Causes And Treatment Methods Of Blistering And Pores In The Weld Overlay Of Stainless Steel Pipe Flanges

Stainless Steel Weld Fitting When surfacing small parts, in order to avoid overheating of thin-walled substrates and melting of edges, the parts can be placed on copper heat-conducting pads for surfacing. For some materials, such as titanium alloy steel, when direct surfacing is difficult, a titanium-free base transition layer can be pre-surfaced. After mechanical processing, the thickness of the transition layer should not be less than , and then cobalt-based cemented carbide can be surfacing on the transition layer. Because cobalt-based cemented carbide has a low melting point and good fluidity, the surface of the parts to be surfacing must be placed in a horizontal position during surfacing; otherwise, the alloy will flow downhill, making the thickness of the surfacing layer uneven. After surfacing, the stainless steel flange is placed in the furnace for slow cooling. Small parts can be air-cooled or insulated in asbestos ash for slow cooling. Surfacing and elimination measures are as follows. Bubbling and pores. The temperature of the same part of the welding surface is too high, the base is not Jinyu should be batched, too much base metal is mixed into the surfacing layer, the flame ratio changes, the flame shakes, the protective atmosphere is poor, and the surface preparation of the base is not perfect. Factors such as these can cause bubbling and pores.

During surfacing, attention should be paid to maintaining "triple acetylene excess flame" and properly controlling the degree of flame heating on the surfacing surface. The excessive content of oxygen, ammonia, hydrogen and other gases in the cobalt-based cemented carbide rod is also the reason for the formation of blistering and pores in the surfacing layer. So maintain the quality of the alloy rod. Before surfacing, it is beneficial to dehydrogenate the alloy rod for insulation. When the base metal contains titanium, blistering is easy to occur in the surfacing layer. Generally, the filter layer is first surfacing and an alloy with good surfacing performance is used as the transition layer material, and then the cobalt-based cemented carbide is surfacing on the transition layer. For blistering and pores of stainless steel flanges, after all surfacing is completed, the "triple acetylene excess flame" can be used to melt the surfacing metal at the blister and scrape it off with a welding rod, and then the scraped part is remelted once with the same flame and welded to complete. Practice has proved that "scraping and re-welding" has no adverse effect on the hardness and corrosion resistance of the surfacing metal. Cracks. If the preheating temperature before welding is low, the insulation during the cladding process is poor, the temperature drops severely, and the temperature drops rapidly after cladding, cracks will easily appear in the cladding layer.