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ABRASION RESISTANCE
The ability of a metal to withstand surface wear
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AISI
American Iron and Steel Institute, a trade association of domestic steel mills
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ALLOYING ELEMENTS
These are the chemical elements, usually metallic, that are added to steel to modify its properties:
ABBREVIATIONS FOR ALLOYING ELEMENTS
| Aluminum |
Al |
| Calcium |
Ca |
| Carbon |
C |
| Chromium |
Cr |
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| Columbium |
Cb |
| Manganese |
Mn |
| Molybedneum |
Mo |
| Nickel |
Ni |
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| Nitrogen |
N |
| Phosphorus |
P |
| Selenium |
Se |
| Silicon |
Si |
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| Sulfur |
S |
| Titanium |
Ti |
| Tantalum |
Ta |
| Tungsten |
W |
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AMS
Aerospace Material Specifications
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ANNEALING
Annealing is a thermal treatment used to soften the steel, to improve machinability, to improve or restore ductility, and to reduce internal stresses. Annealing consists of heating the steel to a temperature above or within critical range, holding a sufficient length of time at the designated temperature and then cooling in the furnace at a slow rate
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ARGON OXYGEN DECARBURIZATION (AOD)
This term refers to both the process and the vessel that is used for the process in which hot metal from an electric furnace is refined to a chemical specification by blowing a mixture of gases (a combination of inert gas and oxygen) under the hot metal surface. The result removes carbon from the hot metal and produces steel by adding alloying elements (raw materials) in the form of ferroalloys to achieve a certain chemical specification
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ASM
American Society of Metals
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ASME
American Society of Mechanical Engineers
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ASTM
American Society of Testing and Materials
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ATMOSPHERIC CORROSION
Atmospheric corrosion occurs when unprotected steel is exposed to air containing moisture. The attack is generally uniform on plain surfaces, and may be affected by corners. The damage can usually be measured in terms of loss of thickness in thousandth of an inch (mils) per year
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AUSTENITIC
These grades of stainless have chromium (roughly 16% to 30%) and nickel (roughly 2% to 25%) as their major alloying additions. They have excellent ductility and formability, excellent corrosion resistance and good weldability. They have the ability to be hardened by cold drawing as a final step. These grades are usually non-magnetic
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BAR
Straight length in any cold-finished round, square, octagon, hexagon, or shape over 1/16" in diameter or size. Any cold-finished flat 3/8" and over in width and 1/8" and over in thickness. Any hot-rolled or forged round, square, octagon, hexagon or shape 1/4" and over in diameter or size. Any hot-rolled flat 1/4" to 10" inclusive in width and 1/4" and over in thickness
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BILLET
A semi-finished product, hot rolled from an ingot, generally square or round in cross section 2" and larger
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CENTERLESS GRINDING
Grinding the surface of a bar that is supported by rollers rather than on centers
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CHARPY IMPACT TEST
A test which a specimen is contains a V or key-hole-shaped notch, and supported at both ends as a simple beam, is broken by a falling pendulum. The energy absorbed in breaking the specimen is the measure of impact strength
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COBBLE
A piece of steel that becomes bent or twisted and must be withdrawn from the rolling operation and scrapped
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COLD FINISH
General term referring to any process where a mechanical process is used to achieve closer dimensional tolerances. Most common processes are drawing, smooth and rough turning, centerless grinding and peeling
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CONSUMABLE ELECTRODE VACUUM ARC REMELTING (VAC CE)
Remelting a stainless steel ingot in a vacuum by a process in which the ingot is the consumable electrode. This process not only removes gasses from the steel, but also minimizes impurities and segregation
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CONDITION B
Austenitic grades of stainless bar with higher yield and tensile strength achieved by cold working the material, usually by high reduction drawing
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CONDITION T
Martensitic grades of stainless bar with higher yield and tensile strength achieved by thermal treatment
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CONTINUOUS CASTING
A molding process developed as an alternative to the ingot casting method. In continuous casting, the mold is made of copper and is water-cooled to remove heat from the molten steel. As the metal passes through the water-cooled mold, it forms a solid shell on the outside while the inside is still full of liquid steel. This shell passes out the bottom of the copper mold and into a spray chamber where the water is directed against it, removing more and more of the heat from the steel and causing it to solidify from the edge toward the center until it is completely solidified.This solidified billet passes out upon a roller conveyor where it is cut to the lengths desired for hot rolling
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CREVICE CORROSION
Occurs when there is an agent on the metal that might be as simple as rubber band or a grease pencil that prevents oxygen from reaching the metal to re-form the passive film
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CORROSION RESISTANCE
