Casting Quality and Yield Improved by Simulation

International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 312

(ICCOMIM - 2012), 11-13 July, 2012

ISBN 978-93-82338-04-8 | © 2012 Bonfring

Abstract--- Casting produced by a foundry is acceptable if its quality level as required by the customer’s

specifications is found satisfactory. Otherwise the casting is termed as defective; each casting rejected contributes to

the wastage and loss of value to the foundry. A sound casting involves systematic blend of experience and

engineering basics. For improving cast metal yield, optimize the gating system design, optimise mould filling, avoid

shrinkage scrap, voids, hot tears etc. Casting simulation packages were found to be of immense help. With the

advent of modern computing facilities, application of some popular commercial software as casting simulation tools

has become widely accepted within the foundry industry. The aim of the present paper is to produce defect less

castings by simulation of sand casting phenomenon for this a case study on steel component was carried out using

ProCAST, a commercial finite element solver developed by ESI group. Observation of the simulation results was

carried out experimentally. Efforts were made to improve the yield of castings, minimize the shrinkage porosity,

casting parts resulting in lower cost and higher productivity.

Keywords--- Simulation, Mould Filling, Solidification, Quality and Yield

I. INTRODUCTION

OST of the steel foundries must melt about twice as much steel as will be shipped as finished product. The

additional metal is primarily present in risers, which provide feed metal that helps prevent holes or voids from

forming inside the casting as it solidifies. This paper is identifying techniques for decreasing the size and number of

risers required to produce quality castings, and high yield. Metallurgical phase transformation plays a vital role in

the solidification of castings [1]. Computer simulation of casting solidification of metals and alloys is a complex

phenomenon [2,3]. The assumptions and constraints used for simulation are considered as a vital one [4,5]. In the

casting process, the metal–mould interface will have an air gap which affects the dissipation of heat flow from the

casting to the mould [4,6]. But the application of pressure during the solidification process reduces the air gap and

forms a tight contact between the casting and the mould [7,8]. This condition releases the heat at a faster rate and

produces fine grain structured castings [9]. To identify the conditions and optimum values, simulation of

solidification process is done by running indigenously developed computer software for the casting process selected

for investigation [10,11]. The program output provides the details on time-temperature profile and heat transfer

coefficient values which plays a key role in the effective design of castings [11,12].

1.1. Applications of Casting Solidification Simulation Software Programs Casting solidification simulation software‟s are in regular use by aluminium, copper, iron and steel foundries

using processes ranging from green-sand, resin-and shell-bonded sand to investment and gravity die casting.

Applications include [13]:1. Large steel castings such as heavy weighing turbine housings and stern frames where

improved yields and reduced fettling costs were achieved.2.Critical high pressure valve castings.3.Repetition

castings such as ductile iron crank shafts, where modelling increases the chance of achieving „right first time‟

methoding, so reducing the lead time for new castings. Solidification simulation software‟s are not only used by

foundry method engineers but also casting designers and purchasers are using the software‟s having experienced

significant improved quality from their simulation software-using suppliers.

1.2. Available Numerical Techniques for Casting Solidification Simulation Process

Some of the well-known casting simulation programs currently available to foundry engineers are listed in Table

P. Prabhakara Rao, Kakatiya Institute of Technology & Science. E-mail: [email protected]

Dr.G. Chakraverti, Mahaveer Institute of Science & Technology. E-mail: [email protected]

Dr.A.C.S. Kumar, P.Indra Reddy Memorial Engineering College.

