Ing. Franco Zanardi MSc Mech. Eng. Zanardi Fonderie ... F Met 07 - F Zanardi.pdf · Franco Zanardi MSc Mech. Eng. Zanardi Fonderie Honorary President . 2 Mechanical properties on

CONGRESSO TECNICO ASSOFOND 2016 10th – 11th November Museo Mille Miglia S.Eufemia (BS)

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Ing. Franco Zanardi MSc Mech. Eng. Zanardi Fonderie Honorary President

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Mechanical properties on separately cast test bars t ≤ 30 mm

Std Grade Rm min [MPa]

Rp0.2 min [MPa]

A5 min [1/100]

K RT unn. [J]

KIC [MPa m0.5]

(KIC/Rp0.2)2

[mm] Matrix

ISO 1083 JS/800-2/S 800 480 2 14 1 As Cast Pearlitic

ISO 17804 JS/800-10/S 800 500 10 110 62 15 Ausferritic

The proof stress (Rp0.2) range from 440 to 510 MPa is interesting for mechanical design, because of a good expected compromise between strength, machinability, notch sensitivity. Following the existing International Material Standards, limitation exists in substitution of steel components with (ISO 1083) conventional As Cast Pearlitic Ductile Iron having Elongation at Fracture not lower than 5%. ADI grades (following ISO 17804) are the traditional conventional solution to overcome this limitation.


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Mechanical properties on separately cast test bars t ≤ 30 mm

Age Std Grade Rm min [MPa]

Rp0.2 min [MPa]

A5 min [1/100]

K RT unn. [J]

KIC [MPa m0.5]

(KIC/Rp0.2)2

[mm] Matrix

70s Fiat 52215 Gh 65-48-05 640 470 5 As Cast Pearlitic Ferritic

70s Fiat 52215 Gh 90-52-05 880 510 5 HT Pearlitic

70s ISO 17804 JS/800-10/S 800 500 10 110 62 15 HT Ausferritic

90s Fiat 52215 Gh 75-45-05 735 440 5 As Cast Pearlitic Ferritic

2005 +GF+ SiBoDur 700 440 8 As Cast Pearlitic Ferritic

2005 +GF+ SiBoDur 800 480 5 As Cast Pearlitic Ferritic

2006 Zanardi IDI LT 800 480 6 HT Perferritic

2006 Zanardi IDI RT 880 510 5 HT Perferritic

2011 EN 1563 GJS/600-10 600 470 10 65 19 As Cast SiSSS Ferritic

In the last millennium, the only non-conventional additional possibilities were the Fiat (52215) grades. In the new millenium, three different new possibilities became available :


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The Fiat grade Gh 65-48-05 has usually been regarded as a pearlitic grade, similar to ISO 800 – 2, with higher elongation. In the 90s, it has been redefined as Gh 75-45-05, maintaining the original definition for practical purchasing purposes. Gh 90 – 52 – 05 is normalized. All these grades could be critical in current production processes, and compromises regarding elongation could be a commercial practice, especially when test probes taken from the casting are required. As far as we understand, +GF+ SiBoDur represents an evolution of the Fiat concept: increasing the Silicon content, a larger amount of reinforced Ferrite is permitted for a given strength level, promoting elongation. IDI is a Zanardi patented material, obtained by salt bath heat treatment of a conventional ferritic ductile iron casting. GJS/600-10 is the fully ferritic grade with very high Silicon content.


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A MINIMUM

Rm – Rp0.2

SHALL BE REQUIRED

FOR EACH GRADE

The graph shows the mimimum tensile properties in the Rp0.2

range 440 – 510 MPa Rm – Rp0.2

However, the MQI is not be sufficient, being necessary to control also the proof stress : for a given Rp0.2 required by the linear elastic design, at least a minimum plastic range (Rm – Rp0.2) shall be assured. This graph show how the previously mentioned materials, having similar proof stress Rp0.2 and similar MQI, show different plastic ranges. It is evident how the very high Silicon ferrritic 600-10 is affected by a short plastic range.


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Rp0.2 440 – 510 Mpa A5 ≥ 5% on Separately Cast Test Bars t ≤ 30 mm

Conventional Si - Zanardi Processes +GF+ SiBoDur Very High Si

As Cast Conventional

Pearlite Promoters

IDI LT 800 – 480 - 6

IDI RT 880 – 510 - 5

Critical Process for A5 ≥ 5%

Fiat 52215 Gh 75 – 45 – 05

EN 1563 GJS/600-10

Fiat 52215 Gh 90 – 52 – 05

Elongation and Charpy Impact Increase Elongation increases, Charpy Impact decreases

700 – 440 - 8 800 – 480 - 5

Fiat 52215 Gh 75 – 45 – 05

EN 1563 GJS/600 - 10

ADI ISO 17804 JS/800-10

Design freedom decreases: Silicon selected for Mechanical Properties

Optimum Design Freedom: Si selected for Impact / Nucleation / Feeding / Graphite Shape

