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Basic Concepts And Production Methods Of Steel
Basic Concepts And Production Methods Of Steel
2011-10-29
Introduction To Steel Terminology
Introduction To Steel Terminology
2013-07-14

Our Steel Number Expression Method

A. Overview of China's steel number expression method

Steel number for short, is the name taken for each specific steel product, is a common language for people to understand the steel. China’s steel number, according to the national standard “Steel Product Grade Method” (GB221-79), using the hanyu pinyin letters, chemical element symbols and Arabic numerals combined method of expression. That is.

① The chemical elements in the steel number are expressed by international chemical symbols, such as Si, Mn, Cr ……, etc. Mixed rare earth elements with ” RE ” (or ” Xt “) said.

② product name, use, smelting and pouring methods, etc., generally using the abbreviated letters of Hanyu Pinyin, see table.

③ steel in the main chemical element content ( % ) using Arabic numerals.

Table: GB standard steel number used in the abbreviated letters and their meanings

Translated with www.DeepL.com/Translator (free version)

Our Steel Number Expression Method

Name

Chinese Character

Symbol

Font

Position

Yield point

Yield

Q

Capitalization

Head

Boiling stee

boiling

F

Capitalization

tail

Semi-sedated steel

semi

b

lowercase

tail

Calming steel

town

Z

Capitalization

tail

Special sedation steel

special town

TZ

Capitalization

tail

Oxygen converter (steel)

Oxygen

Y

Capitalization

Alkaline air converter (steel)

Alkaline

J

Capitalization

Free-cutting steel

easy

Y

Capitalization

Head

Carbon tool steel

Carbon

T

Capitalization

Head

Rolling bearing steel

Rolling

G

Capitalization

Head

Steel for welding rod

Weld

H

Capitalization

Head

High grade (high quality steel)

High

A

Capitalization

tail

Special grade

Special

E

Capitalization

tail

riveted screw steel

riveted screw

ML

Capitalization

Head

Anchor chain steel

Anchor

M

Capitalization

Head

Mining Steel

mining

K

Capitalization

tail

Steel for automobile beams

beam

L

Capitalization

tail

Steel for pressure vessel

capacity

R

Capitalization

tail

Steel for multi-layer or high-pressure vessels

high level

gc

lowercase

tail

Cast steel

Cast steel

ZG

Capitalization

Head

Cast steel for rolls

Casting rolls

ZU

Capitalization

Head

Steel for Geological Drilling Tubes

Geological

DZ

Capitalization

Head

Hot rolled silicon steel for electrical engineering

Electrothermal

DR

Capitalization

Head

Cold-rolled non-oriented silicon steel for electrical engineering

Electroless

DW

Capitalization

Head

Cold-rolled oriented silicon steel for electrotechnical use

Electric taking

DQ

Capitalization

Head

Pure iron for electrotechnical use

Electric iron

DT

Capitalization

Head

Super

Super

C

Capitalization

tail

Marine Steel

Ship

C

Capitalization

tail

Bridge steel

Bridge

q

lowercase

tail

Boiler steel

pot

g

lowercase

tail

Steel rail steel

rail

U

lowercase

Head

Precision Alloy

Precision

J

Capitalization

Corrosion resistant alloys

Corrosion resistant

NS

Capitalization

Head

Deformation high temperature alloys

High Hop

GH

Capitalization

Head

Casting high temperature alloys

 

K

Capitalization

Head

B. The classification of our steel number representation description

1 . Carbon structural steel

① is composed of Q + number + quality grade symbol + deoxidation method symbol. Its steel number is crowned with “Q”, representing the yield point of the steel, followed by a number indicating the value of the yield point, the unit is MPa For example, Q235 means the yield point (σ s) for 235 MPa of carbon structural steel.

② If necessary, the steel number can be marked after the symbol indicating the quality grade and deoxidation method. Quality grade symbols are A, B, C, D. Deoxidation method symbols: F boiling steel; b indicates semi-sedated steel: Z indicates sedated steel; TZ indicates special sedated steel, sedated steel may not be marked symbols, that is

Both Z and TZ may be left unmarked. For example, Q235-AF indicates A grade boiling steel.

③ special purpose carbon steel, such as bridge steel, marine steel, etc., basically using the carbon structural steel, but in the steel number at the end of the additional letters to indicate the purpose.

2 . High-quality carbon structural steel

① two numbers at the beginning of the steel number indicates the carbon content of the steel, to the average carbon content of a few ten thousandths, for example, the average carbon content of 0.45% of the steel, steel number ” 45 “, it is not a sequential number, so can not be read as 45 steel.

