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 available characteristics. This is facilitated by active elements whose alloying properties cause chemical and physical processes of changes in the metal structure.
Basic alloying elements
Of great, but ambiguous importance in the doping processes is carbon. On the one hand, its concentration in the metal structure of about 1.2% helps to increase strength, hardness and cold brittleness, and on the other hand, it reduces the thermal conductivity and density of the material. But this is not even the main thing. Like all alloying elements, it is added when performing technological processing under strong temperature influence. However, not all impurities and active components are retained in the structure after the completion of the operation. Just carbon can remain in the metal, and depending on the required characteristics of the final product, technologists decide to refine the metal or maintain its current qualities. That is, they vary the carbon level through a special alloying operation.
Silicon and manganese can also be included in the list of the main elements of alloying. The first is included in the target structure in a minimum percentage (not 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 agent. These properties of alloying elements determine the basic integrity of the structure, which, even in the process of alloying, makes possible the organic perception of 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 most often used in chromium steels. In particular, with its help, the hardenability of the metal increases, and the cold brittleness threshold also decreases. Useful for building grades of steel and the use of molybdenum components. These are effective alloyed elements in steel that provide dynamic and static strength of metals, while eliminating the risks of internal oxidation. As for titanium, it is used infrequently and only for one task - grinding of structural grains in chromomanganese alloys. Calcium and lead supplements can also be called targeted. They are used for metal workpieces, which are subsequently subjected to cutting operations.
Classification of alloying elements
In addition to the very conditional separation of alloying elements into main and auxiliary, other, more accurate signs of difference are also used. For example, according to the mechanics of influencing the characteristics of alloys and steels, elements are divided into three categories:
- Influencing the formation of 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 external impurities. For example, the concentration of the same carbon or iron may be of importance. There is also a classification of elements of polymorphic transformation by the nature of the effect. In particular, elements are distinguished that allow the presence of doped ferrite in the alloy, as well as their analogues, which contribute to the stabilization of the optimum austenite content regardless of temperature.
The effect of alloying on alloys and steel
There are several areas 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 to increase strength, ductility, hardenability and hardness. Another direction of positive influence from alloying elements is the improvement of protective properties. In this regard, it is worth highlighting shock resistance, red resistance, heat resistance and a high threshold for corrosion damage. For some applications, metals are 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, it, under the condition of joining with iron, is capable of forming brittle grains that persist after alloying. As a result, the resulting alloy loses a high degree of density, and is also endowed with fragility. However, bonding 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 designed to improve the resistance of the material to external influences, then this impurity levels this group of qualities. For example, its high concentration in the structure leads to an increase in abrasion, a decrease in the fatigue resistance of a metal, and minimization of corrosion resistance.
Alloying Technology
Usually, alloying is carried out within the framework of metallurgical production and represents the introduction of additional elements into the charge or mass of the melt, which were considered above. As a result of heat treatment, chemical and physical processes of the connection of individual substances, as well as deformation, occur in the structure. Thus, alloying elements can improve the quality of metallurgical products.
Conclusion
Alloying is a complex process of changing the characteristics of a metal. Its complexity mainly lies in the initial selection of optimal recipes to achieve the desired set of properties of the workpiece. 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 reduce its thermal conductivity. The task of technologists is to develop winning combinations of elements that will make the metal part or structure the most acceptable in terms of quality in terms of use for specific purposes.