Cast iron graphite


One production line of a paper mill consists according the size and the quality of the produced paper sometimes from more than 50 steam drums to dry and flatten the produced paper. These drums (cylinders with flat bottoms, see figure 1) will be used with a steam pressure up to 500 kPa (5 bar) and additionally with a rotation speed up 1200 m.min the material is mainly grey cast iron (with lamellar graphite). The diameters can reach up to 2.2 m and the cylindrical lengths up to 10 m. For the specific flattening drums the cyhndrical diameters can be up to 5 m and more.  [c.30]

Another case of selective corrosion is the graphitization of grey cast iron, resulting in preferential removal of the metallic constituent, leaving graphite. Here again the physical fonn of the casting is maintained, but it is devoid of any mechanical strength.  [c.2732]

Uses include flashlight photography, flares, and pyrotechnics, including incendiary bombs. It is one third lighter than aluminum, and in alloys is essential for airplane and missile construction. The metal improves the mechanical, fabrication, and welding characteristics of aluminum when used as an alloying agent. Magnesium is used in producing nodular graphite in cast iron, and is used as an additive to conventional propellants.  [c.29]

In general, siUca has proved to be a good material of constmetion for the burner. Cast iron, steel, or graphite was sometimes used. Gaseous HCl produced by this method is very pure and can be used to manufacture pure hydrochloric acid by the adiabatic absorption process (33) or falling film absorption process (34).  [c.445]

An ahoy of titanium containing 40—50% Ti and 45—50% Si is used as an additive in cast iron to shorten the graphite flakes. The effect is to provide a smooth casting surface. The resulting casting is then used to produce glass botde molds.  [c.541]

In metallurgical practice, sodium uses include preparation of powdered metals removal of antimony, tin, and sulfur from lead modification of the stmcture of siHcon—aluminum alloys appHcation of diffusion alloy coatings to substrate metals (162,163) cleaning and desulfurizing alloy steels via NaH (164) nodularization of graphite in cast iron deoxidation of molten metals heat treatment and the coating of steel using aluminum or zinc.  [c.169]

Tellurium also improves the properties of electrical steels by aiding in the magnetic anisotropy, malleable cast iron (77), and spheroidal (graphitic) cast irons (see also Metal surface TiiEATiffiNTs).  [c.392]

Diamond is the hardest (Knoop hardness ca 78.5 GPa (ca 8000 kgf/mm )) of all known materials. Both the natural (siagle-crystal) and synthetic (polycrystaUine siatered body) forms can be used for cuttiag-tool appHcations. Diamond tools exhibit high hardness, good thermal conductivity, abiUty to form a sharp edge by cleavage (especially the siagle-crystal natural diamond), low friction, nonadherence to most work materials, abiUty to maintain a sharp edge for a long period of time, especially when machining soft materials like copper and aluminum and high wear resistance. Sometimes if the surface of a tool material is somewhat rough, metal may be stuck ia the valleys of the tool surface and subsequent buildup can occur between this metal and the chips. Disadvantages of diamond tools iaclude extensive chemical iateraction with metallic elements of Groups (4—10) (IVB—VIII) of the Periodic Table (diamond wears rapidly when machining or grinding mild steel it wears less rapidly with high carbon alloy steels than with low carbon steel and is occasionally employed to machine gray cast iron (high carbon content) with long life) a tendency to revert at higher (ca 700°C) temperatures to graphite and oxidize ia air extreme britdeness (siagle-crystal diamoad cleaves easily) difficulty ia shaping and reshaping after use and high cost.  [c.216]

Antimony may be added to copper-base alloys such as naval brass. Admiralty Metal, and leaded Muntz metal in amounts of 0.02—0.10% to prevent dezincification. Additions of antimony to ductile iron in an amount of 50 ppm, preferably with some cerium, can make the graphite fliUy nodular to the center of thick castings and when added to gray cast iron in the amount of 0.05%, antimony acts as a powerflil carbide stabilizer with an improvement in both the wear resistance and thermal cycling properties (26) (see Carbides).  [c.198]

