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The process of alloying is used to change the chemical composition of steel and improve its properties over carbon steel or adjust them to meet the requirements of a particular application. Benefits of Steel Alloying Agents: Different alloying elements each have their own effect on the properties of steel. 1  Some of the properties that can be improved through alloying include: 2  Stabilizing austenite: Elements such as nickel, manganese, cobalt, and copper increase the temperatures range in which austenite exists. However, whether present as a residual element or added deliberately as an alloying element, the effects of N in steel are significant. N is an important and inexpensive alloying addition to steels. In recent years there has been an increasing demand to reduce and control the amount of dissolved gases in steel. In case of N being used as a deliberate alloying element in steels, N is added to liquid steel in the form of nitrogen bearing alloying additions or as gaseous nitrogen itself. Nitriding alloys are alloy steels with nitride-forming elements such as aluminum, chromium, molybdenum and titanium. History. Systematic investigation into the effect of nitrogen on the surface properties of steel began in the 1920s. Investigation into gas nitriding began independently in both Germany and America. The process was greeted with enthusiasm in Germany and several steel grades were developed with nitriding in mind: the so-called nitriding steels. Nitrogen and steel properties. Nitrogen can influence steel properties either in a detrimental or beneficial way depending on the presence of other elements in the steel, the form and quantity of nitrogen, and the required behavior of the steel. Normally most of the steels need nitrogen at the minimum level. Duplex stainless steels have a mixture of austenitic and ferritic grains in their microstructure; hence they have a “duplex” structure. This effect is achieved by adding less nickel than would be necessary for making a fully austenitic stainless steel. Salt bath nitriding. In salt bath nitriding the nitrogen donating medium is a nitrogen-containing salt such as cyanide salt. The salts used also donate carbon to the workpiece surface making salt bath a nitrocarburizing process. The temperature used is typical of all nitrocarburizing processes: 550–570 °C. Numerous sources of nitrogen exist during the melting, ladle processing and casting operations of steel. Sources of nitrogen in oxygen steelmaking include hot metal, the scrap, impurity nitrogen in oxygen and the nitrogen used as a stirring gas. Nitrogen pickup from the atmosphere can occur during steel for at least 15 min after the addition of potassium bisulfate. Brown [4] describes a pro­ cedure for the determination of total nitrogen in steel wherein the steel is dissolved in a mixture of diluted sulfuric and phosphoric acids, metallic selenium is added, and, after the removal of water, Fig 4 Effect of nitrogen on strain ageing index of steel. Effect during welding – Nitrogen generally affects the toughness of the heat affected zone (HAZ) of welded steel. Since the weld metal should not be weaker in a welded structure, the role of nitrogen is important. The loss of toughness is normally known as HAZ embrittlement.

effect of nitrogen in steel