Steel Grades — Family Index
Encyclopedic discovery layer for the steel designations engineers actually meet in drawings, mill certificates, and specs. Each row is a one-line characterisation: composition class, indicative mechanical numbers, archetypal use, and how it weldsor heat-treats. For depth on metallurgy and heat treatment see [[Engineering/materials-steel]]; for structural-design context see [[Engineering/steel-design]] and [[Engineering/steel-connection-design]].
1. At a glance — designation systems
Five systems dominate global commerce, each with its own logic:
| System | Region | Logic | Example |
|---|---|---|---|
| AISI / SAE | US, legacy global | Composition-based, 4-digit | 1018, 4140, 8620 |
| ASTM | US, current dominant | Function-based, spec number | A36, A572 Gr.50, A992 |
| UNS | US, unified | Letter+5-digit, cross-references AISI/ASTM | G10180 (=AISI 1018), K11597 (=A36) |
| EN 10027 | Europe | Mixed: structural (S), pressure (P), engineering (E) + property OR composition | S355J2, P265GH, 42CrMo4 |
| JIS | Japan | G-series spec + letters | SS400, S45C, SCM440 |
| GB/T | China | Q + yield-MPa (structural), composition codes elsewhere | Q235, Q355, 45# |
Composition vs property based. AISI/SAE and EN composition-codes (42CrMo4) tell you what is in it. ASTM, EN structural (S355), JIS SS, GB Q-grades tell you what it must do (yield, tensile, impact). Mills are free to meet a property spec with any composition that hits the chemistry envelope. A steel can carry both designations on its mill cert — e.g. an A992 wide-flange is also broadly a 1020-ish mild steel by chemistry.
Reading a mill test report (MTR). Every shipped lot of steel arrives with an MTR carrying: heat number (traceability), specification(s) certified-to, chemistry (ladle and product analyses for C, Mn, P, S, Si, plus alloys), mechanical results (yield, UTS, elongation, RA, Charpy temp/energy), and product-form data (thickness, width, dimensions). The MTR is the legal proof of conformance — keep one with every bridge, pressure-vessel, or aerospace lot.
2. Designation-system primer
AISI/SAE 4-digit codes
- First two digits = alloy family.
- 10xx — plain carbon
- 11xx — resulphurised (free-machining)
- 12xx — resulphurised + rephosphorised
- 13xx — Mn (1.75% Mn)
- 15xx — high-Mn plain carbon
- 23xx, 25xx — Ni
- 31xx, 33xx — Ni-Cr (legacy)
- 40xx, 44xx — Mo
- 41xx — Cr-Mo
- 43xx — Ni-Cr-Mo
- 46xx, 48xx — Ni-Mo
- 50xx, 51xx, 52xx — Cr
- 61xx — Cr-V
- 86xx, 87xx, 88xx — Ni-Cr-Mo (lean)
- 92xx — Si-Mn
- 93xx — Ni-Cr-Mo
- Last two digits ≈ carbon content × 100. AISI 1045 ≈ 0.45 wt% C; 4140 ≈ 0.40 wt% C with Cr-Mo; 8620 ≈ 0.20 wt% C, low alloy.
- A leading “H” suffix (e.g. 4140H) means hardenability is to a guaranteed band rather than chemistry alone.
EN 10027 naming
- S = structural (S235, S275, S355, S460) — number is the minimum yield in MPa for the thinnest range.
- P = pressure vessel (P265GH, P355NL2).
- E = engineering / machine (E295, E335, E360) — number is minimum yield.
- L = pipeline (L290, L360, L450 — number ≈ SMYS in MPa, equivalent to API 5L X-grades).
- B = reinforcing bar (B500B).
- Suffix letters: JR/J0/J2/K2 = Charpy impact temperature/energy class; N/M = normalised/thermomechanical; W = weathering; Q = quench+temper.
- Composition codes: a number = mean C×100, then alloy letters (Cr, Mn, Mo, Ni, V) with their content × 4, 10, 100 depending on element. 42CrMo4 ≈ 0.42 %C, 1.0 %Cr.
ASTM
- Letter “A” + spec number. Spec defines product form and mechanical requirements; multiple grades within one spec (A572 has Gr. 42, 50, 55, 60, 65).
- Function-oriented: A36 = general structural; A53 = pipe; A106 = seamless pressure pipe; A516 = pressure-vessel plate; A992 = W-shape beams; A1018/A1011 = hot-rolled sheet/coil.
