WAYS TO WELD

[Music] Welding is very much a 20th century development and skill. The industrial revolution of the 19th century occurred virtually without it. And while ancient artisans fused gold and brass to fashion jewelry, welding as we know it today had to await a number of things to happen. First, there was the need for controlled high temperatures available widely with the mixing and burning of industrial gases. Welding had to await advances in metallurgy. Welding also had to await further knowledge and sophisticated techniques for the generation and use of electricity. not widely available in the 19th century. Yet today, there are over 40 welding processes, some of the most advanced employing a beam of electrons and even a beam of concentrated light, the laser. History aside, a clear understanding of welding and its wide variety can be found through examining just five of the major welding processes available today. [Music] here. The welder is demonstrating gas welding. He ignites a mixture of oxygen and acetylene gas coming through his torch under pressure. Now he concentrates the flow of the gas and increases the heat using the torch. He is simply melting both pieces of metal in a controlled manner to join them together. Gas welding. It requires skill but it is an easily learned technique. Gas or oxy acetylene welding is one of the most versatile of welding processes. [Music] Here the welder is joining two pieces of metal by fusion welding. Using the torch he is melting both pieces of metal while at the same time melting the metal rod. The result is a melting and fusing of both the metal pieces and the rod into one solid piece. Let's look at another variety of gas welding called braise welding. Here the welder is going to join a metal collar to a piece of pipe. They are dissimilar metals. Now in braise welding, he uses his torch to heat the pipe and collar to a red glow, while the rod he uses is made of bronze. The bronze melts at a lower temperature than the work pieces and forms the bond between the pipe and the collar. [Music] The basic equipment you need for gas welding are a cylinder of oxygen and a cylinder of fuel gas. More often than not, acetylene. You need regulators to control the flow and pressure of the gases to a welding torch. And then you're ready to weld. Take a close look at gas welding right at the torch tip. And you can see that the intense heat of the oxygen and acetylene which does the melting is a cone within an envelope of acetylene and air. The envelope tends to protect the melting metal from contamination. Another feature of the versatile gas welding process is simply by changing the torch you can use the same equipment to cut metals. Here, the welder can quickly cut through this length of pipe [Music] and oxy acetylene cutting or gas cutting is widely used in a variety of industries. The technique can be highly automated and controlled here by an optical scanner which reads a template of the shape to be cut and directs four torches. You can even use computerized controls for oxy acetylene cutting of steel plate as much as 10 in thick. And there are machines available which will employ up to 10 cutting torches all working together and with precision. Here's a large shop where stainless steel is being welded for nuclear plants. One of the welding processes being used here is the stick electrode or shielded metal arc process. With this process, you need electricity. So you require a power source or generator, cable, a ground clamp, an electrode holder, and an electrode. Electricity flows from its source through the circuit and back to the source. But in arc welding, the electricity must jump a slight gap between the electrode and the work surface. This electric arc is hot enough to melt both the electrode and the two pieces of metal to be joined. The welding electrode used in this process is coated with a bakedon material called flux. The flux protects the molten weld metal from the air around it which would contaminate and weaken the weld. The welder here strikes an arc by touching the electrode to the workpiece. Quickly, he pulls the electrode back about an eighth of an inch to maintain his arm. Once solidified, the weld will be stronger than the original metal pieces. Incidentally, this certified welder is just 18 years old. [Applause] Let's take a look at a metal arc welding process called MIG or gas metal arc welding where we have a power supply controls shielding gas a continuous electrode and miles of wire on a spool. With a 14-in electrode in stick electrode welding, you have to add a new electrode every few minutes. With MIG welding, you can weld practically without interruption. [Music] Look at it this way. We need a power supply to provide the welding current. We need shielding gas, an electrode in the form of wire on a spool, all coordinated from a central box which controls welding current, gas flow, and wire feed speed. Then we need a conduit to guide the electrode to the torch. a hose which carries the shielding gas into the torch and a power cable to carry the current to the torch. These are the essentials of MIG welding. There are several variations of MIG welding. One, where you use carbon dioxide as a shielding gas or argon or a mixture of carbon dioxide and argon. and two where you use a cord wire instead of a solid wire. Cord wire is a hollow wire which is filled with a fine sandlike flux similar to the flux on the electrode in stick electrode