Niobium, formerly columbium, is a chemical element with symbol Nb and atomic number 41. It is a soft, ductile metal, which is often found in the pyrochlore mineral, the main commercial source for niobium. Its name comes from Greek mythology, specifically Niobe, who was the daughter of Tantalus, the name reflects the great similarity between the two elements in their physical and chemical properties, making them difficult to distinguish. The English chemist Charles Hatchett reported a new element similar to tantalum in 1801, in 1809, the English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. The German chemist Heinrich Rose determined in 1846 that tantalum ores contain a second element, in 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element, and for a century both names were used interchangeably. Niobium was officially adopted as the name of the element in 1949 and it was not until the early 20th century that niobium was first used commercially.
Brazil is the producer of niobium and ferroniobium, an alloy of niobium. Niobium is used mostly in alloys, the largest part in special steel such as used in gas pipelines. Although these alloys contain a maximum of 0. 1%, the percentage of niobium enhances the strength of the steel. The temperature stability of niobium-containing superalloys is important for its use in jet and rocket engines, Niobium is used in various superconducting materials. These superconducting alloys, containing titanium and tin, are used in the superconducting magnets of MRI scanners. Other applications of niobium include welding, nuclear industries, optics, numismatics, in the last two applications, the low toxicity and iridescence produced by anodization are highly desired properties. Niobium was identified by English chemist Charles Hatchett in 1801, the columbium discovered by Hatchett was probably a mixture of the new element with tantalum. Subsequently, there was confusion over the difference between columbium and the closely related tantalum.
This confusion arose from the observed differences between tantalum and niobium. The claimed new elements pelopium and dianium were in fact identical to niobium or mixtures of niobium and tantalum, articles on ilmenium continued to appear until 1871. De Marignac was the first to prepare the metal in 1864 and this use quickly became obsolete through the replacement of niobium with tungsten, which has a higher melting point. That niobium improves the strength of steel was first discovered in the 1920s, to end this confusion, the name niobium was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949
Cemented carbide is a hard material used extensively in cutting tools for machining, as well as other industrial applications. It consists of particles of carbide cemented into a composite by a binder metal. Cemented carbides commonly use tungsten carbide, titanium carbide, or tantalum carbide as the aggregate, mentions of carbide or tungsten carbide in industrial contexts usually refer to these cemented composites. Most of the time, carbide cutters will leave a surface finish on the part. Carbide tools can withstand higher temperatures at the interface than standard high-speed steel tools. Cemented carbides are metal matrix composites where carbide particles act as the aggregate and its structure is thus conceptually similar to that of a grinding wheel, except that the abrasive particles are much smaller, the material of a carbide cutter looks homogeneous. The process of combining the carbide particles with the binder is referred to as sintering or hot isostatic pressing, during this process the binder eventually will be entering the liquid stage and carbide grains remain in the solid stage.
As a result of this process the binder is embedding/cementing the carbide grains, the naturally ductile metal binder serves to offset the characteristic brittle behavior of the carbide ceramic, thus raising its toughness and durability. By controlling various parameters, including size, cobalt content and carbon content. The first cemented carbide developed was tungsten carbide which uses tungsten carbide particles held together by a metal binder. Since other cemented carbides have been developed, such as carbide, which is better suited for cutting steel, and tantalum carbide. The coefficient of expansion of cemented tungsten carbide is found to vary with the amount of cobalt used as a metal binder. For 5. 9% of cobalt a coefficient of 4.4 µm·m−1·K−1 is found, both values are only valid from 20 °C to 60 °C, but more data is available from Hidnert. Carbide is more expensive per unit than other typical tool materials, to offset these problems, the carbide cutting tip itself is often in the form of a small insert for a larger tipped tool whose shank is made of another material, usually carbon tool steel.
This gives the benefit of using carbide at the interface without the high cost. Most modern face mills use carbide inserts, as well as many tools and endmills. In recent decades, solid-carbide endmills have more commonly used. To increase the life of carbide tools, they are sometimes coated, four such coatings are TiN, TiC, TiN, and TiAlN
Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity.
Under normal conditions, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones and carbon dioxide, but significant quantities occur in organic deposits of coal, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature.
Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
Compare the main article Elektronenstrahl-Materialbearbeitung within the German Wikipedia. Electron beam welding is a welding process in which a beam of high-velocity electrons is applied to two materials to be joined. The workpieces melt and flow together as the energy of the electrons is transformed into heat upon impact. EBW is often performed under vacuum conditions to prevent dissipation of the electron beam, Electron beam welding was developed by the German physicist Karl-Heinz Steigerwald, who was at the time working on various electron beam applications. Steigerwald conceived and developed the first practical electron beam welding machine, american inventor James T. Russell has been credited with designing and building the first electron-beam welder. Electrons are elementary particles possessing a mass m =9.1 · 10−31 kg and they exist either bound to an atomic nucleus, as conduction electrons in the atomic lattice of metals, or as free electrons in vacuum. Free electrons in vacuum can be accelerated, with their paths controlled by electric and magnetic fields, in this way narrow beams of electrons carrying high kinetic energy can be formed, which upon collision with atoms in solids transform their kinetic energy into heat.
Electron beam welding provides excellent welding conditions because it involves, Strong electric fields, the electron beam can carry high power, equal to the product of beam current and accelerating voltage. By increasing the current and the accelerating voltage, the beam power can be increased to practically any desired value. Using magnetic lenses, by which the beam can be shaped into a narrow cone and this allows for a very high surface power density on the surface to be welded. Values of power density in the crossover of the beam can be as high as 104 –106 W/mm2, shallow penetration depths in the order of hundredths of a millimeter. This allows for a high volumetric power density, which can reach values of the order 105 –107 W/mm3. Consequently, the temperature in this volume increases extremely rapidly,108 –1010 K/s, the effectiveness of the electron beam depends on many factors. The most important are the properties of the materials to be welded. Electron beam welding can be so intense that loss of material due to evaporation or boiling during the process must be taken into account when welding, at lower values of surface power density the loss of material by evaporation is negligible for most metals, which is favorable for welding.
At higher power density, the affected by the beam can totally evaporate in a very short time. Cathode - the source of free electrons Conduction electrons move in a lattice of metals with velocities distributed according to Gausss law. They cannot leave the metal unless their kinetic energy is higher than the barrier at the metal surface
Titanium is a chemical element with symbol Ti and atomic number 22. It is a transition metal with a silver color, low density. Titanium is resistant to corrosion in sea water, aqua regia, titanium was discovered in Cornwall, Great Britain, by William Gregor in 1791, and it is named by Martin Heinrich Klaproth for the Titans of Greek mythology. The metal is extracted from its principal mineral ores by the Kroll, the most common compound, titanium dioxide, is a popular photocatalyst and is used in the manufacture of white pigments. Other compounds include titanium tetrachloride, a component of smoke screens and catalysts, and titanium trichloride, the two most useful properties of the metal are corrosion resistance and strength-to-density ratio, the highest of any metallic element. In its unalloyed condition, titanium is as strong as some steels, there are two allotropic forms and five naturally occurring isotopes of this element, 46Ti through 50Ti, with 48Ti being the most abundant. Although they have the number of valence electrons and are in the same group in the periodic table.
As a metal, titanium is recognized for its high strength-to-weight ratio and it is a strong metal with low density that is quite ductile and metallic-white in color. The relatively high melting point makes it useful as a refractory metal and it is paramagnetic and has fairly low electrical and thermal conductivity. Commercial grades of titanium have ultimate tensile strength of about 434 MPa, equal to that of common, low-grade steel alloys, titanium is 60% denser than aluminium, but more than twice as strong as the most commonly used 6061-T6 aluminium alloy. Certain titanium alloys achieve tensile strengths of over 1400 MPa, titanium loses strength when heated above 430 °C. Titanium is not as hard as some grades of heat-treated steel, it is non-magnetic, machining requires precautions, because the material might gall unless sharp tools and proper cooling methods are used. Like steel structures, those made from titanium have a limit that guarantees longevity in some applications. The metal is an allotrope of an hexagonal α form that changes into a body-centered cubic β form at 882 °C.
The specific heat of the α form increases dramatically as it is heated to this transition temperature but falls, similar to zirconium and hafnium, an additional omega phase exists, which is thermodynamically stable at high pressures, but metastable at ambient pressures. This phase is usually hexagonal or trigonal and can be considered to be due to a soft longitudinal acoustic phonon of the β phase causing collapse of planes of atoms, like aluminium and magnesium, titanium metal and its alloys oxidize immediately upon exposure to air. Titanium readily reacts with oxygen at 1,200 °C in air and it is, slow to react with water and air at ambient temperatures because it forms a passive oxide coating that protects the bulk metal from further oxidation. When it first forms, this layer is only 1–2 nm thick but continues to grow slowly
A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. The pressure differential is dangerous, and fatal accidents have occurred in the history of pressure vessel development, pressure vessel design and operation are regulated by engineering authorities backed by legislation. The preferred test is hydrostatic testing because its a much safer method of testing as it much less energy if fracture were to occur. Today vessels in the USA require BPVC stamping but the BPVC is not just a domestic code, there are, other official codes in some countries, Australia, Canada and Europe have their own codes. Regardless of the nearly all recognize the inherent potential hazards of pressure vessels. Pressure vessels can theoretically be almost any shape, but shapes made of sections of spheres, cylinders, a common design is a cylinder with end caps called heads. Head shapes are frequently either hemispherical or dished, more complicated shapes have historically been much harder to analyze for safe operation and are usually far more difficult to construct.
