Nickel-chromium-molybdenum steels

Nickel-chromium-molybdenum steel 86XX and 87XX... 

Manganese-nickel-chromium-molybdenum steel 94XX... 

Selected mechanical properties of chromium and nickel-chromium-molybdenum steels are given in Table 9.20. Selected applications are shown in Table 9.21. 

Carbon content is usually about 0.15% but may be higher in bolting steels and hot-work die steels. Molybdenum content is usually between 0.5 and 1.5% it increases creep—mpture strength and prevents temper embrittlement at the higher chromium contents. In the modified steels, siUcon is added to improve oxidation resistance, titanium and vanadium to stabilize the carbides to higher temperatures, and nickel to reduce notch sensitivity. Most of the chromium—molybdenum steels are used in the aimealed or in the normalized and tempered condition some of the modified grades have better properties in the quench and tempered condition. 

Alloying elements such as nickel, chromium, molybdenum, and copper, which may be introduced with scrap, can increase the hardenability, although only slightly, because the concentrations are ordinarily low. However, the heat-treating characteristics may change, and for appHcations in which ductihty is important, as in low carbon steels for deep drawing, the increased hardness and lower ductiHty imparted by these elements may be harmful. 

Low-carbon, low-alloy steels are in widespread use for fabrication-welded and forged-pressure vessels. The carbon content of these steels is usually below 0.2%, and the alloying elements that do not exceed 12% are nickel, chromium, molybdenum, vanadium, boron and copper. The principal applications of these steels are given in Table 3.8. 

Steel is essentially iron with a small amount of carbon. Additional elements are present in small quantities. Contaminants such as sulfur and phosphorus are tolerated at varying levels, depending on the use to which the steel is to be put. Since they are present in the raw material from which the steel is made it is not economic to remove them. Alloying elements such as manganese, silicon, nickel, chromium, molybdenum and vanadium are present at specified levels to improve physical properties such as toughness or corrosion resistance. 

Chromium compounds Cr203 surface scale Nickel- chromium—iron alloys Nickel-chromium— molybdenum (tungsten) alloys Ni-Cr alloys analytical methods, 6 502-514 composition of metal compared to chromium ferroalloys, 6 501t dispersoid former, 2 325, 327 disposal, 6 519-521 economic aspects, 6 496—500 effect on cobalt alloys, 7 220 effect on stainless steel corrosion resistance, 7 809... 

Most modern industrial materials are designed to be passive i.e., covered by an adherent, chemically inert, and pore-free oxide that is highly insoluble in aqueous solutions and hence dissolves at an extremely slow rate. Examples would be modern stainless steels, nickel-chromium-molybdenum, and titanium alloys. The concept of passivity is often defined by reference to the polarization curve for metals and alloys in aggressive acidic solutions, Fig. 22. This curve defines the potential regions within which the alloy would be expected to corrode actively or passively. 

Explosively clad metals, of which Deta-Clad4 is an example, are used mostly for small items such as tube sheets and heads for small heat exchangers or vessels. It is usually not economical for large surfaces or complex shapes. Nickel-chromium-molybdenum alloys and some other expensive metals can be applied to carbon steel by explosive bonding. 

NOTE Other standard specifications exist for iow carbon, manganese, molybdenum, columbium and low carbon, nickel, chromium, molybdenum, and copper high-yield strength steels. 

Elements, which usually originate from alloyed steel scrap and non-ferrous metals in the steel charge, of the type which can be added to steels as alloying elements. They include nickel, chromium, molybdenum, copper, niobium and vanadium. Residual elements... 

Nickel-chromium-molybdenum alloys are used in reactor vessels in the production of acetic acid. These alloys are cost-effective compared to Ni-Cr stainless steels and have good resistance to oxidizing corrosive media Ni-Mo alloys have good resistance to reducing media. Molybdenum together with the chromium stabilizes the passive film in the presence of chlorides and is particularly effective in increasing resistance to pitting and crevice corrosion. 

Carbon steel IS 2002 Grade A, ASTM A 560, SA-516, A-179 Carbon-manganese steel Carbon-molybdennm steel Chromium-molybdenum steel Chromium-molybdenum-vanadium steel Chromium-nickel stainless steel Duplex steel, super duplex steel Non-ferrous alloys of Ni, Cu, Al, Ti... 

At higher elevations, there is fume and carry-over with the flue gases that cause deposits to form on the superheater, generating bank, and economizer tubes. Deposits may be molten depending on the concentrations of chloride and potassium. Superheater temperatures are usually between 300 C at the steam inlet and 500°C at the outlet. Although there are a variety of materials used in superheaters, ranging from chromium-molybdenum steels to stainless steels and nickel-base alloys, changing materials offers httle improvement when superheater deposits are molten. 

Metals are used in the cardiovascular area including heart valves, heart pacemaker leads, and heart pacemaker cases. These metals include titanium, titanium aUojrs, cobalt-chromium alloys, and cobalt-nickel alloys. Metals used for aneurism clips include cobalt-chromium-molybdenum alloys, cobalt-nickel-chromium-molybdenum allojfs, and, previously, stainless steels were used. Metal seeds are used for fractionated hyperthermia treatment of prostate disease, and corrosion analysis showed the alloy, PdCo may be suitable for the seed implants [52],... 

Ferritic chromium steels with < 13 % Cr 320 Ferritic chromium steels with > 13 % Cr 320 High-alloy multiphase steels 320 Ferritic/pearlitic-martensitic steels 320 Ferritic-austenitic steels/duplex steels 320 Austenitic CrNi steels 323 Austenitic CrNiMo(N) steels 323 Austenitic CrNiMoCu(N) steels 323 Nickel-chromium alloys 339 Nickel-chromium-iron alloys (without Mo) 339 Nickel-chromium-molybdenum alloys 339 Nickel-copper alloys 339 Zinc 343 Bibliography 344... 

---