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Steel grades

Classification system

Steel grades

Classification system

Steel grades are grades used to classify various steels by their composition and physical properties. Steel grades have been developed by a number of standards organizations.

Steel grades standards by country

  • For alloys in general (including steel), unified numbering system (UNS) of ASTM International and the Society of Automotive Engineers (SAE).
  • American steel grades : AISI/SAE steel grades standard
  • British Standards
  • International Organization for Standardization ISO/TS 4949:2016
  • European standards – EN 10027
  • Japanese steel grades : Japanese Industrial Standards (JIS) standard and NK standard
  • Germany steel grades : DIN standard
  • China steel grades : GB standard
  • Czech steel grades : ČSN standard
  • Russia steel grades : GOST standard
  • Spain steel grades : UNE standard
  • France steel grades : AFNOR standard
  • Italy steel grades : UNI standard
  • Sweden steel grades : SIS standard
  • Norway steel grades : DNV standard

Note that an increasing number of national European standards (DIN, AFNOR, UNE, UNI, etc.) and UK standards are being withdrawn and replaced by European Standards (EN). This task is carried out by the Comité Européen de Normalisation (CEN) (European Committee for Standardization).

European standard steel grades

EN 10027-1 steel grade designation system.

European standard steel grade names fall into two categories:

  1. Steel specified by purpose of use and mechanical properties.
  2. Steel specified by chemical composition.

The inclusion of a letter 'G' before the code indicates the steel is specified in the form of a casting.

Category 1: Steel specified by purpose of use and mechanical properties

Basic grade designations for category 1 steels consist of a single letter (designating application) then a number signifying the mechanical property (often yield strength) dictated in the standard for that application designation. For some application designations another letter is included before the property value, this number is used to indicate any special requirements or conditions. These additional letters and values depend entirely on the application of the steel and are specified in the standard and far too numerous to mention here.

The next set of 3 digits gives the steel's minimum yield strength. So S355 has a minimum yield strength of 355 MPa for the smallest thickness range covered by the relevant standard – i.e. EN10025.

Below is a table indicating the most common application codes.

Application symbolMeaningMechanical PropertyDetails
SStructural steelMinimum Yield Strength
PSteel for pressure lines and vesselsMinimum Yield Strength
LSteel for pipe and tubeMinimum Yield Strength
EEngineering steelsMinimum Yield Strength
BSteel for reinforced concreteCharacteristic Yield Case
RSteel for rail useMinimum Yield Case
HHigh Tensile Strength Flat productsMinimum Yield CaseIf followed by T then the given mechanical property is minimum tensile strength
DFlat Products for Cold FormingFollowed by C, D or X and two numbers characterising steel
TTinmill ProductsNominal Yield Case
MElectrical SteelNumber = 100 × specific loss in W/kg

Additional symbols

In addition to the above category codes there are symbols that can be added to the grade code to identify any additional compositional requirements, delivery conditions, mechanical properties, &c. These values depend solely on the type/application code given in the first part of the code and are so numerous as to be impossible to indicate here. Additional symbols are separated from the main code by the plus sign (+).

The most common additional symbols are the impact and temperature codes for structural steels, category 1 - Sxxx.

Impact ResistanceTemperatureImpact
codeTesting
strengthTemperature
codeTesting
temperature
J27 JRRoom temperature
K40 J00 °C
L60 J2-20 °C
3-30 °C
4-40 °C
5-50 °C
6-60 °C

Example : S355J2

Delivery condition codes are also relatively common, the most common being:

CodeCondition
AAnnealed
QTQuenched and tempered
NNormalised
SRStress relieved
CCold worked
UUntreated
GDeoxidated

Example : S355J2+N

Electrical steel

Electrical steel type of product letters (bold are most recent version 2016):

CodeMaximum specific lossType of product
**A**1.5 T @50 Hznon oriented
D (formerly B)"non-alloy semi-finished (not finally annealed)
E"alloy semi-finished (not finally annealed)
**K** (=D+E)"non-alloy and alloy electrical steel sheet/strip in the semi-processed state
N"for normal grain oriented products
**P**1.7 T @50 Hzhigh permeability grain oriented
**S**"conventional grain oriented

Standard per steel name

According to EN 10027-1

ApplicationMechanicaladditional symbolStandard
S235JREN 10025-2
355JREN 10025-2
J0EN 10025-2
J2EN 10025-2
K2EN 10025-2
NEN 10025-3
NLEN 10025-3
450J0EN 10025-2
P265GHEN 10028-2
NBEN 10120
355NHEN 10028-3
MEN 10028-5
ML1EN 10028-5
QEN 10028-6

Category 2: Steel specified by chemical composition

In addition to the descriptive steel grade naming system indicated above, within EN 10027-2 is defined a system for creating unique steel grade numbers. While less descriptive and intuitive than the grand names they are easier to tabulate and use in data processing applications.

