Introduction of various welding materials

- Dec 29, 2017 -

Introduction of various welder materials:
(1) ac manual arc welding machine: mainly welding 2.5mm steel plate
(2) argon arc welding machine: welding of alloy steel below 2MM
(3) dc welder: welding pig iron and non-ferrous metal
(4) carbon dioxide protection welder: thin material below 2.5mm
(5) submerged arc welding machine: weld H steel, bridge frame and other large steel.
(6) for welder: it is mainly used for ring material such as chain cable chain
(7) spot welder: to weld the two plates by clicking
(8) high frequency direct welder: for welding pipes, such as water pipes, etc
(9) roller welding machine: welding tank bottom with rolling form
(10) aluminum welder: specially welded aluminum
(11) flash press welder: to weld copper aluminum joint and other materials
(12) laser welder: specially welding the internal wiring of the triode

Welding of aluminum and aluminum alloy
1.Welding characteristics of aluminum and aluminum alloy
(1) aluminum oxide is easy to oxidize in the air and welding, and the alumina (Al2O3) is high and stable and not easy to remove.It prevents the melting and fusion of the mother material, the oxide film is more important than the surface, and it is easy to be born into slag, unmelted and unsoldered.Aluminum surface oxidation film and adsorption of a large amount of water, easy to make the weld hole.Chemical or mechanical methods should be used to clear the surface of the surface before welding.Strengthen protection during welding process to prevent oxidation.When tungsten electrode argon arc welding, choose ac power supply, through "cathodic cleaning" action, remove oxide film.When gas welding is used, the flux is used to remove the oxide film.When in thick plate welding, can increase the welding heat, for example, helium arc heat is big, the use of helium or argon helium gas mixture protection, or the big specification the melting polar gas shielded welding, in dc on case, don't need "cathode cleaning".

(2) the thermal conductivity and specific heat capacity of aluminum and aluminum alloy are more than double that of carbon steel and low alloy steel.The thermal conductivity of aluminum is about ten times that of austenitic stainless steel.In the welding process, a lot of heat transmission can be rapidly into the base metal, so when the welding aluminium and aluminium alloy, in addition to the energy consumption in the molten metal molten pool, have more useless heat consumption in other parts of the metal, the useless energy consumption is more significant than steel welding, in order to obtain high quality welded joint, should try to use the energy concentration, large power energy, sometimes also can be used such as preheating process measures.

(3) the linear expansion coefficient of aluminum and aluminum alloy is about twice as high as carbon steel and low alloy steel.When the aluminum solidifies, the volume shrinkage rate is larger, the deformation and stress of welding parts are larger, so it is necessary to take measures to prevent welding deformation.It is easy to produce shrinkage cavity, shrinkage, thermal crack and high internal stress.The production can be used to adjust the composition of the wire and the welding process to prevent the heat crack.In the case of corrosion resistance, aluminum - silicon alloy wire can be used to weld aluminum alloy other than aluminum magnesium alloy.With the increase of silicon content, the crystallization temperature range of the alloy is smaller, the flow rate is increased, the shrinkage rate decreases, and the tendency of thermal crack is reduced.According to the production experience, when the silicon contains 5%~ 6%, it is not hot to crack, so the use of SAlSi bar (the silicon content 4.5%~6%) will have better anti-crack resistance.

(4) aluminum has a strong reflection ability of light and heat, and when it is solid and liquid, there is no obvious color change, and it is difficult to judge when welding operation.High temperature aluminum strength is very low, support molten pool difficulty, easy to weld wear.
(5) aluminum and aluminum alloy can dissolve a lot of hydrogen in the liquid state, and the solid is hardly soluble in hydrogen.In the process of solidification and rapid cooling of welding pool, the hydrogen has no time to overflow, and it is easy to form hydrogen pores.The moisture in the arc column atmosphere, the welding materials and the adsorption of the oxide film on the surface of the mother material are all important sources of hydrogen in the weld.Therefore, the source of hydrogen should be strictly controlled to prevent stomatal formation.

(6) alloy elements are easy to evaporate and burn, and the weld performance is reduced.
(7) when the base metal of the parent material is strengthened by deformation or solid solubility, the welding heat will decrease the strength of the heat-affected zone.
(8) aluminum is the face centered cubic lattice, there is no isomer, no phase change in heating and cooling process, the weld grain is easy to be large, and the grain can not be refined by phase change.

2.Welding method almost every kind of welding method can be used for welding of aluminium and aluminium alloy, aluminium and aluminium alloy adaptability to all kinds of welding methods, various welding methods have their own applications.The welding method of welding and welding electrode is simple and easy to operate.Gas welding can be used for the welding quality of aluminum sheet and casting.Welding electrode arc welding can be used for welding of aluminum alloy castings.Inert gas shielded welding (TIG or MIG) method is the most widely used aluminum and aluminum alloy welding method.The aluminum and aluminium alloy sheet can be used for argon arc welding or tungsten electrode pulse argon arc welding.The aluminum and aluminum alloy plate can be soldered by tungsten electrode helium arc welding, argon helium mixed tungsten gas protection welding, melting electrode gas protection welding, pulse melting electrode gas protection welding.

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