History of Electroslag welding in the US PDF Print E-mail

 

arc_logo

ARCMATIC

Welding Systems

1175 Nimitz Ave.

Vallejo, CA,  94592

THE HISTORY OF ELECTROSLAG WELDING

FOR HIGH RISE BILDINGS AND BRIDGES

William Bong,

president of Arcmatic Welding Systems


There was a boom in High Rise building fabrication in California during the late 1960's through the 1980's. During that time, One of the principals of, Arcmatic Welding Systems developed a method is increasing the speed and quality of welding moment plates (stiffeners) into High Rise building columns. The following structural steel fabricators were using the process extensively:

  1. Pittsburgh Des Moines Steel (Santa Clara, CA)
  2. Pittsburgh Des Moines Steel (Fresno, CA)
  3. Bethlehem Steel (Pinole Point, CA)
  4. US Steel - American Bridge Div (South San Francisco, CA)
  5. US Steel - American Bridge Div (Antioch, CA)
  6. US Steel - American Bridge Div (Los Angeles, CA)
  7. The Herrick Corporation - (Hayward, CA)
  8. Kaiser Steel - (Fontana, CA)
  9. Kaiser Steel - (Napa, CA)
  10. And others throughout the United States

Between the late 1960's and late 1980s, it is estimated that these fabricators collectively welded over a million stiffeners with the electroslag welding process in Northern and Southern California. Two of the tallest buildings in California were welded, using the electroslag welding process - The Bank of American building in San Francisco, and the twin tower Security Pacific buildings in Los Angeles. Countless smaller buildings were also welded during this period of time in the greater San Francisco bay area, the Los Angeles basin, and the San Diego area.

In (1970) I was working with several fabricators that were trying to solve the problem of welding closure weld on a moment plate in box columns. Prior to the advent of electroslag welding, fabricators would weld three plates of a box column together, then insert the moment plates into the box columns and weld all three sides to the three sides of the box. When the final cover plate was attached, the only way to make a full penetration weld was to slot the flange and spend a week filling in the final side of the moment plate. As High Rise building got much taller in California, the box columns on the bottom floors had continuity plates as thick as 6-inches. These welds were generally done with a SubArc Squirt welder, and took weeks to complete. When the electroslag process came along, a gap was left between the stiffener and the final cover plate. A hole was then cut in the top and bottom plates to allow for a sump and run-off - we dubbed this the "keyhole" welding procedure. It was found that the Vertical-Rate-of-Rise (VRR) had to be less than ½ IPM to produce a sound weld. This slower VRR created a weld nugget that was strong enough to support the stress created by the solidification of the weld puddle. One of the principals of Arcmatic was instrumental in setting creating the welding procedures to solve this most troublesome problem.

In Asian countries, structural steel fabricators use box columns, instead of rolled H-Beam columns for high-rise building fabrication. To weld moment plates into a box columns, they also use the electroslag "keyhole" methods developed by California fabricators the 70s. Over the last 35 years, every box column in the world has been made using the electroslag keyhole process. The electroslag process isn't anything new. Millions of welds have been made in high-rise buildings all over the world. So far, we don't have a record of any failures.

Another popular process for welding continuity plates into building columns was the multipass gasless flux cored wire process. This process was also used for field welding beam flanges to column flanges for field erection.

The Northridge Earthquake and the Loma Prieta Earthquakes provided a "real world" test to compare all of the welding processes. The Structural Steel welding industry is well aware that, over one billion dollars in crack repairs were needed, after the Northridge earthquake, to repair weld cracks propagated in welds made with the gasless flux cored wire process. Not one failure or one crack propagation was initiated in any of the hundreds-of-thousands of welds made on continuity plates welded with the Electroslag welding process.

In the history of the use of electroslag welding in the United States, to this authors knowledge, only one weld failure has ever occurred in an electroslag weld - where thousands of failures have occurred with the Submerged Arc Welding Process (SAW), The Gas Shielded Flux-Cored Arc Welding Process, and the Gasless Flux-Cored Arc Welding Process during this same period of time.

This one failure occurred on bridge flange in tension - subjected to reversal stress loading. Extensive research by a "blue ribbon" committee of University professors, and welding engineers determined that a bad weld repair, not the electroslag welding process, caused this one failure. If the same bad repair had been done with any other process, the weld would still have failed.

In the early 1980's, the Federal Government, under the guidance of the Federal Highway Administration (FHWA) set about an extensive investigation of the electroslag welding process with the purpose of increasing the physical properties for welding tension flanges on bridges, subjected to reversal stress loading. During this research period, they placed a moratorium on welding flanges with the process. The process continued to be used for structural applications under the AWS D1.1 Structural Code.