The number is in the following format: x.yyzz(zz) Where x is the material type (only 1 is specified so far), yy is the steel group number (specified in EN10027-2) and zz(zz) is a sequential number designated by the certifying body, the number in brackets being unused but reserved for later use.

The steel groups are indicated below:

CodeType**Non-alloy steels****Alloy steels**
00 & 90Basic steels
0x & 9xQuality steels
1xSpecial steels
2xTool steels
3xMiscellaneous steels
4xStainless and heat resistant steels
5x – 8xStructural, pressure vessel and engineering steels
08 & 98Special physical properties
09 & 99Other purpose steels

The current certification body is the VDEh in Düsseldorf, Germany.

Comparisons

Below is a table comparing steel grades from different grading systems.

EN steel number
(Europe)EN steel name
(Europe)ASTM grade
(USA)AISI/SAE grade
(USA)UNS
(USA)DIN
(Germany)BS
(UK)UNI
(Italy)JIS
(Japan)Carbon steelsAlloy steelsStainless steelsTool steels
1.1141
1.0401
1.0453C15D
C18D1010
1018CK15
C15
C16.8040A15
080M15
080A15
EN3BC15
C16
1C15S12C
S15
S15CK
S15C
1.0503
1.1191
1.1193
1.1194C451045C45
CK45
CF45
CQ45060A47
080A46
080M46C45
1C45
C46
C43S45C
S48C
1.0726
1.072735S20
45S201140/114635S20
45S20212M40
En8M
1.0715
1.073611SMn3712159SMn28
9SMn36230M07
En1ACF9SMn28
CF9SMn36SUM 25
SUM 22
1.0718
1.073711SMnPb30
11SMnPb3712L149SMnPb28
9SMnPb36230M07 Leaded
En1B LeadedCF9SMnPb29
CF9SMnPb36SUM 22
SUM 23
SUM 24
1.1555C120UC125WBW1CC120KUSK2
1.7218413025CrMo4
GS-25CrMo4708A30
CDS11025CrMo4 (KB)
30CrMo4SCM 420
SCM 430
SCCrM1
1.7223
1.7225
1.7227
1.356342CrMo44140/414241CrMo4
42CrMo4
42CrMoS4
43CrMo4708M40
708A42
709M40
En19
En19C41CrMo4
38CrMo4 (KB)
G40 CrMo4
42CrMo4SCM 440
SCM 440H
SNB 7
SCM 4M
SCM 4
1.6582
1.656234CrNiMo6434034CrNiMo6
40NiCrMo8-4817M40
En2435NiCrMo6 (KB)
40NiCrMo7 (KB)SNCM 447
SNB24-1-5
1.6543
1.652320NiCrMo2-2862021NiCrMo22
21NiCrMo2805A20
805M2020NiCrMo2SNCM 200 (H)
1.541516Mo3A204 A/B/CK12822
K12320
K12020
K1182015Mo31503-243B
240
24315Mo3
16Mo3STBA12
1.4310X10CrNi18-8301S30100
1.4318X2CrNiN18-7301LN
1.4305X8CrNiS18-9303S30300X10CrNiS18-9303S 31
En58MX10CrNiS18-09SUS 303
1.4301X2CrNi19-11
X2CrNi18-10304S30400X5CrNi18-9
X5CrNi18-10
XCrNi19-9304S 15
304S 16
304S 18
304S 25
En58EX5CrNi18-10SUS 304
SUS 304-CSP
1.4306X2CrNi19-11304LS30403304S 11SUS304L
1.4311X2CrNiN18-10304LNS30453
1.4948X6CrNi18-11304HS30409
1.4303X5CrNi18-12305S30500
1.4401
1.4436X5CrNiMo17-12-2
X5CrNiMo18-14-3url=https://powder.samaterials.com/stainless-steel-powder-301-vs-304-vs-316.htmltitle=Stainless Steel Powder: 301 vs. 304 vs. 316website=Stanford Advanced Materialsaccess-date=Sep 7, 2024}}S31600X5CrNiMo17 12 2
X5CrNiMo17 13 3
X5CrNiMo 19 11
X5CrNiMo 18 11316S 29
316S 31
316S 33
En58JX5CrNiMo17 12
X5CrNiMo17 13
X8CrNiMo17 13SUS 316
SUS316TP
1.4404X2CrNiMo17-12-2316LS31603316S 11SUS316L
1.4406
1.4429X2CrNiMoN17-12-2
X2CrNiMoN17-13-3316LNS31653
1.4462X2CrNiMoN22.5.3S31803X2CrNiMoN22.5.3
1.4571316TiS31635X6CrNiMoTi17-12320S 33
1.4438X2CrNiMo18-15-4317LS31703
1.4541321S32100X6CrNiTi18-10321S 31SUS321
1.4848GX40CrNiSi25-20A351 HK40J94204SEW 595 GX40CrNiSi25-20310C40SCH22
1.4859GX10NiCrSiNb32-20N08151GX10NiCrSiNb32-20
1.4878X12CrNiTi18-9
X8CrNiTi18-10321HS32109
1.4906X7CrNiNb18-10347HS34709
1.4512X6CrTi12409S40900SUH409
410S41000
1.4016430S43000X6Cr17430S 17SUS430
440AS44002
1.4112440BS44003
1.4125[440C](440c)S44004X105CrMo17SUS440C
1.4104430FS44020X14CrMoS17SUS430F
1.4057X17CrNi16-2431 XS43100X16CrNi16431S 29SUS431
1.542316Mo5A335 P14520
4419H
4419K1152216Mo5STPA12
1.771514MoV6-3A335 P2K1154714MoV6-3660STPA20
1.7335
1.733813CrMo4-5
10CrMo5-5A335 P11K11597STPA23
1.7375
1.7380
1.738310CrMo9-10
11CrMo9-10
12CrMo9-10A335 P22K2159017175 10CrMo910STPA24
1.7362
1.7366X11CrMo5
X12CrMo5
12CrMo19-5A335 P5501
502K41545
S50100
S50200STPA25
1.7386X11CrMo9-1
X12CrMo9-1A335 P9503S50400
S50488
K90941STPA26
1.4903X10CrMoVNbN9-1A335 P91K91560X10CrMoVNbN9-1
1.4905
1.4906X11CrMoWVNb9-1-1
X12CrMoWVNbN10-1-1A335 P92K92460X11CrMoWVNb9-1-1
X12CrMoWVNbN10-1-1
1.4539X1NiCrMoCu25-20-5904LN08904
1.4547X1CrNiMoCuN20-18-7S31254
1.4565NIT50S20910
NIT60S21800
1.2363X100CrMoV5A-2T30102X100CrMoV51BA 2X100CrMoV5-1 KUSKD 12
A-3T30103
A-4T30104
A-6T30106
A-7T30107
A-8T30108
A-9T30109
1.2365X32CrMoV3-3
32CrMoV12-28H10T20810X32CrMoV3-3
32CrMoV12-28SKD 7
1.2379X153CrMoV12D-2X153CrMoV12-1BD 2X155CrVMo12-1SKD 11
1.2510O-1100MnCrW4Bo 195MnWCr-5 KU

