40CrNi2Mo, 4340, SnCM439, 1.6563 Low Alloy Ultra-High Strength Steels- SCALE STEEL.

​40CrNi2Mo, also known as 4340 steel, is a kind of low alloy ultra-high strength steel.Only steels with tensile strength greater than [SCALE STEEL]1400MPa and yield strength greater than 1200MPa at room temperature are termed "ultra-high strength steels".4340 steel is a typical ultra high strength steel, which is obtained by heat treatment.

Standards:
CHINA GB/T 3077-2015 40CrNi2Mo，A50400
GB/T 34484.2-2018 40CrNi2Mo
GB/T 38809-2020 40CrNi2MoA
GB/T 5216-2014 40CrNi2MoH
USA ASTM A29-2005[SCALE STEEL]
ASTM A322-2007 4340，G43400
JAPAN JIS G4053-2003 SNCM439
GERMANY DIN EN 10263-4:2002 41NiCrMo7-3-2，1.6563

Chemical Composition(%):
Grade A50400 4340 SNCM439 1.6563
C 0.38~0.43 0.38~0.43 0.36~0.43 0.38~0.44
Si 0.17~0.37 0.15~0.35 0.15~0.35 ≤0.30
Mn 0.60~0.80 0.60~0.80 0.60~0.90 0.60~0.90
P ≤0.030 ≤0.035 ≤0.030 ≤0.025
S ≤0.030 ≤0.040 ≤0.030 ≤0.025
Cr 0.70~0.90[SCALE STEEL] 0.70~0.90 0.60~1.00 0.70~0.90
Ni 1.65~2.00 1.65~2.00 1.60~2.00 1.65~2.00
Mo 0.20~0.30 0.20~0.30 0.15~0.30 0.15~0.30
Cu ≤0.30 ≤0.35 ≤0.30 ≤0.25

Mechanical Property:  
QUENCHED FIRST TIME NORMALIZED AT 890℃，OIL QUENCHING
SECOND TIME 850℃，OIL QUENCHING
TEMPERED(AIR COOLING) 560~580℃ 220℃ TWICE OIL QUENCHING
TENSILE STRENGTH MPa ≥1050 ≥1790
YIELD STRENGTH MPa ≥980 ≥1500
ELONGATION % ≥12 ≥6
REDUCTION OF AREA %[SCALE STEEL] ≥45 ≥25
IMPACT TESTJ ≥48 --
TEMPERED HARDNESS ≤269HBW

Performance Applications:
4340 steel after heat treatment, not only obtain ultra-high strength, but also have good plastic toughness, excellent fatigue performance, fracture toughness and stress corrosion resistance, good comprehensive mechanical [SCALE STEEL]properties, so that it is often used in the industry as a tempering steel to manufacture bearings, gears and crankshafts, and in the aircraft structure has been widely used.Such as aircraft landing gear, helicopter rotor shaft and turbojet turbine shaft and other moving parts.