Metallographic diagram of granular bainite 38CrMoAl (liquid steel)

Metallurgic Features of 38CrMoAl Alloy Steel

The 38CrMoAl alloy steel is a type of steel alloy known for its high hardness, wear resistance and toughness, found in a variety of applications from automotive and tool making to production of steel wire and plastic molds. This alloy steel is considered to be one of the most popular, reliable and cost-efficient alloys for many engineering applications including, but not limited to, automotive components and components for the aerospace and defense industries. In addition to its high performance characteristics, it is also known for its attractive dark gray finish and superior impact resistance capabilities. Furthermore, it offers excellent corrosion protection and strong weldability.

This alloy is particularly popular in automotive and aerospace engineering since it offers exceptional levels of strength, wear resistance and toughness, while allowing for minimized weight. The alloy is generally composed of chromium, molybdenum, aluminum, sulphur, silicon and manganese. When the metal is alloyed with aluminum, it is known as AISI 38CrMoAl steel, which modifies the corrosion resistance and strength of the alloy significantly.

This alloy is fabricated in the form of semi-finish and finished products. Generally, the common heat treatments of 38CrMoAl alloy steel are annealing, normalizing, carburizing hardening, tempering, quenching and nitriding. The annealing and normalizing processes serve to soften the metal and relieve stresses generated during hardening processes. Carburizing in particular is performed to enhance the toughness and wear resistance of the alloy; otherwise, the alloy exhibits good formability, ductility, workability and machinability properties.

The microstructure of the 38CrMoAl alloy steel consists primarily of ferrite and pearlite, with a small amount of free ferrite, spheroidized carbides and bainite. Ferrite and pearlite are the primary constituents of the alloy and are responsible for most of its strength and increased wear resistance. The alloy can also show a degree of secondary hardening that is generally due to the formation of bainite, which further provides the alloy with improved wear-resistance properties.

The mechanical properties of 38CrMoAl alloy steel depend on its final heat treatment process. It is typically offered in both hot-rolled and cold-rolled condition and possess a tensile strength range of between 1060 - 1210 MPa (depending on its temper and thickness). The alloy also has good creep and fatigue strength characteristics, as well as impact toughness and notch ductility.

The 38CrMoAl alloy steel is a widely used deposit for gas tungsten arc welding (GTAW) processes due to its exceptional weldability. It is usually used for a variety of welding operations, such as maintenance and repair welding, fabrication and production welding. This makes it a preferred choice for many industries due to its weldability, strength and high fatigue strength.

As the microstructure of the 38CrMoAl alloy steel consists of primarily ferrite and pearlite, it is therefore classified as a pearlite-ferrite type of steel. The fine grained microstructure is advantageous for weldments, offering improved toughness and greater resistance to stress corrosion cracking. Typical grain size is between 5 and 13.5microns.

In conclusion, the 38CrMoAl alloy steel is a popular, reliable and cost-efficient choice for automotive and aerospace applications, thanks to its impressive mechanical properties, excellent corrosion resistance and strong weldability. It is typically produced in semi-finished and finished form, and can be fabricated into a number of parts and components for various applications. The microstructure of the alloy consists principally of ferrite and pearlite, offering the alloy significant levels of strength and increased wear resistance. The typical grain size is also an indication of its improved weldability and increased toughness.

The Microstructure of 38CrMoAl Steel

38CrMoAl steel, also known as liquid steel, is a high-strength alloy used in many applications. It is composed mainly of chromium and molybdenum and also contains trace amounts of aluminum and other elements. The final structure of the steel depends on the composition, temperature, and cooling rate of the alloy during production.

In this particular case, the microstructure of the 38CrMoAl steel was examined in order to measure its mechanical properties. The microstructure was viewed on a metallographic mount under an optical microscope and revealed a highly homogenous grain structure. Primarily, the grains appeared polygonal in shape and distributed fairly evenly throughout the mount, with a uniform appearance.

Furthermore, small particles of bainite could be detected in various parts of the mount. These present in the form of needle-like particles that often remain suspended in liquids. Bainite particles are known to form through the transformation of austenite, either in the presence of high cooling rates or through isothermal transformation processes. The formation of these particles can highly influence the mechanical behavior of the steel.

Based on the microstructure, it can be concluded that the 38CrMoAl steel exists as a primarily polygonal grain structure with needle-like particles distributed throughout. In addition, it can be assumed that the bainite particles were formed during the cooling process of the alloy during production, likely due to its high cooling rate. Thanks to this unique microstructure, the 38CrMoAl steel is capable of achieving remarkable mechanical properties.