Teknologi Las Kapal identifying TIG WELDING Tungsten Inert

Teknologi Las Kapal identifying TIG WELDING (Tungsten Inert Gas) (

I CAN v I can describe the TIG operating principles and procedures v I can compare and contract the TIG advantages and disadvantages v I can distinguish the different tungsten rods and their application v I can explain the use of the TIG shielding gases Teknologi dan Rekayasa

Tungsten Inert Gas (TIG) Welding v Produced by an electric arc maintain between non consumable tungsten electrode and the part to be welded. v The heat affected zone, the molten metal and the tungsten electrode are all shielded from the atmosphere by a blanket of inert gas fed through the TIG torch. § Gas serves to blanket the weld, exclude the active properties , does not burn and adds nothing to the bead. Teknologi dan Rekayasa

Basic Equipment Teknologi dan Rekayasa

TIG Welding Process Teknologi dan Rekayasa

TIG Welding Process v Produce temperatures of up to 35, 000 F v Torch contributes only heat to the work piece v Filler metal is required to make the weld § Added manually like brazing. Teknologi dan Rekayasa

Advantage of the TIG Process v Weld more kinds of metals and metal allow. § Stainless steel, nickel alloys, titanium, aluminum, copper, brass v Also can weld dissimilar metals to each other. § Copper to brass § Stainless steel to mild steel. Teknologi dan Rekayasa

Other Advantages v Concentrated Arc § Pin point control of heat input to the workpiece. § Narrow heat affected zone § This is where the base metal has undergone a change due to the superheating of the arc and fast cooling rate. v No Slag v No Sparks, Spatter or Noise v No Smoke or Fumes Teknologi dan Rekayasa

TIG Disadvantages v Low filler metal deposition rate. v Need hand eye coordination to accomplish the weld v Arc Rays are brighter than normal welding. v Need additional care to protect skin with proper clothes and welding lens. Teknologi dan Rekayasa

TIG PARAMETER v Two basic parameters in welding § Amount of current § Amount of voltage. v Current number of electrons flowing past a given point in one second. v Voltage Amount of pressure induced in the circuit to produce current flow. v Resistance represented by the welding arc, cables, connections and internal components Teknologi dan Rekayasa

Alternating Current v Has both negative and positive half cycles v Current flows in one direction during one half of the cycle and reverses directions Teknologi dan Rekayasa

Teknologi dan Rekayasa

Frequency v Rate at which alternating current makes a complete cycle of reversals v United States the rate is 60 cycles per second (60 hertz) v As frequencies goes up, the arc gets more stable, narrows and become stiffer and more directional. Teknologi dan Rekayasa

Types of AC v Sine Wave Normal cycle of AC current v Square Wave Done with electronics, ability of positive and negative transition almost instantaneously. Effective use of energy produce a square waveform. v Advance Squareware Incorporates switching electronics capable of switching currents up to 50, 000 times per second. Teknologi dan Rekayasa

Control Wave Teknologi dan Rekayasa

Types of AC v With the technology AC is made up of direct current electrode negative and the direct current electrode positive Teknologi dan Rekayasa

Direct Current v DC electrical current that flows in one direction only. § Water flowing through a pipe. v Polarity Electrical charge the electrode is connected for , such as direct current electrode negative (DCEN) or direct current electrode positive (DCEP) v Three welding current type and polarity § Direct Current Electrode Negative § Direct Current Electrode Positive § Alternating Current (combination of both electrode negative and electrode positive polarity. Teknologi dan Rekayasa

Direct Current Electrode Negative Straight Polarity v Used for practically all metals. v Torch is negative v Work is connect to positive v Electrons flow from neg. to positive work. v 70% of heat on positive side; heat is distributed into the work. v Deep penetration neg + Teknologi dan Rekayasa

Direct Current Electrode Positive Reverse Polarity v Torch is connect on the positive terminal v Work is connected to the negative terminal. v Electrons flow from negative to positive, electrode is on the negative side. Electrons are leaving the work. v 70% of heat is on positive side and more into the electrode. v Electrode has to be large. v Used for nonferrous metals, as a cleaning form. v USED ON ALUMINUM Teknologi dan Rekayasa

Pulsing v Varying the current from a high peak amperage level to a lower background amperage level at regular intervals. v Pulse controls also adjust for the number of pulse per second and the percent of time spent at the peak amperage level. v Pulsing is used to control heat input and allow for improved weld profile. Teknologi dan Rekayasa

Duty Cycle v The number of minutes out of a 10 -minute time period an arc welding machine can be operated at maximum rated output. v An example would be 60% duty cycle at 300 amps. This would mean that at 300 amps the welding machine can be used for 6 minutes and then must be allowed to cool with the fan motor running for 4 minutes. Teknologi dan Rekayasa

TIG Welding Torch v Majority of heat goes into the arc something must be used to remove the wasted heat. v Torches may be either water or air cooled. v Air cooled torches are popular for lower amperage application. They require no additional cooling other than the surrounding air. Teknologi dan Rekayasa

