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The state of the USA titanium industry in 1995
MATERIALS SCIENCE & ENGINEERING ELSEVIER
Materials Science and Engineering A213 (1996) 1-7
A
The state of the USA titanium industry in 1995 Stan R. Seagle RMI Titanium Company, Niles OH, USA
Abstract The USA titanium industry has been in a prolonged depressed market owing to reduced miIitary requirements and reduced commercial airline sales. Recent capacity reductions and consolidations still leave the industry with significant excess capacity. The response to these market conditions was to develop less costly alloys, reduce processing costs, improve quality and aggressively pursue new non-aerospace applications. These developments combined with current improvements in both non-aerospace and commercial aerospace markets will help stabilize the USA titanium industry in the last half of this decade. Keywords: Applications; Corrosion; Quality assurance; Defects; Alloys
1. Introduction
2. Current business
In 1989 the titanium market was booming and the USA titanium industry was prosperous. Several events occurring in this year would profoundly influence the state of the industry in the early 1990s. The collapse of the Berlin Wall in 1989 would eventually devastate military budgets, thus reducing requirements for titanium mill products. In addition, this opened the Former Soviet Union's (FSU) large titanium capability for use in Western markets. In 1989 the commercial aircraft builders were presenting overly optimistic forecasts that encouraged investment in additional titanium capacity and facilities [1]. Also, in 1989 the Sioux City-United Airlines engine failure started a re-examination on how rotating quality titanium is produced and inspected. These events combined with a worldwide recession would require major adjustments in the USA industry starting in the early 1990s. The titanium industry has had a history of many dramatic market expansions followed by severe declines. However, the poor demand-supply conditions starting in 1991 were unprecedented and the future direction of the industry remains uncertain. This paper will cover the current status of the USA industry and how the industry responded in these difficult times.
2. i. Markets
The world market for titanium is estimated to be between 40 and 50 million kilograms annually [2]. The USA is the largest consumer of titanium. The market generally is divided into three components; defense aerospace, commercial aerospace and non-aerospace. Historically, titanium's health has been equated with the status of the military market. However, new industrial and consumer applications have evolved and the high usage in wide-body commercial airliners have made titanium less dependent on military budgets. Table 1 shows the market segments for the years 1990, the last good year, and 1994, the most recent year. The precipitous drop in demand oc6urred in 1991 with the years 1992, 1993 and 1994 having nearly identical, but reduced demand (Fig. 1). This 18.2 million pound or 35% decrease in market is primarily attributed to lower mil!tary budgets and the poor sales of new commercial aircraft. The largest percent 'decrease is in the defense aerospace market, but the largest weight decrease is for commercial aerospace. Fig. 1 also shows the estimated market for the next few years. The projected increases are modest and certainly do not approach the 50 million pound mar-
2
S.R. Seagle / Materials Science and Engineering A213 (1996) I-7
Table 1 Recent USA titanium mill products markets Market sector
Defense aerospace Commercial aerospace Non-aerospace Total
Million Ibs (kg)
Change from 1990
Reason for decline
1990
i994
lbs (kg)
%
14.3 (6.5) 26.5 (12.0) 11.9 (5.4) 52.7 (23.9)
7.0 (3.2) 17.0 (7.7) 10.5 (4.8) 34.5 (I 5.7)
-7.3 (-3.3) -9.5 (-4.3) - 1.4 (-0,9) - 18.2 (- 8.2)
-5I
Decreased military budgets
-36
Poor airline sales
- I2
World recession
kets of the early 1990s. They reflect an improvement in both commercial aerospace and non-aerospace markets starting in 1995. The military market is not expected to rebound. The high titanium content in new military airframes such as C-17 and F-22 may help offset further declines in other military spending. The commercial aerospace market is starting to improve in mid 1995. This should be further assisted by the new airplanes such as the Boeing 777 which have high titanium contents. In addition, new non-aerospace uses for titanium continue to be found which should provide further market growth. 2.2. CapaciO'
As recently as the late 1980s, market forecasts projected steady increases in deliveries of commercial and military aircraft. Reliance on these forecasts led to expansion of capacities, including investments in new facilities. Table 2 shows the capacities for sponge production and melting in 1990 arLd 1995. The current World sponge capacity is estimated to be 117 million kilograms (257 million pounds). This is a 25% reduction in capacity since the peak in 1990 as all countries reduced capacity except the People's Republic of China. Europe has no sponge production as a result of the closing of Deeside Titanium in the United Kingdom. Since about one kilogram of spoage is needed for one kilogram of mill product, the current capacity is calculated at over two times current market requirements. The remaining plants are all magnesium-reduced technology. All sodium-reduced titanium plants have now been closed. This technology produced a very high purity product and had the capability of generating low cost powders. Unfortunately sufficient markets did not exist to support these facilities. The FSU dominates the world capacity for sponge, however there is some question on the ready availability of aJl this capacity. About 1.5 kg of ingot product are required to produce one kilogram of mill product. Again the melting capacity is nearly 2.5 times the market requirements. Only a moderate amount of capacity has been closed. Again the
-35
FSU dominates this capacity and the condition and ready availability of this capacity is uncertain. 2.3. Market and capacity impact
With smaller World markets and a large FSU capacity for both sponge and mill products, the current state of the USA industry is very precarious. The consequences of these persistent market conditions for the last four years have included large financial losses, plant closings, consolidations, capacity reduction and ownership changes. Public financial data are available for the three largest USA mill product companies, Tremont, Oremet and RMI Titanium. The book value of the combined US companies has decreased in the past four years from 441 to 186 milliofl dollars. Obviously this cannot continue without dramatic consequences to the USA industry. Additional consolidation may be required if the current market improvement is not sustained or if new applications with sizeable markets are not quickly developed. Although the USA titanium industry has suffered through a severe market entrenchment, most believe that the titanium market has not matured, and titanium with its unique combination of properties is a metal still
20
= o
t~
._o =
90
91
F-1 DefenseAerospace
I
92
93
94 Year []
95
96
Commercial
97
Aerospace
• Non-Aerospace
Fig. 1. USA titanium mill product shipments,
S.R. Seagle / Materials Science and Engilwer#zg A213 (1996) I - 7
3
Table 2 World titanium capacity Country
Former Soviet Union (FSU) Japan USA People's Republic of China Europe (UK) Total
Ingot/slab million ibs (kg)
Sponge million lbs (Kg) I990
1995
1990
1995
200(91) 64(29) 67(30) 6(2.7) 11(5) 348(158)
160(73) 57(26) 34(15) 6(2.7) 0(0) 257(117)
231(105) 50(23) 153(69) 8(3.6) 19(8.6) 461 (209.2)
231(105) 50(23) 131(59) 8(3.6) I8(8.2) 438(198.9)
in its infancy. The metals' outstanding corrosion resistance in most natural environments, particularly sea water, has not been fully exploited. In addition as energy reserves are depleted and we are required to spend more in acquisition cost to obtain energy, titanium's strength-to-weight ratio makes it attractive for both energy extraction as well as use in energy intensive applications. Continued expansion of titanium markets will be possible by exploiting its unique properties while at the same time developing technology to reduce the cost of using the metal. Even in this recent difficult environment many new developments are underway. The remaining portion of this paper will provide examples of the progress in the USA related to improved quality, lower application cost and examples of emerging new markets.
