• INNOVATIONS:
  Spectore Turns Ordinary Titanium into a Black-Ti™ Affair
  
  
• CASE IN POINT:
  ATI 425™: A New 130 ksi UTS Alloy for Pressure Vessel Applications — ASME Code Case 2532
  
  
• CORROSION SOLUTIONS CONFERENCE:
  Corrosion Conference Draws Attendees from Around the World
  
  
• TECHNICALLY SPEAKING:
  Heat Treating Fabricated Reactive Metal Equipment
  
  
• PEOPLE:
  On the Move at Wah Chang
  
  
• ALLEGHENY LUDLUM IN THE NEWS:
  Alloy Substitution — The Switch Is On™
  
  
• INFORMATION

It wasn’t long ago that most people primarily associated titanium with aerospace, medical, golf, or industrial applications; either that or they had never heard of the metal at all. Play a word association game with someone other than a metallurgist or an engineer, throw out the name “titanium”, and you might just get a blank stare.

My how a little bit of time changes things. Today, titanium is so popular that its name is on everything from plastic credit cards to high end watches. Though demand for titanium is skyrocketing and its price per pound is tagging along, innovators are not shying away from trying the lightweight, high strength metal in new applications.

The name titanium comes via the Titans of Greek mythology, known for their extreme and superior strength, an attribute the metal shares. Titanium belongs to a category of elements known as refractory metals. One of the more outstanding characteristics of these materials lies in the refractive properties inherent to their oxides. By applying heat or electricity, one may unleash its refractive properties, inducing various oxide thicknesses on the material surface. According to artisans, “the resulting titanium oxide causes an optical interference with a purity and vivacity much the same as witnessed in the luminescent colors of oil on water, a peacock’s feather, or a rainbow.” It’s an element that’s helped take technology to the depths of the ocean, the far reaches of the solar system and has elevated capabilities in medicine, industry and science. Some believe that titanium has positively and diversely impacted mankind more than any single element in history.

Edward Rosenberg is one such believer. Founder and President of Spectore Corporation, Rosenberg has managed a rare feat. He has captured jewelry industry market share, taking shelf and cyber space from other precious metals sold in brick and mortar stores as well as online. Spectore’s Black-Ti™, part of the company’s Edward Mirell line, and gray titanium jewelry have gone mainstream, finding their way onto the fingers, necks, and wrists of men and women around the world.

Rosenberg’s passion for anything titanium combined with his frustration over an industry that he says had grown stale and complacent, drove his desire to introduce a new noble element into fine jewelry manufacturing. “Titanium is more than another material; it is an entirely new and exciting category,” he explains. According to his web site, spectore.com, “titanium would become the first such element to define an entirely new category of fine jewelry material in almost 3,000 years.”

The truth of the matter is, Rosenberg didn’t just stumble on the idea. Jewelry is in his lineage. “My family has been in the jewelry business since the early 1900s,” says the 3rd generation jeweler/entrepreneur. “My father was a master jeweler in Austria. He came to America and opened his business in New York in 1924. My entire family is or was in the jewelry business.

“I really didn’t want to be in the jewelry business. I wanted to be an artist and a musician. I wanted to create masterpieces. The jewelry business like so many others was becoming commoditized. The art was secondary.” It was the lure of something new, something different that ultimately kept him in the business. “Had I not discovered and committed myself to developing titanium as a new material, I would surely have pursued a career outside of jewelry,” he says.

In 1983, Rosenberg conceived Spectore, the masterpiece he had always imagined creating. “Our sole focus was and continues in the development of the artistic properties unique to titanium,” he says. “Spectore Corporation is unquestionably the innovator and world leader in aesthetic titanium technology. We are the only titanium company solely dedicated and equipped to create the broad diversity of products needed to fulfill an entire merchandised titanium category. Our history in working with notable clients worldwide (a list populated with names like Tiffany & Co.) has allowed us to develop and manufacture an extensive variety of quality titanium products. Our strategic partners are a veritable “who’s-who” of corporate giants, including many Fortune 500 companies.”

As deeply committed as Rosenberg is to his clients, he has never lost focus on what kept him in the family business in the first place: the alchemy of the whole process; the blending of science and art to come up with unique, exotic products. “In order to fully realize our potential we have committed ourselves to consummating the marriage of art and science and developing the creative and technical mindset of each faction as one,” as he explains it. “This has proven no easy task. Neither the artist nor the scientist has the patience or understanding that allows either participant to recognize, appreciate, or value the infinite possibilities such a union could place before them. What is even more amazing is that these barriers exist through the mutual respect and admiration of what each perceives in the other as being foreign. As the jewelry industry embraced titanium, so has the titanium industry begun to recognize the direct value and rewards resulting from their involvement in consumer products.”

Embracing the idea of turning titanium mill products into jewelry on a mass-market scale is one thing; turning the idea into a real, marketable product is something altogether different and exponentially more difficult. Many have dabbled in the business, and some still manufacture product out of their basements. In contrast, Spectore operates out of a 36,000 ft2 facility in Deerfield, Florida that is home to Rosenberg’s scientists and artists as well as millions of dollars worth of state-of-the-art equipment.

