|
Metal
Products Distributor Supplier
Metals and Materials Table of Contents GE HARDENING—Precipitation hardening; a process of
aging that increases hardness and strength and ordinarily decreases
ductility. Age hardening usually follows rapid cooling from solution
heat treatment temperatures or cold working.
AGING—A change in properties of an aluminum alloy that generally
occurs slowly at atmospheric temperatures and more rapidly at higher
temperatures. ALLOY—The mixture of any element with a pure metal. However, there
are several elements regularly occurring in plain carbon steel as
manufactured, such as carbon, manganese, silicon, phosphorous, sulfur,
oxygen, nitrogen and hydrogen. Plain carbon steel is therefore an alloy
of iron and carbon and these other elements are incidental to its
manufacture. Steel does not become alloy steel until these elements are
increased beyond their regular composition for a specific purpose, or
until other metals are added in significant amounts for a specific
purpose.
ALLOY STEEL—Steel is considered to be alloy steel when the maximum of
the range given for the content of alloying elements exceeds one or more
of the following limits: Manganese 1.650/0, silicon,.60%, copper,.600/0,
or in which a definite range or a definite minimum quantity of any of
the following elements is specified or required within the limits of the
recognized field of constructional alloy. Steels: Aluminum, chromium up
to 3.9~, cobalt, columbium, molybdenum, nickel, titanium, tungsten,
vanadium, zirconium, or any other alloying element added to obtain a
desired alloying effect.
ANNEALING—See heat treating definitions . BASIC OXYGEN FURNACE—The process of manufacturing steel in this type
of furnace is called the basic oxygen process and is the most efficient
method of producing low and medium carbon and low and medium alloy
steels. In this process high purity oxygen is blown onto the surface of
a bath of molten iron contained in a basic lined and ladle shaped
vessel. The melting cycle duration is extremely short with quality
comparable to open hearth steel. BASIC PROCESS—A steel making process either basic oxygen, open hearth
or electric in which the furnace is lined with a basic refractory. A
slag, rich in lime, being formed and phosphorous removed. BILLET—A solid semi-finished round or square product that has been
hot worked by forging, rolling or extrusion. An iron or steel billet has
a minimum width or thickness of 11~! inches and the cross-sectional area
varies from 21/4 to 36 square inches. BLAST FURNACE—A vertical shaft type furnace used for reducing iron
ore to pig iron when cast or hot metal for further melting. This product
is used in an open hearth or basic oxygen furnaces for production of
steel. BLOOM—Generally a rolled product from an ingot generally greater than
36 square inches in area. This is generally considered the first
operation in the production of bars or structurals. CARBON STEEL—Steel is classified as carbon steel when no minimum
content is specified or required for aluminum, boron, chromium, cobalt,
columbium, molybdenum, nickel, titanium, tungsten, vanadium, or
zirconium, or any other element added to obtain a desired alloy effect;
when the specified minimum for copper does not exceed .40% or when the
maximum content specified for manganese does not exceed 1.650/0; silicon
.600/0; copper .60%. CARBURIZING—See heat treating definitions CHARPY TEST—A pendulum-type single-blow impact test in which the
specimen, usually notched, is supported at both ends as a simple beam
and broken by a falling pendulum of given weight. The energy absorbed,
as determined by the subsequent rise of the pendulum, is a measure of
impact strength or notch toughness and is a measurement in foot-pounds.
