Novel Processing Technique for Titanium Weld Wire Jeffrey Schutz

U.S. Army Armament Research, Development and Engineering Center (ARDEC) Dr. Daniel Hennessy

American Engineering and Manufacturing, Inc (AEM) ABSTRACT Welding and prototype fabrication are playing an increasing role towards the implementation of titanium into future weapon systems. Cost continues to be a barrier to entry for insertion of titanium. To help mitigate some of the cost burden, all aspects of the supply chain are examined for potential savings. A recent feasibility study funded by the Defense Metals Technology Center has demonstrated the technology to produce titanium weld wire in a more efficient and cost effective manner, resulting in savings in both dollars and logistics lead-times for the DoD. The key to the success of this program relies on the ability to directly roll a cast titanium structure as opposed to the more conventional method that hot forges very large diameter ingots. INTRODUCTION ARDEC, part of the research arm of the Army Materiel Command, is a comprehensive armaments facility headquartered at Picatinny Arsenal on 6,500 acres in northwestern New Jersey. ARDEC is responsible for supplying 90 percent of the Army’s lethality and provides the majority of lethal mechanisms for other military services as well. ARDEC technical expertise extends to almost all areas of modern warfare: direct fire, indirect fire, and smart munitions; energetics; aeroballistics; battlefield digitization; logistics research and development; lethal mechanisms; fire control; fuzing; small, medium, and large caliber weapon systems; explosive ordinance disposal; environmental assessments, analyses, and studies; and environmental remediation of ordnance and weapon systems. Titanium processes and production equipment ARDEC has adapted and refined various manufacturing methods (welding, casting, forming, powder metallurgy, joining, and machining) to automate processes and improve technologies to make it easier and more cost effective to use titanium in military applications. With its practice of ensuring that designs are manufacturable early in the development process, ARDEC has collected a body of technical information about titanium that has been communicated to the U.S. industrial base in the form of Technical Data Packages (TDPs).

Welding Advances Advances in pulsed gas metal arc welding (GMAW-P), which involve modifying existing practices to optimize them for titanium, have turned welding titanium into a high-productivity automated (robotic) process. Welds can be performed up to ten times faster than the linear travel speed of manual gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding. Welds normally requiring three manual passes can be performed in a single pass. Two waveform templates are used: a single-pulse GMAW-P that uses a 100 percent helium shielding gas and provides good penetration capability; and a “double-pulse” template, consisting of a short duration “exciting” pulse followed by a second peak “detaching” pulse for metal transfer. These improvements yield higher quality, less expensive welds. Additionally, The American Welding Society (AWS) D1.9/D1.9M Structural Welding Code—Titanium was released in July 2007. The code goes beyond the limitations of previous documents by providing the information required to engineer a structural titanium product from start to finish — from design through manufacture and inspection — in the form of a structural code of reference. Furthermore, AWS D1.9/D1.9M Structural Welding Code—Titanium provides a formal method for the development and approval of titanium welding procedures, which, in turn will bolster the reputation of titanium as a usable metal. Design engineers are often reluctant to propose expensive materials, such as titanium, in order to minimize overall cost. However, the true life-cycle cost of the component can have the potential to be lower over the long term. When taking into account costs for fabrication and manufacturing and other costs accrued over the component’s service life, the savings can have the ability to drastically outweigh material costs. This often is overlooked when focusing on the price-per-pound of raw titanium upfront. TITANIUM WELDING WIRE When compared to other high-volume manufacturing materials (steel, aluminum, etc.) the price-per-pound of titanium raw material has been, and continues to be a barrier-to-entry for manufacturing applications.

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Wrought- Lo O2 V1607

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high oxygen cast rod had a considerable number of spikes on its trace. A follow-up visual inspection would characterize these indications as “fingernail defects.” This surface discontinuity has a crescent shape spanning most of the outer diameter. After final drawing, a scanning electron microscope was used to examine the cast and wrought wires, which resulted in no substantial difference in surface features. Images are shown in Figure 3.

