Steel grades to classify various steels by their composition and physical properties have been developed by a number of standards organizations.
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 and UK standards are being withdrawn and replaced by European Standards (EN).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 grade names fall into two categories:
The inclusion of a letter 'G' before the code indicates the steel is specified in the form of a casting.
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.[1]
Below is a table indicating the most common application codes.
| Application symbol | Meaning | Mechanical Property | Details | |
|---|---|---|---|---|
| S | Structural steel | |||
| P | Steel for pressure lines and vessels | |||
| L | Steel for pipe and tube | |||
| E | Engineering steels | |||
| B | Steel for reinforced concrete | Characteristic Yield Case | ||
| R | Steel for rail use | Minimum Yield Case | ||
| H | High Tensile Strength Flat products | Minimum Yield Case | If followed by T then the given mechanical property is minimum tensile strength | |
| D | Flat Products for Cold Forming | Followed by C, D or X and two numbers characterising steel | ||
| T | Tinmill Products | Nominal Yield Case | ||
| M | Electrical Steel | Number = 100 × specific loss in W/kgNumber = 100 × nom thick in mm Letter for type of product (A, K, P or S[2]) |
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 Resistance | Temperature | ||
|---|---|---|---|
| Impact code | Testing strength | Temperature code | Testing temperature |
| J | 27 J | R | Room temperature |
| K | 40 J | 0 | 0 °C |
| L | 60 J | 2 | -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:
| Code | Condition | |
|---|---|---|
| A | Annealed | |
| QT | Quenched and tempered | |
| N | Normalised | |
| SR | Stress relieved | |
| C | Cold worked | |
| U | Untreated | |
| G | Deoxidated |
Electrical steel type of product letters (bold are most recent version 2016):
| Code | Maximum specific lossexpressed for magnetic induction | Type of product | |
|---|---|---|---|
| A | 1.5 T @50 Hz | non 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 Hz | high permeability grain oriented | |
| S | " | conventional grain oriented |
According to EN 10027-1
| S | 235 | JR | EN 10025-2 |
| 355 | JR | EN 10025-2 | |
| J0 | EN 10025-2 | ||
| J2 | EN 10025-2 | ||
| K2 | EN 10025-2 | ||
| N | EN 10025-3 | ||
| NL | EN 10025-3 | ||
| 450 | J0 | EN 10025-2 | |
| P | 265 | GH | EN 10028-2 |
| NB | EN 10120 | ||
| 355 | NH | EN 10028-3 | |
| M | EN 10028-5 | ||
| ML1 | EN 10028-5 | ||
| Q | EN 10028-6 |
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:
| Code | Type | |
|---|---|---|
| Non-alloy steels | ||
| 00 & 90 | Basic steels | |
| 0x & 9x | Quality steels | |
| 1x | Special steels | |
| Alloy steels | ||
| 2x | Tool steels | |
| 3x | Miscellaneous steels | |
| 4x | Stainless and heat resistant steels | |
| 5x – 8x | Structural, pressure vessel and engineering steels | |
| 08 & 98 | Special physical properties | |
| 09 & 99 | Other purpose steels | |
The current certification body is the VDEh in Düsseldorf, Germany.
