Influence Factors of Decarburization in Forging
Introduction
Decarburization is a condition where the carbon content of steel has been reduced due to heating. Decarburization occurring during forging is a common problem, and it can have serious effects that have a negative impact on the quality, performance and durability of steel parts. This paper will discuss the influence factors of decarburization in forging of steel, and the proper standards for successful forging operation.
Influential Factors
Decarburution occurs during forging when low-carbon steel is heated to temperatures that cause the carbon to oxidize and move into the surrounding atmosphere. The effect of this process is a reduction in steels carbon content and a weakening of the material. The most influential factors on the rate of decarburization include time, temperature, gas atmosphere and surface area.
Time - Decarburization increases as temperatures become higher and time increases. Longer times at higher temperatures significantly increase the rate of decarburization.
Temperature - The rate of decarburization is significantly related to the temperature at which it is heated. The temperature range at which significant decarburization becomes a problem is between 773 K (500 °C) and 1273 K (1000 °C).
Gas Atmosphere - Any air that comes into contact with heated steel will initiate the process of oxidation and decarburization. Controlling the rate of oxidation is typically done by controlling the gas atmosphere. Carbon dioxide is usually used to slow or prevent oxidation from occurring.
Surface Area - The surface area exposed to the atmosphere has an effect on the rate of decarburization. Increasing the surface area by using a finer grained material or preheating the workpiece will increase the rate of decarburization.
Proper Standards for Successful Forging Operation
In order to obtain the desired properties from forged steel parts, it is important to maintain the proper standards for successful forging operations.
Time - As mentioned previously, time is a key factor that influences the rate of decarburization. Ideally, forging should be kept to the minimum time needed to achieve the desired shape and properties.
Temperature - Decarburization occurs when the steel is heated to temperatures between 773 K (500 °C) and 1273 K (1000 °C). When the steel is heated beyond this range, the rate of decarburization increases significantly.
Gas Atmosphere - During forging, the presence of oxygen will accelerate the decarburization process. Controlling the ambient atmosphere is essential to prevent decarburization. Carbon dioxide or nitrogen can be used to create an inert atmosphere.
Surface Area - Minimizing the surface area of the workpiece by using a coarser grained material or by preheating the workpiece will reduce the rate of decarburization.
Conclusion
Decarburization is a common problem during forging, and it can lead to serious problems that have a negative impact on the quality and performance of steel parts. This paper has discussed the influence factors of decarburization in forging of steel and the proper standards for successful forging operation. Controlling the rate of decarburization is essential for producing high-quality steel parts, and understanding the influential factors is important for preventing this condition.