3. Technical developments
5.i. Aerospace Quality During the production of titanium mill products, defects of high melting point metals or compounds occasionally have been introduced through contaminated raw materials. The very hard defects such as WC and nitrogen-rich Type I have proven to be most troublesome and in 1990, in response to the Sioux City incident, the Federal Aviation Agency (FAA) set objectives to eliminate all defects through improvements in both processing and inspection [3]. Prior to 1990 the industry-wide defect rate in rotating billet was greater than four per million pounds. This has now decreased to less than three and is expected to decline further as a result of new developments in hearth melting, vacuum arc melting and sonic inspection. Hearth melting has been pursued as a process having the greatest potential for eliminating high density and Type I defects [4,5]. Since molten metal time can be controlled, the hearth offers the potential to dissolve defects and to separate the high density defects to the bottom of the hearth. Significant progress has been made in developing the technology, however, further
refinement of the process is necessary to assure complete elimination of the defects. The technology at this point in development has not been endorsed by all the engine manufacturers. The conventional technology of three vacuum arc melts (triple melt) has improved in the last few years as a result of more stringent process control and appears at this time to be as effective as the hearth technology for producing nearly defect-free ingots. Realizing that process changes may not totally eliminate all types of defects, improving sonic inspection process was established as a goal by several engine manufactures. A new system termed Multizone has been developed by General Electric Research [6,7]. The system utilizes multiple transducers focused at specific depths or zones. The technology was first implemented and developed on the shop floor at RMI Titanium Company by parallel testing over 500 000 kg of rotating quality billet using both the Multizone and conventional systems simultaneously [8]. For billet diameters up to 254 mm, the Multizone process was able to test to a 0.8 mm flat bottom hole standard while the conventional process was limited to a 50% larger t.2mm standard. Defects such as WC were found using the new technology that were not evident in the conventional inspection. As a result of this effort, improved sonic standards have been implemented recently for rotating quality titanium billets. These quality improvements will assure the continued high usage of titanium in gas turbine engines.
3.2. Aerospace titanium alloys Annealed Ti-6AI-4V has been the predominate titanium alloy for airframe and engine applications. Occasionally new aerospace platforms such as the C-17, F-22 and the Boeing 777 offer the opportunity to introduce new alloys as well as new titanium applications. Several high strength heat treatable alloys are now being used and their properties are summarized in Table 3. Both Ti-10V-2Fe-3A1 and Ti-6-22-22S were developed in the 1960s but are now just starting to see significant commercial applications. Their high strength combined with good toughness are attractive for many airframe applications including landing gears.
S.R. Seag/e / Materials Science and Engineering A213 (1996) 1-7
4
Table 3 High strength aerospace alloys Property
Maximum useful temperature
Alloy Ti-10-2-3
Ti-6-22-22
Alloy C
260
320
650
1170 1070 8 66 Landing gears Deep hardening; High strength
1100 1000 10 82 Airframe components High strength; good toughness
1000 930 20
(c) UTS (MPa) YS (MPa) EL (%0) Application Characteristic
The T i - 1 0 - 2 - 3 is in the C-17 and Boeing 777 and the Ti-6-22-22S is used in the F-22 fighter. All these new planes contain large quantities of titanium in the airframe. The C-17 is 12%, the Boeing 777 is reported to be about 12% and the F-22 is 41% with the T i - 6 - 2 2 22S being 5% [9]. Alloy C is unique because of its resistance to burning and is used in the two-dimensional thrust-vectoring exhaust nozzles on the F-119 engine. The well known titanium gamma aluminides have received extensive technical interest and look very promising for very high temperature applications. However, they have not yet been accepted as a major material of construction because of high cost, low toughness and low ductility. 3.3. L o w cost alloys - - co~'rosion resistant
Crevice corrosion is a major problem in many elevated temperature chloride environments. Traditionally, ASTM Grade 7 (Ti-0.15% Pd) has been recommended for this severe service. The addition of 0.15% Pd nea/ly doubles the cost of titanium and thus makes it unattractive for many applications. More recent work shows that Pd additions at the reduced level of 0.05% are suitable for most applications requiring added corrosion resistance [10,1i]. Furthermore, ruthenium at 0.10% is equally effective for corrosion protection as illustrated in Table 4. Although 0.10% Ru has equivalent corrosion resistance to 0.05% Pd, the ruthenium addition is less costly. The Pd addition increases the cost of commercially pure titanium approximately 30% while similar corrosion protection is achieved for only 10% additional cost with the Ru addition. Noble metal additions are also effective for improving the corrosion resistance of higher strength titanium alloys. As in commercially-pure titanium, the 0.05% Pd and 0.1% Ru addition provide similar improved corrosion resistance in alloys. The Pd version of these alloys were recently given Grade designations by ASTM. The Ru adjusted alloys are a newer development and are
Engine exhaust nozzels High temperature strength; burn resistant
now starting to be seen in commercial activity, Examples of potential applications are shown in Table 5. Ti-6AI-4V-0.01Ru has been selected for production tubulars in high temperature geothermal brines. 3.4. Low-cost alloys ~
h~dustrial applications
Most titanium alloys were developed for aerospace applications without regard for the alloy cost and are often applied in industrial applications because of availability and well known properties. More recently alloys made from less costly alloying elements have been proposed to penetrate markets very sensitive to cost such as automotive. Examples are shown in Table 6. The compositions include both alpha-beta and beta type alloys. The alloys use molybdenum and iron to replace more expensive alloying elements, particularly vanadium. The beta alloy Ti-4.5Fe-6,8Mo-I.5A1 is made from steel-type F e - M o master alloy which is not normally as clean as aerospace master alloys. However, this has not been detrimental to mechanical properties, The high oxygen version of Ti-6A1-4V takes advantage of abundant low-cost scrap. The composition was adjusted to achieve ballistic performance equal to or better than standard Ti-6A1-4V alloy. Theses approaches to alloy design can lower the alloy formulation cost by approximately 20% and hopefully open new market opportunities. 3.5. Low-cost process#zg
