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 1/2009129-132

29/1

Defining the relation between tensile strength and ultrasonic wave velocity in spheroidal cast iron manufactured

in the foundry JAFAR S.A.

W. Or owicz, M. Tupaj, M. Mróz E. Guzik E. Gierut , W. Pilut, A. Zimowski 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

Fabryka Armatury „JAFAR S.A.“,38-200 Jas o , ul. Kadyiego 12

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 FA JAFAR S.A.. Tests were conducted on wedge casts which were used as samples for tensile strength tests, a map of distri-bution of longitudinal ultrasound wave velocity was determined for the cast wedges. The tensile strength tests were conducted and values of longitudinal ultrasound wave velocity were determined in the place where the sample was broken. Relations between the tensile strength and the velocity of longitudinal ultrasonic wave cL were determined. Keywords: spheroidal cast iron, tensile strength, ultrasonic control index

1. Introduction

Fabryka Armatur JAFAR S.A. manufactures spheroidal cast iron fittings for water and sewage systems. Increasing re-quirements towards spheroidal cast iron elements demand non-destructive diagnosing of microstructure and mechanical proper-ties, with the main focus on tensile strength. The traditional method for evaluating microstructure and mechanical properties of wedge samples, used in Polish foundries, is not satisfactory for many demanding customers. They usually determine the places in the cast that require the ultrasonic evaluation and define the range of velocities of longitudinal ultrasound wave that guarantee the required microstructure and mechanical properties. Working out, for a particular foundry, the relation between the microstructure

and the velocity of longitudinal ultrasound wave and the me-chanical properties may become the basis for acceptance of spheroidal cast iron elements [1-5].

The way the cast iron is manufactured influences its sus-ceptibility to ultrasonic diagnosis; therefore, the relations worked out for a particular foundry are useless for another [1].

On account of the above, the aim of this work was to de-termine the relation between the tensile strength and the velocity of longitudinal ultrasonic wave cL in the foundry JAFAR S.A.

2. Experimental conditions

The tests were conducted on 15 cast iron melts of the fol-lowing composition: 3.3-3.9%C, 2.1-3.2%Si, 0.03-0.06%Mn, 0.06-0.08%P, 0.017-0.025%S, 0.01-0.04%Cr, 0.005-0.012%Ni,

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0.01-0.06%Cu, 0.014-0.016%Ti, 0.002-0.004%Mg, 0.001-0.005%Ca, 0.004-0.008%Ce, 0.0003-0.0007%B, the rest Fe. The alloy was prepared in a gas rotary furnace.

Spheroidization and modification of the case iron were conducted with the elastic conductor method in the KDS-2 ladle of a 1000 kg capacity. Then, the liquid metal was poured into ladles of a 80 kg capacity, installed under an overhead conveyor. Those ladles were used to fill production forms and wedge forms placed on the transporter. 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.

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 strength testing were made of the plates after ultrasonic tests. Tests of tensile strength were conducted on P-20.

Then, the relation was worked out a dependence for evaluation of tensile strength 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 strength tests were made.

a)

b)

c)

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

plates of which samples for tensile strength tests were taken; a) sample 1, b) sample 6, c) sample 15

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a)

b)

c)

Fig. 4. Microstructure of samples after mechanical characteristics

tests; a) sample 1, b) sample 6, c) sample 15. Non-etched polished sections, magn. x 200

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

Table 1. Results of the tensile strength tests and longitudinal

ultrasound wave velocity in the place where the sample was broken.

No. Longitudinal ultrasound wave velocity cL, m/s

Tensile strength UTS, MPa

1 5567 496

2 5582 507

3 5597 512

4 5603 518

5 5607 521

6 5609 524

7 5615 527

8 5622 531

9 5632 533

10 5637 544

11 5644 547

12 5649 550

13 5658 558

14 5669 561

15 5686 574

The relation between the tensile strength UTS and the ve-

locity of longitudinal ultrasonic wave cL has been presented in Figures 5.

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

velocity of longitudinal ultrasonic wave cL.

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References The expression describing the relation between the tensile strength UTS and the velocity of longitudinal ultrasonic wave cL has the following form:

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

UTS = 0,66 cL – 3194,29, R = 0,99 (1)

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

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. [3] Li H., Griffin R.D., Bates L.E.: Gray iron property meas-

urements using ultrasonic techniques. AFS Transactions. Paper 05-125(05), 2005, 1-11.

4. Conclusions [4] 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.

The tensile strength of the spheroidal cast iron manufac-tured in the conditions of the foundry JAFAR S.A. is in a linear relation with the velocity of a longitudinal ultrasound wave. In-crease of the tensile strength Rm is accompanied by an increase in the longitudinal ultrasound wave velocity. This dependence is characteristic of the high correlation coefficient. This proves it is possible to use it in practice.

[5] 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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