1 the principle of heat welding of the device - the process of welding the necessary conditions, there are known to breakdown of the welding heat: electromagnetic energy, chemical energy, mechanical energy, the crystal can be like; flexion while welding is welded to the chemical energy of formula France.
Welding (Gas-Welding) - is a combustible gas and the combustion supporting gas led out from the container, the welding torch (Torch) After mixing, the flame ignited by a high temperature solder Juhuo mouth, and a heating element butt welding methods used are flammable gas acetylene (Acetylene, C2H2, calcium carbide gas), propane (Propane, C3H8, gas), methane (Methane, CH4), hydrogen (Hydrogen, H2), etc., but currently the most commonly used acetylene; combustion gas was oxygen (Oxygen, O2).
1-1 gas supply equipment: Currently oxygen and acetylene or other compressed gases are stored in steel containers, and high-pressure oxygen is usually filled with compressed gas in the form of seamless cylinders, the bottle pressure of about 150kg at 21 ℃ / cm2, mostly painted black or green bottle, and indicate the internal volume, weight, test pressure and the date of manufacture; bottle and begin cylinders made of copper alloy. Acetylene is (calcium carbide, AD 1862 German chemist MR.Wohler made from acetylene gas from calcium carbide calcium carbide;
AD 1892 Willson Aluminium Co., the official production of calcium carbide; Year 1900 French MR.Edmund Fouche welding torch invention, the use of calcium carbide produced by combustion of acetylene gas mixed with oxygen for welding of metallic materials), play a role in water or air The combustible gas produced; acetylene gas early to get the calcium carbide is placed in a hanging basket, and then suspended in the top of the gas cylinder, and then the entire gas cylinder into the tank, then the calcium carbide in the air reservoir the chemical reaction with water and produce acetylene gas, and then sent through a catheter (CaC2 + 2H2O → C2H2 + Ca (OH2)); such a device in the 1960s, the industrial sector in general very wide use, but often because of the risk of an explosion and, nowadays has been replaced by acetylene cylinders. Mounted within the cylinder and is part of acetylene dissolved acetylene, acetylene can be dissolved by water or other liquid, the liquid is different, the amount of dissolution is also different. As common ownership can be dissolved at 1 atm in water is about twice acetylene in acetone (Acetone, C2H6O) can be dissolved in about 25 times; charcoal powder is usually added, such as asbestos within the porous material to absorb sufficient to dissolve the acetylene cylinder acetylene acetone. Typically the acetylene cylinder filling pressure of about 15kg / cm2, exterior paint with brown, shoulder cylinders equipped with safety plugs. Another acetylene and copper due to prolonged exposure, will produce the same explosive element conductive body in the copper surface, so if observe and then, you will find in the acetylene cylinder valve materials are fashioned by the mouth of steel materials, rather than as oxygen copper cylinder valve.
1-2 torch (Torch) -. Whose main function is to oxygen, acetylene inducted into the inner mixed, and adjust the proper gas flow to the pilot flame welding Juhuo mouth to facilitate welding apparatus. General torch can be divided according to different occasions large, medium and small three, including the mixing chamber can be divided into fire-suction (Injector Type) and medium pressure type (Positive Pressure Type); radio suction mixing chamber in which there is a fine waist Venturi tube (Venturi Tube) by which high-pressure oxygen and acetylene gas to attract the mixing chamber together with the oxygen flow to the crater caused by acetylene holes beside buck. Mixing chamber in which the pressure of oxygen and acetylene gas flow, and other places the same pressure into the mixing chamber, the mixing and then flow to the crater.
1-3 crater (fire mouth, Tip) - crater at the front end of the welding torch, the flame due to prolonged heating, it must be made of a material having good heat conductivity; Usually this material is copper or will have chosen a copper alloy; And there are two kinds of crater patterns, ① overall style, that fused with the mixing chamber of the blowpipe, European-style torch to section majority. ② separate, welding torch and to the front there is a crater with a welding torch thread combination blowpipe, when replacing the crater, then remove it and put another crater can, Japanese and domestic torch used mainly do this type of crater.
1-4 pressure regulator (Regulator) - housed in cylinder oxygen, acetylene gas, the pressure is too high, you can not use for welding, and therefore have to rely on the pressure regulator (commonly known as: pressure reducer) the bottle output Gas cut to the appropriate welding pressure. Pressure regulator means the basic structure is composed of a bottle pressure indicator tables, work pressure instruction sheet, pressure adjustment knob cylinder fittings, hose fittings, etc. combination. Zoe adjustment device internal structure can be divided into single-stage (Single-Stage) and bipolar (Two-Stage) two kinds; single-stage, the cylinders can be obtained after one buck welding pressure, but in Welding pressure gradually reduced consumption due to the bottle, so a single-stage regulator must also be adjusted to the appropriate welding pressure. Also in the bipolar, the first paragraph is to bottle feed Qigong with pressure down to about 30kg / cm2 of pressure, and then by the second paragraph down to the appropriate welding pressure.
