Nickel-steel, 9-percent

Nickel Steel Low-carbon 9 percent nickel steel is a ferritic alloy developed for use in cryogenic equipment operating as low as —I95°C (—320°F). ASTM specifications A 300 and A 353 cover low-carbon 9 percent nickel steel (A 300 is the basic specification for low-temperature ferritic steels). Refinements in welding and (ASME code-approved) ehmination of postweld thermal treatments make 9 percent steel competitive with many low-cost materials used at low temperatures. 

For chemical service the necessary parts are available in 3.5 percent nickel steel monel Hastelloy C Stainless Type 316, 304, etc. plastic coated bellows nickel silver nickel plated springs and other workable materials. 

Cr-8Ni stainless steel (SS d aluminum or 9 percent nickel steel required... 

Nickel Steel. Steels containing 3-1/2, 5 and 9% nickel also require impact tests to determine their suitability for low temperature operation. The 3-1/2 and 5% nickel steels may be used down to -150°F and require stress relief after welds and forming operations. Nine percent nickel steel requires no stress relief and is usable down to -325°F, however, valves, fittings, and piping are not readily available. 

The fluorocarbons are generally compatible with most of the common metals except at high temperatures. At elevated temperatures, the following metals resist fluorocarbon corrosion (and are named in decreasing order of their corrosive resistance) Inconel, stainless steel, nickel, steel, and bronze. Water or water vapor in fluorocarbon systems will corrode magnesium alloys or aluminum containing over 2 percent magnesium. These metals are not recommended for use with fluorocarbon systems in which water may be present. 

Anhydrous phosgene in the liquid state is compatible with a variety of common metals, including aluminum (of 99.5 percent purity), copper, pure iron or cast iron, steel (including cast steel and chrome-nickel steels), lead (up to 250°F or 12 PC), nickel, and silver it is also compatible with platinum and platinum alloys in instruments. Nonmetallic materials with which liquid anhydrous phosgene is also compatible include acid resistant linings (ceramic plates and carbon blocks), enamel on cast iron or glass-lined steel, Pyrex or Kimax, porcelain, quartzware, granite or basalt natural stone, stoneware, and Teflon. 

SAE 780 tin, silicon, and copper alloy, and SAE 770 using tin, copper, and nickel are aluminum alloys which have been widely used in medium- and heavy-duty diesels (6). With siUcon and cadmium incorporated for improved compatibiUty, both SAE 781 and 782 are used as an 0.5 mm to 3.0 mm overlay on a steel backing with a thin electroplated babbitt overlay. Traditional 6% tin—aluminum is also used as the SAE 780 alloy with an overlay. Eleven percent siUcon alloys are used for highly loaded diesel bearings in Europe. 

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. 

Stainless Steel There are more than 70 standard types of stainless steel and many special alloys. These steels are produced in the wrought form (AISI types) and as cast alloys [Alloy Casting Institute (ACI) types]. Gener y, all are iron-based, with 12 to 30 percent chromium, 0 to 22 percent nickel, and minor amounts of carbon, niobium (columbium), copper, molybdenum, selenium, tantalum, and titanium. These alloys are veiy popular in the process industries. They are heat- and corrosion-resistant, noncontaminating, and easily fabricated into complex shapes. 

Austenitic stainless steels are the most corrosion-resistant of the three groups. These steels contain 16 to 26 percent chromium and 6 to 22 percent nickel. Carbon is kept low (0.08 percent maximum) to minimize carbide precipitation. These alloys can be work-hardened, but heat treatment will not cause hardening. Tensile strength in the annealed condition is about 585 MPa (85,000 Ibf/in"), but workhardening can increase this to 2,000 MPa (300,000 Ibf/in"). Austenitic stainless steels are tough and ducdile. 

Thermal Expansion. Alloys differ in their thermal expansion, but the differences are modest. Coefficients for the ferritic grades of steel are perhaps 30 percent below those of the austenitic steels at best, while expansion of the nickel-base austenitic types may be no more than 12 to 15 percent less than tho.se of the less expensive, iron-base, austenitic, heat-resistant alloys. Unfortu-... 

Replacing some of the nickel with iron produces a family of alltws with intermediate corrosion resistance between stainless steels and the Ni-Cr-Mo alloys. Alloys such as Incoloy 825 and Hastelloy G-3 and G-30 are in this family. Incoloy 825 has 40 percent Ni, 21 percent Cr, 3 percent Mo, and 2.25 percent Cu. Hastelloy G-3 contains 44 percent Ni, 22 percent Cr, 6.5 percent Mo, and 0.05 percent C maximum. These alloys have extensive applications in sulfuric acid systems. Because of their increased nickel and molybdenum contents they are more tolerant of chloride-ion contamination than are standard stainless steels. The nickel content decreases the risk of stress-corrosion cracking molybdenum improves resistance to crevice corrosion and pitting. Many of the nickel-based alloys are proprietary and are coverecf by the following specifications ... 

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