Metallurgy. SiUcon carbide is used extensively in ferrous metallurgy. When added to molten iron, a vigorous exothermic reaction takes place decomposing the siUcon carbide and resulting in a hotter melt. The effect is to deoxidize and cleanse the metal and promote fluidity. Thus a more desirable random distribution of the graphite flakes is achieved and a more machinable product obtained. Present practice is to add the siUcon carbide as briquettes to the cupola or in loose granular form to induction furnaces when producing cast iron (see Iron). When added as granules to molten steel in the ladle, it reduces the number of undesirable inclusions and leads to better physical properties in the product. When added as granules to steel in a basic oxygen furnace it extends the capacity of the furnace to melt more scrap as a result of the exothermic reaction.  [c.469]

Some diamond powder is produced commercially by shock-wave methods. The DuPont process (28) exposes small, well-crystallized graphite lumps in nodular cast iron to the brief, intense pressure generated by a suitable charge of high explosive. The graphite lumps are more compressible and reach much higher temperatures than the surrounding iron at the peak pressures, which last for a few microseconds, and part of the graphite turns into diamond. The carbon is cooled rapidly by the iron environment and the new diamond is thereby preserved. After recovery of the mass, the iron is dissolved and the diamond is separated by controlled oxidation of the graphite. The final product is a gray powder with particles ranging in size up to 30 p.m.  [c.564]

Cast Iron. Cast kons contain carbon (qv) as the main alloying element, are heterogeneous in microstmcture, and form an extensive family of materials that includes gray kon, compacted graphite, and ductile kon. The key to obtaining distinctive differences in properties between individual cast-kon types is the control of the carbon content and especially control of the morphology that graphitic carbon precipitates assume in the final product. Crystal morphology depends on tramp elements bound to the growing crystaUite surfaces.  [c.369]

Another type of corrosion is deaHoying which has also been called parting or selective leaching. DeaHoying (1 3) is the preferential removal of one of the alloying elements from an alloy resulting in the enrichment of the other alloying element(s). Common examples are the loss of zinc from brasses (dezincification) and the loss of iron from cast irons (graphitization) (see Copper alloys).  [c.274]

Steam manifolds for pressures up to 10 X 10 Pa are of cast iron. For higher pressures, the manifold is fabricated from plate steel, stay-bolted, and welded. The tubes are fastened rigidly to the manifold face plate and are supported in a close-fitting annular plate at the other end to permit expansion. Packing on the steam neck is normally graphite-asbestos. Ordinary rotating seals are similar in design to those depicted in Fig. 12-61, with allowance for the admission of small quantities of outside air when the dryer is operated under a slight negative internal pressure.  [c.1209]

Graphitic Corrosion Graphitic corrosion usually involves gray cast iron in which metalhc iron is converted into corrosion products, leaving a residue of intact graphite mixed with iron-corrosion products and other insoluble constituents of cast iron.  [c.2420]

Another group of cast-iron alloys are called Ni-Resist, These materials are related to gray cast iron in that they have high carbon contents (3 percent), with fine graphite flakes distributed throughout the structure. Nickel contents range from 13.5 to 36 percent, and some have 6.5 percent Cu.  [c.2443]

Cast iron, flake graphite, plain or low alloy 0 2 0 2 <400 1 < 750 Cast No Fair 45 6.7  [c.2446]

Changing the pump metallurgy to a more corrosion- and cavitation-resistant material, such as stainless steel, is a potential solution to this type of problem. Note, however, that all other cast iron pump components that have sustained graphitic corrosion should be replaced to avoid the possibility of galvanic corrosion (see Chap. 16) between retained graphitically corroded cast iron components and new components.  [c.285]

As the word dealloying implies, attack occurs only in metals containing two or more alloying elements. Various alloys are susceptible to corrosion. Copper alloys such as brasses, cupronickels, and bronzes are particularly susceptible in cooling water environments. Most other alloys, with the exception of gray and nodular cast iron (see Chap. 17, Graphitic Corrosion ), are attacked when exposed to high temperatures, molten salts, acids, sulfides, or other very aggressive environments.  [c.296]

Another form of microstructural galvanic corrosion, graphitic corrosion, is unique to gray and nodular cast irons. It may be encountered in cast iron pumps and other cast iron components. It is a homogeneous form of galvanic corrosion, not requiring connection to a different metal.  [c.358]

Cast iron (not graphitically corroded)  [c.360]

Similarly, graphitically corroded cast iron (see Chap. 17) can assume a potential approximately equivalent to graphite, thus inducing galvanic corrosion of components of steel, uncorroded cast iron, and copper-based alloys. Hence, special precautions must be exercised when dealing with graphitically corroded pump impellers and pump casings (see Cautions in Chap. 17).  [c.366]

