NDLI: Weld Metal Toughness: Sources of Variation

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Marie, A. Quintana Babu, S. S. Major, Jeff Dallam, Craig James, Matthew
Copyright Year	2010
Abstract	Many material properties are statistical in nature. If one measures the same property of the same material repeatedly, ideally the result is a normally distributed “bell” curve about a mean value. This ideal case does not necessarily hold true for all mechanical properties of interest in steel weld metals. Tensile strength measurements tend to exhibit normal behavior for a given weld metal chemical composition deposited using a reasonable consistent welding procedure, Figure 1a. However, toughness measurements are not nearly as well-behaved or predictable. In a tensile test, assuming a defect free weld, the strength measurement is based on the bulk response of the material throughout the gage length. In a Charpy V-notch (CVN) impact test, again assuming a defect free weld, the toughness measurements are controlled largely by the very local response of the material at the point of highest stress where fracture initiates just below the notch. This paper presents a detailed assessment of a C-Mn weld metal and explains how CVN toughness can vary from less than 20 ft-lbf to over 200 ft-lbf in the same weld, often with test specimens located adjacent to one another in the test weld, Figure 1b. The much localized microstructure features that give rise to this degree of variation are a combined result of chemical composition, welding procedure, pass sequence, and individual welder technique. The evidence suggests that retained austenite in coarse grained regions of the as-deposited weld metal transform to martensite at the CVN test temperature, effectively creating local brittle zones in the weld metal. This example provides basis for examination of a broader range of microstructural discontinuities in steel weld metals and their potential influence on toughness measurement.
Sponsorship	International Petroleum Technology Institute and the Pipeline Division
Starting Page	599
Ending Page	608
Page Count	10
File Format	PDF
ISBN	9780791844212
DOI	10.1115/IPC2010-31402
e-ISBN	9780791838853
Volume Number	2010 8th International Pipeline Conference, Volume 2
Conference Proceedings	2010 8th International Pipeline Conference
Language	English
Publisher Date	2010-09-27
Publisher Place	Calgary, Alberta, Canada
Access Restriction	Subscribed
Subject Keyword	Temperature Welding Metals Mechanical properties Fracture (materials) Steel Brittleness Gages Stress Tensile strength Fracture toughness Fracture (process) Materials properties Impact testing
Content Type	Text
Resource Type	Article

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