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Title: Quantitative metallographic method for determining delta ferrite content in austenitic stainless steels. Final report

Quantitative metallographic method for determining delta ferrite content in austenitic stainless steels. Final report Delta ferrite is a magnetic form of iron and has a body centered cubic crystal structure. It is often present as a nonequilibrium phase in austenitic stainless steel welds, castings, and wrought materials. The ferrite content of austenitic stainless steel can directly affect its properties, especially weldability and formability. Therefore, it is highly desirable to be able to predict and/or measure the ferrite content accurately. Current magnetic ferrite measuring methods are not applicable when test materials are geometrically small (less than 2.54 mm thick and 6.35 mm wide). Therefore, a standard metallographic test method STM 00107-A was established to determine delta ferrite content in small weldments and base metals of austenitic stainless steel. This standard test method (STM 00107-A) was then performed on several exemplary metallographic specimens to illustrate its capabilities and applications. The results from the exemplary tests were compared and contrasted to metallographic manual point count measurements, Ferritescope measurements, and predicted values calculated from chemical analyses. By utilizing the manual metallographic point count data, an accuracy of +-16% and a precision of +-0.77% were determined for the standard test method. The comparison of Ferritescope data to standard test method revealed that the results obtained by the two methods more » are close at low (0 to 3%) ferrite contents and Ferritscope results are substantially greater at higher (6 to 10%) ferrite contents. The standard test method data compiled from the exemplary weld specimens was noted to be very similar to the predicted values calculated from chemical analyses. It was also shown that because the standard test method utilizes optics the morphology of the delta ferrite particles can be determined. This type of determination is possible only with metallographic methods. « less
Authors:
Publication Date:
OSTI Identifier:OSTI ID: 6239282
Report Number(s):BDX-613-3350
ON: DE86006311
DOE Contract Number:AC04-76DP00613
Resource Type:Technical Report
Research Org:Allied Corp., Kansas City, MO (USA). Bendix Kansas City Div.
Country of Publication:United States
Language:English
Subject: 42 ENGINEERING; 36 MATERIALS SCIENCE; AUSTENITIC STEELS; METALLOGRAPHY; FERRITE; ETCHING; IMAGE PROCESSING; MORPHOLOGY; QUANTITY RATIO; ALLOYS; CARBON ADDITIONS; IRON ALLOYS; IRON BASE ALLOYS; PROCESSING; STEELS; SURFACE FINISHING 420500* -- Engineering-- Materials Testing; 360102 -- Metals & Alloys-- Structure & Phase Studies