Elements that alloy. Effect of alloying elements on the properties of steel and alloys

In the construction, industry and some areas of agriculture, one can observe the active use of metal products. And the same metal, depending on the sphere of use, reveals different technical and operational properties. This can be explained by the doping process. Technological procedure, in which the base piece acquires new qualities or improves on the available characteristics. This is promoted by active elements, alloying properties of which cause chemical and physical processes of changing the metal structure.

Basic alloying elements

A large, but ambiguous value in the doping process is carbon. On the one hand, its concentration in the metal structure of about 1.2% contributes to the strength, hardness and cold-brittleness level, 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 when performing technological processing under a strong temperature effect. However, not all impurities and active components remain in the structure after the operation is completed. Just the carbon can remain in the metal and, depending on the required characteristics of the final product, the technologists decide whether to refine the metal or maintain its current qualities. That is, they vary the level of carbon content through a special alloying operation.

Also, silicon and manganese can be added to the list of basic elements of alloying. The first is introduced into the target structure in a minimum percentage (no more than 0.4%) and does not have a particular 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 cause the basic integrity of the structure, which, even during the doping process, 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 notable representative of this link is molybdenum, which is often used in chromium steels. In particular, with its help, the hardenability of the metal increases, and the cold-brittle threshold is also reduced. Useful for building grades of steels and application of molybdenum components. These are effective alloyed elements in steel, which ensure the 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 - the grinding of structural grains in chromium-manganese alloys. Calcium and lead additives can also be targeted. They are used for metal blanks, which are later subjected to cutting operations.

Classifications of alloying elements

In addition to the very conditional separation of alloying elements into basic and auxiliary ones, other, more precise, signs of difference are also used. For example, according to the mechanics of the effect on the characteristics of alloys and steels, the elements fall into three categories:

• Influencing with the formation of carbides.
• With polymorphic transformations.
• With the formation of intermetallic compounds.

It is important to take into account that in each of the three cases the effect of alloying elements on the properties of intermetallic compounds also depends on foreign impurities. For example, the value may have a concentration of the same carbon or iron. There is also a classification of the elements of the polymorphic transformation according to the nature of the effect. In particular, there are elements that allow the presence of alloyed ferrite in the alloy, as well as their analogues, which help stabilize the optimum austenite content regardless of temperature.

Effect of alloying on alloys and steels

There are several ways in which qualitative characteristics of steel can be improved. First of all, these are physical qualities that determine the technical resource of the material. Doping 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 the resistance to shock, red resistance, heat resistance and high threshold of corrosive damage. For some applications, metals are also prepared taking into account the electrochemical properties. In this case, the alloying elements can be used to increase electrical and thermal conductivity, oxidation resistance, magnetic permeability, etc.

Peculiarities of the influence of harmful impurities

Typical representatives of harmful impurities are phosphorus and sulfur. As for phosphorus, it is capable of forming brittle grains, which are preserved after alloying, under the condition of the connection with iron. As a result, the resulting alloy loses a high degree of density, and is also endowed with brittleness. However, the connection with carbon gives a positive characteristic, improving the process of chip separation. This quality facilitates the machining process. Sulfur, in turn, is an even more dangerous substance. If the effect of alloying elements on steel as a whole is intended to improve the material's resistance to external influences, then this impurity neutralizes this group of qualities. For example, its high concentration in the structure leads to increased abrasion, reduced fatigue resistance of the metal, and minimization of corrosion resistance.

The technology of doping

Usually alloying is carried out within the framework of metallurgical production and is the introduction of additional elements into the burden or mass of the melt, which were considered above. As a result of heat treatment, chemical and physical processes of compounding of individual substances, as well as deformations, take place in the structure. Thus, alloying elements allow to improve the quality of metallurgical products.

Conclusion

Doping is a complex technological process of changing the characteristics of the metal. Its complexity is mainly in the initial selection of the optimal recipes to achieve the desired set of properties of the billet. As already mentioned, the effect 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 the technologists is to develop winning combinations of elements that will make the metal part or structure the most acceptable in its quality in terms of use for specific purposes.