Only a small portion of titanium output is processed on efficient high volume mill equipment of the type used in steel industry. The first products to reach sufficient volume were commercially pure (CP) titanium strip followed by welded tubing. The market size allowed for development of these processes. The hearth' melting process developed in the USA and used by A. Johnson Company, Wyman-Gordon and Teledyne A1lvac may be considered the first step in a continuous
S.R. Seagle / Materials Science and Eng#wer#zg A213 (I996) 1-7 Table 4 Effect of Pd and Ru on the corrosion resistance and cost of several titanium alloys in boiling 1% HC1 (mm/yr) Base alloy
Ti (grade 2) Ti-3A1-2.5V (grade 9) Ti-6AI-4V (grade 5) Beta C (grade 19) Relative cost Ti (grade 2)
Typical yield strength MPa
Noble alloy addition, % 0
0.05Pd
0.10Ru
350 550 900 1050
1.82 2.6 2.8 0.2
0 0.01 0.07 0.0I
0.01 0.01 0.08 0.01
350
I
1.28/1.3
1.10/1.1
type casting process for mill products. The electronbeam hearth process is very efficient for producing slab of commercially-pure titanium. More recently, RMI titanium successfully produced a range of large diameter seamless alloy pipe using the Lorain, Ohio, steel processing facilities of the USS/Kobe joint ' venture. Seamless alloy pipe between 250 and 350ram diameter by 37m long with a wall thickness between 19 and 25mm has been produced using the rotary-piercing mill. Although this technology was demonstrated many years ago by U.S. Steel in both the Gary Works and Elwood City Works, market opportunities were not available to take advantage of this low-cost process route. The availability of this low-cost process will allow titanium to compete in several energy related markets. A modified version of Titanium roll-clad steel plate has been developed to significantly reduce the cost of chemical equipment produced from specialty titanium and zirconium alloys [10]. The process consists of roll cladding low cost Grade 2 or 9 backer plate to which a 1.0-1.4 mm thick skin layer of a more chemically resistant titanium alloy (Grade 7 or 12) or zirconium. Recent cost comparisons of Ti/Zr roll-clad plate with solid plate at equivalent thickness indicate a potential cost savings of 15%-25% over Ti-Grade 7 plate and 20%-45% over Zr 702 plate. Casting is a low cost method of making a component. The current lost-wax investment casting process is complicated and labor intensive. Process development work at Howmet Corporation suggests that permanent mold casting of titanium is possible [12]. The advantages include lower cost (40% to 50%), simpler manufacturing process, tighter process control, improved dimensional control, no alpha case and refined microstructures. This process has been demonstrated with both conventional titanium alloys and gamma alloys. The first production castings are now under engine evaluation.
4. New markets 4.I. Energy extraction Titanium alloys have been selected for several new applications because of their combination of properties and competitive cost. Geothermal wells exceeding 460 m can reach temperatures as high as 285 °C in the Salton Sea of Southern California. The traditional material of construction has been low carbon steel which has a life of less than one year. Large diameter extruded pipe of Beta C was first tested in this environment in the 1980s and has performed well. The expected life is greater than 30 years [13]. In the meantime, new design analysis indicates the high strength of Beta C is not required and additional corrosion resistance is desirable. This led to the recent production of Ti-6AI-4V-0.1Ru large diameter (250-350 mm) seamless tubulars as the material of choice' for most recent wells. The combination of low-cost processing combined with a modified, improved alloy assures titanium's competitive edge in this market. Conoco-Norway, Inc (CNI) is developing the Heidrun Field for hydrocarbon production. This field is on the Norwegian Continental Shelf in the northern North Sea, some 120 miles off the mid-coast of Norway. Development of this field utilizes a tension leg platform (TLP) for both drilling and production of hydrocarbons at a water depth of 345 meters. Installation of the TLP is scheduled for late in 1995. The 56 production and ejection wells planned in this field will be tied back to the TLP from the subsea production well template via high pressure production risers. Drilling of these wells from the TLP deck will be accomplished using one high-pressure titanium alloy drilling riser. The drilling riser for offshore drilling has traditionally been a low-medium strength steel alloy, which has been satisfactory for shallow waters (depths below
6
S.R. Seag/e /Materials Science and Engineer#Tg A213 (i996) I - 7
Table 5 Candidate applications for Pd- or Ru-enhanced alpha-beta and beta titanium alloys Application
Applicable alloys containing Pd or Ru Ti-3AI-2.5V
Ti-6AI-4V
Beta C
Wet oxidation Other waste treatments High temperature organic systhesis Hydrometallurgical ore leaching Deep sour gas and geothermal wells Downhole tool and accessories Offshore flowlines, export and catenary r,sers
305 m). Owing to the deeper waters involved at the Heidrun TLP location and the high-pressure drilling design (i.e., topside BOP)~ CNI considered other lower-weight, higher-strength, and easier to handle material alternatives for the dri?ling riser. Given the severe well bay spacing constraints, this drilling riser also required special design considerations to account for riser interference under severe weather conditions. In early 1991, CNI pursued conceptual engineering studies to evaluate the feasibility and practicality of producing and utilizing a titanium alloy drilling riser for this service. These studies confirmed that the titanium drilling riser was indeed a viable option, and offers economic advantages over steel from both an initial and life-cycle cost standpoint. This stems from elimination of costly riser flex joints and syntactic foam buoyancy, as well as reeuction of tensioning equipment size, deck storage requirements, running time, and maintenance with titanium. This evaluation revealed that the high-strength ELI Ti-6AI-4V alloy riser exhibits approximately one-fourth the weight and three times the flexibility of a high pressure steel riser, while offering immunity to seawater corrosion and superior sea water fatigue p~operties. CNI's preliminary engineering studies also indicated that the design process and melhodology for a titanium alloy riser is basically the same as that of a steel riser, permitting expedient engineering to progress for this project. The technology for manufacturing and fabricating (i.e., welding) the titanium alloy riser was deemed available as well, and had been demonstrated in large tubular prototypes such as the Placid Oil riser stress-taper joint produced from the ELI Ti-6AI-4V alloy. Based on all these favorable engineering and cost considerations, CNI purchased a 61 cm OD x 2.2cm minimum wall ELI Ti-6AI-4V high-pressure drilling riser for the Heidrun Field. Total consumption of titanium for this single project was in excess of 115 000 kilograms.
