1, the use of copper and iron electrodes (such as the Z607) welding, metal welding rod of iron and copper immiscible, there is a mechanical mixture of state and mixing was uneven. When the electrode in the w (Fe) increased 30%, so that the plastic weld metal greatly reduced, rigid joints in the welding seam, easy cracks in the weld. Therefore, short-arc welding should be taken to reduce the electrode of the swing, the use of multi-layer welding and other technological measures to prevent weld cracks.
2, in the cold welding of cast iron, in order to repair individual major casting defects, often using pure nickel electrode or nickel-iron, nickel-copper electrode for welding, such as Z308, Z408 and Z508, etc. The Types Of Welding Electrode electrode with nickel-copper cast iron parts, general machining performance is better, but the tensile strength of weld metal is generally relatively low, and because copper-nickel alloy shrinkage large, the weld crack resistance are more difference. Therefore, this electrode only for less demanding strength, but the surface to be machined casting repair welding. Welding electrode with pure nickel weld metal processing has the advantage of good, but expensive, in normal circumstances should not be used. When using these electrodes, in addition to the general technical requirements for welding, the welding speed can not be too fast still need to pay attention, be intermittent welding. Each weld length should not exceed 40-50mm, and percussion with a hammer after welding layer to eliminate stress. Weld is not to be cold to hot again when the second layer of solder, so as to ensure the welding work to achieve better results.
3, high-vanadium cast iron Gas Shielded Welding Wire rod is a more economical cast iron cold welding electrodes, such as the Z116 and Z117. This requires the use of short-arc welding electrodes, and welding sub-regressive sequence, each about 10-30mm, should adopt a smaller current, the same after welding, percussion welding, to reduce stress.
In petroleum, chemical, power station equipment, the process piping and petrochemical tube furnace and boiler furnace tubes are mostly low-carbon steel, the most common brands are: 10,20, Q235, 20g. Because these devices harsh process conditions, the quality of the weld and pipe cleanliness requirements are higher, in the field of construction, we often use manual GTAW (TIG) and SMAW rendering (SMAW) filling, cover surface welding of carbon steel welded pipe is more important. China in the early 1980s, began to promote the installation manual pipeline welding TIG rendering technology, at present, in addition to electric power construction system developed special welding wire and GB/T8110-1995 part of the standard recommended in the use of gas welding carbon steel, low alloy steel welding wire can be used as TIG welding, in general, are used with wire and submerged arc welding with CO2 Gas Shielded Welding Wire as TIG welding. Because of the low carbon steel welding consumables primarily by "equal strength" principle use, the current construction standards and related manuals are recommended Mig Welding Wires: H08 (or H08A), H08Mn2Si, TIG-J50, ER49-1.