1-5 rubber tube (Gas-Hose) -. Mainly is connected to the torch gas conduit, must have high voltage characteristics of the rubber tube diameter varies according to size using a welding torch. For ease of identification, oxygen tubes in green or black, and its joint nut for the right thread; acetylene trachea is red, and the joint was left threaded nut, peripherals and light rail vehicles sold a trench.
1-6 tempering prevention device (Check-Valve) -. During welding welding, due to poor operation, resulting crater blockage or other circumstances, this can easily result in reverse back to the phenomena, such as to prevent the violations occurred, mostly single a check valve connected to the intake port at the rear end of the welding torch and the gas form a unidirectional flow of tempering so as to avoid unexpected.
1-7 crater through needle (Tip-Cleaner) -. Thickness for a group of small-diameter steel wire of varying combinations of sets, this is used to clear the crater adhering slag or other carbides, should perform cleanup crater in the crater up placed in a fixed position while unscrew the oxygen valve, and slightly less than the crater aperture vertical pass through the needle into the hole cleared.
1-8 Other accessories (Accessories) -. Goggles, lighters, gas cylinders handle, torch / crater fixed wrench, leather gloves, steel brush, table, tongs, fixtures and so on. 2 adjust the flame: oxyacetylene welding flame welding supply mainly when needed energy, although hydrogen, propane or other gas welding also available for use, but because the temperature of the heat of combustion gas mixed with oxygen after the highest about 2700 ℃, so now the industry is still using acetylene gas. (As for the use of environmental policy under the constraint, then agreed on demand.)
After mixing oxygen acetylene flame combustion gas is vigorous during the culmination of an oxidation reaction, the complete combustion of the chemical reaction equation is as follows: C2H2 + 2.5O2 → 2CO2 + H2O + heat generated by the chemical reaction equation above that: a volume of acetylene gas, the need to obtain 2.5 volumes of oxygen, the ratio of 1: 2.5, while the welding torch is provided a mixing ratio of the flow rate of acetylene gas and oxygen is 1: 1 to 1: 1.2, and the remaining approximately 1.5 volume of oxygen, is supplied by the air; Accordingly, the gas sprayed out of the crater early initial combustion starts the chemical reaction is:
2-1 according to the oxyacetylene flame combustion chemical reaction can be divided into two stages: A. The first stage combustion flame - via the oxygen and acetylene torch gas mixture, the burner flame is ignited at the combustion, including carbon monoxide, and residual hydrogen gas acetylene, showing blue color of the flame, the flame in this area that The reducing flame, the highest temperature, the chemical reaction is as follows: C2H2 + O2 → 2CO + H2 + heat B. The second stage combustion flame - carbon monoxide (CO) generated by combustion of the first stage and a hydrogen gas (H2) is still combustible gas flame to the periphery of the two gases and the oxygen in the atmosphere to form a second phase of complete combustion, the flame color was pink, so we know when oxyacetylene welding carried out in a well-ventilated places, avoid atmospheric oxygen due to the narrow working environment and lack; carbon dioxide and water vapor produced by the secondary combustion, the chemical reaction type as follows: 4CO + 2H2 + 3O2 → 4O2 + 2H2O + heat
2-2 A welding operator in oxyacetylene welding applied, often face recall six basic flame characteristics, hereby commentary as follows: A. Pure acetylene flame - oxygen torch, these two acetylene gas, the acetylene gas flow only out of the crater and the oxygen off, and then the use of pure oxygen to the combustion air and acetylene gas, which produces a flame at the burner close to a yellow When the outer flame zone changed to orange, while also emitting smoke, such a flame temperature of about 800 ℃, is not suitable for welding. B. Carbonizing flame - when pure acetylene flame produced, immediately open the oxygen valve on the torch, so gradually adding pure oxygen acetylene, the flame will be immediately turned from pale blue and orange Waiyan inner flame is turned bright white; Such a flame temperature of about 2800 ℃, the temperature is not very high, usually used for soldering, brazing or welding aluminum, and the surface hardening heat treatment of steel products. C. Reducing flame - carbon flame is formed, which is slightly more than the amount of oxygen in the acetylene amount, if more gradual adjustment of the oxygen flow rate increases, the proportion of the amount of oxygen and acetylene is close to 1: 1, still light blue outer flame, where bright white inner flame will gradually shorten, this flame temperature of about 3050 ℃, typically used for welding nickel-chromium steel, nickel-chromium-molybdenum steel or stainless steel.