American Petroleum Institute (API) steel grades

The American Petroleum Institute has a standardized steel grading system for various properties of steel composites.

Color coding

In order to clearly distinguish the steel grade, tubing, casing and its coupling should be painted with color codes respectively. Color bands should be painted on tubing and casing body longer than 600mm to either end. The whole outer-body of the coupling needs to be painted color and then color codes.

Steel GradeCouplingTubular Body
**API Tubing and Casing**H40None
J55all green.one green band
K55all greentwo green bands
N80-1all redone red band
N80-Qall red + one green bandone red band + one green band
L80-1all red + one brown bandone red band + one brown band
L80-9Crcolorless + two yellow bandsone red band + one brown band + two yellow bands
L80-13Crcolorless + one yellow bandone red band + one brown band + one yellow band
C90-1all purpleone purple band
T95-1all silverone silver band
C110all white + two brown bandsone white band + two brown bands
P110all whiteone white band
Q125all orangeone orange band

API 5B and 5CT provide various steel grades and color codes of each grade, with general information of casing and tubing.

References

Notes

Bibliography

References

  1. "EN 10027". European Committee for Standardization.
  2. "EN 10027 Steel Names and their Meaning".
  3. "Designation systems for steels".
  4. (2016). "Handbook of Comparative World Steel Standards, 5th Edition".
  5. "Standards comparison".
  6. Oberg, pp. 411-412.
  7. (16 May 2022). "1045 Steel".
  8. "Stainless Steel Powder: 301 vs. 304 vs. 316".
  9. "Chronifer M-15 X (431 X) steel developed by L. Klein SA".
  10. "AISI A2". Efunda.
  11. "AISI A3". Efunda.
  12. "AISI A4". Efunda.
  13. "AISI A6". Efunda.
  14. "AISI A7". Efunda.
  15. "AISI A8". Efunda.
  16. "AISI A9". Efunda.
  17. "API Steel Grade for Casing & Tubing".
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