1.6358 / X2NiCoMo18-9-5 / Maraging 300 Forging Parts
- 🇪🇺 1.6358 · X2NiCoMo18-9-5
- 🇺🇸 UNS K93120
- 🇺🇸 AMS 6514
- 🇺🇸 ASTM A538 Gr C · A579
- 🛡 MIL-S-46850 Gr 300
- 🌐 Maraging 300 · C300 · 18Ni(300)
- ™ Vascomax® C300 is a Carpenter Technology trademark; we do not sell under that brand
1.6358 is the European Werkstoff number for X2NiCoMo18-9-5, an 18 % nickel cobalt–molybdenum maraging steel known internationally as Maraging 300 / C300 / 18Ni(300) and designated UNS K93120, AMS 6514 and ASTM A538 Grade C. It is soft and freely machinable after solution annealing (≈ 28–32 HRC) and reaches roughly 1,930–2,050 MPa (280–297 ksi) tensile strength after a single low-temperature aging treatment at 480 °C, with almost no distortion and no quench.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, manufacturing 1.6358 forged rings, seamless rolled rings, shafts, round and flat bars, discs, flanges, sleeves, bushings, blocks and tube sheets to customer drawings, in the solution-annealed or aged condition, with EN 10204 3.1 or 3.2 certification and ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388.
Inquiries: 0086-189-2135-9659 · sales@steelforgepieces.com. Send a drawing or dimensions and we reply with price and lead time within 24 hours.
- Werkstoff-Nr.
- 1.6358
- EN name
- X2NiCoMo18-9-5
- UNS
- K93120
- SAE / AMS
- AMS 6514 (bar & forging stock)
- ASTM
- A538 Grade C · A579
- US military
- MIL-S-46850 Gr 300 · MIL-S-13881
- Common names
- Maraging 300 · C300 · Type 300 · 18Ni(300)
- Alloy family
- Fe–18Ni–9Co–5Mo maraging steel
- Strengthening
- Ni₃Ti + Fe₂Mo intermetallics (not carbon)
- Melt route
- VIM + VAR · or EAF + VOD + ESR
- Export status
- Dual-use, ECCN 1C216 (license required)
- Corrosion class
- Not stainless; requires protection
Every 1.6358 order from Jiangyin Jiangnan Metal Co., Ltd. is certified with the ordered designation plus all equivalents the heat also satisfies, so a single certificate clears customs, QA and site inspection in every market.
What is 1.6358 maraging steel?
1.6358 (X2NiCoMo18-9-5 / Maraging 300 / UNS K93120) is an ultra-high-strength, low-carbon iron–nickel martensitic alloy. The name maraging is a contraction of martensitic and aging, and it describes exactly how the alloy works: it transforms to a soft, dislocated iron–nickel martensite on cooling from the solution-annealing temperature, and is then hardened by a separate low-temperature aging step that precipitates fine Ni₃Ti and Fe₂Mo intermetallic particles throughout that martensite.
The critical difference from conventional quenched-and-tempered steels such as AISI 4340 is that 1.6358 gets almost none of its strength from carbon. Carbon is held below 0.03 %, deliberately, because carbides would embrittle the structure. Almost every practical advantage of the grade follows from that:
Air cooling is enough
The martensite transformation in 1.6358 is driven by the 18 % nickel content, not by cooling rate. Sections cool in still air and still transform fully, so there is no quench crack risk and no size-dependent hardenability limit. A 400 mm forged block hardens through as reliably as a 40 mm bar.
Aging at 480 °C only
Hardening happens at 480 °C, far below any transformation temperature, and the part contracts by only about 0.04–0.06 % linear. This is why 1.6358 dominates precision die and tooling applications where a conventional tool steel would move unacceptably.
28–32 HRC before aging
In the solution-annealed condition the alloy is soft enough for conventional carbide machining and even cold forming. All roughing and most finishing is done before aging; only critical features are ground afterwards.
No preheat required
With carbon below 0.03 %, the heat-affected zone cannot form brittle high-carbon martensite. 1.6358 welds without preheat and recovers full strength after a simple re-aging cycle, which is very unusual at 2,000 MPa.
1.6358 is not a stainless steel
1.6358 is occasionally listed as a high-strength stainless steel. It is not one. The specification limits chromium to about 0.50 % maximum as a residual, with no deliberate chromium addition and therefore no passive film. 1.6358 rusts in the same way as carbon and low-alloy steel, and must be oiled, plated, nitrided, painted or otherwise protected. See Corrosion & surface protection for the options.
What is correct, and probably the source of the confusion, is that 1.6358 derives its strength from precipitation of intermetallic compounds rather than from carbon. It shares that hardening mechanism with the precipitation-hardening stainless grades such as 17-4PH, but not their corrosion resistance.
1.6358 is also not a nickel-based superalloy, despite the 18 % nickel content and despite this page sitting in our nickel-alloy category for historical URL reasons. Iron is the balance and the majority element. The correct family description is: an 18 % nickel, cobalt-strengthened, molybdenum- and titanium-bearing maraging steel.
What are the equivalents of 1.6358?
Engineers reach 1.6358 from several directions: a German drawing, an American aerospace specification, a military standard, or a mill trade name. All of the designations below refer to the same nominal chemistry, and Jiangyin Jiangnan Metal Co., Ltd. accepts purchase orders under any of them.
| Standard / body | Designation | Scope & notes |
|---|---|---|
| EN / DIN (Werkstoff) | 1.6358 | European material number, the primary reference on German and EU drawings |
| EN (name) | X2NiCoMo18-9-5 | Descriptive EN name: ≤0.02 %C nominal, 18 Ni, 9 Co, 5 Mo |
| USA · UNS | K93120 | Unified Numbering System. The cleanest generic identifier for a purchase order |
| USA · SAE / AMS | AMS 6514 | Bars, forgings and forging stock. The dominant aerospace specification |
| USA · ASTM | A538 Grade C | Pressure-vessel plates of 18 Ni maraging steel (Gr A = 200, Gr B = 250, Gr C = 300) |
| USA · ASTM | A579 (grade for 18Ni300) | Superstrength alloy steel forgings |
| USA · military | MIL-S-46850 Gr 300 | Also MIL-S-13881; largely superseded but still cited on legacy drawings |
| Generic industry names | Maraging 300 · C300 · Type 300 · 18Ni(300) | Use these on inquiries; they are unencumbered by trademarks |
| Trade names (see notice) | Vascomax® C300 · NiMark® 300 · Durnico® · Marval® 18H | Branded material of the respective producers; the underlying chemistry is 1.6358 |
Vascomax® is a registered trademark of Carpenter Technology Corporation. NiMark®, Durnico® and Marval® are trademarks of their respective owners. Material made by those companies and sold under those brands is theirs. Material produced by Jiangyin Jiangnan Metal Co., Ltd. is correctly described as 1.6358 / X2NiCoMo18-9-5 / UNS K93120 / AMS 6514 / ASTM A538 Grade C: the same generic chemistry, manufactured independently. We are not affiliated with, sponsored by or endorsed by any of the trademark holders named on this page. If your purchase order literally requires "Vascomax C300", only Carpenter can fill it; specify the generic designation instead.