Equivalence table — the most-asked rosetta
| Application | AISI/SAE | ASTM | EN | JIS | GB |
|---|---|---|---|---|---|
| Mild plate | 1018-ish | A36 | S235JR / S275JR | SS400 | Q235 |
| Structural plate, 50 ksi | 1020+V-Nb | A572 Gr.50 | S355JR | SM490 | Q355 |
| Wide-flange beam | — | A992 | S355J0/J2 | SM490YB | Q355B |
| Cr-Mo shaft | 4140 | A322 (4140) | 42CrMo4 | SCM440 | 42CrMo |
| Aerospace tube | 4130 | AMS 6346 | 25CrMo4 | SCM430 | 30CrMo |
| Case-hardening gear | 8620 | A322 (8620) | 21NiCrMo2 | SNCM220 | 20CrNiMo |
| Bearing race | 52100 | A295 | 100Cr6 | SUJ2 | GCr15 |
3. Carbon steels
Plain carbon steels (AISI 10xx, EN C-grades, JIS S-C, GB -grades): the workhorse family — ~ 0.05 to 1.0 % carbon, ~ 0.30 to 0.90 % Mn, low residuals. Mechanicals scale almost linearly with carbon up to the eutectoid (0.77 %).
Low-carbon (≤ 0.25 %C) — formable, weldable, low strength
| AISI | C % | Mn % | Yield (MPa / ksi) | UTS (MPa / ksi) | Typical use | Weldability |
|---|---|---|---|---|---|---|
| 1006 | 0.06 | 0.35 | 165 / 24 | 295 / 43 | Drawn wire, deep-draw sheet | Excellent |
| 1008 | 0.08 | 0.40 | 170 / 25 | 305 / 44 | Cold-form sheet, panels | Excellent |
| 1010 | 0.10 | 0.40 | 180 / 26 | 325 / 47 | Cold-headed fasteners, sheet | Excellent |
| 1018 | 0.18 | 0.75 | 370 / 54 | 440 / 64 | Shafts, pins, machined parts | Excellent |
| 1020 | 0.20 | 0.45 | 350 / 51 | 420 / 61 | Tube, general-purpose plate | Excellent |
| 1022 | 0.22 | 0.85 | 380 / 55 | 475 / 69 | Carburised gears, screws | Excellent |
| 1025 | 0.25 | 0.45 | 370 / 54 | 440 / 64 | Forgings, low-stress shafts | Good |
EN equivalents: C10E, C15E, C22E (where the trailing “E” or “R” denotes max-P,S limits). JIS: S10C through S25C. GB: 10#, 20#, 25#.
Medium-carbon (0.25 – 0.55 %C) — heat-treatable, machinable, moderate strength
| AISI | C % | Mn % | Yield, normalised (MPa / ksi) | UTS, normalised | Typical use | Weldability |
|---|---|---|---|---|---|---|
| 1035 | 0.35 | 0.75 | 380 / 55 | 585 / 85 | Connecting rods | Fair (pre-heat ≥ 150 °C) |
| 1040 | 0.40 | 0.75 | 415 / 60 | 620 / 90 | Shafts, axles, gears | Fair |
| 1045 | 0.45 | 0.75 | 450 / 65 | 690 / 100 | Crankshafts, machine keys, sprockets | Fair |
| 1050 | 0.50 | 0.85 | 495 / 72 | 725 / 105 | Larger machine parts, springs | Difficult |
EN: C35E, C40E, C45E, C50E. JIS: S35C – S50C. GB: 35# – 50#. C45 / 1045 is the benchmark mid-carbon stock for general machining.
High-carbon (0.55 – 1.0 %C) — high hardness, low ductility, springs and edges
| AISI | C % | Mn % | UTS, oil-quenched/tempered | Typical use | Weldability |
|---|---|---|---|---|---|
| 1060 | 0.60 | 0.75 | 950 / 138 | Springs, hand tools | Poor |
| 1070 | 0.70 | 0.75 | 1030 / 149 | Music wire, springs | Poor |
| 1080 | 0.80 | 0.75 | 1100 / 160 | Music wire, knife blades | Poor |
| 1095 | 0.95 | 0.40 | 1170 / 170 | High-end carbon-steel blades, chisels | Very poor (avoid) |
Free-machining (11xx, 12xx)
Add 0.08 – 0.33 %S as MnS stringers (1117, 1141, 1144, 1215), occasionally with Pb (12L14 — leaded). Pay-off: 30 – 50 % faster cutting, better chip break. Trade-off: anisotropic toughness, poor weldability, sulfur banding visible in macro-etch.
| AISI | C % | Mn % | S % | Pb % | Use |
|---|---|---|---|---|---|
| 1117 | 0.17 | 1.20 | 0.10 | — | Machined shafts, screws |
| 1141 | 0.41 | 1.45 | 0.10 | — | Auto-shop bar stock, studs |
| 1144 | 0.44 | 1.50 | 0.27 | — | Stressproof (cold-drawn, stress-relieved) — high yield without heat treat |
| 1215 | 0.09 | 1.00 | 0.30 | — | Screw-machine work, fittings |
| 12L14 | 0.15 | 1.00 | 0.30 | 0.30 | Highest machinability; lead being phased out in EU under REACH |
Structural-plate carbon grades
- A36 — 250 MPa yield, 400-550 MPa UTS, max 0.26 %C (thin) to 0.27 %C (thick). Generic structural plate from 1960s onward, weldable with low-H electrodes.