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 steels | |||||||||
| 1.1141 1.0401 1.0453 | C15D C18D | 1010 1018 | CK15 C15 C16.8 | 040A15 080M15 080A15 EN3B | C15 C16 1C15 | S12C S15 S15CK S15C | |||
| 1.0503 1.1191 1.1193 1.1194 | C45 | 1045[6] | C45 CK45 CF45 CQ45 | 060A47 080A46 080M46 | C45 1C45 C46 C43 | S45C S48C | |||
| 1.0726 1.0727 | 35S20 45S20 | 1140/1146 | 35S20 45S20 | 212M40 En8M | |||||
| 1.0715 1.0736 | 11SMn37 | 1215 | 9SMn28 9SMn36 | 230M07 En1A | CF9SMn28 CF9SMn36 | SUM 25 SUM 22 | |||
| 1.0718 1.0737 | 11SMnPb30 11SMnPb37 | 12L14 | 9SMnPb28 9SMnPb36 | 230M07 Leaded En1B Leaded | CF9SMnPb29 CF9SMnPb36 | SUM 22 SUM 23 SUM 24 | |||
| 1.1555 | C120U | C125W | BW1C | C120KU | SK2 | ||||
| Alloy steels | |||||||||
| 1.7218 | 4130 | 25CrMo4 GS-25CrMo4 | 708A30 CDS110 | 25CrMo4 (KB) 30CrMo4 | SCM 420 SCM 430 SCCrM1 | ||||
| 1.7223 1.7225 1.7227 1.3563 | 42CrMo4 | 4140/4142 | 41CrMo4 42CrMo4 42CrMoS4 43CrMo4 | 708M40 708A42 709M40 En19 En19C | 41CrMo4 38CrMo4 (KB) G40 CrMo4 42CrMo4 | SCM 440 SCM 440H SNB 7 SCM 4M SCM 4 | |||
| 1.6582 1.6562 | 34CrNiMo6 | 4340 | 34CrNiMo6 40NiCrMo8-4 | 817M40 En24 | 35NiCrMo6 (KB) 40NiCrMo7 (KB) | SNCM 447 SNB24-1-5 | |||
| 1.6543 1.6523 | 20NiCrMo2-2 | 8620 | 21NiCrMo22 21NiCrMo2 | 805A20 805M20 | 20NiCrMo2 | SNCM 200 (H) | |||
| 1.5415 | 16Mo3 | A204 A/B/C | K12822 K12320 K12020 K11820 | 15Mo3 | 1503-243B 240 243 | 15Mo3 16Mo3 | STBA12 | ||
| Stainless steels | |||||||||
| 1.4310 | X10CrNi18-8 | 301 | S30100 | ||||||
| 1.4318 | X2CrNiN18-7 | 301LN | |||||||
| 1.4305 | X8CrNiS18-9 | 303 | S30300 | X10CrNiS18-9 | 303S 31 En58M | X10CrNiS18-09 | SUS 303 | ||
| 1.4301 | X2CrNi19-11 X2CrNi18-10 | 304 | S30400 | X5CrNi18-9 X5CrNi18-10 XCrNi19-9 | 304S 15 304S 16 304S 18 304S 25 En58E | X5CrNi18-10 | SUS 304 SUS 304-CSP | ||
| 1.4306 | X2CrNi19-11 | 304L | S30403 | 304S 11 | SUS304L | ||||
| 1.4311 | X2CrNiN18-10 | 304LN | S30453 | ||||||
| 1.4948 | X6CrNi18-11 | 304H | S30409 | ||||||
| 1.4303 | X5CrNi18-12 | 305 | S30500 | ||||||
| 1.4401 1.4436 | X5CrNiMo17-12-2 X5CrNiMo18-14-3 | 316 | S31600 | X5CrNiMo17 12 2 X5CrNiMo17 13 3 X5CrNiMo 19 11 X5CrNiMo 18 11 | 316S 29 316S 31 316S 33 En58J | X5CrNiMo17 12 X5CrNiMo17 13 X8CrNiMo17 13 | SUS 316 SUS316TP | ||
| 1.4404 | X2CrNiMo17-12-2 | S31603 | 316S 11 | SUS316L | |||||
| 1.4406 1.4429 | X2CrNiMoN17-12-2 X2CrNiMoN17-13-3 | 316LN | S31653 | ||||||
| 1.4571 | 316Ti | S31635 | X6CrNiMoTi17-12 | 320S 33 | |||||
| 1.4438 | X2CrNiMo18-15-4 | 317L | S31703 | ||||||
| 1.4541 | 321 | S32100 | X6CrNiTi18-10 | 321S 31 | SUS321 | ||||
| 1.4848 | GX40CrNiSi25-20 | A351 HK40 | J94204 | SEW 595 GX40CrNiSi25-20 | 310C40 | SCH22 | |||
| 1.4859 | GX10NiCrSiNb32-20 | N08151 | GX10NiCrSiNb32-20 | ||||||
