42CrMo (grinding) surface quenching treatment

Quenching and tempering are commonly used heat treatment technologies for 42CrMo steel parts. It can not only improve the hardness and strength of the steel parts, but also improve the wear resistance and excellent balance between toughness and wear resistance, which ensures the stability of the mechanical properties of the steel parts.

42CrMo steel is an alloyed steel with medium carbon content, of which the content of carbon,Cr and Mo is 0.37-0.44, 0.9-1.2 and 0.15-0.20 respectively. It belongs to the venue of carburizing and quenching of medium carbon quenched and tempered steel. Through heat treatment, it has high strength and good comprehensive mechanical properties, including plasticity, toughness and fatigue resistance.

Grinding is one of the post processing methods for 42CrMo steel parts. After the grinding, the surface of the parts are required to be hardened and tempered. The quenching and tempering of 42CrMo steel parts is performed by carburizing and quenching method in order to obtain a stable mechanical properties.

The most commonly used method for carburizing and quenching is oil quenching. Carburizing and quenching is the chemical reaction of steel parts and the gas of carburizing composition atmosphere under high temperature. After transferring the carbon element to the surface of the steel parts, the steel parts are quenched in the oil quenching medium to form a hard and wear-resistant composite layer with good microstructure and low internal stress.

The burning temperature of 42CrMo steel is generally 850-1020℃, and the carbon potential is 0.9-1.2％. The quenching medium of 42CrMo steel is generally hot plate quenching or oil quenching. Plus tempering after oil quenching, tempering temperature of 80-220℃, for more than 8 mm thick bar, hot plate intensive tempering is the best.

After quenching, high hardness and strength is obtained, which is mainly applied to the working parts of various machinery that need wear resistance, such as cutting tools, nozzles, and so on. The quenched parts are generally tempered, that is, the parts are further heated in the tempering medium after quenching, which can reduce the hardness of the parts and can also improve the toughness and bending fatigue strength.

The Tempering temperature of 42CrMo steel is to prevent the parts from becoming too soft and too brittle. The tempering temperature should not be lower than 180℃, and the best tempering temperature is 230-240℃. After tempering, the mechanical properties of the steel parts will be stable and the toughness and resilience will be improved.

In order to ensure the quality of quenching and tempering of 42CrMo steel, these points should be noted: Firstly,to choose suitable tempering temperature and tempering time according to the requirements of mechanical properties. Secondly, to check the quenching and tempering process of the parts, observe the quenching and tempering stains, and check the hardness and mechanical properties of the parts after quenching and tempering to ensure the quality of heat treatment. Finally, to perform X-ray detector scanning and other nondestructive testing to confirm the mechanical performance of the parts.

To conclude, 42CrMo steel parts can be processed by grinding and then quenched and tempered to obtain better mechanical properties and comprehensive performance. The appropriate quenching temperature and tempering temperature should be selected according to different requirements, and strict quality control should be implemented to ensure the quality of quenching and tempering.

AISI 4140 alloy steel is a chromium-molybdenum alloy steel that is used mostly in tooling and construction. It is an alloyed steel which has a high hardness and strength. It is used in several engineering applications such as shafts, fasteners, gears, and crankshafts.

The AISI 4140 steel can be processed using conventional machine tools. It can be machined using a variety of operations including turning, milling, drilling, and grinding. After the machining process is complete, it is important to subject the material to a surface hardening treatment such as a tempering or carburizing.

Carburizing is a surface hardening process used to make the steel more resistant to wear and fatigue. This is achieved by introducing atoms of carbon, typically in the form of carbon dioxide or methane, into the alloy steel. The carbon atoms diffuse into the surface of the steel, forming a stiffer and harder layer which increases the steel’s fatigue and wear resistance.

Once the carburization process is complete, the steel should be heat treated. Heat treatment ensures that the desired properties of the alloy steel are achieved. Depending on the properties needed, the steel can be heated to different temperatures and quenched in oil or water.

Finally, the steel should be tempered to reduce the brittleness of the alloy steel. Tempering is typically done at temperatures ranging from 300 °C to 600 °C. This helps to reduce the steel’s tensile strength, thereby increasing its toughness.

The machined and heat treated AISI 4140 alloy steel is highly durable and provides excellent corrosion and wear resistance. This makes it a great choice for parts used in high stress and high temperature environments.