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GB/T 20566-2006 PDF in English

GB/T 20566-2006 (GB/T20566-2006, GBT 20566-2006, GBT20566-2006)
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GB/T 20566-2006: PDF in English (GBT 20566-2006)

GB/T 20566-2006
ICS 77.140.01
H 40
Terminology of steel and alloy
Issued by. General Administration of Quality Supervision, Inspection and
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms ... 4 
Appendix B (Informative) Index in English ... 25 
Terminology of steel and alloy
1 Scope
This standard specifies the terms and definitions which are commonly used for
steel and alloys.
This standard applies to the preparation of standards of different levels and
related technical documents for steel and alloys and their products.
2 Normative references
The provisions in following documents become the provisions of this standard
through reference in this standard. For the dated references, the subsequent
amendments (excluding corrections) or revisions do not apply to this standard;
however, parties who reach an agreement based on this standard are
encouraged to study if the latest versions of these documents are applicable.
For undated references, the latest edition of the referenced document applies.
GB/T 13304 Steel classification (GB/T 13304-1991, neq ISO 4948/1.1982
Steel Classification - Part 1. classification of steels into unalloyed and all
alloyed steels based on chemical composition, ISO 4948/2.1981 Steel
classification - Part 2. Classification of unalloyed and alloyed steels based
on main quality classed and main property or application characteristic)
3 Terms
A material which contains iron as a main element, has a carbon content of
generally not more than 2%, and contains other elements. The carbon
content in chrome steel may be greater than 2%, but 2% is usually the limit
between steel and cast iron.
3.1.1 Steel classified by chemical composition
Unalloyed steel
Special quality steel
The steel whose quality and performance need special control in the
production process, especially the strict control of the content of such
impurities as sulfur and phosphorus as well as the purity of steel. Special
quality steels include special quality non-alloy steels, special quality low alloy
steels and special quality alloy steels.
3.1.3 Steel classified by application and use characteristics
Carbon structural steel
The carbon steel which is used for buildings, bridges, ships, vehicles and
other structures, must have a certain strength and, if necessary, impact
performance and weldability.
High strength low alloy structural steel
The carbon steel which is used for buildings, bridges, ships, vehicles,
pressure vessels, and other structures. The carbon content (melting analysis)
is generally not more than 0.20%, the total content of alloying elements is
generally not more than 2.5%, the yield strength is not less than 295 MPa. It
has good impact toughness and weldability.
Steel with improved atmospheric corrosion resistance
Weathering resistance steel
Steel to which copper, phosphorus, chromium, nickel and other elements are
added to improve the atmospheric corrosion resistance. These steels are
classified into steel with highly improved atmospheric corrosion resistances
and steel with improved atmospheric corrosion resistances for welded
Steel for building structure
Steel which is used to build high-rise and important building structures. It is
required to have high impact toughness, sufficient strength, good welding
performance, a certain yield ratio, and thickness direction performance if
Steel for welding
Steel which is used to weld steel (including welding rods, welding wire,
welding strip). It has strict requirements for chemical composition, which
requires to control the carbon content and limit such hazardous substances
such as sulfur and phosphorus. Based on chemical composition, welding
steel can be divided into three types. non-alloy steel, low alloy steel and alloy
Free-cutting steel
The steel to which such elements as sulfur, phosphorus, lead, selenium,
tellurium, calcium, etc. (one or more elements are added) are added to
significantly improve the cutting performance to facilitate automated
Steel for deep drawing
Steel which has excellent stamping properties. It is usually aluminum-killed
low carbon steel. The optimal deep drawing performance is obtained usually
by reducing the content of carbon, silicon, manganese, sulfur, and
phosphorus, controlling the range of the aluminum content as well as the
processing technology. Based on the stamping grade, it is divided into two
types. steel for deep drawing and steel for ultra-deep drawing.
Interstitial free steel
The steel with good deep drawing performance, which is obtained by adding
an appropriate amount of titanium and niobium to a low carbon steel which
has a carbon content of not more than 0.01% to absorb interstitial atom
carbon and nitrogen of the steel to form carbides and nitride particles.
Dual phase steel
A high strength low alloy formable steel. The microstructure consists of a soft
ferrite crystal grain matrix and hard diffuse martensite particles, it has high
strength and plasticity as well as good formability.
and tempered steel, case hardened steel and cold plastic formed steel.