| 1.4878 | X12CrNiTi18-9 X8CrNiTi18-10 | 321H | S32109 | ||||||
| 1.4906 | X7CrNiNb18-10 | 347H | S34709 | ||||||
| 1.4512 | X6CrTi12 | 409 | S40900 | SUH409 | |||||
| 410 | S41000 | ||||||||
| 1.4016 | 430 | S43000 | X6Cr17 | 430S 17 | SUS430 | ||||
| 440A | S44002 | ||||||||
| 1.4112 | 440B | S44003 | |||||||
| 1.4125 | 440C | S44004 | X105CrMo17 | SUS440C | |||||
| 1.4104 | 430F | S44020 | X14CrMoS17 | SUS430F | |||||
| 1.4057 | X17CrNi16-2 | 431 X[7] | S43100 | X16CrNi16 | 431S 29 | SUS431 | |||
| 1.5423 | 16Mo5 | A335 P1 | 4520 4419H 4419 | K11522 | 16Mo5 | STPA12 | |||
| 1.7715 | 14MoV6-3 | A335 P2 | K11547 | 14MoV6-3 | 660 | STPA20 | |||
| 1.7335 1.7338 | 13CrMo4-5 10CrMo5-5 | A335 P11 | K11597 | STPA23 | |||||
| 1.7375 1.7380 1.7383 | 10CrMo9-10 11CrMo9-10 12CrMo9-10 | A335 P22 | K21590 | 17175 10CrMo910 | STPA24 | ||||
| 1.7362 1.7366 | X11CrMo5 X12CrMo5 12CrMo19-5 | A335 P5 | 501 502 | K41545 S50100 S50200 | STPA25 | ||||
| 1.7386 | X11CrMo9-1 X12CrMo9-1 | A335 P9 | 503 | S50400 S50488 K90941 | STPA26 | ||||
| 1.4903 | X10CrMoVNbN9-1 | A335 P91 | K91560 | X10CrMoVNbN9-1 | |||||
| 1.4905 1.4906 | X11CrMoWVNb9-1-1 X12CrMoWVNbN10-1-1 | A335 P92 | K92460 | X11CrMoWVNb9-1-1 X12CrMoWVNbN10-1-1 | |||||
| 1.4539 | X1NiCrMoCu25-20-5 | 904L | N08904 | ||||||
| 1.4547 | X1CrNiMoCuN20-18-7 | S31254 | |||||||
| 1.4565 | NIT50 | S20910 | |||||||
| NIT60 | S21800 | ||||||||
| Tool steels | |||||||||
| 1.2363 | X100CrMoV5 | A-2 | T30102 | X100CrMoV51 | BA 2 | X100CrMoV5-1 KU | SKD 12 | ||
| A-3 | T30103 | ||||||||
| A-4 | T30104 | ||||||||
| A-6 | T30106 | ||||||||
| A-7 | T30107 | ||||||||
| A-8 | T30108 | ||||||||
| A-9 | T30109 | ||||||||
| 1.2365 | X32CrMoV3-3 32CrMoV12-28 | H10 | T20810 | X32CrMoV3-3 32CrMoV12-28 | SKD 7 | ||||
| 1.2379 | X153CrMoV12 | D-2 | X153CrMoV12-1 | BD 2 | X155CrVMo12-1 | SKD 11 | |||
| 1.2510 | O-1 | 100MnCrW4 | Bo 1 | 95MnWCr-5 KU | |||||
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 Grade | Coupling | Tubular Body | |
|---|---|---|---|
| API Tubing and Casing | H40 | None | None or black band at the manufacturer's option |
| J55 | all green. | one green band | |
| K55 | all green | two green bands | |
| N80-1 | all red | one red band | |
| N80-Q | all red + one green band | one red band + one green band | |
| L80-1 | all red + one brown band | one red band + one brown band | |
| L80-9Cr | colorless + two yellow bands | one red band + one brown band + two yellow bands | |
| L80-13Cr | colorless + one yellow band | one red band + one brown band + one yellow band | |
| C90-1 | all purple | one purple band | |
| T95-1 | all silver | one silver band | |
| C110 | all white + two brown bands | one white band + two brown bands | |
| P110 | all white | one white band | |
| Q125 | all orange | one orange band |