Theoretically, a pressure vessel has approximately twice the strength of a cylindrical pressure vessel with the same wall thickness. However, a shape is difficult to manufacture, and therefore more expensive. Smaller pressure vessels are assembled from a pipe and two covers, many pressure vessels are made of steel. To manufacture a cylindrical or spherical pressure vessel and possibly forged parts would have to be welded together, some mechanical properties of steel, achieved by rolling or forging, could be adversely affected by welding, unless special precautions are taken. In addition to adequate strength, current standards dictate the use of steel with a high impact resistance. In applications where carbon steel would suffer corrosion, special corrosion resistant material should be used, some pressure vessels are made of composite materials, such as filament wound composite using carbon fibre held in place with a polymer. Due to the high tensile strength of carbon fibre these vessels can be very light.
The composite material may be wound around a metal liner, forming a composite overwrapped pressure vessel, other very common materials include polymers such as PET in carbonated beverage containers and copper in plumbing. Pressure vessels may be lined with metals, ceramics, or polymers to prevent leaking. This liner may carry a significant portion of the pressure load, Pressure Vessels may be constructed from concrete or other materials which are weak in tension. Cabling, wrapped around the vessel or within the wall or the vessel itself, a leakproof steel thin membrane lines the internal wall of the vessel
Silicon is a chemical element with symbol Si and atomic number 14. A hard and brittle crystalline solid with a metallic luster. It is a member of group 14 in the table, along with carbon above it and germanium, lead. It is not very reactive, although more reactive than germanium, Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earths crust. It is most widely distributed in dusts, planetoids, over 90% of the Earths crust is composed of silicate minerals, making silicon the second most abundant element in the Earths crust after oxygen. Most silicon is used commercially without being separated, and often with little processing of the natural minerals, such use includes industrial construction with clays, silica sand, and stone. Silicate is used in Portland cement for mortar and stucco, and mixed with sand and gravel to make concrete for walkways, foundations. Silicates are used in whiteware ceramics such as porcelain, and in traditional quartz-based soda-lime glass, Silicon compounds such as silicon carbide are used as abrasives and components of high-strength ceramics.
Elemental silicon has an impact on the modern world economy. Most free silicon is used in the refining, aluminium-casting. Silicon is the basis of the widely used synthetic polymers called silicones, Silicon is an essential element in biology, although only tiny traces are required by animals. However, various sea sponges and microorganisms, such as diatoms and radiolaria, silica is deposited in many plant tissues, such as in the bark and wood of Chrysobalanaceae and the silica cells and silicified trichomes of Cannabis sativa and many grasses. Silicon is a solid at room temperature, with a point of 1,414 °C. Like water, it has a density in a liquid state than in a solid state and it expands when it freezes. With a relatively high conductivity of 149 W·m−1·K−1, silicon conducts heat well. In its crystalline form, pure silicon has a gray color, like germanium, silicon is rather strong, very brittle, and prone to chipping. Silicon, like carbon and germanium, crystallizes in a cubic crystal structure with a lattice spacing of 0.5430710 nm.
The outer electron orbital of silicon, like that of carbon, has four valence electrons, the 1s, 2s, 2p and 3s subshells are completely filled while the 3p subshell contains two electrons out of a possible six
Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the destruction of materials by chemical and/or electrochemical reaction with their environment. Corrosion engineering is the dedicated to controlling and stopping corrosion. In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen or sulfur, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide or salt of the original metal, corrosion can occur in materials other than metals, such as ceramics or polymers, although in this context, the term degradation is more common. Corrosion degrades the useful properties of materials and structures including strength and permeability to liquids, many structural alloys corrode merely from exposure to moisture in air, but the process can be strongly affected by exposure to certain substances.