- A572 Gr.50 — 345 MPa yield, 450 MPa UTS, micro-alloyed (V or Nb ≤ 0.15 %). Today the default for new buildings, bridges, sign poles. See
[[Engineering/steel-design]]. - A992 — wide-flange-beam grade since 1998 (replaced A36 for W-shapes); 345-450 MPa yield, max yield ratio ≤ 0.85 (for seismic).
- A1011 / A1018 — hot-rolled sheet (≤ 6 mm) / hot-rolled plate (auto, equipment). Designations by grade: CS (commercial), DS (drawing), SS (structural), HSLAS, HSLAS-F.
4. Alloy steels (AISI 4xxx-9xxx)
Hardenability is the key property: how deep you can get a fully-martensitic structure on quench. Carbon sets maximum hardness; alloy content sets depth of hardening.
| AISI | Composition (nominal) | UTS Q&T (MPa / ksi) | HRC range | Typical use | Notes |
|---|---|---|---|---|---|
| 4130 | 0.30 C, 0.95 Cr, 0.20 Mo | 670 - 1240 / 97-180 | 30-50 | Aerospace tubing, racing chassis, pressure vessels | Best chrome-moly weld behaviour; OAW or TIG without pre-heat for thin tube |
| 4140 | 0.40 C, 0.95 Cr, 0.20 Mo | 830 - 1400 / 120-200 | 30-55 | Shafts, gears, axles, oil & gas tooling | ”Pre-hard” 28-32 HRC is a stock condition |
| 4145 | 0.45 C, 0.95 Cr, 0.20 Mo | 900 - 1450 | 32-58 | Heavier sections of 4140 use-cases | More C = harder, less weldable |
| 4150 | 0.50 C, 0.95 Cr, 0.20 Mo | 950 - 1500 | 35-60 | Gun barrels (mil-spec), heavy gears | Difficult to weld |
| 4340 | 0.40 C, 1.8 Ni, 0.80 Cr, 0.25 Mo | 1100 - 1800 / 160-260 | 35-55 | Landing gear, crankshafts, large rotors | Deep-hardening to >100 mm; classic ultra-high-strength chassis steel |
| 300M | 0.40 C, 1.8 Ni, 0.80 Cr, 0.40 Mo, 1.6 Si, 0.08 V | up to 1930 / 280 | 53-55 | Landing gear (mod-4340), rocket motor cases | Tempered at 300 °C; HE-sensitive — careful with plating |
| 5140 | 0.40 C, 0.80 Cr | 900 / 130 | 35-50 | Lightly-stressed shafts, leaf springs | Cr only — cheaper than 4140 |
| 5160 | 0.60 C, 0.80 Cr | 1100 / 160 | 50-60 | Leaf springs, coil springs, large knives | Classic spring steel; tough at HRC 56 |
| 6150 | 0.50 C, 0.95 Cr, 0.15 V | 1170 / 170 | 50-58 | Valve springs, torsion bars | V adds grain-refine + secondary hardening |
| 8620 | 0.20 C, 0.55 Ni, 0.50 Cr, 0.20 Mo | core 700 / case 60 HRC | core 25 / case 60 | Case-hardening: pinions, ring gears, transmission parts | Carburise + oil quench; tough core, hard case |
| 8740 | 0.40 C, 0.55 Ni, 0.50 Cr, 0.25 Mo | 1100 / 160 | 35-50 | Aircraft bolts, fasteners | AN/MS aerospace fastener grade |
| 9310 | 0.10 C, 3.25 Ni, 1.2 Cr, 0.12 Mo | core 900 / case 62 HRC | core 30 / case 62 | High-performance carburised gears (helicopter, aero) | Premium case-hardening — deep, tough core |
| 52100 | 1.0 C, 1.4 Cr | through-hardened 60-66 HRC | 60-66 | Bearing races, balls, rollers, knife blanks | High-C bearing steel; vacuum-degassed for premium grades |
Heat-treatment ground rules.
- 41xx, 43xx, 86xx are quench-and-tempered for through-hardening; austenitise 815-870 °C, oil quench, temper 400-650 °C to set hardness.
