Study of Regression Relationship Involving Compressive Strength, Resin Addition and Time of Soaking

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International Journal of Engineering Technology Science and Research IJETSR www.ijetsr.com ISSN 2394 – 3386 Volume 3, Issue 9 September 2016

Study of Regression Relationship Involving Compressive Strength, Resin Addition and Time of Soaking of Foundry Sand Samples during Mould Making in a Foundry Unit Benrajesh, Pranab Das,A.Johnrajan(1)&GurumoorthyHebbar Christ University, Mechanical Engineering Faculty of Engineering, Kanmanike, Bangalore (1)VIT University, Vellore

ABSTRACT Achieving proper strength in sand molds by varying addition of resin and soaking period for casting metal is a matter of experience by the operating personnel. Therefor Regression analysis was carried out to know the role of resin addition and time of soaking as dependent parameters on the independent parameter namely compressive strength of the sand mold samples . Cylindrical samples were made with varying amount of resin additions ( upto a maximum of 1.3% ) with varying soaking period ( up to a maximum of 24 hours ). Initially an exponential relationship involving compressive strength and resin additiononly (S= k Rnwherewhere S= compressive strength in kg/sq.cm, k= numerical constant (presumed constant) R= Resin percentage and n= empirical constant ) were tried. The data points exhibited wide variationswithout having any relationship . Therefore, an exponential relationship involving both resin addition and time of soaking with compressive strength of the samples was made ( S= kRαtβ , where S= compressive strength, R= resin percentage and t=time of soaking at a fixed resin percentage, and α and β are empirical constants ). It was observed that the values of ‘ α ‘ as regards relationship between resin addition and compressive strength was same ( followed the same curve ) and were therefore of no significant importance. As regards relationship between time of soaking and compressive strength (βvalues )distinct relationship between compressive strength and time of soaking was observed such that the lower soaking period gave less compressive strength in comparison to that subjected to higher soaking period.This analysis indicates that time of soaking of moulds is more important in achieving strength and the addition of resin has no significance as regards strength of the moulds are concerned. key words: mold, regression analysis, resin

1.INTRODUCTION In sand mold making , the sand particles are held together by a typical mixture of 90% silica sand, 3% water and 5% - 7% clay. Other bonding agents can be used in place of clay, including organic and inorganic binders. Additives (catalysts or hardeners) are sometimes combined with the mixture of sand and binder to enhance properties such as strength of the mold [1]. Sand casting with these mixtures is called resin bonded sand casting. It is claimed that it can give better dimensional accuracy on cast product and strength than the green sand process [2]. Resin bonded sand consists of 93-99% silica and 1-3% binders [3]. Binders give bond, cohesion and strength to the mixed sand during mold ramming to ease the shaping process and retain it shape under pressure, temperature and erosion of liquid metal during pouring process A highly alkaline phenolic resin is used as binder in no bake process [4]. No bake process is another name for resin bonded sand casting in which resin is self-setting at room temperature.In phenolic-ester no bake mold, 1.5 – 2% of the phenolic resin (based on the weight of sand) is first blended into the sand, followed by about 20% of an ester (based on weight of resin) [4]. The reaction between the ester and phenolic resin leads to curing and solidification. Since the binders are free of nitrogen and sulfur, it gives strength advantages for steel, nodular iron and aluminum casting.Additives arealso added to the molding components to improve: surface finish, dry strength, refractoriness, and "cushioning properties".Up to 5% of reducing agents, such as coal powder, pitch, creosote, and fuel oil, may be added to the molding material to prevent wetting (prevention of liquid metal sticking to sand particles, thus leaving them on the casting surface), improve

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Benrajesh, Pranab Das, A.Johnrajan(1) & Gurumoorthy Hebbar


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