Effect of alloying elements
To improve the corrosion resistance, strength and technological properties, various alloying elements are introduced into the composition of metals. For alloying steels use vanadium, tungsten, manganese, nickel, niobium, titanium, chromium, etc. Zinc additives in copper and bronze — increase strength, ductility, corrosion resistance. Small additions of cadmium to copper increase the wear resistance of wires. When titanium is doped with molybdenum, the temperature limit of the operation of the alloy will double by changing its crystal structure. Doping involves the introduction of one or more elements that give alloys unique properties.
The alloying of structural steel significantly increases its strength. The main constituent in the structural steel is ferrite. Its alloy structure is 90%. Doping elements, dissolving in the ferrite, strengthen the structure. The hardness of the alloy is stronger than others by increasing silicon, manganese and nickel. Molybdenum, tungsten and chromium are weaker. Most alloying elements, strengthening the structure and having little effect on ductility, reduce the toughness (with the exception of nickel).
How Hardening Works
Doping strengthens ferrite. Alloying elements increase the hardness, strength and toughness, increase the stability of austenite, hardenability, etc. So for steels that serve for the production of turbines, boilers, etc., corrosion resistance and heat resistance are of particular importance. Alloying elements can dissolve in ferrite or austenite, form carbides, give intermetallic compounds, settle in the form of inclusions, without interacting with ferrite and austenite or with carbon.
Depending on the peculiarities of the interaction of the alloying additive with iron or carbon, the properties of the steel are determined. Ferrite can dissolve all elements to some extent. Dissolution of alloying additives in ferrite allows hardening of steel without heat treatment. In this case, both the ultimate strength and hardness increase, and the toughness usually decreases. All elements that dissolve in the iron affect the stability of austenite and ferrite. Critical points of alloyed steels are shifted under the influence of the quantity and quality of alloying additives. Therefore, when selecting the quenching, normalization, annealing, and tempering mode, the offset of the critical points should be taken into account.
Mn and Si
They are technological impurities and are introduced into the process of steel smelting for deoxidation. The share of Mn in steel is up to 2%. It is distributed between cementite and ferrites and significantly increases the cold-brittleness threshold, hardenability and yield strength, but makes the steel sensitive to overheating. Therefore, to carve grain into the alloy, along with manganese, carbide-forming elements are introduced. Since in all steels the manganese content is approximately the same, its effect on the change in the properties of steel of different composition is insignificant. It increases the strength of steel without changing the ductility.
Mn and Si are found in virtually any steel. Silicon, along with manganese and aluminum is the main deoxidizer. Mn is also needed to «bind» the sulfur in the steel and eliminate redness. Additives of these elements usually do not exceed 0.17 — 0.37% Si, 0.3−0.7% Mn and about 0.03% Al. Within these limits, they are considered technological impurities and are not alloying elements. A special introduction of these additives above the specified level to give the steel certain properties will already be doping.
It is not a carbide-forming element, and its share in steel is usually less than 2%. It significantly increases the yield strength and strength of the steel, and when the content exceeds 1%, it reduces viscosity, ductility and increases the cold-brittle threshold. Silicon is not structurally detected, since it usually dissolves in ferrite, except for that part of silicon, which in the form of oxide did not have time to float into the slag and remained in the metal in the form of inclusions.
In the warehouse of Electrovek-Steel LLC there is a wide range of high-quality rolled metal of standard and non-standard sizes. We supply products from alloyed alloys in retail and wholesale. All products are certified for compliance with the requirements of standards and technical conditions of operation. In the certificate, the manufacturer, number of drawings and product names, alloy grade, melting number, parts, chemical composition, mechanical properties and results of additional tests were noted. The implementation of orders — in the shortest possible time. Discounts are given to wholesale buyers.