In order to carry out any work with different materials, It is important to know all the data before processing them, concerning the characteristics of the material, its physical properties.
The following material will be considered below, like steel. Attention will be focused on this ability of materials, as thermal conductivity. This is an indicator, which you must know, if you plan to work with any material.
The concept of "thermal conductivity"
To begin with, it is necessary to understand the very concept of "thermal conductivity". This will help the user to easily maneuver among the dry numbers and operate with them. In order to carry out certain work, it is necessary to approach the case thoroughly and learn all the possible characteristics of that material, which the user will work with later.
Thermal conductivity is the ability of various material bodies to exchange heat (energy transfer) to less heated parts of the body from its hotter parts. This process is possible due to different parts of the body, which move chaotically. Such particles are:
- molecules;
- atoms;
- electrons and so on.
Such heat exchange is possible in all bodies, in which there is a heterogeneous distribution of temperature. The mechanism of heat transfer will directly depend on the physical state of the material.
Also, the term "thermal conductivity" is used to denote the quantitative characteristics of the ability of any physical body to conduct heat. If you compare thermal circuits with electrical circuits, then such a term is analogous to conductivity.
In order to characterize the quantitative ability of the physical body to conduct heat, a special value is used, which is called the coefficient of thermal conductivity. This characteristic is equal to the amount of heat, which passes through the sample material, necessarily homogeneous, unit area and unit length per unit time at a unit temperature difference. In the well-known SI system, this value is measured in W /(m * degrees Celsius).
The very phenomenon of thermal conductivity is based on principles, which are easily explained by molecular kinetic theory. They are, that heated molecules move much faster, than molecules, in their normal state, therefore, with their rapid chaotic motion, they are able to affect other molecules, are in the colder parts of the body and transfer their heat to them.
Thermal conductivity of steel
In order to operate with the acquired knowledge about the thermal conductivity of materials for further work with them, all the existing nuances for an individual physical body should be taken into account.
If we talk about steel, that should be remembered, that this characteristic of this metal is reduced, if it contains impurities of various kinds. You can even give specific examples, which may confirm this well-known fact. Example, if the steel content of carbon is increased, then it negatively affects the thermal conductivity of steel. In alloy steels, this ratio is even lower due to additives.
If you consider pure steel, does not contain any impurities, then its thermal conductivity will be quite high, as with all metals. It is close 70 W /(m * gr. Celsius).
If you look at the performance of carbon and high-alloy steels, then they are significantly lower, which in principle is not surprising. This is due to the presence of impurities in their composition, which reduces the thermal conductivity. By the way, keep that in mind, that the factor of thermal influence can significantly affect the thermal conductivity of high-alloy and carbon steels. The point is, that with increasing temperature, the coefficient of this value of such steels decreases.
Thermal conductivity of several different types of steels
Here are the dry figures for that, so that the user can immediately find the required values of the coefficient of this value for some grades of steel:
- Thermal conductivity of low-carbon steels, which are used in the production of ordinary pipes, is equal to 54, 51, 47 (W /(m * gr. WITH) for 25, 125, 225 degrees Celsius, respectively.
- The average ratio of carbon steels, which can be calculated at room temperature, is in the range of 50 to 90 W /(M * gr. WITH).
- Thermal conductivity for ordinary steel, which does not contain various impurities, which, in turn, cannot affect this factor in any way, equal 64 W /(m * gr. WITH). This coefficient changes insignificantly when the thermal effect changes, but definitely not so much, as in the case of carbon and alloy steels.
Conclusions
For a successful process of processing any material it is very important to know all its physical properties and characteristics. This is necessary for that, to successfully perform all the necessary work and get the desired result. Ignorance of the characteristics can lead to unpleasant consequences.
The thermal conductivity of steel is a very important point, if work with this metal is provided. It is important to remember not only the basic thermal conductivity of ordinary steel, but also the coefficients of this value in its alloys. They have other properties, which can make working with them more difficult.
The master must have knowledge of it, that carbon and alloy steels have a much lower thermal conductivity, as they contain impurities, directly affecting this value.
You should also remember, that the coefficient of this characteristic of steels depends on the thermal effect. This means, that the higher the temperature, especially the coefficient.