Refractories Pdf Download
Pamela Olivares
In materials science, a refractory (or refractory material) is a material that is resistant to decomposition by heat or chemical attack that retains its strength and rigidity at high temperatures.[1] They are inorganic, non-metallic compounds that may be porous or non-porous, and their crystallinity varies widely: they may be crystalline, polycrystalline, amorphous, or composite. They are typically composed of oxides, carbides or nitrides of the following elements: silicon, aluminium, magnesium, calcium, boron, chromium and zirconium.[2] Many refractories are ceramics, but some such as graphite are not, and some ceramics such as clay pottery are not considered refractory. Refractories are distinguished from the refractory metals, which are elemental metals and their alloys that have high melting temperatures.
Refractories are defined by ASTM C71 as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above 1,000 F (811 K; 538 C)".[3] Refractory materials are used in furnaces, kilns, incinerators, and reactors. Refractories are also used to make crucibles and molds for casting glass and metals. The iron and steel industry and metal casting sectors use approximately 70% of all refractories produced.[4]
The oxides of aluminium (alumina), silicon (silica) and magnesium (magnesia) are the most important materials used in the manufacturing of refractories. Another oxide usually found in refractories is the oxide of calcium (lime).[5] Fire clays are also widely used in the manufacture of refractories.
Refractories have multiple useful applications. In the metallurgy industry, refractories are used for lining furnaces, kilns, reactors, and other vessels which hold and transport hot media such as metal and slag. Refractories have other high temperature applications such as fired heaters, hydrogen reformers, ammonia primary and secondary reformers, cracking furnaces, utility boilers, catalytic cracking units, air heaters, and sulfur furnaces.[12] They are used for surfacing flame deflectors in rocket launch structures.[13]
Acidic refractories are generally impervious to acidic materials but easily attacked by basic materials, and are thus used with acidic slag in acidic environments. They include substances such as silica, alumina, and fire clay brick refractories. Notable reagents that can attack both alumina and silica are hydrofluoric acid, phosphoric acid, and fluorinated gases (e.g. HF, F2).[14] At high temperatures, acidic refractories may also react with limes and basic oxides.
These are without definite form and are only given shape upon application. These types are better known as monolithic refractories. The common examples are plastic masses, ramming masses, castables, gunning masses, fettling mix, mortars etc.
Refractories may be classified by thermal conductivity as either conducting, nonconducting, or insulating. Examples of conducting refractories are silicon carbide (SiC) and zirconium carbide (ZrC), whereas examples of nonconducting refractories are silica and alumina. Insulating refractories include calcium silicate materials, kaolin, and zirconia.
Insulating refractories are used to reduce the rate of heat loss through furnace walls. These refractories have low thermal conductivity due to a high degree of porosity, with a desired porous structure of small, uniform pores evenly distributed throughout the refractory brick in order to minimize thermal conductivity. Insulating refractories can be further classified into four types:[2]
Delta supplies literally hundreds of proprietary shaped & prepackaged refractory products. Our prepackaged specialty refractories incorporate the latest technologies, such as low cement, ultra-low cement, enhanced flow, "shotcrete", & true self-flowing castables. Along with conventional castables, we offer...
In addition to being resistant to thermal stress and other physical phenomena induced by heat, refractories can withstand physical wear and corrosion caused by chemical agents. Thus, they are essential to the manufacture of petrochemical products and the refining of gasoline.
Refractory products generally fall into one of two broad categories: preformed shapes or unformed compositions, often called specialty or monolithic refractories. Then, there are refractory ceramic fibers, which resemble residential insulation, but insulate at much higher temperatures. Bricks and shapes are the more traditional form of refractories and historically have accounted for the majority of refractory production.
From the simple (e.g., fireplace brick linings) to the sophisticated (e.g., reentry heat shields for the space shuttle), refractories are used to contain heat and protect processing equipment from intense temperatures. In industry, they are used to line boilers and furnaces of all types (reactors, ladles, stills, kilns, etc.).