Corrosion can be concentrated locally to form a pit or crack, because corrosion is a diffusion-controlled process, it occurs on exposed surfaces. As a result, methods to reduce the activity of the surface, such as passivation and chromate conversion. However, some corrosion mechanisms are less visible and less predictable, in a galvanic couple, the more active metal corrodes at an accelerated rate and the more noble metal corrodes at a slower rate. When immersed separately, each metal corrodes at its own rate, what type of metal to use is readily determined by following the galvanic series. For example, zinc is used as a sacrificial anode for steel structures. Galvanic corrosion is of major interest to the industry and anywhere water contacts pipes or metal structures. Factors such as size of anode, types of metal. The surface area ratio of the anode and cathode directly affects the corrosion rates of the materials, galvanic corrosion is often prevented by the use of sacrificial anodes. In any given environment, one metal will be more noble or more active than others.
Two metals in electrical contact share the same electrons, so that the tug-of-war at each surface is analogous to competition for free electrons between the two materials. Using the electrolyte as a host for the flow of ions in the same direction, the resulting mass flow or electric current can be measured to establish a hierarchy of materials in the medium of interest. This hierarchy is called a series and is useful in predicting and understanding corrosion
Manganese is a chemical element with symbol Mn and atomic number 25. It is not found as an element in nature, it is often found in minerals in combination with iron. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels, by the mid-18th century, Swedish chemist Carl Wilhelm Scheele had used pyrolusite to produce chlorine. Scheele and others were aware that pyrolusite contained a new element, johan Gottlieb Gahn was the first to isolate an impure sample of manganese metal in 1774, which he did by reducing the dioxide with carbon. Manganese phosphating is used for rust and corrosion prevention on steel, ionized manganese is used industrially as pigments of various colors, which depend on the oxidation state of the ions. The permanganates of alkali and alkaline earth metals are powerful oxidizers, Manganese dioxide is used as the cathode material in zinc-carbon and alkaline batteries. In biology, manganese ions function as cofactors for a variety of enzymes with many functions.
Manganese enzymes are essential in detoxification of superoxide free radicals in organisms that must deal with elemental oxygen. Manganese functions in the complex of photosynthetic plants. The element is a trace mineral for all known living organisms but is a neurotoxin. In larger amounts, and apparently with far greater effectiveness through inhalation, Manganese is a silvery-gray metal that resembles iron. It is hard and very brittle, difficult to fuse, Manganese metal and its common ions are paramagnetic. Manganese tarnishes slowly in air and oxidizes like iron in water containing dissolved oxygen, naturally occurring manganese is composed of one stable isotope, 55Mn. Eighteen radioisotopes have been isolated and described, the most stable being 53Mn with a half-life of 3.7 million years, 54Mn with a half-life of 312.3 days, and 52Mn with a half-life of 5.591 days. All of the radioactive isotopes have half-lives of less than three hours, and the majority of less than one minute. Manganese has three meta states, Manganese is part of the iron group of elements, which are thought to be synthesized in large stars shortly before the supernova explosion.
53Mn decays to 53Cr with a half-life of 3.7 million years, because of its relatively short half-life, 53Mn is relatively rare, produced by cosmic rays impact on iron. Manganese isotopic contents are combined with chromium isotopic contents and have found application in isotope geology
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread, a screw thread is the essential feature of the screw as a simple machine and as a fastener. The mechanical advantage of a screw depends on its lead. This characteristic is essential to the vast majority of its uses, the tightening of a fasteners screw thread is comparable to driving a wedge into a gap until it sticks fast through friction and slight elastic deformation. Screw threads have several applications, Fasteners such as screws, machine screws, nuts. Connecting threaded pipes and hoses to each other and to caps, gear reduction via worm drives Moving objects linearly by converting rotary motion to linear motion, as in the leadscrew of a jack. Measuring by correlating linear motion to rotary motion, as in a micrometer, both moving objects linearly and simultaneously measuring the movement, combining the two aforementioned functions, as in a leadscrew of a lathe.
In all of these applications, the thread has two main functions, It converts rotary motion into linear motion. It prevents linear motion without the corresponding rotation, every matched pair of threads and internal, can be described as male and female. For example, a screw has male threads, while its matching hole has female threads, the helix of a thread can twist in two possible directions, which is known as handedness. This is known as a thread, because it follows the right hand grip rule. Threads oriented in the direction are known as left-handed. By common convention, right-handedness is the default handedness for screw threads, most threaded parts and fasteners have right-handed threads. Left-handed thread applications include, Where the rotation of a shaft would cause a conventional right-handed nut to loosen rather than to tighten due to fretting induced precession, examples include, The left hand pedal on a bicycle. The left-hand grinding wheel on a bench grinder, the lug nuts on the left side of some automobiles.
