The alloy steel Welded Pile of 20# Carbon Alloy Steel (Manually Arc Welding) is a kind of alloy steel which is a combination of alloy chromium and carbon, and its application has been used in heavy industries such as shipbuilding, construction and transportation. This article will discuss the microstructure of the Welded Pile of 20# Carbon Alloy Steel (Manually Arc Welding), which will present the type of microstructure, the proportion of different microstructures, and the influence of welding on the microstructure.
The type of microstructure in the Welded Pile of 20# Carbon Alloy Steel (Manually Arc Welding) can be divided into four types: austeninated ferrite structures, Bainite structures, martensite structures, and pearlite structures. The formation of these structures is the result of the temperature during welding and the metallurgical reactions during welding. The austeninated ferrite structures form when steel is heated to just below the critical temperature in welding. During welding, carbon atoms are stayed at the grain boundaries of metals, resulting in the form of an excellent combination of strength, toughness, and wear resistance; however, this structure is easily tempered by heat treatment. The Bainite structures form when the steel is cooled from quenching to below the critical temperature. During cooling, the carbon atoms are distributed in the steel lattice structure and the formation of ferrite and cementite phases results in the formation of Bainite structures, and these steel alloys have a combination of high-hardness and high-toughness. The martensite structures form when steel is cooled from the critical temperature and below the martensite start temperature. Due to the high cooling rate, carbon atoms are retained in the steel lattice structure and form martensite transformation, resulting in an increase in strength and hardness. The pearlite structures form when the steel is cooled to just below the critical temperature. This is the most common microstructure found in carbon and low-alloy steels, and it is a combination of ferrite and pearlite phases. The pearlite structures are formed by the combination of the ferrite and pearlite phases, and they are suitable for applications where high fatigue strength and toughness are required.
The proportion of the different types of microstructures in the Welded Pile of 20# Carbon Alloy Steel (Manually Arc Welding) weldment depend on the welding parameters, the base material properties, and post-weld heat treatments. Generally, the proportion of austenitized ferrite structures, Bainite structures as well as martensite and pearlite structures tend to increase with decreasing cooling rates during welding. With increasing welding parameters, such as the welding speed, or increases in heat input, the proportion of martensite and pearlite structures tends to decrease while the proportion of austenitized ferrite structures and Bainite structures increases. On the other hand, with post-weld heat treatments, the proportion of martensite and pearlite structures can be increased.
The microstructure of the Welded Pile of 20# Carbon Alloy Steel (Manually Arc Welding) has a significant effect on the weldment’s mechanical properties. In general, the weldment with mostly austenitized and Bainite structures is suitable for applications requiring high strength, good wear resistance and good fatigue strength. On the other hand, the weldments with a higher proportion of martensite and pearlite structures are suitable for applications requiring higher toughness and fatigue strength.
In conclusion, the Welded Pile of 20# Carbon Alloy Steel (Manually Arc Welding) has four different types of microstructure: austenitized ferrite structures, Bainite structures, martensite structures, and pearlite structures, and their proportion varies according to the welding parameters and post-weld heat treatments. These microstructures have a significant effect on the mechanical properties of the weldment, and they can be tailored to suit the specific application requirements.
