Asking the Big Questions The five top-rated presentations at the 115th
Can metal castings exhibit the mate- rial properties of wrought alloys? Tese were among the questions
W Addressing Quality
In “Understanding Quality in Alu- minum Castings,” Geoffrey Sigworth, Foseco, Cleveland, examined the “pervasive yet elusive” concept of metal quality. Sigworth began by exam- ining the standard molds typically used to evaluate quality and went on to analyze several numerical indexes and other statistical data that are used to determine quality. Finally, Sigworth offered advice on how to define relative quality in individual facilities.
Conclusions • Finding a scientific basis to evaluate the quality of a casting is important so metalcasters and casting engineers under- stand the relative quality of a delivered casting and whether
asked by the more than 150 presenters at the 115th
Metalcasting Congress,
held April 5-8 in Schaumburg, Ill. Tey were also among the questions asked in the presentations receiving the highest marks by their peers. Five presentations at this year’s con-
gress received perfect (or nearly perfect) scores from their panel of peer review- ers. Following is a look at the questions posed and conclusions reached in each of the five presentations.
Metalcasting Congress tackled important issues and delivered intriguing results. A MODERN CASTING STAFF REPORT
hat does “qual- ity” mean? What is the best way to cast magnesium?
What is the best way to cast magnesium?
• Standardizing quality measures shows a wide range of competence exists in the metalcasting industry. Metalcasters must therefore use improved practices (innovative casting processes and improved degassing, metal filtration and flux- ing) in order to bring their quality up to the highest level.
the caster can improve on it.
• Maintaining the best metal condi- tions for reducing oxide films, porosity and brittle intermetallic phases is the most effective way to inhibit the loss of ductility and tensile strength in castings.
• Weibull statistics (fatigue data from analysis of failure rates) are a powerful tool in helping evaluate the quality of castings produced by a specific combination of metalcasting practices and mold design.
• Proper grain refinement and modi- fication are the primary means of improving the pore size in castings, which are primarily affected by casting solidification rates.
affected by the size of the largest pore, or in some cases largest oxide film, found within it. These condi- tions can be improved through better melt treatment.
Ultrasonic Testing Comes Out on Top According to Robert Tuttle,
• The fatigue life of a casting is most
Saginaw Valley State Univ., Saginaw, Mich., many steel casting facilities have expressed concern about the reli- ability of ultrasonic testing of castings with heavy section thicknesses. Typi- cally, these metalcasters conduct x-ray testing without the same concerns. In “A Gage R&R Study of the
ASTM A609 Ultrasonic Testing Standard,” Tuttle examined the variances he could find among different operators using the test. Would it prove to be less repeat- able than x-ray testing? In the study, five plates were
cast with varying levels of shrink- age defects. Te plates were then x-rayed and ultrasonically tested by five different metalcasting facilities.
Geoffrey Sigworth’s work on quality concluded that the fatigue life of a casting is most affected by the size of the largest pore found within it.
Conclusions • X-ray ratings showed a dramatic variation between metalcasting facilities.
May 2011 MODERN CASTING | 51
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