Casting and forging: what are the main differences?
Before explaining what the casting and forging processes are, as well as the main characteristics of each, we must first clarify the nature of the two main materials usually used in these processes—iron and steel.
Iron (Fe) is one of the most abundant metals in the earth’s crust,
surpassed only by aluminum (Al). However, pure iron (that which has a purity
greater than 9.5%) does not have many applications and often requires alloys,
both metal and nonmetal, to give it different properties. It is also important
to keep in mind that the popular meaning of the term “iron” does not always
refer to pure elemental iron, but rather usually to an alloy of iron.
The main differences between cast iron and steel
One of the most striking differences between steel and iron lies in its composition—specifically, in the amount of carbon present in the alloy. Iron contains a little more than 2% carbon by weight. However, to produce steel, carbon levels must be reduced to between 0.008% and 2%. Cast iron has a low melting point, whereas steel must be melted at a higher temperature. The lower melting point of cast iron and the ease with which it flows are two key reasons this material is most often used in the casting of a wide variety of products.
Cast iron cannot be welded reliably due to its high carbon content, which would cause a brittle weld. Therefore, this material does not provide the strength and pipeline connectivity that are imperative for high-pressure and high-temperature applications. In these cases, steel is the best option.
Steel has unbeatable capabilities to cope with both casting and forging processes. It is also an ideal material for welding, as it offers greater strength and resistance than cast iron, making it a perfect choice for use at high pressures and temperatures. The most common steel alloy is carbon steel. However, depending on the conditions that the final product will be used under, the material may need a higher-grade alloy composition, such as stainless steel or molybdenum steel. Special alloy steels are popular due to their often higher resistance to corrosion and wear; they can also satisfy needs requiring high temperatures and/or pressures.
At ULMA Advanced Forged Solutions, we have become one of the leading manufacturers of flanges and high-performance forged steel products. All of our products are designed to guarantee maximum durability in all types of industries, including the petrochemical and energy industries. We also cover the entire manufacturing process, from raw material to final product. This fact allows us to be competitive while also meeting the quality and durability standards demanded by both the market and our clients.
All cast products are manufactured by transforming the material into a liquid state and then pouring it into a mold to solidify it. The material, in its liquid state, takes on the shape of the mold as it begins to cool; it is removed from the mold once the material has completely solidified.
Forging is the method by which metals are shaped through the application of high pressure, either by hammering or under the pressure of a die. In this process, the material is usually heated beforehand to make the forging action simpler and more effective. However, unlike with cast products, the material stays in a solid state throughout the process.
For many products on the market, manufacturers often specify the grade and type of material, such as ”forged steel” or ”cast steel,” to specify which process has been used during manufacturing.
At ULMA Advanced Forged Solutions, we constantly optimize all of our processes, which is why we design and manufacture our own stamps for the different references forged on our press lines. We also guarantee traceability by inputting and capturing data in each phase of the entire manufacturing process. Part of this process involves performing quality tests and applying the appropriate ranges in each operation we carry out.
Forged steel has some interesting advantages compared to cast iron. Although more complex shapes can be obtained by casting, the forging process deforms the material in a solid state, making the internal grain follow the geometry of the part. This process obtains significant improvements in the mechanical properties of the steel. In addition, the deformation pressures of the forging process can reduce or even eliminate possible internal defects in the part by closing cavities and pores.