It’s a challenging business in more ways than one. “I equate working with titanium to the surfer thinking that a tidal wave is the ultimate ride. What doesn’t kill you...,” jokes Rosenberg. “It is far more difficult to work with than all other jewelry materials, yet offers the most dynamic aesthetic opportunities if in the proper hands. Unlike other titanium producers, we must be proficient and have the capability to produce in the full spectrum of manufacturing possibilities and perform efficiently in a fast changing fashion driven market. Our clients expect “new collections” three to four times a year. Yes there is a learning curve…in fact there is a new one nearly every day.

“When we decided to create the first commercial line of consumer products almost 30 years ago, titanium technology was primarily focused on the aerospace industry. There was little or no information available for net shape mass production.

“Almost every process we employ today was developed within our company. We offer the broadest scope of manufacturing capabilities in the world. Amongst our core competencies, our technology pallet includes machining, forging, casting, powder metallurgy, forming, welding, anodizing, milling, engraving, and a host of other processes (many of which are proprietary).”

Though working with titanium poses many challenges, Rosenberg says that it has been well worth the considerable effort. “Titanium’s high strength-to-weight ratio coupled with its high level of biocompatibility makes it an ideal choice as a jewelry material,” he says, then boldly adds: “I believe that had titanium preceded gold and platinum in the jewelry industry, the other materials would have had a difficult time routing themselves as a popular alternative. Titanium also offers the broadest scope of possibilities for design. Not only can the material be transformed by anodizing to create a myriad of pure optical colors, its structural integrity at low weight offers a broadened scope of architecturally inspired design options with unsurpassed comfort.”

According to Rosenberg, few elements offer the depth and breadth of possibilities that titanium presents. “Its natural resemblance to platinum and the expansive spectrum of anodized colors and finishes offer an unsurpassed diversity,” he says. “Coupled with the virtues inherent in the material, titanium has repeatedly proven its superiority in product and industry. Titanium is the only element offering this unique combination of beauty, strength, reduced weight, and bio-compatibility.

“Aside from the aforementioned virtues, unique to titanium is the superior durability to conventional jewelry materials,” he explains. “Platinum, gold, and silver are soft and heavy. They mar easily, deform, and wear poorly. Designs blur with time and wear. Pins wear and break, clasps get loose. Titanium is far more durable and comfortable than any conventional or other jewelry material.”

Spectore specifies a few different alloys for its products. “For our gray products, we use CP Grade 2 titanium,” says Rosenberg. “It offers the best balance of purity and hardness. It also offers the jeweler the ability to engrave and cut off rings with conventional jewelry tools. Grade 2 also works best with a broad variety of finishes and works well in machining, forming, stamping, casting, and striking. Our Black-Ti™ line is an alloy that, by nature of process, forms an extremely hard black ceramic finish yet maintains sufficient ductility to allow for tension setting (as does the CP)."

The optimistic entrepreneur sees a lustrous future for titanium jewelry. “I believe that the possibilities alone and in combination with other stones and materials are as infinite as our imagination,” he says. “I don’t believe we have scratched the surface of possibilities in product applications in and outside of jewelry and accessories. “As we enter 2006, with the multitude of endorsements from notable retailers, personalities, and industries, we anticipate escalated demand for our products and technological advancements. We are committed to advancing our brands through our strengths in innovation both in design and capabilities. We look ahead to continued growth and market penetration. We are also planning to further expand our product offerings into other consumer products arenas. We will continue to meet consumer expectancy for titanium products in the future. Titanium is an accepted jewelry material that is not only here to stay, it has only just begun to take its rightful place as a jewelry material alongside gold and platinum.”

If it’s not obvious by now, Rosenberg is absolutely passionate about his business — it’s his angel and his demon. “I love to create and watch things grow,” says the dynamic innovator. “First is not just a place, it is a state of mind and a commitment to achievement. I have a long list of the “next things” we want to build and introduce. I doubt I will see them all to fruition, but I promise I’ll give it a go. The problem, or blessing (depending on how you look at it), is that I keep adding more to the plate.”

What a 1st century sage once observed seems to hold true today, at least in the case of Edward Rosenberg: “The artist finds a greater pleasure in painting than in having completed the picture.” In fact, he’s having the time of his life.

For more information about Spectore’s titanium jewelry, visit them online at www.spectore.com.

Introduction

ASME Code Case 2532, for the first time, allows for a truly high strength alloy, ATI 425™ (United States Patent Number 5,980,655 granted November 9, 1999) in ASME pressure vessel construction. With allowable stresses up to 30 to 40% higher than Grade 9, this new 130 ksi UTS proprietary material significantly alters the economics of solid titanium compared to clad steel, particularly for higher pressure and temperature applications. The Section VIII, Division 1 Code Case has the potential to reduce the cost of titanium process equipment compared to conventional grades and even medium strength Grade 9.

