Welding people must see, this 79 welding common sense to memorize!

Share 79 welding common sense, beginners remember not only save, but also memorize oh! 1. Mechanical properties of metal include strength, plasticity, hard seat, toughness, fatigue strength, etc. 2, hardness indicators can be divided into Brinell hardness, Rockwell hardness, Vickers hardness and other three. 3. The performance of metal materials to conduct heat is called thermal conductivity. 4, the physical properties of metal including density, melting point, thermal expansion, thermal conductivity, electrical conductivity, etc. 5, heat resistant steel refers to the steel with a certain thermal stability and thermal strength at high temperature. 6, stainless steel is with atmospheric resistance, acid, alkali, salt, corrosion effect of rust acid flow. 7. The performance of metal materials to conduct current is called electrical conductivity, and its measurement index is resistivity. The temperature at which a metal changes from solid to liquid is called the melting point. 9. Weld symbols are generally composed of basic symbols and guide lines. If necessary, auxiliary symbols, supplementary symbols and weld size symbols can also be added. 10, indicating that the weld surface is flush symbol is one; The symbol for the bottom of the weld plate ; The symbol for the weld surrounding the weldment is. 11. According to different heating and cooling methods, heat treatment can be divided into annealing, quenching, normalizing and tempering, etc. 12. An electric current whose direction and magnitude do not change with time is a direct current and the reverse is an alternating current. 13, welding welding components along the steel plate rolling layer formed by the ladder crack is called lamellar tear. 14. When other conditions remain unchanged, the tendency of porosity increases with the increase of welding speed; When the welding current increases, the porosity tendency increases. When the arc voltage increases, the porosity tendency increases. Manual arc welding is suitable for welding carbon steel, low alloy steel, heat resistant steel, low temperature steel, stainless steel and other materials. 16, manual arc welding can be flat, vertical, horizontal, vertical and other positions of welding, so it is widely used. 17. Compared with gas welding and submerged arc welding, manual arc welding has fine microstructure and good performance of small joints in the heat affected zone. When manual arc welding, the welder’s operation technology and experience directly affect the quality of the product. 19. Welding process parameters refer to the physical quantities selected to ensure welding quality during welding. 20, manual arc welding is mainly based on the performance of the base metal, the rigidity of the joint and working conditions to choose the electrode, welding general carbon steel and low alloy steel is mainly according to the principle of equal strength to choose the strength level of the electrode. 21. There are many factors to consider when choosing welding current for manual arc welding, but the main one is electrode diameter; Welding position; Pass level 22. The empirical formula for calculating welding current in manual arc welding is I= 10D2. 23. The basic form of manual arc welding groove is I shape; V; Double V; Double Y; Double U bevels with franges 24. Welding cracks are characterized by sharp notches and large aspect ratio. The purpose of preheating is to reduce the cooling rate and improve the stress condition. 26. The slag of alkaline electrode has strong desulfurization and dephosphorization ability. 27. Immediately after welding, all (or part) of the welding parts are heated or kept warm. The process measure of slow cooling is called after heat, which can make the hydrogen in the welding joint effectively escape, so it is an important measure to prevent delayed cracks. 28. When welding, the bubbles in the solution pool fail to escape when solidification, and the remaining holes formed are called pores. After welding, the residual slag in the weld is called slag. 30, the coating layer on the surface of the welding core is called drug skin. Electrode length depends on core diameter, material, coating type, etc. 32, welding core steel can be divided into carbon structural steel; Alloy structural steel; Stainless steel three categories. Electrode can be divided into carbon steel electrode according to different uses; Low alloy steel electrode; Stainless steel electrode; Surfacing electrode; Cast iron electrode; Nickel and nickel alloy electrode; Copper and copper alloy electrode; Aluminum and aluminum alloy electrode; Special purpose electrode; The joint of the two ends of the weldment is relatively parallel to the butt joint. The butt joint without groove opening is used for welding of thinner steel plate, and the butt joint with groove opening is used for the thick surface of steel plate Full penetration welds are required. Acetylene generator is the use of voltage and water interaction to make acetylene equipment. The role of the pressure reducing valve is to store in the cylinder of high pressure gas decompression to the required stable working pressure. 38, oxygen and acetylene mixture ratio β is 1.1-1.2 for neutral flame, β>1.2 for oxidation flame, β<1.1 for carbonization flame. Gas welding process parameters have wire diameter; Flame properties and energy rate; Nozzle tendency; Welding speed; . 