Cast iron high-chromium cast irons


Regular 75% ferrosiUcon is widely used for deoxidizing and alloying additions to iron and steel that do not require tight control of residuals. This ferrosihcon is ideal for ladle additions because its higher siUcon content permits smaller additions in order to reach desired siUcon levels. The slight exothermic nature of 75% ferrosihcon is also desirable from the standpoint of ladle heat balance. Regular 75% ferrosihcon and 90% ferrosihcon grades are used mainly for high ahoy cast steels that require large additions of shicon. Regular 75% ferrosihcon can also be used to reduce the chromium oxide in the slag of stainless steel produced by the argon oxygen decarburization (AOD) process. Because 75% ferrosihcon is not quite as dense as steelmaking slags, additions are best added to the ladle during tapping or refining.  [c.540]

Carbon disulfide is normally stored and handled in mild steel equipment. Tanks and pipes are usually made from steel. Valves are typically cast-steel bodies with chrome steel trim. Lead is sometimes used, particularly for pressure reUef disks. Copper and copper alloys are attacked by carbon disulfide and must be avoided. Carbon disulfide Hquid and vapor become very corrosive to iron and steel at temperatures above about 250°C. High chromium stainless steels, glass, and ceramics maybe suitable at elevated temperatures.  [c.31]

Materials and Pressure Ratings Valves must be constructed from materials that are sufficiently immune to corrosive or erosive action by the process fluid. Common body materials are cast iron, steel, stainless steel, high-nickel alloys, and copper alloys such as bronze. Trim materials usually need a greater immunity due to the higher fluid velocity in the throtthng region. High hardness is desirable in erosive and cavitating applications. Heat-treated and precipitation-hardened stainless steels are common. High hardness is also good for guiding, bearing, and seating surfaces cobalt-chromium alloys are utilized in cast or wrought form and frequently as welded overlays called hard facing. In less stringent situations, chrome plating, heat-treated nickel coatings, and ion nitriding are used. Tungsten carbide and ceramic trim are warranted in extremely erosive services. See Sec. 28, Materials of Construction, for specific material properties.  [c.787]

The drum drier is heated by steam, which enters through the trunnion. The condensate is discharged by means of a scoop or syphon through the second trunnion. Rotation of the drum varies with duty but, in general, will be between 4 and 10 rpm. The drum for the single atmospheric drum drier is a single casting, the face turned true on a lathe and then ground and polished. The materials are cast iron, bronze, or chrome-plated. For dimensions, a drum 5 ft in diameter and 12 ft long is large. Smaller sizes generally are a 24-in. diameter drum, 24 to 36 in. long. Figure 32 shows an atmospheric single-drum drier with dip feed. Besides the knife, a spreader is shown, which regularizes the coating. The heat from the condensing steam passes through the condensate film, through the metal of the drum, and then through the coating on the drum. The maximum rate of evaporation for a dilute solution, which gives up its water more readily than a concentrated one, is as high as 20 lb of water per hour per square foot of drum surface. This, however, only indicates that a high rate of evaporation may be obtained. As the purpose of drum drying is, rather, to produce a quantity of dry material, the true measure of efficiency is the number of pounds of finished product per unit heating surface. The rate of evaporation is determined by the concentration at which the material is fed to the drier. The capacity of a drum drier depends on its dimensions, the speed of rotation (the greater the speed, the greater the discharge, with the reservation expressed below), and the initial concentration of the liquor or slurry it will depend, furthermore, on the residual moisture allowable in the product, on the heat resistance of the liquor film, on the steam pressure, and on the adhesion of the coat to the surface. The better the adhesion, the heavier is the coating and, therefore, the greater the amount dried in a unit time for a given drier.  [c.137]

