Better understanding of steel fracturing

February 10, 2015
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Better understanding of steel fracturing

 

Researchers from the Universidad Carlos III de Madrid (UC3M), Spain, visualized step-by-step and on a microscopic level how certain steels fracture when extreme loads are applied to them. This could help to improve these materials, used in the automobile industry.

 

Scientists from the UC3M Powder Technology Group (initialled GTP in Spanish) have carried out this research using a scanning electron microscope to obtain high-resolution images (around 10 nanometers; a nanometer is one millionth of a millimeter). The application of new techniques to characterize materials has made it possible to better understand the behavior of sintered steels (those produced from powders) on fracturing. In this way, they have been able to discover where the first cracks "‘nucleate' and where they particularly extend to," explain researchers.

 

The materials that are the subject of the research are commercial sintered steels obtained through powder metallurgy or powder technology and are widely used in the automobile industry. Mechanical and on-site characterization tests performed in the scanning electron microscope have been essential in "understanding the mechanisms of fracture," which, until this research, "we have never been able to determine, but instead only intuit," explains one of the authors, Elena Bernardo.

 

In this study several steels currently on the market were evaluated. Specifically, an Fe-C steel, a steel pre-alloyed with molybdenum (Astaloy Mo grade, Höganäs AB) and the well-known Distaloy AE (Höganäs AB), which is iron alloyed by diffusion with copper, nickel and molybdenum, were analyzed.

 

Results aid in understanding the connection between microstructure and properties which, in these materials, entails a technological challenge, as not only the phases but also the residual porosity that composes their microstructure come into play. José Manuel Torralba, full professor in the UC3M department of Materials Science and Engineering, stresses the fundamental role of porosity in these steels: "The research has revealed, among other things, that the most angular and irregular pores are the first points of ‘nucleation,' that is, those that initiate the breaking."

This study makes changes in the microstructure of the material visible while it is being tested, says Torralba. Moreover, the methodology used "is applicable to any type of alloy" and not only to test its behavior under pressure, but "also its behavior at high temperatures." Some of the research was carried out at the UC3M facilities and was completed at IMDEA Materials, a research institute financed by the regional government of Madrid and the European Union.

Better understanding of steel fracturing

Researchers from the Universidad Carlos III de Madrid (UC3M), Spain, visualized step-by-step and on a microscopic level how certain steels fracture when extreme loads are applied to them.

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Greener ship propellers

October 31, 2014
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Some of the propeller blades manufactured by Oshaug Metall AS in Molde, Norway, are so big that if the complete propeller stood on end, it would reach up to the roof of a three-story building. In collaboration with Oshaug, SINTEF developed an energy-saving casting technology which successfully completed pilot trials at the foundry's manufacturing center in Norway.

"The pilots reveal that the method can save as much as 35% of the electricity currently used to melt the metal we need to cast a propeller", says Arne Nordmark, a researcher at SINTEF and father of the invention.

Propeller parts from the foundry in Molde end up in the propulsion systems and lateral propellers in everything from naval vessels to cruise ships. The smelting furnaces at Oshaug consume as much electricity as a hundred average Norwegian households—1.5 million kilowatt hours per year.

"The results of the project so far indicate that we can reduce electricity consumption by half a million kilowatt hours per year, and in this way reduce both costs and negative impacts on the environment," says Stein Berg Oshaug.

Unlike water, which expands when it freezes, molten metals shrink in volume when they solidify. Foundries compensate for this during the casting process by adding a little extra molten metal from reservoirs called feeders. The feeder forms part of the mold and is situated above the level of the casting. As the propeller blade solidifies and starts shrinking, additional molten metal is supplied from the feeder.

However, the metal in the feeder also solidifies. But if it is to compensate for the shrinkage in the casting, this metal must not be allowed to solidify before the propeller metal does. The feeder must retain molten metal right up until the time when the blade becomes solid. Currently, this is achieved by making big feeders—on the principle that large volumes solidify more slowly than small ones.