Some supplier catalogues list both 1.6358 and 1.6354 against Maraging 300, and list 1.6359 or 1.6354 against Maraging 250. European mill datasheets and the published literature both give 1.6358 = X2NiCoMo18-9-5 = Maraging 300. If a drawing simply says "1.635x", ask for the EN name or the cobalt and titanium limits before quoting: the difference between the 250 and 300 grades is roughly 200 MPa of tensile strength and a materially different price.
What is the chemical composition of 1.6358?
The 1.6358 / Maraging 300 chemistry below is consistent with AMS 6514, ASTM A538 Grade C and the DIN 1.6358 limits. Note how little of the alloy is doing conventional steel work: there is almost no carbon, manganese or silicon, and the four elements that matter, nickel, cobalt, molybdenum and titanium, are there only to produce the martensite matrix and the intermetallic precipitates that harden it.
| Element | Min | Max | Metallurgical role |
|---|---|---|---|
| Carbon (C) | n/a | 0.03 | Deliberately suppressed. Carbides would embrittle the matrix and consume Ti and Mo |
| Nickel (Ni) | 17.00 | 19.00 | Forms the soft Fe–Ni lath martensite; provides Ni₃Ti precipitation on aging |
| Cobalt (Co) | 8.50 | 9.50 | Lowers Mo solubility in the matrix, forcing finer and denser Fe₂Mo precipitation. The biggest single strength lever |
| Molybdenum (Mo) | 4.60 | 5.20 | Primary precipitation former (Fe₂Mo / Ni₃Mo); also refines the structure |
| Titanium (Ti) | 0.50 | 0.80 | Forms Ni₃Ti; the strongest single contributor per unit added. Higher Ti = higher strength, lower toughness |
| Aluminum (Al) | 0.05 | 0.15 | Deoxidizer plus a secondary precipitation contribution |
| Manganese (Mn) | n/a | 0.10 | Kept low. No hardenability role here, and it degrades toughness |
| Silicon (Si) | n/a | 0.10 | Kept low for the same reason |
| Phosphorus (P) | n/a | 0.010 | Impurity; tight limit protects toughness and resistance to grain-boundary embrittlement |
| Sulfur (S) | n/a | 0.010 | Impurity; tight limit is why VIM/VAR or ESR melting is specified |
| Chromium (Cr) | n/a | 0.50 | Residual only. This is why 1.6358 is not stainless |
| Copper (Cu) | n/a | 0.50 | Residual |
| Boron (B) | ≈ 0.003 (added) | Grain-boundary strengthening micro-addition | |
| Zirconium (Zr) | ≈ 0.01 (added) | Grain refinement and inclusion control | |
| Calcium (Ca) | ≈ 0.05 (added, optional) | Inclusion shape control during melting | |
| Iron (Fe) | Balance | Matrix | |
Limits are per AMS 6514 / ASTM A538 Grade C and the DIN 1.6358 range; individual purchase specifications may narrow them. The certified analysis for your heat is stated on the EN 10204 certificate. Our nominal production aim for 1.6358 is Ni 18.5, Co 9.0, Mo 4.8, Ti 0.60, Al 0.10.
Why the melting route belongs on your purchase order
Because the phosphorus and sulfur limits are 0.010 % and because titanium is easily oxidized, 1.6358 cannot be made in an ordinary open melt. Two routes are used, and they are not interchangeable on a demanding drawing:
VIM + VAR
Vacuum induction melting followed by vacuum arc remelting. Gives the lowest gas content, tightest inclusion rating and the best transverse toughness. Specify this route for AMS 6514 aerospace parts, rotating components and anything with a fracture-mechanics requirement.
EAF + VOD + ESR
Electric arc melting with vacuum oxygen decarburisation, then electroslag remelting. Produces sound, clean material suitable for tooling, dies and general engineering forgings at a lower cost. This is the standard route unless the order says otherwise.
Jiangyin Jiangnan Metal Co., Ltd. supplies 1.6358 from either route. State which one you need. It must appear on the material certificate, and it changes both price and lead time.
What are the mechanical properties of 1.6358?
1.6358 has two completely different mechanical personalities, and confusing them is the most common source of ordering errors on this grade. In the solution-annealed (ST) condition it behaves like a medium-strength engineering steel and machines readily. After aging (STA) at 480 °C it becomes one of the strongest commercially available structural steels.
| Property | Solution annealed (ST) | Solution annealed + aged (STA) |
|---|---|---|
| Tensile strength, Rm | 1,000–1,100 MPa 145–160 ksi | 1,930–2,050 MPa 280–297 ksi |
| Yield strength, Rp0.2 | 760–830 MPa 110–120 ksi | 1,860–1,965 MPa 270–285 ksi |
| Elongation on 4D / 5D, A | 15–18 % | 6–11 % (min 6 %) |
| Reduction of area, Z | 65–75 % | 35–55 % (min 35 %) |
| Hardness | 28–32 HRC (36 HRC max) | 50–56 HRC (typically 52–54) |
| Charpy V-notch impact, RT | 100–160 J | 20–35 J |
| Fracture toughness, KIc | not applicable | ≈ 80–110 MPa·√m |
| Rotating-bending fatigue limit | ≈ 450 MPa | ≈ 600–750 MPa (polished) |
| Typical use of this condition | Delivery, machining, forming, welding | Final service condition |
Values are typical for correctly processed material and are indicative only. Guaranteed minima are those of the specification revision named on the purchase order (AMS 6514, ASTM A538 Grade C, or a customer specification) and are certified per heat on the EN 10204 document. Heavy sections and transverse test orientations show lower ductility and toughness than the longitudinal values above.