The securing nut on some circular saw blades - the large torque at startup should tend to tighten the nut. The spindle on brushcutter and line trimmer heads, so that the torque tends to tighten rather than loosen the connection In combination with right-hand threads in turnbuckles, in such a case, the coupling will have one right-handed and one left-handed thread. In some instances, for example early ballpoint pens, to provide a method of disassembly
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a golden tinge. Nickel belongs to the metals and is hard and ductile. Meteoric nickel is found in combination with iron, a reflection of the origin of elements as major end products of supernova nucleosynthesis. An iron–nickel mixture is thought to compose Earths inner core, use of nickel has been traced as far back as 3500 BCE. Nickel was first isolated and classified as an element in 1751 by Axel Fredrik Cronstedt. The elements name comes from a mischievous sprite of German miner mythology, Nickel, an economically important source of nickel is the iron ore limonite, which often contains 1–2% nickel. Nickels other important ore minerals include garnierite, and pentlandite, major production sites include the Sudbury region in Canada, New Caledonia in the Pacific, and Norilsk in Russia. Nickel is slowly oxidized by air at room temperature and is considered corrosion-resistant, historically, it has been used for plating iron and brass, coating chemistry equipment, and manufacturing certain alloys that retain a high silvery polish, such as German silver.
About 6% of world production is still used for corrosion-resistant pure-nickel plating. Nickel-plated objects sometimes provoke nickel allergy, Nickel has been widely used in coins, though its rising price has led to some replacement with cheaper metals in recent years. Nickel is one of four elements that are ferromagnetic around room temperature, alnico permanent magnets based partly on nickel are of intermediate strength between iron-based permanent magnets and rare-earth magnets. The metal is valuable in modern times chiefly in alloys, about 60% of world production is used in nickel-steels, other common alloys and some new superalloys comprise most of the remainder of world nickel use, with chemical uses for nickel compounds consuming less than 3% of production. As a compound, nickel has a number of chemical manufacturing uses. Nickel is a nutrient for some microorganisms and plants that have enzymes with nickel as an active site. Nickel is a metal with a slight golden tinge that takes a high polish.
It is one of four elements that are magnetic at or near room temperature. Its Curie temperature is 355 °C, meaning that bulk nickel is non-magnetic above this temperature, the unit cell of nickel is a face-centered cube with the lattice parameter of 0.352 nm, giving an atomic radius of 0.124 nm
Induction heating is the process of heating an electrically conducting object by electromagnetic induction, through heat generated in the object by eddy currents. An induction heater consists of an electromagnet, and an electronic oscillator that passes a high-frequency alternating current through the electromagnet, the rapidly alternating magnetic field penetrates the object, generating electric currents inside the conductor called eddy currents. The eddy currents flowing through the resistance of the heat it by Joule heating. In ferromagnetic materials like iron, heat may be generated by magnetic hysteresis losses, the frequency of current used depends on the object size, material type and the penetration depth. An important feature of the heating process is that the heat is generated inside the object itself. Thus objects can be heated very rapidly, in addition there need not be any external contact, which can be important where contamination is an issue. It is used in induction cooktops for heating containers of food, induction heating allows the targeted heating of an applicable item for applications including surface hardening, melting and soldering and heating to fit.
Iron and its alloys respond best to induction heating, due to their ferromagnetic nature, eddy currents can, however, be generated in any conductor, and magnetic hysteresis can occur in any magnetic material. Induction heating has been used to heat liquid conductors and gaseous conductors, induction heating is often used to heat graphite crucibles and is used extensively in the semiconductor industry for the heating of silicon and other semiconductors. Utility frequency induction heating is used for lower cost industrial applications as inverters are not required. An induction furnace uses induction to heat metal to its melting point, once molten, the high-frequency magnetic field can be used to stir the hot metal, which is useful in ensuring that alloying additions are fully mixed into the melt. Most induction furnaces consist of a tube of water-cooled copper rings surrounding a container of refractory material, induction furnaces are used in most modern foundries as a cleaner method of melting metals than a reverberatory furnace or a cupola.
Sizes range from a kilogram of capacity to a hundred tonnes capacity, induction furnaces often emit a high-pitched whine or hum when they are running, depending on their operating frequency. Metals melted include iron and steel, aluminium, because it is a clean and non-contact process it can be used in a vacuum or inert atmosphere. Vacuum furnaces make use of heating for the production of specialty steels. A similar, smaller-scale process is used for induction welding, plastics may be welded by induction, if they are either doped with ferromagnetic ceramics or by metallic particles. Seams of tubes can be welded this way, currents induced in a tube run along the open seam and heat the edges resulting in a temperature high enough for welding. At this point the seam edges are forced together and the seam is welded, the RF current can be conveyed to the tube by brushes, but the result is still the same – the current flows along the open seam, heating it