42CRMO is a commonly used alloy structural steel with excellent mechanical properties and heat treatment plasticity, which is widely used in the field of manufacturing mechanical parts and construction machinery. Heat treatment is one of the important processes for 42CrMo to obtain excellent performance. In this paper, we will introduce the characteristics and applications of 42CRMO from two aspects: heat treatment process and hardness. 42CRMO is a high-strength alloy structural steel with good comprehensive mechanical properties, which is suitable for manufacturing parts and equipment with high strength, high wear resistance, high corrosion resistance and high hardness.
Due to its excellent mechanical properties and heat treatment plasticity, this material has a wide range of applications in many industrial fields, such as construction machinery, auto parts, petroleum machinery and aerospace. The heat treatment process has a significant impact on the performance of 42CrMo. The heat treatment process of 42CrMo is a key factor in its performance, and different heat treatment processes will result in different hardness, strength and toughness of the material.
The heat treatment process of 42CRMO refers to heating the steel to a certain temperature, and after the heat preservation and cooling process, the phase transformation of the steel is carried out, thereby changing its microstructure and properties. The heat treatment process of 42CRMO mainly includes four common processes: annealing, normalizing, quenching and tempering.
The main heat treatment process and efficacy of 42CRMO steel pipe:
Annealing: Used to relieve internal stresses and improve processability.
Normalizing: Improves the strength and hardness of the material.
Quenching: Improving the strength, hardness, and wear resistance of materials.
Tempering: Reduces the brittleness of the material and improves toughness.
The delivery hardness of 42CRMO is generally 240-270HB. After normalizing treatment, the hardness can be increased to 280-320HB. The hardness after quenching can reach 50-55hrc, while the hardness after tempering is about 50hrc. Different heat treatment processes correspond to different hardness, strength and toughness.
Hardness change of 42crmo steel pipe under heat treatment:
The hardness of 42CrMo without any treatment is about 180-200HB.
The hardness of annealed 42CrMo can reach HB220-230.
The hardness of 42CrMo after normalizing treatment can reach 250-300HB.
The hardness of 42CrMo after quenching + tempering treatment can reach about 280-340HB.
Quenching and tempering is to heat 42crmo to 850-880 degrees Celsius, keep it warm for a period of time and then cool it with water or oil. This heat treatment method allows 42CrMo to achieve a homogeneous martensitic structure, thereby improving its hardness and strength while maintaining high toughness. The quenched and tempered 42CRMO has high tensile strength and yield strength, which is suitable for the manufacture of parts that require high strength and fatigue resistance.
Quenching + tempering is to heat 42crmo to 860-880 degrees Celsius, keep it warm for a period of time and then quench (usually water cooling). The steel is then heated to a temperature below the critical temperature of the steel for tempering. This heat treatment method enables 42CrMo to obtain a uniform and fine martensitic structure, improving its hardness and toughness. After quenching + tempering, 42crmo has a higher hardness, and the wear resistance and impact resistance are also improved, which is suitable for manufacturing parts that require wear resistance and impact resistance.
After heat treatment, the hardness of 42CrMo is usually between 260-300HB, and the hardness range may vary depending on the heat treatment process and the shape of the workpiece. The quenched and tempered 42CRMO has a high hardness, which can meet the requirements of many mechanical parts. The 42CRMO after quenching + tempering treatment has a lower hardness, but has good toughness, which is suitable for manufacturing parts that require high strength and high toughness.
Due to its good mechanical properties and heat treatment plasticity, 42CRMO has been widely used in construction machinery, auto parts, petroleum machinery, aerospace and other fields. For example, when manufacturing heavy-duty parts such as engine crankshafts, transmission gears, and wind turbine spindles, the choice of 42CRMO can ensure the strength and life of the parts.