4.2. Consumer applications Consumer applications have not developed at the
rate originally expected when the metal was first industrialized in the mid 1950s. The anticipation then and the hope over the last forty years was to find automotive applications. The automotive manufactures started to look seriously at titanium in the early 1980s. Most of this effort in the USA was focused at Ford Motor Company and consisted of the evaluation of suspension springs, valves and valve springs [14]. The impetus for the work was the mandated fuel economy improvements known as CAFE. Unfortunately, titanium has not been selected for use in any large volume production models and has been limited to a few optional parts on high performance cars and demonstrated in concept cars like the Neon Lite. Although there is a new, well funded, Government sponsored initiative in the USA for light weight automobile materials, this author believes that significant titanium usage will not occur until the CAFE standards are more stringent or until energy prices escalate to the point titanium can be considered cost effective for weight reduction. An exception could be the use of gamma aluminides as valves if a low-cost manufacturing process is developed. Titanium has been used to a minor extent in sports equipment such as skis, tennis rackets and golf equipment. The most surprising new major use is the development of titanium driver golf club heads. Because of titanium's strength-to-weight ratio, the club head can be built larger (250 cc vs. 175 cc volume) without loss of integrity. This allows the manufactures to design a club that is easy to swing, easy to hit straight and more forgiving. The market in the USA is expected to exceed 1400000 kilograms in 1995. All clubs produced in the USA are by investment casting Ti-6A1-4V. This market is expected to grow 20% to 25% per year as the titanium heads move from driver to irons. Titanium golf clubs may be a passing fad. However, in depressed times, a new application is welcome. Numerous other consumer markets including archi" tecture, medical and jewelry have enjoyed modest increases. However, a large single consumer market still evades this metal.
S.R. Seagle I Materials Science and E1~ghzeeriszg A213 (1996) I - 7
7
Table 6 Low-cost industrial titanium alloys Alloy
Cost
YS MPa
Concept
Application
Ti-6A1-4V Ti- 5AI-2Fe Ti-6AI-4V-0.250 "SAT" Ti-4.5Fe-6.SMo- 1.5A1 "LCB"
1 0.82 0.85 0.78
825 825 900 1100
Base Comparison Low-Cost Alloying Elements Low-Cost Scrap Ferro-moly steel Master alloy
Automotive Ballistic Armor Springs. Torsion bars
5. Summary The USA titanium industry appears to be transitioning out of a prolonged 35% market retrenchment caused by reduced military spending and poor commercial aircraft sales. Despite capacity reductions, the world titanium industry still has appreciable excess capacity in both sponge and ingot. Current projections suggest that the market will improve during the last half of 1995 owing to increased consumption in nonaerospace, commercial aerospace and inventory replenishment. The future for titanium is still optimistic as new technical developments and applications are pursued. New low-cost corrosion-resistant and industrial alloys will make titanium more attractive. The development of low-cost processing will also improve the competitiveness of the metal. The application of high strength alloys opens new opportunity in aerospace airframe and engine applications. As titanium becomes more cost-effective, new applications will continue to develop in consumer and energy extraction markets.
References [I] S.R. Seagle. Current and future trends in special materials, IVor/cshop Presentanons on Critical Issues jot the Aerospace Special Materials bz&tstrial Base, National Materials Advisory Board, Washington, DC, JuIy, 1994. [2] P. Bania, Current and future trends in the titanium industry, [Vorkshop Presentations on Critieal Issues for the Aerospace Speeial ~[aterials Dzdustrial Base, National Materials Advisory Board, Washington, DC, July, 1994.
[3] R.J. Koenig, J.G. Costa, R.E. Gonzalez, R.E. Guyotte, D.P. Salvano and T. Smith, Titalziu~12 Rotating Compo~zents Re~,iew Team Report, US FAA Aircraft Certification Service Engine and Propeller Directorate, December I4, 1990. [4] M. Osthelmer and S.R. Seagle, Utilization of electron beam melting in the production of defect free Ti-6AI-4V ingots, Sixth World Coi~jFreneeon Tita~Hum, Societe Francaise de Metallurgie, June 6, 1988. pp. 579-582, [5] C.E. Shamblem and G.B. Hunter, in Cordy and Lherbier (eds.), Titanium base alloys-clean melt process Development, Proc. I'acuum Metallurgy Co~(:, 1989, pp. 3-1 I. [6] P.J. Howard and R.S. Gilmore, Ultrasonic noise and the volume of the ultrasonic pulse, Reciew oJ Progress #7 QNDE, 15, to be published. [7] D.C. Copley and P.J. Howard, in D.O. Thompson and D.E. Chimenti (eds.), Reciew oj" Progress m QNDE, Plenum, New York, 1995, pp. 2145-2151. [8] J.C. Moyers, S.R. Seagle, D.C. Copley and R.S. Gilmore, Multizone sonic testing of titanium billet, Eighth World Co~zjerenee on Titanium, IJ~stitute of Materials, October 22, I995. [9] At,iattot~ If'eek, McGraw-Hill Companies, July 24, 1995, p. 47. [10] R.W. Schutz, Recent titanium alloy' and product developments for corrosive industrial service, I995 N,4 C£ Aimual Meet., Paper No. 244, NIarch 26, 1995. [11] R.W. Schutz and M. Xiao, Optimized lean-Pd titanium alloys for aggressive reducing acid and halide service environments, Proc. I2th Int. Corrosion Congr., col. 3A, September I993, NACE, Houston, TX, p. 1213. [12] N. Paton, Advances in titanium casting technology, Workshop PresentatioJzs otz Critical Issues Jot the Aerospace Special Materials hMustrial Base. National Materials Advisory Board. Washington, DC, July, I994. [13] W.W. Love, C.J. Cron and D. Holligan, The use of Beta Ctm titanium for downhole production casing in geothermal wells, Si.'cth World Col~J'ere~zce on Tita~Hm~7 Proceed#~gs, Les Ulix, France, Societe Francaise de Metallurgie, 1988, p. 443. [14] A.M. Sherman and S.R. Seagle, Titanium coil springs for automotive suspension systems, SAE paper 800481, AutoJtzotzve Engineering, May I980.