The test specimen is 2” or 2.165” long, .394” square and has a key hole
type notch in the center made by centering a No. 47 drill .160” from one
side and sawing through the hole. COLD DRAWING—This is a process for finishing a hot rolled rod or bar
at room temperature by pulling it through the hole of a die of the same
shape but smaller in size. The bars or rods are cleaned of scale by
pickling or other methods prior to cold drawing and then coated with
lime which aids as a lubricant in the drawing operation. COLD FINISHING—The cold finishing of steel, generally used for bars
and shafting, may be defined as the process of reducing their cross
sectional area, without heating, by one of five methods: 1. Cold rolling 3. Cold drawing and grinding 5. Turning and grinding
2. Cold drawing 4. Turning and polishing COLD ROLLING—The cold working of hot rolled material by passing it
between power driven rolls. The process is generally used for flat bars
of such a size that they cannot be pulled through a die and for the
production of cold rolled sheets by cold reducing hot rolled and pickled
sheets. Whereas wire and sheets are cold drawn and cold rolled
continuously from coil, bars are individually cold drawn. COLD WORKING—Plastic deformation of a metal at a temperature low
enough to insure strain hardening. CORE—The center portion of a piece of steel which may be of different
chemical composition than the outside, as in the case of carburized
parts or which may have different mechanical properties than the outside
due to the failure of penetration of heat treatment effect. DECARBURIZATION—The loss of carbon from the surface of a ferrous
alloy. Decarburization is a common surface condition of hot rolled steel
and is produced during the heating and rolling operations when
atmospheric oxygen reacts with the heated surface removing carbon. ELASTIC LIMIT—The greatest stress which a material is capable of
developing without a permanent deformation remaining upon complete
release of the stress. ELECTRIC FURNACE STEEL—Steel made in any furnace where heat is
generated almost always by are. Because of relatively high cost,
normally only tool steels and other high value steels are made by the
electric furnace process. ELONGATION—The amount of permanent extension in the vicinity of the
fracture in the tensile or tension test; usually expressed as a
percentage of the original gauge length, such as 25% in 2” or 21% in 8”.
ENDURANCE LIMIT—Also known as fatigue limits a limiting stress, below
which metal will withstand without fracture an indefinitely large number
of cycles of stress. If the term is used without qualification, the
cycles of stress are usually such as to produce complete reversal of
flexural stress. Above this limit failure occurs by the generation and
growth of cracks until fracture results in the remaining section. FATIGUE—The phenomenon of the progressive fracture of a metal by
means of a crack which spreads under repeated cycles of stress. FERROUS—Metals or alloys that contain appreciable amounts of iron.
FILE HARDNESS—Hardness as determined by the use of a file of
standardized hardness on the assumption that a material which cannot be
cut with the file is as hard as, or harder than, the file. Files
covering a range of hardnesses may be employed. FRACTU RE TESTING—Breaking a specimen and examining the fractured
surface with the unaided eye or with a low-power microscope to determine
such things as composition, grain size, case depth, soundness, or
presence of defects. HARDEN-ABILITY—This relates to the ability of steel to harden deeply
upon quenching and takes into consideration the size of the part, the
method of quenching and the analysis and grain size of the steel. Carbon
steels are considered as shallow hardening and various alloy and tool
steel grades are considered deep hardening or through hardening. HARDENING—Increasing the hardness by suitable heat treatment, usually
involving heating and cooling. When applicable, the following more
specific terms should be used: age hardening, case hardening, flame hardening, induction
hardening, precipitation hardening, and quench hardening. HARDNESS—The ability of a metal to resist penetration. The principal
methods of hardness determination are the Brinell, Rockwell and
Scleroscope tests.
HEAT TREATMENT—An operation or combination of operations involving
the heating and cooling of a metal in the solid state for the purpose of
obtaining certain desirable conditions or properties. Heat treating
operations would be annealing, normalizing, quenching and tempering,
etc. IMPACT TEST—A test used to determine the impact energy measured in
foot pounds, to fracture a material by means of an Izod or Charpy test.
INCLUSIONS—Nonmetallic materials occurring in metals. More
specifically in steel; oxides, sulphides, and silicates which are
mechanically held during solidification of the ingot. INGOT- A steel casting that is cast into a mold which when solidified
will be rolled in a blooming mill to plates, slabs for sheets, or blooms
and billets into structurals and bars. IZOD TEST—An impact test similar to the charpy with the difference
being in the test specimen. In the Izod test the specimen is 2.953”
long,.3937” square with a 45” notch located 1.1024” from the impact end.
