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As your Metals Partner, it is our goal to educate you on various casting processes. Feel free to browse around to learn more but if you have questions or need to submit an RFQ, please contact us. MetalTek International. Because You Demand More Than Metal.

What Is Duplex Stainless Steel?

Posted by Dave Olsen on 12/30/19 8:22 AM

Duplex stainless steels are alloys with metallurgical structures generally regarded as being approximately equal parts of austenite and ferrite, with a 60/40, 40/60-phase distribution being the envelope widely considered as acceptable. The combination of austenite/ferrite produces alloys with twice the strength of conventional austenitic stainless steels.

Duplex stainless steels are virtually immune to stress corrosion cracking (the Achilles’ heel of common austenitic stainless steels) and are highly resistant to pitting and crevice corrosion. Possessing these characteristics, it is not surprising to find the majority of, but by no means all, applications to be seawater related.  Duplex stainless steels have many uses in offshore oil and gas production and naval equipment, particularly sub-surface.

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Topics: Ferrous Alloys, Duplex Stainless Steel

What Are Ferrous Alloys?

Posted by Dave Olsen on 12/27/19 9:23 AM

Ferrous metals or alloys are metals that consist mostly of iron (Fe). Steel is an iron-based alloy containing typically less than 1% carbon, where iron frequently contains 2% or more carbon. Iron and steel are widely available, strong, cheap, and can be shaped by casting.  Their mechanical properties can be improved by heat treating and, in the case of steels, by working (i.e. rolling or forging). Stainless steels were developed to resist corrosion and generally contain 12% or more chromium, and may contain nickel in any amount up to or even exceeding the chromium content based upon the mechanical properties desired and application.

There are several types of stainless steel. When considering these alloys for use in a corrosive environment, the most widely used method for initial selection is to compare PREn ratings (pitting resistance equivalent number) across materials.  This is calculated using the weight % of key alloying elements present in any particular grade of stainless steel. The formula is:

                                                                PREn = % Cr + (3.3 x % Mo) + (16 x % N)

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Topics: Ferrous Alloys

Alloy Numbering Systems

Posted by Dave Olsen on 10/12/18 11:41 AM

Surfing around the reaches of cable TV the other night, we came across an airing of Atlas Shrugged.  In the book/movie, Hank Rearden has developed a brand new light-weight high-performance alloy for railroads that threatens to revolutionize the industry.  Called “Rearden Metal” (once his career-savvy Marketing guys get a hold of it), Hank is protective of the chemistry and properties of the metal - other than to assert its superiority in the manufacture of train rails.

The burgeoning US rail industry in the late 1800’s was facing Rearden-like conditions.  Steel used in rail manufacture was of inconsistent quality – suppliers differed, manufacturing lots differed, and expectations between buyer and seller differed.  A take-it-or-leave it attitude prevailed.

Enter Charles Dudley, the father of ASTM, now the American Society for Testing and Materials.  Dudley engendered a collaborative process as a means to develop and adopt standards that were acceptable to both producers and users.  What began with railroad steel has expanded through the efforts of ASTM, DIN, BSI, JSA, AFNOR and others to thousands of other materials used in countless applications.

ASTM standards describe the composition of alloys, minimum mechanical properties that the materials must exhibit when test bars are evaluated, and standards for how those tests are to be done.  Customers know what to expect when designing components and suppliers know what properties must be achieved. 

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Topics: Non-Ferrous, Alloy Selection, Ferrous Alloys, Alloy Number Systems

What Is Wear?

Posted by Dave Olsen on 10/10/18 4:37 PM

Walking across a grocery store parking lot, six-year-old Danny stumbled, fell down and did further damage to his already worn jeans.  He looked up with little tears in his eyes and said, “Daddy, maybe you should get me pants made out of steel!”  That got Daddy to thinking: What really is wear and what makes a metal resist it?

Among other qualities, metals are characterized by their toughness and by their hardness.  Toughness is the ability of a material to absorb impact without fracturing.  Hardness is the material’s ability to resist indentation, so typically the harder the material, the better it resists wear.  But hard materials are, generally, not tough materials.  A high impact application with a lot of wear would be a difficult environment.  Metal selection often demands tradeoffs. 

Like Danny’s jeans, wear in metals comes in various forms and can be caused by a variety of events.

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Topics: Non-Ferrous, Ferrous Alloys, Wear Resistance, Wear

What Makes It Stainless?

Posted by Dave Olsen on 10/10/18 4:17 PM

It’s everywhere. Probably more than you notice. It’s a key material in food preparation and food processing equipment. When you are eating, that fork in your hand is probably made of it. It is likely to be the material your sink is made of. And if you watch HGTV you know that no kitchen is complete unless it has appliances made of it. It’s a key component in many industrial applications. We are talking about stainless steel, but it’s probably so familiar that you just refer to it as your old friend, “Stainless”.

But just what makes this popular material “Stainless” and what does that mean?

Stainless steel is a ferrous (iron-based) alloy family that has a minimum of 10.5% chromium.  It has been known for a couple of centuries that adding chromium to a ferrous alloy really improves the material’s resistance to corrosion.  But it has only been in the last century or so that a better understanding of the metallurgy of that combination – more specifically the controlled inclusion of very small amounts of carbon – has allowed stainless steel to become the workhorse family of metals that it is.

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Topics: Ferrous Alloys, Stainless Steel

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