Welding torch is a working tool for gas welders, and allows for autogenous welding flame, heated, and molten metal. The modern torch must meet many stringent requirements: to provide stable welding flame of the desired shape, to have precise control, consistently support the established mode of fire, have sufficient strength not to require frequent repairs, be simple, convenient and safe to use, have the lowest possible weight and m . etc. These requirements can be sufficiently well designed to meet a torch, carefully and precisely manufactured from quality materials.
Basic material for the manufacture of burners is a brass mouthpiece made of red copper, and sometimes to reduce the weight of the burners used lightweight aluminum alloys. Welding Torch can be made for different combustible gases, combusted in a mixture with oxygen or air. In the future, will be considered primarily oxygen-acetylene torch, prevailing in the welding technique. Burners have a different capacity, allowing welding thick steel 0.2-30 mm, but the special types of burners can have more power, and there are special burners and thin metal. On the basis of the most important constructive welding torches can be divided into two main types: the burner injector or low pressure, and bezynzhektornye, or high-pressure burners belonging to one or another type is determined by the presence or absence of the injector for the suction of the fuel gas. need to use the injector is determined by the pressure of fuel gas. If a combustible gas has a high enough pressure, not less than 0.5 atm, he can come to the burner by gravity, and the burner may not have the injector. Bezynzhektornaya burner can be operated only at sufficiently high pressure of fuel gas, so she called a high pressure burner. If the pressure of fuel gas slightly (less than 0.5 atm), it is necessary, moreover, forced feeding or leak of fuel gas, which is a special injector, oxygen is embedded into the burner. Therefore, injection burners are called low-pressure burners. This burner can be operated at a pressure of 0.005 atm of combustible gas. The burner can run low pressure and high pressure fuel gas (more than 0.5 atm), but in this case, apply a high pressure burner. At pressures below 0.5 atm injection burner is irreplaceable, unique fit. Given that the burner pressure (bezynzhektornoy) there is no injector, it is easier to design a low-pressure burner (see Fig. a). Oxygen is supplied to the burner on the rubber hose and a nipple and receiving a control valve passes to the mixer 3, where the oxygen flow is broken into thin streams for better mixing with fuel gas, and then passes into the nozzle mixing 4. Quite similar is the way fuel gas entering the burner through the control valve 2. Of the three mixer blend the fuel with oxygen gas enters the mixing chamber 5, where the cross section due to the increase of gas flow rate decreases, and it ends with a mixture of oxygen and combustible gas, which gives the output of the mixing chamber uniform throughout the volume of combustible mixture. From the mixing chamber 5 ready-mix tip passes through the tube 6 and the channel through a calibrated die 7 comes out, where and burns, forming a welding flame. For the formation of normal welding flame flammable gas mixture to flow from the canal orifice burner with a certain speed as burning a mixture of . By increasing the velocity of the gas mixture in excess of the flame separates from the mouthpiece, more and more away from it with increasing shear rate, and finally goes out. With decreasing velocity of the gas mixture from the flame jumps mouthpiece mouthpiece through a channel inside the burner ignites and the explosion of a combustible mixture within the burner. Thus, the torch can work properly only when a certain constant velocity of the gas mixture from the mouthpiece, which might vary only within narrow limits . This normal velocity of the flow depends on the composition of the gas mixture, the diameter of the output channel and the construction of the mouthpiece. For the acetylene-oxygen mixture, this rate for different sizes of burners is in the range 70-160 m / sec. To create such a rate at the outlet of the mouthpiece and to overcome internal resistance burner is required, as experience shows, the gas pressure at the inlet to the burner of the order of 0.5-0.7 atm. Required pressure is approximately the same for both oxygen and acetylene. Bezynzhektornye burner may be constructed for both acetylene and other flammable gases - hydrogen, methane. They are relatively simple in design, well-supported by the constancy of the gas mixture, provide stable welding flame. Despite these positive qualities, a high-pressure burners in our industry are used less often because they can only work on the acetylene sufficient pressure, and the industry makes wide use of low-pressure acetylene. Industrial applications are often injection burner (see Fig. b). Oxygen under pressure of 3.4 atm enters the burner through the nipple, and a control valve, the injector is in the cone 3 is a narrow channel injection cone and exits at high speed in the expanding mixing chamber 5. Breaking with great speed from a narrow channel injection cone 3, the oxygen creates a significant vacuum in the chamber