Materials Science and Engineering A213 (1996) 1-7
A
The state of the USA titanium industry in 1995 Stan R. Seagle RMI Titanium Company, Niles OH, USA
Abstract The USA titanium industry has been in a prolonged depressed market owing to reduced miIitary requirements and reduced commercial airline sales. Recent capacity reductions and consolidations still leave the industry with significant excess capacity. The response to these market conditions was to develop less costly alloys, reduce processing costs, improve quality and aggressively pursue new non-aerospace applications. These developments combined with current improvements in both non-aerospace and commercial aerospace markets will help stabilize the USA titanium industry in the last half of this decade. Keywords: Applications; Corrosion; Quality assurance; Defects; Alloys
1. Introduction
2. Current business
In 1989 the titanium market was booming and the USA titanium industry was prosperous. Several events occurring in this year would profoundly influence the state of the industry in the early 1990s. The collapse of the Berlin Wall in 1989 would eventually devastate military budgets, thus reducing requirements for titanium mill products. In addition, this opened the Former Soviet Union's (FSU) large titanium capability for use in Western markets. In 1989 the commercial aircraft builders were presenting overly optimistic forecasts that encouraged investment in additional titanium capacity and facilities [1]. Also, in 1989 the Sioux City-United Airlines engine failure started a re-examination on how rotating quality titanium is produced and inspected. These events combined with a worldwide recession would require major adjustments in the USA industry starting in the early 1990s. The titanium industry has had a history of many dramatic market expansions followed by severe declines. However, the poor demand-supply conditions starting in 1991 were unprecedented and the future direction of the industry remains uncertain. This paper will cover the current status of the USA industry and how the industry responded in these difficult times.
2. i. Markets
The world market for titanium is estimated to be between 40 and 50 million kilograms annually [2]. The USA is the largest consumer of titanium. The market generally is divided into three components; defense aerospace, commercial aerospace and non-aerospace. Historically, titanium's health has been equated with the status of the military market. However, new industrial and consumer applications have evolved and the high usage in wide-body commercial airliners have made titanium less dependent on military budgets. Table 1 shows the market segments for the years 1990, the last good year, and 1994, the most recent year. The precipitous drop in demand oc6urred in 1991 with the years 1992, 1993 and 1994 having nearly identical, but reduced demand (Fig. 1). This 18.2 million pound or 35% decrease in market is primarily attributed to lower mil!tary budgets and the poor sales of new commercial aircraft. The largest percent 'decrease is in the defense aerospace market, but the largest weight decrease is for commercial aerospace. Fig. 1 also shows the estimated market for the next few years. The projected increases are modest and certainly do not approach the 50 million pound mar-
2
S.R. Seagle / Materials Science and Engineering A213 (1996) I-7
Table 1 Recent USA titanium mill products markets Market sector
Defense aerospace Commercial aerospace Non-aerospace Total
Million Ibs (kg)
Change from 1990
Reason for decline
1990
i994
lbs (kg)
%
14.3 (6.5) 26.5 (12.0) 11.9 (5.4) 52.7 (23.9)
7.0 (3.2) 17.0 (7.7) 10.5 (4.8) 34.5 (I 5.7)
-7.3 (-3.3) -9.5 (-4.3) - 1.4 (-0,9) - 18.2 (- 8.2)
-5I
Decreased military budgets
-36
Poor airline sales
- I2
World recession
kets of the early 1990s. They reflect an improvement in both commercial aerospace and non-aerospace markets starting in 1995. The military market is not expected to rebound. The high titanium content in new military airframes such as C-17 and F-22 may help offset further declines in other military spending. The commercial aerospace market is starting to improve in mid 1995. This should be further assisted by the new airplanes such as the Boeing 777 which have high titanium contents. In addition, new non-aerospace uses for titanium continue to be found which should provide further market growth. 2.2. CapaciO'
As recently as the late 1980s, market forecasts projected steady increases in deliveries of commercial and military aircraft. Reliance on these forecasts led to expansion of capacities, including investments in new facilities. Table 2 shows the capacities for sponge production and melting in 1990 arLd 1995. The current World sponge capacity is estimated to be 117 million kilograms (257 million pounds). This is a 25% reduction in capacity since the peak in 1990 as all countries reduced capacity except the People's Republic of China. Europe has no sponge production as a result of the closing of Deeside Titanium in the United Kingdom. Since about one kilogram of spoage is needed for one kilogram of mill product, the current capacity is calculated at over two times current market requirements. The remaining plants are all magnesium-reduced technology. All sodium-reduced titanium plants have now been closed. This technology produced a very high purity product and had the capability of generating low cost powders. Unfortunately sufficient markets did not exist to support these facilities. The FSU dominates the world capacity for sponge, however there is some question on the ready availability of aJl this capacity. About 1.5 kg of ingot product are required to produce one kilogram of mill product. Again the melting capacity is nearly 2.5 times the market requirements. Only a moderate amount of capacity has been closed. Again the
-35
FSU dominates this capacity and the condition and ready availability of this capacity is uncertain. 2.3. Market and capacity impact
With smaller World markets and a large FSU capacity for both sponge and mill products, the current state of the USA industry is very precarious. The consequences of these persistent market conditions for the last four years have included large financial losses, plant closings, consolidations, capacity reduction and ownership changes. Public financial data are available for the three largest USA mill product companies, Tremont, Oremet and RMI Titanium. The book value of the combined US companies has decreased in the past four years from 441 to 186 milliofl dollars. Obviously this cannot continue without dramatic consequences to the USA industry. Additional consolidation may be required if the current market improvement is not sustained or if new applications with sizeable markets are not quickly developed. Although the USA titanium industry has suffered through a severe market entrenchment, most believe that the titanium market has not matured, and titanium with its unique combination of properties is a metal still
20
= o
t~
._o =
90
91
F-1 DefenseAerospace
I
92
93
94 Year []
95
96
Commercial
97
Aerospace
• Non-Aerospace
Fig. 1. USA titanium mill product shipments,
S.R. Seagle / Materials Science and Engilwer#zg A213 (1996) I - 7
3
Table 2 World titanium capacity Country
Former Soviet Union (FSU) Japan USA People's Republic of China Europe (UK) Total
Ingot/slab million ibs (kg)
Sponge million lbs (Kg) I990
1995
1990
1995
200(91) 64(29) 67(30) 6(2.7) 11(5) 348(158)
160(73) 57(26) 34(15) 6(2.7) 0(0) 257(117)
231(105) 50(23) 153(69) 8(3.6) 19(8.6) 461 (209.2)
231(105) 50(23) 131(59) 8(3.6) I8(8.2) 438(198.9)
in its infancy. The metals' outstanding corrosion resistance in most natural environments, particularly sea water, has not been fully exploited. In addition as energy reserves are depleted and we are required to spend more in acquisition cost to obtain energy, titanium's strength-to-weight ratio makes it attractive for both energy extraction as well as use in energy intensive applications. Continued expansion of titanium markets will be possible by exploiting its unique properties while at the same time developing technology to reduce the cost of using the metal. Even in this recent difficult environment many new developments are underway. The remaining portion of this paper will provide examples of the progress in the USA related to improved quality, lower application cost and examples of emerging new markets.
