Welding is one of the main connection methods of steel structures, and the quality of welding directly determines the quality of steel structure installation.
In the steel structure welding construction of the weld defects are usually six categories: cracks, holes, solid inclusions, not fused, not welded through, shape defects and other defects other than those mentioned above.
The main causes and treatment methods are summarized below.
There are usually hot cracks and cold cracks. The main reason for thermal cracking is the poor anti-cracking properties of the base material, poor quality of welding materials, improper selection of welding process parameters, welding stress is too large, etc..
The main reason for cold cracking is the unreasonable design of the welded structure, improper arrangement of the weld seam, unreasonable welding process measures, such as preheating before welding, fast cooling after welding, etc..
Treatment is to drill the crack stop hole at both ends of the crack or eradicate the weld metal at the crack and make up the weld.
Usually divided into two kinds of pores and pore shrinkage.
The main reason for the production of porosity is serious damage to the electrode flux skin, welding rod and flux not baked, the base material has oil or rust and oxide, welding current is too small, arc length is too long, welding speed is too fast, etc., the treatment is to shovel the weld metal at the porosity, and then replenish the welding.
The main reason for the arc pit shrinkage is that the welding current is too large and the welding speed is too fast, the arc is too fast, and the filler metal is not repeatedly added to the arc extinguished, etc. The method of treatment is to fill the arc pit.
There are two kinds of defects: slag and tungsten.
The main reason for the slag is the poor quality of welding materials, welding current is too small, welding speed is too fast, slag density is too large, impede the floating of slag, multi-layer welding slag is not clean, etc., the treatment is to remove the slag at the weld metal, and then weld.
The main reason for tungsten trapping is tungsten contact with the molten pool metal, the treatment method is to dig out the defective metal at the tungsten trap, re-welding.
Not fused, not welded through
The main reason is that the welding current is too small, the welding speed is too fast, the bevel angle gap is too small, and the operation technology is not good.
The treatment for unfused is to remove the weld metal at the unfused area and then weld it.
For the treatment of non-welding through is not welded through on one side of the structure of good openness, can be directly welded on the back of the weld.
For the important welding parts that cannot be directly welded, the weld metal should be eradicated and re-welded.
Including biting edge, weld tumor, collapse, root shrinkage, wrong side, angle deviation, weld super high, surface irregularities, etc..
The main reason for biting edge is improper selection of welding process parameters, such as too much current, too long arc, etc.; incorrect operating techniques, such as the wrong angle of the torch, improper transport, etc.; arc bias blowing at the end of the electrode flux; improper placement of welded parts, etc. The treatment is a slight, shallow biting edge available mechanical methods to repair the file, so that the smooth transition; serious, deep biting edge should be welded.
The main reason for the weld tumor is the incorrect selection of welding process parameters, poor operating techniques, improper placement of welded parts. The treatment method is to use shovel, file, grinding and other manual or mechanical methods to remove the excess buildup of metal.
Other defects: mainly arc abrasion, spatter, surface tearing, etc.