|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 59
Chap ter 6
U. S . NATIONAL TITANIUM STOCKPILE
Sponge titanium metal can be the key bottleneck in the production of
finished titanium components; therefore, titanium sponge stockpiling has
been a prime component in the U.S. government's defense strategy and in
its support of the industry. Since there are important dif ferences in
the chemistry and melting characteristics of titanium sponge produced by
the various manufacturers, specif ications for purchases of sponge for the
U.S. National Defense Stockpile (the term U.S. National Stockpile is used
interchangably) could determine whether a particular manufacturer's
sponge would be acceptable for the stockpile. Closely related to this is
whether improved and new sponge capacity to satisfy the specifications
would be encouraged by the prospect of sales to the stockpile.
All titanium stockpile purchases to date have been of sponge. Since
ingots and mill products, both commercially pure and alloy , are closer to
final end uses, an important question is whether the U.S. National
Defense Stockpile should include ingots and mill products and, if so,
what specifications should apply.
The primary purpose of the titanium stockpile is to have sufficient
quantities of adequate-quality titanium sponge immediately available for
defense use in time of national emergency (if a stockpile is strictly
limited to national emergency use, it is termed a "strategic
stockpile" ). A secondary purpose has been to use stockpiling as one of
the government's measures to support the domestic titanium industry,
(particularly, via its purchases, to encourage expansion of sponge
manufacturing capacity). Finally, there is always considerable support
to use the U.S. National Stockpile to absorb surplus production during
periods of low demand and to alleviate shortages during high demand
periods (a so-called "economic stockpiled. For the reasons presented in
Chapter 12, this panel recommends that the U.S. National Stockpile for
titanium be kept strategic in character.
The U.S. National Stockpile contains 21,465 short tons of sponge
titanium metal meeting the specifications in force when it was
purchased. In addition to this material, the stockpile contains 10,866
short tons of non-stockpile-grade sponge titanium. The amount of
specif~cation-grade material now held is considerably short of the
recently established goal for stockpiled sponge titanium of 195,OOO short
tons (FEMA May 1980~. This shortfall in specification-grade titanium
sponge in the national stockpile places the United States in a vulnerable
position. The DoD is reviewing the situation and the Air Force has taken
steps in an attempt to remedy it (Appendix D ~ .
59
OCR for page 60
60
The constructive aspect of this vulnerability, however, is that it
gives the government the opportunity to use the buildup of the stockpile
to further o ther national goals . Table 6 shows the GSA titanium disposal
actions since 1960. Among these might be the production of higher
quality. sponge fully usable by all domestic melters. Another would be to
replace a substantial proportion of or substantially augment the
s tockpile sponge goal with ingot and even selected mill product s. In
this manner, U. S . fabricators would have a head start towards producing
end products for their ultimate use in a national emergency. The panel
believes that it does not have sufficient expertise to make recommendations
on these important matters. However, it believes it can note in this
report the perceived options available to the government and leave it to
other, perhaps ad hoc, groups to gather data and consider all the facts
bef ore developing such recommendations.
There is good agreement among stockpile observers that specification-grade
titanium sponge is the only desirable type to be carried in inventory.
As noted in Chapter 5 and Appendix H' U.S. National Stockpile Purchase
Specification P-97-R6 covers titanium metal sponge and ASTM B-299 is the
applicable public specifications An important question is whether or not
these specifications are adequate to serve the best interests of the
nation.
TABLE 6 GSA titanium stockpile disposal actionsa
Year
1960
19 63
1964
19 65
196 6
1967
196 8
19 69
197 0
1971
19 74 b
197 5
Amount
-
17
67
35
117
495
902
113
6
711
51
8, 392
918
Total Sol d
11~844
a Sales authorized under the Defense Production Act (DPA).
b Sales of materials in excess of new goals set by
the Federal Preparedness Agency (now FEMA).
Source: Private communication to the committee by GSA.
OCR for page 61
61
In view of the foregoing considerations, it would appear that the
administration of the stockpile must identify the most probable scenarios
under which the stockpile will be used and then base decisions on
stockpile sponge quality on those scenarios. A key question is whether,
in the national emergency envisioned, the high-volatile-content sponge
manufacturers would be able to continue in full production or would lose
some of their sponge-making capacity. In the latter case, they could not
employ their full melting capacity without securing outside sponge. At
present, the U.S. sponge producers maintain a good balance between their
sponge (plus scrap and alloy additions) and melting capacities. If their
sponge-making capacity were unimpaired during the hypothetical emergency,
they would not need to use any sponge from the stockpile.
