Exotic alloys. The answer for demanding spring applications. White paper

Transcription

1 Exotic alloys The answer for demanding spring applications By John King, Manager of Engineering, Atlantic Spring Keith Thomas, P.E., Vice President & General Manager, Engineered Spring Products

2 If you have a demanding application that is used in high-temperature, corrosive or other harsh environments, manufacturing your spring or fastener out of an exotic alloy may provide the performance-driven solution you require. Exotic alloy solutions have been around for decades and continue to find their way into a variety of applications where durability, reliability and longevity are the main goals. Understanding performance attributes, cost and trade-offs are key to making the best decision. For example, some exotic alloys are capable of sustaining temperatures in the 650 to 1,400 degree Fahrenheit range. Others are resistant to chlorine, sulfuric, phosphoric or nitric acids. Each has its own attributes which must align with the application objectives in order for the execution to be successful. As you design your next product, consider the benefits of unique alloys. What follows is a list of the most commonly-used exotic alloys for springs, accompanied by attributes and considerations, to help narrow down choices for your next challenge. A286 Description. A-286 is an iron/nickel/chromium super alloy appropriate for applications that require high tensile strength, oxidation and corrosion resistance. Economics. Developed in the late 1960s as an alternative for Inconel X-750 which had become expensive. Because it has one-third the nickel content of Inconel X-750, it is an attractive alternative. However, it has limited availability for spring wire sizes. Applications: Most frequently used for springs used in valves subjected to high temperatures. Alternative material for: Inconel X-750. However, if higher corrosion resistance is desired, Inconel X-750 is a better choice. Where can you turn for exotic alloy assistance? Design engineers are being challenged like never before to create next generation products in a compressed timeline. Designs are becoming more complex, while at the same time, development cycles are shrinking. Additionally, companies are losing specialized knowledge faster than they are building it. Simply said, professionals are being asked to do more with less. In the pursuit of specifying the right type of spring for your application, you may run into a knowledge stumbling block. For example, you may have a basic knowledge of exotic alloys, but your experience may not be deep enough to give you confidence that you are making the right decision. That s where MW Industries comes into the picture. With our far-ranging expertise in metallurgy and hundreds of experience years in spring manufacturing, we help design engineers to pick the right metal or alloy for specific applications some of which are extremely challenging. In addition to manufacturing springs using exotic alloys, we continuously expand our knowledge base by interacting frequently with alloy suppliers. We learn from their experts so that we are continuously up to date on technology, availability, pricing and other key attributes that impact our ability to provide you with the right solution. That s why MW Industries is your ideal partner for spring solutions made from exotic alloys. 2 of 8

3 Beryllium copper Description: Beryllium copper is a copper alloy with up to 3% beryllium and includes other elements to obtain high strength with non-magnetic and non-sparking qualities. It has excellent metalworking, forming and machining properties. Beryllium copper is known for its ability to withstand corrosion. Additionally, it has a low torsion modulus which enables it to deliver more force compared to steel in a restrained area. Because it is formed soft and then becomes hard after heat treating, the material is very effective in spring applications. Beryllium copper also has great electrical connectivity which might be desired in certain applications. Alloy type used in springs: Beryllium copper alloy 172. Economics: It costs approximately 2.5 times that of stainless steel, but is two-thirds the cost of Inconel. Applications: Anything that needs long-life corrosion-resistance to salt water. Examples include springs used in nuclear submarine hatch covers and in valves for off shore oil rigs. Alternative material for: Phosphorus bronze and Monel K-500. Cons: Beryllium is very hazardous. Elgiloy Definition: Elgiloy is considered a super-alloy consisting of cobalt, chromium, nickel, iron, molybdenum and manganese. It s used to make springs that are corrosion resistant as well as provide high strength, ductility and good fatigue life. Elgiloy is highly resistant to sulfide stress corrosion cracking and pitting, and can operate at temperatures up to 850 F. MW Industries uses: Springs used in oil and gas applications are produced from wire or strip. Also slant coil springs used in energized seal applications. Applications: Oil and gas in a wellbore environment is probably one of the largest applications for Elgiloy springs because the alloy is highly resistant to corrosion cracking in chlorides. It is also used in aerospace applications where high strength and temperature resistance is required. Other applications include springs for medical and dental products. Alternative material for: Inconel X-750, if upgraded performance is required. Elgiloy will provide more strength in a small space than Inconel X-750 and MP35N. Cons: Cost can be prohibitive if the performance requirements do not merit its use. Limitations: Three-quarters of an inch is the maximum wire size. In strip form, you are limited to 1/16th of an inch thickness and 12 to 14 inches wide. Hastelloy Definition: Hastelloy alloys provide excellent resistance to chlorides and acids. Heat Resistant Exotic Alloys MW Industries uses: Hastelloy C276 is most commonly used to manufacture springs. Applications: Food processing, petrochemical, marine applications and water treatment valves. Cantilevered springs for energized seal applications. Alternative material for: Improved performance compared to 300 series stainless steel. Less expensive than Elgiloy. Cons: Narrow range of product forms used for spring applications. Limited tensile strength. Rene 41 Inconel Elgiloy MP35N Titanium 3 of 8

