A R C H I V E S

o f

F O U N D R Y E N G I N E E R I N G

Published quarterly as the organ of the Foundry Commission of the Polish Academy of Sciences

ISSN (1897-3310)Volume 9

Issue 1/2009121-124

27/1

Defining the relation between mechanical properties and ultrasonic wave velocity in spheroidal cast iron manufactured

in the foundry Metal-Odlew s.c.

W. Or owicz, M. Tupaj, M. Mróz E. Guzik J. Nykiel, A. Zaj c, S. Piotrowski Department of Casting and Welding Technical University of Rzeszow,

35-959 Rzeszów, ul. W. Pola 2

University of Science and Technology, Faculty of Foundry Engineering, 30-059 Kraków, ul. Reymonta 23

Cast Iron Foundry Metal-Odlew S.C., ul. Kwiatkowskiego 1, 37-450 Stalowa-Wola

Received 26.02.2009; accepted in revised form: 30.03.2009

Abstract This work presents results of ultrasonic evaluation of mechanical properties of spheroidal cast iron manufactured under the production conditions of Metal-Odlew s.c. Tests were conducted on wedge casts which were used as samples for tensile tests, a map of distribution of longitudinal ultrasound wave velocity was determined for the cast wedges. The tensile tests were conducted and values of longitudinal ultrasound wave velocity were determined in the place where the sample was broken. Relations between the mechanical properties and the velocity of longitudinal ultrasonic wave cL were determined. Keywords: spheroidal cast iron, mechanical properties, ultrasonic control index

1. Introduction

The cast iron foundry Metal-Odlew s.c. produces a wide range of non-alloy spheroidal cast iron castings. The increasing competence in the market of spheroidal cast iron castings manu-facturers forces us to use modern quality control techniques. This group of techniques includes an ultrasonic method for the assess-ment of mechanical properties (UTS, YS, Elongation) [1-11].

The aim of this study was to establish relations between mechanical properties (UTS, YS, Elongation) and ultrasonic wave velocity.

2. Experimental conditions The tests were conducted on 19 cast iron melts of the fol-

lowing composition: 3,5-3,8% C, 2,5-2,8% Si, 0,40% Mn, max. 0,07% P, max. 0,023% S, 0,2-0,3% Cu, max. 0,06% Cr, 0,038-0,050% Mg. The alloy was prepared in an induction furnace PIT 1,6.

Spheroidization and modification of the case iron were conducted with the FeSiMg9 master alloy in the KOZ-Q-2Mg ladle with crucible top. To determine the influence of the filling time on the cease of spheroidization effect, and thus the change of graphite precipitation shape, the wedge forms were filled after different times of keeping the liquid alloy in the pouring ladle.

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The feeding elements were rejected of the castings and plates were obtained for testing the structure and ultrasonic wave velocities (Fig. 1). The plate surfaces were milled to have the opposite surface parallel. This operation was conducted to prepare the plates for ultrasonic tests (Fig. 2). Velocity of the longitudinal ultrasound wave was measured by applying the head in the points between point A and point B.

Fig. 1 Wedge casting for testing

Fig. 2. Diagram of measurement of the longitudinal ultrasound

wave velocity in the plates of which the samples for ten-sile strength tests were obtained

Velocities of the longitudinal ultrasound wave were

measured with an Echometer 1073 VS with a head 10.4/6 PB 4. Samples for tensile testing were made of the plates after ultrasonic tests. Tests of ultimate tensile strength, yield strength and elonga-tion were conducted on UTS 250.4.

Then, the relation was worked out a dependence for evaluation of UTS, YS and elongation out of the longitudinal ultrasound wave measurements.

3. Experimental results An example distribution of the longitudinal ultrasound

wave velocities along the plates, from A to B (fig.2) has been presented in Fig. 3. Figure 4 presents an example microstructure of plate material of which samples for the tensile tests were made.

Results of tests of the longitudinal ultrasound wave veloc-ity cL and the ultimate tensile strength UTS, yield strength YS and elongation in the area of sample breaking are presented in Table 1.

The relation between the ultimate tensile strength UTS and the velocity of longitudinal ultrasonic wave cL has been pre-sented in Figures 5.

a)

b)

c)

Fig. 3. Distribution of the ultrasonic wave velocity cL along the

plates of which samples for tensile tests were taken: a) sample 1, b) sample 6, c) sample 19

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a) b) c)

Fig. 4. Microstructure of samples after mechanical characteristics tests; a) sample 1, b) sample 6, c) sample 19. Non-etched polished sec-

tions, magn. x 200

Table 1. Results of the mechanical properties (UTS, YS and elongation) and longitudinal ultrasound wave velocity in the place where the sample was broken.