3. Technical developments
5.i. Aerospace Quality During the production of titanium mill products, defects of high melting point metals or compounds occasionally have been introduced through contaminated raw materials. The very hard defects such as WC and nitrogen-rich Type I have proven to be most troublesome and in 1990, in response to the Sioux City incident, the Federal Aviation Agency (FAA) set objectives to eliminate all defects through improvements in both processing and inspection [3]. Prior to 1990 the industry-wide defect rate in rotating billet was greater than four per million pounds. This has now decreased to less than three and is expected to decline further as a result of new developments in hearth melting, vacuum arc melting and sonic inspection. Hearth melting has been pursued as a process having the greatest potential for eliminating high density and Type I defects [4,5]. Since molten metal time can be controlled, the hearth offers the potential to dissolve defects and to separate the high density defects to the bottom of the hearth. Significant progress has been made in developing the technology, however, further
refinement of the process is necessary to assure complete elimination of the defects. The technology at this point in development has not been endorsed by all the engine manufacturers. The conventional technology of three vacuum arc melts (triple melt) has improved in the last few years as a result of more stringent process control and appears at this time to be as effective as the hearth technology for producing nearly defect-free ingots. Realizing that process changes may not totally eliminate all types of defects, improving sonic inspection process was established as a goal by several engine manufactures. A new system termed Multizone has been developed by General Electric Research [6,7]. The system utilizes multiple transducers focused at specific depths or zones. The technology was first implemented and developed on the shop floor at RMI Titanium Company by parallel testing over 500 000 kg of rotating quality billet using both the Multizone and conventional systems simultaneously [8]. For billet diameters up to 254 mm, the Multizone process was able to test to a 0.8 mm flat bottom hole standard while the conventional process was limited to a 50% larger t.2mm standard. Defects such as WC were found using the new technology that were not evident in the conventional inspection. As a result of this effort, improved sonic standards have been implemented recently for rotating quality titanium billets. These quality improvements will assure the continued high usage of titanium in gas turbine engines.
3.2. Aerospace titanium alloys Annealed Ti-6AI-4V has been the predominate titanium alloy for airframe and engine applications. Occasionally new aerospace platforms such as the C-17, F-22 and the Boeing 777 offer the opportunity to introduce new alloys as well as new titanium applications. Several high strength heat treatable alloys are now being used and their properties are summarized in Table 3. Both Ti-10V-2Fe-3A1 and Ti-6-22-22S were developed in the 1960s but are now just starting to see significant commercial applications. Their high strength combined with good toughness are attractive for many airframe applications including landing gears.
S.R. Seag/e / Materials Science and Engineering A213 (1996) 1-7
4
Table 3 High strength aerospace alloys Property
Maximum useful temperature
Alloy Ti-10-2-3
Ti-6-22-22
Alloy C
260
320
650
1170 1070 8 66 Landing gears Deep hardening; High strength
1100 1000 10 82 Airframe components High strength; good toughness
1000 930 20
(c) UTS (MPa) YS (MPa) EL (%0) Application Characteristic
The T i - 1 0 - 2 - 3 is in the C-17 and Boeing 777 and the Ti-6-22-22S is used in the F-22 fighter. All these new planes contain large quantities of titanium in the airframe. The C-17 is 12%, the Boeing 777 is reported to be about 12% and the F-22 is 41% with the T i - 6 - 2 2 22S being 5% [9]. Alloy C is unique because of its resistance to burning and is used in the two-dimensional thrust-vectoring exhaust nozzles on the F-119 engine. The well known titanium gamma aluminides have received extensive technical interest and look very promising for very high temperature applications. However, they have not yet been accepted as a major material of construction because of high cost, low toughness and low ductility. 3.3. L o w cost alloys - - co~'rosion resistant
Crevice corrosion is a major problem in many elevated temperature chloride environments. Traditionally, ASTM Grade 7 (Ti-0.15% Pd) has been recommended for this severe service. The addition of 0.15% Pd nea/ly doubles the cost of titanium and thus makes it unattractive for many applications. More recent work shows that Pd additions at the reduced level of 0.05% are suitable for most applications requiring added corrosion resistance [10,1i]. Furthermore, ruthenium at 0.10% is equally effective for corrosion protection as illustrated in Table 4. Although 0.10% Ru has equivalent corrosion resistance to 0.05% Pd, the ruthenium addition is less costly. The Pd addition increases the cost of commercially pure titanium approximately 30% while similar corrosion protection is achieved for only 10% additional cost with the Ru addition. Noble metal additions are also effective for improving the corrosion resistance of higher strength titanium alloys. As in commercially-pure titanium, the 0.05% Pd and 0.1% Ru addition provide similar improved corrosion resistance in alloys. The Pd version of these alloys were recently given Grade designations by ASTM. The Ru adjusted alloys are a newer development and are
Engine exhaust nozzels High temperature strength; burn resistant
now starting to be seen in commercial activity, Examples of potential applications are shown in Table 5. Ti-6AI-4V-0.01Ru has been selected for production tubulars in high temperature geothermal brines. 3.4. Low-cost alloys ~
h~dustrial applications
Most titanium alloys were developed for aerospace applications without regard for the alloy cost and are often applied in industrial applications because of availability and well known properties. More recently alloys made from less costly alloying elements have been proposed to penetrate markets very sensitive to cost such as automotive. Examples are shown in Table 6. The compositions include both alpha-beta and beta type alloys. The alloys use molybdenum and iron to replace more expensive alloying elements, particularly vanadium. The beta alloy Ti-4.5Fe-6,8Mo-I.5A1 is made from steel-type F e - M o master alloy which is not normally as clean as aerospace master alloys. However, this has not been detrimental to mechanical properties, The high oxygen version of Ti-6A1-4V takes advantage of abundant low-cost scrap. The composition was adjusted to achieve ballistic performance equal to or better than standard Ti-6A1-4V alloy. Theses approaches to alloy design can lower the alloy formulation cost by approximately 20% and hopefully open new market opportunities. 3.5. Low-cost process#zg