The ability of a metal to withstand attack in an environment that is conductive to chemical or electrochemical reaction
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DENSITY
The weight of steel per volume of measurement
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DESCALE
This term refers to the process of removing scale from the surface of material by various chemical and/or mechanical means
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DRAWING
A process by which metal is pulled through a die for the purpose of changing the cross section or the mechanical properties
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DUCTILITY
The ability of a metal to deform without fracturing. Also, a measurement of the malleability of the metal in terms of the deformation it will withstand before failure
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DUPLEX
Steels exhibiting both austenitic and ferritic structures and characteristics
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ELECTRIC SLAG REMELT (ESR)
A remelt process that is used where extreme cleanliness is required. In that process, in ingot is as an electrode within the melt-specification. Electrical remelting is conducted in water-cooled, cooper crucible and the molten pool under the electrode contains a specially prepared slag
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ELECTRIC FURNACE
A method to produce steel..basically from scrap metal, with electric arc
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ELONGATION
A measure of ductility. In metals, elongation is expressed in terms of a percentage, reflecting the difference in length between an original length and the extension of that length that takes place in a tensile test. A metal sample is cut to a standard size and pulled until it breaks
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FERRITIC
The tendency of a metal to break when subjected to repeated cycles of stress considerably below its normal tensile strength
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FERRITIC
Stainless steel grades of steel contained in excess of about 11%chromium and used in a condition in which their microstructure consists of ferrite plus carbides. These steels are essentially non-hardenable by heat treatment and only slightly hardenable by cold work. They are magnetic in all conditions and have good scaling resistance. These steel are called ferritic because, in a heat treated condition ferrite is the predominant phase. When viewed under a microscope it looks like a low-carbon iron
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GALLING
Tearing of metal surfaces which render a component unserviceable
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GALVANIC CORROSION
This occurs when an electric current is generated between two dissimilar metals through an electrolyte and then promotes the corrosion of one of the metals while retarding or stopping the corrosion of the other
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FORGING QUALITY
Used where forging, quenching and tempering are required
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FREE MACHINING STEEL
Steel to which a small amount of some element, such as sulfur, selenium calcium is added to create a minute and widely distributed soft phase that aids machining. In cutting operations, the steel results in superior surface finish, longer tool life at increased cutting speeds
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GRAIN BOUNDARY CARBIDE
Metallic carbides that preferentially form on the surface of the individual grains, rather than within the body of the grains
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HARDENABILITY
The response of an alloy to a specified heating and quenching cycle -usually understood to be the maximum hardness that can be attained with the individual heat using the specified heat treatment, as used in connection with the martensitic (hardenable) stainless steels
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HARDNESS
Usually understood to be a resistance to indentation. Materials with little resistance are called soft; with hi resistance, called hard. Hardness is measured in steel by scientific instruments as follows:
- Brinell machine for sizes over 1/2 inch in diameter or thickness
- Rockwell machine sizes over 1/2 inch in diameter or thickness
We are interested in hardness because hardness correlates well with strength with harder materials being stronger.
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HEAT TREATING
To heat treat a product is to change its mechanical properties by thermal treatment. Normally this means to heat the material to an elevated temperature in the 1800 to 2000 grades Fahrenheit range, rapidly cool it, and then reheat it at a lower temperature to relieve the stresses caused by the rapid cooling
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HOT ROLLED
Hot rolled products are those that are rolled to finish at temperatures above the recrystalization temperature
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HYDROGEN EMBRITTLEMENT
- A condition caused by absorption of hydrogen, resulting in low difficulty in metals
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IMPACT STRENGTH
A measure of material's ability to resist fracture due to shock loading
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INCLUSIONS
Particles of non-metallic impurities, usually oxides, sulfates, or silicates that are mechanically held in steel during solidification
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INTERGRANULAR CORROSION
This occurs when the metal has been sensitized by passing through the temperature range of 800 to 1650 degrees Fahrenheit causing chromium carbides to form in the grain boundaries and thereby pulling corrosion resistant chromium out of the areas adjacent to the grain boundaries and making these areas susceptible to corrosive attack
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IRON
Element which is considered the base metal of stainless steel. The largest single constituent in ferrous metals
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MACHINING
The cutting away of the surface of a metal product by means of power driven machinery…i.e. drills, lathes, planers, shapers, etc.
