Effect of Alloying Elements on the Mechanical Properties of Steel
Improve the strength of steel is one of the main purpose of adding alloying elements. To improve the strength, we should seek to increase the resistance to dislocation motion. Metal strengthening mechanism of solid solution strengthening, dislocation strengthening, fine grain strengthening, second phase (precipitation and dispersion) strengthening. Strengthening the role of alloying elements took advantage of the strengthening mechanism.
1. Impact on the mechanical properties of the steel in the annealed condition
Structural steel basic phase in the annealed condition is ferrite and carbides. Alloying elements dissolved in ferrite, forming an alloy ferritic, rely on solid solution strengthening effect, improve the strength and hardness, but lower ductility and toughness.
2. The impact on the mechanical properties of the steel in the annealed condition
Due to the addition of alloying elements reduce the carbon content of the eutectoid point, the C curve to the right, so that the proportion of the organization increases pearlite, pearlite lamellar distance decreases, which increases the strength of steel, plastic decline. But in the annealed condition, Alloy no great advantage. Since the supercooled austenite stability increases, alloy obtained in normalized condition lamellar distance smaller pearlite, or bainite or martensite, thereby greatly increasing the strength. Greater strengthening effect Mn, Cr, Cu, and Si, Al, V, Mo, etc. in general the content (e.g., the actual content of the general structural steel) under the influence is small.
3. Impact on the mechanical properties of quenched and tempered steel of state
Alloying elements on the quenching and tempering of steel to strengthen the role of the state in the most significant, because it makes full use of all four strengthening mechanisms. The most economical and most effective method of strengthening the integrated steel quenched martensite formation, precipitation of carbides during tempering, resulting in a strong second phase strengthening while the toughness is greatly improved, it is tempered martensite and its .
Alloying elements in steel, the primary objective is to improve the steel hardenability to ensure easy access to martensite during quenching. Second is to improve the stability of steel tempering, martensite is maintained to a higher temperature, the hardened steel carbide precipitation during tempering, more uniform and stable. Thus, under the same conditions, the alloy has a higher strength than carbon steel.