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Glossary
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Age Hardening - See heat treatment.
Air Frame Tubing - This tubing is produced for aircraft structural parts. This tubing
is made to special surface quality, mechanical properties and other characteristics
required by Military Specifications (MIL-T...) and SAE Aeronautical Materials Specifications
(AMS ...).
Air Hardening - See heat treatment.
Aircraft Quality – Is a steel which has a special cleanliness rating determined
by magnetic particle testing. The terms “Aircraft Quality” and “Magnaflux Quality”
are considered synonymous.
Alloy Steel - All steels contain carbon and small amounts of silicon, sulfur, manganese
and phosphorus. Steels which contain intentional additions of elements other than
these, or in which silicon and manganese are present in large amounts for the express
purpose of improving or altering any of the physical or mechanical properties of
the steel, are termed alloy steels.
Annealing – Heating and holding to a suitable temperature and then cooling at a
suitable rate, for such purposes as reducing hardness, improving machinability,
facilitating cold working, producing a desired microstructure, or obtaining desired
mechanical, physical or other properties. See also heat treatment.
Austenitic Stainless Steel - Low carbon, iron-chromium-nickel stainless alloys containing
more than 16% chromium, and 4 to 22% nickel to provide an austenitic structure at
normal temperatures. These alloys cannot be hardened by heat treatment, but can
be hardened by cold working. They are normally non-magnetic in the annealed condition,
but can become slightly magnetic after cold working depending upon composition.
Average Wall - See dimensions
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Bearing Quality Steels - Steels suitable for use in balls, rollers and races of
high quality anti-friction bearings.
Bevel - An angular cut on the I.D. or OD of a tube
Billet - As used in the manufacture of seamless tubes, a round bar with dimensions
and other characteristics suitable for piercing into tubing.
Bloom - A semi-finished piece of steel, resulting from the rolling or forging of
an ingot. A bloom is square or not more than twice as wide as thick, and usually
not less than 36 sq. in. in cross-sectional area.
Borescope - An optical device used for inspecting under low magnification the inside
surface of tubes.
Bright Anneal - See heat treatment.
Brinell Hardness - See hardness.
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Camber - The amount of curvature or deviation from exact straightness over any specified
length of tubing.
Capped Steel - Semi-killed steel that has characteristics similar to those of rimmed
steels but to a degree intermediate between rimmed and killed steel. The capping
operation limits the time of gas evolution and prevents the formation of an excessive
number of gas voids within the ingot.
Carbide - A compound consisting of carbon and other elements.
Carbide Precipitation - The phenomenon of carbides coming out of a solid solution,
occurring in stainless steel when heated into the range of 800-1600 Degree degrees
Fahrenheit.
Carbon Steel - A steel consisting of essentially iron, carbon, manganese, and silicon.
Carbon steel has no minimum content required for aluminum, chromium, cobalt, columbium,
molybdenum, nickel, titanium, tungsten, vanadium, zirconium or any other element
added to obtain alloying effect. Small quantities of certain residual elements are
considered incidental.
Carburizing - Adding carbon to the surface of iron-base alloys by heating the metal
below its melting point in contact with carbonaceous solids, liquids or gases. Desired
hardness and toughness properties are developed in the high carbon “case” by quenching
and tempering.
Case Hardening - A heat treatment in which the surface (case) of an iron-base alloy
is made harder than the interior (core). Any of the following methods may be employed:
flame hardening, induction hardening, carburizing, cyaniding or nitriding.
Chamfer – (1) A beveled surface to eliminate an otherwise sharp corner. (2) A relieved
angular cutting edge at a tooth corner.
Charpy Impact 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. The energy absorbed, as determined by the subsequent rise of the pendulum,
is a measure of impact strength or notch toughness. See also impact testing.
Check Analysis - An analysis of the metal after it has been rolled or forged into
semi-finished or finished forms. It is not a check on the ladle analysis, but is
a check against the chemistry ordered.
Chloride Stress Cracking - See Stress Corrosion Cracking.
