Welding QC simple with real-time temperature readings

Beginning with battleships and submarines in World War II, most welders have relied on TempilStik, the simple surface-temperature indicator that delivers reliable and accurate results on temperatures from 200 ºF to 2000 ºF (38 ºC to 1093 ºC). Welders at the 38,000-square-foot Stainless LLC plant in Pine Forge, Pa., are no different. They continue to rely on their Tempilstik surface temperature indicators as they work on preheat and welding of the huge, heavy mild and alloy steel tower pieces.

Their supervisors and plant inspectors now are thinking very seriously of employing a new electronic device which makes it simple to take surface temperature readings and provides the actual temperature number. This new product provides a quick way to monitor values like preheat and interpass welding temperature as the supervisors move around the plant floor.

Called E-Stik, it is a product of Tempil, South Plainfield, N.J., an Illinois Tool Works Company. E-Stik employs micro-thermocouple technology to provide a large, quick digital readout of critical actual temperature at point of contact. It reads with ± 2% accuracy for surface temperatures from 32 ºF to 999 ºF (0 ºC to 537 ºC). The reading is immediate, with no need to correlate with any surface variables such as the emissivity of the surface material which is used on infrared thermometers.

Stainless LLC likes to keep its preheat temperatures in the range of 600 ºF to 650 ºF, and as the supervisor passes by the welder, he can quickly check out the temperature of the workpiece.

Stainless LLC has found preheating slows the cooling rate in the weld metal and base metal, producing a more ductile metallurgical structure with great resistance to cracking. This slower cooling rate provides an opportunity for hydrogen present to diffuse out reducing the potential for hydrogen induced cracking.

Preheating reduces the shrinkage stress in the weld and adjacent base metal, which is especially important in highly restrained joints, helping to avoid post weld heat treatment.

A beam-to-column connection made of ASTM jumbo sections (thicknesses ranging from four to five inches) is to be fabricated with a low hydrogen electrode, then a minimum prequalified preheat of 225 ºF. Making butt splices in jumbo sections, the pre-heat temperature is increased beyond the minimum prequalified level.

How construction proceeds

The 40-foot, mild-steel sections are standard at the plant, although sections up to 50 feet may be supplied. A 1,000-foot tower, for example, is fabricated in sections with flanges beveled just prior to welding. With all needed welding completed, the tower is taken apart, the sections are galvanized and it’s put on a truck to be shipped. At the site, it’s put together again like a giant Tinker toy.

Bottom sections of a high tower may be 3.5- to 4-inch steel; eight inches is usually the heaviest employed at Stainless LLC, although 11 inches has occasionally been supplied. The factory’s work is, of course, AIC qualified, audited and inspected.

E-Stik: important supervising tool

Stainless LCC considers the E-Stik an important supervising tool for foremen, supervisors and QA departments to make sure that preheat and interpass temperatures are as specified.

The self-contained E-Stik unit needs no cable. It is easy to carry around the yard and reads out in a button-selected choice of Fahrenheit or Centigrade in three to five seconds after the probe end touches the workpiece. When the E-Stik is removed from the workpiece, it resets with virtually no time lag.

Inspectors note that its red grip makes it easy to find; its flat shape with rounded corners means it won’t roll off if set down; and the backlit readout is helpful in tight corners.

Charles Leinback began at Stainless LLC with a summer job in 1962. He returned after graduation and began to move up through the company’s ranks. Today, he’s plant manager for the manufacturing facility.