The role and influence of various elements in iron and steel

For people long-term fight with corrosion practice and the formation of the special steel stainless steel series, the most common element has a dozen, in addition to the basic elements of composition of steel iron, the most influential elements to stainless steel performance and organization has: carbon, chromium, nickel, manganese, silicon, boron, titanium, niobium, copper, cobalt, nitrogen and so on. Stainless steel apply on industrial are simultaneous presence of several or even dozens of elements, when several elements coexist in the stainless steel this one unity, their effects is much more complicated than alone, because in this case not only to consider the elements of its role, but also to pay attention to their mutual influence. Therefore, the organization is decided by the sum affecting of various elements in stainless steel.According to metal powder supplier, chromium plays a decisive role in stainless steel: the determinant of stainless steel is only one, this is chrome, every kind of stainless steels were containing a certain amount of chromium. To date, there are without chromium stainless steel. Chromium has become the main element to decision the performance of stainless steel, the fundamental reason is after add chromium as alloying elements in steel, make its internal contradictory movement is conducive to resist corrosion development. This change can be described from the following aspects: chromium improves the Fe-based solid electrode potential; chromium absorbs iron electronic to make iron passivation, passivation is the phenomenon due to anodic reaction blocked cause metal and alloy corrosion resistance performance is improved.Cobalt as an alloying element application in steel is not much, this is because the high price of cobalt and its more important use in other ways (such as high-speed steel, carbide, cobalt base alloy, steel or hard alloy ). In general stainless steel add cobalt as alloy is also not much, commonly used stainless steel adding cobalt was not intended to improve corrosion resistance but is to improve the hardness, because this kind of stainless steel is mainly used for manufacturing sections of machine tool, scissors and operation blade.Add 0.005% boron powder in high chromium ferritic stainless steel, can make in boiling 65% acetic acid corrosion performance improved. Adding trace boron ( 0.0006^ 0.0007% ) can make the austenitic stainless steel hot plasticity improving. A small amount of boron due to the formation of low melting point eutectic austenite steel, the welding hot crack tendency increases, but contains more boron ( 0.5 ~ 0.6% ), it can prevent hot cracking. Because when containing 0.5^0.6% boron, boride phase formation of austenite weld of tissue, can lower melting point. When the solidification temperature molten pool below melting zone, parent material in cooling produce tension stress, due to in liquid solid, the weld metal bear, this will not cause cracks, even in near seam zone forming a crack, also can be filled in liquid - solid pool metal. Boron containing chromium nickel austenite stainless steel in atomic energy industry has a special use.Rare earth elements: rare earth elements used in stainless steel is mainly to improve the process performance. Such as adding small amounts of rare earth elements to Crl7Ti steel and Cr17Mo2Ti steel, can be eliminating the bubble caused by hydrogen and reducing the cracks in steel. Austenitic and austenitic-ferritic stainless steel with 0.02^ 0.5% rare earth element (cerium lanthanum alloy), can significantly improve the forging property. There once a containing 19.5% chromium, 23% nickel and molybdenum copper and manganese austenite steel, due to thermal processing performance can only produce castings in the past, after adding rare earth elements can be rolled into various sections.Source:http://www.mhcmp.com