- 8620, 9310 are carburised (add C to surface at 925 °C in CO/CH₄ atmosphere or in salt), then oil-quenched and low-tempered (~150 °C) to set a hard case.
- 5160, 6150 are typically oil- or polymer-quenched then tempered 425-500 °C for spring temper at HRC 45-50.
- 52100 is austenitised at 845 °C, oil-quenched, sub-zero treated (-70 °C) to convert retained austenite, then tempered at 150-180 °C.
EN equivalents: 25CrMo4 (4130), 42CrMo4 (4140), 34CrNiMo6 / 36NiCrMo16 (4340), 51CrV4 (6150), 16MnCr5 / 20MnCr5 (8620-class case), 100Cr6 (52100). JIS: SCM430 (4130), SCM440 (4140), SNCM439 (4340), SCM420/SNCM220 (case-hardening), SUJ2 (52100).
5. Tool steels
Classified by AISI/SAE letter prefix based on hardening medium and use:
| Type | Letter | Examples | HRC after treatment | Key uses | Notes |
|---|---|---|---|---|---|
| Water-hardening | W | W1, W2 | 58-66 | Cold chisels, axes, woodworking edges | Cheapest; shallow hardening; high C (0.7-1.5 %) |
| Shock-resistant | S | S1, S5, S7 | 54-60 | Impact tools, jackhammer bits, punches | Lower C (0.4-0.55 %); tough |
| Oil-hardening | O | O1, O2, O6, O7 | 57-62 | Knives, gauges, low-volume dies | Stable on quench; classic knife steel |
| Air-hardening | A | A2, A6, A8, A10 | 57-62 | Blanking dies, forming tools, knives | Distortion-free quench; A2 is the mid-shop standard |
| High-C high-Cr | D | D2, D3, D7 | 58-62 | Long-run blanking dies, slitter knives, plastic-mould inserts | 12 % Cr + 1.5 % C; high wear, low toughness; D2 dominant |
| Hot-work | H | H11, H13, H21 | 44-54 | Die-casting dies (Al, Mg), forging dies, mandrels | Resist softening to 540 °C; H13 dominant |
| High-speed | M, T | M2, M4, M42, M50, T1, T15 | 62-68 | Drills, taps, mill cutters | M2 universal; M42 (8 % Co) for harder workpieces; T15 (CPM) for wear |
| Plastic-mould | P | P20, P20+S | 28-34 (pre-hard) | Injection-mould cavities | Sold pre-hardened; no heat treat post-machining |
| Powder-metal cutlery | (CPM) | CPM-S30V, S35VN, S45VN, S90V, M4 | 58-64 | Premium knives | Cr-V-Mo PM steels; fine carbide, excellent edge retention |
Heat-treatment essentials. A2 austenitises ~925 °C, air-cools to RT, tempers twice at 175-200 °C → HRC 60-62. D2 austenitises ~1010 °C, air-cools, tempers 200-525 °C (double-temper to dissolve retained austenite). M2 austenitises 1200-1230 °C, oil or salt quench, triple-temper at 540-565 °C → secondary-hardening peak at HRC 64-65.
Common chemistries.
| Tool steel | C % | Cr % | Mo % | V % | W % | Co % | Notes |
|---|---|---|---|---|---|---|---|
| W1 | 0.7-1.5 | — | — | — | — | — | Simplest carbon tool steel |
| S7 | 0.50 | 3.25 | 1.40 | — | — | — | Best shock resistance among S-series |
| O1 | 0.94 | 0.50 | — | — | 0.50 | — | Classic oil-hardening shop steel |
| A2 | 1.00 | 5.25 | 1.10 | — | — | — | Air-hardening, minimal distortion |
| D2 | 1.50 | 12.0 | 0.95 | 0.90 | — | — | High-Cr cold-work die steel |
| H13 | 0.40 | 5.25 | 1.35 | 1.00 | — | — | Hot-work die-casting and forging dies |
| M2 | 0.85 | 4.0 | 5.0 | 2.0 | 6.0 | — | Universal HSS |
| M42 | 1.10 | 3.75 | 9.5 | 1.15 | 1.5 | 8.0 | Cobalt HSS — harder, more red-hard |
| T15 | 1.55 | 4.5 | — | 5.0 | 12.5 | 5.0 | Powder-met super HSS — wear-critical cuts |
| P20 | 0.32 | 1.85 | 0.40 | — | — | — | Pre-hardened mould steel |
| CPM-S30V | 1.45 | 14.0 | 2.0 | 4.0 | — | — | Premium PM stainless cutlery steel |
6. HSLA / weathering / structural
High-strength low-alloy (HSLA) steels add ≤ 0.15 % of micro-alloying elements (V, Nb, Ti) and reduce C to gain yield strength via grain refinement and precipitation, without sacrificing weldability.