The new invention involves surrounding the feeder with an induction coil that supplies heat which keeps the metal in the feeder molten. This means that feeders no longer have to be so big in order to do their job. They only have to be large enough to contain the small amount of molten metal needed to compensate for the shrinkage in the casting.

According Nordmark, this is important because, "Currently, in order to prevent the too rapid solidification of the metal in the feeder, a propeller blade manufactured using traditional casting methods requires a feeder almost as large as the blade itself. A blade weighing 1000 kg may require a feeder weighing as much as 800 kg. However, shrinkage during solidification constitutes only about 10% of the weight and volume of the propeller blade. If the metal in the feeder is kept molten using heat supplied by an induction coil, only 100 kg are required to compensate for the shrinkage of a propeller blade weighing 1000 kg. So instead of having to melt 1800 kg of metal, foundries would only need 1100 kg."

Because the invention comes close to halving the amount of metal that has to be melted, Oshaug will now be able to cast more propeller blades in a given time (or bigger blades) than its current capacity permits.

"The new technology enables us to increase production capacity by as much as 50%, and in cash terms this is even more than we save in electricity," says Oshaug.

An extra bonus is that there is less need for heavy-duty post-casting work. After the casting process is complete and the metal solidified, the feeder metal is cut from the casting for re-melting during the next casting operation. This cutting process is very time-consuming for feeders of large diameter. During the pilot trials of the new technology in Molde, the diameter of the feeder was reduced by 60%, thus reducing cutting work.

Image caption — New technology almost halves the amount of metal that has to be melted in order to cast a propeller blade. This was tested for the first time on an industrial scale at Oshaug Metall in Molde. Photo: Oshaug Metall/Arnt Jørgen Sønslien.

Greener ship propellers

Invention reduces the energy that foundries need to manufacture ship propeller blades by a third.

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SSAB launches Laser Plus steel with guaranteed flatness after laser cutting

October 29, 2014
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SSAB Stockholm, Sweden, has introduced Laser Plus, a new generation of steels for laser cutting that comes with unique guarantees: maximum flatness deviation of 3 mm/m after laser cutting, and bending radius of 0 -1.5 x the material thickness. These features make it possible to meet the most challenging requirements in automated production environments.

The production process of Laser Plus steels results in a surface that is covered with a thin micro scale. This enables extremely efficient laser- water- and plasma cutting. The quality of the cut edge remains excellent, even up to a thickness of 30 mm. The cold forming properties of Laser Plus steels are excellent and SSAB guarantees inner bending radius of 0-1.5 x the material thickness, depending on strength level in combination with thickness.

Laser Plus steels are now available both as heavy plates and hot-rolled strip products. It is the new standard for demanding applications in mechanical engineering and construction, as well as in the automotive and electronics industries.

www.ssab.com

 

SSAB launches Laser Plus steel with guaranteed flatness after laser cutting

SSAB Stockholm, Sweden, has introduced Laser Plus, a totally new generation of steels, for laser cutting that comes with unique guarantees: maximum flatness deviation of 3 mm/m after laser cutting and bending radius of 0 -1.5 x the material thickness.

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ASM International partners with AQM to offer classes overseas

October 2, 2014
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ASM International, Materials Park, Ohio, announced a new education collaboration agreement with AQM, a primary technical services center in northern Italy. Through this new partnership, AQM is now an educational support location in Europe for ASM International. Starting this fall, multiple metallurgical blended and online courses are planned using the metallurgical laboratories and the metallography and the heat treatment schools of AQM and will be taught by ASM International instructors.  

"We hope this partnership will help extend our global reach, fuel a passionate sense of community, energize members to aspire to new levels of success, and advance the development of materials," said Thom Passek, managing director of ASM. "AQM has a similar mission and the goal of our collaboration is to ultimately elevate the importance of materials professions. European metallurgical  students will be able to lower their costs of training by traveling to a local destination and we hope that provides an extra incentive to take a course with us."

"AQM has always supported the training and growth of technical competence in the field of metallurgy, believing that this is one of the key factors for competitive growth of enterprises," says Gabriele Ceselin, CEO of AQM. "This collaboration will provide an additional impulse in this direction, promoting an approach at the highest level, and the access to innovative international relations."