PAPER ID: MEP16

Casting Quality and Yield Improved by

Simulation P. Prabhakara Rao, Dr.G. Chakraverti and Dr.A.C.S. Kumar

M


(ICCOMIM - 2012), 11-13 July, 2012

ISBN 978-93-82338-04-8 | © 2012 Bonfring

1.2[14].Among these, AutoCAST, MAGMASoft, ProCAST, and SOLIDCast have the largest installation base in

India

Table 1.2: Casting Simulation Programs [14]

Software Program Company and Location

CastCAE CT-Castech Inc. Oy, Espoo, Finland

Castflow, Castherm Walkington Engineering, Inc., Australia

PAM-CAST/ProCAST ESI Group, Paris, France

MAGMASoft MAGMA GmbH, Aachen, Germany

JSCast Komatsu Soft Ltd., Osaka, Japan

SOLIDCast Finite Solutions, Inc., Illinois, USA

MAVIS Alphacast Software, Swansea, UK

AutoCAST Advanced Reasoning Technologies P. Ltd., Mumbai

On estimating the defects in the casting components major portion is because of the design problems and minor

portion is caused by manufacturing. The cost involved is also very high. Casting process simulation and analysis for

various defects is considered to be one of the major productivity tools. Considering the conventional approach

followed in foundries shown in Figure:1.3, i.e. trial and error method, lots of money, energy and time are wasted.

Even then process is not controlled accurately. Foundries mostly follow lot of heuristics which they come out with

their experience in that casting. Process operations and casting are to be controlled in a very accurate fashion. One of

the approaches that can be adopted is simulation, which is now becoming a part of every industry. Computer aided

casting simulation helps us in visualizing the real world environment casting process in a mere few steps of inputs.

Simulation has become an important tool in almost in all foundries. Simulation plays a major role in all casting

stages. The main aim of all the foundry makers will be to produce profitable and high quality components to survive

in this competitive era. This may be one of the reasons “why now a day‟s simulation has become an unavoidable

part of casting production.

II. CASTING PROCESS MODELLING

An engineer designing the particular production technology of a casting has certain possibilities of interfering

with the process of solidification and cooling – among others through proper designing of technological allowances,

internal and external chills, distribution and magnitude of riser heads, assuming optimum temperature of pouring

and chemical analysis of the alloy, and finally through a suitable selection of sand mix. The process of designing the

technology of a casting production can be expanded, modernized and improved through utilization of the

possibilities offered by the introduction of numerical methods in the calculation of solidification and cooling of

metal in a mould.Generally the simulation software has three main parts shown in Figure2.

Pre-processing: the program reads the CAD geometry and generates the mesh,

Main processing: adding of boundary conditions and material data, filling and temperature calculations,

Post processing: presentation, evaluation.

The objective of the present paper is to optimize gating/riser systems based on CAD and simulation technology

with the goal of improving casting quality such as reducing incomplete filling area, decreasing large porosity and

increasing yield. Therefore in this paper a case study on plate casting simulation technology based optimization

framework is presented. Given a CAD model of part design and after its being converted to casting model, the

objective is to evaluate casting design. Then runner and risers are presented parametrically. By varying each

parameters, after analyzing simulation results, the original gating/riser system design will be optimized to improve

casting quality.


(ICCOMIM - 2012), 11-13 July, 2012

ISBN 978-93-82338-04-8 | © 2012 Bonfring

Figure 1.2: Conventional Production Steps in a Typical Sand Casting Process

Figure 2: System of Simulation

Computer simulation based on the design procedures described above have been implemented with one case

study. Let's consider a crusher plate casting for the present study (Figures.2.1 &2.2Shows the 3D model&3D model

of sand block). Used in cement industry made of IS 1030 alloy steel. During simulation of the casting process,

mould filling and solidification are examined and sand casting process are optimized.