Figure 3: SEM Images

Mechanical tests including tensile, hardness, helix, cast, and size variation were conducted to fully characterize the wire. The American Welding Society (AWS) does not have a specification, but rather a guideline of 120ksi minimum for welding Ti 6Al-4V. All wires, high and low oxygen cast and wrought had an Ultimate Tensile Strength (UTS) greater than 120ksi. As expected, the higher oxygen material tended to have a higher UTS. It should also be noted, that depending on the annealing of the wire, mechanical properties can be varied to achieve a wide range of desired strengths. Results are shown in Figure 4.

Figure 4: Wire Tensile Strength

The hardness survey of the wire demonstrated a strong relationship between the low oxygen cast structure and the wrought material with a nearly equivalent profile, as shown in Figure 5. Additionally, the correlation of increased hardness with increased oxygen content is also present. Size variation was measured throughout each wire, and there was little to no variation throughout, and all wires were within specification. Likewise, the helixes of the wires

were measured and were all within specification. Results are shown in Figures 6 and 7 respectively.

Figure 5: Wire Hardness

Figure 6: Wire Size Variation

Figure 7: Wire Helix

The final mechanical test was to measure the cast of the wire. The 0.045” wire was within specification for both the cast and wrought material; however for the 0.035” wire, both low oxygen wires, wrought and cast, were below specification. To examine the wire further, each wire was placed through a straightener on a welding machine. The cast improved by approximately 6x. Results are shown in Figure 8.

Figure 8: Wire Cast

To complete the evaluation, the welding wire was welded using Gas Metal Arc Welding (GMAW) on plate, shown in Figure 9. The resultant mechanical properties were compared for each welding wire used. The low oxygen wire both wrought and cast produced similar properties. When examining the chemistry of the weld metal, the oxygen levels increased to 0.14% for the low oxygen wrought and 0.11% for the low oxygen cast material. The increase can be attributed to a pick-up of oxygen during the welding process.

Figure 9: Welded Plate

CONCLUSION The Army continues to seek titanium processing advances that lower cost and make titanium more readily available to current and future weapons systems. The goal of the study was to investigate the manufacturability of titanium weld wire starting from a 4” cast structure. The properties examined including material efficiency, grain structure, surface finish, and all mechanical properties showed no discernable differences between the wrought and cast structure of the starting billet. The results presented show a viable alternative to the current manufacturing practice of titanium welding wire.

CONTACT Jeffrey Schutz Materials Engineer Materials, Manufacturing and Prototype Technology US Army ARDEC; Building 60 Picatinny Arsenal, NJ 07806-5000 P(973)724-5333 F(973)724-4525 jeffrey.schutz@us.army.mil Dr. Daniel Hennessy Project Manager/Metallurgist American Engineering and Manufacturing, Inc. 8085 Leavitt Road Amherst OH 44001 P(440)986-4400 F(440)986-4405 dan.h@aemi.us www.aemohio.com

U.S. Army Research, Development and Engineering Command

Novel Processing Technique for Titanium Welding WireJeffrey Schutz

16 September 2009

yDr. Daniel Hennessy

ARDEC at a Glance

• ARDEC (all sites) ~ 3098• Picatinny Arsenal = 2648• Benet (Watervliet Arsenal) 240Benet (Watervliet Arsenal) = 240• Rock Island Arsenal = 145• Adelphi & APG = 65• S&E average 20 years experience – more than 30,000 man-years of highly specialized experience in critical multidisciplinary field (no commercial equivalent)• S&E new hires from April 99 to January 07 = 994

• Intellectual Property (FY07): • Invention Disclosures – 49 • Patent Applications – 30• Patents Issued – 13• Patent License Agreements = 13

Providing the lethality technology for over 90% of the Army’s munitions

Patent License Agreements = 13• Growth and success through Cooperative Research and Development Agreement (CRADA) = 159• World recognized armaments authority

Why the Army needs Titanium

• New Army objectives require weapon systems and vehicles that have high:

T t bilit– Transportability– Maneuverability– Survivability

• Titanium is playing a critical role in this revolutionary change by: – Meeting new system performance characteristics