Only a small portion of titanium output is processed on efficient high volume mill equipment of the type used in steel industry. The first products to reach sufficient volume were commercially pure (CP) titanium strip followed by welded tubing. The market size allowed for development of these processes. The hearth' melting process developed in the USA and used by A. Johnson Company, Wyman-Gordon and Teledyne A1lvac may be considered the first step in a continuous
S.R. Seagle / Materials Science and Eng#wer#zg A213 (I996) 1-7 Table 4 Effect of Pd and Ru on the corrosion resistance and cost of several titanium alloys in boiling 1% HC1 (mm/yr) Base alloy
Ti (grade 2) Ti-3A1-2.5V (grade 9) Ti-6AI-4V (grade 5) Beta C (grade 19) Relative cost Ti (grade 2)
Typical yield strength MPa
Noble alloy addition, % 0
0.05Pd
0.10Ru
350 550 900 1050
1.82 2.6 2.8 0.2
0 0.01 0.07 0.0I
0.01 0.01 0.08 0.01
350
I
1.28/1.3
1.10/1.1
type casting process for mill products. The electronbeam hearth process is very efficient for producing slab of commercially-pure titanium. More recently, RMI titanium successfully produced a range of large diameter seamless alloy pipe using the Lorain, Ohio, steel processing facilities of the USS/Kobe joint ' venture. Seamless alloy pipe between 250 and 350ram diameter by 37m long with a wall thickness between 19 and 25mm has been produced using the rotary-piercing mill. Although this technology was demonstrated many years ago by U.S. Steel in both the Gary Works and Elwood City Works, market opportunities were not available to take advantage of this low-cost process route. The availability of this low-cost process will allow titanium to compete in several energy related markets. A modified version of Titanium roll-clad steel plate has been developed to significantly reduce the cost of chemical equipment produced from specialty titanium and zirconium alloys [10]. The process consists of roll cladding low cost Grade 2 or 9 backer plate to which a 1.0-1.4 mm thick skin layer of a more chemically resistant titanium alloy (Grade 7 or 12) or zirconium. Recent cost comparisons of Ti/Zr roll-clad plate with solid plate at equivalent thickness indicate a potential cost savings of 15%-25% over Ti-Grade 7 plate and 20%-45% over Zr 702 plate. Casting is a low cost method of making a component. The current lost-wax investment casting process is complicated and labor intensive. Process development work at Howmet Corporation suggests that permanent mold casting of titanium is possible [12]. The advantages include lower cost (40% to 50%), simpler manufacturing process, tighter process control, improved dimensional control, no alpha case and refined microstructures. This process has been demonstrated with both conventional titanium alloys and gamma alloys. The first production castings are now under engine evaluation.
4. New markets 4.I. Energy extraction Titanium alloys have been selected for several new applications because of their combination of properties and competitive cost. Geothermal wells exceeding 460 m can reach temperatures as high as 285 °C in the Salton Sea of Southern California. The traditional material of construction has been low carbon steel which has a life of less than one year. Large diameter extruded pipe of Beta C was first tested in this environment in the 1980s and has performed well. The expected life is greater than 30 years [13]. In the meantime, new design analysis indicates the high strength of Beta C is not required and additional corrosion resistance is desirable. This led to the recent production of Ti-6AI-4V-0.1Ru large diameter (250-350 mm) seamless tubulars as the material of choice' for most recent wells. The combination of low-cost processing combined with a modified, improved alloy assures titanium's competitive edge in this market. Conoco-Norway, Inc (CNI) is developing the Heidrun Field for hydrocarbon production. This field is on the Norwegian Continental Shelf in the northern North Sea, some 120 miles off the mid-coast of Norway. Development of this field utilizes a tension leg platform (TLP) for both drilling and production of hydrocarbons at a water depth of 345 meters. Installation of the TLP is scheduled for late in 1995. The 56 production and ejection wells planned in this field will be tied back to the TLP from the subsea production well template via high pressure production risers. Drilling of these wells from the TLP deck will be accomplished using one high-pressure titanium alloy drilling riser. The drilling riser for offshore drilling has traditionally been a low-medium strength steel alloy, which has been satisfactory for shallow waters (depths below
6
S.R. Seag/e /Materials Science and Engineer#Tg A213 (i996) I - 7
Table 5 Candidate applications for Pd- or Ru-enhanced alpha-beta and beta titanium alloys Application
Applicable alloys containing Pd or Ru Ti-3AI-2.5V
Ti-6AI-4V
Beta C
Wet oxidation Other waste treatments High temperature organic systhesis Hydrometallurgical ore leaching Deep sour gas and geothermal wells Downhole tool and accessories Offshore flowlines, export and catenary r,sers
305 m). Owing to the deeper waters involved at the Heidrun TLP location and the high-pressure drilling design (i.e., topside BOP)~ CNI considered other lower-weight, higher-strength, and easier to handle material alternatives for the dri?ling riser. Given the severe well bay spacing constraints, this drilling riser also required special design considerations to account for riser interference under severe weather conditions. In early 1991, CNI pursued conceptual engineering studies to evaluate the feasibility and practicality of producing and utilizing a titanium alloy drilling riser for this service. These studies confirmed that the titanium drilling riser was indeed a viable option, and offers economic advantages over steel from both an initial and life-cycle cost standpoint. This stems from elimination of costly riser flex joints and syntactic foam buoyancy, as well as reeuction of tensioning equipment size, deck storage requirements, running time, and maintenance with titanium. This evaluation revealed that the high-strength ELI Ti-6AI-4V alloy riser exhibits approximately one-fourth the weight and three times the flexibility of a high pressure steel riser, while offering immunity to seawater corrosion and superior sea water fatigue p~operties. CNI's preliminary engineering studies also indicated that the design process and melhodology for a titanium alloy riser is basically the same as that of a steel riser, permitting expedient engineering to progress for this project. The technology for manufacturing and fabricating (i.e., welding) the titanium alloy riser was deemed available as well, and had been demonstrated in large tubular prototypes such as the Placid Oil riser stress-taper joint produced from the ELI Ti-6AI-4V alloy. Based on all these favorable engineering and cost considerations, CNI purchased a 61 cm OD x 2.2cm minimum wall ELI Ti-6AI-4V high-pressure drilling riser for the Heidrun Field. Total consumption of titanium for this single project was in excess of 115 000 kilograms.
