420 is a chromium-alloyed stainless steel that is highly valued for its versatility and excellent mechanical properties, making it a popular choice for plastic mould applications. This steel is characterized by its exceptional polish ability, enabling it to achieve a mirror-like surface finish, which is crucial for producing high-quality moulds. Additionally, it offers excellent hardenability, with the ability to reach high levels of hardness after appropriate heat treatment, making it suitable for applications requiring durability and wear resistance. One of the key advantages of 420 stainless steel is its reasonable corrosion resistance, attributed to its chromium content.