Highest strength to weight ratio over any other conventional metal such as– Highest strength-to-weight ratio over any other conventional metal such as steel or aluminum which allows designers to achieve the lowest weight possible in a design

Cost Barriers

• Army requires lower costs than current technology supports– Existing titanium material costs are high compared to Army’s traditional

materials

• The Army needs:– Lower cost material– Loser cost fabrication processes– Reduced manufacturing time for parts

• Defense Metals Technology Center– Conducted feasibility study and funded effort to compare direct rolling of a

cast structure versus conventional wrought structure

Cast vs. Wrought Test PlanCast vs. Wrought Test Plan

Two 8” High O2Cast Ingots

Two 5” Low O2Cast Ingots

Two 4” Low O2Wrought Billets

Machine to 4” Diameter

Weld High to Low

Roll Three Billets to 0.343” Rod

f dSurface Prep Cast Rods

Hot Wire Draw/Anneal to 0.196”

Cold Wire Draw/Anneal to 0.060”, 0.045”, & 0.035”

Weld 0.5” Ti Plate with 0.035” Ti Wire

Cast Ingots & Wrought Billets

Two 8” High O2Cast Ingots

Two 4” Low OTwo 4  Low O2Wrought Billets

Two 5” Low OTwo 5  Low O2Cast Ingots

Machined & Welded Bars

Machine to 4” Diameter

Weld High O2 to Low O2

Rolled Rod

R ll Th Bill t t 0 343” R dRoll Three Billets to 0.343” Rod

Wire at Final Diameter

Finished Wire at 0.045” & 0.035”

Welded Plates

0.5” Titanium Plate Welded with 0.035” Ti Wire

Final Size Wire

G&S Mil tag Source Identification Heat # Diameter Quantity Oxygen (%)

Final Produced Quantities

tag y yg ( )

42147 A Picatinny Cast - Hi O2 Y065641 60 mil 10 lbs 0.2342772 B RMI Cast - Lo O2 XH8010 60 mil 10 lbs 0.053/0.06042148 C Picatinny Cast- Hi O2 Y065680 60 mil 10 lbs 0.2542175 F Metalwerks Wrought- Lo O2 V1607485 60 mil 10 lbs 0.06

G&S Mil tag Source Identification Heat # Diameter Quantity Oxygen (%)

42772 B RMI Cast - Lo O2 XH8010 45 mil 41 lbs (5 spools) 0.0442147 A Picatinny Cast- Hi O2 Y065641 45 mil 74 lbs (7 spools) 0.2342148 C Picatinny Cast- Hi O2 Y065680 45 mil 174 lbs (17 spools) 0.2542175 F Metalwerks Wrought- Lo O2 V1607485 45 mil 124 lbs (11 spools) 0.06

G&S Mil tag Source Identification Heat # Diameter Quantity Oxygen (%)

59 S l 596 P d

tag42147 A Picatinny Cast- Hi O2 Y065641 35 mil 59 lbs (6 spools) 0.2342771 D RMI Cast - Lo O2 XH8011 35 mil 53 lbs (5 spools) 0.0542175 F Metalwerks Wrought- Lo O2 V1607485 35 mil 31 lbs (4 spools) 0.06

59 Spools – 596 Pounds

Productivity

Comparable Production between Test and Control

Characterization Testing

– Cast Ingot Grain Structure– Rolled Bar Grain Structure– Rolled Rod Eddy Current– Finished Size Tensile Strength– Finished Wire Hardness Profile– Finished Wire Hardness Profile– Finished Wire Size Variation– Finished Wire Cast– Finished Wire Helix– Finished Wire Surface (SEM)– Welded Plate Section Tensile Strength– Welded Plate Chemistry

MaterialChemistry

Low Oxygen Cast (RMI)

High Oxygen Cast (Picatinny)

Heat # Grade O2 %

V1607485 6Al-4V 0.06

Low Oxygen Wrought (Metalwerks)