welding. With the MIG welding process, the welder can preset his current, rate of gas flow, and wire speed before he starts to actually weld. This frees him to concentrate on his welding without interruption. Those constant starts and stops in stick electrode welding, for example, where he would have to change his electrode every few minutes. The MIG welding process is clean, fast, and produces little smoke. [Music] [Applause] [Music] A fourth major welding process is gas tungsten arc welding called TIG welding. It's primarily a manual process and requires a high degree of skill. It can be used without filler metal rod as demonstrated here. [Music] TIG welding resembles MIG welding in many ways. You need a power supply and shielding gas. You need one cable and clamp to provide a ground. You need another cable for electricity and hose for shielding gas and sometimes water for cooling the torch. You need a torch and you need an electrode. You need a solid non-consumable electrode which doesn't melt into the well. The TIG electrode is made of tungsten. TIG welding is used primarily for light metals and where high quality welds are needed. High pressure piping and piping used in nuclear power generators. Filler wire is used for welding heavy gauge metals. While TIG welding is primarily a manual process, it can be mechanized for long straight line welds. The skilled individual's control and mastery of the process can be seen in the weld itself. And this one is a beauty. Submerged arc welding is another process introduced to provide automatic welding on thick pieces of metal. Here again you need a power supply, ground cable, wire contact tube, a wire feeder, and an integrated control box. The electrode wire is much heavier than the wire used in MIG welding. It is supplied in coils for continuous feeding into the weld area. Additionally, you need flux and a flux hopper. You can mount it all on a traveling carriage which will move along an I-beam track. In this process, the ark and the entire welding process takes place beneath a blanket of flux which protects the weld from contamination. Here, instead of moving the welding rig along the workpiece, the submerged arc unit is held steady while the workpiece is rotated beneath it. It was the first automatic welding process and is still today the fastest, cheapest, and most reliable way of welding heavy steel plates such as used in ships, boilers, and other large structures. Here, two pieces of structural steel will be welded by consumable guide electro slag welding, a process similar to submerged arc welding. The two steel plates are attached by a sump at the bottom. Now, the operators will clamp copper plates on either side of the gap. The welding unit is positioned over the gap and a fluxcoated tube is installed around the welding wire. When the ark is struck, the edges of the steel plate, the fluxcoated tube and the welding wire all meet and fuse. Flux from the tube lies a top the molten metal and shields it from the air. The operator adds flux as needed. Electro slag welding deposits very large quantities of metal very quickly. Welds as high as 40 ft have been made with this process. This process is used in the vertical position only. Resistance welding is a process used on light gauge steels. You place two non-consumable electrodes on either side of the workpiece and zap. You send a strong current between the two electrodes under pressure and fuse the two pieces from one electrode to the other. Ultra pulse welding is an advanced form of resistance welding. Here, your two electrodes are cylindrical and fit around the lug nuts to be welded. Zap. It happens so fast, the workpiece isn't even too hot to handle. With ultra pulse welding, you have better control and can make more critical welds than with resistance welding. Plasma arc welding is an advanced welding process which uses a highly concentrated stream of ionized gas to develop an extremely high temperature up to 30,000° F. You can see the ark pierce the workpiece. It's a high-speed continuous process used for metals up to a/4 of an inch thick. [Music] The plasma arc process can be used for cutting most metals quickly, including hard to cut metals such as stainless steel and aluminum. Electron beam welding is another advanced welding process. It employs a highowered beam of electrons that can penetrate up to 6 in of steel. The beam is the same as that produced by the electron gun in an ordinary TV picture tube, except that it is hundreds of times more powerful. [Music] The process is worked in a vacuum chamber for best performance. It is one of the purest welding processes available and was originally developed for critical aerospace welding where the highest quality welds are essential. Laser welding is another advanced welding process where a concentrated beam of light is used to fuse or cut metals. It can be used with a variety of thin metals including stainless steel and aluminum. The process lends itself to a high degree of control and automated welding of difficult configurations as the film shows. [Music] Gas welding, stick electrode welding, MIG, TIG, and submerged arc welding are but a few of the welding processes available. A basic knowledge of these five processes will help you to understand all welding processes. But knowledge alone, while valuable, is not enough to become a highly skilled and expert welder. It's a matter of taking things into your own hands and doing it. [Music] Heat. Heat. [Music]