Metalworking throughout history
Milestones in welding process and equipment development
Metalworking began long before the Iron Age, and welding has undergone its share of developments throughout the centuries. How much do you know about its history and evolution?
At the time Solomon's Temple was believed to be constructed (mid-10th century BCE), there lived a man named Tubal-cain. He was said to be an instructor and artificer of bronze and iron and all other metals. Also written about that same time was this statement: "They will beat their swords into plowshares." As old as I am, I was not there for those events, but it is evident that the Iron Age was not the beginning of metalworking.
Sometime during the Middle Ages, the Iron Pillar of Delhi (Figure 1) was constructed. This is said to be the largest weldment made in this time period. The metalworking method of forging was becoming a common process used for all types of metal that could be forge-welded. This method was used in blacksmithing even in the 20th century. My grandfather made very strong fireplace tools in the 1940s by forging (Figure 2). Today it is used mostly by artists at arts and crafts fairs.
The Davys' Discoveries
The Davys are credited with two important discoveries in the early 1800s. Edmund Davy discovered acetylene, and Sir Humphry Davy discovered that two carbon sticks connected to a battery produced an electric arc. This became a usable welding process in the late 1800s and early 1900s that still is used today to weld galvanized sheet metal with cupro-bronze filler material. The arc between the two carbon electrodes places very little heat into the base material, barely affecting the galvanized material.
Gas welding, brazing, and cutting with oxygen and coal gas (would be good for West Virginia) or hydrogen came into their own in the late 1800s. Because of its low flash point and its expansion in any conventional container, storing acetylene was a problem. At one time an attempt was made to store it in a glass bottle. This proved to be catastrophic. Then a steel container was used, and it also was a failure.
The safest method at the time was to place the gas in a steel container filled with a concrete-like substance. The gas was absorbed in the porous material and became relatively stable. Later, a cylinder that contained a much lighter substance, similar to acoustic ceiling material, was found to be just as safe. This storage method continues to be used today.
An additional stabilizer, acetone, is in the cylinder, which is stored at 250 PSI for safety. A gas regulator set at 15 PSI or less also is a safety requirement for cutting or welding.
In the 1960s a fellow from Weston, W. Va., developed a torch that used gasoline and oxygen. He believed that it was safer than acetylene and much less expensive. It never really caught on because temperature variations caused liquid to be dispersed from the torch at times, which sparked fires adjacent to the operation.
World War I Push
World War I actually was the big push for the need for welding. The cost and efficiency of welding far outweighed those of the riveting process. Riveting required removing some material, and it was a two-person operation. Rosie the Riveter became Rosie the Welder.
Ships were being built in the U.S. and Europe using arc welding. This activity called for definition and standardization of welding language and usage.
In 1919 the American Welding Society was formed by the Wartime Welding Committee. A gentleman named Comfort Avery Adams led the effort and helped set the society's goals based on the criteria that it be "dedicated to the advancement of welding and allied processes." This mission statement remains broadly the same on the society's membership certificate.
Much controversy exists about who developed the shielded metal arc welding (SMAW) electrode similar to that used today. The case has been argued in many armchair courts of welding experts, and I will leave it alone.
Several developments in electrode technology occurred in the 1920s and 1930s. The coated electrode development is credited to the A.O. Smith Company. This company is no longer prominent in the welding industry, but is well-known in the home appliance industry, especially for its hot water tanks.
By the late 1920s, the coated electrode SMAW process was used extensively. The Lincoln Electric Company began mass producing coated electrodes that utilized extrusion for the coating rather than the former method of dipping. The coating not only improved the usability of the electrodes, but it also shielded the molten puddle from the oxygen/nitrogen atmosphere. It was believed that this atmosphere contributed to embrittlment and porosity in the weld.
Spot-method Identification. In the early days (when I was attending the Hobart school), electrodes were identified by spots painted on the coating. We were required to memorize the spot method of identification. I can still remember some of them. The E6010 had no spot. The E6012 had a white spot.