Topics of the educational courses include:

  • Metallurgy for Non-Metallurgist
  • Practical interpretation of Microstructures
  • Corrosion
  • Principle of Failure Analysis
  • Failure Analysis in the Oil and Gas Industry
  • Metallographic Interpretation
     

Students will receive a complimentary one year ASM International membership, allowing them to share ideas and solutions with other members about technologies and application processes while building personal and professional networks around the world. They will also have free access to online journals and technical publications, as well as access to special offers available only to members.

The new ASM International-AQM training offer is intended to complement and reinforce the AQM Expertise Center's "Materials and Quality Control of Products," which already has a full calendar of courses through the School of Metallography.
Do you belong to an ASM European chapter? Contact them directly for a special promotional code and save on registration! 

ASM International partners with AQM to offer classes overseas

Fall metallurgical class schedule available for new Italy location

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Europe’s new age of metals

September 18, 2014
Source: ASM International

Europe’s new age of metals

The European Space Agency has joined forces with other leading research institutions and more than 180 European companies in a billion-euro effort developing new types of metals and manufacturing techniques for this century.

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Multi-element high-entropy metal alloys crystallize as a single phase

September 10, 2014
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The Department of Energy' s Lawrence Berkeley and Oak Ridge National Laboratories announce that a new concept in metallic alloy design – called "high‐entropy alloys" – has yielded a multiple-element material that has been demonstrated to be not only very tough at room temperature, but also strong and ductile at cryogenic temperatures. By definition, HEAs are multi-component alloys having at least five principal elements, and all the principal elements are mixed in equiatomic or close-to-equiatomic  ratios.

"We examined CrMnFeCoNi, a high‐entropy alloy that contains five major elements rather than several minor elements and one that dominates," says Robert Ritchie of Berkeley Lab's Materials Sciences Division. "Our tests showed that despite containing multiple elements with different crystal structures, this alloy crystallizes as a single phase, face‐centered cubic solid with exceptional damage tolerance. Furthermore, its tensile strength  is above one gigapascal, and fracture toughness values are off the charts, exceeding that of virtually all other metallic alloys."

Dr. Ritchie is the corresponding author, along with ORNL's Easo George, of a paper in Science describing this research. The paper is titled "A fracture resistant high‐entropy alloy for cryogenic applications." Co-authors are Bernd Gludovatz, Anton Hohenwarter, DhirajCatoor, and Edwin Chang.

"High‐entropy alloys represent a radical departure from tradition," Dr. Ritchie says, "in that they do not derive their properties from a single dominant constituent or from a second phase. The idea behind this concept is that configurational entropy increases with the number of alloying elements, counteracting the propensity for compound formation and stabilizing these alloys into a single phase, like a pure metal."

Although high‐entropy alloys have been around for more than a decade, it has only been recently that the quality of these alloys has been sufficient for scientific study. Dr.  George and his research group at ORNL combined high‐purity elemental starting materials with an arc-melting and drop-casting process to produce high quality samples of CrMnFeCoNi  in sheets roughly 10 mm thick. After characterizing these samples for tensile properties and microstructure, the ORNL team sent them to LBL for fracture and toughness characterization.

Tensile strengths and fracture toughness values were measured for CrMnFeCoNi from room temperature down to 77 Kelvins, the temperature of liquid nitrogen. The values recorded were among the highest reported for any material. That these values increased along with ductility at cryogenic temperatures is a huge departure from the vast majority of metallic alloys, which lose ductility and become more brittle at lower temperatures.

Researchers  believe that the key to  its remarkable cryogenic strength, ductility and toughness is a phenomenon known as "nano-twinning," in which during deformation, the atomic arrangements in adjacent crystalline regions form mirror images of one another.

http://newscenter.lbl.gov/2014/09/04/a-metallic-alloy-that-is-tough-and-ductile-at-cryogenic-temperatures/#sthash.6dCRaR2t.dpuf

 

Multi-element high-entropy metal alloys crystallize as a single phase

The Department of Energy’ s Lawrence Berkeley and Oak Ridge National Laboratories announce that a new concept in metallic alloy design – called “high?entropy alloys” – has yielded a multiple-element material that is strong at cryogenic temperatures.

