40Cr steel material widely be used in the machine-building industry. 40Cr is a standard grade of GB. After quenching and tempering, it will get great comprehensive mechanical property and great low-temperature impact toughness. And its hardenability is good. After the oil quenching, the fatigue limit will be higher. But the fittings with complex shape is easy to get crack after the water quenching. It is also suitable for cyaniding and high-frequency quenching beside Q+T. Its machinability also is good, if the hardness is 174-229 HB, the machinability is 60%. 40Cr steel material is a good choice for medium type plastic mold. It belongs to mild Q+T steel and cold heading mold steel. Also, the price is not high, easy to be processed. After the right heat treatment, it will get good toughness, plasticity and wear resistance. Tempering at the range of 550-570℃, it will get the best mechanical property. The equivalent steel grade of 40Cr is 40MnB, 45 MnB, 35SiMn, 42SiMn, 40MnVB, 42MnV, 40MnMoB, 40MnWB and etc.

40Cr Steel Material Chemical Composition

40Cr Mechanical Properties

• Tensile Strength: ≥ 810 MPa
• Yield Point: ≥ 785 MPa
• Impact Absorbing Energy: ≥ 47 J

What is 40Cr Steel Material Used for?

It is one of the most popular steel grades in the industry. After Q+T heat treatment, it usually is used to make parts. Such as the gears of machine tools, shaft, worm, spline shaft and etc. If it is through quenching and tempering; high-frequency quenching, it will be good choice for fittings with high hardness and wear resistance. For example, wheel gear, shaft, principal axis, crankshaft, arbor, inlet valve, bolt and etc.

Q+T Hardness

After quenching and tempering, the hardness of 40Cr is in the range of 32-36HRC, which means about 301-340 HB.

• 830℃-860℃ oil quenching: 55HRC
• 150℃ tempering: 55HRC
• 200℃ tempering: 53HRC
• 300℃ tempering: 51HRC
• 400℃ tempering: 43HRC
• 500℃ tempering: 34HRC
• 550℃ tempering: 32HRC
• 600℃ tempering: 28HRC
• 650℃ tempering: 24HRC
• 700℃ tempering: 20HRC

40Cr Steel vs 45# Steel

The carbon content of 40Cr is lower than 45# steel. At the condition of hot-rolled, their mechanical property is almost the same. But the price of 40Cr is higher than 45# steel about a half. So if your budget is not high, you maybe need to choose the 45# steel.