EVALUATION OF MOULDING PROPERTIES OF SAND IN NIGER STATE FOR ALUMINIUM CASTING AND OTHER FOUNDRY APPLICATIONS

ABSTRACT

Evaluation of moulding properties of sand in Niger State for casting and the effects of the sand mould on mechanical properties of aluminium cast is presented. The moulding properties includes; Permeability, Compactibility, Moisture Content, Green and Dry Strengths. Sand samples from five locations in Niger State, Zungeru, Tungan Mallam, Wuya, Gidan Mangoro and Tagwai Dam area villages were collected and evaluated according to the American Foundry Society (AFS) standard. Mechanical (Tensile and Hardness) and Metallographic tests were carried out on the aluminium cast specimen obtained from the five different sand samples to verify the sand test results. All the results of the five different sands evaluated were compared with that of satisfactory standard mould property ranges for sand casting, the values of result of the five sands evaluated were found to be out of range with that provided for aluminium alloy casting. Mechanical and Metallographic tests of the aluminium samples produced from the five different sand were carried out to validate the results from the sand tests. The sand tests results gave values that ranged between for Permeability 72.08 – 96.85, Green Compressive Strength 12.50 kN/m2  – 48.67 kN/m2 and 76.00 kN/m2  – 116.67 kN/m2  and Dry Compressive Strength 85.00 kN/m2 – > 650.00 kN/m2, While the satisfactory mould property ranges for sand casting for aluminium are Permeability 10-30, Green Compressive Strength 50 – 70 kN/m2, Dry Compressive Strength 200-550 kN/m2. The sand test results however of Wuya, Zungeru and Tagwai Dam area villages were found to be within the range for casting Heavy Grey Iron as provided by standard mould property range for sand casting, while the result of Gidan Mangoro village was in the range for Malleable Iron castings. Tungan Mallam sand results did not provide values within the range provided by the standard mould property range for sand casting in its natural state as provided in the table of standard.

CHAPTER ONE

1.0       INTRODUCTION

1.1       Background of the Study

The greatest problem the Production Engineer faces is choice of solving problems with maximum output in terms of quality, quantity and cost of production. Manufacturing process is a production process which involves directly the change of form or dimensions of a finished part being produced from other forms or raw materials to produce the usable product. Manufacturing process is divided into six major groups namely Primary Shaping Processes  [casting,  powder  metallurgy,  plastic  technology,  bending  and  forging], Secondary Machining Processes [turning, threading, milling, drilling and gear cutting], Metal Forming Processes [forging, rolling, hot spinning, extrusion and drawing], Joining Processes [welding, brazing, soldering, riveting and bolt joints], Surface Finishing Processes [honing, super finishing, electroplating, metal spraying, painting and sand blasting] and Processes Effecting Change in Properties [annealing, normalising, hardening, tempering and grain refining], Singh (2006).

Primary shaping processes are manufacturing processes were a product is produced from an original raw material. Primary shaping processes produces finished products or parts into its usable or working form, Singh (2006). Casting is one of the earliest forms of metal forming processes and is defined as a technique of pouring metal in liquid form into a cavity of the shape desired called the mould, and allowing it to solidify, Khan (2005). Bala et.al (2013) noted that melting temperatures and solidification of metals occurs at a steady temperature.  Solidification  starts  at  melting temperature  and  forms  a steady straight path on the cooling curve during the solidification as a result of the evolution of the latent heat of fusion. The chilling effect of the mould wall produces a thin skin of solid metal at the boundary instantly after pouring. Randomly shaped grains of tiny size form close to the mould wall, and big columnar grains positioned in the direction of the middle of the cast form afterword. The solid-liquid boundary goes completely all the way in the molten metal from the mould walls internally to the middle. Once solidification occurs at any position cooling continues. The cast is removed from the mould and cooling starts at ambient temperature.

The other primary shaping processes have been proven severally compared to casting to have  the  disadvantage  of  material  waste,  high  cost  implication,  stress  distribution problems like cracks, fatigue and creep as compared to products of casting. Casting processes is divided into different groups which are permanent and expendable mould pattern that includes sand casting, squeeze casting, die casting etc. While stressing the relevance of casting, Khan (2005) stated that, casting process is extensively used for the manufacture of products  for almost  all  industries  such  as  agriculture,  construction, cement, chemical, petro chemical, aircraft, ship building etc. This clearly shows that the scope of casting cannot be over emphasized given its wide area of coverage and utilization. Sand casting, otherwise referred to as sand moulded casting, is a casting technique whereby sand is used as the mould material. It is reasonably cheap and has sufficient refractory property for steel foundry use. Khan (2005) identifies sand casting as the most widely used casting process in the casting industry, worldwide. Abolarin et.al (2010) share the view in stating that sand is the main moulding component utilized for casting globally for the production of variety of casts both ferrous and non ferrous metals, because sand has the properties essential for foundry application. In explaining the reason for the high utilization of sand casting Aweda and Jimoh (2009) noted the particle size of sand which is packed finely and tightly together provides an excellent surface for the mould.  Sand  moulds  are  designed  to  have  a  good  collapsibility and  accommodate shrinkage of cast metal in the process of solidification, which is to prevent defects in the cast metal. Sand casting also provides good surface finish because the molten metal poured in the mould flow freely and is closely packed with good permeability for better final cast finish.