Graphitic corrosion has two distinct features that are useful in distinguishing it from other forms of corrosion. First, it affects an unusually limited number of metals the only metals commonly affected are gray cast iron and nodular cast iron. Second, metal that has experienced graphitic corrosion may retain its original appearance and dimensions. Consequently, graphitic corrosion frequently escapes detection.  [c.373]

Graphitic corrosion is a slow corrosion process, typically requiring many years to effect significant damage. Complete penetration of thick cross sections has, however, occurred in as little as 2 years in adverse environments. On the other hand, cast iron components can be found in use in Europe after 160 years of service. Although graphitic corrosion causes a substantial reduction in mechanical strength, it is well known that corroded cast iron, when sufficiently supported, may remain serviceable when internal pressure is low and shock loads are not applied.  [c.374]

Figure 17.1 Flakes of graphite embedded in a matrix of iron (gray cast iron). Figure 17.1 Flakes of graphite embedded in a matrix of iron (gray cast iron).
The occurrence of graphitic corrosion is not location specific, other than that it may occur wherever gray or nodular cast iron is exposed to sufficiently aggressive aqueous environments. This includes, and is common to, subterranean cast iron pipe, especially in moist soil (Case History 17.1). Cast iron pump impellers and casings are also frequent targets of graphitic corrosion (Case Histories 17.2 through 17.5).  [c.376]

Failure of graphitically corroded cast iron will yield a brittle, thick-walled fracture. Fracture faces through the graphitically corroded region will be black and nonmetallic (Fig. 17.5). Cross sections cut through graphitically corroded regions will readily show bright, intact metal surrounded by a soft, black, corroded area (Fig. 17.6).  [c.377]

Figure 17.5 Brittle fracture through pipe. The gray material is graphitically corroded cast iron. Unaffected pipe wall metal is orange from normal rust. Figure 17.5 Brittle fracture through pipe. The gray material is graphitically corroded cast iron. Unaffected pipe wall metal is orange from normal rust.
Iron is usually prepared from oxide or carbonate ores, from which S, As, etc. have been removed by roasting in air, by reduction with carbon. The ore is mixed with coke and CaC03 and heated in a blast furnace, the maximum temperature of which is about 1300 C. The major acidic impurities are removed as slag (calcium silicate, aluminate, etc.) and the molten crude metal run off into pigs pig-iron contains 2-4% of carbon with a little P, S and Si. If the Si content is high, the C is present almost entirely as graphite on remelting and casting, such an alloy gives grey cast iron. If the Si content is low, the carbon is present as cementite, FejC, and gives white cast iron on casting. The sulphur content governs that of Mn, since excessive sulphur forms MnS, which is appreciably soluble in the slag. The cast irons are too brittle for many purposes. Wrought  [c.222]

Alloys with other useful properties can be obtained by using yttrium as an additive. The metal can be used as a deoxidizer for vanadium and other nonferrous metals. The metal has a low cross section for nuclear capture. 90Y, one of the isotopes of yttrium, exists in equilibrium with its parent 90Sr, a product of nuclear explosions. Yttrium has been considered for use as a nodulizer for producing nodular cast iron, in which the graphite forms compact nodules instead of the usual flakes. Such iron has increased ductility.  [c.74]

Ferrous XIeta.ls. In small concentrations, selenium decreases the surface tension of molten steel (qv) more than S, N, O, P, and C, but probably less than Te. In cast iron of low (0.02%) Mn content, selenium, in the presence of hydrogen, suppresses graphite nucleation and promotes carbide formation. However, at higher Mn levels graphite nucleation is favored. In steels, small amounts of Se act as a mild deoxidizer and selenium promotes fine-grained equiaxial crystals which minimize differences in directional properties, reduces hardenabifity, and is less sensitive to overheating and quench cracking. These properties result in improved steels for carburizing and hot-roUed appfications. Selenium is also added to steel to counteract, on hot rolling, the elongation of globular MnS inclusions frequendy encountered which lead to directional properties. It dissolves in the MnS, hardening the inclusion so that it will remain more oval during rolling. As fitde as 0.2% Se added to stainless steel casting alloys prevents the pinhole porosity ascribed to hydrogen.  [c.336]

