What is the difference between 40CR and 40MN? What is their respective hardness after heat treatment

40Cr is an alloy structural steel, and chromium (Cr) is added to improve hardenability, which is generally used to do quenching and tempering treatment.

The workpiece, after quenching and tempering treatment, the material can have good comprehensive mechanical properties, the general hardness of quenching and tempering treatment is about HRC30, if the hardening treatment hardness can reach HRC50 60;

40mn is a carbon steel with a higher manganese content.

Commonly known as manganese steel. The addition of manganese (Mn) is mainly to improve the strength of the material, and it is generally used directly without heat treatment.

The use and quality are different, about 50 60hcr after 40cr treatment.

40cr-high-quality alloy structural steel, a high-performance mechanical part commonly used for quenching and tempering treatment, belongs to quenched and tempered steel.

40mn - High quality carbon steel with higher manganese content, commonly known as manganese steel, has better mechanical properties, and is generally directly made as mechanical parts.

Both materials belong to high-quality carbon structural steel, the main difference is that the carbon content is different, and the other components are the same. The difference in carbon content is directly related to the properties of the material.

The plasticity of 40mn is medium and the machinability is good, but the weldability is poor. It should be used after quenching and tempering. Suitable for hinges. Bolt. Nut. screws, etc., mandrel. Gears, which are also used in the manufacture of bolts, nuts, levers, etc., in medium-sized machinery.

40mn carbon structural steel can be used in the normalized state, as well as in the quenched and tempered state. The cutting performance is good, the plasticity is medium during cold deformation, and the welding performance is poor. It is used to manufacture parts that are subjected to fatigue loads, such as shaft rolls and screws and nuts that work under high stress.

After heat treatment, the weldability is low, it has overheating sensitivity and tempering brittleness, and it is easy to crack when water quenched. Suitable for fatigue-resistant parts. Crankshaft.

Roller. Axis. Connecting rod.

After 40cr heat treatment, it can reach a hardness of about 50 60hcr, while 40mn cannot be heat treated, which will cause the material to deform.

It's bullshit upstairs!

Your sister's! If the hardness of 40cr Nima is below 30hrc, what do you need to do with 40cr!

All you want is its hardness! Generally, gears require a surface of more than 55hrc, and the heart is only about 30hrc!

Nima's! Upstairs, I don't know how to pretend to understand, and 40mn is generally hardness at 40 45hrc, and 40hrc is generally taken into account toughness.

40cr belongs to low hardenability alloy quenched and tempered steel, steel grade: 40cr annealing hardness hbs: 207 end quenching test temperature |Normalize:

860 880 end quenching test temperature |End quenching: 850 5 Hardenability zone range: the upper limit is HRC| at the following distance (mm) from the quenching end:

59 hrc|at the following distance (mm) from the quenching end59 hrc|at the following distance (mm) from the quenching end: 58 hrc|at the following distance (mm) from the quenching end6:

57 HRC|at the following distance (mm) from the quenching end9:54 HRC| at the following distance (mm) from the quenching end12:48 HRC|at the following distance (mm) from the quenching end15:

43 HRC|at the following distance (mm) from the quenching end18:41 HRC|at the following distance (mm) from the quenching end21:39 HRC| at the following distance (mm) from the quenching end24:38

The hardness after quenching and tempering 40CR is about between HRC32-36, that is to say, about HB301-340. 40cr steel quenched and tempered.

It has good comprehensive mechanical properties.

Good low-temperature impact toughness.

and low notch sensitivity. The hardenability of the steel is good, it can be hardened to 28 60mm when water quenched, and it can be hardened to 15 40mm when oil quenched. In addition to quenching and tempering, this steel is also suitable for cyanide and high-frequency quenching.

Dispose. The machinability is good, when the hardness is 174 229HB, the relative machinability is 60%. This steel is suitable for making medium-sized plastic molds.

40cr characteristics:

Medium carbon quenched and tempered steel, cold heading die steel. The steel is moderate, easy to process, and can obtain certain toughness, plasticity and wear resistance after proper heat treatment. Normalize:

It can promote spheroidization of the structure and improve the cutting performance of blanks with hardness less than 160hbs. Tempered at a temperature of 550 570, the steel has the best comprehensive mechanical properties. The hardenability of this steel is higher than that of 45 steel.

It is suitable for high-frequency quenching, flame quenching and other surface hardening treatments.

The above content reference: Encyclopedia-40cr

Quenching to obtain the whole martensitic has a critical quenching speed, 45 steel critical quenching speed is larger, requiring a strong cooling medium with strong cooling capacity, so water is commonly used.

Due to the addition of CR to 40CR, the C curve is shifted to the right, and the critical quenching speed is reduced, and oil quenching is possible.

Due to the difference in the cooling rate of the surface and core of the workpiece (fast surface, slow core), each steel grade has a critical quenching diameter for different quenching media (i.e. to obtain full martensitic), so it is not possible to generalize whether CR can be quenched with oil, but should be based on the size of the workpiece (cross-sectional size).

Critical hardened diameters are available in the manual.