(ICCOMIM - 2012), 11-13 July, 2012

ISBN 978-93-82338-04-8 | © 2012 Bonfring

Figure 2.1: 3D Model of Plate Figure 2.2: 3D Model of Sand Block

III. MOULD FILLING AND SOLIDIFICATION SIMULATION RESULTS USING PROCAST

The Procast simulation solved for mould filling and solidification processes at the same time. The discussion

about mould filling is solely based on ProCAST simulation results. The mould filling processes of the initial and

modified gating systems can be visualized from Figures.3.1&3.2. It is found that for every succession of one second

fraction of solid and temperatures are changing (encompasses pouring basin, sprue and runner system, gatings,

casting and feeder) will be filled up. The melt was rising almost uniformly in the cavity of the mould until it was

completely filled up. This is a good filling because it ensures the temperature distribution in the mould will be equal

everywhere just after filling so that solidification rate will be fairly consistent throughout the casting. Equal rate of

solidification will entail uniform shrinkage of the casting to minimize defects such as shrinkage cavities as a result

of non-uniform cooling rate. The temperature distribution and fraction of solid also indicates that during mould

filling, cooling has actually started especially at the end of runner as shown from Figures.3.3&3.4. It can be seen

that down sprue and feeder were filled up simultaneously since their dimensions and shapes are very similar.

Though the down sprue is the entrance of the molten metal, it was not filled up or completely wetted during the

mould filling of cavity. Generally, the mould filling is successful as a result of proper design of straight runner

system. It can be seen that the straight runner and gatings were filled up with in the first few second.

Figure 3.1: Mould Filling Pattern and Temperature Variations of Initial Gating System at Various Stages


(ICCOMIM - 2012), 11-13 July, 2012

ISBN 978-93-82338-04-8 | © 2012 Bonfring

Figure 3.2: Mould Filling Pattern and Temperature Variations of Modified Gating System at Various Stages

Figure 3.4: Solidification Fraction of Modified Gating


(ICCOMIM - 2012), 11-13 July, 2012

ISBN 978-93-82338-04-8 | © 2012 Bonfring

Figure 3.3: Solidification Fraction of Initial Gating System at Various Stages

IV. CONCLUSIONS

Casting simulation is the way of predicting a casting process. The objective function of maximizing the yield,

minimizing shrinkage and minimizing solidification time are all found to be greatly achieved using ProCAST FEA

based software. Simulation should become an indispensable tool in all foundries, minimizing time, energy spent and

money, thus maximizing profit. The plot for various parameters and defects very well gives a good idea for redesign

and re-simulation done with no cost of time. Casting process simulation has become an industry standard. No

foundry that produces high quality castings can consider simulation as unnecessary.

REFERENCES

[1] T. Iida, R.I.L. Guthrie, The Physics of Liquid Metals, Clarendon Press,Oxford, 1988.

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518–525.

[3] M.C. Flemings, Solidification Processing, McGraw-Hill, New York,1974.

[4] ASM Hand Book, Casting, ASM International, vol. 15, 1988.

[5] K. Kubo, R.D. Pehlke, Mathematical modeling of porosity formation in solidification, Metall. Trans. B 16B

(1985) 359–366.

[6] W. Kurz, D.J. Fisher, Fundamentals of Solidification, Trans Tech Publications, Aedermannsdorf, Switzerland,

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[7] H.L. Lee, R.D. Doherty, E.A. Feest, J.M. Titchmarsh, Solidification Technology in the Foundry and Cast House,

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[8] C. Beckermann, Modeling of macro segregation: applications and future needs, Int. Mater. Rev. 47 (5) (2002)

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[9] R. Heine, Principles of Metal Casting, McGraw-Hill, 1999.

[10] J.D. Hunt, Solidification and Casting of Metals, Metals Society, London,1979.

[11] C. Kim, C.-W. Kim (Eds.), Numerical simulation of casting solidification in automotive applications,

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[12] S. Kalpakjian, S.R. Schmid, Manufacturing Engineering and Technology,4th ed., International Edition Prentice-

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[13] The Foseco Foundry man‟s Hand Book, Foseco, revised and edited by John R Brown, 10th ed., Butterworth-

Heinemann, Foseco International Ltd., Birmingham, U.K., 1994.

[14] B.Ravi CAD/CAM Revolution for Small and Medium Foundries 48th Indian Foundry Congress, Coimbatore,

February 11-13, 2000.

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Casting Quality and Yield Improved by Simulation