Across the maraging family, every increase in strength is bought with toughness. Maraging 250 delivers about 1,760 MPa with roughly 45 J Charpy; 1.6358 delivers about 2,000 MPa with roughly 25 J; Maraging 350 delivers about 2,400 MPa with roughly 12 J. If your part is fatigue- or impact-critical rather than yield-critical, dropping from 1.6358 to Maraging 250 is often the better engineering decision, and it costs less. See the comparison table.
Elevated-temperature behavior
1.6358 holds its room-temperature strength well to about 400 °C, then falls away as the service temperature approaches the 480 °C aging temperature. Prolonged exposure at or above the aging temperature over-ages the Ni₃Ti and Fe₂Mo precipitates: they coarsen, lose coherency with the matrix, and the strength loss is permanent. A conservative continuous-service limit is 400 °C. Short excursions to 450 °C are tolerated. For sustained service above that, move to a nickel-based alloy such as Inconel 718 or Waspaloy.
What are the physical properties of 1.6358?
| Property | Value | Unit / condition |
|---|---|---|
| Density | 8.0 | g/cm³ (0.289 lb/in³); higher than plain steel because of 18 Ni + 9 Co |
| Modulus of elasticity, E | ≈ 190 | GPa (27.5 × 10⁶ psi), room temperature |
| Shear modulus, G | ≈ 72 | GPa |
| Poisson's ratio, ν | ≈ 0.30 | dimensionless |
| Coefficient of thermal expansion | ≈ 10.1 | × 10⁻⁶ /°C, 20–100 °C (annealed; aged slightly lower) |
| Thermal conductivity | ≈ 20 | W/m·K at room temperature |
| Specific heat capacity | ≈ 450 | J/kg·K |
| Electrical resistivity | ≈ 0.60–0.75 | µΩ·m |
| Magnetic response | Ferromagnetic | Martensitic matrix, strongly magnetic in all conditions |
| Melting range | ≈ 1,413–1,453 | °C (solidus / liquidus) |
| Martensite start, Ms | ≈ 200–215 | °C on cooling from solution temperature |
| Austenite start, As | ≈ 510–540 | °C on heating. The ceiling on any re-aging cycle |
| Dimensional change on aging | −0.04 to −0.06 % | Linear contraction ≈ 0.4–0.6 mm per meter |
Physical property values are typical published data for the 18Ni(300) chemistry and are provided for design guidance. They are not certified values and are not guaranteed on the material certificate.
What is the heat treatment for 1.6358?
The heat treatment of 1.6358 is unusually simple: two steps, both air-cooled, no quenchant, no cryogenic step, no tempering ladder. That simplicity is a large part of why the grade gets chosen.
Step 1. Solution annealing (ST)
Heat to 815–830 °C (1,500–1,525 °F), hold approximately one hour per 25 mm of ruling section (minimum one hour), then air cool to below 30 °C. The alloy transforms to soft iron–nickel lath martensite at roughly 200 °C on cooling. Because the transformation is composition-driven rather than rate-driven, the cooling rate is almost irrelevant. A heavy forging air-cools through the transformation just as completely as a thin bar. Resulting hardness is approximately 28–32 HRC.
For heavy forgings, a prior homogenizing soak at 1,120–1,150 °C is often specified to dissolve segregation from the ingot and improve transverse properties. Confirm on the drawing whether this is required, as it must be planned into the route.
Step 2. Aging / maraging (STA)
Heat to 480–485 °C (900 °F), hold 3–6 hours, then air cool. Furnace uniformity of ±5 °C or better matters here: aging is a precipitation reaction and both under-aging and over-aging move the final properties. Three hours is the usual commercial cycle for sections up to about 75 mm; six hours is used for heavy sections and where maximum strength is required.
Nothing in the 1.6358 cycle involves a quench, a phase change during hardening, or a temperature above 830 °C after machining. The hardening step happens at 480 °C, below the stress-relief temperature of most steels. Total dimensional change is about 0.5 mm per meter of contraction, predictable and isotropic. A die that would move several millimeters in a conventional H13 quench-and-temper cycle moves a few hundredths in 1.6358.
1. Over-aging above 510 °C. Reverted austenite begins to form near 510–540 °C. Strength drops and cannot be recovered by further aging, only by a full re-solution anneal, which also undoes your machining tolerances.
2. Soaking too long at solution temperature. Extended time above 830 °C coarsens the austenite grain and can deplete titanium at the surface, giving a soft skin that fails the hardness check. Hold to the schedule.
3. Decarburisation thinking. There is no carbon to lose, but titanium and aluminum do oxidize. Use a protective atmosphere, vacuum or a well-controlled endothermic furnace for the solution step, or leave enough machining stock to remove the affected skin.
How is 1.6358 forged?
1.6358 forges well but has a narrower usable window than carbon or low-alloy steel, and it is unforgiving about finishing temperature. The parameters below are the practice used at Jiangyin Jiangnan Metal Co., Ltd. for open-die forging and seamless ring rolling in this grade.
| Parameter | Value | Reason |
|---|---|---|
| Preheat / soak | 1,150–1,230 °C | Full solution of the alloying elements; soak slowly and uniformly through section |
| Start forging | 1,150–1,200 °C | Working above 1,230 °C risks incipient melting at segregated regions |
| Finish forging | ≥ 900 °C | Below ~900 °C the alloy work-hardens sharply and edge cracking risk rises |
| Total forging reduction | ≥ 4:1 | Breaks down the as-cast/remelted structure; ≥ 6:1 for aerospace grain-flow requirements |
| Reduction per pass | Light, incremental | Heavy single strokes cause internal bursts in this alloy |
| Post-forge cooling | Air cool | Transforms to soft martensite; no quench, no risk of forging cracks |
| Reheats | Minimise | Each reheat costs titanium to oxidation and coarsens the grain |
| Post-forge condition | Solution anneal | Always solution anneal after forging before machining and aging |
Process routes for 1.6358 at our works
Open-die forging
Used for shafts, spindles, blocks, bars, discs and hubs. Multi-step incremental reduction under the hammer or hydraulic press, with intermediate reheats controlled to protect titanium content. This is the primary route for 1.6358 at our factory.
