Plasma technology
Plasma is a set, mixture of ionized and neutral particles. This set contains ionized atoms and electrons which coexist together while the whole area filled by plasma is electrically indifferent. Electrical resistance is different than the one observed in metal materials – it diminishes with the temperature increase. Plasma has a cellular like structure, where every cell is surrounded by the double layer buld by charged particles. Layers are formed by temperature difference in parts of plasma. The warmer side of double layer creates higher density area with positively charged ions. Conversely, the colder side collects more electrons. Between them forms a corrdidor with less frequent appearance of positively and negatively charged particles. Plasma cells can set in a grainy structure but more often they build a fibre like shape, especially when plasma floating streams.
We can distinct the two groups of plasma when comparing a temperature.
- cold plasma, which is created in plasmatrons – temperature range: 4000 to 30,000 K
- hot plasma, found in the stars and nuclear fusions – above 30,000 K
When the electricity is conducted within the plasma cell, which has very high conductivity property, it has to pass the double layer. This is where almost all voltage potential is dropped. When we look closer to the plasma and electrical currency, we differ a three states:
- very low electrical currency – no visible effects
- moderate electrical currency – the visible light appears
- electrical currency exeeds a given treshold – electric arc forms
The third one is the one we are interested especially when it comes to steel cutting. Steel cutting by plasma precisely. The electric arc allows to cut all electrically conductive materials and it is widely used in the industry in the mid of the previous century. Development of technology and electronics esteblished it in the steel machining world and deployed a strong competitor for the other cutting methods, like laser cutting steel for example. We will continue the topic in the next article.
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