Cleanup - The amount of metal removal required to obtain desired dimensions and
complete removal of inherent surface imperfections.
Coefficient of Thermal Expansion - A physical property value representing the change
in length per unit length, the change in area per unit area or the change in volume
per unit volume per one degree increase in temperature.
Cold Drawing - A process in which tubing is drawn at room temperature through a
die and over a mandrel to achieve its final size and to provide better surface finish,
closer tolerances, lighter walls, smaller diameters, longer lengths, or a different
combination of mechanical properties from those possible through hot finishing or
direct welding.
Cold Reduction - The reduction of sectional dimensions of a tube by any of a number
of types of cold-working operations.
Cold Sinking - Similar to cold drawing, except that the tube is drawn through a
die, but without an internal mandrel, Usually used only for making heavy wall or
small tubing, where drawing over a mandrel is impractical. Only outside diameter
is closely controlled.
Cold Working - Permanent plastic deformation of a metal below its recrystallization
temperature.
Conditioning - The removal of surface defects (seams, laps, pits, etc from steel.
Conditioning is usually done when the steel is in semi-finished condition (bloom,
billet, slab). It may be accomplished, after an inspection, by chipping, scarfing,
grinding, or machining.
Corrosion - Chemical or electrochemical deterioration of a metal or alloy.
Galvanic Corrosion—Corrosion associated with the presence of two dissimilar metals
in a solution (electrolyte). In principle, it is similar to bath-type plating in
the sense that the anode surface has lost metal (corroded).
Intergranular Corrosion—Corrosion which occurs preferentially along the grain boundaries
of the alloy.
Pitting Corrosion — Non-uniform corrosion usually forming small cavities in the
metal surface.
Corrosion Resistance - The ability to resist attack by corrosion.
Creep Strength - The constant nominal stress that will cause a specified quantity
of creep in a given time at a constant temperature. It is a measure of a tube’s
ability to withstand prolonged stress or load without significant continuous deformation.
In steels it is an important factor only at elevated temperatures.
Crown - Crown, in plates, sheet or strips, is characterized by a greater thickness
in the middle than at the edges. It may be caused by a deflecting (bending) of the
rolls or by worn rolls,
Cut Length - Refers to tubing ordered to a specified length and permitting a tolerance
of a standardized fraction of an inch over but nothing under the specified length.
Cyaniding - A process in which an iron-base alloy is heated in contact with a cyanide
salt so that the surface absorbs carbon and nitrogen. Cyaniding is followed by quenching
and tempering to produce a case with a desired combination of hardness and toughness.
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Decarburization - The loss of carbon from the surface of an iron-base alloy as the
result of heating in an environment which removes the carbon. In medium or high
carbon steels, decarburization leads to a pronounced lowering of the fatigue limit.
Density - The mass per unit volume of a substance, usually expressed in the tubing
industry in pounds per cubic inch.
Dimensions –
- OD - Outside Diameter. Specified in inches and fractions of an inch, or inches and
decimals of an inch. OD = (2 x Wall) + ID
- ID - Inside Diameter. Specified in
the same units as the OD. ID = OD – (2 x Wall)
- Wall - Wall Thickness or Gage.
Specified in either fractions or decimals of an inch or by a “wire gage” number.
In the United States, the most common gage used for tubing is the “Birmingham” iron
wire gage, designated “BWG”. Wall = (OD – ID) / 2
- Nominal - The theoretical
or stated value of the OD, ID or wall dimension as specified by the customer.
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Maximum and Minimum - The dimensions resulting after applying the proper tolerances
to the nominal dimensions.
- Minimum Wall - Generally, the lightest wall permitted
within specified tolerances. A “minimum wall tube” is one whose wall thickness is
not permitted to fall below the specified nominal measurement.
- Average Wall
- A tube whose wall thickness is permitted to range over or under the specified
nominal wall measurement within certain defined tolerances.
Duplex Stainless Steels – Contains a mix of austenite and ferrite that yields significantly
higher yield strength and improved stress corrosion cracking resistance vs. T 304.
Duplex stainless steels are magnetic.