D. Neutral flame - by reducing flame to further increase the amount of oxygen and acetylene ratio of about 1.14: 1, the forensic method, by reducing flame sailed to increase the amount of oxygen until the white inner flame shortened to keep the nucleus of the nucleus after the status quo rather than continue to add oxygen to shorten the moment, that is a neutral flame, this property is the nucleus was bright and white, the flame has a clear inner and outer layers, such a flame temperature of about 3200 ℃, for use in welding most widely, usually welded carbon steel that uses this flame, because the metal bath very clearly visible, no Mars splash, and there is a good flow of molten iron.
E. Oxidizing flame - acetylene flame into the case is less than the oxygen neutral flame, the flame of the core is no longer shorter, as the oxygen flow rate increases further, the flame will show a sharp conical core, with the outer flame is shortened, the mixing ratio will be 1: 1.5 about ~ 1.7, the flame color from blue to light blue, the reason for increased oxygen flow, oxidative flame will be issued at this time hissing sound, the flame temperature as high as about 3500 ℃, typically used for steel butt weld penetration first Road bead is not suitable for flat packing welding, due to high temperature metal bath bubbling boil and produce a lot of sparks. The flame used in welding thick steel and steel plate cutting, rarely used on other occasions.
F. Separation flame - flame when ignited, because acetylene gas flow turned too large, which produce a flame jet flame core side away from the crater, and the flame will be shrill hissing sound, this is not the welding flame should immediately reduce acetylene gas flow, while Cadogan oxygen flow until the flame core and the crater termination together, and adapt to the combination of flame. Category 3 commonly used welding electrode and flux of and applicability: Welding (Welding-Rods), commonly known as molten gold, according to the actual needs of the welding process to fill plus metal weldments on. Generally used in welding, begin with the parent main ingredients are similar, and the common specifications are as follows:
A. Mild steel gas welding - uses a wide, general, and low-carbon steel, machine parts, automotive sheet metal iron, sheet industry, etc., are applicable.
B. Copper and copper alloys - copper, copper alloy brazing, welding cast iron, cars and trucks knife blade engagement and so on.
C. Stainless steel gas welding - all kinds of stainless steel and carbon steel butt welding or restricted to.
D. Aluminum and aluminum alloy gas welding - suitable for aluminum and aluminum alloy castings and aluminum welding.
E. Cast iron gas welding - only for welding cast iron and foundry casting porosity fill welding.
F. Silver and copper gas welding - for bronze, brass, copper and dissimilar metals.
3-1. Electrode is generally used, although considering its composition is similar to the base material, the welding rod after then, due to the high temperature melting, some of its rare chemical element diluted or low melting point and reduces the original material properties and microstructure changes , thereby reducing the strength; therefore, require a higher weld strength or need to retain the original high corrosion resistance weldments, its choice of welding strength and alloy composition should be slightly higher than the weldment.
3-2. Electrode contains a small amount of ingredients such as molybdenum, manganese, nickel, chromium, vanadium, titanium, ......, etc., may be increased weld strength, such as electrodes containing phosphorus, sulfur elements, will result in the weld cracking.
3-3. Flux shape can be divided in liquid, powder, paste, solid four. Flux is the workpiece surface to remove dirt grant, the oxide film in order to prevent oxidation of the metal at the welding temperature, so the solder can directly affect the weld quality and strength of the bonding, in particular aluminum, magnesium, copper metal welding is more significant.
4 welding operation essentials: welding work, if not according to the standard procedure, the danger is still very high, so please operate according to the following order before welding, determine implementation of strict requirements. 1) First of oxygen, acetylene gas cylinders in accordance with the provisions of place on location, and lock to prevent dumping. After two) to the cylinder wrench slightly moment and immediately turned the cylinder valve is closed, its role is in the mouth of the bottle valve blow off the dust, and with a clean cloth to wipe clean the valve port.
※ Note: Before Pingfa mouth people can not stand to avoid dust blown human eye or wounding.
3) The regulator were mounted on oxygen, acetylene cylinders, and wrench tighten the nut intake.
4) Take the green (black) rubber tube connected to the outlet end of the low-pressure oxygen regulator, the red rubber tube is connected to a low pressure acetylene regulator outlet end, and tighten the nut.
5) After the first regulator to relax the grip on the regulator, before slowly open the cylinder valve, pressure reducer at the moment on the high-pressure gauge will show the value of the stock at the time of the bottle pressure. ※ Note: acetylene cylinder valve may only reverse a turn, oxygen cylinders can be fully open.
6) gas torch - The pressure reducer regulator tight grip on the gas outlet from the secondary side of the dust discharge, and immediately loosen.
7) will be on the torch car sales have grooved nut and stigma have "GAS" connector mounted on the word red acetylene rubber tube, another mark there "OXY" connector is mounted on the word green (black) oxygen rubber tube .
8) Adjust the oxygen, acetylene gas welding appropriately low side pressure.