The much desired development of Nigeria can only be achieved through industrialization and the back bone of any industrialized country is very much dependent on its production capacity from the availability of raw materials to the technology utilized in transforming the raw materials to finished products. Nigerian economy over the years has continue to depend on oil as the major source of revenue neglecting other sectors that would boost its industrial  and  economic  development  as  highlighted  by Abolarin  et.al  (2004).  The abundance of mineral deposits all over Nigeria is greatly underutilized, sand being one of them. Asuquo et.al (2013) in investigating the nature and quality of Zircon sand from Jos Plateau State and sand samples from Idah, Kogi State for foundry application, noted that Nigeria is blessed with large quantity of natural resources that have numerous applications which can be used in producing expensive High Performance Engineering equipment, which are not being utilized to the optimum.

1.2       Problem Statement

Nigeria is aiming to be among the twenty most developed nations by the year 2020, this can only be achieved through rapid industrialization and this cannot be achieved without sufficient production that would serve the country and even provide for export to other nations. Sheidi (2012) noted that the production of castings is necessary for the development of every nation, as almost all human aspect is reliant upon casting for equipment in construction, transportation, petroleum, mining, farming, and in water supply. Nuhu (2008) noted the significance of Ajaokuta steel rolling company situated in Kogi state operating at full capacity will draw a large number of ancillary and small to heavy industries to the region that require large foundry plants for the spare and completely knocked down parts. Niger state with a land mass of 99,000 km2 situated in central Nigeria and also the largest state in terms of land mass in Nigeria has tremendous potential in the casting industry if only it would be harnessed properly. The growing desire for increase in local content in the production industries and the quest for rapid industrialization in Nigeria necessitates that more and more local materials are being sought after to replace imported materials which Niger state provides.

1.3      Aim and Objectives of the Research

1.3.1    Aim of the Research

This research work aim at evaluating the moulding properties of sand from Zungeru, Wuya, Tungan Mallam, Gidan Mangoro and Tagwai Dam all in Niger State for casting and also to test the effects of the moulding sand evaluated on the mechanical properties of aluminium casts.

1.3.2    Objectives of the Research

The objective of the research is to identify whether the five selected area where the sand samples were taken from in Niger State meet the requirement for moulding and can be utilized for casting as well as to determine the effects of the moulding sand on cast aluminium.

1.4    Justification of the Study

Clearly, a preference exists for imported sands and clay over local ones by most foundries in Nigerian cast industries as stated by Ayoola et al (2010). This might not be unconnected with the processes involved in the acquisition, preparation and other processes of the sand for it to be suitable for casting, coupled also with the fact that little effort has been put in identifying and exploring local sands to see their suitability and practical ability in commercial quantity. The porosity, sizes and treatment of sand material affects the permeability, curing time and the quality of cast produced. Musa et.al (2012) conducted a comparative analysis of some selected clays in Niger state to investigate their refractory properties which gave satisfactory results. Igbokoda clay in south west Nigeria had shown good binding property for synthetic sand moulding, Loto and Omotoso, (1990). Abolarin et.al (2010) utilized river Niger sand with Tudun-Wada clays as binder which gave them a satisfactory result with the clay acting as substitute for bentonite used in foundry mould. This shows clearly that more research is required to find more alternatives to imported sands. Ayoola et.al (2010) found Oshogbo sand in Osun state suitable for use in foundry application for sand casting. Asuquo et.al (3013) investigated the characteristics of Zircon sand and the effect on foundry casting utilizing sand sample from Idah, Kogi state and Zircon sand from Jos, Plateau state which gave positive results. Aramide et.al (2011) in the quest of optimizing local silica sand from Ilaro, Osun state investigated the possibility of using recycled local Nigerian with the addition of binders in which desired results were obtained.

Clearly a lot of prospects exist for the utilization of local Nigerian sand in casting. Zungeru, Wuya, Tungan Mallam, Gidan Mangoro and Tagwai Dam area sand all in Niger State would provide alternate source for sand cast utilization considering its span and abundance. This would promote the local content initiative of the government and cut cost of procuring sand, this project is focusing on local sand in Nigeria to ascertain if it has sufficient properties to be used for foundry application satisfactorily.

1.5      Research Scope and Limitations

This project work is restricted to sand deposit located in five different locations of Zungeru in Wushishi Local Government Area, Wuya in Mokwa Local Government Area, Tungan  Mallam in  Paikoro  Local Government  Area,  Tagwai Dam area and  Gidan Mangoro in Bosso Local Government Area all in Niger State to test whether the sand samples were suitable enough to be utilized in sand casting of aluminium alloys and other foundry application.

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