TIG Welding Components v Collect body screws into the torch body. It is replaceable and is changed to accommodate various size tungstens & collets. v Collets held in the torch by the collet. Made of copper, Grip on the electrode is secured when the torch cap is tighten in place. v Need good electrical contact between the collet and tungsten electrode is essential for good current transfer. Teknologi dan Rekayasa

Torch Part Teknologi dan Rekayasa

Torch Part Teknologi dan Rekayasa

TIG Components v Gas Lenses replaces normal collect body. Is used to reduce turbulence and produce a longer undisturbed flow of shielding gas. v Gas Nozzles made of various heat resistance materials. A nozzle will allow only a given amount of gas to flow before the flow becomes turbulent. v Coolers air cooler v Remote Control § Set at 100% , the more it is depressed the more current flows v Running Gear and Cylinder Racks Teknologi dan Rekayasa

Shielding Gas Protects the molten weld pool from the atmosphere. Without this protection, the molten metal reacts with gases in the atmosphere and produces porosity (bubbles) in the weld bead greatly reducing weld strength. Teknologi dan Rekayasa

Argon v Obtained as a byproduct in the manufacturing of oxygen. v Argon as a liquid temperature is – 300 F. v Cylinder size 330 cubic feet at 2640 psi at 70 F. v Argon provides excellent arc stability and cleaning action. v Has low thermal conductivity which means it is not a good conductor of heat. Arc density refers to the concentration of energy in the arc. With argon this energy is confined to a narrow or more “pinpointed” area. Teknologi dan Rekayasa

Flow Gage v Correct flow rate is an adequate amount to shield the molten weld pool and protect the tungsten electrode. v Influenced by: welding current, nozzle diameter, electrode and position § Corner or edge joints, excessive flow rates can cause air entrapment, effectiveness is improved by reducing the gas flow by about 25% Teknologi dan Rekayasa

Preflow and Postflow v To prevent contamination of both the weld pool and the tungsten electrode by the surrounding atmosphere. v Preflow will clear the air and moisture from the torch and prevent this contamination. v Postflow prevent oxidization from occurring by shielding the hot electrode and weld area and by speeding up the cooling process. v If tungsten that has discolored because of oxidization must be properly removed. Teknologi dan Rekayasa

Tungsten Electrode v Color Codes v EWCe-2 (2% Cerium, Orange)—all purpose electrodes that work with AC or DC electrode negative. Ground to modified Point v EWLa-1 Lanthana (Black) Similar performance to thoriated tungsten. Easy arc starting, good arc stability, long life, high current capacity. Teknologi dan Rekayasa

Tungsten Electrode Teknologi dan Rekayasa

Electrode Preparation v Pointed End. Used for Electrode negative little heating affect on the tungsten and a sharp pointed tungsten is preferred. v Pointing of electrodes grind the taper for a distance of 2 2 ½ diameter in length for use on DC & usually to a sharp point. 1/8” electrode ground to ¼ to 5/16 long. Teknologi dan Rekayasa

Electrode Preparation Teknologi dan Rekayasa

Electrode Preparation Teknologi dan Rekayasa

GRINDING v Marks run lengthwise with the point. v Stone needs to be clean not used for anything else. v Contamination particles can lodge in the grinding crevices and dislodge during welding, ending up in the deposit. v Proper prepared tungsten will reduce or eliminate arc wandering, splitting and poor weld quality. Teknologi dan Rekayasa

MATERIALS FOR TIG WELDING ⇒ Absolute cleanliness is vitally important! ⇒ When working with Cr. Ni, use only Cr. Ni tools ⇒ Only work aluminium with Cr. Ni tools that have only ever been used for aluminium and never for steel Teknologi dan Rekayasa

MATERIALS FOR TIG WELDING Aluminium v On butt seams, always slightly round off the rootpenetration side, otherwise an "oxide notch" may result v A larger weld-preparation angle is needed than on steel v V-welds: max. 80°, generally with no root-face! v Gap root width > 2 mm, if possible use a backing support (Cr. Ni, poss. ceramic - but not Cu) v Weld I-seams (square butt welds) without a gap. Degrease sheets - in some cases re-baking will be necessary, as the oxide skin occasionally contains H 2, (with acetylene flame = reducing effect) When working with thicker materials, preheating may be necessary because of the large heat radiation that takes place; with He mixtures, pre-heating will not be necessary in some cases. Teknologi dan Rekayasa

MATERIALS FOR TIG WELDING Cr. Ni v As small a weld-preparation angle as possible, as Cr. Ni is a poor thermal conductor. There is a risk of very great distortion. Weld at the coolest temperatures possible -> overheating, burn-off of alloy elements, rootshield protection is necessary because of oxidation Teknologi dan Rekayasa

Knowledge is the key to success Teknologi dan Rekayasa