the effect of the steelmaking process
TRANSCRIPT
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Macroinclusions
Abstract
European Wind Energy Conference & Exhibition 2010, Tuesday 20 - Friday 23 April 2010, Warsaw, Poland
Microinclusions
Microinclusions
Macroinclusions Microinclusions
Objectives
Methods
Macroinclusions
Conclusions
References
The Effect of the Steelmaking Process
on Steel Cleanliness and
Related Application PerformancePeter Glaws-Researcher • Mick Grew-Presenter
Results
Macroinclusions Microinclusions
1) the steelmaking practice
2) the resultant oxide inclusion distribution
3) the corresponding effect on fatigue
performance.
The focus of this presentation will be on the
relationship between steelmaking practice
and measured oxide inclusion population.
Values of various steel cleanness metrics,
which provide quantitative information on
the macro- and micro-inclusion populations,
are compared in steels produced by different
processes, including air melt, ESR and VAR.
The effects of certain steelmaking process
improvements on cleanliness are also
reviewed.
The presence of oxide inclusions in steel has been shown to have a
significant impact on fatigue performance of load bearing components
manufactured from that steel. It is important to establish some
understanding of the connection between:
Given that:
- Inclusion related rolling contact fatigue failures in tapered roller
bearings have only been found to be caused by large oxide stringers.
- Today’s clean steels have lower concentrations of oxide stringers.
- However, there remains variations in the stringer content between
“clean” steel sources.
Objective:
- Use the appropriate Steel Cleanliness Measurement tool to determine
the effect of steel processing on the macroinclusion population.
Project
Objective 1
Project
Objective 2
Given that:
- Microinclusions, while not usually associated with rolling contact
fatigue failures in bearings, have been found to cause component
failures in other applications experiencing other fatigue loading modes.
- The variation in the microinclusion population in various steel sources
is not well understood.
Objective:
- Use the appropriate Steel Cleanliness Measurement tool to determine
the effect of steel processing on the microinclusion population.
Macroinclusion Cleanliness Measurement Method Deficiencies of Traditional Cleanliness
Measurement Methods
- As steels became cleaner, traditional
measurement methods no longer provided
a reliable correlation with bearing fatigue
performance.
- This was primarily due to the insufficient
inspection volume necessary to detect a
statistically significant number of the oxide
macroinclusions that impacted bearing life.
- The Timken Ultrasonic Test combines the
benefits of large inspection volume and
adequate sensitivity to provide an accurate
measurement of the macroinclusion
population, which correlates with bearing
performance.
Microinclusion Cleanliness Measurement Method
New metrics on Inclusion Population
– Total Oxide Area
– Oxide Stringer Area
– Statistics of Extreme Values (SEV)
– Histograms
• Size, Aspect Ratio, etc.
– Generalized Pareto Distribution (GPD)
– Inclusion Type (composition)
– Inclusion Pattern Recognition
SEM Based Image Analyzer
Generated data on each inclusion
– Location
• Coordinates of inclusion centers
– Geometric
• Size
– Area
– Diameter(s): Length / Width
– Perimeter
– Orientation (direction of DMax)
• Shape
– Aspect Ratio
– Convexity
– Circularity
– Composition
• Rapid (approximate) EDS analysis
• X-ray Counts
Timken has employed recent steel cleanliness measurement technologies to
help make significant reductions in the size of the microinclusion population.
Improvements to air melt 52100 have approached VAR and VIM VAR levels of
cleanliness.
Effect of Steelmaking Process on MicrocleanlinessEffect of Steelmaking Process on Macrocleanliness
Conclusions
Steelmaking process selection does have a significant
influence on inclusion population
Traditional cleanness detection techniques do not
adequately measure or screen steel quality to predict
component life or reduce failure risk.
Process development based on advanced measurement
methods can achieve enhancements to low-cost steelmaking
processes such that they can produce oxide inclusion
populations historically only possible from high-cost (remelt)
processes.
References
J. D. Stover, R. V. Kolarik and D. M. Keener, “The Detection of
Aluminum Oxide Stringers in Steel using an Ultrasonic Measuring
Method,” Mechanical Working and Steel Processing Proceedings,
October 22-25, 1989, ISS, vol. 27, pp. 431-440.
P. C. Glaws, R. V. Fryan and D. M. Keener, “Influence of
Electromagentic Stirring on Inclusion Distribution as Measured by
Ultrasonic Inspection,” Steelmaking Conference Proceedings, Vol 74,
Washington, D.C., Apr. 14-17, 1991, ISS, pp. 24 7-264.
J. D. Stover, “Inclusions and Rolling Contact Fatigue,” Proceedings
of the 2nd International Symposium on Bearing Steels, June 6-8,
1995, Arles, France.
J. A. Eckel, P. C. Glaws, J. O. Wolfe, and B. J. Zorc, “Clean
engineered steels - progress at the end of the twentieth century,”
Advances in the Production and Use of Steel With Improved Internal
Cleanliness, Atlanta, GA, May 4, 1998, ASTM, pp. 1-11.
The Timken Ultrasonic
Test provided
─ Large inspection
volume
─ Strong correlation
with Bearing Life
Utilizing the information
provided by the Timken
Ultrasonic Test,
successive process
improvements were
implemented over the
years to ultimately
produce air melt steels
with extremely low
concentrations of
performance damaging
oxide stringers.