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Eternal
AISI 431 stainless steel forged shafts are made from martensitic stainless steel 431 (UNS S43100 / DIN 1.4057 / JIS SUS431). They are formed by open-die forging. With carefully controlled quenching and tempering, they achieve high strength, high hardness, and good toughness.
Grade 431 has the best corrosion resistance among martensitic stainless steels. It contains 15–17% chromium and 1.25–2.50% nickel. Its corrosion resistance is close to that of 304 austenitic stainless steel, while its strength and hardness are much higher than those of austenitic stainless steel.
AISI 431 forged shafts are widely used for pump shafts, drive shafts, stern shafts/propeller shafts, valve stems, and other key parts that carry high loads and face mild corrosion. They are an ideal choice for heavy-duty shaft parts in corrosive conditions.
Jiangyin Eternal Heavy Industry Co., Ltd. focuses on making stainless steel forgings. It is TUV certified and provides stainless steel forgings that meet ASTM A388 inspection requirements to customers at home and abroad.
The typical chemical composition (in wt.%) of the 431 stainless steel forged shaft is as follows:
Element | C | Si | Mn | P | S | Cr | Ni |
wt% | 0.12–0.20 | ≤1.00 | ≤1.00 | ≤0.040 | ≤0.030 | 15.00–17.00 | 1.25–2.50 |
Nickel is the key that makes 431 different from other martensitic stainless steels. A small amount of nickel keeps the steel in an austenitic structure at heat-treatment temperatures. Even with higher chromium, it can form hard martensite after quenching. Carbon is kept below 0.20%, which gives both strength and toughness. Impurities such as phosphorus and sulfur must be kept very low to ensure the impact toughness of the forgings.
Standard | Grade | Material No. |
AISI / ASTM / UNS | 431 | UNS S43100 |
EN | X17CrNi16-2 | 1.4057 |
DIN | X22CrNi17（旧）/ X17CrNi16-2（新） | 1.4057 / 1.4044 |
JIS | SUS 431 | — |
BS | 431S29 | EN57 |
AFNOR | Z15CN16-02 | — |
GB | 1Cr17Ni2（旧）/ 14Cr17Ni2（新） | S43110 |
SS | 2321 | — |
UNI | X16CrNi16 | — |
Applicable Product Standards:
ASTM A473 (stainless steel forging standard)
ASTM A276 / A479 (stainless steel bar standards)
AMS 5628 (aerospace forging standard, with tensile strength up to 1379 MPa)
EN 10088-3 / EN 3365 / EN 3490 / EN 3491 (European aerospace forging standards)
Preheating stage: Slowly preheat at approximately 850°C to avoid cracking caused by rapid heating.
Forging temperature: After heating at 1150–1180°C, complete the forging deformation within the range of 1180–950°C.
Post-forging cooling: After forging, cool slowly (furnace cooling or cooling in dry ash) to prevent excessive internal stresses.
At Jiangyin Eternal Heavy Industry Co., Ltd., years of accumulated forging practice have yielded the following practice-proven guidelines:
For Grade 1.431, experience shows that excessively high forging temperatures readily lead to the formation of δ-ferrite, which impairs subsequent heat treatment response and mechanical properties; excessively low temperatures sharply increase deformation resistance and readily cause forging cracks. Therefore, the forging temperature window must be precisely controlled.
For large shaft forgings, our forging practice recommends a combined upsetting and drawing process, with a total forging ratio of no less than 4, to ensure grain refinement and a dense, sound microstructure.
For large forgings with diameters over 300 mm, experience requires sufficient homogenizing annealing after forging to eliminate compositional segregation and microstructural inhomogeneity.
Process | Temp. | Cooling way | Note |
Annealing (softening) | 620–660°C | air | Hardness≤285 HB |
Quenching | 950–1030°C | oil or air | Hardness 47 HRC |
Tempering | 580–680°C | air | Regular tempering temperature range |
Through years of accumulated practical experience in stainless steel heat treatment, Jiangyin Eternal Heavy Industry Co., Ltd. recommends a quenching temperature of 980–1030 °C for 431 stainless steel forgings; both oil quenching and air cooling can produce a martensitic microstructure. The tempering temperature should be selected according to the target strength grade: QT800 (tempering at 750–800 °C, with a tensile strength of 800–950 MPa) and QT900 (tempering at 600–650 °C, with a tensile strength of 900–1050 MPa).
The typical mechanical properties of the 431 stainless steel forged shaft under different heat treatment conditions are as follows:
Item | Annealing state | QT state（QT800） | QT state（QT900） | High-strength state（AMS 5628） |
Tensile strength Rm (MPa) | — | 800–950 | 900–1050 | ≥1379 |
Yield strength Rp0.2 (MPa) | — | ≥600 | ≥700 | ≥1034 |
Elongation A (%) | — | ≥14 | ≥12 | ≥10 |
Impact energy (J, 25°C) | — | ≥14 | ≥12 | — |
Hardness | ≤285 HB | 248–302 HB | — | — |
The 431 forged shaft is a commonly used material for manufacturing stern shafts, propeller shafts, and external motor drive shafts of ships. Its resistance to seawater corrosion is excellent in cold seawater environments and is suitable for equipment such as offshore platforms and ship propulsion systems.
It is widely used in pump shafts, valve stems, valve seats, agitator drive shafts, etc. In the chemical, petrochemical and food processing industries, these components need to withstand continuous loads in mild corrosive media. The high strength and corrosion resistance of the 431 forged shaft make it an ideal material.
The 431 forged part shaft is used for aircraft fasteners, accessories, and structural components exposed to the marine atmospheric environment. The AMS 5628 standard requires a tensile strength of ≥ 1379 MPa, meeting the stringent requirements for aerospace-grade high-stress components.
Including drive shafts, gear shafts, connecting rods, hydraulic rods, etc. The high strength and wear resistance of 431 make it suitable for heavy-duty conditions in mining machinery, metallurgical equipment, and other applications.
What is the difference between a 431 stainless steel forged shaft and a 304 stainless steel shaft? How should I choose?
431 is a high-strength martensitic stainless steel. After heat treatment, its tensile strength can reach 1000–1400 MPa, with a hardness of HRC 28–45, making it suitable for heavy-duty shaft applications. 304 is an austenitic stainless steel with lower strength (approximately 520–720 MPa) but better corrosion resistance and weldability. If the application prioritizes strength and wear resistance and the corrosive environment is mild to moderate, 431 is preferred. If corrosion resistance is the primary requirement and the load is relatively low, choose 304.
What is the maximum service temperature of a 431 forged shaft?
The continuous service temperature limit of 431 is approximately 700°C, which is its oxidation limit. However, considering temper softening, the recommended long-term working temperature should not exceed 600°C. Service above the tempering temperature can cause permanent softening of the material.
How does a 431 forged shaft perform in seawater environments?
It performs reasonably well in cold seawater, such as in temperate marine areas, but it is not suitable for tropical warm-water environments. For long-term seawater immersion, consider duplex stainless steel 2205 or super duplex stainless steel 2507.
What is the relationship between the corrosion resistance of a 431 forged shaft and its surface condition?
In the hardened and tempered condition, the best corrosion resistance is achieved with a ground or polished surface. Higher surface roughness, the presence of scale, or attached foreign matter will significantly reduce corrosion resistance. Pickling and passivation after machining are recommended to restore optimum corrosion resistance.