Ductility - The ability of a tube to deform plastically. Frequently, elongation
during tensile testing is used as a measurement of this property.
Dye Penetrant Inspection - Non-destructive test employing dye or fluorescent chemical
and sometimes black light to detect surface defects.
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Eccentricity - The displacement of the ID of the tube with respect to its OD Eccentricity
results in the variation of wall thickness normal to seamless tubing.
Eddy Current - Non-destructive testing method using eddy current flow for the purpose
of recognizing a discontinuity in the piece being tested.
Elastic Limit - A measure of the maximum stress that may be applied to a tube without
leaving a permanent deformation or strain after the stress is released.
Electric Furnace Process - One of the common methods used for melting and refining
stainless and some alloy steels. It involves the use of electric power as the sole
source of heat, thereby preventing contamination of the steel by impurities in the
fuel as in other melting processes.
- Electric Resistance Welded Tubing – Carbon steel tubing made from strip by electric
resistance heating and pressure, the strip being part of the electrical circuit.
The electric current, which may be introduced into the strip through electrodes
or by induction, generates the welding heat through the electrical resistance of
the strip.
- As Welded Hot Rolled - ERW tubing exhibiting the pickled surface
of hot rolled strip.
- As Welded Cold RoIled - ERW tubing exhibiting the surface
of cold rolled strip.
- As Drawn tubing is unheat-treated, cold drawn tubing and
has a scale free cold drawn surface.
- Bright Annealed - Welded tubing normalized
in a controlled atmosphere furnace and which exhibits a bright surface.
- Pickled
tubing has had the scale from hot fabrication or heat treatment removed by one of
several types of acid solutions.
- Gun Metal Finish - Welded tubing normalized,
annealed, or stress relieved in a controlled atmosphere furnace that exhibits a
gun metal finish. Flash-In tubing is welded tubing which still retains the I.D.
bead or flash formed during the welding operation. It can be furnished in either
the as-welded, sunk or heat-treated condition.
- Flash-Removed - Welded tubing
from which the I.D. flash formed during the welding operation has been removed by
some mechanical method. It can be furnished in either the as-welded, sunk or heat-treated
condition.
- Special Smooth ID - A cold drawn tube in which special attention
is paid to the internal surface. Depth of pits and scores in ID are guaranteed to
be below published maximum depths. Microinch finish is guaranteed in ERW tubes.
Elongation - The amount of permanent stretch, usually referring to a measurement
of a specimen after fracture in a tensile test. It is expressed as a percentage
of the original gage length.
Endurance Limit - The maximum stress below which a material can presumably endure
an infinite number of stress cycles.
Etch Test - Exposure of a specimen to acid attack for the purpose of disclosing
the presence of foreign matter, defects, segregation pattern, or flow lines.
Extrusion - Production process in which steel is forced by compression through a
die into solids (round or special shape) or through a die and over a mandrel to
form a tubular shape.
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Fatigue Limit - Synonymous with Endurance Limit.
Ferritic Stainless Steels - The designation used for certain high chromium content
steels that exhibit microstructures consisting mainly of ferrite at ordinary temperatures.
Ferritic stainless steels are divided into two classifications: hardenable, and
non-hardenable. When rapidly cooled from elevated temperatures the non-hardenable
grades (ferritic) have a ferritic microstructure. The hardenable grades (martensitic)
will exhibit a martensitic micro-structure when rapidly cooled. Ferritic and martensitic
stainless steel alloys are magnetic in all conditions.
Finish - In the steel industry, refers to the type of surface condition desired
or existing in the finished product.
Finish Anneal - See heat treatment.
Finish Machine Size - Normally specified in terms of the maximum machined OD and
the minimum machined ID as applied to tubular parts. Finish machine size represents
the size of the part as it comes from the final machining operation. From this size
the tube mill can calculate a tube size which will be guaranteed to cleanup upon
machining.
Flame Hardening - A process of heating the surface layer of an iron-base alloy above
the transformation temperature range by means of the flame of a high temperature
torch, followed by quenching.
