If there is no weld size specified, the weld should be entire joint penetration. When a groove reveals the depth of groove preparation but not the weld size, the depth of the weld cannot be less than the depth of preparation. This means that additional metal has to be removed after welding or the strength of the joint will be reduced.
When making groove welds, it is important to ensure that the depth of weld penetration is at least as deep as the prepared groove depth. If this condition is not met, then the strength of the joint will be compromised.
As you can see from this example, if there are no dimensions listed on the symbol, then the whole joint must be penetrated by the laser beam. This means that the entire surface of one piece of metal needs to be exposed to heat from the laser beam. The other piece of metal would need to be removed so that only fresh metal is exposed to the heat of the laser beam.
This is usually not desirable because more material will be destroyed in order to make the weld. Also, having unwelded areas on the metal parts being joined reduces the strength of the joint.
Groove welding is used primarily for joining thin sections of metal together. The laser beam passes through one section of metal and into the other section where it melts the metal creating a joint with a smooth finish.
Unless otherwise noted, all single groove welds should be deemed full joint penetration (CJP). When a weld is applied to both sides of a joint, it is referred to as a double groove weld. For example, the welding sign for a double bevel groove weld is shown below.
The CJP weld symbol indicates that the entire depth of the weld puddle will be covered by subsequent layers of metal, providing complete coverage and preventing any stress risers from forming.
This joint design requires full joint penetration on both sides of the joint to achieve the desired structural strength. If half-depth or partial joint penetration was used, then the tube would have been weakened at that point and could have failed prematurely. The CJP weld symbol should always be used when joining tubing together in order to avoid weakening the joint.
Joints between tubular goods require special care because the tubes are usually thin-walled and low in mass. A small defect or lack of fusion at the joint can lead to failure. Stress risers at the joint may not become visible until after further loading, which can lead to premature failure. Therefore, joints between tubular goods should be fully fused to prevent these defects from forming during use.
Good welding practices should be used throughout the process to ensure proper fusion of the materials and formation of a strong joint.
The letter "G" is used to indicate a welded joint. This letter can be used alone as a reference point when positioning and aligning metal for welding. The weld should be made in a direction from the bottom of the letter to the top of the letter.
There are three basic methods used in welding: gas welding, arc welding, and plasma cutting. Each method has its advantages and disadvantages. Which method you use will depend on what you are trying to accomplish and how much experience you have with each type of welding.
Gas welding uses a filler material (steel) that is fed into the joint being welded by a gas burner. The gas produces an intense heat that melts the filler material and joins the two pieces of steel together. Gas welding is most commonly done by professionals because it is difficult to perform well without special training. The quality of the weld depends on how well you set up your equipment and how experienced you are at welding using this method.
Arc welding uses an electric current to melt filler material (steel) that is fed into the joint being welded.
Subtract 1.5 mm from the thickness of the thinner part to be joined to get the maximum size of a fillet weld. When applying welds to the round toe of steel sections, the maximum size of the weld should not exceed 3/4 of the thickness of the section at the toe. The actual size of the weld depends on how it is applied; see below for more information.
Welds can be either continuous or discontinuous. In a continuous weld, both ends of the metal being welded are brought together and fused by the heat of the welding torch. This type of weld is used in most structural applications because it produces a strong joint with very little gap between the parts being welded. A discontinuous weld consists of two or more separate passes of the torch over the same spot. These passes may overlap each other slightly but should not touch. They fuse together any material that comes in contact with the heat from the welding torch.
The maximum size of a fillet weld is determined by the diameter of the fillet itself. Therefore, the maximum size of a weld is equal to the distance from the center of one face of a component to the center of its opposite face. The minimum size of a weld is zero (0).
Fillet welds can be made using either gas tungsten arc welding (GTAW) or laser beam welding (LBW).
When the welding composition is held in place below the joint by a support, somewhat larger root gaps are permitted; if the root gap exceeds 1/16-in. , submerged arc welding flux should be tamped into the gap ahead of the weld. Submerged arc welding with filler metal requires very small root gaps.
The term "root gap" describes the space between the base material and the weldment that contains the heat source for melting the base material. The root gap must be large enough to allow passage of the welding rod or wire, but it should be as small as possible while still providing adequate cooling. Too small a root gap can cause excessive heating within the weld puddle, resulting in brittle cracking or exudation of metal from the weld.
Too large a root gap results in lack of fusion of some molten metal within the weld puddle and may also cause excessive heating which can lead to the same problems mentioned above.
For example, if TIG (Tungsten Inert Gas) welding is used with a support, the root gap can be as large as 1/4-inch. If however, the workpiece being welded has a diameter less than 1/4-inch, a smaller root gap would be required.
Calculate the weld size, s, at each node on the terminated part's intersecting edge: