Chromium in Martensitic Stainless Steels
September 26, 2016
Source:
The interplay between chromium and carbon is further explained in the two graphs of the iron-chromium phase diagram. The iron-chromium phase diagram at (a) shows 12% chromium and (b) shows 17% chromium. Higher chromium alloys, the range over which full austenitization can occur is further restricted.
The variety of martensitic stainless steels would be very limited if only chromium and carbon were available as alloying elements, but fortunately nickel can make an important contribution. Nickel greatly expands the chromium levels and temperatures at which austenite is stable,
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Heat Treating of Martensitic Stainless Steels ⇒ Alloying
Higher chromium alloys, the range over which full austenitization can occur is further restricted. The variety of martensitic stainless steels would be very limited if only chromium and carbon were available as alloying elements, but fortunately nickel can make an important contribution.
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One Minute Mentor: Martensitic Stainless Steels
September 16, 2016
Source:
A stainless martensitic alloy should have the following characteristics:
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It must have at least 10.5% chromium to qualify as stainless, and even more for better corrosion resistance.
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It should be fully austenitic at some temperature.
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The temperature at which austenite forms on heating should be sufficiently high to permit tempering above the temper embrittlement range.
These criteria are somewhat challenging to meet. The two graphs show iron-chromium phase diagrams at two low-carbon levels.
The figure on the left shows that at low-carbon (0.05%) levels, austenite is stable up to about 12% chromium, above which some δ-ferrite tends to be stable at all temperatures below the melting point.
Increasing carbon slightly, to 0.1%, shown on the right, expands the chromium level at which the steel becomes fully austenite.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Heat Treating of Martensitic Stainless Steels ⇒ Alloying
A stainless martensitic alloy should have the following characteristics:
• It must have at least 10.5% chromium to qualify as stainless, and even more for better corrosion resistance.
• It should be fully austenitic at some temperature.
• The temperature at which austenite forms on heating should be sufficiently high to permit tempering above the temper embrittlement range.
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ASM Appoints New Managing Director
September 13, 2016
Source: ASM International
The ASM International Board of Trustees announces the appointment of William T. (Bill) Mahoney as Managing Director effective immediately.
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Sciaky and EWI collaborate to 3D-print metal prototype parts
August 17, 2016
Source:
Sciaky Inc., Chicago, announces that it will collaborate with the Edison Welding Institute, Columbus, Ohio, to produce 3D-printed prototype parts for high-tech manufacturers in a variety of industries across the United States. EWI has purchased an industry-leading Electron Beam Additive Manufacturing (Ebam) system from Sciaky, and both companies plan to co-market their extensive metal 3D printing capabilities to the marketplace.
"Sciaky is very excited to work with an innovator like EWI," saidMike Riesen, General Manager of Sciaky, Inc. "Beyond simply selling an Ebam system to EWI, Sciaky will collaborate with EWI to advance and promote the technology into mutual fields of interest. New applications and solutions will surely be discovered under this exciting partnership."
As the most widely scalable metal 3D printing solution in the industry (in terms of work envelope), Sciaky's Ebam systems can produce parts ranging from eight inches to 19 feet in length, but can also manufacture smaller and larger parts, depending on the application. Ebam is also the fastest deposition process in the metal additive manufacturing market, with gross deposition rates ranging from 7 to 20 pounds of metal per hour. Plus, with a dual wirefeed option, two different metal alloys can be combined into a single melt pool to create "custom alloy" parts or ingots. In addition, the mixture ratio of the two materials can be changed to create "graded" parts or structures.
www.sciaky.com
www.ewi.org
Sciaky Inc., Chicago, announces that it will collaborate with the Edison Welding Institute, Columbus, Ohio, to produce 3D-printed prototype parts for high-tech manufacturers in a variety of industries across the United States.
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One Minute Mentor: Hardening Ferritic Stainless Steels
July 15, 2016
Source: ASM International
Ferritic stainless steels are quite similar in their mechanical behavior to carbon steel.
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Aichelin Group acquires AFC-Holcroft for its heat treating furnace equipment
July 13, 2016
Source:
Aichelin Group, Austria, announces that it has acquired U.S.-based Atmosphere Group, the holding company of AFC-Holcroft, said to be the U.S. market leader in the production of industrial furnace equipment for ferrous and nonferrous metals. According to Aichelin, the two groups are a perfect fit: Both are leading market players with a long-standing history and state-of-the-art technologies and services in the industrial area of heat treatment solutions.
Aichelin Group's business model covers all stages of the lifecycle: From design, engineering, manufacturing and installation at customer sites, to comprehensive maintenance and spare part services. By combining the networks of Aichelin Group and AFC-Holcroft, customers will get the best of two worlds: An enlarged, high quality product portfolio as well as an innovative, worldwide service network.
As the next step, a process will start to integrate AFC-Holcroft and its sister companies into Aichelin Group's network in the coming months. AFC-Holcroft's headquarters will remain in Wixom, Michigan. The current top management stays in place and most customers will keep their key account managers.
Aichelin Group includes manufacturing companies Aichelin, EMA Indutec, Safed, Bosio, and Noxmat, which provide plants and systems.
In addition to AFC-Holcroft, the Atmosphere Group includes Atmosphere Heat Treating and Austemper Inc. Until now, Atmosphere Group was privately held. The parties agreed not to disclose details or the price of the transaction.
The acquisition complements the geographic presence of Aichelin Group and strengthens the Group's overall market position as one of the leading global heat treatment groups. It is now the largest provider of atmosphere furnaces worldwide. With a strong presence in Europe, North America, and Asia, the joint annual turnover generated by 1100 employees amounts to over $216 million (2015). The group operates a network in 32 countries.
www.aichelin.com
Aichelin Group, Austria, announces that it has acquired U.S.-based Atmosphere Group, the holding company of AFC-Holcroft, said to be the U.S. market leader in the production of industrial furnace equipment for ferrous and nonferrous metals.
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ZEISS partners with ASM International to supply microscopes and collaborate on training
June 17, 2016
Source: ASM International
Instruments to be used for training on high precision manufacturing and materials testing techniques
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Women in engineering profile: Lesley D. Frame
June 9, 2016
Source: ASM International
This new profile series introduces leading materials scientists from around the world who happen to be females. Here we speak with Lesley D. Frame, Director of Product Development for Thermatool Corp.
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One Minute Mentor: Stabilization
May 20, 2016
Source:
Stabilization is generally considered to be the simple gettering of carbon and nitrogen by a suitable carbide former such as titanium or niobium. Stabilization is essential for ferritic stainless steels to avoid the precipitation of grain boundary carbides.
For example, if carbon and nitrogen are kept as low as possible and a stoichiometric amount of titanium is available (i.e., greater than about four times the carbon plus nitrogen), then essentially all carbon is removed from solution (below 2280°F). However, the stabilization formula in various specifications is more than four times the carbon plus nitrogen, because experiments show that sometimes understabilization occurs. This is due to the influence of oxygen and sulfur having already formed compounds with the titanium, and to less-important kinetic factors that have prevented TiC formation.
The graph shows the time-temperature-transformation (TTT) curve for an unstabilized 430-type alloy with carbon plus nitrogen of 0.08%.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Heat Treating of Ferritic Stainless Steels ⇒ Stabilization
Stabilization is generally considered to be the simple gettering of carbon and nitrogen by a suitable carbide former such as titanium or niobium. Stabilization is essential for ferritic stainless steels to avoid the precipitation of grain boundary carbides.
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One Minute Mentor: Metallurgy of Ferritic Stainless Steels
May 12, 2016
Source:
One Minute Mentor: Metallurgy of Ferritic Stainless Steels
Chromium stabilizes the ferritic structure at high temperatures, but some austenite can form at high temperature in steels with 12% chromium and a low or medium percentage of carbon, as shown in the graph. The graph shows the effect of chromium additions on the extent of the austenite phase field in the iron-carbon system.
Carbon and nitrogen added together also produce about the same effect as carbon alone, which means that a fully ferritic stainless steel at elevated temperatures is not possible below 20% chromium without refining to remove carbon and nitrogen.
In addition, because chromium is a strong carbide former, the presence of carbon causes the formation of chromium carbides. This depletes the amount of dissolved (in solution) chromium that is needed to create the corrosion-resistant oxide layer of a stainless steel.
Volume 4D, Heat Treating of Irons and Steels ⇒ Heat Treated High-Alloy Steels ⇒ Heat Treating of Ferritic Stainless Steels ⇒ Metallurgy of Ferritic Stainless Steels
Chromium stabilizes the ferritic structure at high temperatures, but some austenite can form at high temperature in steels with 12% chromium and a low or medium percentage of carbon, as shown in the graph.
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