Steel service temperature

Plain Carbon and Low Alloy Steels. For the purposes herein plain carbon and low alloy steels include those containing up to 10% chromium and 1.5% molybdenum, plus small amounts of other alloying elements. These steels are generally cheaper and easier to fabricate than the more highly alloyed steels, and are the most widely used class of alloys within their serviceable temperature range. Figure 7 shows relaxation strengths of these steels and some nickel-base alloys at elevated temperatures (34). 

The copolymers have been used in the manufacture of extruded pipe, moulded fittings and for other items of chemical plant. They are, however, rarely used in Europe for this purpose because of cost and the low maximum service temperature. Processing conditions are adjusted to give a high amount of crystallinity, for example by the use of moulds at about 90°C. Heated parts of injection cylinders and extruder barrels which come into contact with the molten polymer should be made of special materials which do not cause decomposition of the polymer. Iron, steel and copper must be avoided. The danger of thermal decomposition may be reduced by streamlining the interior of the cylinder or barrel to avoid dead-spots and by careful temperature control. Steam heating is frequently employed. 

At ambient temperatures the strength of molybdenum is comparable to that of normalised low-alloy steel and moderately higher than that of the austentic stainless steels. However, whereas the low-alloy steels are limited to use at service temperatures of about 550°C and stainless steels to about... 

The effect of sulphur from the gas phase is critically dependent on the effectiveness of fuel combustion. With good combustion to the limit of the available oxygen, and even down to 50% air deficiency, no serious effect was found from high-sulphur fuel in tests with 321S12 steel up to the usual limit of service temperature at 850°C, as shown in Table 7.9. With 310S24 steel at 1 100°C some effect from high sulphur content was found in 2 1 air gas with effective combustion, but none in 4 1 and 6 1 mixtures. 

Stainless steel type 304L is an extra-low-carbon stainless steel. Grade 304L can be used for applications involving service temperatures up to 450°C, and under certain conditions up to 800°C. The following data were obtained from Ref. G8 (p.B10). 

Stress relieve carbon and chrome steel welds and cold bends in amine service regardless of service temperature. For all concentrations of carbonate solutions and in concentrations of caustic up to 30 percent stress relieve for service temperatures above 140 F (60 C). For 30 to 50 percent caustic, the service temperature where stress relief is required decreased from 140 >F(60°C) to 118T (4B C). Welded tubing does not require heal treatment in addition to that required by the ASTM specifications. Rolled tube-to-tube sheet joints do not require stress relief. 

As an internal insulation in a process vessel, reducing the surface temperatures on the membrane to an acceptable level. Examples (1) Steel pickling tank in a steel mill, lined with rubber sheet. Top service temperature of the rubber 160°F, but bath temperature 210°F. The brick lining provides sufficient insulation to get the surface temperature of the rubber sheet down to 140°F. (2) The same system to protect the membrane in process vessels or (3) to prevent live steam from cutting out the asphalt membrane on a floor. 

The terms semikilled, rimmed, and capped refer to many carbon steels that have been partially deoxidized or not deoxidized at all. Examples include ASTM A53 and API 5L [10] for pipe and ASTM A36, a structural steel specification. (While these specifications do no require a killing practice, some, such as API 5L, are normally supplied in the killed condition). Although plain carbon steels are often permitted in benign services such as chemically treated utility water or air lines, killed carbon steels are generally used for at least three reasons (1) There is virtually no cost difference between the two steels. The killed carbon steel is usually preferred because of its lower defect density and higher maximum code-allowable stress at higher service temperatures. 

Brittle Failure. Below some limiting temperature steel pipe is notch sensitive and can crack at lower-than-yield-point stress with little or no deformation or absorption of energy. Do not use carbon steel pipe at temperatures even as low as 0°F unless the service is completely non-hazardous or you have specific evidence that a particular lot of pipe is resistant to brittle failure at the service temperature. 

In the present study, the long-term oxidation resistance of some of these FeCrMn(La/Ti) steels in both air and simulated anode gas has been studied and compared with the behaviour of a number of commercially available ferritic steels. Main emphasis was put on the growth and adherence of the oxide scales formed during exposure, their contact resistance at service temperature as well as their interaction with various perovskite type contact materials. 

Ductility is the plastic response to tensile force. Plastic response, or plasticity, is particularly important when a material is to be formed by causing the material to flow during the manufacture of a component. It also becomes important in components that are subject to tension and compression, at every temperature between the lowest service temperature and the highest service temperature. Ductility is essential for steels used in construction of reactor pressure vessels. Ductility is required because the vessel is subjected to pressure and temperature stresses that must be carefully controlled to preclude brittle fracture. Brittle fracture is discussed in more detail in Module 4, Brittle Fracture. 

These assumptions are not always justifiable when applied to plastics unless modification has occurred. The classical equations cannot be used indiscriminately. Each case must be considered on its own merits, with account being taken of such factors as the mode of deformation, the service temperature and environment, the fabrication method, and so on. In particular, it should be noted that the past traditional equations that have been developed for other materials, principally steel, use the relationship that stress equals the modulus times strain, where the modulus is constant. Except for thermoset reinforced plastics and certain engineering plastics, many plastics do not generally have a constant modulus. Different approaches have been used for the nonconstant situation some are quite accurate. The drawback is that most of these methods are quite complex, involving numerical techniques that are not attractive to designers. One method that has been widely accepted is this so-called pseudoelastic design method. In this method appropriate values of such time-dependent properties as the modulus are selected and substituted into the standard equations. 

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