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| Grade | Code | AISI | High-Strength Stainless Steel |
| 1.4418 / S165M | X4CrNiMo16-5-1 | - |
1.4418 / S165M, is a soft-martensitic stainless steel that combines high mechanical strength with good toughness, fatigue resistance, and weldability. It offers greater corrosion resistance than conventional martensitic stainless steels and largely retains its mechanical properties after welding. It is generally supplied in the quenched-and-tempered condition.
| C % | Si % | Mn % | P % | S % | Cr % | Ni % | Mo % |
| ≤ 0.06 | ≤ 0.70 | ≤ 1.50 | ≤ 0.04 | ≤ 0.03 | 15.00–17.00 | 4.00–6.00 | 0.80–1.50 |
| Product Form | Rp0.2, MPa | Rm, MPa | Elongation [%] | Hardness [HB] | Density [g/cm³] |
| Bar QT900 | ≥ 700 | 900 – 1100 | ≥ 16 | 280 – 340 | 7.7 |
Note: The mechanical properties stated in the table apply to QT900 bars with diameters below 160 mm.
| Sector | Products |
| Hydropower and energy | Water turbine components, turbine shafts, couplings |
| Marine and shipbuilding | Propeller shafts, rudder stocks, seawater pump shafts |
| Oil and gas | Pump components, valve stems, high-strength fasteners |
| Chemical and process industries | Agitator shafts, centrifuge components, valves |
| Pulp and paper | Process equipment, agitator shafts, pump components |
| Mining and separation technologies | Centrifuge shafts, separator components, homogenizer shafts |
| Automotive | Crankshafts, piston rods, fuel injector bodies |
| Aerospace and defense | High-strength shafts, fasteners, pressure-system components |
| Mechanical and plant engineering | Axles, spindles, pins |
| Hydraulic systems | Hydraulic-cylinder piston rods, pump shafts, valve components |
The performance of 1.4418 / S165M is derived from the balanced distribution of tempered martensite, stable austenite, and controlled ferrite phases formed after quenching and tempering. The QT900 condition is designed to retain ductility and impact toughness while targeting a minimum tensile strength of 900 MPa. This microstructure delivers stable performance under operating conditions involving cyclic loads, vibration, sudden impact, cavitation, and flow-induced surface wear.
Its low carbon content reduces the risk of hard and brittle zones forming during welding, helping preserve strength and toughness in welded joints. The molybdenum-bearing alloy structure supports localized corrosion resistance in humid environments and in contact with flowing media. The material is magnetic and is generally machined in the QT900 delivery condition, after acquiring its final mechanical properties. For this reason, procurement and manufacturing specifications should state not only the grade, but also the delivery condition, bar diameter, and hardness range.
1.4418, S165M, X4CrNiMo16-5-1
| Product Form | ASTM | DIN |
| Bar | ASTM A276, ASTM A484/A484M* | DIN EN 10088-3, DIN EN 10272** |
* ASTM standards may be used for general bar production, surface condition, dimensional, and tolerance requirements; however, they are not a direct ASTM grade equivalent for 1.4418.
** DIN EN 10088-3 covers stainless steel bars for general purposes, whereas DIN EN 10272 covers stainless steel bars intended for pressure equipment. The grade and condition should be specified on the order as 1.4418 / X4CrNiMo16-5-1 +QT900.
1.4313 / AISI 415 – This is the closest alternative in terms of microstructure, weldability, toughness, and mechanical properties near the QT900 level.
15-5PH – It may be considered for shafts, pumps, and fasteners requiring high strength, good toughness, and corrosion resistance.
13-8PH – It is a strong alternative for critical components where high strength, fatigue resistance, and impact resistance are important.
Swiss Steel Group / Ugitech – UGI® 4418 AIR
Carpenter Technology – VACUMET® 1.4418 Stainless
Note: The information contained in this datasheet is for informational purposes only; no liability is accepted.
