Heliarc welding

In the design of equipment for the manufacture of sterile ophthalmic (and nonophthalmic) pharmaceuticals, manufacturers and equipment suppliers are turning to the advanced technology in use in the dairy and aerospace industries, where such concepts as CIP (clean-in-place), COP (clean-out-of-place), automatic heliarc welding, and electropolishing have been in use for several years. As a guide here, the reader is referred to the so-called 3A Standards of the dairy industry issued by the U.S. Public Health Service [267],... 

A heliarc-welded, all-nickel can of 850-mL volume was filled with an intimate mixture of NiF, (290 g, 3 mol) and anhyd KF (52 g, 9 mol). The can was valved to a tank of F2 gas and a vacuum pump and was heated by an electric-resistance furnace. The can was heated slowly to 500 C under 10 atm of F2 and then cooled to 250 C, while still under several atm of F2. Several such cycles were carried out before using the device for the regeneration of F2. For the regeneration of F2, the salt was fluorinated at 250 C until no more F2 was taken up. The can was then cooled to 225 C and evacuated to remove the excess F2 and any volatile impurities. The temperature was then raised until the desired F, pressure (at 400 C, 25 atm) was achieved. 

This diagram is intended for use with ORIGINAI barrel bushing. It is pressed in the front and heliarc-welded. This diagram was prepared from an actual uncut Sten and also Austen,... 

The vacuum chamber (Fig. 2) is a 20 x 39-in. stainless steel cylinder of all heliarc-welded construction. The chamber is suspended in an insulated aluminum tank. The chamber volume after correction for the pump lines and cryosphere was calculated to be 202 liters. This chamber size makes possible the use of commercially available standard leaks, without introducing significant errors in the time measurement when calibrating the gas analyzer by the rate of pressure rise method. The 7-in.-diameter cryosphere has a calculated surface area of 995 cm . The coolant transfer lines to the cryosurface are vacuum-jacketed to prevent possible condensation. 

The sun is the most notable source of ultraviolet radiation. Some other sources include heliarc welding. 

The base subassembly is welded using a tungsten-inert gas (TIG) process in an oxygen-free atmosphere (a process sometimes referred to as Heliarc welding) to produce a finished base unit. 

Figure 23, Heliarc torch used in welding as an example of the plasma jet...

Heliarc melding is used for stainless steels and most of the nonferrous materials. This process can be carried out manually, automatically, or semiauto-matically. A stream of helium or argon gas is passed from a nozzle in the electrode holder onto the weld, where the inert gas acts as a shielding blanket to protect the molten metal. As in the shielded-arc and submerged-arc processes, a filler rod is fed into the weld, but the arc in the heliarc process is formed between a tungsten electrode and the base metal. 

Answer by author Welding of the Invar is by the Heliarc process using ER-309 rod. Final inspection includes hydrostatic and gas pressure tests and a helium mass spectrometer leak test. 

Impact and tensile specimens were cut from 3/16 inch aluminum plate which was butt-welded with 5183 aluminum welding rod in a 60 single V by the heliarc method. The welding was accomplished under a helium atmosphere in two passes. In all, three plates were welded using a constant applied voltage of 60 volts. Current for the three plates, however, was regulated at 65, 75 and 90 amperes, respectively. 

In the investigation reported herein, the mechanical properties of type 301 stainless steel were studied at 70, -320 and -423 F in samples of steel that had been cold-worked 42, 62, and 78. Toughness was studied by means of notched tensile tests at the same temperatures, and a notch-to-unnotch tensile ratio was calculated. The latter was taken as a criterion of resistance to brittle fracture. In addition, the tensile properties of heliarc butt-welded joints of the same materials were determined. The welded joint data were included because low-temperature properties of welded joints are of practical importance in pressurized cryogenic propellant tanks. 

Table III. Tensile Properties of Heliarc Butt-Welded Joints in 301 Stainless Steel...

Fig. 4. Tensile strength (ksi) versus temperature ( p) for heliarc butt-welded 301 stainless steel.

The heliarc butt-weld tensile data of Fig. 4 and Table III again show the typical increase in tensile strength between 70 and-320 F, followed by a decrease and wide scatter between -320 and -423 F. The scatter in tensile data at -423 F are typical of many notch-sensitive materials. The annealed material present in the welded joint has been shown to be even more prone to occur in the austenite-martensite reaction due to the smaller number of defects present in its structure (the defects presumably block atomic shear movements which result in the martensite transformation) [2]. 

Answer by Author This joint is made by heliarc butt-welding the opposing ends of the sheet, roll-planishing the butt weld, and attaching a doubler strip that is resistance spot-welded to each side of the butt joint. All data reported pertain to the heavily cold-worked materials. 

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