As an effective and economical deoxidi2er, sihcon is used to refine most grades of carbon and ahoy steels. In importance to steelmaking, it is second only to manganese. As an ahoying element in steels, it increases tensile strength and elastic limits, improves resistance to corrosion and high temperature oxidation, improves electrical characteristics, and decreases yield point. As a reducing agent, it reduces metal oxides from slag, thereby permitting the desired element, such as chromium, to sink and be recovered as an ahoying agent. Sihcon in cast iron reduces the stabhity of iron carbide and promotes the formation of graphitic carbon. As an effective graphiti2er in cast iron, sihcon softens the iron and improves its fluidity and machinabhity. For wear resistance, sihcon in gray iron ranges from 0.50—1.50%. In ductile iron, sihcon ranges from 1.50 to 3.00%. Increased percentages of sihcon improve the corrosion and oxidation resistance of gray and ductile cast irons.  [c.539]

Ductile cast iron is made by converting the flakes of graphite in gray iron into tiny balls or spheruhtes by the addition of one or more elements to the molten metal. Magnesium, calcium, cerium, barium, or other elements produce spheruhtic graphite stmctures (29) magnesium and cerium (rare earth) are commercially important. The addition of 1.50—1.95% nickel to nodular iron significantly increases the strength of the pearhtic matrix. Conversion of graphite flakes into spheruhtes increases tensile strength and notch hardness of cast iron subsequent heat treatment produces desirable mechanical properties that cannot be obtained with iron-containing graphite in flakes.  [c.540]

Titanium—Silicon. The titanium—silicon ahoy is made by adding titanium scrap to molten metahurgical shicon or shicon ahoys. It is also made by carbon reduction of titanium ore, limestone, and quartz in a submerged arc furnace. Titanium—silicon ahoy is an efficient graphitizing inoculant for chill reduction in gray cast iron. It is also a supplementary deoxidizer for wrought and cast steels. The high calcium-based titanium shicon ahoy contains 50—60% Si, 9—12% Ti, 5—8% Ca, and 0.9—1.4% Al and is used primarily for steel deoxidization. The high calcium level permits deoxidization to occur with reduced aluminum additions. The titanium readhy combines with dissolved nitrogen in Hquid steels eliminating subsurface porosity. The low calcium grade containing 50—55% Si, 10—12% Ti, 0.5—1.5% Ca, 0.9—1.2% Al, and 1.2% Ba (max) is used primarily for inoculation of gray iron castings to eliminate nitrogen porosity.  [c.541]

A second, more recently developed use for strontium metal is as an inoculant in ductile iron castings. Inoculants provide nuclei upon which graphite forms during the sohdification of cast iron, thus preventing the formation of white cast iron. Elkem Metals Company has commercialized a range of fine-sized foundry inoculants for iron castings. These inoculants, called superseed, are ferrosiUcon alloys containing 50 or 75% Si, 0.8% Sr. Most of the balance is iron.  [c.473]

Cubic boron nitride (cBN), next only to diamond in hardness (Knoop hardness 46.1 GPa (ca 4700 kgf/mm )), was developed in the late 1960s (153—155). It is a remarkable material ia that it does not exist ia nature and is produced by high temperature—high pressure (HP—HT) synthesis ia a process similar to that used to produce diamond from graphite. Hexagonal boron nitride (hBN) is used as the starting material. Alkaline-earth metals and their compounds (iastead of Ni ia the case of diamond) are found to be the suitable catalyst—solvent for the production of cBN by the HP—HT process. Cubic boron nitride, although not as hard as diamond, is less reactive with ferrous materials like hardened steels, hard chill-cast iron, and nickel-base and Co-base superaHoys. It can be used efficiently and economically at higher speed (ca five times), with a higher removal rate (ca five times) than cemented carbide, and with superior accuracy, finish, and surface iategrity. Siatered cBN tools are fabricated ia the same manner as siatered diamond tools and are available ia the same sizes and shapes. Their costs are significantly higher than those of either cemented-carbide or ceramic tools because of higher processiag and shaping costs. Like the siatered polycrystaUine diamond tools, cBN tools are held on standard tool holders. In order to gain fuU potential of this material, very rigid precision machine tools with adequate speed and power capabiUties are recommended.  [c.219]

