Steels continued welding

In the case of long continuously-welded steel pipelines the above pipecoating methods present the disadvantage that the joints have to be coated in the field after welding. To overcome this difficulty equipment which travels along the welded pipeline has been developed. 

For instance, for a 304 stainless steel welded seam pipe with an outside diameter of 3V2", to find the maximum internal pressure allowed for this pipe, use the pressure formula. Find what is called the stress value for a particular material (in this case 304 stainless steel) which is based on that material and the way it was fabricated - whether it is seamless, continuous welded, electric resistance welded, or electric fusion-arc welded. Most of the materials that you will run into will be ERW (electric resistance welded ) and thus have a seam, or will be seamless with no weld. The same material of a given diameter and thickness will be able to withstand higher internal pressure if it is seamless. 

All surfaces liable to receive contamination during station normal operation are protected either by continuously welded, stainless steel liners or by applied high efficiency decentamlnable coatings. 

Unlined plain steel pipes are sometimes installed with sacrificial thickness. This is particularly the case with continuous welded underground pipelines. The reader should refer to Chapters 9 and 11 for some of the particular approaches used to select materials for different slurries. Some slurries such as laterite and taconite has been found to be very abrasive with HOPE pipes. 

The cell case is formed out of a rectangular tube continuously welded and formed from a nickel-coated steel strip and a laser-welded bottom cap. The cell case forms the negative pole. 

If the hole is to be formed with a steel wall sleeve, the outside diameter of the sleeve must be fitted with a 2-in. collar around its entire circumference to anchor it into the concrete wall and prevent water from migrating around the outside of the sleeve. This collar must be continuously welded on both sides to ensure that water will not run under it, and the wall sleeve must be round, clean and free of weld slag. 

Austenitic Steel weld has a well defined transcrystalline (oriented) macrostructure with continuously changing orientation of the crystal axis - from the periphery towards the centre the angle between the axis of the crystal and the axis of the weld is changed from 90 to 0 degrees. Weld metal eould be possible to approximate in the form of a discrete combination of crystals with parallel axes of the crystallites. 

Eor steel and other ferromagnetic materials, property deterrnination is more difficult. Other tests are made to measure the continuity of protective metallic coatings. Residual stresses induced in welded stmctures and in components in service owing to chemical attack may contribute to early failure. 

Forming-Die Alloys. The tonnage of slab zinc used in this appHcation is small. The use of zinc alloy dies started in the aircraft industry during World War II (119). Zinc-based alloys cast in sand and plaster molds continue to be used for short-mn dies for steel and aluminum stampings in the automotive and aircraft industries (120). Considerable cost savings are realized with these low melting zinc-based alloys which are easy to poHsh, machine, weld, and remelt. 

In the United States calcium carbide-based acetylene is mainly used in the oxyacetylene welding market although some continues to be used for production of such chemicals as vinyl ethers and acetylenic alcohols. Calcium carbide is used extensively as a desulfurizing reagent in steel and ductile iron production allowing steel mills to use high sulfur coke without the penalty of excessive sulfur in the resultant steel (see Sulfurremoval and recovery). Calcium cyanamide production continues in Canada and Europe (see Cyanamides). 

The largest use for calcium carbide is in the production of acetylene for oxyacetylene welding and cutting. Companies producing compressed acetylene gas are located neat user plants to minimize freight costs on the gas cylinders. Some acetylene from carbide continues to compete with acetylene from petrochemical sources on a small scale. In Canada and other countries the production of calcium cyanamide from calcium carbide continues. More recentiy calcium carbide has found increased use as a desulfurizing reagent of blast-furnace metal for the production of steel and low sulfur nodular cast iron. 

The triggering mechanism for the corrosion process was localized depassivation of the weld-metal surface. Depassivation (loss of the thin film of chromium oxides that protect stainless steels) can be caused by deposits or by microbial masses that cover the surface (see Chap. 4, Underdeposit Corrosion and Chap. 6, Biologically Influenced Corrosion ). Once depassivation occurred, the critical features in this case were the continuity, size, and orientation of the noble phase. The massive, uninterrupted network of the second phase (Figs. 15.2 and 15.21), coupled... 

New alloys with improved corrosion-resistance characteristics are continually being marketed, and are aimed at solving a particular problem, e.g. improved stress-corrosion cracking resistance in the case of stainless steels improved pitting resistance or less susceptibility to welding difficulties. 

Stainless steel coil and sheet stock is unloaded and stored outdoors under protective cover. As it is needed, the coil stock is moved indoors by a forklift to one of six automatic tube mills where the sides of unrolled metal strips are curled up to form a continuous, cylindrical pipe. The seam of the resulting pipe is fused in an electric in-line welding operation. An abrasive saw is used to cut the continuously formed pipe to specified lengths sections of poorly welded pipe are cut away. 

The reactor assembly was heated by electric heaters. The maximum operating temperature Is determined by the window construction. Sapphire windows (from EIMAC), brazed into Kovar sleeves, were used the sleeves were then welded directly into the stainless steel reactor housing. We found that the cell so constructed was capable of trouble-free, continuous operation at 450°C operations at somewhat higher temperatures are probably still possible but were not explored. Sapphire was chosen as a window material because it is insensitive to water vapor and is transparent in tljie wave number range of our interest (about 2400 cm to 2000 cm in these experiments). Moreover, the thermal expansion characteristics of the reactor were found to match well with those of the window fixture. 

A square stainless steel pad (5 in X 5 in X 1/8 in) is welded to a vessel that is used for high-temperature service (1200°C). The welder welds continuously around the pad, forgetting to leave an opening for a vent. Compute the pressure change between the pad and the vessel if the temperature changes from 0°C to 1200°C. 

The cracking susceptibility of a micro-alloyed HSLA-100 steel was examined and compared to that of a HY-100 steel in the as-received condition and after heat treatment to simulate the thermal history of a single pass weld. Slow strain rate tensile tests were conducted on samples of these alloys with these thermal histories in an inert environment and in an aqueous solution during continuous cathodic charging at different potentials with respect to a reference electrode. Both alloys exhibited reduced ductilities at cathodic potentials indicating susceptibility to hydrogen embrittlement. The results of these experiments will be presented and discussed in relation to the observed microstructures and fractography. 

Casting, continuous sheet casting between stainless-steel belts, pouring and several methods in the molten state are usable extrusion, injection, compression, thermoforming, co-injection, machining, welding. Specific grades of PMI can be foamed. 

Typically, coatings most often in use as intermediate layers are silver, nickel, copper, and gold however, silver is used by far the most often. This is so because of the low dissociation temperature of silver oxide, making it relatively easy to obtain clean surfaces. Also, the typical thickness range of electroplates used, in practice, for diffusion welding is about 15 to 40/rm, but thicknesses as great as 130 )um must sometimes be used. A considerable variety of steel types as well as aluminum and a host of other difficult-to-join metals and even beryllium have been and continue to be diffusion bonded with the use of electroplated intermediate layers. 

In the recently introduced continuous methods of nitroglycerine manufacture nitrators made from acid resistant steel are used since the art of welding stainless steel had progressed remarkably by the 1930 s. The design and construction of nitrators for nitrating glycerine are included in the descriptions of individual methods of nitration. 

---