Flanged End - In a flanged end the tube has been belied or expanded and a flange
turned over until the wall of the tube end is at right angles to the wall of the
tube.
Flare Test – A test applied to tube, involving a tapered expansion over a cone.
Similar to a pin-expansion test.
Flash-In Tubing - See Electric Resistance Welded Tubing.
Flash Removed - See Electric Resistance Welded Tubing,
Forging - Used as a general term to describe the roiling, pressing or hammering
of steel which displaces the metal under compression by a locally applied force,
usually at hot working temperatures.
Fracture Strength - As usually related to the tensile test, fracture strength or
true breaking strength is defined as the load on the specimen at the time of fracture.
Full Anneal - See heat treatment.
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Gages, Gauges - A measurement of thickness. There are various standard gages such
as United States Standard Gage (USS), Galvanized Sheet Gage (GSG), Birmingham Wire
Gage (BWG).
Grain Size - A measure of the size of individual metallic crystals usually expressed
as an average. Grain size is reported as a number in accordance with procedures
described in ASTM grain size specifications.
- Apparent Ferrite Grain Size is the average of the size of the ferrite grains as
microscopically viewed in the normalized or annealed condition.
- Austenitic Grain
Size, which is usually measured by the McQuaid-Ehn method, represents the austenitic
grain size of a material at a prescribed temperature above the upper critical, frequently
1700 degree F. For austenitic stainless steels the grain size does not change upon
cooling and is that observed microscopically at room temperature.
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Hardenability - The property in steel that determines the depth and distribution
of hardness induced by cooling from a suitable elevated temperature. The hardness
can vary with the cooling rate.
Hardness - A measure of the degree of a material’s resistance to indentation. It
is usually determined by measuring resistance to penetration, by such tests as Brinell,
Rockwell, and Vickers.
Heat Exchanger Tube – A tube for use in apparatus in which fluid inside the tube
will be heated or cooled by fluid outside the tube. The term usually is not applied
to coiled tubes or to tubes for use in refrigerators or radiators.
Heat Treatment - A combination of heating and cooling operations applied to a metal
or alloy in the solid state to obtain desired conditions or properties. Heating
for the sole purpose of hot working is excluded from the meaning of this definition.
See various types below.
- Age Hardening - Hardening by aging, usually after rapid cooling or cold working.
Hardening is a result of a precipitation process, often submicroscopic, which occurs
when a supersaturated solid solution is naturally aged at atmospheric temperature
or artificially aged in some specific range of elevated temperature. Aging occurs
more rapidly at higher temperatures. (Synonymous with precipitation hardening)
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Air Hardening - Heating a suitable grade of steel with high hardenability above
the critical temperature range and then cooling in air for the purpose of hardening.
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Annealing - Annealing is a heat treatment process that usually involves a relatively
slow cooling after holding the material for some time at the annealing temperature.
The purpose of the annealing treatment may include the following: (a) to induce
softness; (b) to remove internal stresses; (c) to refine the grain size; (d) to
modify physical and or mechanical properties; (e) to produce a definite microstructure;
(f) to improve machinability. It is generally desirable to use more specific terms
in describing the heat treatment to be used, e.g., finish anneal, full anneal or
medium anneal, as applicable
- Bright Anneal - Carried out in a controlled furnace
atmosphere, so that surface oxidation is reduced to a minimum and the tube surface
remains relatively bright.
- Dead Soft - A heat treatment applied to achieve maximum
softness and ductility.
- Drawing - Synonymous with ‘Tempering’, which is preferable.
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Finish Anneal - Heating of cold-worked tubing to a temperature below the lower critical,
usually 950 Degree. Generally this treatment will relieve peak stresses without
altering hardness to any extent.
- Full Anneal - Heating to a temperature above
the upper critical and slow cooling below the lower critical.
- Isothermal Anneal
- Austenitizing a heat treatable alloy and cooling to and holding at a temperature
at which austenite transforms to a relatively soft ferrite-carbide aggregate.
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Medium Anneal - Subjecting tubing to a subcritical temperature to obtain specific
mechanical properties.