The distance from the bottom of the notch to the opposite side is .315”.
JOMINY TEST—This is a test used to determine the hardenability of any
grade of steel. It consists of water quenching, under closely controlled
conditions, one end of a one inch diameter specimen of the steel under
test and measuring the degree of hardness at regular distances from the
quenched end along the side. The hardnesses obtained at regular
intervals along the bar are then either tabulated or plotted on graphs.
KILLED STEEL—Steel deoxidized with a strong deoxidizing agent such as
silicon or aluminum in order to reduce the oxygen content to such a
level that no reaction occurs between carbon and oxygen during
solidification of the molten steel in the ingot. Killed steel products
will produce a more chemically uniform analysis from the bottom to the
top of the ingot. Killed steel is considered having less chemical
segregation than semi-killed or rimmed steel.
MACHINABILITY—The relative ease of machining a metal. Machinability
index for various steels and machinability tables are available for
comparing machining rates with 1212 steel as the standard for carbon and
alloy steels and W-l as a standard for tool steels.
MARTENSITE—A microconstituent or structure in quenched steel which
has the maximum hardness of any of the structures resulting from the
decomposition or transformation of austenite. Steel which is to be
quenched and tempered properly must first be fully hardened in the
martinsitic state and then drawn or tempered back.
MECHANICAL PROPERTIES—The properties of a material that reveal its
elastic and inelastic behavior where force is applied, thereby
indicating its suitability for mechanical applications; for example,
modulus of elasticity, tensile strength, elongation, hardness and
fatigue limit. MILL EDGE—The edge of strip, sheet or plate in the as rolled state.
Unsheared. MODULUS OF ELASTICITY—The ratio within the limit of elasticity of the
stress to corresponding strain. The stress in pounds per square inch is
divided by the elongation in fractions of an inch for each inch of the
original gauge length of the specimen. The modulus of elasticity for
cold rolled steel is 29,500,000 psi and for other steels varies between
28,600,000 and 30,300,000 psi.
NITRIDING—Adding nitrogen to iron-base alloys by heating the metal in
contact with ammonia gas, or other suitable nitrogenous material.
Nitriding is conducted at a temperature usually in the range of
935-1000” F. and produces surface hardening of the metal without
quenching. NON-FERROUS—Metals or alloys that contain no appreciable quantity of
iron. This term is applied to such metals as aluminum, copper,
magnesium, etc. NORMALIZING—See heat treating definitions page 146 through 148. OLSEN DUCTILITY TEST—A cupping test in which a piece of sheet metal,
restrained except for the center, is deformed by a standard steel ball
until fracture occurs. The height of the cup in thousandths of an inch
at time of failure is a measure of the ductility. OPEN HEARTH PROCESS . One of the main methods used in the production
of steel from hot metal (iron) produced in the blast furnace. The
furnace can be charged with hot metal, and cold steel scrap for further
refining into a carbon or alloy steel. Generally open hearth furnaces
range from 75 to 450 tons of melting capacity in one heat.
OXIDATION—The addition of oxygen to a compound. Exposure to
atmosphere sometimes results in oxidation of the exposed surface, hence
a staining or discoloration. This effect is increased with temperature
increase to the point where heavy scale is formed and the steel product
has a decarburized surface. PHYSICAL PROPERTIES—Those properties familiarly discussed in physics,
exclusive of those described under mechanical properties; for example:
density, electrical conductivity and coefficient of thermal expansion.