As a commonly used alloy structural steel, 42CRMO can obtain different hardness and properties through heat treatment process. Quenching and tempering and quenching + tempering are two common heat treatment processes, and choosing the right process according to different use requirements can meet the performance requirements of parts. The hardness of 42CrMo is typically between 260-300HB and has excellent mechanical properties and heat treatment plasticity, making it suitable for a wide range of applications.
42CRMO steel is an ultra-high strength steel, with high strength and toughness, good hardenability, no obvious tempering brittleness, high fatigue limit and multiple impact resistance after quenching and tempering treatment, and good low-temperature impact toughness. The steel is suitable for manufacturing large and medium-sized plastic molds that require a certain strength and toughness.
High strength, hardenability, good toughness, small deformation during quenching, high creep strength and lasting strength at high temperature. It is used to manufacture forgings that require higher strength and quenched and tempered cross-section than 35CRMO steel, such as large gears for locomotive traction, supercharger transmission gears, pressure vessel gears, rear axles, connecting rods and spring clamps with great load, and can also be used for oil deep well drill pipe joints and salvage tools below 2000m, and can be used for molds of bending machines.
10 kinds of 42CrMo heat treatment methods and their corresponding hardness cases:
no.1 annealing 760 10 annealing, furnace cooling to 400 air cooling, corresponding hardness: HB 220-230.
no.2 Normalize 860 10 Normalize, air cooled out of the oven, corresponding hardness: HB 250-300.
no.3 Quenching+tempering 840 10 Quenching or oil (depending on the complexity of the product), 680-700 tempering, corresponding hardness: HB<217.
no.4 Quenching+tempering 840 10 quenching, then 470 tempering, corresponding hardness: HRC41-45.
no.5 Quenching+tempering 840 10 Quenching, then 480 tempering, corresponding hardness: HRC35-45.
no.6 Quenching+tempering 850 quenching oil, then 510 tempering, corresponding hardness: HRC38-42.
no.7 Quenching+tempering 850 quenching, then 500 tempering, corresponding hardness: HRC40-43.
no.8 Quenching+tempering 850 quenching, then 510 tempering, corresponding hardness: HRC36-42.
no.9 Quenching+tempering 850 quenching, then 560 tempering, corresponding hardness: HRC32-36.
no.10 Quenching+tempering 860 quenching, then 390 tempering, corresponding hardness: HRC48-52.
42Crmo Heat Treatment Process Steps:
The heat treatment of 42CrMo alloy steels typically includes steps such as pre-heating, austenitization, cooling, and tempering.
1.Pre-heating.
Pre-heating is an important part of the heat treatment process, the main purpose is to make the workpiece reach a uniform temperature, so as to avoid the pre-stress afterburner heat or temperature change shape in the austenitization process. The general control is between 700 and 800, and the time depends on the size of the workpiece and the amount of furnace loaded. During the pre-heating process, the temperature should be raised slowly to avoid cracks or deformation of the workpiece.
2.Austenitization.
Austenitization is an important part of the heat treatment process, the main purpose is to dissolve all or part of the ferrite in the steel, so as to obtain the temperature and energy of the mechanical machinery of Liang Aohao in the cooling process. Generally, it is controlled between 900 and 950, and the holding time is quantified according to the size of the workpiece and the Austrian furnace body. The temperature in the furnace should be kept uniform to avoid stress or deformation of the workpiece.
3.Cooling.
Cooling is an important part of the heat treatment process, the main purpose is to obtain the desired mechanical properties. The cooling method is generally oil cooling or water cooling, and the cooling rate should be controlled within the appropriate range, so as to avoid the root and avoid the rapid growth of cracks in the cold parts. Different mechanical properties are obtained.
4.Tempering.
Tempering is the last link in the heat treatment process, the main purpose is to eliminate the residual stress inside the workpiece and improve the toughness and stability of the workpiece. The tempering temperature is generally controlled between 500 and 650, and the holding time depends on the size of the workpiece and the amount of furnace loading. During the tempering process, it is necessary to cool down slowly to avoid cracks or deformation of the workpiece. After tempering, air cooling or furnace cooling should be carried out.