- Normalize - Heating a ferrous metal to a temperature
approximately 100 Degree F. above the upper critical temperature and cooling in
still air.
- Quenching - A process of rapid cooling from an elevated temperature,
by contact with liquids or gases.
- Soft Anneal - A high temperature stress relieving
anneal usually performed in the temperature range of 1250 to 1350 Degree F. This
anneal reduces hardness and strength of a cold worked steel to achieve near maximum
softness.
- Solution Anneal - Heating steel into a temperature range wherein certain
elements or compounds dissolve, followed by cooling at a rate sufficient to maintain
these elements in solution at room temperature. The expression is normally applied
to stainless and other special steels.
- Spheroidizing Anneal - A general term
which refers to heat treatments, that promote spheroidal or globular forms of carbide
in carbon or alloy steels.
- Stabilizing Anneal - A treatment applied to austenitic
stainless steels wherein carbides of various forms are deliberately precipitated.
Sufficient additional time is provided at the elevated temperature to diffuse chromium
into the areas adjacent to the carbides (usually grain boundaries). This treatment
is intended to lessen the chance of intergranular corrosion.
- Stress Relieving
- A heat treatment which reduces internal residual stresses that have been induced
in metals by casting, quenching, welding, cold working, etc. The metal is soaked
at a suitable temperature for a sufficient time to allow readjustment of stresses.
The temperature of stress relieving is always below the transformation range. Finish
anneal, medium anneal and soft anneal (sub-critical) describe specific types of
stress relief anneals.
- Tempering - Reheating quenched or normalized steel to a temperature below the transformation
range (lower critical) followed by any desired rate of cooling.
Hot Finished Seamless Tubing - Tubing produced by rotary piercing, extrusion, and
other hot working processes without subsequent cold finishing operations.
Hot Rolled ERW Tubing - As welded electric resistance welded tubing made from hot
rolled strip or sheet.
Hot Shortness (Red Shortness) - A condition encountered in some metals wherein ductility
is lessened at hot working temperatures.
Hot Working - The mechanical working of metal above the recrystallization temperature.
Huey Test - A corrosion test for stainless steels. The weight loss per unit area
is measured after each of five 48-hour boils in 65 % nitric acid (per ASTM A 262
Practice C). The test results are calculated to and reported as the average corrosive
rate of the five boils in inches per month (1pm) corrosion rates. The test is used
to determine the suitability of a material for nitric acid service. Since most of
the weight loss is due to intergranular attack, the Huey test is commonly used as
an indication of the resistance of a stainless steel to intergranular corrosion.
Hydrostatic Test - A test in which a liquid, usually water, under pressure, is used
internally to detect and locate leaks in a tube of a fabricated structure.
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Impact Testing - There are several methods of determining the toughness of a steel,
but the Izod and Charpy notched-bar tests are used quite widely. In both tests,
the samples are cooled or heated to the desired test temperature, then struck once
with a pendulum that fractures the specimen. The energy required to fracture the
specimen, the impact strength, is measured in foot-pounds.
Inclusions - Particles of nonmetallic impurities, usually oxides, sulphides, silicates,
which are mechanically held in metals and alloys during solidification.
Induction Heating - A process of heating by electrical induction.
Ingot - A cast metal shape suitable for subsequent rolling or forging. Ingot Mold
- A mold in which ingots are cast. Molds may be circular, square, or rectangular
in shape, with walls of various thickness. Some molds are of larger cross section
at the bottom; others are larger at the top.
Integral Finned Tubing - Tubing with raised surface fins formed from the wall of
the tube itself.
Intergranular Corrosion - A type of electrochemical corrosion that progresses preferentially
along the grain boundaries of an alloy, usually because the grain boundary regions
contain material anodic to the central regions of the grain.
Internal Soundness - Refers to condition of inside of material—lack of defects,
pipe, segregation, non-uniformity of composition.
Isothermal Anneal—See heat treatment.
Izod Impact Test—See Impact Strength Testing.
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Jominy Test - Hardenability test performed usually on alloy steels to determine
depth and degree of hardness resulting from a standard end quenching method with
cold water.