Steel for pressure work
Steel which is used for pressure processing (such as rolling, forging, drawing,
etc.) and is plastically deformed into parts or products. Based on whether
the steel is heated before processing, it is divided into steel for hot pressure
work and steel for cold pressure work.
Steel for cut work
Steel for cold machining
Steel which is used for the cut work of the cutting machine tools (such as
turning, milling, planing, grinding, etc.) at normal temperature.
Cold heading steel
Cold heading steel and rivet steel
Steel which is used for upsetting under normal temperature to make rivets,
bolts and nuts. It is represented by adding the letter “ML” in front of the steel
grade. In addition to chemical composition and mechanical properties, it also
requires the surface decarburization layer and cold heading properties. It is
mainly quality carbon structural steel and alloy structural steel.
Structural steel subject to end-quench harden-ability
Steel which is subjected to end quenching in accordance with the end
quenching method specified in the relevant standard, ensures the upper and
lower limits of hardness within certain distance from the quenching end falls
into a certain range. The grades of this type of steel are often represented
by the symbol “H” (for end-quench hardenability zone).
Steel for armor
Plate steels which are used to manufacture tanks and armor to defend
against various armor-through and armor-piercing projectiles. It is required
to have high hardness and sufficient toughness, especially low temperature
Spring steel
Steels which is used to manufacture various springs and elastic elements. It
is required to have excellent mechanical properties (especially elastic limit,
strength limit and yield ratio), fatigue properties, hardenability, physical and
chemical properties (heat resistance, low temperature resistance, corrosion
resistance), and processing properties. Based on chemical composition, it
can be divided into carbon spring steel, alloy spring steel and special spring
Tool steel
A general term for steels which are used in the manufacture of various
cutting tools, forming tools, and measuring tools. It is usually divided into
non-alloy tool steel, alloy tool steel and high speed tool steel. The required
properties are mainly strength, toughness, hardness, wear resistance and
tempering stability.
Unalloy tool steel
Steel which is used for the manufacture of various general small tools
without the addition of alloying elements. The carbon content is between
0.65% and 1.35 %, which belongs to eutectoid steel or hypereutectoid steel.
Alloy tool steel
Tool steel which contains high carbon and alloying elements such as
chromium, tungsten, molybdenum, vanadium, and nickel. Based on the use
and performance, it can be divided into measuring tool steel, impact resistant
tool steel, cold work die steel, hot work die steel, plastic die steel and non-
magnetic die steel.
High speed tool steel
High carbon alloy steel which is mainly used for high speed cutting tools.
Based on the basic composition series of alloys, it is divided into tungsten
steel, molybdenum steel, tungsten molybdenum steel, cobalt molybdenum
steel. Based on use, it is divided into general high speed steel and super-
hard high speed steel.
Steel which uses chromium, molybdenum, nickel, tungsten, vanadium, etc.
as main alloying elements and is used to manufacture steam turbine’s vane.
Based on different working temperatures, it is required for normal
temperature mechanical properties and high temperature transient
mechanical properties as well as long-term strength, plasticity and creep
Silicon steel for electrical grade
The ferrosilicon soft magnetic materials which are mainly used in various
transformers, motors and engine cores, have extremely low carbon content
and silicon content generally ranging from 0.5% to 4.5%. It is divided into
two types. grain-oriented silicon steel and grain non-oriented silicon steel.
Grain-oriented silicon steel
The grains are preferentially oriented by deformation and recrystallization
annealing, the grain orientation is aligned along the rolling direction, the
magnetic properties in the rolling direction are significantly better than the
vertical rolling direction. Usually the silicon content is about 3.2%.
Grain non-oriented silicon steel
Silicon steel which has substantially the same magnetic properties in the
rolling direction and the vertical rolling direction.
Pure iron for electrical grade
The non-alloyed iron-based soft-magnetic materials which are used to
manufacture electromagnetic components, featured by low carbon and other
impurity elements, high magnetic induction strength, high magnetic
permeability, and low coercive force
3.1.4 Steel classified by smelting method and degree of deoxidation
Converter steel
Steel which is smelted with a converter. Based on the lining refractory
properties, it is divided into alkaline converter steel and acid converter steel.
secondary remelting refining process through slag resistance heat in the
electroslag furnace.
