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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.