While the current Code Case is limited to 600ºF, work is underway to develop data to allow an increased maximum design temperature of at least 700°F and to develop a separate external pressure chart to take full advantage of the material properties.

Corrosion enhanced grades containing either palladium or ruthenium can be produced and could be readily added to the Code Case if an application called for them.

Background

Titanium alloy ATI 425 (Ti-4Al-2.5V-1.5 Fe) was originally designed as a low cost armor alloy. The low cost resulted from use of higher scrap recycle and substitution of iron for vanadium in ingot production. In addition, the alloy can be cold rolled, reducing cost of alloy sheet materials substantially.

However, high strength, good weldability, formability, and ductility led to consideration of the grade for pressure vessel construction.

ASME Code Case 2532 (ATI 425)

ASME Code Case 2532 was approved by the Board on Pressure Technology Codes and Standards on October 27, 2005.

The Section VIII Code Case has the potential to reduce the cost of titanium equipment fabricated from solid titanium and will significantly change the pressure temperature conditions where solid titanium construction is more economical than titanium clad steel.

The chemical and mechanical requirements of ATI 425 are as shown in Tables 1 and 2. The Code Case refers to ASME Grade 9 product specifications and covers all wrought products as listed in Table 3.

The maximum allowable stress values allowed in the Case are shown in Table 4A or 4B and plotted graphically along with corresponding values for Grade 9 and other titanium grades allowed in Section VIII in Figure 1. Design Allowable Stresses allowed for ATI 425 for Code Case 2532 are 25-40% higher than for Grade 9.

Code Case 2532 material was assigned to External Pressure Chart NFT-1 (Grade 3) of Section II, Part D, the same as was being used for Grade 9. However, a separate EPC for Grade 9 (NFT-4) was approved in November 2005 and Code Case 2532 will be assigned to it in the next few months, until a separate chart is completed that will take full advantage of ATI 425’s higher properties.

All other rules for Section VIII, Division 1 applicable to titanium must be met.

To use the Case, Code Case 2532 must be referenced in the documentation and marking of the material and must be shown on the Manufacturer’s Data Report. Thus, ATI 425 material for pressure vessel applications should be ordered to the requirements of Code Case 2532.

Higher Allowable Design Temperature

The 600°F limit on the Maximum Design Temperature is based on the similarity to Grade 9. Allowable Stresses for the material were based on new elevated temperature tests conducted to 800ºF by Wah Chang. Ongoing work will provide Creep and Creep Rupture Tests with the objective of providing data for temperatures to at least 700°F. ATI 425 retains considerable strength at higher temperatures, and a higher maximum use limit could be considered.

Welding Filler Metal

Code Case 2532 requires separate welding qualifications.

It is expected that ATI 425 will eventually be assigned to the P-55 group along with Grades 5 and 23.

A matching filler metal composition is being proposed as ER Ti-38 to be added to AWS A5.16-200X (ASME SFA 5.16). Several other changes proposed should provide incentive for AWS to revise the specification in 2006. The filler metal composition is identical to the base metal composition except the upper limit of the oxygen has a maximum of 0.27 weight percent.

UNS Numbers and ASTM Specifications

ATI 425 has been proposed to ASTM as Grade 38 and is expected to be added to all ASTM Specifications (including castings) in 2006. UNS Number R54250 has been proposed to SAE for the base metal and R54251 for the corresponding filler metal.

Corrosion Performance

Wah Chang is testing ATI 425 in a number of common environments. Corrosion performance is expected to be similar to Grades 9 or 5. Users may wish to contact Wah Chang’s Corrosion Services Laboratory for specific data on tests run to-date or for assistance or coupons for testing.

The material could be produced in both 0.15 or 0.05 palladium or 0.10 ruthenium corrosion enhanced grades. Commercial specifications and amendments to the Code Case 2532 can be proposed.

Applications of the Code Case

Pressure vessels for higher temperature and pressure applications, such as metallurgical autoclaves and some vessels now economical only when constructed of titanium clad steel, are primary candidates for ATI 425.

Both seamless and welded pipe could be produced form ATI 425, and as for pressure vessels, piping for higher pressure and temperature combinations should be considered for ATI 425.

Pre-publication Copy of Code Case 2532 available from Wah Chang
Code Case 2532 will be published by American Society for Mechanical Engineers, Boiler and Pressure Vessel Code, Three Park Avenue, New York, New York 10016-5990 in the next Addenda to Code Cases. In the interim, a copy of the Code Case and an authorizing letter from ASME are available from Wah Chang.

For more information about ATI 425 for pressure vessel applications, contact Jeff Kerr at jeff.kerr@wahchang.com or reach him by phone at 541-812-7057.

ATI Wah Chang’s fifth biennial Corrosion Conference drew more than 200 attendees from 21 countries. The event, which featured technical sessions as well as an exhibit hall and evening receptions, took place September 12-15 at the Sunriver Resort near Bend, Oregon.