Our instructor, Howard B. Cary, gave us a clue for remembering another: "There are 12 white eggs in a dozen," and for E6013, "there are 13 brown eggs in a baker's dozen." Low-hydrogen electrodes had several spots of different colors.
We also had an instructor, Jerry Pfister, who had a riddle about the 1109 electrode. It is simply a box of E6011 turned upside down. It is great that electrodes now have the classification numbers printed on them.
High-deposition electrodes, such as E7024 and E7028, were referred to by Hobart as Rocket Rod and Lincoln as Jet Rod. I recall a Lincoln representative placing an E7024 in a Bernard Shortstub® electrode holder on a roller skate; it ran and burned off by itself on a steel plate. He sold lots of electrodes with this trick.
In the early days, the most prominent low-hydrogen electrode was Atom Arc, made by Alloy Rods. The selling point was that Atom Arc was packaged in a hermetically sealed metal container, and no moisture (hydrogen) could get in. For several years many companies specified Atom Arc as the only low-hydrogen electrode they would accept.
Developments in Shielding
While playing around with this theory of shielding, H.M. Hobart and P.K. Devers (I learned this at the Hobart Institute) came upon an idea to shield the electrode with an inert gas such as helium or argon. This was the forerunner of the gas tungsten arc welding (GTAW) process, although it was not patented by Hobart and Devers, but by Russell Meredith. It was later licensed to the Linde Air Products Company.
Hobart used helium in his process, which was called Heliarc® accordingly. It still was referred to as Heliarc into the 1960s and, in many cases, even today. This process lends itself to welding oxidation-intolerant materials. Argon is more commonly used now than helium. This is partly because argon is heavier than helium and because it is less costly. Helium now is considered a rare gas.
In the late 1950s or early 1960s I was involved with cutting some 1/8-in. nickel-alloyed material. I can't remember exactly which alloy, because trade names like MONEL®, INCONEL® weren't used in those days. Our customer was a coal-testing laboratory that specified this material that reportedly would resist the corrosion produced by the acid in the coal-testing process.
We attempted to use iron powder and an oxyacetylene torch to cut the material. This process involved sprinkling a thin layer of iron powder on the area to be cut and then using an ordinary oxyacetylene torch with a relatively low cutting oxygen pressure. The oxygen pressure was lowered to prevent blowing away the iron powder. The cutting was rough and required lots of grinding to remove the dross, but it was much faster and less expensive than using cutoff discs.
We then encountered a problem. We found that the iron powder residue caused porosity and cracking in the ensuing gas tungsten arc welds. We decided to call in some factory experts from Hobart, Linde, and Inco (now Special Metals).
Sometime in the 1950s, the Linde Air Products Company marketed a little-known process called "constricted arc cutting." This was before plasma cutting became the best way to sever nonferrous materials. The process consisted of a gas tungsten arc torch with a valve similar to the cutting valve on an oxyacetylene torch and a high-pressure regulator placed on an argon cylinder separate from the argon shielding gas cylinder. Believe it or not, this worked with no weld contamination. Still, a lot of grinding was necessary, and the argon was expensive.
Airco (Air Reduction Company) was the granddaddy of the gas metal arc welding (GMAW) process, also known as MIG. Actually, it was developed at Battelle with Airco's funding. The initial use of inert gases for welding on carbon manganese material was thought to be too expensive, so developers began looking for a less expensive gas. The winner was the plentiful CO2 gas, which, although not inert, produced a suitable shield and created superior penetration into the base material.
Today most fabrication shops use CO2 gas for the flux-cored arc welding process. The change from inert gas to CO2 gas prompted the American Welding Society to change the slang nomenclature MIG to "gas metal arc welding." The "I" in MIG was no longer properly definitive, since CO2 is a reactive, not inert, gas.