| Grade | Yield (MPa / ksi) | UTS | Family | Use | Notes |
|---|---|---|---|---|---|
| A572 Gr.42 | 290 / 42 | 415 / 60 | HSLA-V/Nb | Light structural | Less common now |
| A572 Gr.50 | 345 / 50 | 450 / 65 | HSLA-V/Nb | Building frame default since ~1990 | Replaces A36 in most new design |
| A572 Gr.60 | 415 / 60 | 520 / 75 | HSLA-V/Nb | Heavy plate, sign poles | Pre-heat for thicker welds |
| A572 Gr.65 | 450 / 65 | 550 / 80 | HSLA-V/Nb | Crane booms | Limited supply >50 mm |
| A588 | 345 / 50 | 485 / 70 | Weathering (Cor-Ten A/B) | Bridges, architectural exposed steel | 0.2-0.5 % Cu + Cr + Ni; rust patina seals surface |
| A709 | 250-485 | 400-620 | Bridge — multi-grade | AASHTO bridge steel | Gr.36/50/50W/HPS70W/HPS100W |
| A992 | 345-450 / 50-65 | 450 / 65 min | WF beam | All hot-rolled W-shapes (US) | Yield ratio ≤ 0.85 |
| A913 | 345-690 / 50-100 | varies | QST shape | Heavy seismic columns | Quenched-and-self-tempered |
| A514 (T-1) | 690 / 100 | 760-895 / 110-130 | Q&T plate | Mining buckets, crane booms, pressure vessels | Pre-heat mandatory; controlled cooling weld |
| A517 | 690 / 100 | 795-930 / 115-135 | Q&T pressure plate | Heavy pressure vessels | Sister spec to A514 |
| A656 | 345-552 | varies | Hot-rolled high-yield | Truck frames, equipment | |
| A1011 HSLAS-F | 345-550 | varies | Hot-rolled sheet | Auto chassis, equipment | Improved formability |
EN structural (10025-2/3/4): S235 = A36 equivalent; S275, S355, S420, S460 are the standard rungs; suffixes JR (impact 27 J at +20 °C), J0 (at 0), J2 (at -20), K2 (at -20, 40 J), N (normalised), NL (low-temp normalised), M/ML (thermo-mech).
EN weathering: S355J0W, S355J2W (Cor-Ten B equivalents).
7. Cast irons and cast steels
Cast irons differ from steels by carbon: ≥ 2 % C, usually 3-4 %, with Si 1-3 %. Microstructure depends on cooling rate and inoculation.
Cast irons
| Type | Spec / Class | C % | Si % | UTS (MPa / ksi) | Hardness | Use |
|---|---|---|---|---|---|---|
| Gray iron | ASTM A48 Cl.20 / 30 / 40 / 60 | 3.0-3.5 | 2.0-2.5 | 140-415 / 20-60 | 150-260 HB | Engine blocks, machine bases, brake rotors |
| Ductile (SG, nodular) | ASTM A536 60-40-18 / 65-45-12 / 80-55-06 / 100-70-03 / 120-90-02 | 3.4-3.8 | 2.0-2.8 | 415-825 / 60-120 | 140-300 HB | Crankshafts, pipe, gears, manhole covers |
| White iron | — | 2.5-3.5 | 0.5-1.5 | 275 / 40 | 350-550 HB | Wear plate, mill liners; brittle |
| Malleable | ASTM A47 (ferritic), A220 (pearlitic) | 2.2-2.9 | 1.0-1.8 | 345-585 / 50-85 | 130-300 HB | Pipe fittings, small castings; mostly displaced by ductile |
| Austempered ductile (ADI) | ASTM A897 Gr.1 to 5 | 3.4-3.8 | 2.2-2.8 | 860-1600 / 125-230 | 269-477 HB | Heavy gears, crankshafts, suspension; austempered (salt-bath quench → bainite/ausferrite) |
| Compacted graphite (CGI) | ISO 16112 GJV | 3.5-3.8 | 2.1-2.4 | 300-500 / 45-70 | 140-260 HB | Modern truck/diesel engine blocks (Ford 6.7 L Power-Stroke, F1) |
A48 class numbers are the minimum UTS in ksi. A536 65-45-12 reads “65 ksi UTS, 45 ksi yield, 12 % elongation”.
