Nov 13, 0 comments. A weld flaw is any indication on a weld that can compromise the quality of the weld. All welds contain features or discontinuities. It is only when a discontinuity exceeds the relevant acceptance standard that is becoming a defect. A weld discontinuity also known as weld imperfection is any interruption in the normal flow of the structure in a weldment present. This could be in either the weld metal or adjacent parent metal.
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Welding Defects can be defined as the irregularities formed in the given weld metal due to wrong welding process or incorrect welding patterns, etc.
The defect may differ from the desired weld bead shape, size, and intended quality. Welding defects may occur either outside or inside the weld metal.
Some of the defects may be allowed if the defects are under permissible limits but other defects such as cracks are never accepted. Weld Crack 2. Undercut 3. Spatter 4. Porosity 5. Overlap 6. Slag Inclusion 2. Incomplete Fusion 3. Necklace cracking 4. Incompletely filled groove or Incomplete penetration. This is the most unwanted defect of all the other welding defects. Welding cracks can be present at the surface, inside of the weld material or at the heat affected zones. Hot Crack — It is more prominent during crystallization of weld joints where the temperature can rise more than 10,degree Celsius.
Cold Crack — This type of crack occurs at the end of the welding process where the temperature is quite low. Sometimes cold crack is visible several hours after welding or even after few days. Poor ductility of the given base metal. The presence of residual stress can cause a crack on the weld metal. The rigidity of the joint which makes it difficult to expand or contract the metals. If there is high content on sulfur and carbon then also the cracks may appear.
Using hydrogen as a shielding gas while welding ferrous materials. Using appropriate materials may decrease the chances of crack. Preheating the weld and reducing the cooling speed joint helps in reducing crack. Reduce the gap between the weld joints by using reasonable weld joints. While welding releases the clamping force slowly which increases fill to capacity of welding material. When the base of metal melts away from the weld zone, then a groove is formed in the shape of a notch, then this type of defect is known as Undercut.
It reduces the fatigue strength of the joint. If the arc voltage is very high then this defect may occur. If we use the wrong electrode or if the angle of the electrode is wrong, then also the defect may form. Using a large electrode is also not advisable. High electrode speed is also one of the reasons for this defect.
Reduce the arc length or lower the arc voltage. Keep the electrode angle from 30 to 45 degree with the standing leg. The diameter of the electrode should be small. Reduce the travel speed of the electrode. When some metal drops are expelled from the weld and remain stuck to the surface, then this defect is known as Spatter. High Welding current can cause this defect.
The longer the arc the more chances of getting this defect. Incorrect polarity. Improper gas shielded may also cause this defect. Reducing the arc length and welding current 2. Using the right polarity and according to the conditions of the welding. Increasing the plate angle and using proper gas shielding.
It occurs when the electrode is not coated properly. Using a longer arc may also increase its chances. Increased welding currents. Rust or oil on the welding surface. Proper selection of the electrode.
Decreasing the welding current. Using smaller arc and slowing the process to allow the gases to escape. Remove rust or oil from the surface and use a proper technique. When the weld face extends beyond the weld toe, then this defect occurs.
In this condition the weld metal rolls and forms an angle less than 90 degrees. Improper welding technique. By using large electrodes this defect may occur. High welding current. Using a proper technique for welding. Use small electrode.
Less welding current. It occurs when the crater is not filled before the arc is broken, which causes the outer edges to cool faster than the crater. This causes a stress and then crack is formed. Using a proper torch angle may reduce the stress on the metal 2. Using a small electrode may also decrease the crater. Use a proper technique. If there is any slag in the weld, then it affects the toughness and metal weldability of the given material.
This decreases the structural performance of the weld material. Slag is formed on the surface of the weld or between the welding turns. Slag is formed if the welding current density is very small, as it does not provide the required amount of heat for melting the metal surface. If the welding speed is too fast then also slag may occur. If the edge of the weld surface is not cleaned properly then also slag may form.
Improper welding angle and travel rate of welding rod. Increase the current density 2. Adjust the welding speed so that the slag and weld pool do not mix with each other.
Clean the weld edges and remove the slags of previous weld layers 4. Have a proper electrode angle and travel rate. Incomplete fusion occurs when the welder does not accurately weld the material and the metal pre solidifies which leads to a gap which is not filled with the molten metal.
It occurs because of the low heat input. When the weld pool is very large and runs ahead of the arc. When the angle of the joint is too low.
Incorrect electrode and torch angle may also lead to incomplete fusion. Unproper bead position. Increasing the welding current and decreasing the travel speed helps in removing the chances of incomplete fusion. Reducing the deposition rate.
Increasing the joint angle. Try to position the electrode and torch angle properly so that the edges of the plate melt away. Positioning the bead properly so that the sharp edges with other beads can be avoided.
It occurs in the use of electron beam welding where the weld does not penetrate properly. It occurs in materials such as nickel base alloys, stainless steel, carbon steels and Tin alloys. Using high speed of electron beam welding. Using a proper welding technique reduce the chances of necklace cracking. Using proper materials for welding.
Using a constant speed during the welding process. These defects occur only in the butt welds where the groove of the metal is not filled completely. It is also called as incomplete penetration defect. Less deposition of the weld metal 2. Use of improper size of the electrode 3. More deposition of the weld metal.
Welding Defects : Causes, Types And Remedies [PDF ]
Defects are common in any type of manufacturing, welding including. In the process, there can be deviations in the shape and size of the metal structure. It can be caused by the use of the incorrect welding process or wrong welding technique. It can appear on the surface, in the weld metal or the area affected by the intense heat. Porosity occurs as a result of weld metal contamination. The trapped gases create a bubble-filled weld that becomes weak and can with time collapse. This welding imperfection is the groove formation at the weld toe, reducing the cross-sectional thickness of the base metal.
The Most Common Welding Defects: Causes and Remedies
As we already know welding is a vast topic, there are countless books are written on welding, so imagine how important the topic is! Below is the article, where I mentioned the types of welding defects with their causes and remedies. I have written the topic in very easily understand language as well as I attach a PDF file of this article so that after reading you can download the PD F for your offline studies. Welding defects are generated in a welding job due to the faulty or poor technique used by the inexperienced or unskilled welder or due to fundamental difficulties in the welding operation. An ideal weld or good weld should be such that adequate fusion exists between the filler metal and edge preparation together with good penetration.
7 Most Common Welding Defects, Causes, and Remedies
No manufacturing process is immune to defects. Same goes true with Welding. Welding defects are the irregularities that are formed due to the wrong welding process or due to inexperienced welders. Even if irregularities are very minimal but if the shape, size and quality of the weld are way different than what is expected, it is also called welding defects.
7 Most Common Welding Defects, Causes and Remedies
Weld flaws may come in different sizes, shapes, and degrees of severity. There are different types of welding defects that can transpire during the welding process. From porosity and cracking, to burn through and undercut, each has several causes. Luckily enough, there are various remedies that can help welders minimize these welding defects. In this article, we shall be discussing the seven most common welding defects, causes, and remedies plus 2 others. These defects differ from the desired weld bead size, shape, and quality. Welding defects could occur either from the outside or inside the weld metal.