Stainless steel and steel are two of the most commonly used metal alloys in the manufacture of components in a wide range of industries. Both metals are highly valued in the manufacturing world for their excellent properties, including machinability, weldability and formability. As the names of the two alloys suggest, there are some similarities between them. However, there are also distinct differences between them. This article will explore the similarities and differences between stainless steel and carbon steel.
Steel is an alloy of iron and carbon with varying amounts of other elements such as manganese, nickel, vanadium, etc. Similarly, stainless steel is an alloy of iron and carbon with other similar alloying elements. However, unlike regular steel alloys, stainless steel contains a high amount of chromium, which is the main reason for its corrosion resistance. Therefore, the main difference between stainless steel and steel is that the former contains a high amount of chromium, which increases its rust resistance and overall durability.
Stainless steel and steel are both iron alloys with similar compositions. As mentioned earlier, the differences between the two alloys mainly relate to the higher proportion of chromium in the stainless steel, which significantly enhances the corrosion resistance of the stainless steel.
During the formation of steel, there are up to 20 different alloying elements (including chromium) that can improve the mechanical properties of steel. Below are the most common alloying elements in these alloy formation processes.
The addition of chromium (in large quantities) turns steel, an iron-based alloy, into a corrosion-resistant material. Normally, iron is susceptible to corrosion in the right humidity and air conditions. However, the presence of chromium in stainless steel causes it to form a protective oxide layer – chromium oxide – when it reacts with oxygen to prevent corrosion. This process is called passivation of stainless steel and is the main reason for the alloy’s self-healing properties, making it more durable than other steel alloys. Although steel can contain chromium, the amount is usually very small, no more than 0.5%. Therefore, the chromium has little effect in preventing corrosion and instead helps to increase the hardness of the steel.
There are many different types of steel alloy. Generally speaking, steel alloys consist of metals made from iron and carbon combined with other alloying elements, as described above. So, in a very real sense, stainless steel itself is a type of steel alloy. However, in this section we will divide steel alloys into two types, based on the proportion of carbon and other alloying elements besides iron.
This type of alloyed steel has a low proportion of alloying elements, usually not more than 5% of the total alloy composition. The addition of these elements can improve the mechanical and chemical properties of the steel, but is less than that of high alloy steel. Typical alloying elements include small amounts of nickel, vanadium, copper, tungsten, boron, copper, chromium, etc.
High alloy steels have even higher alloying elements, over 5%. Therefore, we can even classify stainless steel as a high alloy steel because it contains more than 12% chromium. The higher the chromium content of these steels, the better the mechanical properties tend to be.
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