Cast steels
| Spec | Grade | Yield (MPa / ksi) | UTS | Equivalent wrought | Use |
|---|---|---|---|---|---|
| ASTM A27 | 60-30, 65-35, 70-36, 70-40 | 205-275 / 30-40 | 415-485 / 60-70 | A36 | General-purpose carbon castings |
| ASTM A148 | 80-40 through 165-150 | 275-1035 / 40-150 | 550-1170 / 80-170 | 41xx/43xx-class | High-strength structural castings (railway, crane) |
| ASTM A487 | varies | 415-895 | 620-1035 | Q&T low-alloy | Pressure-containing castings |
| ASTM A352 | LCB, LC1-LC4, LC9 | varies | varies | low-temp service | Cryogenic valves and pumps |
8. Specialty and advanced steels
Advanced High-Strength Steels (AHSS) — automotive
Designed for crashworthiness + light-weighting. Designations roughly “type-YS/UTS” in MPa.
| Family | Examples | Yield (MPa) | UTS (MPa) | Mechanism | Use |
|---|---|---|---|---|---|
| Dual-Phase (DP) | DP590, DP780, DP980, DP1180 | 340-900 | 590-1180 | Ferrite + 10-40 % martensite islands | Body structure, B-pillars |
| TRIP | TRIP780, TRIP980 | 400-700 | 780-1000 | Retained austenite → martensite on strain | Energy-absorbing rails |
| TWIP | TWIP980, TWIP1100 | 500-700 | 980-1100 | High-Mn (18-25 %), deformation by twinning, > 50 % elongation | Crash zones — premium |
| Complex Phase (CP) | CP800, CP1000 | 600-850 | 800-1000 | Ferrite-bainite-martensite mix | Bumper beams |
| Martensitic (MS) | MS1300, MS1500 | 950-1250 | 1300-1500 | Fully-martensitic, low-C | Door beams, rocker reinforcements |
| Press-hardened / hot-stamped | 22MnB5 (boron steel) | 950-1250 | 1500-1800 | Boron + Mn; austenitise at 900 °C, form, water-quench in die | B-pillars (almost every modern car) |
| Q&P | QP980, QP1180 | 600-900 | 980-1180 | Quench-and-Partition (austenite stabilised by C partitioning) | Latest body-in-white |
22MnB5 (USIBOR, Al-Si coated) is the workhorse: blank arrives at OEM ferritic-pearlitic (~600 MPa UTS), heats to 900 °C, transferred to die, formed and quenched in one stroke, exits at 1500-1800 MPa UTS as fully-martensitic part. See [[Engineering/materials-steel]] for martensite mechanics.
Maraging steels (18Ni)
Ultra-high-strength precipitation-hardened steels, very-low-carbon (≤ 0.03 %C), ~18 % Ni + Co, Mo, Ti. Solution-treated, then aged 480-510 °C / 3 hr for Ni₃(Mo,Ti) precipitates.
| Grade | UTS (MPa / ksi) | KIC (MPa·√m) | Use |
|---|---|---|---|
| Maraging 200 | 1400 / 200 | 150-180 | Aerospace structure |
| Maraging 250 | 1720 / 250 | 100-130 | Rocket motor cases, landing gear |
| Maraging 300 | 2050 / 300 | 70-100 | Premium tooling, dies, F1 gearbox |
| Maraging 350 | 2400 / 350 | 50-65 | Specialty tooling, centrifuge rotors |
| Maraging C-300 | similar | similar | Variant for additive manufacturing (LPBF) |
Hadfield manganese steel (austenitic Mn steel)
ASTM A128, 1.0-1.4 %C, 11-14 %Mn. Solution-quenched to fully-austenitic, soft (~200 HB). Work-hardens dramatically on impact to ~500 HB. Use: railway crossings (“frogs”), crusher jaws, rock-mill liners.
Other specialties
- Nitriding steels (Nitralloy 135M, EN 41B, 31CrMoV9) — alloyed for nitride formation, surface ≥ 1000 HV after gas nitriding at 500 °C.
- HY-80, HY-100, HY-130 — naval Q&T plate (US Navy submarine hulls); 550-895 MPa yield, controlled low-temp Charpy.
- API 5L X42 – X120 — pipeline steels; numeral = SMYS in ksi. X65, X70 dominate modern long-distance transmission.
- Spring wire grades (ASTM A227, A228 music wire, A229 oil-tempered, A231 Cr-V) — drawn or annealed wire for coil/torsion springs.
