Classification of Metal and Alloys
Ferrous – Iron as base metal
Nonferrous – No iron in compositionAlloy definitions -
Steel : Historic Overview
round 800 B.C. -: the general use of iron
16th-19th century -: wrought iron / cast iron
round 1870 A.D. -: the first production of modern steel
late 19th century -: multi-storey iron structure buildings
early 20th century -: the use of tower and mobile cranes in construction
Ferrous Metals -: Cast irons, Steels.
Super alloys -: Iron-based, Nickel-based, Cobalt-based.
Non-ferrous metals -: Aluminum and its alloys Copper and its alloys, Magnesium and its alloys, Nickel and its alloys, Titanium and its alloys, Zinc and its alloys, Lead & Tin, Refractory metals, Precious metals.
Alloys In Metals
Properties of metal & alloy
Strength, Toughness, Hardness, Ductility, Elasticity, Fatigue and Creep
Density, Specific heat, Melting and boiling point, Thermal expansion and conductivity, Electrical and magnetic properties
Oxidation, Corrosion, Flammability, Toxicity, …
Mechanical Properties Of Metals
The ability of a material to stand up to forces being applied without it bending, breaking, shattering or deforming in any way..Elasticity
The ability of a material to absorb force and flex in different directions, returning to its original position.
The ability of a material to be change in shape permanently.Ductility
The ability of a material to change shape (deform) usually by stretching along its length..
The ability of a material to stretch without breaking or snapping.Malleability
The ability of a material to be reshaped in all directions without cracking.Toughness
A characteristic of a material that does not break or shatter when receiving a blow or under a sudden shock.
The ability of a material to conduct electricity..Hardness
The ability of a material to resist scratching, wear and tear & indentation.Fatigue
Fatigue failures occur when metal is subjected to a repetitive or fluctuating stress and will fail at a stress much lower than its tensile strength.
Fusibility is defined as the ability of a metal to become liquid by the application of heat. Metals are fused in welding. Steels fuse at approximately 2,500°F, and aluminum alloys at approximately 1,110°F.Creep
The mechanical strength of metals decreases with increasing temperature and the properties become much more time dependent. Metals subjected to a constant load at elevated temperatures will undergo 'creep', a time dependent increase in length.
Creep in metals is defined as time dependent plastic deformation at constant stress (or load) and temperature.
Hardness is the property of a material to resist permanent indenation. Because there are several methods of measuring hardness, the hardness of a material is always specified in terms of the particular test that was used to measure this property. Rockwell, Yickers, or Brinell are some of the methods of testing. Of these tests, Rockwell is the one most frequently used.
When a material has a load applied to it, the load causes the material to deform. Elasticity is the ability of a material to return to its original shape after the load is removed. Theoretically, the elastic limit of a material is the limit to which a material can be loaded and still recover its original shape after the load is removed.
Ductility and Malleability
Ductility is the property that enables a material to stretch, bend or twist without cracking or breaking. This property makes it possible for a material to be drawn out into a thin wire. In comparison, malleability is the property that enables a material to deform by compressive forces without developing defects. A malleable material is one that can be stamped, hammered, forged, pressed, or rolled into thin sheets.
Pure iron rarely exists outside of the laboratory. Iron is produced by reducing iron ore to pig iron through the use of a blast furnace. From pig iron many other types of iron and steel are produced by the addition or deletion of carbon and alloys.
Pig iron is composed of about 93% iron, from 3% to 5% carbon, and various amounts of other elements. Pig iron is comparatively weak and brittle; therefore, it has a limited use and approximately 90% produced is refined to produce steel. Cast-iron pipe and some fittings and valves are manufactured from pig iron.
Ingot iron is a commercially pure iron (99.85% iron) that is easily formed and possesses good ductility and corrosion resistance. The chemical analysis 'and properties of this iron and the lowest carbon steel are practically the same. The lowest carbon steel, known as dead-soft, has about 0.06% more carbon than ingot iron. In iron the carbon content is considered an impurity and in steel it is considered an alloying element. The primary use for ingot iron is for galvanized and enameled sheet.
Steel in this classification is tough and ductile, easily machined, formed, and welded. It does not respond to any form of heat treating, except case hardening.