Fiat 52215 Gh 65 – 48 – 05

+GF+ SiBoDur 800 – 480 - 5

Fiat 52215 Gh 65 – 48 – 05


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The previous map shows two different approaches: On the left, the one based on conventional Silicon content, selected following the casting needs as: impact, nucleation, casting feeding, graphite shape. On the right, Silicon is selected for Mechanical Properties, by Solution Strengthening the Ferrite: for a given yield, a larger amount of ferrite is possible, which permits the required elongation. In case of Very High Silicon content, a fully ferritic matrix is obtained. Processes leaded by Zanardi Fonderie (IDI and ADI) are based on salt bath quenching heat treatment to achieve the required mechanical properties. This processes are more expensive, because of the heat treatment, however they offer the best possible design freedom. The Very High Silicon Ferritic Grade 600 – 10 works in a narrow process window, with the risk of porosities in hot spots or chunky graphite in wall thicknesses higher than 60 mm. Despite of the apparent low production cost, this material is not a Commodity : it requires a very skilled foundry, a very good cooperation between designer and foundry since the early stage of the design, and (as far as we suppose) it is limited to relativity uniform casting wall thicknesses. SiBoDur grades are affected to minor limitations, because the matrix is composed by pearlite and moderately Silicon solution strengthened ferrite. However, (as far as we suppose) the claimed mechanical properties require, also in this case, a reasonably uniform wall thickness (bionic design, as it is called by +GF+)


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This graph shows how the IDI heat treatment on a fully ferritic matrix with a conventional Silicon 2.5% enhances the mechanical properties on separately cast test bars Y25, Y50, Y75 in terms of tensile and un-notched Charpy test. On Y50 and Y75 the tensile test results are above the minimum requirements of the lowest grade of ADI. Tensile and Impact properties are similar for the different thicknesses.


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This graph shows how the IDI heat treatment on a fully ferritic matrix with a conventional Silicon 2% enhances the mechanical properties on a real casting, in terms of tensile and un-notched Charpy test. On the heaviest sections, the tensile test results are above the minimum requirements of the lowest grade of ADI for separately cast test bars. Also here, tensile and Impact properties are reasonably similar for the different thicknesses. At this Silicon level, Charpy Impact Energy slows down only at a small extent at low temperatures, similarly to ADI, but at a lower level.


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Thirteen Brinell Hardness measurements, on different points in the cross section of a 72 kg real casting, show how IDI has the lower average hardness, compared with ADI and conventional Pearlitic castings. ADI shows the minimum range. Both the heat treated castings are significantly better than the as cast conventional pearlitic, regarding the hardness control. The half table on the left is based on thirteen results, while the right one is based on twelve, excluding one outlier for each material.


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# Sentence

1 Casting in Ferritic Ductile Iron with NO Addition

2 Ferritic Ductile Iron is the most commonly available casting Commodity

3 Silicon content can be selected as most convenient for the Casting Shape and Working Temperature

4 Casting feeding can be optimized as for Technical and Economical Issues

5 Fettling and Primary Machining can be done at the minimum cost

6 Heat Treatment is required, as for ADI

7 After HT, Mechanical Properties are the best possible for a Ferritic – Pearlitic grade, Brinell Hardness is low, compared with the strength

8 Mechanical Properties and Hardness are reasonably similar in different wall thicknesses

9 Machining is easy and economical, compared with the strength

10 Differently from ADI, Wear Resistance in similar to that of other Pearlitic Ferritic grades and similar surface hardening could be necessary


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ADI Ausferritic Ductile Iron

Low Alloyed (as for max casting wall thickness) Ferritic Pearlitic Ductile Iron

Intercritical or Upper Critical austenitizing and Quenching into a Salt Bath, crossing the Ausferritic nose


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IDI Perferritic Ductile Iron (Interconnected Pearlite and Ferrite)

As Cast Un-alloyed Ferritic Ductile Iron casting, also having Non-Uniform up to Relatively High Thickness

Intercritical Austenitizing and Quenching into a Salt Bath, crossing the pearlitic nose


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Perferritic Bull Eye

Quenching into a salt bath, the perferritic transformation is done in minutes and not in hours, as it happens during cooling in the mold. The perferritic transformation transforms the austenite in pearlite in undercooling conditions. The Carbon mobility is low, hence the Bull Eye shape around the nodules is avoided, the Ferrite is interconnected and reinforced by the Pearlite lamellae. This enables the optimum mechanical properties, without increasing the Silicon content.


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Ing. Franco Zanardi MSc Mech. Eng. Zanardi Fonderie ... F Met 07 - F Zanardi.pdf · Franco Zanardi MSc Mech. Eng. Zanardi Fonderie Honorary President . 2 Mechanical properties on