Direct measurement of the gas content of blisters formed by hydrogen attack during steam corrosion in a low alloy steel
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REFERENCES 1. R.A. Lula: Metal Progress, October 1979, vol. 80, pp. 60-65. 2. E. A. Loria: J. Metals, October 1982, vol. 34, pp. 16-22. 3. V. K. Sikka: Oak Ridge National Laboratory Report 5841, April 1982, 12 pp. 4. S. Danyluk: AISI Project 62-440, 1982. 5. E. A. Loria: J. Metals, June 1979, vol. 31, pp. 137-46. 6. E. A. Loria: J. Metals, December 1979, vol. 31, pp. 163-69. 7. G. Krishnamurti and E. A. Loria: unpublished research, 1975. 8. G. Bombara, A. Alderisio, U. Bernabai, and M. Cavallini: Surface Technology, September 1981, vol. 14, pp. 17-23.
Author's Reply S. FLOREEN Mr. Loria has raised a number of issues that would require considerable length to discuss in detail. Since this is perhaps not the best forum for exploring all these aspects of chromium substitution in stainless steels, I will confine myself to trying to reply to the specific questions he has raised. With regard to evaluating the properties of other lower Cr alloys, such as the Cr-lMo steel or lower Cr variations of type 304, the short answer is that the study was done under the usual constraints of time and money, and that we could not do everything. The decision to evaluate only austenite alloys was part of the design of the test program to minimize the variables. Ferritic or martensitic alloys clearly will have a role to play in any overall strategy of Cr conservation. These materials will offer different mechanical properties, fabricability, corrosion behavior, costs, etc., and the selection of the best alloy for any application will have to weigh these various trade-offs. As discussed in the paper, the simulated, heavy section ingots were based on the mold designed by Kane. He did not determine cooling curves for this mold, and no experimental determinations of the solidification behavior were made in the present study. The nominal solidification history for molds of this type could be inferred from the cooling curve data presented by Pellini.1 Some pipe was observed in the ingots to a depth of approximately 20 pct from the top. There was no apparent effect of alloy composition on the extent of pipifig. Aluminum would be a logical addition to try to refine the structure, but no experimental work was done to evaluate refining additions. Preparation of alloys with high nitrogen contents proved to be a considerable experimental problem. Additions of N were made by the use of Mn-N master alloy. This alloy was very volatile. Several attempts were made to add N to vacuum melts, but because of the limitations of the charging bins of the vacuum furnace, fairly large quantities had to be added rapidly, with unsatisfactory results. The final solution was to add the master alloy under air so that the additions could be made slowly. Even then only one satisfactory ingot METALLURGICALTRANSACTIONS A
was produced and another heat with higher N had to be scrapped because of porosity. Mr. Loria is quite right in pointing out that N additions can provide improved corrosion resistance, and further exploration of the properties of low Cr alloys with N, an
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