Industrial sand plays a critical role in the production of a wide variety of ferrous and non-ferrous metals and castings and is an essential part of the ferrous and non-ferrous foundry industry. Metal parts and components ranging from engine blocks to pumps and valves are cast in a sand and/or clay mould to produce the external shape, with a resin-bonded core creating the desired internal shape. These are costly components to produce and any defects or flaws found in them can have a devastating result on the foundry. Reworking or scrapping the casting and then having to remelt are extra processes that every foundry should be striving to avoid. Quality sand will help in these endeavours.
Foundries are constantly on the lookout for new sources of sand supply and it is always refreshing to report on a new supplier to the industry, especially if it is a silica sand manufacturer.
At the moment Rhino Quarries has one truck that can deliver 35 to 50 tons per load
“Different foundries have different needs. Shakeout and cleaning processes are a standard operation, but improving performance demands various approaches with new products and maintenance and operating strategies. Cost-conscious foundries, large and small, are looking for every advantage to reduce core, mould, and casting scrap. Most foundries are also concerned about binder consumption. All these things can be related,” explained Robert Kelbrick Junior of Rhino Quarries.
“When a fresh casting leaves its mould, the production process is far from over. In many foundries, systems and equipment for removing cores and sand, inside and out, represent a significant portion of capital and operating costs. The less rework or extra processes that can be avoided are usually governed from the beginning – the mould and the sand.”
“Moulding sand is at the heart of the sand casting process. It must hold a shape well and capture the fine details of a casting, yet be permeable enough to allow gases to escape. Under the strain of having the moulding pattern removed from it, or while it is filled, it cannot crumble or sink on itself. When it is turned upside down it must not lose its form. The parts of a mould have to stay true while clamped together.”
“And moulding sand is just not sand that is dug up out of the ground or mine and then used. That would be a disaster for any foundry. It has to go through a number of processes before it becomes anywhere near to being acceptable to be used in a foundry.”
Rhino Quarries’ aim is to get up to the 10 000 tons per month production figures
“Silica sand, or quartz sand as it is sometimes referred to, used in the manufacture of cores and moulds with synthetic binding agents such as furan and cold-box, must be well-defined and to the greatest extent possible, dust-free. Therefore, a process was developed that involves scrubbing and washing the sand, as well as hydro-screening it, before kiln drying with natural gas and the sorting into the final standard grading.”
“The purpose of this process is to achieve high sintering temperatures, low foreign body content and a high degree of chemical purity, which meet our customers’ requirements in all aspects – both for foundry use as well as for a wide range of industrial purposes. Apart from standard grading the process makes it possible to produce a wide range of special grading tailored to our customer’s needs.”
“Silica sand is quartz that over time, through the work of water and wind, has been broken down into tiny granules. In metal casting silica’s high fusion point (1 760°C) and low rate of thermal expansion produce stable cores and moulds compatible with all pouring temperatures and alloy systems. Its chemical purity also helps prevent interaction with catalysts or the curing rate of chemical binders. Following the casting process, core sand can be thermally or mechanically recycled to produce new cores or moulds.”
Background
“The Rhino Quarry site has been operational for many years, since 2002, and mainly manufactured crushed silica sand for the construction industry and for the manufacture of concrete tiles. It is the main source of material for the tile manufacturing company Rooftile West Rand CC, that was established in 1984.”
The equipment for processing the raw material has been sourced locally but Rhino Quarries have also manufactured their own equipment and are doing the civils and the housing construction too
“Subsequently Rooftile West Rand CC decided to acquire Rhino Quarries (Pty) Ltd in 2002 and the mine continued to manufacture silica sand for the construction and tiling industry. It is an open cast mine situated in Randfontein, a gold mining town in the West Rand of Gauteng, 40 km west of Johannesburg.”
“It is estimated to be able to provide 52 million tons of resource at a tested depth of 30m, guaranteeing a reliable supply of high-quality resources for many years. The quarry is 270 hectares in size and the output at the quarry has been tested to understand the makeup of the resources. The silica sand has been tested to be 94% – 99.8% silica (SiO2).”
