In construction, industry and some areas of agriculture, one can observe the active use of metal products. Moreover, the same metal, depending on the scope of use, reveals different technical and operational properties. This can be explained by doping processes. A technological procedure in which the basic workpiece acquires new qualities or improves according to existing characteristics. This is facilitated by active elements, the alloying properties of which cause chemical and physical processes of changing the metal structure.
Main alloying elements
Carbon has a great but ambiguous value in alloying processes. On the one hand, its concentration in the metal structure of about 1.2% contributes to an increase in strength, hardness and the level of cold brittleness, and on the other hand, it also reduces the thermal conductivity and density of the material. But even this is not the main thing. Like all alloying elements, it is added during technological processing under strong temperature influence. However, not all impurities and active components remain in the structure after the completion of the operation. Just carbon can remain in the metaland depending on the required characteristics of the final product, technologists decide whether to refine the metal or maintain its current qualities. That is, they vary the carbon content through a special alloying operation.
Also, silicon and manganese can be added to the list of basic alloying elements. The first is introduced into the target structure in a minimum percentage (no more than 0.4%) and does not have a special effect on the change in the quality of the workpiece. Nevertheless, this component, like manganese, is essential as a deoxidizing and binding substance. These properties of alloying elements determine the basic integrity of the structure, which, even in the process of alloying, makes it possible to organically perceive other, already active elements and impurities.
Auxiliary alloying elements
This group of elements usually includes titanium, molybdenum, boron, vanadium, etc. The most prominent representative of this link is molybdenum, which is more often used in chromium steels. In particular, with its help, the hardenability of the metal is increased, and the cold brittleness threshold is also reduced. Useful for building steel grades and the use of molybdenum components. These are effective alloying elements in steel that provide dynamic and static strength to metals while eliminating the risks of internal oxidation. As for titanium, it is used infrequently and for only one task - the grinding of structural grains in chromium-manganese alloys. Supplements can also be called targetedcalcium and lead. They are used for metal blanks, which are subsequently subjected to cutting operations.
Classifications of alloying elements
In addition to the very conditional division of alloying elements into main and auxiliary, other, more accurate signs of difference are also used. For example, according to the mechanics of the impact on the characteristics of alloys and steels, elements are divided into three categories:
- Influencing to form carbides.
- With polymorphic transformations.
- With the formation of intermetallic compounds.
It is important to consider that in each of the three cases the influence of alloying elements on the properties of intermetallic compounds also depends on foreign impurities. For example, the concentration of the same carbon or iron can have a value. There is also a classification of already elements of polymorphic transformation according to the nature of the impact. In particular, elements are distinguished that allow the presence of alloyed ferrite in the alloy, as well as their analogues, which contribute to the stabilization of the optimal austenite content, regardless of temperature.
Effect of alloying on alloys and steels
There are several ways in which the quality characteristics of steel can be improved. First of all, these are physical qualities that determine the technical resource of the material. Alloying in this part allows you to increase strength, ductility, hardenability and hardness. Other direction positiveinfluence from alloying elements is to improve the protective properties. In this regard, it is worth highlighting impact resistance, red hardness, heat resistance and a high threshold of corrosion damage. For some applications, metals are also prepared taking into account electrochemical qualities. In this case, alloying elements can be used to increase electrical and thermal conductivity, oxidation resistance, magnetic permeability, etc.
Features of the influence of harmful impurities
Typical representatives of harmful impurities are phosphorus and sulfur. As for phosphorus, when combined with iron, it is capable of forming brittle grains that are preserved after alloying. As a result, the resulting alloy loses a high degree of density, and is also endowed with brittleness. However, the combination with carbon also gives a positive characteristic, improving the chip separation process. This quality facilitates machining processes. Sulfur, in turn, is an even more dangerous substance. If the influence of alloying elements on steel as a whole is intended to improve the resistance of the material to external influences, then this admixture levels out this group of qualities. For example, its high concentration in the structure leads to an increase in abrasion, a decrease in metal fatigue resistance and a minimization of corrosion resistance.
Alloying technology
Usually, alloying is carried out within the framework of metallurgical production and represents the introduction of additionalelements discussed above. As a result of heat treatment, chemical and physical processes of joining individual substances, as well as deformations, occur in the structure. Thus, alloying elements make it possible to improve the quality of metallurgical products.
Conclusion
Alloying is a complex technological process of changing the characteristics of a metal. Its complexity mainly lies in the primary selection of optimal recipes to achieve the desired set of workpiece properties. As already mentioned, the influence of alloying elements is diverse and ambiguous. The same component of the active additive can, for example, simultaneously improve the strength of the metal and degrade its thermal conductivity. The task of technologists is to develop winning combinations of elements that will make a metal part or structure the most acceptable in terms of its qualities in terms of use for specific purposes.
