What happens when pinholes appear on my weld? It means that the weld's quality is compromised and has potential contaminants like trapped gas, oil, or moisture. It weakens the weld joint's tensile strength.
As I'm sure you have learned, TIG welding a small blob over a pinhole is sure to generate more pinholes. The best approach is to remove all of the material that has any trace of porosity. I sometimes do this with an abrasive cut-off disc, making a tiny slice in the weld, which removes the porous area.
When it comes to porosity, the American Welding Society dictates that the sum of the diameters of visible porosity should not exceed 3/8 inches, or 9.5 mm, in any linear inch of the weld, or exceed 3.4 inches or 19 mm, in any 12-inch length of a weld.
Signs of a bad weld include: Spatter, undercutting, visible lack of fusion, and cracking. However, with all welds tests must be run in order to determine adequate penetration.
A good weld should be visually appealing, with a smooth and uniform weld bead that shows proper fusion and penetration. Bad welds, on the other hand, may contain defects like porosity, pinholes, or slag on the weld surface, which can compromise the strength and reliability of the weld.
Appearance: Welds should have a consistent, smooth, and uniform appearance. Profile: Depending on the application, welds need to be flat, concave, or convex. Coloration: A good weld will have a color-free appearance that indicates no oxidation has occurred.
Porosity does not "burn out", it travels from weld pass to weld pass and never leaves the original weld pass.
One of the most obvious forms is surface porosity, also known as surface breaking pores. This is the porosity that looks like swiss cheese to the naked eye. The pores are sitting right on top of the bead, spread out evenly or deposited randomly throughout the bead.
Porosity, one of the most common MIG welding defects, is the result of gas becoming trapped in the weld metal. Inadequate shielding gas coverage is among the biggest culprits, and this can be addressed in several ways. First, check the regulator or flow meter for adequate gas flow, increasing it as necessary.
Pinholes can also be caused by air bubbles that do not break until after the coating has dried. One culprit is vigorous mixing that creates too much foam. The number one way to prevent pinholes, craters, and similar defects is to clean and dry the surface before coating it.
In a cone 6 firing, adding a heating segment from 2050 up to 2230F @ 130F will resolve pin-holing issues. It allows the clay to completely off gas; thereby resolving your pin hole issues. However, additional heat work is also done by this slower heating segment, so you may need to lower your lithium additions slightly.
Disadvantages of the pinning and welding process: The device you choose is permanently affixed; you cannot remove it or replace it with another muzzle device.
Tensile and fatigue loads; bending, twisting, or flexing; as well as hot and cold expansion and contraction all can occur long after welding, be it two days, two months, or even two years. The major cause of a crack is when internal stresses exceed the strength of the weld metal, the base metal, or both.
Poor shielding gas coverage is the most common cause of welding porosity, as it allows atmospheric gases (N2 and H2) to contaminate the weld pool.
In high porosity hair, the cuticles appear open and spread apart. In low porosity hair, the cuticles look closed and tight together.
Anti-spatter compound can prevent spatter from accumulating on a part; however, it should be a last resort. Anti-spatter compound adds to an operation's expenses and has the potential to introduce weld defects like porosity.
Hot isostatic pressing (HIPing) is a process that can be applied as a post-casting treatment to reduce porosity in castings (Roberts, 2001). The process takes components up to a temperature of ∼80% of the absolute melting point, under pressures from 100 MPa to 210 MPa, for up to 6 h.
The impact of porosity can cause cracks in the weld joint, decreased ductility, and fatigue failure.
The sign of a quality and secure weld is that you will not see the weld at all. If there is any visible evidence of a weld, it will be in the form of a bead that has no holes or cracks and is uniform overall. A high-quality weld is made using high-quality materials.
TIG welding is the hardest form of welding to learn for a variety of reasons. The process of TIG welding is slow and takes time to get used to as a beginner. A TIG welder requires a foot pedal to feed the electrode and control the variable amperage while maintaining a steady hand at the welding torch.
It is simple to determine a good weld vs bad weld. A good stick weld will be straight and uniform. The thickness won't change drastically and there won't be drops of spatter. There are no holes, breaks, or cracks in the bead.