4.2. Consumer applications Consumer applications have not developed at the
rate originally expected when the metal was first industrialized in the mid 1950s. The anticipation then and the hope over the last forty years was to find automotive applications. The automotive manufactures started to look seriously at titanium in the early 1980s. Most of this effort in the USA was focused at Ford Motor Company and consisted of the evaluation of suspension springs, valves and valve springs [14]. The impetus for the work was the mandated fuel economy improvements known as CAFE. Unfortunately, titanium has not been selected for use in any large volume production models and has been limited to a few optional parts on high performance cars and demonstrated in concept cars like the Neon Lite. Although there is a new, well funded, Government sponsored initiative in the USA for light weight automobile materials, this author believes that significant titanium usage will not occur until the CAFE standards are more stringent or until energy prices escalate to the point titanium can be considered cost effective for weight reduction. An exception could be the use of gamma aluminides as valves if a low-cost manufacturing process is developed. Titanium has been used to a minor extent in sports equipment such as skis, tennis rackets and golf equipment. The most surprising new major use is the development of titanium driver golf club heads. Because of titanium's strength-to-weight ratio, the club head can be built larger (250 cc vs. 175 cc volume) without loss of integrity. This allows the manufactures to design a club that is easy to swing, easy to hit straight and more forgiving. The market in the USA is expected to exceed 1400000 kilograms in 1995. All clubs produced in the USA are by investment casting Ti-6A1-4V. This market is expected to grow 20% to 25% per year as the titanium heads move from driver to irons. Titanium golf clubs may be a passing fad. However, in depressed times, a new application is welcome. Numerous other consumer markets including archi" tecture, medical and jewelry have enjoyed modest increases. However, a large single consumer market still evades this metal.
S.R. Seagle I Materials Science and E1~ghzeeriszg A213 (1996) I - 7
7
Table 6 Low-cost industrial titanium alloys Alloy
Cost
YS MPa
Concept
Application
Ti-6A1-4V Ti- 5AI-2Fe Ti-6AI-4V-0.250 "SAT" Ti-4.5Fe-6.SMo- 1.5A1 "LCB"
1 0.82 0.85 0.78
825 825 900 1100
Base Comparison Low-Cost Alloying Elements Low-Cost Scrap Ferro-moly steel Master alloy
Automotive Ballistic Armor Springs. Torsion bars
5. Summary The USA titanium industry appears to be transitioning out of a prolonged 35% market retrenchment caused by reduced military spending and poor commercial aircraft sales. Despite capacity reductions, the world titanium industry still has appreciable excess capacity in both sponge and ingot. Current projections suggest that the market will improve during the last half of 1995 owing to increased consumption in nonaerospace, commercial aerospace and inventory replenishment. The future for titanium is still optimistic as new technical developments and applications are pursued. New low-cost corrosion-resistant and industrial alloys will make titanium more attractive. The development of low-cost processing will also improve the competitiveness of the metal. The application of high strength alloys opens new opportunity in aerospace airframe and engine applications. As titanium becomes more cost-effective, new applications will continue to develop in consumer and energy extraction markets.
References [I] S.R. Seagle. Current and future trends in special materials, IVor/cshop Presentanons on Critical Issues jot the Aerospace Special Materials bz&tstrial Base, National Materials Advisory Board, Washington, DC, JuIy, 1994. [2] P. Bania, Current and future trends in the titanium industry, [Vorkshop Presentations on Critieal Issues for the Aerospace Speeial ~[aterials Dzdustrial Base, National Materials Advisory Board, Washington, DC, July, 1994.
[3] R.J. Koenig, J.G. Costa, R.E. Gonzalez, R.E. Guyotte, D.P. Salvano and T. Smith, Titalziu~12 Rotating Compo~zents Re~,iew Team Report, US FAA Aircraft Certification Service Engine and Propeller Directorate, December I4, 1990. [4] M. Osthelmer and S.R. Seagle, Utilization of electron beam melting in the production of defect free Ti-6AI-4V ingots, Sixth World Coi~jFreneeon Tita~Hum, Societe Francaise de Metallurgie, June 6, 1988. pp. 579-582, [5] C.E. Shamblem and G.B. Hunter, in Cordy and Lherbier (eds.), Titanium base alloys-clean melt process Development, Proc. I'acuum Metallurgy Co~(:, 1989, pp. 3-1 I. [6] P.J. Howard and R.S. Gilmore, Ultrasonic noise and the volume of the ultrasonic pulse, Reciew oJ Progress #7 QNDE, 15, to be published. [7] D.C. Copley and P.J. Howard, in D.O. Thompson and D.E. Chimenti (eds.), Reciew oj" Progress m QNDE, Plenum, New York, 1995, pp. 2145-2151. [8] J.C. Moyers, S.R. Seagle, D.C. Copley and R.S. Gilmore, Multizone sonic testing of titanium billet, Eighth World Co~zjerenee on Titanium, IJ~stitute of Materials, October 22, I995. [9] At,iattot~ If'eek, McGraw-Hill Companies, July 24, 1995, p. 47. [10] R.W. Schutz, Recent titanium alloy' and product developments for corrosive industrial service, I995 N,4 C£ Aimual Meet., Paper No. 244, NIarch 26, 1995. [11] R.W. Schutz and M. Xiao, Optimized lean-Pd titanium alloys for aggressive reducing acid and halide service environments, Proc. I2th Int. Corrosion Congr., col. 3A, September I993, NACE, Houston, TX, p. 1213. [12] N. Paton, Advances in titanium casting technology, Workshop PresentatioJzs otz Critical Issues Jot the Aerospace Special Materials hMustrial Base. National Materials Advisory Board. Washington, DC, July, I994. [13] W.W. Love, C.J. Cron and D. Holligan, The use of Beta Ctm titanium for downhole production casing in geothermal wells, Si.'cth World Col~J'ere~zce on Tita~Hm~7 Proceed#~gs, Les Ulix, France, Societe Francaise de Metallurgie, 1988, p. 443. [14] A.M. Sherman and S.R. Seagle, Titanium coil springs for automotive suspension systems, SAE paper 800481, AutoJtzotzve Engineering, May I980.