Reading designations
How to read Indian steel designations: IS 1570 (45C8, 40Cr4Mo3), IS 2062 E250 and IS 1786 Fe 500D
Indian steel names follow the letter-symbol code in IS 1762 (Part 1), which the IS 1570 schedules use: 45C8 means about 0.45% carbon, C for carbon steel and about 0.8% manganese, while alloy names such as 40Cr4Mo3 list each element with a multiplied content figure. Steels bought on strength rather than chemistry are named by a minimum strength instead, as in IS 2062 E250 structural steel and IS 1786 Fe 500D reinforcing bar.
- Designation code
- IS 1762 (Part 1):1974, applied in IS 1570 and other Indian steel standards
- Carbon steels
- 100 × C, then C, then 10 × Mn: 45C8 = about 0.45% C and 0.8% Mn
- Alloy factors
- ×4 Cr, Co, Ni, Mn, Si, W; ×10 Al, Be, V, Pb, Cu, Nb, Ti, Ta, Zr, Mo; ×100 P, S, N
- High-alloy steels
- X prefix when total alloying exceeds 10%; element figures are plain percentages (X04Cr19Ni9)
- Strength-named steels
- IS 2062 E250 = minimum yield 250 MPa; IS 1786 Fe 500D = minimum 0.2% proof stress 500 N/mm², D for higher elongation
- Old names
- Pre-1974 names such as C45 and 40Ni2Cr1Mo28 still appear on older drawings
Carbon steels: 45C8 and 40C8
IS 1762 (Part 1) writes an unalloyed steel as three parts: 100 times the average carbon content, the letter C, and 10 times the average manganese content rounded to a whole number. 45C8 therefore means about 0.45% carbon and 0.8% manganese; IS 1570 (Part 2) specifies 0.40–0.50% C and 0.60–0.90% Mn for it.
Before 1979 the same steels had different Indian names, and IS 1570 (Part 2) still prints the old name in brackets: 45C8 was C45, 40C8 was C40, 35C8 was C35Mn75. The old C45 looks like the European name C45, so check which system a drawing uses.
A G at the end means guaranteed hardenability. Free-cutting steels add the free-cutting element (S, Se, Te or Pb) followed by 100 times its content.
Alloy steels: 40Cr4, 40Cr4Mo3 and 40Ni6Cr4Mo3
Low- and medium-alloy steels (total alloying up to 10%) start with 100 times the carbon content. Each alloying element follows in order of decreasing content, with its average percentage multiplied by a factor and rounded. Manganese is written only when it is 1% or more.
The factor is 4 for chromium, cobalt, nickel, manganese, silicon and tungsten; 10 for aluminium, beryllium, vanadium, lead, copper, niobium, titanium, tantalum, zirconium and molybdenum; and 100 for phosphorus, sulphur and nitrogen. The idea matches the European EN 10027-1 factors, though the Indian X threshold is different.
Older Indian names used figures closer to plain percentages, with molybdenum in hundredths. 40Cr1Mo28 is the older style of 40Cr4Mo3, and 40Ni2Cr1Mo28 the older style of the EN24-type steel now written 40Ni6Cr4Mo3.
High-alloy and stainless steels
When total alloying exceeds 10%, the name starts with X. Carbon is still 100 times its percentage, but the element figures are average percentages rounded to whole numbers.
X04Cr19Ni9 is the IS 6911 name for the 304-type austenitic stainless steel: about 0.04% carbon, 19% chromium and 9% nickel. X02Cr19Ni10 is the low-carbon 304L type and X04Cr17Ni12Mo2 the 316 type. Tool steels add T (or XT for high-alloy tool steels).
Strength-named steels: IS 2062 and IS 1786
IS 1762 also names steels bought on mechanical properties: Fe followed by the minimum tensile strength, or FeE followed by the minimum yield stress, in N/mm². Many older Indian structural and plate grades were written this way.
IS 2062:2011 names hot-rolled structural steel by minimum yield stress: E250, E275, E300, E350, E410 up to E650. A sub-quality letter follows. A means no impact test, BR an optional impact test at room temperature, B0 a mandatory impact test at 0 °C and C a mandatory impact test at −20 °C on killed steel. Order by grade and quality together, for example E250 BR.
IS 1786 names high-strength deformed reinforcing bars Fe 415, Fe 500, Fe 550 and Fe 600, where the figure is the minimum 0.2% proof stress or yield stress in N/mm². A D suffix keeps the same strength but adds a higher minimum elongation and lower carbon limits; S grades, added by amendment, carry further requirements.
