Welding carbon steels

Manufacturing tolerances for steel, stainless-steel, and nickel-alloy tubes are such that the tubing is produced to either average or minimum wall thickness. Seamless carbon steel tube of minimum wall thickness may vaiy from 0 to 20 percent above the nominal wall thickness. Average-wall seamless tubing has an allowable variation of plus or minus 10 percent. Welded carbon steel tube is produced to closer tolerances (0 to plus 18 percent on minimum wall plus or minus 9 percent on average wall). Tubing of aluminum, copper, and their alloys can be drawn easily and usually is made to minimum wall specifications. 

The selection of materials for high-temperature applications is discussed by Day (1979). At low temperatures, less than 10°C, metals that are normally ductile can fail in a brittle manner. Serious disasters have occurred through the failure of welded carbon steel vessels at low temperatures. The phenomenon of brittle failure is associated with the crystalline structure of metals. Metals with a body-centred-cubic (bcc) lattice are more liable to brittle failure than those with a face-centred-cubic (fee) or hexagonal lattice. For low-temperature equipment, such as cryogenic plant and liquefied-gas storages, austenitic stainless steel (fee) or aluminium alloys (hex) should be specified see Wigley (1978). 

E6010, a low strength electrode, which is deeply penetrating and with easily removed slag. It is sometimes used for the root pass in welding carbon steel piping. 

ERW-Pipe. If run-of-the-mill pipe inconsistencies disturb you, and they should, inquire about ERW (electrical resistance welded) carbon steel pipe. This has more consistent properties than the usual steel pipe. You should be able to buy ERW-pipe for essentially the same price as pipe meeting your old specifications. 

Table 7-25. Welded Carbon Steel Pipe for Normal Duties-...

Table 7-26. Welded Carbon Steel Pipe Suitable for Higher Temperatures and Pressures-About 60,000 psi Ultimate Strength...

Allowable stresses for various ASTM code steel pipes at different temperatures are listed in Perry s "Chemical Engineers Handbook, 3d ed., pp. 1650-1651, and ASA B 31.1 Code for Pressure Piping. For example, St is 6,500 for butt-welded and 9,000 for lap-welded carbon-steel pipe at temperatures up to 250°F. 

Residual tensile stress resulting from fabrication is a major cause of stress-corrosion cracking. For example, welded carbon steel pipe can crack when exposed to a 10% caustic solution at 170°F or above. To avoid this failure, welded carbon steel piping sections that, even briefly, are exposed to caustic should be stress relieved. 

Stress relieving is accomplished by heating the fabricated section in a special furnace. Alternatively, process equipment may be stress relieved in the field by electrical heating. The operating engineer should insist that replacement welded carbon steel piping be stress relieved if caustic can enter the piping system. 

Suitable for welding carbon steels, alloy steels, stainless steels, aluminum, and other nonferrous metals. Table 24.3 lists recommended filler metals for GMAW... 

C. . Jaske, J.E. Slater, D. Brook, B. N. Leis, W. . Anderson, J.C. Turn and T. Omar, "Corrosion Fatigue of Welded Carbon Steel for Application to Offshore Structures", Interpretative Report submitted to API by Battelle Columbus Lab., Feb. 1, 1977. 

Grade WCC welded carbon steel casting, grade C JO2503... 

Propellers of inland vessels often work in very difficult conditions. This results in a fairly rapid mechanical consumption of propellers (abrasion and deformation). Propellers are also mostly performed in a technology giving low accuracy (welded carbon steel). Most of these results in negligently manufacturing of propellers (Dudziak, 1988). 

Caustic see of carbon steel occurs at temperatures above 50 to 80 °C (120 to 180 °F), depending on caustic concentration. Welded carbon steel components that are exposed to caustic solutions above these temperatures should be post-weld heat treated at 620 °C (115 °F) for 1 h per 25 mm (1 in.) of metal thickness. Caustic SCC of austenitic stainless steels occurs between 105 and 205 °C (220 and 400 °F), depending on caustic concentration. 

To avoid these failures, carbon steel is being replaced with Type 304L stainless. Others have stress-relieved welded carbon steel systems and have operated successfully, although elevated-temperature excursions are discouraged. 

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