PICKLING—The process of removing hot rolled mill scale from billets,
bars or hot rolled sheets with sulphuric or hydrochloric acid. The scale
is removed for hot rolled pickled and oiled sheets or for further
processing of the hot rolled steel product into cold drawn bars and wire
and cold rolled sheets and strip. PLASTIC DEFORMATION—Deformation of a material that will remain
permanent after removal of the load which caused it. PRECIPITATION HARDENING—A process of hardening an alloy in which a
constituent precipitates from a supersaturated solid solution. This
process is used for non-ferrous alloys to change the mechanical
properties of the metal and is also called aging or age hardening. PROPORTIONAL LIMIT—Same as elastic limit. QUENCHING—In the heat treating of steel, the step of cooling metals
rapidly in order to obtain martensite by immersing or quickly cooling
the steel in a quenching medium. The quenching media may be water,
brine, oil, special solutions, salts or metals; and the intensity of the
quench is determined by the temperature, volume and velocity of the
media. In the case of air hardening tool steels the quenching medium is
air at room temperatures. REDUCTION OF AREA—The percentage difference between the original
cross sectional area and that of the smallest area at the point of
rupture. The percentage figure can be considered a measurement of
ductility. RESIDUAL STRESS—Macroscopic stresses that are set up within a metal
as the result of nonuniform plastic deformation or thermal gradients.
Stresses of this nature are caused by cold working or by drastic
gradients of temperature from quenching or welding. RESIDUALS—Elements present in an alloy in small quantities, but not
added intentionally. RESILIENCE—The tendency of a material to return to its original shape
after the removal of a stress that has produced elastic strain. RIMMED STEEL—Low-carbon steel in which incomplete deoxidation permits
the metal to remain liquid at the top of the ingot, resulting in the
formation of a bottom and side rim of relatively pure iron of
considerable thickness. Steel products such as sheets produced from this
type of ingot will have a very good surface quality free of surface
defects. ROCKWELL HARDNESS (TEST) -- See hardness tests. ROLLED EDGES—Finished edges, the final contours of which are produced
by side or edging rolls. The edge contours meet commonly used are square
corners, rounded corners and a rounded edge. ROLLINQ—A term applied to the operation of shaping and reducing metal
in thickness by pressing it between rolls which compress, shape and
lengthen it following the roll pattern. Steel is either hot rolled or
cold rolled depending upon the product being manufactured, ROLLING DIRECTION—The direction in which the steel product is rolled
perpendicular to the axes of the rolls during rolling. ROLLING MILLS—Equipment used for rolling down metal to a smaller size
or to a given shape employing sets of rolls the contours of which
determine or fashion the product into numerous intermediate and final
shapes, e.g., blooms, slabs, rails, bars, rods, sections, plates, sheets
and strip. RUST—A corrosion product consisting of hydrated oxides of iron. This
term is only applied to ferrous alloys. SCALE—A complex iron oxide formed on the steel surface during the hot
rolling operation or formed on steel parts which are heat treated in the
presence of oxygen. SCLEROSCOPE—See hardness tests. SCRAP—Material unsuitable for direct use but usable for reprocessing
by remelting. SEGREGATION—Pertaining to chemical segregation which occurs during
the solidification of the molten steel in the ingot mold. Rimmed and
capped steels are considered to have high levels of segregation;
semi-killed steels intermediate segregation; and, killed steels the
minimum amount. SEMIKILLED STEEL—A commonly used grade of steel manufactured for low
carbon bars and structurals. A steel is considered semi killed when it
is produced so that it is incompletely deoxidized and it contains
sufficient dissolved oxygen to react with the carbon to form carbon
monoxide to offset solidification shrinkage in the ingot. SHEET STEEL—Either hot or cold rolled sheets produced on continuous
sheet mill where the minimum width produced is 24”. Sheet coils when
slit to narrower widths is called slit sheet. SHOT BLASTING—Cleaning surface of metal by air blast, using metal
shot as an abrasive. SLAB—A semi finished steel product intermediate between ingot and
plate, with the width at least twice the thickness for rolling down into
plates or sheets. SOLID SOLUTION—Many metals possess the ability to dissolve certain
other elements in the solid state forming solid solutions which in many
ways are analogous to ordinary liquid solutions. In the case of steel
the solid solution is called austinite. SOLUTION HEAT TREATMENT—Heating
an alloy to a suitable temperature, holding at the temperature long
enough to allow one or more constituents to enter into solid solution
and then cooling rapidly enough to hold the constituents in solution.