In addition to specially designed monolithics, tundish linings, ladle products and reheat furnace refractories, URC supplies customized precast shapes such as deltas and engineered fiber components such as ladle preheaters to steel mills across North America.
The former ANH family of companies, including A.P. Green Refractories Co., North American Refractories Co., and Harbison-Walker Refractories Co., is known as a knowledgeable leader in the manufacture and supply of innovative refractories products for a wide range of industry applications presenting, among other things, challenging heat-intensive or chemically corrosive production environments. Building on this strong heritage, the new HarbisonWalker International is reportedly positioning itself as the first and only choice for comprehensive solutions to address the needs of its growing international customer base. It also hopes to reinvigorate the strong bond between the company and both its employees and its customers.
Carolina Refractories can supply a full line of refractories including, but not limited to, lightweight castables, medium density castables, dense castables, gunning mixes, bricks, anchors, specialty shapes, and ceramic fiber. Quality product is the key to our success.
Carolina Refractories is headquartered in Conway, SC and is a mainsupplier of refractories across the United States and the globe. Weoffer a complete product portfolio to satisfy several industries andtheir extreme temperature requirements. Carolina Refractoriesmanufactures and supplies castables, gunning mixes, plastic, mortar,pre-cast shape, refractory bricks, and ceramic fiber to offer acomplete solution to any high temperature need. Currently we servethe steel, aluminum, cement, foundry, incineration, power and paperindustries. With over 35 years in the industry and a combinedexperience of 175 years our team can provide a maximum benefit to ourcustomers and their needs.
As a global leader in high quality refractories, SHINAGAWA has been supporting vital social infrastructure for 145 years by providing superior values and optimal solutions for virtually every essential industry. SHINAGAWA values a close relationship with our customers and promises the highest and most consistent performances. In doing so, SHINAGAWA responds to the needs of customers in essential industries with speed and competitiveness in both costs and performances.
Saint-Gobain offers a wide range of refractories products providing exceptional performances in a wide range of applications such as steel or glass making or mineral processing. Depending on the end-use, our products demonstrate exceptional resistance to abrasion, wear, corrosion and chemical attack. They display very high hot strength and dimensional stability as well as high hardness and fracture toughness.
Refractory products are a vital element in all high-temperature processes, such as metal making, the production of cement, petrochemical processes, glass and ceramics. Without refractories there would be no cars, no planes, no trains, no gas or electricity and we would be eating from wooden plates and living in mud-brick huts.
All Almatis alumina-based aggregates are manufactured from high purity raw materials. The well-controlled production processes result in very homogeneous, pure products for producing high quality refractories.
refractories WORLDFORUM is the most comprehensive technical and scientific journal for the entire refractories sector. Technology, development and application of high-temperature materials are the focus. refractories WORLDFORUM updates its readers on state-of-the-art processes and innovative technologies for the following sectors:
refractories WORLDFORUM addresses refractories professionals worldwide, i.e. in the production of refractories as well as in industries processing and consuming refractories, raw materials and additives, plant and machine suppliers. Each issue also features market analyses of selected countries, company profiles and interviews with manufacturers and suppliers, reports on new and upgraded plants as well as news items on companies, people, products, events.
Silica brick is one of the most important refractory materials having around 93% SiO2. Top refractory cement suppliers in India make use of high-quality rocks as a raw material to manufacture them. Silica bricks are well-known for having outstanding mechanical strength especially when the temperature nears their real fusing point. This unique behavior of silica refractories contrasts with different other refractories including alumino-silicate materials. Refractories apart from silica bricks start fusing and creeping at temperatures that are even lower than their fusion points. A wide range of silica bricks find applications in industries such as glass and steel.
The hydrated aluminum silicates that have around 25% -45% Al2O3 and 50% -80% SiO2 are known as fireclay refractories. These refractory materials have only minor additional minerals. Fireclay refractories are not only the most popular and inexpensive ones but also their raw ingredients are commonly available. These refractories find applications in regenerators, furnaces, kilns, stoves, and a large number of other purposes.
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