Seamless ring rolling
Upset, punch, then radial–axial roll to final ring section. Produces continuous circumferential grain flow, which is why rolled rings outperform cut-from-plate rings in fatigue. Used for bearing races, coupling rings and pressure-housing rings.
Upset forging
Short, large-cross-section discs, flanges and hubs where the height-to-diameter ratio suits upsetting. Efficient material use on pancake geometries.
Near-net-shape forging
Where geometry allows, profiling the forging to the part shape removes 30–50 % of the machining stock. On a material at this price point, near-net-shape is usually worth the tooling cost even at modest quantities.
1.6358 raw material is expensive: 9 % cobalt, 5 % molybdenum and 18 % nickel are all costly and price-volatile. Buy-to-fly ratio therefore dominates the part cost far more than it does in carbon steel. A ring machined out of solid bar can throw away 70 % of the material; a rolled ring throws away 15–25 %. On a 200 kg finished ring that difference is usually worth more than the entire forging conversion cost. Send us the finished geometry and we will quote both routes so you can see the comparison.
How is 1.6358 machined, welded and ground?
Machining
Machine 1.6358 in the solution-annealed condition (28–32 HRC). Machinability is roughly comparable to a 4340 steel at similar hardness, around 45–55 % of free-machining carbon steel. The alloy is gummy and work-hardens if you let the tool rub, so the rule is positive rake, sharp edges, rigid setup and never dwell.
- Turning (annealed): coated carbide, vc ≈ 50–80 m/min, feed 0.15–0.35 mm/rev, flood coolant.
- Milling (annealed): coated carbide, vc ≈ 40–70 m/min, climb milling, avoid interrupted light cuts.
- Drilling: cobalt HSS or carbide, peck cycles, generous through-coolant.
- After aging (50–56 HRC): grinding, or ceramic and CBN tooling only. Plan the sequence so that only critical features need post-age machining, and allow for the 0.04–0.06 % aging contraction.
Welding
For an ultra-high-strength steel, 1.6358 welds unusually well, because there is no carbon to form brittle martensite in the heat-affected zone.
- Preheat: none required.
- Process: GTAW (TIG) or electron-beam welding; keep heat input low and interpass temperature below about 120 °C.
- Filler: matching maraging composition. Do not substitute a stainless or nickel filler unless the joint is deliberately designed as a soft transition.
- Cleanliness: critical. Titanium and aluminum oxidize readily, so degrease thoroughly and shield generously on both sides.
- Post-weld: re-age at 480 °C for 3–6 h to restore properties in the weld and HAZ. Where the highest uniformity is required, perform a full solution anneal plus age on the completed assembly.
Nitriding and surface engineering
Because the aging temperature (480 °C) and the gas-nitriding temperature (≈455 °C) are so close, 1.6358 can be nitrided and aged in effectively one operation. A 24–48 hour gas nitride produces a 0.10–0.15 mm case at 65–70 HRC over a 52 HRC core. For dies, shafts and wear surfaces that combination is one of the strongest technical reasons to pick this grade.
At 2,000 MPa, 1.6358 is highly susceptible to hydrogen embrittlement. Any process that can charge hydrogen into the part (acid pickling, electroplating, cathodic protection, some paint strippers) must be followed by a bake at 190–220 °C for 4–24 hours, as soon as possible after plating. Avoid acid pickling of aged parts wherever mechanical descaling will do.
Is 1.6358 corrosion resistant? Surface protection requirements
No. With chromium limited to about 0.50 % as a residual, 1.6358 has no passive film and corrodes broadly like a low-alloy steel. It rusts in humid air, in condensation, in fresh water and in seawater. Any 1.6358 part that will see moisture needs a protection strategy specified on the drawing, and any 1.6358 part shipped bare needs vapour-phase inhibitor packaging.
The one favorable corrosion characteristic is behavior under stress: maraging steels are markedly more resistant to stress-corrosion cracking and hydrogen-assisted cracking than quenched-and-tempered steels of equivalent strength, such as 4340 at 1,900 MPa. That resistance, and not general corrosion resistance, is the reason maraging steel gets chosen for highly stressed parts in aggressive service.
| Method | Typical use | Watch out for |
|---|---|---|
| Gas nitriding | Dies, shafts, wear surfaces; combines with the aging cycle | Adds a hard but not corrosion-proof case; still needs oiling |
| Black oxide + oil | Tooling, indoor service, transit protection | Light-duty only; renew periodically |
| Electroless nickel | General corrosion protection on machined parts | Hydrogen bake at 190–220 °C afterwards is mandatory |
| Cadmium / zinc-nickel plating | Aerospace fasteners and fittings | Highest hydrogen risk, so bake immediately. Cadmium is restricted in many markets |
| Paint / epoxy systems | Structural and marine components | Needs a proper blast profile and primer; watch edges and threads |
| VCI packaging | Every bare shipment | Standard on all our 1.6358 export packing |
If your application actually requires both ultra-high strength and inherent corrosion resistance, 1.6358 is the wrong grade. Consider a maraging stainless such as PH 13-8 Mo (≈1,520 MPa with real stainless behavior), or 17-4PH where 1,070–1,310 MPa is sufficient.
1.6358 vs Maraging 250, Maraging 350, 4340 and 17-4PH
The table below places 1.6358 against the two adjacent maraging grades and against the two alloys most often considered as alternatives. Read it as a selection tool: the right answer depends on whether your part is limited by yield strength, by toughness, by corrosion or by cost.
