How do you get rid of lamellar tearing?
A smaller diameter electrode which can be used to produce a smaller leg length, has been used to prevent tearing. A low hydrogen consumable will reduce the risk by reducing the level of weld metal diffusible hydrogen.
What is meant by lamellar tearing?
Lamellar tearing is a cracking phenomenon which occurs beneath welds, and is principally found in rolled steel plate fabrications. The tearing always lies within the parent plate, often outside the transformed (visible) heat-affected zone (HAZ), and is generally parallel to the weld fusion boundary.
How can we explain the lamellar tearing in any highly stressed structure?
Lamellar Tear is caused by Tensile Stress in Through-Thickness direction. This comes from the shrinkage of the weld and the base metal itself has impurities or inclusions that are parallel to the work surface Thus causing a tear or crack Lamellar Tearing up.
What causes slag inclusions?
Slag inclusions are nonmetallic particles trapped in the weld-metal or at the weld interface. Slag inclusions result from faulty welding technique, improper access to the joint, or both. Dipping the tungsten electrode in the molten weld-metal or using too high current that melts the tungsten can cause inclusions.
What are lamellar tears and how do they occur?
Lamellar tearing is a form of cracking that occurs in the base metal of a weldment due to the combination of high localized stress and low ductility of the plate in the through-thickness direction.
What causes laminations in steel?
What are laminations? Laminations are an imperfection in a steel or alloy, resulting from blisters, seams, foreign material, and/or scratches on an ingot or billet that are not repaired during the rolling process.
What causes lamination in steel?
Any discontinuity present in the metal, such as porosity or inclusions trapped in the slab, are elongated in the direction of rolling and results in laminate formation within the metal sheet. Plate lamination in carbon steel happens when folds or layers of plates are rolled together into a single plate thickness.
What mostly the causes that can defect on the finished weldment?
Causes:
- Too high weld current.
- Too fast weld speed.
- The use of an incorrect angle, which will direct more heat to free edges.
- The electrode is too large.
- Incorrect usage of gas shielding.
- Incorrect filler metal.
- Poor weld technique.
What causes slag?
Causes. As slag is the residue of the flux coating in MMA welding, it is principally a deoxidation product from the reaction between the flux, air and surface oxide. The slag becomes trapped in the weld when two adjacent weld beads are deposited with inadequate overlap and a void is formed.
What is the importance of removing slag?
Removal of the slag is necessary for four reasons: Ability to inspect the quality of the weld area, Aesthetics, or ergonomically appearance. If a second layer or pass of welding is to be made on top of the first to clean and clear the unpleasant surface for coatings such as paint or oil.
What is lamination in welding?
A lamination seam is part of a weld seam inspection in which the weld seam is overlayed with the lamination material to produce a smooth finish on the weld seam. A lamination seam can protect the weld portion on a metal joint from corrosion.
What are two cases of lamellar tearing in fabricated steel?
Two cases which have been reported are : 1 Pull out of lifting lugs from the parent plate. 2 Lamellar tearing in flange-to-web joints in fabricated I beams. It is important to be aware that lamellar tearing can be a problem in apparently simple unrestrained joints if the material is sufficiently susceptible.
How does the susceptibility of a lamellar tear depend?
The susceptibility to lamellar tearing depends upon the type of joint and the inherent restraint, on sulphur and oxygen contents, on the type and morphology of inclusions (which affect the through-thickness ductility) and on the hydrogen content of the weld.
What can I do to stop the tearing of the lamellars?
Cerium or rare-earth metal (REM) treatment is another means of control. Hydrogen has a significant effect on lamellar tearing.
What’s the temperature at which a tear occurs?
Tearing may also start at a higher temperature than is possible for hydrogen cracking (perhaps as high as 300 °C).