It consists of a hollow, cylindrical metal drum lying on its side trunnions that permit its rotation a sturdy, straight, adjustable knife and a shallow feed pan into which it dips. A large gear mounted on one trunnion is driven by a pinion actuated by motor or pulley. A cast-iron or welded steel frame furnishes the supports. The drum is cooled by water or brine introduced and wasted through the trunnions. A coating of liquid forms on the drum as it dips in the feed pan as the drum turns, the film at once begins to cool, so that after traveling about three-fourths of the rotation, it is hard and solid. It meets the knife, which scrapes it off, the coating breaking into flakes, chips, or other fragments characteristic of the material. The flakes drop into an apron from which they may be shoveled into shipping drums, or they may drop directly into a screw conveyor that moves them to a chute and packing boxes or barrels. The drum is usually made of a special grade of cast iron with a very smooth surface, which may be chromium-plated. The drum is also made of stainless steel, nickel, or bronze. The motion is generally a steady rotating one, but for certain products it has been found better to move the drum in a series of short jerks. Successful application of the flaker depends upon a low adhesion of the solidified material to the surface of the drum. Should the adhesion be too high, the knife will be unable to lift off the solid and will ride on the material instead of on the drum. The adhesion of some troublesome materials is lessened by a wetting roll, which leaves a film of moisture on the metal just before the coating is formed.  [c.158]

Because of its mechanical properties and the difficulties associated with its production, high-chromium iron is mostly used in environments which are particularly aggressive to other cast alloys. It is most useful for handling acid waters containing oxidising agents, for example mine waters and industrial effluents. Because many of these waters tend to contain solid matter in suspension, which can lead to abrasion of metals exposed to them, the very hard high-chromium iron is often the most suitable material for pumps handling these solutions. There is always a possibility that abrasive slurries  [c.614]

The data available suggest that the high-chromium irons do not offer any better resistance to alkalis than unalloyed grey iron, which would normally be preferred in view of its lower cost and its mechanical properties.  [c.617]

Fig. 7.20 Long-term growth (increase in length %) at temperatures of 350°C and 400°C in flake graphite and nodular cast irons, a, high carbon (3 - grey iron, b engineering grey iron, 3-2% carbon, c nodular graphite iron, d engineering grey iron, 3-15% carbon large section casting with coarse but widely dispersed flake graphite, e engineering grey iron alloyed with up to 0-5% molybdenum and/or up to 0-5% chromium Fig. 7.20 Long-term growth (increase in length %) at temperatures of 350°C and 400°C in flake graphite and nodular cast irons, a, high carbon (3 - grey iron, b engineering grey iron, 3-2% carbon, c nodular graphite iron, d engineering grey iron, 3-15% carbon large section casting with coarse but widely dispersed flake graphite, e engineering grey iron alloyed with up to 0-5% molybdenum and/or up to 0-5% chromium
Fig. 7.21 Long-term scaling (increase in weight related to surface area) at temperatures of 350°C and 400°C in flake graphite and nodular cast irons. a high carbon (3-7%) grey iron. b engineering grey iron, 3-2% carbon, c nodular graphite iron, d engineering grey iron, 3 15% carbon large section casting with coarse but widely dispersed flake graphite, e engineering grey iron alloyed with up to 0-5% molybdenum and/or up to 0-5% chromium Fig. 7.21 Long-term scaling (increase in weight related to surface area) at temperatures of 350°C and 400°C in flake graphite and nodular cast irons. a high carbon (3-7%) grey iron. b engineering grey iron, 3-2% carbon, c nodular graphite iron, d engineering grey iron, 3 15% carbon large section casting with coarse but widely dispersed flake graphite, e engineering grey iron alloyed with up to 0-5% molybdenum and/or up to 0-5% chromium
Ferrous materials steel, cast iron, iron, stainless steel, high-silicon iron, high-silicon molybdenum iron, high-silicon chromium iron, magnetite, ferrite.  [c.163]

In addition to these elements, foundry alloys may contain a small amount of titanium [7440-32-6] Ti, for grain refinement, as weU as small additions of manganese, chromium, or nickel [7440-02-0] Ni. A high strength Al—Cu—Mg alloy for aircraft use contains silver for added strength by modifying the precipitate phase. Alloys intended for pressure die casting may have high iron contents to resist welding to the dies. Lower grades of the same alloys may be used in sand casting and permanent mold castings with some benefits to mechanical properties. Castings are produced in an F temper (as-cast) and a T temper (heat treated) where higher strengths or other special characteristics are desired.  [c.120]

