What is AISI 431 / 1.4057 stainless steel bar?

What is AISI 431 / 1.4057 stainless steel bar?

AISI 431 stainless steel bar is a high-strength martensitic stainless steel round bar defined by the American Iron and Steel Institute standard, corresponding to the European standard 1.4057 and the Chinese standard 1Cr17Ni2.

It contains 15.0%~17.5% chromium and 1.25%~2.5% nickel. After quenching and tempering heat treatment, its hardness can reach 45~50 HRC, and its corrosion resistance is far better than that of ordinary 410 and 420 martensitic stainless steels. It is widely used to manufacture high-strength mechanical parts such as shafts, bolts, valve bodies and food machinery components.

 

AISI 431 / 1.4057 Stainless Steel Bar Specification

Chemical Composition of 1.4057 Stainless Steel Bar

1.4057 SS 431	C	Si	Mn	P	S	Cr	Mo	Ni	V
min.	0,12					15,0		1,50
max.	0,22	1,0	1,50	0,04	0,015	17,0		2,50

 

Mechanical Properties (at Room Temperature in QT Condition)

Heat Treatment Condition	Tensile Strength (Rm)	Yield Strength (Rp 0.2%)	Elongation (A5)	Impact Energy (KV)	Hardness (Brinell)
QT 800	800 – 950 MPa	≥ 600 MPa	≥ 14%	≥ 25 J	240 – 295 HBW
QT 900	900 – 1050 MPa	≥ 700 MPa	≥ 12%	≥ 20 J	280 – 335 HBW
Annealed (+A)	---	---	---	---	≤ 295 HBW

 

Physical Properties (Average Values)

Density	Modulus of Elasticity	Thermal Conductivity	Specific Heat	Electrical Resistivity	Magnetism
7.70 g/cm³	215 GPa (at 20°C)	25 W/m·K (at 20°C)	460 J/kg·K	0.70 Ω·mm²/m	Yes (Ferromagnetic)

 

Technical Fabrication & Heat Treatment Guidance

Process	Temperature Range	Cooling Method	Notes
Hot Forming	1100°C – 800°C	Slow cooling (sand/ashes)	Avoid rapid cooling to prevent cracking.
Annealing (+A)	650°C – 750°C	Air or Furnace	To achieve a max hardness of 295 HBW.
Hardening	950°C – 1050°C	Oil or Air	Results in martensitic structure.
Tempering	600°C – 700°C	Air	Critical for balancing strength and toughness.
Welding	200°C – 300°C Pre-heat	Slow cooling	Hardens in heat-affected zone; post-weld tempering required.

 

1.4057 Stainless Steel Bar Supplier/Manufacturer

We maintain a ready stock of commonly used specifications in QT800/QT900 grades, enabling standard orders to ship within 3–7 days and effectively shortening our customers' production cycles. For large-scale applications such as pump shafts and marine shafts, we supply large-diameter forged round bars characterized by a dense microstructure and freedom from internal defects, boasting an industry-leading pass rate for ultrasonic testing.

 

Supply Range & Dimensional Tolerances

Product Form	Diameter / Size Range	Length	Surface Finish	Tolerance (ISO)
Round Bar	5.0mm – 600mm	3000mm – 12000mm	Black, Peeled, Polished, Ground	h9, h10, h11, k12
Hexagonal Bar	10mm – 100mm	3000mm – 6000mm	Cold Drawn, Bright	h11, h12
Flat Bar	(5-120) x (20-500) mm	3000mm – 6000mm	Pickled, Sand-blasted	DIN 1017

 

Quality Inspection

To address the risk of internal cracking or microstructural non-uniformity inherent in grade 1.4057, GNEE conducts multiple inspections:
Chemical Analysis: 100% PMI (Positive Material Identification) spectral analysis.
Mechanical Testing: Impact testing (specifically low-temperature impact) and hardness testing.
Ultrasonic Testing: For round bars intended for shaft applications, testing is performed in accordance with SEP 1921 Class C/c or D/d standards to ensure the absence of internal shrinkage cavities, slag inclusions, or cracks.

Expert Packaging

Anti-rust Treatment: Surfaces are coated with high-performance anti-rust oil and wrapped in moisture-proof plastic film to withstand long-distance maritime transport.
Physical Protection: Bright bars/precision-ground bars are individually sleeved or packed in partitioned woven bags.
Plastic protective caps are fitted to both ends to safeguard chamfers and end faces.
Reinforced Packaging: Packed in fumigated wooden cases compliant with international standards to prevent bending of small-diameter bars.

FAQ

 

Is 1.4057 stainless steel magnetic?
Yes. As a martensitic stainless steel, 1.4057 is ferromagnetic in all conditions (whether annealed or heat-treated) and is strongly attracted to magnets.

 

How does 1.4057 compare to 304 or 316 stainless steel?
Strength: 1.4057 offers significantly higher strength and hardness than 304 or 316. It is suitable for applications requiring high mechanical load-bearing capacity. 304 and 316 stainless steels generally offer superior corrosion resistance, particularly in acidic environments.
Heat Treatment: 1.4057 can be hardened via quenching and tempering, whereas 304 and 316 cannot be hardened by heat treatment.

 

What do "QT 800" and "QT 900" mean?
QT 800: Achieves a tensile strength of 800–950 MPa after heat treatment.
QT 900: Achieves a tensile strength of 900–1050 MPa after heat treatment.

 

Can AISI 431 be welded?
Welding is challenging but feasible. Due to its high carbon content and air-hardening characteristics, it is prone to cold cracking during welding. Preheating to 200°C–300°C is mandatory. Post-weld tempering or annealing is required to restore ductility in the heat-affected zone (HAZ).