② high quality carbon structural steel with high manganese content, the manganese element should be marked out, such as 50Mn.

③ boiling steel, semi-sedimentation steel and special-purpose high-quality carbon structural steel should be specially marked at the end of the steel number, for example, the average carbon content of 0.1% of the semi-sedimentation steel, the steel number 10b.

Translated with www.DeepL.com/Translator (free version)

3 . Carbon tool steel

① steel number crowned with ” T “, so as not to mix with other steel types.

② steel number in the number indicates the carbon content, to the average carbon content of a few thousandths. For example, “T 8” means the average carbon content of 0.8%.

③ manganese content is higher, in the steel number at the end of the label ” Mn “, such as ” T8Mn “.

④ senior quality carbon tool steel phosphorus, sulfur content, than the general quality carbon tool steel low, in the steel number at the end of the letter ” A “, to show the difference, such as ” T8MnA “.

4 . Free-cutting steel

① steel number crowned with ” Y “, to distinguish from high-quality carbon structural steel.

② the letter “Y” after the number indicates the carbon content, to the average carbon content of a few ten thousandths, such as the average carbon content of 0.3% of the free-cutting steel, the steel number for “Y 30”.

③ manganese content is higher, also marked in the steel number after the “Mn”, such as “Y40Mn”.

5 . Alloy structural steel

① two numbers at the beginning of the steel number indicates the carbon content of the steel, to the average carbon content of a few ten thousandths, such as 40Cr.

② steel in the main alloying elements, in addition to individual micro-alloy elements, generally expressed as a few percent. When the average alloy content < 1.5%, the steel number is generally marked only the element symbols, and not marked content, but in special cases easily confused, in the element symbols can also be marked with the number ” 1 “, such as steel number ” 12CrMoV ” and “12Cr1MoV”, the former chromium content of 0.4-0.6%, the latter is 0.9-1.2%, the rest of the composition of all the same. When the average content of alloying elements ≥ 1.5%, ≥ 2.5%, ≥ 3.5% ……, the content should be marked after the element symbol, can be expressed accordingly as 2, 3, 4 …… and so on. For example, 18Cr2Ni4WA.

③ steel in the vanadium V, titanium Ti, aluminum AL, boron B, rare earth RE and other alloying elements, are micro-alloying elements, although the content is very low, but still should be marked in the steel number. For example, in 20MnVB steel. Vanadium is 0.07-0.12%, boron is 0.001-0.005%.

④ Advanced quality steel should be added at the end of the steel number ” A “, to distinguish it from the general quality steel.

⑤ special purpose of the alloy structural steel, steel number crowned (or suffix) on behalf of the use of the steel symbol. For example, 30CrMnSi steel for riveting screw, the steel number is expressed as ML30CrMnSi.

6 . Low-alloy high-strength steel

① steel number of the method of expression, basically the same as the alloy structural steel.

② low alloy high-strength steel for professional use, should be marked at the end of the steel number. For example, 16Mn steel, special steel for bridges for “16Mnq”, special steel for automobile girders for “16MnL”, special steel for pressure vessels for “16MnR “.

7 . Spring steel

Spring steel according to the chemical composition can be divided into two categories of carbon spring steel and alloy spring steel, the steel number representation, the former is basically the same as high-quality carbon structural steel, the latter is basically the same as alloy structural steel.

8 . Rolling bearing steel

① steel number crowned with the letter ” G “, said rolling bearing steel class.

② high carbon chromium bearing steel steel number of the carbon content is not marked, chromium content to a few thousandths said. For example, GCr15. Carburized bearing steel steel number, basically the same as the alloy structural steel.

9 . Alloy tool steel and high-speed tool steel

① alloy tool steel steel grade average carbon content ≥ 1.0%, not marked carbon content; when the average carbon content < 1.0%, expressed in parts per thousand. For example, Cr12, CrWMn, 9SiCr, 3Cr2W8V.

② steel alloying elements in the content of the method of expression, basically the same as the alloy structural steel. But the chromium content of the lower alloy tool steel grades, the
chromium content to a few thousandths, and in the content of the number before adding ” 0 “, in order to distinguish it from the general elemental content by a few percent of the method. For example, Cr06.

③ high-speed tool steel steel number is generally not marked out of carbon content, only marked out of the average content of various alloying elements a few percent. For example, the steel number of tungsten high-speed steel is expressed as ” W18Cr4V “. Steel number crowned with the letter “C”, that its carbon content is higher than the general steel number not crowned with “C”.