Refining steel outside furnace
The steel which is obtained by placing the molten steel that has been initially
smelted in the electric furnace or converter in a ladle or other special
container, being subjected to a refining process such as degassing,
deoxidation, desulfurization, decarburization, removal of inclusions, and fine
adjustment of composition.
Killed steel
Steel which, in molten state, is fully deoxidized before pouring, and calm
without boiling in the pouring and solidification process. The killed steel has
a dense structure, small segregation and uniform composition.
Semi-killed steel
Semi-deoxidized steel whose degree of deoxidation is between that of the
killed steel and the rimmed steel. There is a slight boiling phenomenon
during pouring, the yield of steel is higher than that of killed steel, the
segregation is smaller than that of rimmed steel.
Rimmed steel
Steel which is not deoxidized or is only slightly deoxidized. When the molten
steel is poured and before it is solidified, a carbon-oxygen reaction occurs in
the ingot mold, which emits carbon monoxide to generate a strong boiling
phenomenon. This kind of steel does not have concentrated shrinkage
cavities, the steel has a high yield rate, but the composition is large in
segregation and the quality is uneven.
3.1.5 Steel classified by metallographic structure
Austenitic steel
The steel whose structure at normal temperature after solution annealing is
Ledeburite steel
Steel with a ledeburite structure. At high temperature, the ledeburite is a co-
crystal of austenite and cementite; at normal temperature, the ledeburite is
a mixture of pearlite and cementite.
Eutectoid steel
Pearlite-structure steel which has a carbon content of eutectoid component
(generally carbon content is 0.80%).
Hypoeutectoid steel
Ferritic & pearlitic steel which has a carbon content lower than the eutectoid
steel component (carbon content is usually 0.02% ~ 0.8%).
Hypereutectoid steel
Pearlite & cementite-structure steel which has a carbon content higher than
eutectoid component (carbon content is usually 0.8% ~ 2.0%).
Special alloy
Alloy which has special physicochemical properties and special functions. It
usually includes high temperature superalloy, precious alloys, corrosion
resistant alloys, high resistance for electrical heating, and other special
functional materials.
Heat resisting superalloy
Heat resisting alloy
Alloy that can withstand certain stresses and has oxidation or corrosion
resistance at high temperatures ranging from 600 °C ~ 1200 °C. Based on
the matrix constituent elements, it can be divided into three types. iron-based
(iron-nickel-based) heat resisting superalloy, nickel-based heat resisting
superalloy and cobalt-based heat resisting superalloy. Based on the main
strengthening characteristics of the alloy, it can be divided into solid solution
strengthened heat resisting superalloy and age hardening heat resisting
cold state. Based on the matrix constituent elements, it can be divided into
an iron-based alloy, an iron-cobalt-based alloy, an iron-cobalt-molybdenum-
based alloy, an iron-chromium-cobalt-based alloy, and the like. In addition to
high coercivity values, various types of deformable permanent magnetic
alloys have different magnetic properties.
Elasticity alloy
Alloy which has good elastic properties. It is usually divided into two types.
high elastic alloys and constant elastic alloys. Based on the matrix
constituent elements, it can be divided into an iron-nickel-based alloy, an
iron-cobalt-based alloy, an iron-chromium-based alloy, and the like. In
addition to the elastic properties, the elasticity alloys are also featured by
non-magnetic, shock-resistant, wear-resistant, corrosion-resistant, specific
frequency temperature coefficients, and so on.
Expansion alloy
Alloy which has a specific coefficient of linear expansion. Based on the
matrix constituent elements, it can be divided into an iron-based alloy, an
iron-nickel-based alloy, an iron-nickel-cobalt-based alloy, a nickel-based
alloy, and the like. Based on the different linear expansion coefficients, it can
be divided into low expansion alloys, fixed expansion alloys and high
expansion alloys. In addition to the specific expansion properties, various
alloys are also featured by non-magnetic, corrosion-resistant, easy-cutting,
high strength and so on.
Thermostatic biomaterials
Composite materials which are formed by the two or more layers of metals
having different coefficients of linear expansion. The component layer is
composed of a high expansion layer, a low expansion layer and an
intermediate layer.
Electrical resistance alloy
Alloy which is mainly technically featured by resistance characteristics. It
mainly includes precious resistance alloys, strain resistance alloys,
thermistor alloys and electrothermal alloys.
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.