300 series stainless steels

Aniline is slightly corrosive to some metals. It attacks copper, brass, and other copper alloys, and use of these metals should be avoided in equipment that is used to handle aniline. For appHcations in which color retention is critical, the use of 400-series stainless steels is recommended. 

The body-centered-cuhic (bcc) metals and alloys are normally classified as undesirable for low temperature construction. This class includes Fe, the martensitic steels (low carbon and the 400-series stainless steels). Mo, and Nb. If not brittle at room temperature, these materials exhibit a ductile-to-brittle transition at low temperatures. Cold working of some steels, in particular, can induce the austenite-to-martensite transition. 

Several constraints were faced in the design phase of the project. For example, special attention was given to the fact that 400 Series stainless steel, carbon, and some grades of aluminum were not compatible with the process. Additionally, the expander discharge temperature was required to stay between 35-70°F. The operating rpm of the expander wheel was determined by the rpm required by the third stage of the air compressor. 

Axial compressor blades are usually forged and milled. Precision casting has been used on occasion. The most common material used is a 12 chrome steel, in the AISI 400 series, and is also known as 400 series stainless steel. While the stator blades are occasionally shrouded, the rotor blades are free-standing. Lashing wires have been used on rotor blades, but are generally used to solve a blade vibrational stress problem. 

The H2SO4-CUSO4 test, unlike the Huey test, is specific for susceptibility due to chromium depletion and is unaffected by the presence of submicro-scopic a-phase in stainless steels containing molybdenum or carbide stabilisers. It can be used, therefore, with confidence to test susceptibility in austenic (300 series) and ferritic (400 series) stainless steels and in duplex austeno-ferritic stainless steels such as Types 329 and 326. 

This process uses a moving laser beam, directed by a computer, to prepare the model. The model is made up of layers having thicknesses about 0.005-0.020 in. (0.012-0.50 mm) that are polymerized into a solid product. Advanced techniques also provides fast manufacturing of precision molds (152). An example is the MIT three-dimensional printing (3DP) in which a 3-D metal mold (die, etc.) is created layer by layer using powdered metal (300- or 400-series stainless steel, tool steel, bronze, nickel alloys, titanium, etc.). Each layer is inkjet-printed with a plastic binder. The print head generates and deposits micron-sized droplets of a proprietary water-based plastic that binds the powder together. 

The more corrosion resistant 300 and 400 series stainless steels are normally pickled in nitric acid, or HF-accelerated nitric acid mixtures. Solutions are operated at temperatures ranging from 70° to 90°C, and contact times of 2 to 20 minutes are typical (3). 

Most instruments are composed of a wide variety of materials. Metallic components are fabricated of beryllium alloys, copper alloys, 300 and 400 Series stainless steels, steel alloys, aluminum alloys. 

Chromium is a refractory metal having a melting point of 3375°F (1857°C). Neither chromium metal nor chromium-based alloys are widely in the hydrocarbon or chemical industries. Chromium plating is useful for aesthetic purposes, and hard chromium plating finds some use in hardface applications. It is extensively used as an alloy addition to low-alloy steels (usually for the purpose of stabilizing carbides) and in cast irons (to produce wear-resistant products) and nickel alloys (for increased corrosion resistance). Chromium is the main alloying addition in the 400-series stainless steels and is used extensively in the 200- and 300-series stainless steels. 

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. 

Magnetic. These are the 400 series stainless steels. They contain between 11% to 18% chromium, but no nickel. Types 410 (12% chrome) and Type 430 (17% chrome) are most commonly used. 

All structural metals corrode to some extent in natural environments (e.g., the atmosphere, soil, or waters). Bronze, brass, most stainless steels, zinc, and pure aluminum corrode so slowly in service conditions that long service life is expected without protective coatings. Corrosion of structural grades of cast iron and steel, the 400 series stainless steels, and some aluminum alloys, however, proceeds rapidly unless the metal is protected against corrosion. As described in Chapter 1, corrosion of metals is of particular concern because annual losses in the United States attributed to corrosion amount to hundreds of billions of dollars. 

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