Contracts were given to, Northwestern University, Lehigh University, and the Oregon Graduate Institute (OGI). OGI came up with the best ideas to improve the physical properties of the electroslag welding process. They accomplished this by reducing the weld gap from 1-1/4", down to ¾" wide. The reduction in gap reduced the size of the Heat Affected Zone (HAZ) and increased the speed of the process.

The second major advance was to use a Metal-Cored Welding Wire, instead of a Solid Wire. Using a Metal Core welding wire made it much easier to change the wire chemistry. Nickel (Ni) was added to the chemistry of the wire to help increase the impact properties of the weld metal. The density of a Metal-Core welding wire is much less than a solid wire. This decrease in density allows the wire to melt as soon as it comes in contact with the 3500-degree molten weld puddle. The fast melting of the weld wire resulted in a shallower molten weld metal pool that lowered the resultant weld "form factor" - reducing or eliminating the potential for weld cracking. The process greatly improved the mechanical properties of an electroslag weld.

OGI conducted the initial research between 1980 and 1985. By the end of 1985 most of the basic research had been completed. The task then undertaken by FHWA was to convince the bridge industry of the superiority of the newly developed process. To accomplish this goal, they gave a contract to OGI to go to every State and demonstrate the process to Department of Transportation (DOT) Management. They called this new HIGH QUALITY electroslag welding process, Narrow Gap Improved - ElectroSlag Welding (NGI-ESW).

In 1993 Arcmatic Welding Systems was formed to take advantage of this superior welding process. Since the principals of Arcmatic had already designed and put into production the Continuity Plate welding process, using the original electroslag welding process (ESW); they felt that the advantages of welding

Continuity Plates with the new NGI-ESW process would give better physical weld characteristics to an already superior welding process.

Welding Continuity plates with multipass gasless, or gas shielded flux-core welding wire process has inherent problems that the NGI-ESW process eliminates. First, the weld has to be made into a backup bar that, in most cases should be removed and back gouged to insure a sound weld on the top and bottom of the moment plate. Second, each time a pass is made in a multipass weld, the base metal is first heated by the weld bead and then cools and stresses the weld joint. This puts the weld in tension. Each time a weld pass is made, tension in the weld joint is increased. The "K-Area" of the column is already work hardened and highly stressed because of the multiple rolling actions created when the column is formed. When a multipass weld passes over the "K-Area" of the column, the stress/strain increases. If this stress/strain becomes excessive, small cracks occur. Then either by fatigue or large stress/strain (as in the case of an earthquake) the small cracks will propagate and a weld failure will follow.

The 3500-degree molten flux puddle floating on top of the molten weld metal preheats the parent material, eliminating the need for preheating. The weld is done in one pass.

 

 

VERTASLAG (NGI-ESW) WELD SETUP

 


Prior to welding, the “K-area” is removed and the weld proceeds from the bottom of the flange to the top of the flange in one single pass. As the weld progresses vertically upward, it passes through a Keyhole in the web (where the K-Area has been removed). As the weld progresses through the web, either side of the K-area is annealed; eliminating both the work hardened area and residual stresses -practically eliminating the potential for crack propagation.

Arcmatic Welding Systems started welding continuity plates with the exact same equipment used by OGI to develop the NGI-ESW welding process. We soon found that equipment used in a University Lab by graduate students (working free of charge), was not the best equipment for structural steel fabricators – not all structural steel fabricators have welders working on their PHDs in welding. Arcmatic quickly discovered that the original equipment used by OGI had to have better controls so that less skilled workers could produce superior quality welds by letting the equipment control the welding variables. To accomplish this we decided to control of the variables of the NGI-ESW process with a computer program. This computerized welding control had to be robust and fool proof. After a welding program had been developed to create a perfect weld, all of the variables used to create that perfect weld had to be stored into a program and recalled when the same weld had to be repeated. We tried to take the decision process for making a perfect weld away from the hands of the operator.

Arcmatic took the NGI-ESW process and designed a welding system that made it possible for an unskilled welding operator to make a perfect weld every time. This computerized welding system, designed to use the NGI-ESW welding process is called by Arcmatic, the VERTASLAG welding system.

Arcmatic started the design of the VertaSlag welding system in 1993. We designed and perfected the equipment and the process from 1993-to-2001. During that time Arcmatic worked closely with one structural steel fabrication company – Cofab Steel in Vallejo, California. Cofab bid jobs and developed PQR’s that qualified each and every application to conform to the AWS D1.1 Structural Welding Code. Various jobs were performed over this 7- to-8 year period, generating Zero failures or weld defects.

