There are currently more than 100 known chemical elements, and about 20 chemical elements can be encountered in steel materials commonly used in industry. For the special steel series stainless steel formed by people's long-term struggle against corrosion phenomena, there are more than a dozen most commonly used elements. In addition to iron, the basic element that makes up steel, the ones that have the greatest impact on the performance and structure of stainless steel are The elements are: carbon, chromium, nickel, manganese, silicon, molybdenum, titanium, niobium, titanium, manganese, nitrogen, copper, cobalt, etc. Except for carbon, silicon, and nitrogen, these elements are all elements in the transition group of the periodic table of chemical elements.
In fact, stainless steel used in industry contains several or even more than a dozen elements at the same time. When several elements coexist in the unity of stainless steel, their influence is much more complicated than when they exist alone, because in this case In this case, it is not only necessary to consider the role of each element itself, but also to pay attention to their influence on each other. Therefore, the structure of stainless steel is determined by the sum of the effects of various elements.1). The influence and effect of various elements on the performance and structure of stainless steel
The decisive role of chromium in stainless steel: There is only one element that determines the properties of stainless steel, which is chromium. Each stainless steel contains a certain amount of chromium. To date, there is no chromium-free stainless steel. The fundamental reason why chromium has become the main element that determines the performance of stainless steel is that adding chromium as an alloying element to steel promotes its internal contradictory movements to develop in a direction that is conducive to resisting corrosion damage. This change can be explained from the following aspects:
① Chromium increases the electrode potential of iron-based solid solution
② Chromium absorbs electrons from iron to passivate the iron
Passivation is a phenomenon in which the corrosion resistance of metals and alloys is improved due to the prevention of anodic reactions. There are many theories that constitute the passivation of metals and alloys, including thin film theory, adsorption theory and electron arrangement theory.
