How To Prevent The Expansion Of Stainless Steel Pipe Flange Cracks During Repair Welding
Stainless Steel Weld Fitting preparation before welding When the casting is cracked, the location and length of the crack should be observed clearly first. When the crack is narrow and cannot be found with the naked eye, it can be displayed with the help of a magnifying glass or by heating with a kerosene hydrostatic test flame, and then stop holes can be drilled at both ends of the crack to prevent the crack from expanding during the repair welding process.
In order to avoid the generation of pores, slag inclusions or poor fusion during the repair welding process, the oil, rust and other objects in the repair welding area can be cleaned by brushing with alkaline water, scrubbing with gasoline, and burning with a gas flame. Under the condition of ensuring the smooth progress of welding, the groove form should minimize the groove angle to reduce stress and workload. The groove form is divided into two categories: non-penetration groove and penetration groove. Since gray cast iron cannot be cut with oxyacetylene flame, the processing method of the groove surface generally adopts mechanical methods such as manual picking with a flat shovel, wind shovel iron, grinding with a grinder, etc. Castings with low requirements for groove surface processing can also be planed with carbon arc air planing. The longitudinal stress of the short-section intermittent welding weld begins to increase with the increase of the weld length. When it reaches a certain level, it will cause transverse cracks. Therefore, only a short weld can be welded each time, and the next weld can only be welded after the weld reaches the bottom. Long welds cannot be welded continuously, otherwise, cracks will inevitably occur. Similarly, the weld should be narrow and should not be swung horizontally to avoid large transverse stress. Forced weld practice has proved that when gray castings are repaired, local overheating near the weld will cause weld peeling. Therefore, in order to prevent local overheating and improve work efficiency, water or cotton yarn dipped in water can be used to quickly weld each weld after welding to draw out the input heat.
At this time, the welder should pay attention that rapid cooling generally does not cause cracks. The use of small current will increase the depth of penetration and the thickness of the white layer in the fusion zone. The thick white layer is not only difficult to process, but may also cause weld peeling and thermal cracks on the weld. Therefore, a smaller current should be used for repair welding. If only a single-layer weld is used for repair welding, the fusion zone at the bottom of the weld is relatively hard. When repair welding, a layer can be scraped off from the upper part of the welded weld, and then another weld is welded. This weld is called an annealed weld. The annealed weld can make the bottom of the first weld softer due to annealing, so the processability of the stainless steel flange joint can be improved. According to production experience, when repair welding, it is a way to reduce or even white layer to minimize the length of the welding section and shorten the time of each section. The specific method is to use a small diameter electrode, do not move the arc, and when the fusion is good, the molten pool wets the parent material and immediately breaks the arc to form a circular weld. The next weld overlaps with this weld, gradually weld a weld, and then weld the annealed weld. After hammering the weld, you can immediately hammer the weld with a small hammer after welding each section of the weld, so that the weld can be extended and widened, offsetting the shrinkage during the time, so that the stress can be.