Several of the jobs Cofab welded during this period included, (1) the fabrication of seismic structural members for the Bay Area Rapid Transit System (BART) that extended the BART tracks from South San Francisco to the San Francisco Airport, (2) the fabrication of heavy seismic retrofit columns for the San Francisco Opera House, (3) the fabrication of a large theater complex in Sacramento, (4) the fabrication of heavy column support structure for KFM to fabricate the Benicia Bridge project, (5) and many other projects.

In the year 2001, Arcmatic sold the first VertaSlag production system to Schuff Steel in Gilbert, Arizona for welding connection plates into high-rise building columns. To qualify to use the process for the city of Los Angeles, we had to submit, a full-scale test Column-Beam Moment Connection for their inspection. The seismic test was performed by, Smith Emery Testing Labs in Los Angeles.

Approximately 10 engineers from the city of Los Angels were there to witness the test. To pass, the test required a hydraulic ram deflect the beam, 4-inches (up-and-down 4-inches (a total of 8 inches of deflection). A chalky material was sprayed on the stiffeners and the beam-to-column flange welds to indicate stress lines after the test was performed. After deflecting the beam up-and-down 4-inches, chalk fell off the beam-to-column welds, but no chalk fell off the 2-1/2” thick VertaSlag welded moment plates. The city was satisfied, and we passed the test.

Since the equipment was already setup, Arcmatic asked Smith Emery Testing Labs to increase the deflection to (+/- 6)-inches, still no chalk fell off the VertaSlag welds or continuity plates. We continued to increase the deflection until the beam passed the yield point and permanently distorted. At (+/-) 12-inches deflection (the limit of the Hydraulic Ram Stroke) still no stress lines appeared, nor any chalk fell off of the VertaSlag welds areas - indicating low stress/strain in the weld area. After witnessing this test, the officials from the city of Los Angeles said additional testing was not required, and gave Schuff Steel and the VertaSlag Stiffener Welding Process approval for fabricating buildings in the City of Los Angeles

Since that test Schuff Steel has been welding building with the VertaSlag Stiffener welding process for the past eight or nine years. They later expanded the use of VertaSlag welding to their Phoenix plant and to their new plant in Ottawa, Kansas. They are currently welding the world’s largest hotel complex in Las Vegas, Nevada. Also participating in the fabrication of that project are, SME Steel in Salt Lake City, Utah; and others.

More than 20 companies have received either AWS D1.1 Structural Code approval (see the customers list on the WEB), or under the last printed D1.5 code (2009). These companies are welding on a variety of structural steel and bridge applications using the VertaSlag welding process.

There are over 15 companies that are now waiting for demonstrations to purchase Arcmatic VertaSlag welding system. The welding system is very cost affective, and produces superior quality welds for structural steel fabrication. All companies presently using, or planning to use the VertaSlag welding system are also using the system for “Tee” column fabrication to weld beam flanges to column flanges, and for welding the base plates onto the flanges of the columns.

The D1.5 Bridge Code Committee approve to include the NGI-ESW process in the next edition of the Bridge Code (2009). Now the process gain blanket approval for welding on tension flanges, subjected to reversal stress loading for bridge fabrication.

At this time there are several bridges being fabricated following the D1.5 provisions that were accepted and approved by the States’ DOTs. Twelve States have already approved the use of the process even before the last vote in D1.5 committee.

To help develop the new additions for NGI-ESW to be added to the AWS D1.5 Bridge Code, Arcmatic worked with Stupp Bridge, Trinity Industries, Williams Bridge, Jesse Engineering, the FHWA, TXDOT, and the NGI-ESW code committee. The combination of the fabricating companies submitted approximately 35 weld test results that all passed the last NGI-ESW code requirements.

In addition to the Tensil, Yield and Elongation these tests required that all welds be tested with five impacts from the weld metal and five tests from the HAZ (with the notch 1mm off the fusion line, in the parent material). All 35 welds passed all 10 Impact test requirements of 20 ft-lb at –200 F. This data was used by the AWS D1.5 Code Committee as a reference for their approval of the process.

Arcmatic is attaching a variety of information to this letter to show the amount of work that has done since 1980 to assure the quality of the NGI-ESW VertaSlag welding process. Arcmatic has always been on the leading edge of this development with process and components and systems. Our company has been a major contributor to the “state of the art” of welding by developing superior control over the welding process in an attempt to reduce, or eliminate, errors caused by unskilled welding operators.

 


 

 

 

 


 
Contact Us for More Information

Email: Keith Zimmerman or Call Him for More Information Tel: 707-643-5517 or 707-552-3232 Keith@arcmatic.com Sales@arcmatic.com  
331342
Visits TodayVisits Today105
YesterdayYesterday140
This weekThis week648
This monthThis month4530