9) to brush smear stained with soap bubble solution to all threaded joints on the whole cylinder valve and pressure reducer, and the torch gas inlet fitting thread; if blistering, that means there leak, please re-tighten.
10) to open the torch oxygen, acetylene gas flow control valve, the discharge of impure gas and the impurities remain in the rubber tube, immediately after tightening.
11) mounted on the burner torch.
12) will be placed in the base metal weldments appropriate workbench table.
13) prepare goggles, steel brush, tongs, lighters, gas welding, leather gloves.
14) Wear leather gloves, goggles.
15) to open the acetylene torch valve about a quarter turn, and then use lighters to ignite the flame, open the oxygen valve acetylene flame immediately after ignition, tune out the applicable flame.
※※※ Shi solder position at least away from the fire of oxygen, acetylene gas cylinders at least about 3 meters or more. 5. welding end, knock off the flow when:
1) Close the torch acetylene gas regulating valve.
2) Close the oxygen valve on the torch.
3) Close the oxygen, acetylene gas cylinders cylinders.
4) in the open air on the acetylene torch valve and release the gas regulator and the rubber tube until the pressure gauge pointer return "0" so far, then unscrew the regulator pressure regulator knob and simultaneously shut tight torch acetylene gas regulator valve.
5) then turn on the torch oxygen valve, release the pressure reducer and the rubber tube gas until the pressure gauge pointer return "0" so far, then unscrew the regulator pressure regulator and also shut tight grip on the torch oxygen valve.
6 welding pose called law:
1) flat welding (Flat Position) - symbol "F".
2) transverse weld (Horizontal Position) - the symbol "H".
3) vertical welding (Vertical Position) - the symbol "V".
4) overhead welding (Overhead Position) - the symbol "O".
7 copper and copper alloy welding method:
1) copper (copper) welding - welding copper, mining oxidizing flame, and the flame from the welding surface of the core about 5-8m / m, borax and boric acid flux components for each 50%, should continue to join in the welding Flux.
2) Brass welding - brass belong copper, zinc alloy, zinc melting point due to only about 420 ℃, while the boiling point of 925 ℃, zinc is likely to be volatile in case of heat welding, making the weld porosity. To overcome these shortcomings, brass welding, the speed to be as fast as possible, and to avoid duplication welding. Before welding, you must first preheated to above 600 ℃, then oxidizing flame welding. Because zinc melting toxic fumes generated by evaporation after welding brass, it will feel sweet throat, headache, nausea, please wear protective masks during welding, and the working environment and strive ventilated, welding is used RBCuZn-A level , flux selection of borax, boric acid and then each 45% plus 10% sodium chloride.
3) bronze welding - bronze copper, tin alloy, can be divided into 1-12% tin and tin bronze forging cast 9-25% bronze, brass, bronze, since the difference in thermal conductivity than that, so the ratio of the welding flame Brass small, usually in a neutral or slightly oxidizing flame flame welding. Bronze poor weldability, the elements contained in the tin easily oxidized by high fever, and tin oxide will subsidence in the bath, and therefore will reduce the weld strength. Welding using RCuSn-A level, flux places borax, boric acid and sodium chloride each 40%, 10% potassium chloride each composed.
4) Silicon bronze welding method - this is copper, silicon alloys, easier welding, its thermal degree, without first warming up, then to the micro-oxidation flame welding. Welding using RCuSi-A level, the flux places 75-80% borosilicate and sodium fluoride was added 10% sodium chloride and trace.
5) Copper-nickel alloy welding method - adding 2-43% copper nickel for copper-nickel alloy, commonly used in the manufacture of heat exchangers for cooling, as well as shell casings, easily inhaled hydrogen welding cause pores, usually micro-reduction flame welding, welding using RCuNi, adding borax flux places 50% 50% boric acid, and slightly a little phosphorus, manganese deoxidizer to do.
8 tempering and pour fuel (Backfire) of the causes and improvement measures:
1) Tempering (Back-Fire) - welding torch to put guns in often, occasionally flame goes out, the reason:
① 未依 appropriate thickness crater the size of the assembly, leading to gas burning faster than its cooling rate. In this case, increasing the gas pressure, replace the correct crater.
② crater overheating, use too long. Please stop welding, to the crater to cool before welding.
③ crater in touch welding weldment. Steady torch and keep an appropriate distance from the height of the weldment.
There are carbon or welding slag within ④ crater. Remove the needle to pass.
⑤ crater and the torch is not tightened. Then wrench tighten the crater.
2) pour fuel (Flash-Back) - also known as Backfire burning down, that the flame along the crater by the welding torch, burning rubber tube reverse, when the torch will be severely burned, if not immediately prevent burning down, the rubber catheter spread to gas cylinders, if this time there is no proof Backfire backstop device, and more likely to produce an explosion, especially in radio suction torch burning down most likely cause.