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Killed Steel - Steel deoxidized with an agent such as silicon or aluminum to reduce
the free oxygen content so that no harmful reaction occurs between carbon and oxygen
during solidification.
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Ladle - A large vessel into which molten steel or molten slag is received and handled.
Ladle Analysis - Chemical analysis obtained from a sample taken during the pouring
of the steel.
Laminations - Defects resulting from the presence of blisters, seams or foreign
inclusions aligned parallel to the worked surface of a metal.
Lap - A surface defect caused from folding the surface of an ingot, bloom or bar
during hot rolling operations and then rolling or forging the fold into the surface.
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Machinability - A measure of the relative ease with which steel may be machined.
Adding sulphur, phosphorous or selenium to a heat of steel can improve the metal’s
machinability.
Machining - The deliberate removal of metal by one or more of several processes.
Macroetch - A testing procedure for locating and identifying porosity, pipes, bursts,
unsoundness, inclusions, segregations, carburization, flow lines from hot working,
etc. Surface of the test piece should be reasonably smooth or even polished. After
applying a suitable etching solution, the structure developed by the action of the
reagent may be observed without a microscope.
Magnaflux Test - This test is conducted by suitably magnetizing the material and
applying a prepared wet or dry magnetic powder or fluid which adheres to it along
lines of flux leakage. It shows the existence of surface and slightly subsurface
non-uniformities.
Malleability - The property that determines the ease of deforming a metal when the
material is subjected to rolling or hammering. The more malleable metals can he
hammered or rolled into thin sheet more easily than others.
Mandrel - (1) A device used to retain the cavity in hollow metal products during
working. (2) A metal bar around which other metal may he cast, bent, formed or shaped.
Maraging - A process of improving the mechanical strength of certain ferrous alloys.
The name was derived from two hardening reactions: martensite and aging. The maraging
strengthening mechanism is based on the age hardening (precipitation hardening)
of extra-low carbon martensite.
Martensite - A constituent in quenched steel formed without diffusion and only during
rapid cooling below the martensitic start (Ms) temperature. Martensite is the hardest
of the transformation products of austenite.
McQuaid-Ehn Test - A special test for revealing the austenitic grain size of ferritic
steels when the steel is heated to 1700 Degree F. and carburized. There are eight
standard McQuaid-Ehn grain sizes—sizes 5 to 8 are considered fine grain and sizes
under 5 are considered coarse grain.
Mechanical Properties - Those properties of a material that reveal the elastic and
in-elastic reaction when force is applied, or that involve the relationship between
stress and strain; for example, the modulus of elasticity hardness, tensile strength
and fatigue limit. These properties have often been referred to as “physical properties,”
but the term “mechanical properties” is correct.
Mechanical Tubing - Used for a variety of mechanical and structural purposes, as
opposed to pressure tubing, which is used to contain or conduct fluids or gases
under pressure. It is used for the starting stock for machined or formed parts of
industrial, automotive, agricultural aircraft, transportation, material handling
and household equipment. It may be hot finished or cold drawn. It is commonly manufactured
to consumer specifications covering chemical analysis and mechanical properties.
It is made to exact OD and wall thickness dimensions and custom produced to end-use
applications in seamless and welded condition.
Metallography - The science dealing with the constitution, and structure of metals
and alloys as revealed by the unaided eye or by such tools as low powered magnification,
optical microscope, electron microscope and diffraction or X-ray techniques.
Microcleanliness - Refers to the extent or quality of nonmetallic inclusions observed
by examination under a microscope.
Micro-Etch - Micro-etching is used for the examination of a sample under a microscope.
Etching solutions tend to reveal structural details because of preferential chemical
attack on the polished surface.
Minimum Wall - Any wall having tolerances specified all on the plus side.
Modulus of Elasticity - The ratio of stress applied to a material and the resulting
strain occurring at the stresses below the elastic limit
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Nitriding - A process of case hardening in which a ferrous alloy, usually of special
composition, is heated in an atmosphere of cracked ammonia or in contact with nitrogenous
material to produce surface hardening without quenching by the absorption of nitrogen.