Cast IngotGrain Structure at Surface

Low O2 Cast  High O2 Cast            Low O2 Wrought 

Low O Cast High O CastLow O2 Cast  High O2 Cast          Cast “well defined” acicular alpha; Wrought “worked”

Turned/Welded IngotX-Ray Analysis

4”

No Detectable Defects in Weld Regiong

Rolled Bar1.5” Dia Grain Structure (Mid Radius)

Low O2 Cast  High O2 Cast            Low O2 Wrought

Low O2 Cast  High O2 Cast          Low O2 Wrought  2 g 22 g

Comparable Structure mid‐way in Rolling

Rod TestsRolling Eddy Current Test

Low O Wrought Billet Low O Wrought BilletLow O2 Wrought Billet Low O2 Wrought Billet

Low O2 Cast High O2 Cast Billet

Low O2 Cast High O2 Cast Billet

Rod TestsRolling Eddy Current Test

Fold (Finger Nail) Defects – High O2

Wire TestsTensile Strength

All Wire Above AWS minimum “Guideline”

Wire TestsHardness Profile

Hardness Correlates with Oxygen ContentTest (Low O2) and Control are Equivalent 

Wire TestsSize Variation

Size meets Specification

Wire TestsHelix

60 mil HelixCast ‐ Hi O2 0.19”, 0.19”                    Cast ‐ Lo O2 0.25”

Helix within Specification

Cast  Lo O2 0.25  Wrought‐ Lo O2 0.25” 

Wire TestsCast

After Straightenedin Welder

60 mil CastCast ‐ Hi O2  28”, 23”                    Cast ‐ Lo O2 34”Wrought‐ Lo O2 26” 

35 mil Cast below Specification for BOTH Test and ControlControl

Finished Wire Surface0.035” Diameter

Low O2 Cast Low O2 Wrought

Comparable Surface after Wire Drawing

Finished Wire Surface0.035” Diameter

High O2 Cast           Low O2 Wrought – 2nd Control 

Comparable Surface after Wire Drawing

Welded Plate TestsTensile Strength

“Wrought” and “Cast” Lo O2 Comparable

Welded Plate TestsChemistry

Rise in Oxygen Content Observed

ARDEC Usage

From: Picatinny Arsenal, Welding & Fabrication shop:

“…G&S Titanium welding wire…welds just as good, maybe even runs a little better then the wire we normally buy. As soon as the titanium seats come down, we will put it into full production ”we will put it into full production…”

At Pi ti A l 25 HMMWV t d i j t d 2 lb fAt Picatinny Arsenal, 25 HMMWV seats were made, using just under 2 lbs. of G&S wire

Summary

• Goal to Investigate “Manufacturability” of Starting 4” Diameter Titanium bar with Cast Structure”C d L O i i h Hi h O• Compared Low Oxygen concentration with High Oxygen

• Rolled 4” Billet to 0.343” Rod; Drawn to 0.035” Wire• Welded ½” Titanium plate• Material Efficiency of Cast Comparable to Wrought (Control)• Equivalent Grain Structure at 1.5” Diameter• Similar and Acceptable Surface at Finish Size (0.035”)• No Discernable Difference in Physical and Mechanical Properties• Comparable Tensile Properties of Welded Plate Sections• Wire tested in welding ½” titanium plate• Wire used in US Army Humvee seat application at Picatinny Arsenal

Conclusions

• The goal to validate the metallurgical concern of deforming titanium bar having a “cast” (grain) structure compared to conventional “wrought” structure was achievedachieved.

• This investigation has demonstrated the “Manufacturability” to directly roll a cast titanium ingot not having been previously (hot) forged from a larger cast diametertitanium ingot not having been previously (hot) forged from a larger cast diameter.

• Cast titanium was hot rolled, drawn to wire, and tested successfully in titanium welding applications.welding applications.

Acknowledgements

• American Engineering & Manufacturing– Dr. Daniel Hennessy– John Lawmon

• Defense Materials Technology Center– Charles Clark

• G&S Titanium– Roger Geiser– Mitch Bowers– Keith Strother

• US Army ARDEC– Michelle Malham