Welder World Blog

Posts Tagged ‘stainless steel pipe’

Being a professional in any field is no easy task. It demands hard core and continuous smart work. Similarly, a professional welder needs to attain the certification for an adequate job. It is as difficult as passing a school test without preparation. There is equivalent nervousness and uncertainty involved in such tests.

If we get into the details of the kinds of tests for the pipe welding, we may get lost in it. Therefore, it is better to take an outline view of what is it all about? There are hundreds of pipe welding tests but two of them are more dominant. They are 2″ and 6″ schedule 80 pipes in the 6g position. The sad part is that these two joints need to be welded in various ways.

There are different ways for carbon steel pipe welding tests and stainless steel pipe welding certification tests. The former needs tig root pass with 7018 fill along with 6010 root pass having 7018 stick fill. The latter on the other hand requires tig throughout and it needs to be opened with stainless steel stick fill. Each of them has five different combinations. Once you complete all these operations, there are high chances that you will get Pipe welder certification get hired as a professional welder in paper mills, power plants, refineries, construction and maintenance sites.

Being a CWI Inspector implies that one needs to be aware of all the testing no matter what type it is. Since no one is perfect, it is good to go through some of the tips involved before you do any kind of welding. Before getting into the real deal of welding, one should weld a scrap metal first in order to get comfortable with the equipment and easy handling of further tasks of setting up the welding machine. Do follow the welding codes of getting arc strike within the range of the material to be welded.

Even after the welding activity has been performed, there are some finishing touches which must be taken into consideration. One should keep filing and brushing the finished product till the time all the stags are removed. To avoid any further mess, do all the starts and stops at one particular place. One should not chip around the hammer pecks all around. After everything is done, apply a little soapstone and then good power brushing which makes the welding shine brighter.

The standard welding processes such as TIG, MIG, and stick can be used to weld carbon steel pipe to stainless steel pipe. Standard carbon E-class welding electrodes such as  E70 and 7018 can be used for MIG and stick welding respectively. However, using such welding electrodes on this type of welding, the welding quality may be compromised due to lack of chromium and nickel in the alloy. Hence, it is important to use high-carbon stainless steel electrodes to have a strong weld joint between the steel and stainless pipes. In particular, type 309 welding electrodes have the correct composition ensuring a proper weld with correct penetration and structural integrity. Similarly, the following steps must be used in this type of welding:

Step-1: Load or spool the MIG welding machine with the type 309 welding wire after removing already loaded welding wire used for other jobs.

Step-2: Replace the gas with the three part shielding gas mixture. It is necessary to mix the gas thoroughly before attaching the gas bottle to the MIG welder. The method used is to place the gas bottle on the floor horizontally roll it back and forth to mix the gas thoroughly. After that fix gas gauges to the three-part gas bottle.

Step-2: Now switch on the MIG welder and adjust the correct heat and wire speed levels. It is essential to note that the standard heat settings (used for carbon steel) will not be adequate for welding stainless steel as higher amount of heat is required to weld stainless steel. Best advise is to refer your welding guide to verify the initial test setting for your heat and wire speed. Once you adjust the heat levels, carry out a test pass with the welder to see that the settings are correct.

Step-3: Cut a piece of stainless steel pipe and a piece of carbon steel pipe with required lengths using a band saw. It is important to note that when cutting stainless steel using a band saw, reduce the speed and at the same time use cutting fluid to keep the band saw blade cool.

Step-4: You need to have 20-degree bevel on end of the cut pieces of pipe. This is done using a grinder by holding it at a constant 20 degrees to give you an even fill line. Make sure not to touch the grinding pipes because the pipe will get very hot during grinding.

Step-5: Once the pipe edges are grounded correctly, place one beveled end of the steel pipe against the beveled end of the stainless steel pipe allowing a welding gap about 1/16th of an inch between the two pieces of pipe. Then place a tack at the weld joint to keep the pipes together. Similarly, roll the pipes and provide a tack at one inch interval around the entire circumference of the pipe. ItÕs necessary to maintain the 1/16th inch weld gap right through out the circumference.

Step-6: Now start welding the pipes together. Start the weld from the stainless steel pipe and gradually pull the puddle onto the carbon steel pipe. Also, roll the MIG gun in a circle to flow the puddle to create good weld while watching the bottom of the weld to make sure proper penetration. During the welding process, if you note that the carbon pipe is under-cutting, it is necessary to reduce the heat on the MIG welder and repeat it.

Related Welding Bottles Articles