For erosive wear. Rockwell or Brinell hardness is likely to show an inverse relation with carbon and low alloy steels. If they contain over about 0.55 percent carbon, they can be hardened to a high level. However, at the same or even at lower hardness, certain martensitic cast irons (HC 250 and Ni-Hard) can out perform carbon and low alloy steel considerably. For simplification, each of these alloys can be considered a mixture of hard carbide and hardened steel. The usual hardness tests tend to reflect chiefly the steel portion, indicating perhaps from 500 to 650 BHN. Even the Rockwell diamond cone indenter is too large to measure the hardness of the carbides a sharp diamond point with a light load must be used. The Vickers diamond pyramid indenter provides this, giving values around 1,100 for the iron carbide in Ni-Hard and 1,700 for the chromium carbide in HC 250. (These numbers have the same mathematical basis as the more common Brinell hardness numbers.) The microscopically revealed differences in carbide hardness accounts for the superior erosion resistance of these cast irons versus the hardened steels.  [c.270]

Some of the more important properties of diffusion coatings have already been mentioned. Generally speaking, the properties of a diffusion coating are those to be expected from a wrought or cast alloy of the same composition. Thus the corrosion-resisting properties of chromised low-carbon steels are very similar to those of a high-chromium stainless iron", and sherardised materials behave much in the same way as galvanised steel or iron-zinc alloys. This generalisation of course assumes that the coatings are substantially non-porous. For example, the presence of carbon in steel may result in the formation of slightly imperfect chromised layers which are prone to develop pin-point corrosion in strong electrolyte corrodents such as sodium chloride, whereas the use of steels in which carbon is stabilised by a strong carbide-former such as titanium gives coatings of perfect continuity and structure, which provide adequate protection for all types of wet-corrosion conditions. Much of the value of modern techniques lies in the controlled production of homogeneous non-porous coatings.  [c.410]

Because iron—nickel alloys tend to contain large amounts of ferrite stabilizers such as chromium and molybdenum, the minimum nickel content required to maintain a fee matrix is about 25 wt %. High iron contents lower cost, increase fabricabiUty, and tend to raise the melting point, at the expense of poorer oxidation resistance than nickel-base alloys. Chromium is added for surface protection and soHd-solution strengthening of gamma. Molybdenum also is added for soHd-solution strengthening, but is present also in carbides and Small quantities of boron or zirconium are added to improve workabibty and stress—mpture properties, and carbon is usebil as a deoxidant and to provide MC carbides to help refine grain size during hot working. Finally, ductilizing effects may be realized with small addition of magnesium, calcium, and certain rare-earth elements. Iron—nickel alloys are used extensively in aircraft gas turbines and in the space shutde main engine.  [c.124]

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]

Retort Process. Retorts for producing carbon disulfide are typically oval or cylindrical vessels approximately 1 m in diameter by 3 m high, constmcted from chrome alloy steel or cast iron (40,41). Normally one to four retorts are installed in a single furnace, fired with coal, gas, or oil. Alternatively, external electric heaters can be used. The precalcined charcoal is intermittently charged to the top of the retort through a special valve arrangement. Sulfur is added continuously near the bottom of the retort. The sulfur may be first vaporized and superheated to about 700°C in a pipe-coil heat exchanger located in the furnace. Carbon disulfide forms as the sulfur vapor rises through the hot charcoal at 850—900°C. Carbon disulfide, excess sulfur, and other vapors exit from the top of the retort through a duct. Nonreactive ash consoHdates with charcoal dust and sifts down to the bottom of the retort from where the residue is periodically removed. Depending on the quaUty of the raw materials, deposits on the inside walls of the retort must be scraped off approximately monthly. Retorts must be replaced every 1—2 years due primarily to corrosive attack from sulfur vapor. Production capacities are typically up to about 5 tons of carbon disulfide per day per retort with external sulfur vaporization, or 1—3 tons per day with Hquid sulfur feed.  [c.29]

