# X2NiCoMoTi18-12-4 Forgings (Werkstoff 1.6358)

**Manufacturer:** Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory
**Address:** No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
**Telephone:** +86-189-2135-9659
**Email:** sales@steelforgepieces.com
**Web page:** https://www.steelforgepieces.com/Nickel-Alloy/X2NiCoMoTi18-12-4.html
**Last reviewed:** 2 September 2026

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## Summary

X2NiCoMoTi18-12-4 is an ultra-high-strength maraging steel with material number 1.6358, alloyed with roughly 18% nickel, 12% cobalt, 4.8% molybdenum and 1.4% titanium on an ultra-low-carbon iron matrix. Unlike a quenched and tempered steel, it takes its strength from intermetallic precipitation during a low-temperature ageing treatment, reaching a minimum tensile strength of 2345 MPa with very little heat-treatment distortion. Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory in Jiangyin, Jiangsu, China, forges this grade into rings, seamless rolled rings, flanges, bars, shafts, discs, sleeves and tube sheets to customer drawing, with EN 10204 3.1 or 3.2 certification.

## Identification

| Field | Value |
|---|---|
| EN / DIN designation | X2NiCoMoTi18-12-4 |
| Material number | 1.6358 |
| Material class | High-alloy maraging steel, 18Ni cobalt-strengthened |
| Also known as | Maraging 350, 18Ni(350), C350 |
| Melting route | EAF + VOD + ESR |
| Certification | EN 10204 3.1 / 3.2 |

## Key facts

- X2NiCoMoTi18-12-4 carries the Werkstoff number 1.6358 and is supplied to DIN/EN.
- Minimum tensile strength 2345 MPa (340 ksi); minimum yield strength 2275 MPa (330 ksi).
- Hardness up to 56 HRC with a minimum elongation of 3%.
- Carbon is held to 0.03% maximum, so strength comes from Ni-Co-Mo-Ti intermetallic precipitation rather than from carbides.
- Jiangyin Jiangnan Metal Co., Ltd. forges the grade in open dies and rolls seamless rings from it.
- Ultrasonic testing is available to EN 10228-3, SEP 1921 or ASTM A388.
- Quotations come from sales@steelforgepieces.com or +86-189-2135-9659.

## Chemical composition (weight %)

Iron makes up the balance. Every heat is supplied with its own ladle analysis on the mill certificate.

| Element | Minimum | Maximum |
|---|---|---|
| Nickel (Ni) | n/a | 18.5 |
| Cobalt (Co) | n/a | 12.0 |
| Molybdenum (Mo) | n/a | 4.8 |
| Titanium (Ti) | n/a | 1.4 |
| Manganese (Mn) | n/a | 0.10 |
| Silicon (Si) | n/a | 0.10 |
| Aluminium (Al) | n/a | 0.10 |
| Carbon (C) | n/a | 0.03 |
| Zirconium (Zr) | n/a | 0.01 |
| Phosphorus (P) | n/a | 0.01 |
| Sulphur (S) | n/a | 0.01 |
| Boron (B) | n/a | 0.003 |
| Iron (Fe) | Balance | Balance |

## Mechanical properties, aged condition

| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | 2345 MPa min | 340 ksi min |
| Yield strength | 2275 MPa min | 330 ksi min |
| Hardness | 56 HRC max | 56 HRC max |
| Elongation | 3% min | 3% min |

## Equivalent designations

Confirm the exact specification against your own order standard before release, since cross-reference tables between the EN, UNS and ASTM systems are not always exact.

| System | Designation |
|---|---|
| EN / DIN | X2NiCoMoTi18-12-4 |
| Werkstoff number | 1.6358 |
| Common trade description | Maraging 350, 18Ni(350), C350 |
| UNS | K93160 |
| ASTM | A538 Grade C |
| AMS | 6515 |

## Forged forms supplied

Every part is forged to the customer's drawing.

| Forged form | Typical use |
|---|---|
| Forged rings and seamless rolled rings | Gas turbine hot-section hardware, gearboxes, bearing races |
| Forged flanges and tube sheets | Pressure vessels, air receivers, shell-and-tube heat exchangers |
| Forged round bars and blocks | Machined components, die and tool blanks |
| Forged shafts, spindles and eccentric shafts | Power transmission, compressors, turbines |
| Forged discs, disks and hubs | Rotating hardware, couplings |
| Forged sleeves and bushings | Subsea and deepwater production equipment, compressors |
| Forged tubes and pipes | Columns, towers, tanks, process modules, preheaters |
| Forged valve bodies, seat rings and stems | Ball, gate, globe, check and plug valves |
| Forged nozzles, rolls and wheels | Heavy machinery, shipbuilding, pulp and paper, mills |

## Supply condition

| Field | Value |
|---|---|
| Delivery condition | As-forged, rough machined, solution annealed, or solution annealed and aged |
| Machining allowance | Agreed on the drawing before production |
| Marking | Heat number, grade and order number |
| Packing | Seaworthy wooden case or steel pallet |

Ring diameter, single-piece forging weight and bar length are limited by our press and ring-rolling mill. Send the drawing and we confirm feasibility in writing before quoting.

