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Integrated System of Thermal/Dimensional Analysis for Quality Control of Metallic Melt and Ductile Iron Casting Solidification

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Abstract

The main objective of the present work is to introduce a specific experimental instrument and technique for simultaneously evaluating cooling curves and expansion or contraction of cast metals during solidification. Contraction/expansion analysis illustrates the solidification parameters progression, according to the molten cast iron characteristics, which are dependent on the melting procedure and applied metallurgical treatments, mold media rigidity and thermal behavior [heat transfer parameters]. The first part of the paper summarizes the performance of this two-mold device. Its function is illustrated by representative shrinkage tendency results in ductile cast iron as affected by mold rigidity (green sand and furan resin sand molds) and inoculant type (FeSi-based alloys), published in part previously. The second part of the paper illustrates an application of this equipment adapted for commercial foundry use. It conducts thermal analysis and volume change measurements in a single ceramic cup so that mold media as well as solidification conditions are constants, with cast iron quality as the variable. Experiments compared gray and ductile cast iron solidification patterns. Gray iron castings are characterized by higher undercooling at the beginning and at the end of solidification and lower graphitic expansion. Typically, ductile cast iron exhibits higher graphitic, initial expansion, conducive for shrinkage formation in soft molds.

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Abbreviations

TM:

Maximum pouring temperature (°C)

TAL (TGL):

Temperature of austenitic (graphitic) liquidus (°C)

TSEF (TEN):

Temperature of the start of eutectic freezing (nucleation) (°C)

TEU:

Lowest temperature of eutectic undercooling (°C)

TER:

Temperature of graphitic recalescence (°C)

TES:

Temperature of the end of solidification (end of solidus) (°C)

TEM:

Maximum recalescence rate (°C/s)

T st :

Stable (graphitic) eutectic equilibrium temperature (°C)

T mst :

Metastable (carbidic) eutectic equilibrium temperature (°C)

ΔT s :

Range of equilibrium eutectic temperature (ΔTs = Tst − Tmst) (°C)

ΔT m :

Maximum degree of undercooling (ΔTm = Tst − TEU) (°C)

ΔT r :

Recalescence (ΔTr = TER − TEU) (°C)

τ ES :

Duration of eutectic solidification (s)

τ ts :

Duration of total solidification (s)

τ dM :

Maximum dilation position (s)

τ dr :

Time of dilation recalescence (contraction curve) (s)

τ er :

Time of eutectic recalescence (cooling curve) (s)

τ t :

Time between mold filling and the end of solidification (s)

(Δt)ES :

The disparity between the moments of the end of solidification indicated by first derivatives of cooling and contraction curves

FDES:

Minimum values of the first derivative of cooling curves at the end of eutectic solidification (°C/s)

FDESC:

Minimum values of the first derivative of contraction curves at the end of eutectic solidification (%/s)

(ε di)max :

Maximum initial expansion value (%)

(ε di)TEN :

Expansion at the initial start of eutectic freezing (nucleation) (%)

(ε di)TES :

Expansion in the final moment of eutectic freezing (%)

(ε di)ES :

Expansion value at the end of eutectic solidification established by the first contraction curve derivative (%)

ε ap :

Contraction prior to pearlite transformation (%)

ε dp :

The pearlitic dilation (%)

TEM(e):

Maximum rate of eutectic dilation (%/s)

MP:

The main derivative peak position relative to TL (before TL, it is positive) (s)

Ir(e):

First derivative integral of the contraction curve during eutectic dilation

It(s):

Total integral of the first contraction curve derivative (prior to pearlitic contraction)

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Acknowledgments

This work was partially financed by a grant of the Romanian National Authority for Scientific Research and Innovation, CNCS/CCCDI—UEFISCDI, Project Number PN-III-P2-2.1-PED-2016-1793, within PNCDI III.

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Authors and Affiliations

  1. Universitatea Politehnica din Bucuresti, Bucharest, Romania

    Stelian Stan, Mihai Chisamera, Iulian Riposan, Loredana Neacsu, Ana Maria Cojocaru & Iuliana Stan

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  1. Stelian Stan
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  2. Mihai Chisamera
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  3. Iulian Riposan
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  4. Loredana Neacsu
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  5. Ana Maria Cojocaru
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  6. Iuliana Stan
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Correspondence to Iulian Riposan.

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Stan, S., Chisamera, M., Riposan, I. et al. Integrated System of Thermal/Dimensional Analysis for Quality Control of Metallic Melt and Ductile Iron Casting Solidification. J. of Materi Eng and Perform 27, 5187–5196 (2018). https://doi.org/10.1007/s11665-018-3303-0

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  • DOI: https://doi.org/10.1007/s11665-018-3303-0

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