| Property | Maraging 250 | 1.6358 · Maraging 300 | Maraging 350 | AISI 4340 (Q&T) | 17-4PH (H900) |
|---|---|---|---|---|---|
| UNS / W.-Nr. | K92890 · 1.6359 | K93120 · 1.6358 | K93160 | G43400 · 1.6565 | S17400 · 1.4542 |
| Key spec | AMS 6512 | AMS 6514 | AMS 6515 | AMS 6414 | AMS 5643 |
| Cobalt | 7.0–8.5 % | 8.5–9.5 % | 11.5–12.5 % | n/a | n/a |
| Titanium | 0.30–0.50 % | 0.50–0.80 % | 1.30–1.60 % | n/a | n/a |
| UTS | ≈ 1,725–1,800 MPa | ≈ 1,930–2,050 MPa | ≈ 2,400 MPa | ≈ 1,280 MPa | ≈ 1,310 MPa |
| Charpy V, RT | ≈ 40–50 J | ≈ 20–35 J | ≈ 10–15 J | ≈ 20–30 J | ≈ 15–25 J |
| Corrosion resistance | None | None | None | None | Good (≈ 304) |
| Distortion on hardening | Very low | Very low | Very low | High (quench) | Low |
| Weldability | Excellent | Excellent | Good | Poor (preheat + PWHT) | Good |
| Max service temp | ≈ 400 °C | ≈ 400 °C | ≈ 400 °C | ≈ 300 °C | ≈ 315 °C |
| Relative material cost | ≈ 12× | ≈ 15× | ≈ 20× | 1× (baseline) | ≈ 3× |
| Export controlled | Usually not (<1,950 MPa) | Yes (ECCN 1C216) | Yes | No | No |
| Choose it when… | Toughness matters more than the last 200 MPa; also cheaper and usually not license-controlled | You need ~2,000 MPa with low distortion, good weldability and section-independent hardening | Absolute maximum strength, small sections, low impact loading | Cost dominates and 1,280 MPa is enough | You need corrosion resistance and 1,310 MPa is enough |
Relative cost is an order-of-magnitude indication of raw-material cost per kilogram versus AISI 4340, at 2026 cobalt, nickel and molybdenum prices. It is not a quotation and moves with the LME.
If you are replacing a quenched-and-tempered 4340 part that keeps distorting, keeps cracking in the quench, or cannot be welded, then 1.6358 solves all three problems and adds 700 MPa. If you are replacing a 1.6358 part that keeps failing by impact or fatigue rather than by yielding, step down to Maraging 250 instead. Going up to Maraging 350 is rarely the right answer outside small, statically loaded parts.
What 1.6358 forged products does Jiangyin Jiangnan Metal supply?
Jiangyin Jiangnan Metal Co., Ltd. manufactures 1.6358 / X2NiCoMo18-9-5 / Maraging 300 as custom forgings to customer drawings. We do not hold catalogue stock in this grade. Every order is made against a drawing, a heat and an end-use declaration.
- Seamless rolled rings
- Forged rings
- Forged shafts & spindles
- Round bars
- Flat & square bars
- Forged discs & blanks
- Forged flanges
- Sleeves
- Bushings
- Forged blocks
- Tube sheets
- Hollow / trepanned billets
- Gear blanks
- Valve components
- Die blocks & inserts
- Near-net-shape forgings
1.6358 production capability
Jiangyin Jiangnan Metal Co., Ltd. operates open-die forging hammers of 1, 3, 5 and 9 tonnes, a hydraulic press, and 3-meter and 6-meter seamless ring-rolling mills, supported by in-house heat treatment, a mechanical test laboratory, optical emission spectrometry, metallography and non-destructive testing. The works employs 460 people including 9 senior engineers and 32 intermediate engineers.
The figures below are the envelope for 1.6358 specifically. They are deliberately more conservative than our general carbon- and alloy-steel capability, because maraging steel is supplied from remelted ingot in limited sizes and because the tighter cleanliness and testing requirements restrict what can be produced reliably.
If your part falls outside this envelope, send the drawing anyway. We will tell you straight whether we can make it, or whether a different grade or route serves you better.
Process flow for every 1.6358 order
| # | Stage | Control point |
|---|---|---|
| 1 | Order review & export screening | End-use declaration, end-user, destination; license application started before material is bought |
| 2 | Raw material | VIM+VAR or EAF+VOD+ESR ingot; heat number recorded; chemistry verified by OES on arrival |
| 3 | Homogenizing (heavy sections) | 1,120–1,150 °C soak where the drawing requires it |
| 4 | Forging / ring rolling | Start 1,150–1,200 °C, finish ≥ 900 °C, reduction ≥ 4:1, pyrometer log retained |
| 5 | Solution annealing | 815–830 °C, 1 h per 25 mm, air cool; furnace chart recorded |
| 6 | Rough machining | Performed at 28–32 HRC, machining stock to drawing |
| 7 | Ultrasonic examination | EN 10228-3, SEP 1921 or ASTM A388 to the ordered acceptance class |
| 8 | Aging | 480–485 °C, 3–6 h, air cool; furnace uniformity ±5 °C, chart recorded |
| 9 | Mechanical testing | Tensile, hardness, Charpy on prolongations or sacrificial coupons from the same heat and cycle |
| 10 | Final machining / grinding | Critical features only, with aging contraction allowed for |
| 11 | Surface NDT & dimensional | MT or PT, full dimensional report |
| 12 | Certification, VCI packing, shipment | EN 10204 3.1 or 3.2, multi-designation cross-certification, export documents |
Testing, non-destructive examination and certification
Ultrasonic examination
To EN 10228-3 (ferritic and martensitic steel forgings), SEP 1921 or ASTM A388, at the acceptance class stated on your order. Performed after rough machining and before aging, when geometry and attenuation are most favorable.
MT and PT
Magnetic particle examination (1.6358 is strongly ferromagnetic, so MT works well), or liquid penetrant to ASTM E165 / EN ISO 3452 where a non-magnetic method is preferred.
Tensile, impact, hardness
Tensile to ASTM E8 / ISO 6892-1, Charpy V-notch to ASTM E23 / ISO 148-1, hardness in HRC, HB or HV. Test material is taken from prolongations or sacrificial coupons carrying the same heat and the same heat-treatment cycle as the part.
Spectrometry and metallography
Full elemental analysis by optical emission spectrometry against the ordered specification. Grain size to ASTM E112, inclusion rating to ASTM E45 or ISO 4967, macroetch to ASTM E381 for grain flow where required.
EN 10204 3.1 and 3.2
3.1 is our standard mill certificate, issued by our independent quality department. 3.2 adds a third-party witness: Lloyd's, DNV, BV, ABS, TÜV or your nominated body, arranged per order. Certificates list the ordered designation plus every equivalent the heat also satisfies.
Heat and cycle records
Heat number, ingot and billet identity, forging pyrometer log, solution and aging furnace charts, test results and NDT reports are retained and referenced on the certificate. Customer-witnessed hold points can be added at any stage at no charge.
Where is 1.6358 / Maraging 300 used?