The 2005 conference provided industry with the latest information concerning corrosion challenges, materials, engineering and fabrication issues as well as other processing-industry-related information. Allegheny Technologies companies Allegheny Ludlum, Wah Chang, and joint venture partner Uniti Titanium were all represented at the event. Also in attendance were representatives from ATI Australia, China, India, Japan, Korea, Singapore, and the United Kingdom.

Meeting highlights included keynote speeches by Dr. Jack Shilling of Allegheny Technologies (Trends in the Selection of Specialty Materials for Corrosion Applications), Gene Liening of Dow Chemical (Changes in the Chemical Industry and What it Means to You), Joseph Chang of Chemical Market Reporter magazine (Capital Investment Cycles), Dr. Michael Renner of Bayer (New Trends in the Supply Chain for the Chemical Processing Industry), and Don Want of W.E. Smith Hudson (Alloy Material Pressure Vessel Design Aspects). In all, the well-rounded conference featured 43 excellent presentations and 4 panel sessions on topics ranging from Advances in Tubing Technology for Chemical Applications (Andy Nichols, ATI Wah Chang) to Inert Gas Shielding and Purging for Welding Titanium and Zirconium (Jim McMaster, MC Consulting).

During a Wednesday evening reception, ATI Wah Chang honored Conference Keynote Speakers as well as Session Chairmen McMaster, Neil Henry of ABB Eutech, Brian Fitzgerald of Exxon, Joseph Chang of Chemical Market Reporter magazine, Clive Breeden of BP Amoco, Mike James of DuPont, and Rob Henson of Uniti. In addition, Technical Chairman Rick Sutherlin and Meeting Planners Sheryl Renzoni and Rory Bausch-Headly of ATI Wah Chang were recognized for their outstanding efforts.

Wah Chang would like to thank the following exhibitors who supported the Corrosion Conference:

Events included a golf scramble organized by Wah Chang’s Mike Angell and Doug Brenizer. Surprisingly, Angell’s team, which also included Bob Gill (Ellett Industries), Mike James (DuPont) as well as John Deily (AT&F Advanced Metals), took first place at nine under par.

Several other highlights, including a reception hosted by Tico Titanium and a freestyle dance by Pierre Mayer of Marphil to the music of The Booher Brothers, made the 2005 conference an event to remember. In fact, 82% of attendees who completed an event survey rated the conference excellent (with the remaining 18% rating it good), and 97% of the respondents said they planned to attend again.

Speaking of which, plans are already underway for the 2007 event. Keep corrosionconference.com bookmarked and check back often for updated information. Participate in the online poll to provide us with your feedback about the event. We value your input.

For direct questions regarding the Corrosion Conference that aren’t answered online or to offer suggestions, please contact Conference Manager Kirk Richardson at kirk.richardson@wahchang.com. We look forward to seeing everyone again in 2007.

BY: RICHARD C. SUTHERLIN — ATI Wah Chang

Equipment fabricated from titanium and zirconium has been used for over 40 years in the chemical and petrochemical industries. These materials have been chosen for a wide range of applications due to their excellent resistance to acids, salt solutions, caustic and organics. Zirconium equipment is commonly used in hydrochloric, sulfuric, acetic, formic, nitric and urea applications as well as caustic environments. Titanium, on the other hand, is commonly used in seawater applications, mineral processing, and some organic media and in weak oxidizing hydrochloric acid and sulfuric acid environments.

Zirconium and titanium can be fabricated, welded, and machined using standard equipment and processes that are used for more common metals with a few additional considerations. Fabricators use reactive metals in the manufacture of many types of plant equipment, including heat exchangers, columns, reactor vessels, pumps, piping, valves, trays, fasteners as well as other types of ancillary equipment. Reactive metals are required to be heat treated in certain instances to improve their corrosion and mechanical properties.

This article describes the metallurgy of zirconium and titanium and covers the cases where heat treatment is required or desirable when using titanium and zirconium. It also addresses the types of heat treatments used, precautions prior to and during heat treatment, and the surface appearance of reactive metal equipment after heat treatment

Metallurgy of Zirconium and Titanium

Zirconium Grade 702 has a hexagonal close-packed structure at room temperature which transforms to a body centered cubic structure at approximately 865ºC (1590ºF). Zirconium Grade 705 is a two-phase alloy of hexagonal close-packed + body-centered cubic structure at lower temperatures which transform to a body-centered cubic structure (beta) above 854ºC (1570ºF).

Titanium (commercially pure) has a hexagonal close packed structure (alpha) at room temperature which transforms to a body-centered cubic structure at temperatures of approximately 910ºC (1675ºF)

Heat Treatment of Zirconium and Titanium Equipment

Although there are a number of different definitions for heat treatment shown in the dictionary, only a few are applicable to reactive (commercially pure) metals shown in Exhibit 1[1]. Typical heat treatment processes for reactive metal equipment used in corrosion resistant applications include the standard processes of stress relief and full annealing. These heat treatment processes, however, are performed for different purposes as will be described later. Table 1 shows typical heat treatment parameters for zirconium and titanium.

