CARBON and STEELS

CARBON and STEELS

Post 365 ⇒   by Gautam Shah 

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Iron as a metal is very ancient material. It was difficult to process (smelt), unlike materials with lower melting temperatures, such as copper and its alloys. Iron is rarely obtainable in pure form. The impurities in iron derive from the ore, and carbon through the smelting process. Carbon is one of the most important of impurities, varying between 0.002% and 2.1%. Presence of Carbon makes the Iron up to 1000 times a harder material. Technically more than 90 per cent of all steels are carbon steels. Presence of small amounts of carbon changes the quality of steel. It affects strength, hardness, mechanical properties (machining, forming, etc.). With very high percentage of carbon workability and impact strength are reduced, whereas with lower carbon content hardness and tensile strength are higher.

Iron of meteorite -similar to Earth’s inner core

Iron ore pellets

Crude iron or Pig iron metal is produced in a furnace, by mixing ore with coke. The high carbon content of crude iron can be further reduced by refining it with air or oxygen, to turn it into steel. A carbon content metal is commonly called Cast Iron. The carbon content of cast iron is 2.1 percent or more. Gray cast iron is relatively soft. It can be easily machined and welded. It is used for engine cylinder blocks, pipe, and machine tool structures. White cast iron is hard, brittle, but not weldable. When annealed, it becomes malleable cast iron. Malleable cast iron can be welded and machined. It is ductile material. Ductile cast iron is sometimes called nodular or graphite cast iron. It is ductile malleable and weldable.

Iron Ore

Pig Iron billets

Besides carbon other elements present are, manganese, silicon, copper, nickel, chromium, molybdenum, vanadium, tungsten, tin, niobium, zirconium, and non metals like sulphur, phosphorus. These materials mostly find their way through the scrape that is partly used for steel making or through an intentional quality markup. The additions of these materials take steel to the category of Alloy steel. Such alloying elements are added to gain properties like better strength, hardness, durability, or corrosion resistance. These are often called specialty steels.

Crankshaft casting

Adjusting the carbon content is most common tool to control quality of steel. Other quality determinant is the rate at which the steel is cooled. Steel properties are also modified by heat treatments, mechanical working it at hot or cold temperatures and by adding other alloying elements besides carbon.

Steel with high carbon content is hard and strong, but not ductile enough for common uses. In carbon steels, the higher carbon content lowers the melting point and reduces weldability.

Mild steel bars

Low carbon steel has approximately 0.05% to 0.25% carbon content with other materials like manganese. Mild steel, is also known as plain-carbon steel or low-carbon steel. Its very common form of steel, and its material properties are adequate for many applications. It is ductile and malleable. It has a relatively low tensile strength, but is cheap and amenable to cold forming processes. Its surface hardness can be increased with carburizing. It is used for structural steel.

Steel forging

Medium carbon steel has approximately 0.29% to 0.54% carbon content (with 0.60 to 1.65% manganese content). It shows good wear resistance and used for large parts, forging and car parts.

High carbon steel has approximately 0.55% to 0.95% carbon content (with 0.30 to 0.90% manganese content). It is very strong material and used for springs and high-strength wires.

High end Steel – chef’s knife

Ultra high carbon steel has approximately 2.5–3.0% carbon content. These steels that can be tempered to great hardness and used cutting tools, knives, axles or punches. Steel with a carbon content above 2.14% is considered cast iron.

Clydach Gorge Iron Bridge Cast iron supports

Hardened steel usually refers quenched or quenched and tempered steel. Silver steel or high-carbon bright steel, gets its name from its appearance, due to the high carbon content. Silver steel is used for cutting edges and axle components.

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WROUGHT IRON LATTICES

Post 226 ⇒   by Gautam Shah 

WROUGHT IRON LATTICES

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Wrought Iron lattices have been used primarily over windows, doors and other gaps. Latticed structures of wrought iron are used for balconies, as space dividers, church screens, vine climbers, stair railings, estate gates and barricades, frames for furniture items, lintels, beams, brackets, columns and for garden structures like orangeries and pavilions.