Nitriding is normally conducted in a range from 900 to 1000 Degree F.
Non-Destructive Testing - Methods of detecting defects without destroying or permanently
changing the material being tested. Test methods include ultrasonic, eddy current,
magnetic particle, liquid, penetrant, and X-ray.
Notch Brittleness - Susceptibility of a material to brittle fracture at points of
stress concentration.
Notch Sensitivity - A measure of the reduction in strength of a metal caused by
the presence of stress concentration.
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Open Hearth Furnace – A reverberatory melting furnace with a shallow hearth and
a low roof. The flame passes over the charge in the hearth, causing the charge to
be heated both by direct flame and radiation from the roof and sidewalls of the
furnace.
Ovality - The difference between the maximum and minimum outside diameters of any
one cross section of a tube. It is a measure of deviation from roundness.
Oxidation - In its simplest terms, oxidation means the combination of any substance
with oxygen. Scale developed during heat treatment is a form of oxidation.
Oxide - A compound consisting of oxygen and one or more metallic elements.
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Passivate - The changing of the chemically active surface of a metal to a much less
active state by the application of the proper chemical treatment or by applying
an induced electrical current and voltage for cathodic or anodic protection from
corrosion. An example of chemically passivating stainless steel would be to immerse
stainless in a hot solution of approximately 10 to 20 per cent by volume nitric
acid and water.
Photomicrograph - A photographic reproduction of an object magnified more than ten
times used to show microstructure characteristics of steel.
Physical Properties - Those properties not specifically related to reaction to external
forces. These include such properties as density, electrical resistance, coefficient
of thermal conductivity.
Pickling - Use of solutions, usually acids, to remove surface oxides from a tube,
may also be used to produce a desired surface finish.
Piercing - A seamless tubemaking method in which a hot billet is gripped and rotated
by rolls or cones and directed over a piercer point which is held on the end of
a mandrel bar.
Pit - A sharp, usually small, depression in the surface of metal. Pitting is forming
small sharp cavities in a metal surface by nonuniform electro-deposition or by corrosion.
Porosity - Unsoundness caused in cast metals by the presence of blowholes or shrinkage
cavities.
Pressure Tubing - Tubing produced for the purpose of containing or conducting fluids
or gases under pressure. It is produced to exact diameters and decimal wall thicknesses
to ASTM or ASME specifications for boiler, heat exchanger, condenser tubes, etc.
Made by both seamless and welded processes in carbon, alloy, and stainless steels.
Profilometer - An instrument used for measuring surface finish. The vertical movements
of a stylus as it traverses the surface are amplified electromagnetically and recorded
(or indicated) as the surface roughness.
Proof Stress - The load per square inch of the original cross-sectional area which,
when removed, has caused a permanent elongation not exceeding a defined amount (usually
0.0001 per inch of gage length). A test of this type is more commonly used in Europe
than in this country, where it largely has been replaced by yield strength measurements.
Pyrometer - An instrument of any of various types used for measuring temperatures.
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Quench Cracking – Cracking resulting from stresses produced during the austenite
to martensite transformation during heat treating (quench and tempering). Any condition
that concentrates the stresses encountered in quenching will promote the formation
of quench cracks (e.g. corners, hoves, or keyways; too fast a quench medium; excessive
time delay from quench to temper).
Quench Hardening – Hardening a ferrous alloy by austenitizing and then cooling rapidly
enough so that some or all of the austenite transforms to martensite.
Quenching - See heat treatment.
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Recrystallization - The reversion of distorted cold worked microstructure to a new,
strain-free structure during annealing.
Reduction of Area - A measure of ductility determined in a tensile test. It is the
maximum reduction, at the fracture, of the cross section area of a specimen, as
compared with its original cross section area.
Residual Stress – Stress present in a body that is free of external forces or thermal
gradients.
Rimmed Steel - A steel that forms a relatively clean outer layer (rim) during solidification.
