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Tham khảo tài liệu 'guidelines for shielded metal arc welding (smaw)_3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Simpo PDFMergevand Split Unregistered Version - http www.simpopdf.com Butt Joint Weld 2 Electrode Position When welding overhead gravity may distort the molten metal. This technique is not suitable for all electrodes. 1 Electrode 2 Backing Strip Welding overhead is the most difficult welding skill to master. When welding overhead use a welding motion that draws arc out and slightly away from the crater to allow weld puddle to solidify. Welding Patterns Overhead Welding Technique When weaving is necessary use the pattern shown. Bevel edges if warranted by material thickness see Section 3-11 . Tack weld a backing strip to the plates to make the first weld pass root pass easier. Draw arc out and away from crater to let weld puddle soldify. Sequence Of Multiple Weld Passes Tee Joint Weld First Weld Pass Subsequent Weld Passes 804 260 155 095 Page 19 Simpo PDF Merge and Split Unregistered Version - http www.simpopdf.com 1 Vise 2 Weld Joint 3 Hammer Strike the weld joint in the direction shown. A good weld bends over but does not break. If the weld breaks examine it to determine the cause. If the weld is porous many holes the arc length was probably too long. If the weld contains bits of slag the arc may have been too long or the electrode was moved incorrectly which allowed molten slag to be trapped in the weld. This may happen on a V-groove joint made in several layers and calls for additional cleaning between layers. If the original beveled surface is visible the material was not fully melted which is often caused by insufficient heat or too fast a travel speed. S-0057-B SECTION 4 - WELDING TROUBLESHOOTING 4-1. Porosity SSSt ỈJ H Porosity - small cavities or holes resulting from gas pockets in weld metal. Possible Causes Corrective Actions Arc length too long. Reduce arc length. Workpiece dirty. Remove all grease oil moisture rust paint coatings slag and dirt from work surface before welding. Damp electrode. Use dry electrode. 155 095 Page 20 Simpo PDFMerge and Split
