The 100-hr. strength at 2500 F is determined to be 25,000 psi. Compared with the best data previously obtained, the present materials show considerably higher tensile strength up to 3000 F accompanied, however, by room-temperature embrittlement and low strength above 3000 F. These results have been discussed in terms of the excessive carbon concentration, the correspondingly reduced (Ti + Zr)/C ratio, and their influence on the solution and aging reactions. One t-in. diameter ingot of Mo-3 has also been produced with a nominal hot-topping depth of 1.4 in. The ingot was found to be crack-free, thus demonstrating the feasibility of applying the hot-topping approach to production-sized heats. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1965
- Accession Number
- AD0480065
Entities
People
- L. T. Duvelius
- Winston H. Chang
Organizations
- General Electric