The nonintegrated melters (almost one-third of U . S. melting
capacity), on the other hand, would need the stockpile sponge and would
much prefer the low-volatile grades. Thus, in such a si tuation, the
stockpile sponge presently held would not be needed by the integrated
melters and could not be used readily by the nonintegrated melters.
Minkler (1979) has pointed out that if, among other incentives, there
were renewed U.S. stockpile contracts, investments in new greenfield
t itanium winning plants would produce low-volatile sponge f ully
competitive in quality with the Japanese and Soviet product s . The
government 's option of specifying a certain percentage of low-volatile
(Type MD-120) sponge for the stockpile therefore would have the desirable
effect of motivating the existing domestic producers to build greenfield
plants capable of producing competitive-quality sponge and of ensuring
that a portion of the stockpile sponge could be processed readily by all
melters. Again, as noted earlier, the panel is making no firm
recommendation on this matter other than to suggest the establishment of
an ad hoc panel or panels to study these stockpile matters in detail and
then to formulate recommendations. In any case, existing U.S. sponge
manufacturers still could participate in the stockpile buildup if the
government simultaneously decided, that ingots and mill products should
constitute a substantial proportion, such as half, of the stockpile since
the quality of titanium mill products is unaffected by the volatiles
content of sponge that has been vacuum melted.
In addition to the inventory of titanium sponge grades stockpiled,
suggestions have been made for stockpiling consolidated titanium (from
sponge). Both ingot and primary fabricated forms might be considered.
If ingot and fabricated forms were included, some of the metal should be
in alloyed grades rather than unalloyed. Since Ti-6Al-4V alloy is the
most used titanium material (even exceeding the use of unalloyed
titanium), it would appear appropriate to include ingot and fabricated
forms of this material in the stockpile. The grades of Ti-6Al-4V alloy
selected for inventory should be based on a study of grades that are
judged to be most useful for critical applications. It is anticipated
that rotating-grade or premium-grade will be most appropriate (e.g., for
gas turbine engine use ~ .
OCR for page 62
62
Other titanium alloys also might be considered for the inventory.
Suggested alloys include Ti-6Al-2Sn-4Zr-6Mo, Ti-17 (Ti-5Al-2Sn-2Zr-4Mo-4Cr),
Ti-6Al-2Sn-4Zr-2Mo, and Ti-lOV-2Fe-3Al. For other titanium materials
needed to optimize the stockpile content, the selection of various alloys
and grades of alloys should be based on research to determine the most
useful materials.
Consolidated forms of titanium alloys that might be considered for
stockpiling probably should be confined to ingot, billet, and bar. Ingot
definitely should be considered since all other mill product forms stem
from this precursor. Billet also might be considered because the
availability of "off-the-shelf" billet during a national emergency would
save considerable time in the production-of-parts cycle. Further, billet
also is a precursor for a wide variety of other mill product forms as
well as for forgings directly. Bar might be stockpiled in the sizes
amenable to gas turbine engine parts (including compressor blades) since
it is certain that bar stock would be used in large quantities for blade
manufacturing and quite possibly for other uses under a variety of crisis
scenarios.
Specifications for titanium-base ingots, mill products, and alloying
additions are discussed in the final section of Chapter 7. It is noted
that, although there are no public specifications for titanium alloy
ingots, the specifications for mill product quality requirements
indirectly control the quality of ingots. For example, ingots for the
manufacture of quality mill products are prepared to two principal,
widely recognized, quality categories: standard quality and premium
quality. These quality measures generally also apply to the mill product
produced by ingot fabrication (e.g., bloom, billet, bar, plate, sheet);
therefore, the starting material, the ingot, must have an equivalent
quality. Suitable controls are described f or the preparation of ingot
for premium material in the Society of Automative Engineers (SAE) and
ARrospace Material Specification (AXIS) 2380, Approval and Control of
Premium Quality Titanium Alloys. The same specifications used in
defining such products as billet and bar could be applied to def ine ingot
quality for stockpile purposes. Specifications such as ASTM B348 and
MIL-T-9047G as well as AVIS 2380 would be useful in off Bring quality
guidelines for ingot, billet, and bar stock. This aspect of stockpile
guidance should be based also on the results of studies to determine the
most appropriate action. All these inputs could best be integrated by a
separate ad hoc titanium specif ications panel.
REFERENCES
FEMA press release, May 1980.
Minkler, W. W., 1981. NMAB-381, Pp . 65-73 . Assessment of Selected
Materials Issues, National Academy of Science, Washington, D .C.
Representative terms from entire chapter:
titanium sponge