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MAGNETIC PROPERTIES
Those properties relating to the response of the metal to an impressed magnetic field
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MARTENSITIC
These grades of stainless have chromium in the range of 11% to 17% as the sole major alloying addition. This is the same as the ferritic grades.However, carbon is added in amounts from .10% to 1.00% to radically change the behavior of the martensitic alloys. The high carbon enables the material to be hardened by heat treatment
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MECHANICAL PROPERTIES
Those properties that reveal the reaction, either elastic or plastic, of a metal to an applies stress. Tensile strength, and bendability are mechanical properties
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MICROSTRUCTURE
Refers to the shape and alignment of the microscopic components of the metal. Microstructure is key in determining hardness, toughness, and other variables. Austenitic, martensitic, and ferritic are types of microstructure
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OXIDE FILM THEORY
An explanation of passivity based upon the supposition that a thin relatively impermeable layer of oxide forms on the surface of stainless steel that retards further attack corrosives
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PASSIVATION
A process of chemically treating stainless with an acid followed by a water rinse, this process removes all external residue and scale that may affect the corrosion resistance character of stainless steel
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PHYSICAL PROPERTIES
The properties familiarity discussed in physics, exclusive of those listed under mechanical properties; for example, density, electrical conductivity, coefficient of thermal expansion, and magnetism
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PICKLING
Pickling is the process of using acid to remove the undesirable scale that can form on material during the annealing process. Most annealing is done in normal air environment. During the process, the material reaches a temperature that causes it to combine with oxygen in the air to form a layer of oxide or scale on the material's surface. To remove this scale, the material is passed through tubs containing acids and various types of scrubbers
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PITTING
A localized form of corrosion that occurs in stainless steel when the protective passive film is destroyed
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PLANISHING
Straightening of bars using highly polished rolls that improve the finish
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POLISHING
A belting operation using abrasives approximately 100 to 180 mesh to obtain a high luster finish
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PRECIPITATION HARDENING (PH)
Hardening that is caused by the precipitation of a metallic compound from a supersaturated solid solution at relatively low temperature that prevent scaling and distortion of the steel
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QQS
Prefix to material specifications. Used in government specifications
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QUENCHING AND TEMPERING
A process by which steel is rapidly cooled from above its upper critical temperature to a temperature far below this range. Water or oil is normally used to accelerate cooling. In the as-quenched condition, the product is not suitable for most commercial applications because of its lower ductility and higher hardness. The steel must, therefore, be tempered in order to soften it somewhat to improve its ductility and toughness. Tempering is a heat treatment done at lower temperatures usually in the range between 400 and 1200 degrees Fahrenheit
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REDUCTION OF AREA
Tensile specimens begin with a specific diameter at the center. Once the specimen is broken in the test, the round section becomes "necked in". The calculation for the reduction of area is as follows: Measure the diameter of the necked-in section, calculate the area of the necked-insection and the original cross-sectional area and calculate the percentage difference. This difference is expressed as percent reduction of area
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RETAINED AUSTENITE
A tendency in martenistic alloys that increases with alloy and carbon content and with rate of cooling, to retain at room temperature a fraction of the austenite phase that is stable at the high temperature and which fails to decompose into martensite on cooling
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RMS
Measures the "smoothness" of a product. Standing for "root mean square", the RMS number represents the depth of grooves in the surface of a metal. The lower the number, the smoother the material
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SAE
Society of Automotive Engineers
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SENSITIZATION
A term used to describe the condition of the austenitic stainless steels resulting from the heating them in the temperature range of approximately 800 to 1650 degrees Fahrenheit and cooling to room temperature. When the metal is held in the sensitization range, the carbon in the steel combines with some of the chromium and precipitates as chromium carbide at the grain boundaries. This depletes the area at the grain boundaries of chromium and makes the metal susceptible in those areas to attack in some corrosive media
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SOLUTION ANNEALING
Solution annealing is a process performed on austenitic steels. The process consists of heating or rolling the material up to a temperature above 1950 degrees Fahrenheit and holding it long enough for the carbon to go into solution. After this, the material is quickly cooled to prevent the carbon from coming out of the solution. Solution annealed material is in its most corrosion resistant and ductile (formable) condition
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STRESS CORROSION CRACKING
Catastrophic failure by generally transgranular cracking occurring in stainless steels and other metals. It is caused by combined action of a corrosive environment and stress, often without outward appearance of general corrosion attack
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SULFIDE STRESS CRACKING
A severe potentially catastrophic failing that appears as branching transgranular cracks in austenitic stainless. Caused by a combination of tensile stress, corrosive media, temperature, and lack of oxygen. Preventative measures include increasing or decreasing the nickel content, removing stresses, and using duplex stainless steels
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TENSILE STRENGTH
A short form for "ultimate tensile stress". The maximum tensile stress which a material is capable of sustaining. Tensile strength is calculated from maximum load during the tension test carried to rupture the original cross section area of specimen
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TEST REPORTS
A test report or certification is nothing more than a document which lists the results of tests done on the material. These tests are normally the ladle chemistry, the mechanical properties and corrosion test results
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THERMAL CONDUCTIVITY
A measurement expressing the ability of a metal to conduct heat
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THERMAL EXPANSION
The change in volume produced in a metal by change in temperature, commonly expressed as a coefficient measuring the linear change per degree change in temperature
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TOLERANCE
Specified limits of deviation from a measurement that can be dimensions, strength, etc.
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TOUGHNESS
Toughness may be defined as the ability of a material to accept applied stresses by either elastic or plastic deformation, depending on the stress level, without sudden brittle failure
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TRANSVERSE PROPERTIES
This item refers to mechanical properties measured perpendicular to the direction of rolling
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TURBINE STEEL
A term commonly applied to Type 403 stainless steel because of its historic and contemporary prominence as a blading and structural material in steam turbines
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UNS
Defines the chemical analysis (Unified Numbering System) as a joint responsibility of the SAE and ASTM
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VACUUM INDUCTION MELTED (VIM)
Initial heat is melted in a vacuum, drawing off gasses and other impurities. This provides cleaner and therefor stronger metal
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WELDING
The joining of two pieces of metal into one solid piece
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