The GMAW process actually came into its own in the late 1950s and early 1960s. A high deposition rate and the ability to use several sizes and metallurgical types of filler metal were among its benefits.
The short-circuiting application method was introduced in the 1950s; it allowed welds to be made on thinner materials and from all positions.
The various gases available today, including mixed gases, have made it possible to weld almost all ferrous and nonferrous metals. Adding oxygen produces the spray transfer method of application for higher-deposition rates. Oxygen was a no-no before.
CO2 gas does not produce spatter-free welds on carbon/manganese material, but the mixture of argon and CO2 virtually eliminates the spatter on this material. The only detriment to the use of Ar/CO2 seems to be that it allows the manganese to build too high in multipass welds. This condition can cause embrittlement on the surface area.
For nickel and copper alloys, a mixture of argon and helium tends to produce high-quality welds with excellent appearance. The use of GMAW is limited to outdoor welding in winds greater than 5 MPH. For this reason, the process is used mostly in fabrication shops and seldom in construction or pipeline welding.
Shielding gas concerns and GMAW restrictions contributed to the use of the flux-cored arc welding (FCAW) process. The Lincoln Electric Company began producing a wire that did not require a shielding gas. It is called Innershield® and can be used in the same atmosphere as SMAW.
Another flux-cored wire that does require a gas shield is ESAB's Dual Shield, a high-deposition wire that is nearly hydrogen-free.
For hard surfacing applications, it is feasible to use the flux-cored wires with the submerged arc welding process. This allows for higher deposition rates and also lends itself to the addition of other alloys in the submerged arc flux. Additions of tungsten, cobalt, and borium, which are too hard to put in spooled wire, can be mixed in for additional hardness.
The submerged arc welding (SAW) process actually was developed by a pipe mill in Pennsylvania for welding longitudinal seams in pipe. (These welds now are mostly produced by resistance welding.) But like the GTAW process, it was licensed by the Linde Air Products Company and named Union Melt. This process is still the dominant process for resurfacing (building up) mine car wheels in West Virginia and other coal-producing states and in Europe. It once was once appropriately called the "smothered arc welding process," a fact that allows me to put a trick question on my exams for a terms and definitions class. The initials are the same, and on a multiple-choice test, I sometimes have some fun with it.
SAW often is used with tandem wires for making web-to-flange welds on welded plate girders for bridges and other "made-up" beams (Figure 3). The leading wire is placed in the root of the joint with direct current electrode positive (DCEP) to achieve root penetration, and the intermediate and cover passes are made with direct current electrode negative (DCEN) or alternating current (AC). This process may use either constant voltage or constant current.
DCEN or AC can be used on the upper beads to minimize undercut. This process makes welds at high deposition rates, often at 20 to 30 inches per minute or higher.
The Future of Metalworking
In the future, welding will continue to change dramatically. Fully automatic processes are being used in large fabrication shops. Positioners are being designed that turn in almost any configuration, allowing T joints, flanges, and pipe butt joints to be made without removing the weldment from the fixture. Fixturing now enables nearly all welds to be made in the flat position to enhance the travel speed, deposition rates, and weld quality. Positioning the workpiece makes it possible to utilize the spray transfer method of application for use with many different alloys.
Robots have become more versatile for general fabrication, even when not used for repetitive welding. Software that is readily adapted to almost any weld type or shape aids in quick change from one weldment to another with the click of a mouse.
Some machines can hang from the top of a tank to perform horizontal welds automatically (Figure 4). Also available is equipment that can make vertical welds up- or downhill automatically. In both cases the welder travels with the machine (Figure 5). Rarely do these machines need adjustment. Many were developed by end users and built by equipment producers, such as Koike Aronson. The president of Kanawha Manufacturing and I redesigned the machine pictured; Lincoln Electric and Koike Aronson built it to our specifications.
Much more machinery and equipment will be designed and built for specific uses in the future. There seems to be no end to innovation and development of equipment and procedures for advancing our welding industry.