Worked examples
Each row decodes a designation using IS 1762 (Part 1). Ranges are the limits published in the standard named.
| Designation | Norme | Reading | De quoi s’agit-il |
|---|---|---|---|
| 45C8 | IS 1570 (Part 2) | 45 = 0.45% C (0.40–0.50) · C = carbon steel · 8 = 0.8% Mn (0.60–0.90) | Medium-carbon steel, 1045 / C45 type |
| 40C8 | IS 1570 (Part 2) | 40 = 0.40% C (0.35–0.45) · C · 8 = 0.8% Mn | Closest Indian grade to EN8 / 1040 |
| 40Cr4 | IS 1570 (Part 4) | 40 = 0.40% C · Cr4 = 4 ÷ 4 = 1% Cr (0.90–1.20) | Chromium steel |
| 40Cr4Mo3 | IS 4367 | 40 = 0.40% C · Cr4 = about 1% Cr · Mo3 = 3 ÷ 10 = about 0.3% Mo | Cr-Mo steel of the EN19 type |
| 40Ni6Cr4Mo3 | IS 1570 (Part 4) | 0.40% C · Ni 6 ÷ 4 = 1.5% (1.25–1.75) · Cr 4 ÷ 4 = 1% (0.90–1.30) · Mo 3 ÷ 10 = 0.3% (0.20–0.35) | Ni-Cr-Mo steel of the EN24 / 4340 type |
| X04Cr19Ni9 | IS 6911 | X = high alloy · 04 = 0.04% C · 19% Cr · 9% Ni | 304-type austenitic stainless |
| E250 BR | IS 2062 | E250 = yield ≥250 MPa · BR = impact test optional, at room temperature if required | General structural steel |
| Fe 500D | IS 1786 | Fe 500 = 0.2% proof stress ≥500 N/mm² · D = enhanced minimum elongation | High-strength deformed rebar |
Standards
Governing standards by region
| Region | System | Designation | Norme | Match |
|---|---|---|---|---|
| Inde | Designation code | IS 1762 (Part 1)Letter-symbol code for steel names; reviewed by BIS in 2024. | IS 1762 (Part 1):1974 | Same material |
| IS 1570 schedules | IS 1570 (Parts 2, 4 and 5)Carbon, alloy and stainless wrought steels named to IS 1762. | IS 1570 (Part 2/Sec 1):1979; IS 1570 (Part 4):1988 | Same material | |
| Structural steel | E250, E350 …Grades by minimum yield stress with sub-qualities A, BR, B0, C. | IS 2062:2011 | Same material | |
| Reinforcing bar | Fe 415, Fe 500, Fe 500D …Grades by minimum 0.2% proof stress; D and S categories. | IS 1786:2008 | Same material |
Questions et réponses
Common questions
What does 45C8 mean?
45C8 is an Indian carbon steel named to IS 1762. The 45 is 100 times the average carbon content (about 0.45%), C means carbon steel and the 8 is 10 times the average manganese content (about 0.8%). IS 1570 (Part 2) specifies 0.40–0.50% C and 0.60–0.90% Mn. It was called C45 before 1979.
What is the Indian equivalent of EN8?
The closest IS 1570 grade is 40C8: 0.35–0.45% carbon and 0.60–0.90% manganese. EN8 (080M40) is a British name, so compare the full specification before substituting.
What does E250 mean in IS 2062?
E250 is a structural steel with a minimum yield stress of 250 MPa. The letter after it (A, BR, B0 or C) sets the impact test requirement and deoxidation, so a full order reads, for example, E250 BR.
What does D mean in Fe 500D?
Fe 500 means a minimum 0.2% proof stress or yield stress of 500 N/mm². D marks the category with the same strength but a higher specified minimum elongation and lower carbon limits, for better ductility.
Why do older drawings say 40Ni2Cr1Mo28 or C45?
These are Indian names from before IS 1762 (Part 1):1974 was applied to the IS 1570 schedules. The revised schedules print the old names in brackets. 40Ni2Cr1Mo28 corresponds to today's 40Ni6Cr4Mo3, and C45 to 45C8.
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Related references
References
Sources
- IS 1762 (Part 1):1974 Code for designation of steels, based on letter symbols (BIS, via Public.Resource.Org) — Fe/FeE rule, carbon steel rule, alloy factors, X rule
- IS 1570 (Part 2/Sec 1):1979 Schedules for wrought steels, carbon steels (BIS, via Public.Resource.Org) — 45C8, 40C8 limits and old names in brackets
- IS 1570 (Part 4):1988 Schedules for wrought steels, alloy steels (BIS, via Public.Resource.Org) — 40Cr4, 40Ni6Cr4Mo3 limits; designations revised to IS 1762
- IS 6911:1992 Stainless steel plate, sheet and strip (BIS, via Public.Resource.Org) — X04Cr19Ni9 (304), X02Cr19Ni10 (304L), X04Cr17Ni12Mo2 (316)
- IS 2062:2011 Hot rolled medium and high tensile structural steel (BIS, via Public.Resource.Org) — Grade designation by minimum yield stress; sub-qualities A, BR, B0, C
- IS 1786:2008 grades of reinforcement (Infralens summary) — Fe figure = minimum 0.2% proof stress; D and S categories
- 40Cr4Mo3 (India / IS) (Total Materia) — Listed under IS 4367
- IS 40Ni2Cr1Mo28 (Total Materia) — Older Indian name, IS 4368:1967
Values summarize published limits and typical data. The governing standard and the current edition control; check them before specifying.