Solidification shrinkage of steel ingot
Steel ingots are formed by pouring molten steel into a mold, storing it at high temperatures, and cooling it to room temperature. During this cooling process, the metal undergoes a transformation from liquid to solid and experiences a volume change known as solidification shrinkage. Solidification shrinkage is important in terms of metal processing and performance, as it can have an effect on the shape and dimension of the metal object after cooling.
The solidification of metal is a process in which metal is transformed from its molten state to a solid state. This is accompanied by a decrease in the volume of the metal, due to the increase in the density of the atoms as they undergo the transition from the liquid state to the solid state. This phenomenon is known as solidification shrinkage. Shrinkage during solidification is a result of the decrease in volume of the solid metal due to a change in the atomic structure of the material.
The amount of shrinkage that occurs during solidification can vary depending on the type of alloy and the cooling rate of the metal. For example, steels that are cooled very quickly would experience a smaller amount of shrinkage when compared to those that are cooled more slowly. Generally, it is expected that low alloy steels, such as mild steels, will experience the greatest amount of shrinkage. On the other hand, high alloy steels, such as stainless steels, tend to experience less shrinkage due to their higher alloying elements which hinder the shrinkage process.
The size and shape of the steel ingot itself can also affect the amount of shrinkage experienced during solidification. Steels which are casted in large blocks, such as slab or bloom ingots, will have to contend with more complicated shrinkage characteristics than those casted in smaller sizes, such as billet ingots. The larger ingots tend to experience a greater amount of internal shrinkage due to the differences in cooling rates in different parts of the metal. Consequently, when the ingot is cut, internal residual stresses are not only generated, but also need to be taken into account when considering the dimensional accuracy of the metal.
In addition to the effects of the alloy type and the ingot size, the cooling rate of the molten metal can also affect the amount of shrinkage that occurs. Slower cooling rates can result in higher shrinkage levels due to the increased number of phases within the metal matrix. Quenching is a process of rapidly cooling the metal and can be used to reduce the amount of shrinkage experienced by the metal during solidification.
Overall, steel ingots undergo a decrease in volume during the solidification process, known as solidification shrinkage. The scale of this shrinkage is affected by the alloy type, the size of the ingot, and the cooling rate. It is beneficial to have an understanding of the effects of these three factors in order to better control the dimensional accuracy of steel ingots during the manufacturing process.