Heat Treating Considerations

Physical and Mechanical Properties

The physical and mechanical properties of the reactive metals should be taken into account when they are heat treated. These considerations include the reactivity (or pickup of interstitial elements) of the materials, thermal expansion differences, thermal conductivity, modulus of elasticity and whether the material may go through a phase change (beta transus) during heat treatment.

Zirconium and titanium surfaces are very reactive when exposed to elevated temperatures. Both will form thicker oxide films on the surface depending on the temperature and exposure time. It is extremely important that the furnace cleanliness and atmosphere are acceptable for reactive metals in addition to proper cleanliness of the zirconium and titanium surfaces.

Thermal properties of zirconium and titanium are somewhat different than that of other materials. The thermal conductivity of zirconium and titanium is similar or better than that of austenitic stainless steels. Table 2 shows a comparison the thermal properties of common materials. The thermal expansion coefficients of zirconium and titanium are much less than that of common stainless alloys, a property which must be taken into account during fabrication. For example, if a heat exchanger with zirconium or titanium tubes is placed in a furnace and the heat exchanger utilizes a carbon steel or stainless steel shell, an expansion joint on the shell would be required to account for the differences in thermal expansion of the reactive metal and carbon steel/stainless steel.

Zirconium and titanium alloys also have a much lower modulus of elasticity (about half that of stainless steel or carbon steel), which must be taken into account during design and heat treatment. Low modulus of elasticity will require that the materials be better supported in the design as well as at the elevated temperatures used during heat treatment.

Finally, if a component is heat treated, possible phase changes should be considered. Finished zirconium and titanium equipment is not typically heat treated near or above the beta transus temperature. Heating the final equipment above the beta transus should be avoided due to potential detrimental metallurgical effects. Table 3 shows the beta transus temperatures of zirconium and CP titanium alloys.

Heat Treatment Requirements for Reactive Metals

Zirconium and titanium (commercially pure) are typically provided by the mill producer in the fully annealed (mill annealed) condition. When the materials are fabricated into vessels or components, it is sometimes necessary to heat treat the materials and enhance the mechanical properties to improve corrosion resistance. One example of where a heat treatment is required may include the stress relief for reduction of residual stresses when two plates are welded together for press forming into large cylindrical heads. This may result in improved final formability of the head. Also, stress relief may be required after head forming just prior to forming the flange to reduce the stress caused by the working of the head.

Stress relief of highly formed pipe may also be advantageous for rolled and welded pipe or formed fittings to reduce the residual stresses caused during forming. It may also be desirable to perform stress relief of a machined part prior to the final machining passes, especially if tight final tolerances are required.

Heat treatment of reactive metals may be needed for improvement of fracture toughness or fatigue strength. Heat treatment will also increase the erosion, abrasion and galling resistance of zirconium alloys. For zirconium alloys it is necessary to heat treat the welds if placed in the higher temperature and higher concentrations of sulfuric acid. Where the reactive metal has susceptibility to stress corrosion cracking in certain media, a stress relief anneal is an important step to mitigate the tendency for stress corrosion cracking to occur.

Zirconium Heat Treatment for Improved Corrosion Resistance

Stress relief of zirconium is sometimes required for improved corrosion properties. Zirconium is susceptible to stress corrosion cracking in some media. These media include ferric and cupric chloride solutions, pure methanol, methanol + HCl, methanol + I2, dry organics, concentrated nitric acid, 64-69% sulfuric acid, liquid mercury and liquid cerium. Of these identified media, only in concentrated nitric acid and 64-69% sulfuric acid can the tendency for stress corrosion cracking be reduced by a stress relief anneal. A final stress relief will reduce the residual stresses in the final equipment thereby removing one of the factors required for stress cracking to take place.

Stress relief anneal on zirconium does not affect the mechanical properties of zirconium parent metal or welds. Stress relief of zirconium can occur at temperatures as low as 538ºC (1000ºF) and temperatures as high as 620ºC (1150ºF). Typically, zirconium is stress relieved at 550ºC (1025ºF) for •hr per 25mm (1") of thickness. Zirconium Grade 705 welds are susceptible to delayed hydride cracking if the welds are not heat treated within a certain period of time. All welds of Zirconium Grade 705 must be stress relieved to prevent the susceptibility to delayed hydride cracking. Figure 1 shows a photomicrograph of a Zr705 weld with delayed hydride cracking[2].

Zirconium has excellent resistance to sulfuric acid at concentrations from 0% to 70% at well above the boiling temperature. Zirconium welds exposed to sulfuric acid at particular concentrations and temperatures, however, will be preferentially attacked and must be heat treated. Figure 2 shows an iso-corrosion curve of zirconium in sulfuric acid and the weld limit line where the post weld heat treatment is recommended. A primary reason for the lower corrosion resistance in the weld area and heat affect zone is the distribution of second phase or intermetallic particles in the grain boundaries.