Mechanical properties No. UTS,

MPa YS, MPa Elonga-tion, %

Longitudinal ultrasound wave ve-

locity cL, m/s 1 486 312 19,4 5636 2 490 313 18,7 5639 3 496 318 17,9 5644 4 504 322 16,6 5649 5 509 327 16,3 5651 6 510 331 16,3 5655 7 515 334 15,8 5658 8 519 336 15,5 5664 9 524 337 15,2 5666

10 530 342 15,0 5670 11 536 347 14,8 5674 12 542 349 14,5 5678 13 546 352 14,4 5681 14 551 355 14,3 5687 15 553 359 14,0 5690 16 559 364 13,6 5691 17 562 374 13,3 5695 18 567 380 13,1 5699 19 575 390 12,5 5708

Fig. 5. The relation between the ultimate tensile strength UTS and

the velocity of longitudinal ultrasonic wave cL

The expression describing the relation between the ulti-mate tensile strength UTS and the velocity of longitudinal ultra-sonic wave cL has the following form:

UTS = 1,257 cL – 6599,7, R = 0,99 (1)

The relation between the yield strength YS and the veloc-

ity of longitudinal ultrasonic wave cL has been presented in Fig-ures 6.

Fig. 6. The relation between the yield strength YS and the veloc-

ity of longitudinal ultrasonic wave cL

The expression describing the relation between the yield strength YS and the velocity of longitudinal ultrasonic wave cL has the following form:

YS = 1,03 cL – 5483,1, R= 0,98 (2)

The relation between the elongation and the velocity of longitudinal ultrasonic wave cL has been presented in Figures 7.

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Fig. 7. The relation between the elongation and the velocity of

longitudinal ultrasonic wave cL

The expression describing the relation between the elon-gation and the velocity of longitudinal ultrasonic wave cL has the following form:

% Elongation = - 0,085 cL + 495,4, R= 0,97 (3)

The results obtained are characteristic of the high values of the correlation coefficient, which suggests that they are useful for the needs of the foundry where the tests were conducted.

Formulas (1-3) form the basis of developing nomograms characteristic for the Metal-Odlew foundry, which are going to be used in the non-destructive control of spheroidal cast iron casting diagnosis. An example nomogram has been presented in Fig. 8.

Fig. 8. The relation between the ultimate tensile strength UTS and

the velocity of longitudinal ultrasonic wave cL

4. Conclusions

Tensile strength, yield strength and elongation of the spheroidal cast iron manufactured under the conditions at the Metal-Odlew s.c. foundry are in linear dependency with the longi-tudinal ultrasound wave velocity. Increase of the tensile strength and yield strength are accompanied by the increase of longitudinal ultrasound wave velocity. The increase in elongation is accompa-nied by the decrease of longitudinal ultrasound wave velocity. This dependence is characteristic of a high correlation coefficient. This proves that it is possible to use it in practice.

Nomograms have been developed to assess tensile strength, yield strength and elongation from the longitudinal ultrasound wave velocity. These nomograms will be a basis for acceptance at the non-destructive quality control of spheroidal cast iron castings in the conditions at the Metal-Odlew foundry.

References

[1] Voronkova L.V.: Ultrasonic testing possibilities of cast iron ingots. ECNDT Th.2.2.3, 2006, 1-13.

[2] Areste S.: Kontrole par ultrasonic properties mechaniques des fonts. 8 World Conference on NDT, Cannes, IC10, 1976, 6-11.

[3] Guo X.: A statistical study on the relationship between tensile strength and ultrasonic velocity of cast iron. Interna-tional Journal of Cast Metals Research, 2003, vol 16, 221-226.

[4] Lener S.Y.S.: Evaluation of structure and properties of gray iron PM castings using NDT technique, AFS Transactions, 103, 1995, 151-155.

[5] Li H., Griffin R.D., Bates L.E.: Gray iron property meas-urements using ultrasonic techniques. AFS Transactions, 05-125(05), 2005, 1-11.

[6] Kovacs B.V.: Prediction of strength properties in ADI through acoustical measurements. AFS Transactions, vol. 101, No 80, 1993, 37-42.

[7] Lerner Y.S., Vorobiev A.P.: Nondestructive evaluation of structure and properties of ductile iron. AFS Transactions, vol. 106, No 12, 1998, 47-51.

[8] Or owicz W.: Zastosowanie ultrad wi ków w odlewnictwie. Solidification of Metals and Alloys, PAN Katowice, 2000, Vol. 2., No 45.

[9] Fallon J.: Practice and problems during ultrasonic examina-tion of defects in iron castings. The Foundryman. April, 1991, 140-144.

[10] Fuller A.G.: Evaluation of the graphite form in pearlitic ductile iron by ultrasonic and sonic testing and the effect of graphite form on mechanical properties. AFS Transactions, vol. 85, No 102, 1977, 509-526.

[11] Or owicz W., Opiekun Z., Gedeonowa Z., Tresa D.: Wp yw warunków ulepszania cieplnego eliwa sferoidalnego na warto wska ników kontroli ultrad wi kowej. 23 Krajowa Konferencja Bada Nieniszcz cych, 1994, s. 89-96.

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