The alloy is left in a supersaturated, unstable state and may
subsequently exhibit quench aging. SPARK TESTING—This is an inspection method for quickly determining
the approximate analyst of steel. It is intended primarily for the
separation of mixed steel and when properly conducted, is a fast,
accurate and economical method of separation. It consists in holding the
sample against a high speed grinding wheel and noting the character and
color of the spark which is compared with samples of known analysis.
STAINLESS STEEL—Corrosion resistant steel of a wide variety, but
always containing a high percentage of chromium. The minimum chromium
content is considered at 11% for stainless steel, although lesser
amounts of chromium are found in stainless products such as those used
for automobile mufflers. Stainless steels have the properties of being
highly resistant to corrosion attack by organic acids, weak mineral
acids, atmospheric corrosion, etc. Some standard grades of stainless
steel also have 3.5 to 22% of nickel which further increases resistance
to chemical and atmospheric corrosion.
STEEL—An iron-base alloy, malleable in same temperature range as
initially cast, and containing carbon in amounts greater than .05% and
less than about 2.00%. Other alloying elements may be present in
significant quantities, but all steels contain at least small amounts of
manganese and silicon. STRAIN—Deformation produced on a body by an outside force. STRIP STEEL -- (Cold Rolled) A flat cold rolled steel product rolled
to widths 2316/16” and narrower, under .250” in thickness, which has
been cold reduced to desired decimal thickness and temper on single
stand, single stand reversing, or tandem cold mills in coil form from
coiled hot rolled pickled strip steel. TANDEM MILL—Arrangement of rolling mills, in direct line, allowing
the metal to pass from one set of rolls to the next for the reduction of
steel. TEMPER—The state of or condition of a metal as to its hardness or
toughness produced by either thermal or heat treatment and quench or
cold working or a combination of same in order to bring the metal to its
specified consistency. TENSILE STRENGTH—The maximum load in pounds per square inch that the
sample will carry before breaking under a slowly applied gradually
increasing load during a tensile test. TOLERANCE—The specified permissible deviation from a specified
nominal dimension, the permissible variation in the size of the part or
the allowable variation in chemistry. TOOL STEEL—Actually, any grade of steel that can be used for a tool.
Generally the term tool steel as applied in the steel industry is a
grade of steel characterized by high hardness and resistance to abrasion
coupled in many instances with resistance to softening at elevated
temperatures. These properties are attained with high carbon and high
alloy contents and the steel is usually melted in electric furnaces to
assure cleanliness and homogeneity of the product.
TOUGHNESS—The ability of a metal to absorb energy and deform
plastically before fracturing. It is usually measured by the energy
absorbed in a notch impact test such as the Charpy or Izod Impact Test.
The area under the stress-strain curve in tensile testing is also a
measure of toughness. TUMBLING—Cleaning articles by rotating them in a cylinder with
cleaning materials. ULTIMATE STRENGTH—See tensile strength. ULTRASONIC TESTING—A method of nondestructive testing of steel bars,
plates or parts with high frequency sound waves produced with electronic
equipment. The test is used for locating internal or surface
discontinuities or inhomogeneities in materials. WATER HARDENING—High carbon grades of tool steel, straight carbon
steels and low alloy steels that are hardened by quenching in water
during the heat treating operation. WORK HARDENING—An increase in hardness and strength caused by plastic
deformation at temperatures lower than the recrystallization range. YIELD POINT—The yield point is the load per unit area at which a
marked increase in deformation of the specimen occurs without increase
of load during a tensile test. YIELD STRENGTH—Stress corresponding to some fixed permanent
deformation such as .1 or.2% offset from the modulus or elastic slope.
YOUNG'S MODULUS—Same as modulus of elasticity.
© Copyright 2000 - 2009, by Engineers Edge, LLC All rights reserved.
Disclaimer
|