These steels are strong and hard but cannot be welded or worked as easily as the low-carbon steels. They are used for crane hooks, axles, shafts, setscrews, and so on.
Steel in these classes respond well to heat treatment and can be welded. When welding, special electrodes must be used along with preheating and stress-relieving procedures to prevent cracks in the weld areas. These steels are used for dies, cutting tools, mill tools, railroad car wheels, chisels, knives, and so on.
- Austenitic steels
- Ferritic steels
- Martensitic steels
- Precipitation-hardening (PH) steels
- Duplex-structure steels
Steels that derive their properties primarily from the presence of some alloying element other than carbon are called ALLOY STEELS.
One or more of these elements may be added to the steel during the manufacturing process to produce the desired characteristics. Alloy steels may be produced in structural sections, sheets, plates, and bars for use in the "as-rolled" condition.
- Nickel Steel
- Chromium Steel
- Chrome Vanadium Steel
- Tungsten Steel
- Manganese Steel
These steels contain from 3.5% nickel to 5% nickel. The nickel increases the strength and toughness of these steels. Nickel steel' containing more than 5% nickel has an increased resistance to corrosion and scale. Nickel steel is used in the manufacture of aircraft parts, such as propellers and airframe support members.
These steels have chromium added to improve hardening ability, wear resistance, and strength. These steels contain between 0.20% to 0.75% chromium and 0.45% carbon or more. Some of these steels are so highly resistant to wear that they are used for the races and balls in antifriction bearings. Chromium steels are highly resistant to corrosion and to scale.
Chrome Vanadium Steel
This steel has the maximum amount of strength with the least amount of weight. Steels of this type contain from 0.15% to 0.25% . vanadium, 0.6% to 1.5% chromium, and 0.1 % to 0.6% carbon. Common uses are for crankshafts, gears, axles, and other items that require high strength. This steel is also used in the manufacture of high-quality hand tools, such as wrenches and sockets.
This is a special alloy that has the property of red hardness. This is the ability to continue to cut after it becomes red-hot.
Because this alloy is expensive to produce, its use is largely restricted to the manufacture of drills, lathe tools, milling cutters, and similar cutting tools.
The amount of manganese used depends upon the properties desired in the finished product. Small amounts of manganese produce strong, free-machining steels. Larger amounts (between 2% and 10%) produce somewhat brittle steel, while still larger amounts (11% to 14%) produce a steel that is tough and very resistant to wear after proper heat treatment. Railroad tracks, for example, are made with steel that contains manganese
Iron And Steel Manufacturing Process
Manufacture Of Steel : Bessemer Process
The Bessemer process was the first inexpensive industrial process for the mass- production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. The key principle is removal of impurities from the iron by oxidation with air being blown through the molten iron. The oxidation also raises the temperature of the iron mass and keeps it molten.
Manufacture Of Steel Open Hearth Process
Manufacture Of Steel L D Process (Basic Oxygen Process)
In the basic oxygen process, steel is also refined in a pear-shaped furnace that tilts sideways for charging and pouring. Air, however, has been replaced by a high-pressure stream of nearly pure oxygen. After the furnace has been charged and turned upright, an oxygen lance is lowered into it. The water-cooled tip of the lance is usually about 2 m (about 6 ft) above the charge although this distance can be varied according to requirements. Thousands of cubic meters of oxygen are blown into the furnace at supersonic speed. The oxygen combines with carbon and other unwanted elements and starts a high-temperature churning reaction that rapidly burns out impurities from the pig iron and converts it into steel.
Production Of Steel
Production Of TMT Bars
Tempcore: TMT BARS are removed from cooling zone. A temprature gradient is established in the cross section. It causes heat to flow from centre to surface. The martensite left at centre is tempered by heat flow. So it is known as tempcore. After the intensive cooling, the tmt bar is exposed to air and the core reheats the quenched surface layer by conduction, therefore tempering the external martensite. helps them attain a higher yield strength.
Basic Types of Tool and Die Steels
Steel Numbering Systems
IS CODE :
1) Metals Processing Advisor, "Iron and Steel Overview: An in depth look at the Iron and Steel Industries and associated process equipment."
2) World-Bank. "Industrial Pollution Prevention and Abatement: Coke Manufacturing." Washington, D.C. July 1998.
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