## Applications

**Energy and process plant.** Subsea and deepwater oil production systems, wellhead and Christmas tree components, industrial air compressors, power generators, nitrogen generators, columns, towers, silos and preheaters.

**Turbomachinery and power transmission.** Gas turbine hot-section components where hot strength matters, turbine and compressor shafts, gearboxes, gears and spindles.

**Heavy industry.** Cement mills, sugar mills, concrete mixers, forging rolls, shipbuilding, crystalliser equipment, pulp and paper plant, and pharmaceutical and biochemical processing equipment.

## Melting, forging and inspection

X2NiCoMoTi18-12-4 is melted by EAF followed by VOD and ESR refining, which controls the sulphur, phosphorus and non-metallic inclusion content that this grade is sensitive to. Ingots are then open-die forged with a controlled forging ratio and heat treated before machining.

Non-destructive testing is carried out to the standard named on the order: ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, with magnetic particle and dimensional inspection on request. Material certificates are issued to EN 10204 3.1, or to EN 10204 3.2 countersigned by a third-party inspection body such as SGS, BV, TUV or Lloyd Register.

## How to request a quotation

Send the following to sales@steelforgepieces.com:

1. Drawing, or finished dimensions plus the machining allowance you want on the forging.
2. Quantity and target delivery date.
3. Grade and standard, plus the delivery condition (as-forged, solution annealed or aged).
4. Testing and certification requirements, including any third-party inspection.

Quotations are normally returned within one working day. For urgent enquiries call +86-189-2135-9659.

## Frequently asked questions

**What is X2NiCoMoTi18-12-4?**
X2NiCoMoTi18-12-4 is a cobalt-strengthened 18% nickel maraging steel covered by DIN/EN and carrying material number 1.6358. It is an ultra-low-carbon iron-nickel martensite that gains strength from intermetallic precipitation during ageing rather than from carbon, reaching a minimum tensile strength of 2345 MPa. It is widely known as Maraging 350 or 18Ni(350).

**What is the material number for X2NiCoMoTi18-12-4?**
The Werkstoff number for X2NiCoMoTi18-12-4 is 1.6358.

**What forged shapes can be made in X2NiCoMoTi18-12-4?**
Jiangyin Jiangnan Metal Co., Ltd. produces X2NiCoMoTi18-12-4 as open-die forged rings, seamless rolled rings, flanges, round bars, shafts, spindles, discs, sleeves, bushings, tube sheets, forged tubes, pipes, blocks, nozzles and valve components, all forged to customer drawing.

**How strong is X2NiCoMoTi18-12-4 maraging steel?**
In the aged condition it provides a minimum tensile strength of 2345 MPa (340 ksi), a minimum yield strength of 2275 MPa (330 ksi), hardness up to 56 HRC and a minimum elongation of 3%.

**Why use X2NiCoMoTi18-12-4 instead of a quenched and tempered steel?**
Maraging steels are machined soft in the solution-annealed condition and then aged at a low temperature, so they move very little compared with the quench of a conventional high-strength steel. That makes X2NiCoMoTi18-12-4 useful for close-tolerance forged parts that need 2000 MPa class strength without the dimensional movement of a water or oil quench.

**What certification is supplied with X2NiCoMoTi18-12-4 forgings?**
An EN 10204 3.1 mill certificate as standard, or an EN 10204 3.2 certificate countersigned by a third-party inspection body. Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388 as specified on the order.

**How do I get a price for X2NiCoMoTi18-12-4 forgings?**
Send the drawing or finished dimensions, quantity, required standard and any testing or certification requirements to sales@steelforgepieces.com, or call +86-189-2135-9659. Jiangyin Jiangnan Metal Co., Ltd. is at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China.

## About the manufacturer

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. The works forges rings, seamless rolled rings, flanges, shafts, bars, discs, sleeves, bushings and tube sheets in carbon steel, alloy steel, tool steel, stainless steel, nickel alloys and maraging steels including X2NiCoMoTi18-12-4, supplying valve, pressure vessel, oil and gas, power generation and heavy machinery manufacturers worldwide.

| Field | Value |
|---|---|
| Company | Jiangyin Jiangnan Metal Co., Ltd. |
| Address | No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China |
| Telephone | +86-189-2135-9659 |
| Email | sales@steelforgepieces.com |
| Website | https://www.steelforgepieces.com/ |

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Property data is given for guidance. The governing values are those on the mill certificate issued with your order.