1.6358 is specified where a part must carry an extreme load in a small envelope, hold tight tolerance through hardening, or be welded and still reach 2,000 MPa. It is never the cheap answer, so it tends to be specified once the cheaper alternatives have been ruled out.
Die casting, extrusion and forging tooling
Die-casting dies and inserts, aluminum extrusion dies, cold-forging and cold-heading tooling, punches, and plastic-mould inserts. Chosen for the near-zero distortion on hardening and for the nitrided 65–70 HRC case over a tough 52 HRC core.
Landing gear and actuation
Landing-gear components, actuator bodies and rods, airframe fittings and shafts to AMS 6514. Selected for strength-to-weight, weldability and the fracture-toughness advantage over 4340 at equivalent strength.
Shafts, gears and couplings
High-torque transmission shafts, gear blanks, splined shafts, flexible couplings and torsion bars where the shaft diameter is fixed by envelope rather than by strength.
Driveline components
Driveshafts, halfshafts, CV joints, gearbox shafts and ring gears in motorsport and high-performance drivetrains, where mass reduction at constant torque capacity is worth the material cost.
Springs, fasteners and high-load hardware
High-load springs, machine spindles, index tables, precision fasteners and load cells. The very high elastic limit combined with dimensional stability is the attraction.
The 1.2709 connection
The 18Ni300 chemistry is the most widely used metal powder in laser powder-bed fusion, where it carries the tool-steel number 1.2709 (X3NiCoMoTi18-9-5). Customers regularly pair AM-printed features with forged 1.6358 substrates and backing plates from us, because the metallurgy matches.
Export control status of 1.6358: read this before you order
Maraging steel capable of an ultimate tensile strength of 1,950 MPa or more at 20 °C is a listed dual-use good. It appears as ECCN 1C216 on the United States Commerce Control List, under the corresponding entry in Annex I of the EU Dual-Use Regulation, and in the Nuclear Suppliers Group dual-use guidelines. Related entries (for example 1C116) cover maraging steel in forms associated with missile technology. Aged 1.6358 reaches approximately 2,000 MPa and therefore falls above the control threshold.
This is not a formality that suppliers work around. It means that a purchase order for 1.6358 requires end-user and end-use documentation and, in most jurisdictions, an export license before material can move. Licensing adds materially to lead time and must be started at order-review stage, not at shipment.
Jiangyin Jiangnan Metal Co., Ltd. supplies 1.6358 only against complete end-use documentation and the applicable licenses and approvals in both the exporting and importing jurisdictions. To keep your project on schedule, please send the following with your inquiry, not after the order:
- End-user name, registered address and business activity
- Statement of end use: the actual component and the equipment it goes into
- Final destination country, and any re-export or transhipment intentions
- Any applicable import license, end-user certificate or import certificate required in your country
If your application does not actually need 2,000 MPa, ask us about Maraging 250. At roughly 1,725–1,800 MPa it sits below the 1,950 MPa control threshold in most jurisdictions, costs less, has better toughness, and will usually ship considerably faster. For many parts originally specified in 1.6358 out of habit, that is the better commercial and technical answer.
This section is a general description of publicly published control-list entries, provided as commercial guidance. It is not legal advice. Classification and licensing obligations depend on your jurisdiction, the specific end use and the current revision of the relevant regulation. Consult your export-compliance function or a qualified adviser.
1.6358 forging weight calculator
⚖️ Estimate the weight of a 1.6358 forging
Uses the 1.6358 / Maraging 300 density of 8.0 g/cm³. Use the result to populate your inquiry. Weight drives the quotation on this grade more than any other variable.
Result is the net weight of the shape entered. A rough forging normally weighs 20–40 % more once machining stock, test prolongations and cropping are added. Maximum single-piece capability in 1.6358 at our works is 1,500 kg.
How to specify a 1.6358 forging order
A complete 1.6358 inquiry answers seven questions. Sending all seven at once typically saves two weeks of back-and-forth on this grade, because both the melting route and the export license have to be arranged before anything is made.
| # | Specify | Recommended wording |
|---|---|---|
| 1 | Designation | "1.6358 / X2NiCoMo18-9-5" or "UNS K93120 per AMS 6514", not a trademark |
| 2 | Delivery condition | "Solution annealed (ST)" or "Solution annealed + aged (STA), 480 °C / 4 h / AC" |
| 3 | Melting route | "VIM + VAR" for aerospace class, or "EAF + VOD + ESR" for industrial class |
| 4 | Geometry | 2D drawing or STEP file, with machining stock, tolerances and required grain-flow direction |
| 5 | Testing & NDT | "UT per EN 10228-3 class ___" plus MT or PT; state test orientation (longitudinal / transverse) |
| 6 | Certification | "EN 10204 3.1" or "EN 10204 3.2 witnessed by ___" |
| 7 | Export documentation | End-user, end use, destination, and any import certificate; supply with the inquiry |
Drawing callout template
Copy this block into the material box of your drawing. It removes most of the ambiguity we see on incoming 1.6358 inquiries.
Eight specification mistakes that cost time on 1.6358 orders
1. Treating 1.6358 as a stainless steel
It is not. Chromium is a 0.50 % residual and there is no passive layer. Parts arrive, sit in a humid store and rust. Fix: specify a surface protection on the drawing and require VCI packaging on the purchase order.
2. Ordering "Vascomax C300" on the purchase order
Vascomax® is a Carpenter Technology trademark. A PO written that way can strictly only be filled by Carpenter, and it creates a certification argument at goods-in. Fix: order "1.6358 / X2NiCoMo18-9-5 / UNS K93120 per AMS 6514".
3. Leaving the export license until shipment
The single largest cause of schedule loss on this grade. Licensing has to start at order review, before material is purchased. Fix: send the end-user and end-use statement with the inquiry. See Export control.
4. Not stating whether the part arrives annealed or aged
"1.6358, 52 HRC" and "1.6358, ready to machine" are different products at different prices with different lead times. Fix: write "supplied in ST condition" or "supplied in STA condition, fully aged".
5. Finish machining to final tolerance before aging
Aging contracts the part by 0.04–0.06 %, about 0.05 mm on a 100 mm bore. Small, but larger than an H7 fit. Fix: rough and semi-finish before aging, then grind critical features, or compensate in CAD.
6. Omitting the melting route
VIM+VAR and EAF+VOD+ESR material both meet the chemistry but differ in cleanliness, transverse properties and price. Discovering the difference at first-article inspection is expensive. Fix: state the route on the drawing.