Iron forming reflects man’s innovative and craft skills. It has been a very difficult material to work with, as it presents different behaviour in its various forms. Yet, it has been cast, resealed, joined, spliced, chased and engraved. It has been reformatted with hot and cold treatments. Wrought iron has been used for household utilities, tools, vessels, arms, building elements, architectonic entities, decorative items and statuettes. It has replaced wood for its stability, strength and malleability.

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Before the Middle Ages, wrought iron was used primarily for weapons, tools and utilities that only could be made with a metal. Unlike Cast iron, Wrought iron has a lower carbon content. It is stronger, non-brittle, and could be forged to any shape, and join by beating. Literally, Wrought iron means an iron that can be worked, both in hot and cold forms.

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One of the most creative forms of wrought iron manifests in trellis, grills, and other hollowed or pierced-out planner forms. Earlier trellis or grills were formed of wood, bamboos, vines, and cast of copper or bronze, or even of ceramics. These materials were not amenable to plastic shaping. Wrought iron has been used as a plastic material to form variety of trellis, in simple or multi-curved planner forms and also mould sub-elements differently.

The first lattices were functional elements like the protective cover within gaps, and in doors and windows. Simple linear cast or forged elements were inserted in side structures of masonry or wood. These, however, soon became interlacing or entwined entities of bars, hot-forged or riveted forming a grill. Same techniques were used for creating grills for hearths and sieves.

Wrought Iron lattices began to be used 13 and 14th C windows of mansions and cathedrals requiring high security. Same structures were used as barricades and partitions. The lattices were designed with variegated shaping of bars’ profiles, and in terms of angle and spacing. Hot-forging and cold working methods were used to alter the sections and shapes of the linear elements. Round and square rods and bars were twisted, coiled and beaten into complex foliated forms. Iron pieces were chiselled, chased, riveted, shape forged. Iron plates were also used for plate like tracery elements. Ends, finials and cresting were cast from other materials like brass or bronze and mounted over steel roods. Riveting and hot forging was chief techniques of joint making. Joints, However, were so skilfully concealed that the grill seemed like one cast or formed piece.

Wrought ironwork began to serve other decorative purposes. Famous cathedrals and other public buildings ( Canterbury and Winchester Cathedrals of England and Notre Dame de Paris) have extremely crafty pieces wrought iron works.

Wrought Iron lattice work, began as a rough surface entity, but by end of middle ages, the surfaces were well formed, ground and joints were concealed. Surfaces were often chased, engraved, inlayed with materials. Finials, caps and other elements of brass, copper, bronze and gold were added. Ornaments were forged out as separate parts, and assembled with riveting, or welding. Decorative elements, such as of flowers, leaves, vines, birds, names, and coats of arms, were bunched or heaped to provide a composition language.

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GRILLS and TRELLIS

Post by –Gautam Shah

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Grills and Trellis are used primarily for barricading, for providing a transparent vista and for ornamentation. Grills are placed in apertures, windows, doors and any other cleavages in the barrier systems. Grills are also placed against solid planes like walls for ornamentation. Grills are used as parapets on terraces, in balconies, galleries or at the edge of any elevated level. Grills are placed on level grounds to differentiate areas of landscapes and gardens, on walkways, roadsides, road lanes, etc.

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Grills also incorporate railings and grab bars on walkways, stairs, ramps, passages, buses, railway coaches. Grills are placed as markers to differentiate acutely varied areas: between banks and water bodies such as rivers, canals, pools, puddles, between spectators’ and the spectacle, between slow and fast moving objects, against hazardous utilities like machines, ovens etc. Grills are used in nursery and infirm areas, where grabbing elements are required at many different heights.

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Grills become gates, windows and doors. Grills also become ladders. Grills in vertical, inclined and horizontal positions are used as plant climber support, tree guards and to support pots and vases. Grills are used to hang clothes and to dry clothes.

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Grills are used as spark arresters in fireplaces and against burners. Grills are used to support burning bodies in crematoriums. Grills are used to evenly distribute heat as in grilles and barbecue devices. Grills act as air distributors in A.C. rooms.

3479609858_db627dc1b5_zGrills by their typical configuration help in controlling, filtering, decelerating, directing, channeling things that pass through it.

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