AIS AIS Forensic Testing Laboratory, Inc.    Metallurgical Testing
Introduction to Metallurgy...a Metallurgical Tutorial

Welding - Carbon Steels - Stainless Steels - Cast Iron - Super Alloys - Steel - Heat Treating - Corrosion - Galvanic corrosion - Ceramics - Refractories

Basic Metals: Alloy SteelsAlloy steel being forged

Steels that are alloyed are either:

  • High Alloy Steels

  • Low Alloy Steels

High alloy steels have four-application classes:

  • Stainless Steels (Corrosion Resistance) for stress corrosion cracking (SCC).

  • High Temperature Steels (+)1000F These are steels that must have good resistance to high-temperature creep and ruptures. Also important to be resistive to oxidation and corrosion. Stainless steels also fit this class except ferritic.

  • Low Temperature Steels (-)300F This class of application is suited best for stainless steels of the austenitic type. Low carbon high alloy steel do not perform well at -40F unless steps are taken to alter the steel characteristics, and regardless of purity and chemical character (-) 300F is where performance is unacceptable. Austenitic type is very suited for this -300F temperature with alloying.

  • Wear Resistance Steels - These are done by diffusing gases like carburizing, sulfiding, siliconizing, nitriding, and boriding to mention a most methods. Other methods are through alloying and coating the high alloy steels.

  • Electro-magnetic Steels - These are transformer and generator plain carbon steels including iron cores. Permanent magnetic also fit this class. Silicon (Si) is an important alloy.

  • Tooling Steel - These are cutting tools, forming dies, and shearing tools; they can be hardened and will have a high carbon content. Tools like chisels can have carbon (C) content up to 1.10% and razor blades has high as 1.40% C. Tools will have different chemical composition for low speed tooling (including pneumatic powered) and high speed tools where abrasion is important.

Low alloy steels, typically plain carbon steels that have only two-alloys elements but can be as high as five-alloying elements. the majority of the alloying is less tan 2% and in most cases under 1%. Nickel (Ni) can be as high as 5%, but this is an exception and may be found in transmission gearing. In the chemical analysis you will find many more elements but these are incidental to the making of the steel as opposed to alloying to for specific property in the steel. of normally less than 2%

 

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