Cast Iron and Steel. Bearing surfaces can be machined directiy in gray cast iron stmctural parts for light loads and low speeds. The dake graphite in the cast iron develops a surface gla2e for carrying loads up to about 1.0 MPa (145 psi) at surface speeds up to about 0.8 m/s in pivots, lightly loaded transmissions, camshafts, and machinery bearings. With good alignment, clean and copious oil feed, and hardened and ground journals, loads range up to 4.5 MPa (650 psi) for main bearings in cast iron refrigeration compressors, and up to 5.5 MPa (800 psi) for connecting rods (21). A phosphate etched surface is often appHed as an aid for initial mn-in. Guide surfaces and journal bearings can also be inexpensively machined in stmctural steel parts for loads up to 1.4 MPa (200 psi) at speeds up to 0.8 m/s.  [c.5]

Cast Iron. Cast irons for enameling contain between 2.8 and 3.7 wt % carbon the more usual content is between 3.25 and 3.6 wt % (15). The carbon is usually found ia two forms graphitic carbon and combiaed carbon. Some additional elements ia the cast iron are siUcon, manganese, sulfur, and phosphoms. The cast iron known as gray cast iron is the most widely used for enameling purposes. Before enameling, a casting must be cleaned, usually by abrasively blasting the surface with sand or steel shot.  [c.212]

When the layer of graphite and corrosion products is impervious to the solution, corrosion wdl cease or slow down. If the layer is porous, corrosion will progress by galvanic behavior between graphite and iron. The rate of this attack will be approximately that for the maximum penetration of steel by pitting. The layer of graphite formed may also be effective in reducing the g vanic action between cast iron and more noble alloys such as bronze used for valve trim and impellers in pumps.  [c.2420]

Gray cast iron, low in cost and easy to cast into intricate shapes, contains carbon, silicon, managanese, and iron. Carbon (1.7 to 4.5 percent) is present as combined carbon and graphite combined carbon is dispersed in the matrix as iron carbide (cementite), while free graphite occurs as thin flakes dispersed throughout the body of the metal. Various strengths of gray iron are produced by varying size, amount, and distribution of graphite.  [c.2443]

The basic mechanism causing graphitic corrosion is easily understood, but some information is required on the microstructure of cast iron. The microstructural feature of principal importance is the distribution of flakes (gray cast iron) or spheroids (nodular cast iron) of graphite embedded in a matrix of iron (Fig. 17.1). Since graphite is highly noble from a corrosion standpoint and since it is in intimate physical contact with the relatively innoble iron matrix, it is easy to conceive of the formation of a microstructural galvanic couple between the graphite and iron if both are exposed to the same sufficiently  [c.373]

Experience has demonstrated that graphitic corrosion is favored by relatively mild environments such as soft waters, waters having a slightly acidic pH, waters containing low levels (as little as 1 ppm) of hydrogen sulfide, and brackish and other high-conductivity waters. It should not be inferred from this that gray or nodular cast irons are immvme to more aggressive environments but rather that graphitic corrosion is less likely in them. In more aggressive environments, corrosion may indeed occur but may be manifested as general metal loss rather than as graphitic corrosion. Moist soils, especially those containing sulfates, will frequently produce graphitic corrosion of unprotected gray and nodular cast iron. Stray currents have also been identified as causes of graphitic corrosion in subterranean pipelines. Finally, there is evidence that stresses may foster localized, relatively rapid graphitic corrosion.  [c.376]

Altering material or microstructure is a preventive rather than a remedial technique and therefore cannot be applied to existing equipment. When graphitic corrosion is anticipated, consideration should be given to specifying alternate materials. Nodular cast iron is less prone to serious graphitic corrosion than other cast irons, but it is not immune. White cast iron, which is essentially free of graphite, is immune to graphitic corrosion. Corrosion-resistant cast irons containing chromium, nickel, or silicon are essentially immune to graphitic corrosion. Austenitic cast irons are also immune, as are cast steels.  [c.379]

Note also that graphitic corrosion may occur preferentially in poorly accessible areas, such as the bottom of pipelines. Trouble-free service of cast iron components does not necessarily indicate that all is well, since components suffering severe graphitic corrosion may continue to operate until an inadvertent or intentional (e.g., pressuretesting) shock load is applied. At this point massive, catastrophic failures can occur.  [c.380]


See pages that mention the term Cast iron graphite : [c.85]    [c.523]    [c.2443]    [c.358]    [c.376]   
Corrosion, Volume 2 (2000) -- [ c.3 , c.48 , c.101 ]