Sheet and strip made from such steel has good surface quality and is frequently
used for ERW tubing.
Rockwell Hardness - See hardness.
Roto-Rock (Tube Reducing or Rockrite) - A method of cold finishing tubing in which
a machine rolls or rocks a split die over a tube. The tube is supported on the inside
by a tapered mandrel.
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Scale - An oxide of iron that forms on the surface of hot steel.
Seam - A tight, but unwelded imperfection on the surface of a wrought metal product.
Segregation - Non-uniform distribution of alloying elements, impurities or microphases.
Semi-Killed Steel - Steel that is incompletely deoxidized to permit the evolution
of carbon monoxide, thereby offsetting solidification shrinkage.
Sensitization - Sensitization of stainless steel is defined as a susceptibility
to preferential grain boundary attack. Material that exhibits grain boundary carbide
precipitation may or may not be sensitized.
Soak - To hold an ingot, slab, bloom, billet or other piece of steel in a hot furnace,
pit or chamber to secure uniform temperature.
Soaking Pit - A furnace or pit for the heating of ingots of steel to make their
temperature uniform prior to rolling or forging.
Soft Anneal - See heat treatment.
Spark Test -
Special Smooth I.D. (SSID) - See Electric Resistance Welding Tubing.
Specification - A document defining the measurements, tests, and other requirements
to which a product must conform—typically covering chemistry, mechanical properties,
tolerances, finish, reports, marking and packaging.
Spheroidize Anneal - See heat treatment.
Spinning - A type of forming (hot or cold) which involves rotating a tube at high
speed against fixed or rolling tools for the purpose of altering shape, size, etc.
Stabilizing Anneal - See heat treatment.
Stainless Steel – Steel containing 10.5% or more chromium. Invented in 1903, metallurgists
discovered that adding chromium to carbon steels imparted much improved corrosion
resistance. Other major alloying elements include nickel, manganese, molybdenum,
silicon and titanium.
Stress Corrosion Cracking - Cracking of metals under combined action of temperature,
corrosion and stress. The stress can be either applied or residual. Austenitic stainless
steels are especially susceptible to cracking in chloride containing environments.
Stress Relief Anneal - See heat treatment.
Stretch Straightening – A process for straightening rod, tube, and shapes by the
application of tension at the ends of the stock.
Strip - A flat-rolled steel product that serves as the raw material for welded tubing.
Sunk or Sink Drawn - Tubing drawn through a die with no inside mandrel to control
I.D. or wall thickness.
Swaged - A mechanical reduction of the cross sectional area of a metal, performed
hot or cold by forging, pressing or hammering.
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Tapping - The act of pouring molten metal from a furnace into a ladle.
Teeming - Act of pouring molten metal from a ladle into an ingot mold.
Tempering - See heat treatment.
Tensile Strength - The maximum load per square inch of original cross-sectional
area carried during a tension test to failure of the specimen. This term is preferred
over the formerly used ultimate strength.
Thermal Conductivity - A measure of the ease with which heat is transmitted through
a material.
Tungsten Inert Gas Welding – TIG welding process used for stainless steel and stainless
grades.
Tolerance - Permissible variation.
Torsion - A twisting action resulting in shear stresses and strains.
Toughness - A measure of ability to absorb energy and deform plastically before
fracturing.
Transformation Temperature - The temperature at which a change in phase occurs in
steels. The term is sometimes used to denote the limiting temperature of a transformation
range,
Transverse Tension Test - A tension test for evaluating mechanical properties of
a material in a direction transverse to that of rolling.
Turning - A method for removing the surface from a work piece by bringing the cutting
edge of a tool against it while the piece or tool is rotated.
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Ultimate Strength - See tensile strength.
Ultrasonic Testing - The method of detecting defects in tubes or welds by passing
high frequency sound waves into a material then monitoring and evaluating the reflected
signals.
Upsetting - A metalworking operation similar to forging, generally used to thicken
the ends of tubes prior to threading.
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Vickers Hardness Test - See hardness.
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Work Hardening - Hardness developed in metal as a result of cold working. See cold
working.
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