7. Plating without a hydrogen bake
At 2,000 MPa, hydrogen embrittlement causes delayed cracking days or weeks after commissioning, usually at a thread root. Fix: mandate a 190–220 °C bake for 4–24 h immediately after any plating or acid pickling operation.
8. Specifying 1.6358 when Maraging 250 would do
If the part is limited by fatigue or impact rather than by yield, Maraging 250 is tougher, cheaper, and usually outside the export-control threshold. Fix: check the governing failure mode before fixing the grade. Ask us. We would rather quote the right material than the expensive one.
Frequently asked questions about 1.6358
What is material 1.6358?
1.6358 is the European Werkstoff number for X2NiCoMo18-9-5, an 18 % nickel cobalt–molybdenum maraging steel known internationally as Maraging 300, C300 or 18Ni(300) and designated UNS K93120. It is soft and freely machinable after solution annealing (about 28–32 HRC) and reaches roughly 1,930–2,050 MPa tensile strength after a single low-temperature aging treatment at 480 °C.
Is 1.6358 a stainless steel?
No. 1.6358 contains no deliberate chromium addition; chromium is limited to about 0.50 % as a residual. There is therefore no passive film, and it corrodes like carbon and low-alloy steel. Parts must be oiled, plated, nitrided, painted or otherwise protected. Many supplier datasheets repeat this error; the correct description is an ultra-high-strength low-carbon iron–nickel martensitic maraging steel.
What is the equivalent of 1.6358?
1.6358 is equivalent to X2NiCoMo18-9-5 (EN name), UNS K93120, AMS 6514 (bar and forging stock), ASTM A538 Grade C, ASTM A579, MIL-S-46850 Grade 300 and MIL-S-13881. It is commonly called Maraging 300, Maraging C300, Type 300 or 18Ni(300). Vascomax® C300 is a registered trademark of Carpenter Technology Corporation for the same chemistry. Full list in Table 1.
What is the chemical composition of 1.6358?
In weight percent: carbon 0.03 max, nickel 17.0–19.0, cobalt 8.5–9.5, molybdenum 4.6–5.2, titanium 0.50–0.80, aluminum 0.05–0.15, manganese 0.10 max, silicon 0.10 max, phosphorus 0.010 max, sulfur 0.010 max, chromium 0.50 max, copper 0.50 max, with small boron and zirconium additions, balance iron. See Table 2 for the metallurgical role of each element.
What are the mechanical properties of 1.6358 after aging?
After solution annealing plus aging at 480 °C, 1.6358 typically reaches 1,930–2,050 MPa (280–297 ksi) tensile strength, 1,860–1,965 MPa (270–285 ksi) yield strength at 0.2 % offset, 6–11 % elongation, 35–55 % reduction of area and 50–56 HRC. In the solution-annealed condition it is far softer, about 1,000–1,100 MPa and 28–32 HRC, which is when machining is done.
What is the heat treatment for 1.6358 maraging steel?
Two steps, both air-cooled. Solution anneal at 815–830 °C (1,500–1,525 °F) for approximately one hour per 25 mm of section, then air cool. The alloy transforms to soft martensite regardless of cooling rate, so no quench is needed. Then age (marage) at 480–485 °C (900 °F) for 3–6 hours and air cool. Strength comes from Ni₃Ti and Fe₂Mo intermetallic precipitates, not from carbon. Full cycle in Heat treatment.
How much does 1.6358 shrink during aging?
Approximately 0.04 % to 0.06 % linear contraction, about 0.4–0.6 mm per meter. Because aging happens at low temperature with no quench, distortion is very small, which is why maraging steels dominate precision die and tooling work. Allow for the contraction on tight-tolerance features, or finish-machine after aging.
What is the difference between Maraging 250, 300 and 350?
Cobalt and titanium content, which sets achievable strength. Maraging 250 (UNS K92890, AMS 6512) has about 7.0–8.5 % Co and 0.30–0.50 % Ti, reaching roughly 1,725–1,800 MPa. Maraging 300 / 1.6358 (UNS K93120, AMS 6514) has about 8.5–9.5 % Co and 0.50–0.80 % Ti, reaching roughly 1,930–2,050 MPa. Maraging 350 (AMS 6515) has about 11.5–12.5 % Co and 1.30–1.60 % Ti, reaching roughly 2,400 MPa but with markedly lower toughness. Toughness falls as strength rises. Full comparison in Table 7.
Can 1.6358 be welded?
Yes, and unusually well for a 2,000 MPa steel. With carbon below 0.03 % the heat-affected zone cannot form brittle high-carbon martensite, so no preheat is required. Weld with matching maraging filler under GTAW or electron beam, keep heat input low, then re-age at 480 °C to restore properties in the weld and HAZ. A full solution anneal plus age gives the most uniform result.
Is 1.6358 maraging steel export controlled?
Yes. Maraging steel capable of an ultimate tensile strength of 1,950 MPa or more at 20 °C is a listed dual-use item: ECCN 1C216 on the US Commerce Control List and the corresponding entry in the EU Dual-Use Regulation and the Nuclear Suppliers Group guidelines. Aged 1.6358 exceeds that threshold. Orders require end-user and end-use documentation and an export license in most jurisdictions, which extends lead time. Jiangyin Jiangnan Metal Co., Ltd. supplies this grade only against complete documentation and applicable licenses. See Export control.
What forged shapes are available in 1.6358?
Jiangyin Jiangnan Metal Co., Ltd. produces 1.6358 as seamless rolled rings, forged rings, shafts and spindles, round and flat bars, discs and blanks, flanges, sleeves, bushings, blocks, tube sheets, hollow trepanned billets and near-net-shape forgings, all to customer drawings, in the solution-annealed or aged condition.
What is the density of 1.6358?
Approximately 8.0 g/cm³ (0.289 lb/in³), slightly higher than plain carbon steel because of the 18 % nickel and 9 % cobalt content. Use the weight calculator to estimate a forging weight.
What is the maximum service temperature of 1.6358?
1.6358 retains useful strength to roughly 400–450 °C for short exposure. For continuous service keep well below the 480 °C aging temperature: prolonged exposure near or above it over-ages the precipitates, and the strength loss is permanent. A conservative continuous limit is 400 °C. Above that, use Inconel 718 or Waspaloy.
