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Tuesday, 5 May 2015

Welding Procedure

Assembling the Torch In Welding Procedure



By Welder Referer

The arc produced in TIG welding gives off very dangerous UV radiation. Even if one is to catch only a slight glimpse of the arc with the naked eye, one can expect to have a headache the next day. It is the responsibility of the welder to look after his/her own safety and the safety of others.

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Select the proper diameter electrode by consulting this document’s Appendix. It is necessary to correctly prepare the electrode tip to acquire a good weld. If DC welding will be performed, the end must be sharpened comparable to a pencil. 

The easiest way to accomplish this is to use the band-sanders inside the foundry.Turn on the sander, secure the electrode at of a 20° angle for the sander face, and rotate the electrode until a clear point is made. If AC welding will be performed, a rounded, conical tip is critical. In order to shape an electrode for AC welding, first sharpen it one would for DC welding. The second 50 % of the AC electrode preparation are going to be discussed later, following your rest of the products are up and running.

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Select a collet that is the same size as your electrode. The collets are often not in their proper bins, so double-check to see that it slides snugly around the electrode. Pick a cup with an appropriate orifice diameter to match the electrode (see Appendix). Screw the lens into the back of the torch, and then the cup over the lens from the front. 

Slide the collet around the electrode and slip the electrode through the lens and out the front of the torch. Then screw the electrode cap onto the back of the torch, thereby, covering the back of the electrode and locking it into place.The electrode should protrude between 1/8 and 1/4 of an inch out of the front of the torch.If it sticks too far out, loosen the cap and adjust it until it is in the appropriate position.


Grounding the Workpiece


One must make sure that electricity can properly flow out of the workpiece to ground. First, securely clamp the grounding cable to the welding table. Second, fixture the workpiece in a manner so that there is direct contact between the workpiece and the table.

Turning on the Equipment


First of all, check to see that the cooling water valve to the right of the welding machine is fully open (it should always be left open for safety’s sake). Then flip the main switch on the front of the welding machine to the ON position. Next, open the regulator valve on the top of the argon tank. It is a "double seating" valve which must opened all the way in order to properly seal.

It is usually a good idea to check that both the argon and the water are flowing properly. In order to do this, hold the torch in one hand so that it is not in contact with any metal and press down on the foot controller. This should start both the argon and the water flow. On the 300, you can look out the window behind the machine to see that the water is exiting the machine through the disposal tube. Check the flow meter on the argon regulator to see that the argon is flowing at the proper level. (See Appendix for suggested flow rates) Adjust the flow meter if necessary.


Joint Preparation


Proper cleaning of the metal can be essential in producing a solid joint. This is especially true with aluminum, where the pieces to be welded should always be scrubbed clean of all corrosion and dirt. Steel can usually be left as is, unless the pieces are extremely corroded.

Fixture the pieces to be welded in a fashion that allows for proper current flow between the workpiece and the table. Pieces usually do not have to be clamped together, but they should be well supported.

Protection


First, always set up the orange screens around the two edges of the welding table that face the rest of the room. These are crucial in protecting others. Next be sure that there is no exposed skin on the body of the welder. Wear the TIG welding gloves to protect one's hands and be sure that one is wearing only natural fabrics, since synthetics could melt if exposed to sparks from the welding. It is also a good idea to wear either a turtle neck or a shirt with the neck buttoned in order to be sure that one's neck is not exposed. Any unprotected skin can receive a nasty sunburn from overexposure.

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Next, put on an arc-welding helmet. Keep it in the upright position on your head until you actually weld. The one with the large smoked glass plate in the front provides a better field of vision than the others with smaller plates. The darkness of the glass is rated from 1 to 15. Be sure that the glass in your helmet is 11 or over.

Preparing to Weld

Sit at the welding table with your properly fixtured workpiece in front of you. Place the foot controller in front of your chair so that you can comfortably control it with your foot. Hold the properly assembled torch in the hand that you write with. Grasp it about half way along the shaft that connects to the hoses in the same manner as you would grip a pencil. Hold a piece of filler rod in your other hand if you intend to use it.

Starting the Arc

Since the welding machine features a high frequency start current, it is not necessary to make contact with the workpiece in order to start the arc. So place the torch at the point where you wish to begin the weld about with the tip of the electrode about 1/8” off the workpiece. Then lower the visor on the welding helmet. You will not be able to see anything until the arc has started. Call out “welding” so that everyone else in the room knows to avoid looking at the arc. 


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Press down nearly all the way on the foot switch and the arc should start. If it does not start (because you are too far away) slowly bring the electrode tip closer to the workpiece until the arc forms. Do not make contact with the workpiece as this can melt the electrode! The light of the arc should illuminate as small area around the torch so that you can see.

A common problem is to have the torch stray away from the intended starting position when the visor is lowered. A good trick in avoiding this is to actually touch the electrode to the intended starting point on the workpiece before lowering the visor. This will usually anchor the electrode enough so that it will not move when the visor is lowered. Then, bring the electrode slightly off the workpiece but keep it within 1/8” so that the arc will still start. Then press down on the foot controller to start the arc.



Source: http://www.stanford.edu/group/prl/documents/html/TIGweld.html
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