When the weld cools, the intermetallic compounds concentrate in the grain boundaries forming a continuous path for corrosion to propagate. Heat treatment can be performed which disperses and agglomerates the second phase particles thereby eliminating the continuous network[3,4]. Heat treatment will eliminate preferential attack and result in the corrosion resistance of the weld area and heat affected zone being similar to that of the parent metal. In order to reduce this tendency for weld attack, it is important that the welds be heat treated in the temperature range of 630 – 788ºC (1165 - 1450ºF) for 0.5 – 4 hrs at temperature.

At the lower temperatures nearing that of 630ºC, a longer time is required to achieve the beneficial effect and at the higher temperatures a shorter time is needed. The optimum heat treatment parameters have been shown to be 770ºC (1420ºF) (optimum for sulfuric acid corrosion resistance) for 1 hour at temperature. Figure 3 shows the metallurgical effect before and after post weld heat treatment[5]. This post weld heat treatment can be performed in a furnace or using localized heating. If a zirconium heat exchanger is placed in a sulfuric acid environment, all welds, including the seal welds will require post weld heat treatment. In this case, a blanket heater could be used to “locally” heat treat the seal welds.

Titanium Heat Treatment for Improved Corrosion Resistance

Stress relief of CP titanium may be employed when the metal is placed in applications where it has a susceptibility to stress corrosion cracking (SCC). In many cases, there is essentially no corrosion rate, but intergranular or transgranular cracking occurs when exposed to certain environments. The SCC susceptibility of titanium can be reduced by modifying the metallurgical characteristics, such as residual stress of the metal or by modifying the environment.

Titanium alloys are susceptible to SCC in red fuming nitric acid, nitrogen tetroxide, methanol environments, halogenated hydrocarbons, some hot salts and molten salts. Generally the susceptibility of titanium alloys in aqueous media will depend on the type and concentration of halide species, pH, temperature and /or electrochemical potential in the solution. Titanium equipment is generally not stress relieved for improvement of SCC because other factors must be modified for successful use in specific applications.

Oxide Thickening Heat Treatment

Zirconium can be heated to elevated temperatures to form a thick adherent surface oxide film. This property is not so pronounced for CP titanium. This process can be performed in an air furnace, molten salt bath or fluidized bed. For small parts, the use of a salt bath or fluidized bed is applicable, but with larger vessels an air furnace (e.g. box furnace) is necessary. This heat treatment in air is performed at the same temperature of approximately 550ºC (1020ºF) as that of a stress relief but for a longer time (i.e. 4 - 6 hrs at temperature). The resultant oxide layer that is formed on the surface is generally a maximum of 0.0005mm (0.0002")[6]. The oxide thickening heat treatment is recommended on all parts exposed to abrasive or erosive conditions or on those parts where galling resistance is required.

Figure 4 shows zirconium valves that have been heat treated using the Nobleizing™ surface enhancement[7]. Generally zirconium sieve trays, fasteners, rotating parts, pumps and valves are heat treated to enhance erosion resistance.

Methods of Heat Treatment

Two primary methods of heat treatment are available, including furnace and localized heat treatment. A furnace heat treatment is when a vessel or component is placed totally in a furnace container. Types of batch furnaces include box furnaces, car bottom furnaces, muffle furnaces, roller hearth furnaces and vacuum furnaces. Localized heat treatment occurs when only a portion of a component is heat treated. Localized heat treatment methods include electric resistance pads, induction coils, combustion burners and high temperature quartz lamps. The most common method of localized heat treatment for reactive metals is the use of electric resistance pads that are placed over the area to be heat treated.

Furnace Heat Treatment

Furnace heat treatment is often used when the entire vessel or equipment can be placed in the furnace. This can include smaller parts, components or very large pieces of equipment as shown in Figure 5. Batch furnace heat treatments are the most common type for heat treating of industrial equipment. Batch furnaces include box furnaces, car bottom furnaces, vacuum furnaces, induction furnaces, muffle furnaces and roller hearth furnaces. These furnaces can utilize many types of furnace atmospheres. When the entire vessel is placed in a furnace, it is very important that the differences in thermal expansion of the materials used are carefully considered.

Localized Heat Treatment

Localized heat treatment is generally employed when specific areas of a vessel are required to be heat treated. Localized heat treatment can be performed using heating equipment such as electric resistance pads. Induction or combustion burners and high temperature quartz lamps can also be used. This type heat treatment is typically used when it may be undesirable to heat treat a full vessel due to thermal expansion differences in the materials used for construction. One of the most common local heating methods is using electric resistance heating blankets. This method is used when heat treatment of heat exchanger seal welds is required without placing the vessel totally in the furnace. Figures 6 and 7 show resistance heating used to heat treat a tubesheet face.

Heat Treatment Procedures

Furnace Atmospheres

Both zirconium and titanium are very reactive metals especially at elevated temperatures. Because of this, it is very important that the furnace atmosphere is controlled. Air furnaces can either be electric or fuel-fired equipment. While electric furnaces are preferred for reactive metal equipment to prevent hydrogen pickup, fuel fired equipment is most commonly available. If a gas or oil fired furnace is used for reactive metals, the atmosphere must be maintained with an oxidizing or neutral flame. A reducing atmosphere should never be used because severe hydrogen absorption may occur. Also, the flame should never impinge on the metal surface.

Heat up and Cooling Rates

The heat up rate of the components to be heat treated will depend on the geometry of the equipment to be heat treated. It is recommended that the temperature of the furnace not exceed 427C (800ºF) prior to placing the component or vessel into the furnace. A typical heat-up rate for reactive metal equipment is 100ºC-260ºC (212ºF -500ºF) per hour. The heat-up rate should not exceed 260ºC (500ºF) per hour.

Cooling rates for reactive metals above 400ºC (750ºF) should be done at a rate not greater than 260ºC (500ºF) per hour divided by the maximum metal thickness in inches, but should never exceed 260ºC (500ºF) per hour. When the temperature cools to about 427ºC (800?F), the vessel can be cooled in still air.

Surface Preparation

It is extremely important that reactive metal equipment is thoroughly cleaned of oil, greases, dirt or any other foreign materials prior to exposing the equipment to a heat source. Any contamination left on the material prior to heating could result in contamination of the material’s surface since reactive metals can absorb hydrogen, nitrogen, oxygen and carbon at elevated temperatures. Cleaning can be performed using solvent (non-chlorinated) or detergent and water. The final surface must be clean and dry before placing the equipment into the furnace.

Proper Support

Both zirconium and titanium are fairly low in strength at heat treatment temperatures. It is therefore critical that both zirconium and titanium are supported properly in the furnace to prevent distortion. Improper support will also create loading stresses in the furnace. Figure 8 shows examples of furnace loading with proper support.

Placement of Thermocouples

Proper placement of thermocouples on specific areas of the portion of the vessel to be heat treated is critical. Thermocouples will assist in controlling the heat-up and cooling rates of the vessel. Thermocouples will monitor the temperature at various locations of the vessel to help prevent over heating of the vessel components. Overheating the vessel will be detrimental to the metallurgical properties. When thermocouples are attached to the vessel, sometimes it is necessary to weld a temporary lug of similar material on the vessel. Figure 9 shows examples of thermocouple placement on various components in a furnace load.

Final Vessel Surface Appearance

After heat treatment in an air furnace, zirconium and titanium vessels will show differing surface appearances depending on a number of factors. These factors include temperature, time in furnace, alloy or grade of material, furnace atmosphere, surface roughness and/or mechanical preparation, surface cleanliness and circulation and availability of the air. The final surface coloration can range from gray to black or even white, with some alloys showing a tan or pinkish color. It should be noted that just because the material has a different coloration in a localized area does not mean that the oxide is substandard or detrimental. Visit www.corrosionsolutions.com to view a number of zirconium and titanium plate samples with various surface conditions heat treated using standard stress relief and annealing parameters.

The temperature and time will affect the oxide thickness. Higher temperatures and longer times will create thicker (and generally lighter in appearance) oxide films. Different grades of reactive metals will form different oxide film appearance, depending on the alloying elements of the material and the reactivity of the material.

The furnace atmosphere will affect the oxide formation. The furnace atmosphere can be from a vacuum (no air), to a full air atmosphere. A vacuum or inert gas atmosphere will eliminate or reduce the source of oxygen and decrease the thickening of the oxide film. Even in a vacuum atmosphere, reactive metals can form a thicker oxide film and become discolored. If discoloration is unacceptable in a vacuum heat treatment, the parts (for smaller pieces) should be wrapped with clean zirconium foil. Even with an inert gas or in a vacuum, the metal may show discoloration during heating.

The surface roughness and surface cleanliness will also play a role in the final surface appearance. A cold worked product will appear different than that of a hot worked product. In addition, a blasted, machined or ground surface will result in a different oxide film appearance.

The cleanliness of metals when you start the process will also affect their final surface finish appearances. Residue such as oils or greases could potentially contaminate and cause discoloration of the metal surface.

A final factor which will affect the final surface appearance is the circulation of air in the furnace. If the equipment is resting on supports, the oxide formation in those areas will have a different appearance than those areas with greater air circulation.

Explosive Clad Equipment

Heat treatment can also be performed on explosive clad materials, such as Zr or Ti clad to carbon steel or stainless steel without affecting the bonding strength. Previously it had been thought that the higher temperature heat treatments may not be possible due to a potential reduction in shear strength of the clad material. Recent work by DMC Clad Metals has shown that significant non-recoverable bond strength deterioration should not occur below 800ºC (1472ºF)[8].

Summary

References

*Trademark of Flowserve Group.

