When we talk about stainless steel, chromium is often mentioned first because it provides basic corrosion resistance. And nickel, this seemingly supporting but actually crucial role, truly elevates stainless steel from “stainless” to the “excellent” level.
Nickel can significantly enhance the thermodynamic stability of stainless steel, making it not only have better rust resistance and resistance to oxidizing media than ferritic, martensitic and other types of stainless steel with the same chromium and molybdenum content.
With the increase of nickel content, the performance of stainless steel in resisting reducing media is further improved. More importantly, nickel is the “only crucial element” that enhances the resistance of austenitic stainless steel to transgranular stress corrosion in many media.
The influence of nickel on the mechanical properties of austenitic stainless steel is mainly determined by its effect on the stability of austenite.
Chromium-nickel austenitic stainless steel with a stable austenitic structure has excellent toughness (including extremely low-temperature toughness), and thus can be used as low-temperature steel.
Nickel can also significantly reduce the cold working hardening tendency of austenitic stainless steel. This is mainly due to the increased stability of austenite, which reduces or even eliminates the martensitic transformation during cold working.
Nickel reduces the cold working hardening rate of austenitic stainless steel, and its effect on lowering the steel’s room temperature and low-temperature strength while enhancing its plasticity determines that an increase in nickel content is beneficial to the cold working formability of austenitic stainless steel.
To obtain a single austenitic structure, when the steel contains 0.1% carbon and 18% chromium, the minimum nickel content required is approximately 8%, which is the basic composition of the most famous 18-8 chromium-nickel austenitic stainless steel.
An appropriate nickel content can improve the weldability of stainless steel, reduce the tendency of hot cracking during welding, and ensure the corrosion resistance of the joint after welding.
Understanding the nickel market is crucial for the stainless steel trade. At present, the global stainless steel market is undergoing profound changes, with Asian supply dominating and the impact of Western trade barriers being significant.
Indonesia has become the absolute engine driving the growth of global nickel-iron (NPI) supply. Its new production lines and stable cost advantages have continuously driven up output.
The stainless steel industry remains the absolute main consumer of primary nickel. It is estimated that by 2030, stainless steel will consume 72% of the world’s primary nickel, and its market position far exceeds that of emerging fields such as battery materials.