10 . Stainless steel and heat-resistant steel

① steel number in the carbon content in parts per thousand. For example, the average carbon content of “2Cr 13” steel is 0.2%; if the carbon content of steel ≤ 0.03% or ≤ 0.08%, the steel number before the title of “00” and “0”, respectively. expressed, such as 00Cr17Ni14Mo2, 0Cr18 Ni9, etc..

② the main alloying elements in steel to a few percent, while titanium, niobium, zirconium, nitrogen ……, etc. are marked according to the above-mentioned alloy structural steel on the micro-alloy elements.

11 . Welding rod steel

It is crowned with the letter ” H ” before the steel number, to distinguish it from other steel types. For example, stainless steel welding wire for ” H2Cr 13 “, can be distinguished from stainless steel ” 2Cr 13 “.

12 . Electrical silicon steel

① Steel number consists of letters and numbers. Steel number head letters DR means hot-rolled silicon steel for electricians, DW means cold-rolled non-oriented silicon steel for electricians, DQ means cold-rolled oriented silicon steel for electricians.

②The number after the letter indicates the iron loss value (W/kg) of 100 times.

③ steel number with the letter “G” at the end, said in the high frequency test; not add “G”, said in the frequency of 50 waves under the test.

For example, the steel number DW470 indicates that the maximum value of iron loss per unit weight of electrical cold-rolled non-oriented silicon steel products at a frequency of 50 Hz is 4.7W/kg.

13 . Pure iron for electrical use

① Its grade consists of the letters “DT” and numbers, “DT” indicates pure iron for electrician, and the numbers indicate the sequential numbers of different grades, such as DT3.

② The letters added after the numbers indicate electromagnetic properties: A – senior, E – special, C – super, e.g. DT 8A.

C. Part of the old and new steel grade comparison

1, carbon steel new and old standard steel number comparison.

GB700-88 new standard with reference to the adoption of international standards ISO630 “structural steel”, while GB700-79 old standards mainly refer to the former Soviet Union IOCT380, so that the two steel number of the method of expression and the technical requirements specified for each steel number are not the same, now the old and new standard steel number control as follows.

GB700-88 Standard

GB700-79 Standard

Steel number

Technical conditions

Steel number

Technical conditions

Q195

The chemical composition and mechanical properties (σs,σb,δ and cold bending) must be guaranteed regardless of the grade.

For products such as rolled sheets and coils, the guaranteed mechanical properties can be separately specified in the relevant standards according to the product characteristics and usage requirements.

A1

B1

The guaranteed mechanical properties (σs,σb,δ and cold bending) of A1 steel and the guaranteed chemical composition of B1 steel are the same as Q195.

Cold-forming test for A1 steel is an additional guarantee condition

No. 1 steel without special class

Q215

A and B grades, the specified chemical composition and mechanical properties must be guaranteed

Q 215A No impact test

Q215B must be room temperature impact test, with V-notch specimens

A2

C2

A2 steel to ensure the mechanical properties, C2 steel to ensure the chemical composition and mechanical properties, and Q215 steel is basically the same

Q235

A, B, C, D grades, the specified chemical composition and mechanical properties are required to ensure

Q 235A is not impact tested

Q235B must be room temperature impact test, with V-notch specimens

Q 235C, Q235D for important welded structures, the former in 0 O C impact test, the latter in -20 O C impact test, specimens, specimens as above

A3

C3

A3 steel guaranteed mechanical properties, C3 steel guaranteed chemical composition and mechanical properties, and Q235 steel is basically the same

Additional guaranteed impact test at room temperature for A3 steel, with U-notch specimens

C3 steel with additional guaranteed impact test at room temperature or -20 O C, specimen as above

Q255

A and B grades, the specified chemical composition and mechanical properties must be guaranteed

Q 255A without impact test

Q255B shall be subjected to room temperature impact test with V-notch specimens

A4

C4

A4 steel guaranteed mechanical properties, C4 steel guaranteed chemical composition and mechanical properties, and Q255 steel is basically the same

C4 steel additional guaranteed impact test, with U-notch specimens

Q275

Regardless of grade, the specified chemical composition and mechanical properties shall be guaranteed

C5

The guaranteed chemical composition and mechanical properties of C5 steel are essentially the same as those of Q275 steel

2, low-alloy steel is currently using GB/T1591-94 instead of 1591-88, now some of the old and new steel grades against the following.

GB/T1591-94

GB1591-88

Q295

09MnV 09MnNb 12Mn

Q345

12MnV 16Mn 16MnRE

Q390

15MnV 15MnTi 16MnNb

Q420

15MnVN 14MnVTiRE