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Wayne State develops technology for high-strength bainitic steels and austempered ductile irons

June 10, 2014
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Wayne State University, Detroit, has finalized a license agreement with a new start-up company, Detroit Materials Inc., for a Wayne State-patented portfolio of high-strength low-alloy steels and cast irons for demanding applications. The portfolio includes bainitic steels and austempered ductile irons exhibiting a combination of excellent mechanical properties currently available only in costly exotic steels.

A team of researchers led by Susil Putatunda, Ph.D., professor of chemical engineering in Wayne State University's College of Engineering, have been working to create advanced materials with high yield strength, fracture toughness, and ductility.  Dr. Putatunda's research was initially funded by a grant from the National Science Foundation (award number 0854962), and more recently received funding from the New Economy Initiative's (NEI) Technology Development Incubator Program. This program is aimed at accelerating feasibility studies necessary for licensing, industry partnerships, and start-up opportunities.

The company was founded by Pedro Guillen in his role as entrepreneur-in-residence for the Detroit Technology Exchange, with direct financial and administrative support from Detroit Innovate, a new venture fund based in southeast Michigan.

Mr. Guillen, Chief Executive Officer of Detroit Materials, specializes in corporate innovation strategy and new technology commercialization. He has over 15 years of product development and innovation experience in automotive, defense, off-highway, and clean energy markets. He has led engineering teams developing proof-of-concept technologies and demonstrator vehicles for the Department of Defense, and founded two successful start-ups.

www.wayne.edu  

 

Wayne State develops technology for high-strength bainitic steels and austempered ductile irons

Wayne State University, Detroit, has finalized a license agreement with a new start-up company, Detroit Materials Inc., for a Wayne State-patented portfolio of high-strength low-alloy steels and cast irons for demanding applications.

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VPC and Liquidmetal sign agreement to grow amorphous metal technology

May 28, 2014
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Liquidmetal Technologies Inc., Rancho Santa Margarita, Calif., announces that it has signed an amended sublicense agreement with Visser Precision Cast LLC (VPC) in which Liquidmetal is freed from its commitment to use VPC as its exclusive contract manufacturer, and VPC is freed from its commitment to use Liquidmetal as its exclusive sales and R&D channel. The new agreement provides both companies with the flexibility to pursue independent sales and manufacturing strategies needed to rapidly grow the market for amorphous metal products.

"We are pleased to have reached this agreement with VPC, as we believe it is in the best interests of both companies," said Tom Steipp, President and CEO of Liquidmetal. "Under the new agreement, Liquidmetal is able to enter into contracts with other manufacturers to serve a broad array of specialized industries and geographies. We expect a network of manufacturers to leverage their customer relationships to readily identify promising applications, and to leverage their quality certifications and qualified supplier status to rapidly qualify parts for production."

According to Ryan Coniam, President of VPC, "The agreement between Liquidmetal and VPC is a big step forward for both companies. VPC has made substantial investments in its amorphous metal casting technology and we have proven the promise of this technology for several high-value applications."

Under the terms of the amended sublicense agreement, VPC will have rights to manufacture, market, and sell amorphous metal products directly to customers, and it will retain a license to the full portfolio of technology developed by Liquidmetal that exists as of the date of the agreement.

Liquidmetal will have rights to contract with manufacturers of its choosing, and it will retain exclusive rights to any technology that Liquidmetal develops after the date of the agreement. The companies will work together to complete certain projects that VPC currently is manufacturing for Liquidmetal customers, and the companies may choose to work together in the future on a project-by-project basis.

VPC and Liquidmetal sign agreement to grow amorphous metal technology

Liquidmetal Technologies Inc., Rancho Santa Margarita, Calif., announces that it has signed an amended sublicense agreement with Visser Precision Cast LLC (VPC) in which Liquidmetal is freed from its commitment to use VPC as its exclusive contract manufacturer, and VPC is freed from its commitment to use Liquidmetal as its exclusive sales and R&D channel.

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