injector 4 and thus force sucks or injects the fuel gas (usually acetylene), entering through the nipple and the valve chamber 2 in the injector, from which it enters the mixing chamber 5, thence in a combustible gas mixture of oxygen with the proper speed for moving the tip of the tube 6 and leaves the burner via a mouthpiece 7. Under the influence of the injection jet tiruyuschey oxygen pressure in the injector chamber falls below atmospheric pressure. Normally produced by our industry of welding torches in the vacuum chamber of the injector is 1000-3500 mm of water. of Art. for tips of different sizes, and the pressure of oxygen supplied to the burner for proper operation the injector should be about 3-3.5 atm. consumption of oxygen in the fuel injection burner remains almost constant and hardly depends on factors such as heating burner orifice, the resistance change expiration gas from the pipe mouthpiece, etc. On the other hand, the consumption of acetylene is easily changed by the influence of various factors and can vary significantly and quickly, disrupting the normal composition of the gas mixture leaving the burner and supplied to the welding flame. Strong influence on the consumption of acetylene in the torch injector and flow it into the welding flame heating is provided a mouthpiece and the tip of the burner, the increase in resistance to the exit gas from the mouthpiece, the change in pressure gas entering the burner. heating burner tip weakens the effect of injecting oxygen and reduces the vacuum in the chamber of the injector, which reduces the flow of acetylene torch. Since the oxygen supply to the burner at the same time remains almost constant, the content of acetylene in the gas mixture decreases against the rules and increased oxidative effect of the welding flame. To restore the normal composition of the mixture and the nature of the welding flame welder must periodically with increasing heating burner tip, increasing the flow of acetylene the burner by opening the acetylene valve on the torch. Resistance to the expiration of a mixture of the mouthpiece may increase, for example, by clogging the channel orifice spray of metal and, more importantly, due to approximations of the burner to the product, causing decreases the distance from the edge of the mouthpiece to the surface of the product. With increasing resistance to the expiration of the gas mixture increases the pressure in the tube tip and the rise in temperature similar to that of the tip reduces the content of acetylene in the mixture and increases the oxidative action of the flame. With the increase of oxygen pressure at the inlet to the burner increases the oxygen content in the mixture, with a decrease - is reduced. When the pressure at the inlet of acetylene torch enriched mixture of acetylene at low pressure reduces the content of acetylene in the mixture. Thus, the injection burner does not provide a constant gas mixture composition, since the composition changes during welding, the welder must continually monitor and adjust the nature of the flame the mixture acetylene torch valve. Variability of the mixture is a significant lack of injection burners. Its main advantage is that you can run on any low-pressure acetylene, ranging from 50 mm of water. of Art. This advantage is crucial, and now our industry has enjoyed almost exclusively injector burners, as the production of acetylene, medium pressure, sufficient to supply bezynzhektornyh burners are still low. However, the injection burner can work on acetylene not only low but also high blood pressure. The higher pressure of acetylene, the better the injection burner. Changes in the composition of the gas mixture under the influence of the burner and heat resistance increases the expiration of a mixture of the mouthpiece is especially noticeable at low pressure acetylene. With increasing pressure, changing the composition of the mixture decreases, and at work on acetylene medium pressure injection burner works almost as stable as bezynzhektornaya. Injection torch welding flame gives a certain size, a change which is possible only in a small range, since a significant increase in the gas flow causes the separation of the flame from the mouthpiece and its extinction, reducing the gas flow is jumping through the flames into the burner and the reverse shock. In this connection it is necessary to stop the burner operation, fully close the acetylene valve on the burner, and then reopen it, to re-ignite and adjust the welding flame. To change the size of the welding flame, such as the transition metal for welding different thickness, it is necessary to apply the torch of a different size. To reduce and simplify the tools normally used by welders universal burners with multiple interchangeable tips. This burner consists of a constant part of the trunk and replacement parts - the tip, which are connected nut. The trunk consists of a handle, adjusting valves, connecting tubes and nipples for gas; tip - from the injector, mixing chamber, the tube tip and mouthpiece. Each number denotes the size of the tip.
See also:
Gas Welding Technology
Gas Welding Article
Welding Torches
Universal welding torch GS
Technical Oxygen
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