Why is 1.6358 machined before aging rather than after?
Solution-annealed 1.6358 is about 28–32 HRC, soft enough for conventional carbide machining. Aged, it is 50–56 HRC and needs grinding or ceramic and CBN tooling. Standard practice is to rough and semi-finish in the annealed condition, age at 480 °C, then grind or finish-machine only the critical features, allowing for the small aging contraction.
Who manufactures 1.6358 forgings in China?
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, manufactures 1.6358 / X2NiCoMo18-9-5 / Maraging 300 forgings to AMS 6514 and ASTM A538 Grade C. The works operates open-die forging hammers, a hydraulic press and seamless ring-rolling mills, with in-house heat treatment, mechanical testing, spectrometry, metallography and non-destructive testing. Contact 0086-189-2135-9659 or sales@steelforgepieces.com.
Glossary
- Maraging
- Contraction of martensitic + aging. A hardening mechanism in which a soft iron–nickel martensite is strengthened by low-temperature precipitation of intermetallic compounds rather than by carbon.
- 1.6358
- European Werkstoff number for X2NiCoMo18-9-5, the 18Ni(300) maraging steel. The subject of this page.
- X2NiCoMo18-9-5
- EN descriptive name: very low carbon, 18 % nickel, 9 % cobalt, 5 % molybdenum.
- UNS K93120
- Unified Numbering System designation for Maraging 300. The cleanest generic identifier for purchase orders.
- AMS 6514
- SAE Aerospace Material Specification for 18Ni(300) maraging steel bars, forgings and forging stock.
- ASTM A538 Grade C
- ASTM specification for 18 % nickel maraging steel pressure-vessel plate. Grade A = 200, Grade B = 250, Grade C = 300.
- ST
- Solution-treated (solution annealed) condition: 815–830 °C, air cool, ≈28–32 HRC. The machinable delivery condition.
- STA
- Solution-treated and aged condition: ST followed by 480 °C for 3–6 h, ≈50–56 HRC. The final service condition.
- Ni₃Ti / Fe₂Mo
- The intermetallic precipitates formed during aging. They are what gives 1.6358 its strength.
- Reverted austenite
- Austenite that re-forms if the alloy is held above roughly 510 °C. It softens the material and cannot be removed by further aging, only by a full re-solution anneal.
- VIM + VAR
- Vacuum induction melting followed by vacuum arc remelting. The aerospace-class melting route for this grade.
- ESR
- Electroslag remelting. Refines the ingot structure and reduces inclusions; used in the industrial-class route.
- EN 10204 3.1 / 3.2
- Inspection document types. 3.1 is issued by the manufacturer's independent quality department; 3.2 adds a third-party witness.
- EN 10228-3
- European standard for ultrasonic testing of ferritic and martensitic steel forgings. The usual UT reference for 1.6358.
- ECCN 1C216
- Export Control Classification Number covering maraging steel capable of 1,950 MPa or more. Aged 1.6358 falls under it.
- 1.2709
- Tool-steel number (X3NiCoMoTi18-9-5) used for the same 18Ni300 chemistry in additive manufacturing powder.
Technical references
Composition, property, heat-treatment and control-list information on this page is drawn from the published standards and references below. Certified values for your order are independent and are stated on the material certificate for the heat supplied.
- SAE AMS 6514, Steel, Maraging, Bars, Forgings, Tubing, and Rings, 18.5Ni – 9.0Co – 4.9Mo – 0.65Ti – 0.10Al, Consumable Electrode Vacuum Melted, Annealed, SAE International.
- ASTM A538/A538M, Standard Specification for Pressure Vessel Plates, Alloy Steel, Precipitation Hardening (Maraging), 18 Percent Nickel, ASTM International.
- ASTM A579/A579M, Standard Specification for Superstrength Alloy Steel Forgings, ASTM International.
- EN 10027-2, Designation systems for steels — Part 2: Numerical system, CEN.
- EN 10204:2004, Metallic products — Types of inspection documents, CEN.
- EN 10228-3, Non-destructive testing of steel forgings — Part 3: Ultrasonic testing of ferritic or martensitic steel forgings, CEN.
- SEP 1921, Ultrasonic testing of steel bars and forgings, Stahl-Eisen-Prüfblatt, VDEh.
- ASTM A388/A388M, Standard Practice for Ultrasonic Examination of Steel Forgings, ASTM International.
- ASM Handbook, Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys, ASM International. Section on maraging steels.
- ASM Handbook, Volume 4D: Heat Treating of Irons and Steels, ASM International. Heat treatment of maraging steels.
- Decker, R.F. and Floreen, S., Maraging Steels — The First 30 Years, TMS, 1988.
- Sha, W. and Guo, Z., Maraging Steels: Modelling of Microstructure, Properties and Applications, Woodhead Publishing, 2009.
- Nuclear Suppliers Group, Guidelines for Transfers of Nuclear-Related Dual-Use Equipment, Materials, Software and Related Technology (INFCIRC/254 Part 2), current revision.
- US Bureau of Industry and Security, Commerce Control List, Category 1, ECCN 1C216 and 1C116, current revision.
- Regulation (EU) 2021/821, Annex I, dual-use items list, current revision.
- Wikipedia, Maraging steel, general background on the alloy class.
Always reference the standard revision in force at your contract date. Trademarks named on this page are the property of their respective owners.
Request a quotation for 1.6358 forgings
- Manufacturer
- Jiangyin Jiangnan Metal Co., Ltd.
Open-die forging factory - Address
- No.1 Chengxiqiao Road,
Zhouzhuang Town, Jiangyin City,
Jiangsu Province, China - Telephone / WhatsApp
- 0086-189-2135-9659
- Website
- www.steelforgepieces.com
- Response time
- Price and lead time within 24 hours of a complete inquiry
Send a drawing or the dimensions, the required condition (ST or STA), the melting route, the NDT class, the certificate type and your end-use statement. For 1.6358 the end-use statement is needed at inquiry stage, not at order stage. See Export control.
Related grades and forged products
Maraging 250 (AMS 6512) · Maraging 350 (AMS 6515). Ask us for the comparison against your load case.
PH 13-8 Mo · 17-4PH · 15-5PH · 17-7PH
Inconel 718 · Waspaloy · Rene 41 · MP35N
Forged rings · Forged discs · Forging products · Eccentric shafts