“It was by chance that a friend, who works in the foundry industry came to explore the property and realised that we had a very desirable product for the foundry industry. This was only earlier this year.”
“We did our research and decided to invest in the equipment and process to manufacture good quality alluvial silica sand.”
“It is estimated to be able to provide 52 million tons of resource at a tested depth of 30m, guaranteeing a reliable supply of high-quality resources for many years. The quarry is 270 hectares in size and the output at the quarry has been tested to understand the makeup of the resources. The silica sand has been tested to be 94% – 99.8% silica (SiO2).”
“In metal production, silica sand operates as a flux to lower the melting point and viscosity of the slags to make them more reactive and efficient. Lump silica is used either alone or in conjunction with lime to achieve the desired base/acid ratio required for purification. These base metals can be further refined and modified with other ingredients to achieve specific properties such as high strength, corrosion resistance, or electrical conductivity. Ferroalloys are essential to specialty steel production, and industrial sand is used by the steel and foundry industries for de-oxidation and grain refinement.”
“The main properties of silica sand used in moulding and core-making processes are size distribution, clay content, pH, acid demand and refractoriness. Properties such as grain size distribution, grain surface morphology, angularity, flowability, and recoating abilities have a particular importance when determining sand suitability.”
“The sand fineness is represented by AFS number and average grain size. The difference in sand fineness will dictate the smoothness of surface finish in a casting. Silica sand is one of the more widely-used refractory sands in conventional metal casting applications, due to its extensive availability worldwide, and its cost-effectiveness compared with other specialised foundry sands such as chromite, olivine, and zircon sands. Some of the most important foundry properties of silica sand include grain size distribution, grain shape, chemical purity, refractoriness, and thermal expansion. The characteristics of silica sand ensure that resin consumption is minimised, the mould strength is optimised, and the resulting castings are sound and defect-free.”
“To get to the end product that foundries love, the quartz rock that is mined goes through a number of processes. First you blast and collect followed by crushing and shaping of the rock. Screening and separating, further washing, dewatering, sizing and drying are all further processes.”
“Silica sand is also the main raw material for making glass. It can also be used in water filtration and purification, grouts, adhesive, epoxy and specialised cements, refractories, aquariums and ponds and specialised flooring solutions.”
“To get to the end product that foundries love, the quartz rock that is mined goes through a number of processes. First you blast and collect followed by crushing and shaping of the rock. Screening and separating, further washing, dewatering, sizing and drying are all further processes.”
“The equipment for processing the raw material has been sourced locally but we have also manufactured our own equipment, as well as doing the civils and the housing construction. As you know we need to keep the final product as dry as possible so we need enclosures. And of course, removing the fines is an essential process.”
“Our mine property consists of the east bank and the west bank. The east bank is made up of a light red colour material and the west bank is white in colour.”
“We are manufacturing according to AFS 40/45 currently and are busy upgrading the plant to produce AFS 45/55 and AFS 55/65 specifications. In future we will introduce others as required. Concentrating on getting the perfect shape is what the mine is all about at the moment.”
“We are manufacturing according to AFS 40/45 currently and are busy upgrading the plant to produce AFS 45/55 and AFS 55/65 specifications. In future we will introduce others as required. Concentrating on getting the perfect shape is what the mine is all about at the moment.”
“Our first loads went out in June this year and because of the positive outcome we are going into full production now. Our aim is to get up to the 10 000 tons per month production figures but that is down the line.”
“We are only dealing with one foundry at the moment – they initiated this expansion in the company – but will be opening up to the rest of the industry gradually. We have one truck that can deliver 35 to 50 tons per load and will add more as soon as economically viable. But our ‘guinea pig’ foundry is clambering for all that we can produce at the moment. We also have a big interest from a steel maker.”
“Our silica sand is of the highest quality at 94% – 99.8% silica (SiO2). The reserves are enormous so we are here for the long haul.”
For further details contact Rhino Quarries on TEL: 010 595 4689/082 855 1576 or visit www.rhinoquarry.co.za
