Wy25 excavator bucket teeth bucket and weld repair
1. Bucket materials and welding WY25 type Excavator The fighting material as Q345, the weld is good. Bucket Teeth Material ZGMn13 (high manganese steel), the high temperature was austenite single phase, good toughness, impact loads planet surface layer due to work hardening and wear resistance. But this is poor welding of steel: First, heat affected zone material embrittlement caused by precipitation of carbides; second weld hot cracking, especially in the creation of liquefied cracks nearby the weld zone.
(1) heat affected zone of embrittlement caused by precipitation of carbides
ZGMn13 high manganese steel in the temperature again, more than 250 may precipitate along the grain boundary carbides, and the material toughness declined significantly, serious damage to the excellent performance of high manganese steel. After analysis, when the high manganese steel, hvac speed again once the first grain boundary carbide precipitation, while using the residence time, grain boundary carbide particles by the discrete state into a mesh distribution, the brittleness increased significantly. Therefore, when the high manganese steel in Welding, or when heated after welding, heat affected zone will be from a section of carbide precipitation in different degrees, and may the martensite transformation, not only insulating material brittle, and will reduce the wear resistance and vitality. And, in the heat affected zone of carbide precipitation temperature range easily (650 so) the longer the stay, the carbide precipitation.
To reduce carbide precipitation, to prevent loss of toughness and brittle materials, should take measures to speed inside cooling rate, that is, reduced residence time at high temperatures. Therefore, when welding with a much smaller section of welding, intermittent welding, welding, etc. flood destruction.
(2) welding hot cracking Way avoid hot cracks would be reduce the basic metal or Welding materials In the S and P content; also presented by the welding process on measures decrease residual stresses, for example , use of a section of welding, intermittent welding, welding and after welding, hammering dispersed subsequently. Body in the bucket when the high manganese steel surfacing can be one welding layer Cr-Ni, Cr-Ni-Mn or Cr-Mn austenitic steel weld for isolation to prevent cracks.
2. Bucket teeth bucket and welding technology
(1) welding preparation First body pulled from the Big Dipper's bucket teeth to be able to worn, and then Angle grinder Department to install Tooth grinding clean, not too there Nigou, rust, and carefully research for cracks and other defects; in the bucket teeth to get carbon arc air welding Department Paokai a groove, you can angle grinder totally up.
(2) the weld first body in the bucket (bucket teeth and joints) with GBE309-15 electrode for welding, welding electrode is subject to 350 , 10? 5h drying, welding current should be relatively large, slightly slower welding speed to guarantee the fusion zone of nickel content of 5% to 6%, to prevent the generation of the crack-sensitive martensite.
positioning welding. Tooth assembly is in place, with a diameter 3? 2mm of D266 electrodes were bilaterally symmetrical position welding, weld length of not more than 30mm. Water when welding and working.
bottoming welding. Using a diameter 3? 2mm of D266 were bottoming welding stick. With a small current, direct current reverse polarity, intermittent welding, a short section of solder. Welding in order to be stopped every time, water cooling, temperature control between the layers below 50 .
to fill welding. After the end of welding, make use of the D266 4mm diameter electrode for intermittent welding, welding current of 160A, a sub-electrode welding completed 3 to 4 times, each time stopping welding, the weld cooling water still in time 50 below, in addition to hammer, to remove stress and stay away from carbide precipitation; each weld is completed for about two rotation welding seam welded to ensure the symmetry of considerably as 16mm up prior to the welding foot. Welded together with each completed Magnifier Look at the crack situation, where crack is used to eliminate carbon arc gouging after welding.
Bucket teeth repaired by this method will be used by over the year, still a good weld. Modifications fixes Tooth efficient, low cost, good effect, this is practical realize.
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