Porosity is nothing more than bubbles in the weld. Surprisingly a weld can contain quite a bit of porosity without affecting the strength.
Porosity is the formation of bubbles in the weld.
Weld porosity is gas formations that did not escape prior to the weld solidification. These gases can be formed from water (which breaks down to hydrogen and oxygen atoms), oil, paint, rust or many other contaminants. The welding contamination can be on your welding materials as well as on the base metal (damp welding electrodes, etc.).
what must be done to prevent this from happening
Porosity is caused by molten puddle problems: oil, dirt, etc near weld, lack of shielding gas (tank is empty, or wind is blowing away gas. local vaccums for ventilation also can cause gas problems.) If mig welding, if you don't balance wire speed to amps, you may see porosity. Lastly, long arc'ing (too much distance from end of mig wire, to material) can cause bubbling.
Hi porosity is the gas pores (or) gas pocket travel deep in the solidified weld bead. Major causes $ Inadequate shielding gas $ Poor welding technique $ Damaged welding accessories $ Natural effects like wind flow
Porosity in welding is a result of dissolved gases or gases released during the welding process, being trapped in the metal when there is insufficient time to escape prior to solidification. If in the shape of rounded holes, the gas is called spherical porosity or just porosity. However, if elongated the terminology is wormholes or piping. Causes of porosity are;excessively long or short arc lengthwelding current too highinsufficient or moist shielding gastravel speed to fastbase metal covered with oil, grease, moisture etc.wet, unclean or damaged electrodes.
Electrodes with too much moisture may lead to cracking or porosity.
Check the shielding gas & its flow rate.
Sub arc welding is a process in which the welding actually occurs while submerged under a layer of flux. Not only does this prevent oxygen from entering the weld and thus porosity, but it also keeps the dangerous arc from sputtering and spattering from the weld.
J. Littleton has written: 'Gas-metal reactions and porosity in the inert gas arc welding of copper'
Porosity is the most common weld defect. For beginners don't rule out lack of penetration and non-compatible welding rod or filler wire. It all depends on how the weld failed if it has. Proper prep and preheat is required in many types of welding. So a little more detailed question can help me give you a more detailed answer. Trapped slag is also a common problem. It creates a void in the weld. Although porosity is the most common defect some porosity doesn't necessarily affect the weld strength.
Silicon is added to the tig rods in production. Use a gas weld rod which does not have the silicon and the weld will be full of porosity.