4 How MW Industries solved a spring problem with Hastelloy A food processing plant was using equipment to peel and chop fruits and vegetables. During peak season, the stainless steel springs on that equipment were being replaced weekly. This was causing a significant amount of downtime and related labor to replace. MW Industries examined the production process and discovered the problem. Bleach was being used at the end of the shift to clean the equipment as part of its sanitation compliance procedure. The food processing facility was unaware of the adverse effect of the bleach on the springs. The recommendation was made to change all of the springs from stainless steel to Hastelloy. Now the food processor can run all season without replacing parts. The changeover was simple to execute because a stainless steel spring can easily be copied into Hastelloy. The result is a spring that s have similar mechanical properties and functions in a nearly identical way. Hastelloy is a great alternative for those applications using stainless steel springs which are subjected to a higher level of chlorine and acids. Hastelloy will help eliminate corrosion, cracking and other part failures. Inconel Definition: Inconel is a group of alloys containing mostly nickel with chromium and is resistant to corrosion and high temperatures. It was developed in the mid-1900s for nuclear reactor applications. MW Industries uses: Inconel X-750 is most common for spring and wire because this grade offers the best combination of high temperature, corrosion resistance, and availability. Inconel 718 and 600 are also used for coiled springs as well as Belleville washers. Applications: Valves that are used with high temperature fluid or steam (nuclear reactors for submarines and aircraft carriers). An example is the springs used in vacuum furnaces for semiconductor manufacturing. It is also National Association of Corrosion Engineers (NACE) approved for down hole gas exposure. Other uses include lower-tier tools, which will not be subjected to severe service or have a short lifespan, where term corrosion exposure is not an issue. Alternative material for: MP35N and Elgiloy, at less than half the cost. However, it is not as resistant to certain chemicals as compared to MP35N and Elgiloy. Cons: Moderate resistance to chlorides, saltwater and acids. If your application requires more strength and corrosion resistance, upgrade to MP35N or Elgiloy. How MW Industries solved a spring problem using Inconel A company that manufactures valves for high pressure steam applications was having a problem with the supplier of their Inconel springs. The springs were not properly performing in the intended application. MW Industries knew from its significant experience with the material that it needed to take into account performance at room temperature, as well as in elevated steam conditions. MW Industries suggested a spring modification and adjusted the heat-treatment process. The spring was then able to function perfectly in the high-temperature application. 4 of 8

5 Maraging steel Material: Maraging steel was originally developed for liquefied natural gas vessels on large tankers. Its inherent material lattice structure prevents propagation of cracking when subjected to stress or load. It is the strongest spring steel available and is good for both low and high temperature applications. MW Industries uses: For high stress applications, four different alloys (200, 250, 300 and 350) are used. The numbers reference the material s yield strength, which is superior to other alloys. Applications: Torsion and recoil springs for army tanks. Alternative material for: Provides higher strength than stainless 17-7 PH. Cons: Not as corrosion resistant as a high nickel alloy. MP35N Material: MP35N is a cobalt/nickel/chromium base alloy which is corrosion resistant and exhibits high strength, good fatigue life. MW Industries uses: Machined parts, spring washers, and products formed from bar stock are produced from MP35N, in addition to all forms of springs made from wire. Applications: Corrosion resistant applications involving oil and gas exploration or chemical and marine equipment. It is also used in aerospace applications where high strength and hardness levels are required and also for springs used in medical and dental products. Alternative material for: MP35N comes in a wider array of forms than Elgiloy, which is only available in wire or strip. MP35N is available in bars, sheets and wire, offering manufacturing flexibility. It is interchangeable with Elgiloy in environments below 400 F. Cons: For temperature requirements above 400 F, Elgiloy is a preferred choice particularly in oil and gas applications. How MW Industries solved a spring problem using MP35N A customer was using a custom wave spring that another manufacturer was producing for a down hole oil and gas application. It was an expensive solution because they were stacking two wave springs endto-end. In addition to the economics, the performance was less than desirable and the spring needed to be replaced frequently. MW Industries designed a stack of Belleville washers that are machined out of MP35N sheet. Although the Belleville washers were more expensive, they did not have to be replaced as frequently, bringing down the overall cost. The solution met temperature cycle demands as well as were performing successfully in a corrosive environment. The customer was so pleased it asked MW Industries to review some of its other spring applications and make recommendations for improved performance. 5 of 8

6 Ni-Span-C Material: Ni-Span-C is a nickel/chrome alloy. It can handle broad swings in temperature (between -75 F to 140 F), while maintaining the same torsion modulus. Applications: Springs for thermostats and watches. Alternative material for: No other alloy delivers a constant torsion modulus through a broad temperature range for applications that require both. Cons: Cost and availability. Rene 41 Material: Rene 41 is an alloy of nickel, cobalt and chromium, developed for super high temperatures up to 1,500 F. Applications: It frequently is the only spring wire that is suitable for a ceramic application requiring force at 1,500 F. Also valves located in, or next to, a furnace. Any application that is exposed to super high temperatures such as refractories. Alternative material for: Superior performing compared to Inconel alloys. Cons: High cost and not good for applications requiring high strength. Tantalum Definition: Tantalum is the only material that withstands chlorine acid directly. MW Industries uses: Tantalum 61 is used for springs for valve applications. Applications: Tantalum springs are used in municipal processing plant valves for water and sewer lines because they can withstand direct contact with chlorine which is used in the waste water purification. Also used in the electronic industry for contacts. Alternative material for: Superior properties when compared to Hastelloy C. Chlorine concentration levels will determine if Hastelloy is suitable for sewage treatment applications or if an upgrade to Tantalum is required. Cons: It is extremely expensive, ranging from $800 to $1,500 per pound. It is also not very strong, so unless you have continual exposure to high concentrations of chlorine, you are likely to consider alternatives. How MW Industries solved a spring problem using tantalum A well-known, global engineering company was experiencing performance issues with its Hastelloy C valves located at the bottom of a sewage tank. MW Industries showed them how springs made from tantalum could provide the desired lifespan and improve performance. Converting to the tantalum solution meant they were no longer faced with the unpleasant task of replacing springs at the bottom of a sewage tank. 6 of 8

7 Titanium Definition: Titanium offers very high strength at low weight. It provides maximum force in a small space. It is both hot and cold workable. Titanium has a low torsion modulus and is heat treatable after forming. Its ability to be hot formed, enables the fabrication of larger springs. MW Industries uses: Grade 5 and Beta C, which is used extensively in the aerospace industry. Applications: Primarily aerospace including springs for airplane controls and landing gear. Also used for military and automotive applications. Other uses include implantable medical devices and compensator springs for oil and gas applications. Alternative material for: Stainless steel or Inconel. Stainless steel is heavier, but much less expensive. Weight/cost attributes needs to be considered. Cons: Temperature attributes not as good as Inconel, but superior to stainless steel. Exotic alloys: capabilities at-a-glance High tensile strength Corrosion resistance Low torsion modulus Electrical connectivity Nonmagnetic Suggested operational temperature limits Spring applications Alternative for A286 X X X Up to 800 F Beryllium copper X X X X X Elgiloy X X X Up to 800 F? Hastelloy X X Up to 400 F Valves subjected to high temperatures Long-life corrosion resistance to sea water Oil/gas wellbore environment Food processing, petrochemical, marine, etc. Inconel X-750 Stainless steel, Inconel Inconel X series stainless steel Inconel X X Can range up to 1200 to 1400 F? High temp fluid or steam MP35N, Elgiloy Maraging steel X X 600 F to -300 F Valve springs, recoil springs Stainless 17-7 PH MP35N X X Up to 800 F Ni-Span-C 140 F to -75 F Oil/gas wellbore environment Thermostats, watches Elgiloy Unique material Rene 41 Up to 1,500 F Refractories Inconel Tantalum X Valves for water, sewer lines. High chlorine applications Hastelloy C Titanium X X X 700 to 750 F? Aerospace, medical, oil & gas Stainless steel, Inconel 7 of 8

8 MW Industries: your resource for exotic alloy expertise MW Industries professionals, located across all manufacturing locations, have decades of experience in knowing what material will work best for a given application. Understanding metallurgy is the foundation of spring making, followed by a thorough knowledge about mechanical properties. More than 100 engineers located at the company s various manufacturing locations devote thousands of hours per year to stay current on the processing required for exotic materials and newly developed spring materials. They also partner with customers to make sure recommendations will best suit the application. MW Industries has licensed engineers available to review any product challenge and assist with component design. It s likely we have already solved a similar problem and can draw from our vast experience. The company is proud to partner with many of the world s best known brands to provide spring and fastener solutions that help insure product success. MW Industries also partners with alloy manufacturers to gain knowledge from those responsible for developing exotic alloys. With close ties to these manufacturers, MW Industries has a direct pipeline to supply and data that is used to produce successful results. The company is known for fast quotes, rapid turnaround, precision, consistent quality and superb customer service, no matter how common or rugged the application demands are. Please contact us if you need assistance finding the right spring solution for your product. MW Industries 9501 Technology Blvd Rosemont, IL Phone: sales@mw-ind.com 8 of 8