40, welding is a processing method by heating, pressurizing or using two, and with or without filling materials, so that the welding parts to achieve atomic bonding. The basic symbol of weld is the symbol of the shape of the weld section, a total of 13. The Angle between the vertical surface of the weldment and the groove surface is called the groove surface Angle. The junction of weld surface and base material is called toe. 44, when welding non-ferrous metals, cast iron and stainless steel and other materials, usually must use gas welding flux. Acetylene bottle safety is arranged on the bottle shoulder fusible plug to achieve. Ignition method of welding arc has contact moment ignition method; High frequency high voltage arc method and other two. The general structure of manual arc welding is acidic electrode, and the important structure is alkaline electrode. 48, welding electrode coating melting slag characteristics, electrode can be divided into acid electrode and alkaline electrode. Oxygen cylinder safety is realized by the metal safety film in the valve. Metal cutting process includes preheating - burning heat - blowing slag three stages. 51. In heat treatment production, isothermal cooling is commonly used; Two kinds of continuous cooling. The necessary conditions for the generation and maintenance of arc are cathode electron emission and gas ionization. 53, the main source of sulfur in the weld is the base metal, wire, coating or flux, so the key measure to reduce the sulfur content of the weld is to strictly control the sulfur content of the welding raw materials. The energy input to the weld per unit length by welding energy is called line energy. A crystallization of molten pool includes the generation of crystal nucleus and crystal nucleus growth two processes. 56, CO2 gas welding, nitrogen porosity is the cause of poor protection or CO2 gas is not pure. CO2 semi-automatic gas welding of the inverse wire push wire type; Drawing type; Push-pull type; Three, the current use of wire push type welding gun. The gas supply device of CO2 gas shielded welding is made of gas cylinder; Dryer; Preheater; Pressure reducer; Flow meter and other components. CO2 gas welding welding equipment includes welding power supply; Welding torch. Wire feeding system; Air supply device; Control system, etc. Post-welding heat treatment mode after heat; High temperature tempering; Normalizing or normalizing and tempering. The cracks produced by welding gray cast iron have thermal stress cracks; Hot crack; Two kinds, especially thermal stress crack is more common. Ductile iron hot welding method, should be cast 238 electrode. The stress and deformation of the weldment in the direction perpendicular to the weld is called transverse stress and deformation. 64. For the structure of asymmetric welds, the side with less welds should be welded first, and the side with more welds should be welded later, which can reduce the overall deformation. In order to offset the welding deformation, welding parts before welding to the opposite direction of the welding deformation of artificial deformation, this method is called the inverse deformation method. 66. Heat dissipation method is not suitable for welding materials with high hardenability. Flame correction is the use of plastic deformation caused by local heating of the flame, so that the longer metal is compressed after cooling, in order to achieve the purpose of correcting deformation. The key to flame heating correction is to master the deformation caused by local heating of the flame, so as to determine the correct heating position, and the temperature and the number of repeated heating should be controlled. 69, flame heating mode has point heating; Linear heating; Triangle heating. Triangular heating is often used to correct the bending deformation of thick and rigid components. Preheating before welding can reduce the temperature difference and slow down the cooling rate, thus reducing the welding stress. 72, acetylene bottles should be used upright, lying acetylene bottles in direct use, must stand for 20 minutes, to use. The pressure reducer shall not be contaminated with grease during use. Welding torch should be checked before use of the absorption performance of the torch. Welding stainless composite steel plate should use three different dacron electrode to weld the same weld. If the torch temper, first of all should quickly turn off acetylene and then off oxygen. 77. According to the national standard GB3323-82 "Steel welding seam shooting photography and film classification", the quality standard of steel welding seam shooting inspection is divided into four levels, among which the defects in grade ⅰ weld are the least and the defects in grade ⅳ weld are the most. GB3323 provides that grade I welds are not allowed to have cracks; Incomplete fusion; Lack of penetration. Strip slag; Crack; Not fused; No two - sided welding or single - sided welding with backing plate is allowed in the weld; . When carbon steel electrode is used to connect cast iron and low carbon steel joint, 4-5mm isolation layer can be surfacing on cast iron groove first, and then assembly spot welding after cooling. 铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods