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Valve Casting Quality

API Denver

April 2009

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SFSA Yield Program

Objective to increase metallic

yield by 10% - Beckermann UI

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Method

Cast series of plates 6 x 3 x L

Radiograph plates

Cut each plate and Mag Particle examine

Simulate solidification of each plate(Is it possible to simulate and predict a specific

quality level?)

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Results of radiographyinterpretation questionable

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Overview2 studies of ASTM x-ray shrinkage rating:

1) Reproducibility and repeatability of x-ray rating

Statistical study of plate x-rays rated 7 different times

How much variability exists in level and type rating?

If one person rates x-ray twice, same rating both

times?

2) Analysis of digitized images of x-rays Scan reference radiographs and production x-rays

Try to correlate defect measurements to x-ray level

Can shrinkage level be determined quantitatively?

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Overview: Reliability and

Repeatability of X-ray Rating

METHODOLOGY

Used x-rays from first steel plate casting

trials:

128 x-rays from 5 different foundries

4 foundries cast 3 T x 6 W plates

1 foundry cast 1 T x 5.5 W plates

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Overview: Reproducibility and

Repeatability of X-ray Rating 7 separate x-ray ratings were obtained for each

x-ray Reader 1 is the original rating--different person

rated x-rays at each foundry

Reader 2 rated the x-rays two separate times

Reader 3 also rated the x-rays two separate

times Readers 4 and 5 each rated the x-rays once

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Results for Unanimous

Agreement in X-Ray Ratings Unanimous agreement in shrinkage type: 37% (47/128)

14 Level 0 (no type)

20 CB 7 CA

6 CC

Unanimous agreement in shrinkage level: 17% (22/128)

14 Level 0 1 Level 1

1 Level 2

1 Level 3

5 Level 5

Unanimous agreement in level and type: 12.5% (16/128)

14 Level 0

2 CB5

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0.0

0.5

1.0

1.5

2.0

2.5

0 1 2 3 4 5

Average X-ray Level Groupings

AverageO

ne-SidedStuden

t-t95%C

onfiden

ceInterval

39 x-rays

35 x-rays

27 x-rays

11 x-rays

8 x-rays

8 x-rays

AverageX-ray

Level