9. International cross-reference (25 most-encountered grades)
| Application bucket | AISI / SAE | ASTM | EN | JIS | GB |
|---|---|---|---|---|---|
| Low-C sheet | 1008 | A1008 CS | DC01 / S185 | SPCC | 08F / Q195 |
| Cold-finished bar | 1018 | A108 1018 | C15E | S15C | 15# |
| General structural | — | A36 | S235JR | SS400 | Q235B |
| Building structural | — | A572 Gr.50 | S355JR | SM490A | Q355B |
| Wide-flange | — | A992 | S355J0 | SN490B | Q355GJ |
| Weathering | — | A588 | S355J0W | SMA490AW | Q355NHB |
| Heavy Q&T plate | — | A514 Gr.B | S690QL | WEL-TEN 80 | Q690D |
| Medium-C bar | 1045 | A108 1045 | C45E | S45C | 45# |
| Cr-Mo shaft | 4140 | A322 4140 | 42CrMo4 | SCM440 | 42CrMo |
| Aero tube | 4130 | AMS 6346 | 25CrMo4 | SCM430 | 30CrMo |
| Ni-Cr-Mo HS | 4340 | A322 4340 | 34CrNiMo6 | SNCM439 | 40CrNiMoA |
| Spring | 5160 | A689 5160 | 60Cr3 | SUP9 | 60Si2Mn (similar) |
| Cr-V spring | 6150 | A689 6150 | 51CrV4 | SUP10 | 50CrV4 |
| Case-harden | 8620 | A322 8620 | 21NiCrMo2 | SNCM220 | 20CrNiMo |
| Case, premium | 9310 | A322 9310 | 14NiCrMo13-4 | (≈) SNCM815 | 12Cr2Ni4A |
| Bearing | 52100 | A295 52100 | 100Cr6 | SUJ2 | GCr15 |
| Boiler plate | — | A516 Gr.70 | P355GH | SB450 | 16MnDR / 19Mn6 |
| Pressure-vessel HT | — | A387 Gr.22 | 10CrMo9-10 | SCMV4 | 12Cr2Mo1R |
| Seamless pipe | — | A106 Gr.B | P235GH-TC2 | STPG370 | 20# |
| Line pipe | — | API 5L X65 | L450 | (none direct) | L450 |
| Rebar (60 ksi) | — | A615 Gr.60 | B500B | SD345 | HRB400 |
| W tool | W1 | A686 W1 | C105W2 | SK4 | T8A |
| O tool | O1 | A681 O1 | 100MnCrW4 | SKS3 | 9CrWMn |
| A tool | A2 | A681 A2 | X100CrMoV5 | SKD12 | Cr5Mo1V |
| D tool | D2 | A681 D2 | X153CrMoV12 | SKD11 | Cr12Mo1V1 |
| H tool | H13 | A681 H13 | X40CrMoV5-1 | SKD61 | 4Cr5MoSiV1 |
| HSS | M2 | A600 M2 | HS6-5-2C | SKH51 | W6Mo5Cr4V2 |
| Gray iron | — | A48 Cl.40 | EN-GJL-300 | FC300 | HT300 |
| Ductile iron | — | A536 65-45-12 | EN-GJS-450-10 | FCD450 | QT450-10 |
10. Selection heuristics
Quick rules of thumb — use as starting points, validate against application loads, environment, and supply.
| Need | First-pass pick | Why |
|---|---|---|
| General structural beam/column (building, frame) | A992 (W-shape) or A572 Gr.50 (plate); EN S355J2 | Cheap, weldable, well-stocked, 345 MPa yield |
| Generic plate, non-critical | A36 or S235JR | Universally available |
| Cold-finished shaft, light duty, machinable | 1018 or S15C | Best balance of machinability + weldability + cost |
| Machine shaft, moderate strength | 1045 in normalised, or 4140 pre-hard 28-32 HRC | 4140 if any heat-treat or fatigue concern |
| High-cycle shaft, fatigue-critical | 4340 Q&T to 35-40 HRC | Deep hardening, tough core |
| Gear (carburised, high duty) | 8620 for industrial; 9310 for aero | Tough core + hard case after carburise + quench |
| Spring (leaf or coil) | 5160 for leaf; 6150 or oil-tempered Cr-V wire for coil; A228 music wire for small | Tough at HRC 50-55 |
| Bearing race | 52100 through-hardened to 60-66 HRC; or M50 for aero | Industry standard |
| Hand tool / cold chisel | S7 or 4140 Q&T 50 HRC | S7 if impact-critical |
| Long-run blanking die | D2 at HRC 58-60 | High wear resistance |
| Plastic-injection cavity (pre-hard) | P20 at HRC 30 | Machine without further heat treat |
| Hot-work forging or die-cast die | H13 | Best balance of toughness + thermal fatigue resistance |
| HSS cutting tool | M2 general, M42 harder workpieces, T15 (CPM) wear-critical | M2 covers 80 % of applications |
| Premium folding-knife blade | CPM-S30V / S35VN stainless or O1 / D2 / 1095 carbon | PM stainless for low-maintenance; 1095/O1 if easy resharpen |
| Aerospace tubular (chassis, fuselage) | 4130 | Welds without pre-heat in thin section; tough |
| Aerospace ultra-high-strength | 4340, 300M, maraging 250/300 | 1800-2050 MPa UTS with adequate KIC |
