arc stability characteristics. Helium is used in automated  welding and when heavier base metals or deeper penetration  is required.  Care must be taken to ensure that the heat affected zones  and the root side of the titanium welds are shielded until  the weld metal temperature drops below 800 °F. This can  be accomplished using shielding gas in three separate gas  streams during welding. and procedures required to produce an acceptable arc  weld. Additional instruction and information pertaining  to arc welding of other metals can be obtained from  training institutions and the various manufacturers of the  welding equipment.  The first step in preparing to arc weld is to make certain that  the necessary equipment is available and that the welding  machine is properly connected and in good working order.  Particular attention should be given to the ground connection,  since a poor connection results in a fluctuating arc, that is  difficult to control. When using a shielded electrode, the bare end of the electrode  should be clamped in its holder at a 90° angle to the jaws.  (Some holders allow the electrode to be inserted at a 45°  angle when needed for various welding positions.)  Before starting to weld, the following typical list of items  should be checked: Titanium weld joints are similar to those employed with  other metals. Before welding, the weld joint surfaces must  be cleaned and remain free of any contamination during the  welding operation. Detergent cleaners and nonchlorinated  cleaners, such as denatured isopropyl alcohol, may be used.  The same requirements apply to the filler rod, it too must  be cleaned and free of all contaminates. Welding gloves,  especially the one holding the filler, must be contaminate free.  A good indication and measure of weld quality for titanium  is the weld color. A bright silver weld indicates that the  shielding is satisfactory and the heat affected zone and  backup was properly purged until weld temperatures  dropped. Straw-colored films indicate slight contamination,  unlikely to affect mechanical properties; dark blue films or  white powdery oxide on the weld would indicate a seriously  deficient purge. A weld in that condition must be completely  removed and rewelded.  The welding arc is established by touching the base metal  plate with the electrode and immediately withdrawing it a  short distance. At the instant the electrode touches the plate,  a rush of current flows through the point of contact. As the  electrode is withdrawn, an electric arc is formed, melting a  spot on the plate and at the end of the electrode.  Correctly striking an arc takes practice. The main difficulty  in confronting a beginner in striking the arc is sticking the  electrode to the work. If the electrode is not withdrawn  promptly upon contact with the metal, the high amperage  flows through the electrode causing it to stick or freeze to  the plate and practically short circuits the welding machine.  A quick roll of the wrist, either right or left, usually breaks  the electrode loose from the work piece. If that does not  work, quickly unclamp the holder from the electrode, and  turn off the machine. A small chisel and hammer frees the  5-25 Arc Welding Procedures, Techniques, and  Welding Safety Equipment Arc welding, also referred to as stick welding, has been  performed successfully on almost all types of metals. This  section addresses the procedures as they may apply to  fusion welding of steel plate and provides the basic steps  1.  The first shielding of the molten puddle and adjacent  surfaces is provided by the flow of gas through the  torch. Manufacturer recommendations should be  followed for electrodes, tip grinding, cup size, and  gas flow rates. 2.  The secondary, or trailing, shield of gas protects  the solidified weld metal and the heat affected zone  until the temperature drops. Trailing shields are  custom-made to fit a specific torch and a particular welding operation. 3.  The third, or backup, flow is provided by a shielding  device that can take many forms. On straight seam  welds, it may be a grooved copper backing bar  clamped behind the seam allowing the gas flow in the  groove and serving as a heat sink. Irregular areas may  be enclosed with aluminum tents taped to the backside  of welds and purged with the inert gas.  •  Is the proper personal safety equipment being used,  including a welding helmet, welding gloves, protective  clothing, and footwear; if not, in an adequately  ventilated area, appropriate breathing equipment? •  Has the ground connection been properly made to the  work piece and is it making a good connection? •  Has the proper type and size electrode been selected  for the job? •  Is the electrode properly secured in the holder? •  Does the polarity of the machine coincide with that  of the electrode? •  Is the machine in good working order and is it adjusted  to provide the necessary current for the job?