RORY BAUSCH-HEADLEY

Rory Bausch-Headley was recently promoted within the Sales organization at Wah Chang. In her new position as an Account Manager for CPI Zirconium Sales, she will be working with Wah Chang’s major CPI fabricators, agents and end users to provide zirconium mill products for CPI projects.

Ms. Bausch has been with Wah Chang since 2000 and has held positions in Safety, Accounting, and Customer Service. In addition to a strong background in the metals industry, she is working towards her Bachelors Degree in Business Management at Linfield College in Oregon.

“Rory’s results-oriented approach, positive attitude, and customer service experience make her a logical choice for the CPI sales staff,” according to Doug Brenizer, CPI Sales Manager. “We’re looking forward to having Rory join our team.”

Ms. Bausch can be reached at 541-917-6754 or at rory.bausch@wahchang.com.

ADAM GARDELLS

Adam Gardells has accepted a position with Wah Chang as a Business Development Analyst. In his new role, he will be supporting the company’s Business Development and Marketing Managers with in-depth reports regarding business opportunities, market conditions, as well as other analysis support.

Mr. Gardells comes to Wah Chang from Oregon State University, where he was employed as a Market Research Associate since 2002. He has a strong background in marketing research and analysis and is a valuable addition to our commercial team. Mr. Gardells holds a Master of Business Anthropology from Oregon State University and a B.S. in Cultural Anthropology from the University of Idaho.

“We’re pleased to add a talented guy like Adam to our team,” said Marketing Manager Kirk Richardson. “He can leverage his experience studying and analyzing growth opportunities for OSU to help Allegheny Technologies identify customers who would benefit by selecting our specialty metals.”

Contact Mr. Gardells at adam.gardells@wahchang.com.

DAVE GOIN

Dave Goin recently joined Wah Chang’s Marketing Department as an Applications Engineer in the Technical Services Group.  His new role will be offering technical support to potential customers as Wah Chang helps develop solutions to their corrosion problems. 

“I am excited to use my previous experience from Chemical Operations for perspective on what concerns drive a potential customer to make decisions about how to fix a problem,” he says. “Obviously the more involved you are with helping that particular person with a specific problem, the more likely it is that will lead to a fruitful business relationship.”

Mr. Goin has been with Wah Chang since 1998.  He spent his previous eight years with the company in the Chemical Operations in Zirconium Reduction/Pure Chlorination and Hafnium as a Process Engineer and Production Supervisor. Mr. Goin is a graduate of the University of Idaho with Bachelor’s degrees in Metallurgical Engineering and in Chemistry.

He can be reached at david.goin@wahchang.com or by phone 541-926-4211 x188.

TRACEY KLEIN

Tracey Klein has been promoted to Sales Manager for Niobium and Niobium Alloys for Wah Chang’s Niobium Products Group. Ms. Klein joined the CPI Zirconium Group for Wah Chang in 2000 and brings 11 years of sales experience and a BS degree in Business (Marketing) to the Niobium Products Group. Her sales responsibilities will initially include Nb and Nb Alloys for aerospace, corrosion and sputtering applications and in time she will also be involved in Wah Chang’s superconductivity business, as well.

“This is a great opportunity for me to expand my knowledge into other Wah Chang products and applications,” she says. “Our primary focus in the CPI Zirconium Group is on Corrosion and Sputtering Applications. I look forward to developing these markets for the Niobium Products Group along with learning and developing the many other applications associated with this product line.”

Ms. Klein will be reporting to Barry Valder, Manager of Niobium Product Sales. She can be reached at her new number 541.917-6797 or at tracey.klein@wahchang.com.

BOB MARSH

Bob Marsh recently joined Wah Chang’s Business Development Group as a Project Manager. Mr. Marsh has over 29 years of experience with metals production, market development, and sales. He began his career at Wah Chang working in zirconium production and, over many years, has built extensive knowledge of the company’s product lines.

Mr. Marsh will be part of the Wah Chang team focused on market and product development efforts. Initially, his focus will be on Wah Chang and ATI metals developed for chemical processing and other industrial applications.

“Bob’s experience at Wah Chang and his knowledge of the many markets the company serves make him a great fit for our Business Development Group,” says Andy Nichols, Director of Marketing. “He brings metallurgical and processing knowledge to the job that will directly benefit our customers.”

Mr. Marsh can be reached at 541-967-6919 or by e-mail at bob.marsh@wahchang.com.

JENNIFER SHULTS

Joining the Wah Chang sales staff as Sales Technician/Customer Service Representative is Jennifer Shults. Ms. Shults was previously employed with Salem Legal Group where she held the position of Firm Administrator.    

Ms. Shults’ responsibilities will include order management support for the Nuclear, CPI and Chemical Sales Groups, as well as, playing an active role in the implementation of Wah Chang’s customer relationship management (CRM) project. In addition to her other duties, she will provide administrative support to the sales department. 

Ms. Shults can be reached at 541-967-6977 or at jennifer.shults@wahchang.com.