| Boiler / pressure-vessel plate | A516 Gr.70 (warm), A537 (heavy), A387 (high-T Cr-Mo) | ASME Section II compliant |
| Cryogenic vessel | A553 (9 % Ni) or austenitic stainless | 9 %Ni good to -196 °C |
| Bridge, exposed weathering | A588 or A709 50W | Patina protects, no paint |
| Mining wear plate | AR400 / AR500 / AR550 Q&T abrasion-resistant plate; Hadfield for impact | Hadfield for impact-and-abrade |
| Pipeline transmission | API 5L X65 or X70 | High SMYS, low-temp Charpy guaranteed |
| Rebar in seismic frame | A706 Gr.60 (controlled chem) | Better ductility than A615 |
| Auto B-pillar | 22MnB5 (USIBOR) hot-stamped | 1500-1800 MPa UTS at section ~1.5 mm |
10b. Weldability quick chart by carbon equivalent (CE)
Weldability degrades with carbon equivalent. IIW (International Institute of Welding) CE:
CE = C + Mn/6 + (Cr + Mo + V)/5 + (Cu + Ni)/15
| CE range | Weldability | Pre-heat needed | Example grades |
|---|---|---|---|
| ≤ 0.40 | Excellent | None | 1018, A36, S235, S355 (thin), A572 Gr.50 |
| 0.41-0.45 | Good | None to 100 °C for ≥ 25 mm | S355 (thick), A588, A992 |
| 0.46-0.55 | Fair | 100-200 °C | 1045, 4130 (heavy), A514 |
| 0.56-0.65 | Difficult | 200-300 °C + low-H electrodes | 4140, 4340 (Q&T), HY-80 |
| > 0.65 | Severe | > 300 °C + post-weld heat treat | 1095, 52100, tool steels |
For Q&T and HSLA steels, the Pcm (Ito-Bessyo) parameter is preferred — it weights C heavily and is the basis for AWS D1.1 Annex I pre-heat tables.
11. Cross-references
[[Engineering/materials-steel]]— metallurgy, phase diagrams, heat-treatment, microstructure.[[Engineering/steel-design]]— structural-steel design code use of A992 / A572 / S355.[[Engineering/steel-connection-design]]— bolted and welded joints in structural steels.[[Engineering/joining-welding]]— weldability of each family.[[Engineering/Tier3/surface-treatments]]— Q&T cycles, carburising, nitriding, austempering.[[Engineering/fatigue-analysis]]— endurance-limit data by grade.[[Engineering/Tier3/stainless-steels]]— austenitic, ferritic, martensitic, duplex, PH grades.[[Engineering/Tier3/aluminum-alloys]]— counterpart family index for light alloys.[[Engineering/Tier3/fasteners-taxonomy]]— Grade 5/8, A325, A490, ISO property classes.[[Engineering/Tier3/steel-grades]]— extended cast-iron family index.
12. Citations
- ASM International. ASM Handbook, Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys. ASM International, 1990 (and current online edition).
- ASM International. ASM Handbook, Volume 4: Heat Treating. 1991.
- SAE International. SAE J403 — Chemical Compositions of SAE Carbon Steels. Latest revision.
- SAE International. SAE J404 — Chemical Compositions of SAE Alloy Steels.
- ASTM International. Annual Book of ASTM Standards, Vol. 01.01 (Steel — Piping, Tubing, Fittings), 01.04 (Structural Steel), 01.05 (Steel Bars, Forgings, Bearing Steel), 01.06 (Coated Steel Products).
- CEN. EN 10025: Hot-rolled products of structural steels. Parts 1-6.
- CEN. EN 10027-1 and -2: Designation systems for steels.
- CEN. EN 10083: Steels for quenching and tempering. Parts 1-3.
- CEN. EN 10084: Case-hardening steels.
- CEN. EN 10088: Stainless steels.
- Japanese Standards Association. JIS Handbook — Ferrous Materials and Metallurgy. Annual.
- Standardization Administration of China. GB/T 700 Carbon structural steels; GB/T 1591 High-strength low-alloy structural steels; GB/T 3077 Alloy structural steels.
- API. API Specification 5L — Line Pipe. 46th edition.
- AISC. Steel Construction Manual. 16th edition, 2023 — material chapter cross-references.
- Bringas, John E. (ed.). Handbook of Comparative World Steel Standards. ASTM International, 4th edition.
- Krauss, George. Steels: Processing, Structure, and Performance. ASM International, 2nd edition, 2015 — for metallurgical context behind the designations.