Steel Cutting » plasma steel cutting

Plasma cutting gases

admin — Thu, 24 Feb 2011 15:31:16 +0000

Plasma cutting can be lead by a hand controller and an automated one based on electronic and mechanical interfaces on every stage of the technological process. Classic manual welding thanks to small weight of arc and currency invertors can be applied in joining parts of complex design constructions where they are difficult to access in any other way. With plasma technology new possibilities are opening like underwater cutting on high depths, even in salty water of sea by specialized robot units. Such extremal conditions requires replacing of the nozzles and cathodes in the head of cutter more frequently. Cutting steel technology significantly depends of jet qualities and strictly following after producers specifications is must to archeive a desirable outcome. For plasma cutting we use dedicated burners with working current between 30-40A and 100-1200A for high powered cutting.
Plasma burners dedicated for manual cutting are cooled widely by air.It very efficient for cutting with lower parameters of power, when plasma arc currency is below one hundred amperes. High power burners demands more effective water cooling and cnc automation. Improved models of burners are based on selfcalibrating jets and electrodes to preserve strenght and durability as long possible. Matching and adjusting particular bulding blocks of plasma burners we can result in numerous cutting parameters to allow for significant cost reduction without compromise on cutting speed. Plasma gas melts and flushes down liquid steel from a slot while a shelding gas protects the area of cutting from air (and gives an extra colling to it). Application of additional narrowness of plasma arc by shelding gas increases thickness to plasma stream and it’s heat which is is a good way to increase speed of cutting with the same working currency. In this case we ususually use an argon or mixture of it’s mixture with hydrogen or nitrogen. Kind of steel which is cutted down determines kind of a second shelding and narrowing gas then. For lowcarbonised steel we can apply air or oxygene which gives even more speed up for cutting steel by it’s exothermic combustion of steel feature. Because of prices of gases based on argon and hydrogens the industry makes big efforts to apply new and cheaper gas solutions which gives same quality results.

Plasma technology

admin — Mon, 15 Mar 2010 13:43:34 +0000

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.

Plasma cutting steel

admin — Thu, 11 Mar 2010 11:26:36 +0000

Plasma, sometimes called the fourth state of matter, makes tech-people fascinated with it’s numerous properties. Some of them are interesting just from science point of view but many have a practical behoof in the industry. And it’s still growing with a new discoveries and new amazing facilities. Also when it comes to steel machining and cutting – plasma gives a fair competition ever to a laser cutting.

Plasma cutting machines are dedicated for manual and automated handling. Plasma and air jumble is useful with cutting electrical conducting parts made of steel, alloys, aluminium and it’s alloys, coppers, brasses and even a cast iron. Plasma cutting machines shows it’s versatile also when it comes to different enviromental conditions allowing to cut deep underwater for example. Coeval plasma machines are usually instant ready to use and with special accesories can cut in places with limited access for the other tools.

The main advantages for plasma machines:

high speed of cutting
cutting without overheating – quick nailing
small influence in the area of cutting on the steel
narrow slit
allows to cut without overburning thin fabrics.

And here comes some disadventages:

loud work noise
strong radiation
much of exhausts – gases and fumes
Some structure degeneration in cutting area
perpendicular keeping is sometimes difficult.

Let’s see and listen some example: