Ad
related to: what causes undercut in welding
Search results
Results from the WOW.Com Content Network
Undercut created during welding. In welding, undercutting is when the weld reduces the cross-sectional thickness of the base metal. This type of defect reduces the strength of the weld and workpieces. One reason for this defect is excessive current, causing the edges of the joint to melt and drain into the weld; this leaves a drain-like ...
Undercutting is when the weld reduces the base metal's cross-sectional thickness and reduces the strength of the weld and workpieces. One reason for this type of defect is excessive current, which causes the edges of the joint to melt and drain into the weld, thus leaving a drain-like impression along the length of the weld.
During the welding process, residual stresses can present themselves in the area of the weld, either in the heat affected zone or fusion zone. The mean stress a welded joint may see in application, can be altered due to the welding processes implementing residual stresses, changing the fatigue life and can render S-N laboratory testing results. [2]
Arc blow tends to occur if the material being welded has residual magnetism at a certain level, particularly when the weld root is being made, and the welding current is direct current (DC positive or negative). Magnetic arc blow is popularly attributed to a change in the direction of current as it flows into and through the workpiece.
The heat from the welding process and subsequent re-cooling causes this change from the weld interface to the termination of the sensitizing temperature in the base metal. The extent and magnitude of property change depends primarily on the base material, the weld filler metal, and the amount and concentration of heat input by the welding process.
The main obstacle to overcome in this process is the setting of the parameters. For example, if over-welding occurs, then the concentration of plastic in the weld zone may be too low and cause the seal to break. If it is under-welded, the seal is incomplete. [17] Variations in the thicknesses of materials can cause variations in weld quality.
Most weld purging is carried out on joints made by the TIG or GTAW arc welding process. [6] When the laser welding process is chosen, joints or welds being made on reactive materials will need to be carried out and in the case of electron beam welding, this is carried out in a vacuum, in which case purging takes place by complete evacuation of all gas.
Position welding is complicated by a tendency for molten metal to run out of the puddle (“weld drip”), especially a problem with overhead joints. Weld drip will result in cratering and undercutting where the bead should blend into the base metals, resulting in a weak weld and a risk of cracking at the edge of the bead.
Ad
related to: what causes undercut in welding