The distribution of chromium consumption in the United States by physical form is shown in Table 8. Growth has been modest since the 1970s, and there have been few changes in the consumption pattern, which for the 1980s was 79.5% in stainless and heat-resisting steel, 8.2% in fuU-alloy steel, 1.7% in carbon steel, 1.6% in high strength low alloy steel, 1.1% in tool steel, 1.7% in cast iron, 2.9% in superaHoys, 0.2% in stmctural and hard-facing welding materials, 0.8% in cutting materials and magnetic, aluminum, copper, nickel, and other alloys, and 2.19% in miscellaneous and unspecified uses (40). A 3—4% annual growth in chromium consumption leading to a total U.S. primary chromium demand of 1,000,000 metric tons in the year 2000 has been projected (20). Chromium is absolutely essential to the production of stainless steel, which accounts for the largest use of this metal. Moreover, a chromium-free stainless steel is unlikely. Thus chromium importance can be judged in view of the importance of stainless steel to the U.S. industrial economy.  [c.120]

Most units are good-grade cast iron for the casing and lohes. Shafts are high-grade carhon, alloy steel, or stainless steel. Conventional packing boxes are usually satisfactory Because operating pressures are not extremely high.  [c.519]

Silicon-iron Silicon-iron anodes are again generally supplied in standard sizes, e.g. 2-0in (approx. 50mm) dia. x 4 ft (1 2 m) long and 3 in (75 mm) X 5 ft (l-5m) long and are complete with a cable tail. These anodes are made from cast iron with a high silicon content of 14-15%, together with small percentages of alloying elements such as chromium. The main disadvantage is their extreme brittleness, resulting in transport problems from the foundry to the cathodic protection site, especially if this is overseas.  [c.209]

Cobalt-Base Superalloys. Cobalt-base superaHoys are used principally where operating metal temperatures range from 650 to 1000°C and stresses are relatively low. Strengthened primarily by carbide precipitation and soHd-solution effects, these alloys are widely used as forgings and castings for nozzle vanes in gas turbine engines, because of good thermal shock and hot corrosion resistance, and in sheet metal assembHes, such as combustion chamber liners, tail pipes, and afterburners. However, rotating parts such as turbine blades and disks, are more likely to be made from nickel-base alloys, because of the latter s superior strength at low and intermediate temperatures. Some of the industrial uses of cobalt-base alloys include grates for heat-treating furnaces, quenching baskets, pouring fuimels for molten copper, skids for slab reheating furnaces, and other foundry and metalworking operations where the prime requisites are resistance to oxidation at elevated temperatures, comparabiHty with slags, and resistance to thermal and mechanical shocks. In addition, the wrought grades are used for high temperature springs and fasteners. Cast alloys where carbon exceeds 1 wt % and chromium contents are in the range 26—32% are used for cutting tools and wear-resistant facings, where high hardness and abrasion resistance at elevated temperatures are the prime requirements (see Tool materials). Cobalt alloys also are used extensively in valves,pumps (qv), nozzles, and mixers for the chemical process industries. These alloys generally also contain significant amounts of tungsten, iron, nickel, and sometimes molybdenum. A prominent example is StelHte 6, which has 30% Cr, 2.5% Ni, 3% Fe, 1.5% Mo, 4% W, 1.4% Mn, and 1% C.  [c.124]

Stainless Steels (Iron-Based Alloys). The great abundance of iron and the numerous corrosion resistant iron-based alloys, such as stainless steels, have limited uses as restorative dental materials. Dental restorative alloys evolved from gold casting alloys, entrenching the gold casting technology as a preferred method of fabrication of prostheses. The strength and performance requirements for cast alloy prostheses led to the use of alloys, other than stainless steels, from the 1930s—1970s as more desirable, functional replacements for more expensive gold alloys. The iron-based casting alloys of that time did not provide the needed corrosion resistance, especially against pitting and crevice corrosion, casting ease, compatibiHty with dental porcelains, high temperature oxidation resistance, and surface appearance as did the cobalt— chromium and nickel—chromium alloys.  [c.486]


See pages that mention the term Cast iron high-chromium cast irons : [c.314]    [c.213]    [c.1053]   
Corrosion, Volume 2 (2000) -- [ c.0 ]