Steel-carbon type AISI

The materials of construction of the conveyor bed depend on the product to be dried. Products that are destined for human consumption or that are corrosive typically require stainless steel construction. AISI 300 series stainless steels such as 304 or 316 are the most common types of stainless steel however, some AISI 400 series stainless steels such as 409 are also used. Other products are typically dried on carbon steel conveyor beds. As long as condensation on the bedplates is avoided when the dryer is not operated, a carbon steel conveyor bed can give the same service life as a stainless steel conveyor bed on noncorrosive products. 

The only real long term testing of types AISI 302, 315 and 316 stainless steels in chloride contaminated concrete is reported by Cox etal. (1996). Both industrial and marine splash conditions were tested with stainless steels embedded in prisms or beams of concrete with w/c ratio 0.75 (high permeability) and w/c 0.6. In the marine test site chlorides penetrated into the concrete and the chloride concentration after 22 years was found to be 0.5-0.75% C17cement at 30 mm depth (position of the stainless steel rebars). Examination of the steels after 22 years showed no signs of corrosion. At the industrial site beams with chlorides added to the mix (up to 3.2% with respect to cement content) were tested. Carbonation did not reach the steels and no corrosion was observed. 

Germany, the United Kingdom, and the United States shared ahke in the early development of stainless steels. In the United Kingdom in 1912, during the search for steel that would resist fouling in gun barrels, a corrosion-resistant composition containing 12.8% chromium and 0.24% carbon was reported. It was suggested that this composition be used for cutiery. In fact, the composition of AISI Type 420 steel (12—14% chromium, 0.15% carbon) is similar to that of the first corrosion-resistant steel. 

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. 

OD Tube Gauge Factor Carbon Steel Admiralty Red Brass,. 45% Ars. Copper 4-6% Chrome V2 % Moly Steel 80-20 CU-NI 70-30 CU-NI Monel Copper 99.9+ % CU Nickel Aluminum Stainless AISI Type 302 304 Yorkalbro, Aliun. Brass... 

Because of the many types of rolled and forged steel products used in industry, basic specifications are needed to designate the various types. The American Iron and Steel Institute (AISI) has set up a series of standards for steel products. However, even the relatively simple product descriptions provided by AISI and shown in Table 2 must be used carefully. For instance, the AISI 1020 carbon steel does not refer to all 0.20 percent carbon steels. AISI 1020 is part of the numerical designation system defining the chemical composition of certain standard steels used primarily in bar, wire, and some tubular steel products. The system almost never applies to sheets, strip, plates, or structural material. One reason is that the chemical composition ranges of standard steels are unnecessarily restrictive for many applications. 

Carbon steel 5Cr-1 Mo AISI Type 304 AISIType 310 AISI Type 410 AISI Type 430 AISI Type 446 Incoloy 50Cr/50Ni... 

Martensitic chromium steels (AISI 400 series) contain no (or very little) nickel, and the chromium content is typically about 12%. These steels can undergo the a-Fe/7-Fe transition at about 1050 °C and so can be heat-treated for improved mechanical properties, much as can ordinary carbon steels. Since they have the a-Fe structure at ambient temperatures, they are ferromagnetic in ordinary service. Examples are type 410 (11.5-13.5% Cr), which is used for turbine blades, and type 416 (12-14% Cr with minor amounts of Se, Mo or Zr), which has good machinability. 

The low depth of the IGC in AISI 316L steel can be explained by the low carbon content, resulting in the formation of a discrete carbide chain along the grain boundaries. In the AISI 321 and 316Ti types of steel with... 

The simplest stainless steel contains only iron and chromium. Chromium stabilizes the ferrite phase. Ferrite has a body centered cubic structure, it is magnetic, high in yield strength and low in ductility. Ferrite shows a very low solubility for carbon and nitrogen. The ferritic steel, AISI Type 446, is used for high-temperature applications and Types 430 and 434 for corrosion applications, such as automotive trim. 

The fuel pin and fluid are sealed into the tube by means of end plugs silver soldered into place. The tube is rnade of AISI Type 347 stainless steel of 0.188 in. OD and 0.008 in. wall thickness. The helical rib outside the fuel tube is made of low-carbon steel for these tests, although stainless steel or other material will ultimately be used. The rib (cross section 0.065 in. by 0.025 in.), is made of flattened wire. The stock is edge wound on a 1-in. diameter arbor, set, and finally pulled out lengthwise to form a helix of the proper diameter and a 4-inch right hand pitch. The helix is slipped over the fuel tube and soldered into place. One hundred and sixty-nine fuel tubes are required for each subassembly. 

Solution Option 1, Carbon Steel Heat Exchanger Option 2, AISI Type 316 Heat Exchanger... 

Samples of type 301 stainless steel were obtained which had been cold-worked 42, 62, and 78. The chemical analyses of these steels are given in Table I. The chemistry was normal for AISI type 301, except that carbon was held to a maximum of 0.10 to minimize carbide precipitation during welding. Standard sheet specimens were prepared for tensile tests, while notched sheet specimens were used to determine notch tensile strength. A notch-acuity factor of about 6.3 was... 

Solution rale tests. The solution rates of Fc into Bi, and Bi- - Zr and Mg, were measured in crucibles of a carbon steel, a 2 % Cr-1% Mo, a 5% Cr-1 Mo, and an AISI typc-410 steel. The crucible, Bi, and additives were equilibrated at 400 to 425°C, the temperature rapidly rahsed to 600°C, and the coiiceiitration of Fo in solution measured as a function of time. Results are shown in Fig. 21-2. In the presence of Zr-fMg, the 5% Cr-1 2 c I Io and the AISI type-410 steels dissolved at approximately th( same rate, while the 2 % Cr-1% Mo steel dissolved more slowly. No detectable dissolution of Fe from the carbon steel was measured in 44 hr at blO°C. These results are parallel to the thermal convection loop results, and consi,stent with the film-formation studies in that the measured solution rates are inversely proportional to the ability and rate at w hich the steels form ZrX films. At present no data are available on rates of solution for ZrC-forming steels. 

Brookhaveri National Laboratory has used both types of valves exten-,si ely [22,34]. The 1/2-in. IPS 150-lb Y pattern globe valves constructed from AISI type-347. staudess steel for all parts in contact with bismuth (including bellows, stem, and disk) have, been used continuously for over 8000 hr at 930°I without mishap. Similar valves with mild carbon steel disks (instead of type-347 stainless steel) have been used at 930°F for over 13,000 hr without failure or extensive corrosion. 

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