Steel heat content

Example 3.1 Find the rate of heat liberation needed to heat 0.4% carbon steel to 2200 F on a hearth. A loading rate of 80 Ib/ft hr is very good for a single zone batch furnace. From figure 2.2, interpolate the gain in steel heat content from 60 F to 2200 F as 365 Btu/lb, so 80 x 365 = 29 200 Btu/ft hr, which is 8.11 Btu/s for each square foot of hearth. From an available heat chart for natural gas (reference 51), the best possible efficiency for an estimated 2400 F flue gas exit temperature with 10% excess air would be 31.5%, so the rate of heat liberation required = 29 200 Btu/ft hr output divided by (31.5 useful output/100 gross input) = 92 700 gross Btu/ft hr. 

Procedure (boron in steel). Dissolve about 3g of the steel (B content >0.02 per cent), accurately weighed, in 40 mL dilute sulphuric acid in a 150mL Vycor or silica flask fitted with a reflux condenser. Heat until dissolved. Filter through a quantitative filter paper into a 100 mL graduated flask. Wash with hot water, cool to room temperature, and dilute to the mark with water. This flask (A) contains the acid-soluble boron. 

Table 8.7 Chromium, Heat Resistant and High Speed Steels, carbide content in completely solidified samples (vol-%).

Core shakeout is often difficult from aluminum castings. Aluminum is cast at a much lower temperature than iron or steel, 1400°F versus 2500 to 3000°F, and aluminum has a heat content much lower than iron or steel. As a result, the cores or molds are heated to a much lower temperature and the temperatures are not always sufficient to adequately break down the adhesive. 

To illustrate this, calculated carbon profiles are plotted in Figure 5.48 for an 0.85 wt% C steel heated for 90 min at 1050 °C for various assumed values of kc, the corrosion constant.The profiles are plotted relative to the original metal surface and refer to the following values of kc 4.1 x 10 mm s , which is a realistic value for a furnace atmosphere a hypothetical value of 4.1 x 10 mm s to represent a very high scaling rate and 0 mm s representing the case where the atmosphere just fails to form a scale but still reduces the surface carbon content to very low values. 

Although Professor Trinlcs early editions related mostly to metal heating, particularly steel heating, his later editions (and especially this sixth edition) broaden the scope to heating other materials. Though the text may not specifically mention other materials, readers will find much of the content of this edition applicable to a variety of industrial processes. 

Fig. 2.2. Heat contents of irons and steels, showing the small effects of cartxin content on heat contents of pure iron, cast iron, and malleable iron with 4.1% carbon steels from 0.3 to 1.57% carbon. Compare this with fig. 2.5 showing effects on thermal conductivity over a narrower temperature range.

A8. From figure 5.1 at average 2000 F flue gas with 10% excess air, read 40% available heat as an average over the 9-hr period. From figure 2.2, estimate the heat content of the steel at 2300 F as 364 Btu/pound. Therefore,... 

Fig. 8.9. Heat contents of four steels in normal working temperature ranges. For heat contents of other metals, consult pp. 260-263 of reference 52.

In the past century, Ginnings, Douglas, and Ball (1950) used a precision ice calorimeter for determining the enthalpy change of sodium between 0°C and temperatures of up to 900 °C. For this purpose, sodium enclosed in a steel capsule was dropped from a furnace into the calorimeter. The same procedure was used for determining the heat content of the empty capsule. For the difference, that is, the enthalpy of sodium, the authors indicate a probable uncertainty of 0.02% between 100 and 600 °C. 

There is an obvious temperature change during the heat-absorbing and release process of sensible heat-storage materials. Water, steel and stone are widely used sensible heat-storage materials. Water is the cheapest, most useful sensible heat-storage materials in the temperature interval from 1 °C to 99 °C at 1 standard atmosphere. The absorbing heat content of water for a 1 °C rise in temperature is 4.18 J/g. 

Fluorine cannot be prepared directly by chemical methods. It is prepared in the laboratory and on an industrial scale by electrolysis. Two methods are employed (a) using fused potassium hydrogen-fluoride, KHFj, ill a cell heated electrically to 520-570 K or (b) using fused electrolyte, of composition KF HF = 1 2, in a cell at 340-370 K which can be electrically or steam heated. Moissan, who first isolated fluorine in 1886, used a method very similar to (b) and it is this process which is commonly used in the laboratory and on an industrial scale today. There have been many cell designs but the cell is usually made from steel, or a copper-nickel alloy ( Monel metal). Steel or copper cathodes and specially made amorphous carbon anodes (to minimise attack by fluorine) are used. Hydrogen is formed at the cathode and fluorine at the anode, and the hydrogen fluoride content of the fused electrolyte is maintained by passing in... 

Steels iu the AISI 400 series contain a minimum of 11.5% chromium and usually not more than 2.5% of any other aHoyiag element these steels are either hardenable (martensitic) or nonhardenable, depending principally on chromium content. Whereas these steels resist oxidation up to temperatures as high as 1150°C, they are not particularly strong above 700°C. Steels iu the AISI 300 series contain a minimum of 16% chromium and 6% nickel the relative amounts of these elements are balanced to give an austenitic stmcture. These steels caimot be strengthened by heat treatment, but can be strain-hardened by cold work. 

A 95% yield of pure anthraquinone was obtained. This is an almost quantitative yield based on the 100% content of the anthracene used. The cmde anthraquinone was then purified. To a jacketed steel kettie, provided with an agitator, was added cmde anthraquinone and nitrobenzene. Under agitation, the charge was heated at 130—140°C until a complete solution resulted. Under slow agitation, the solution was cooled to 30 °C and the resulting slurry of anthraquinone was filtered on a pressure filter. The cake was washed twice with nitrobenzene, then was reslurried on the filter with nitrobenzene, sucked dry, and transferred to a vacuum dryer where the nitrobenzene was distilled. The dried anthraquinone was discharged to suitable containers. A 99% yield of pure anthraquinone was obtained equal to a recovery of approximately 90% based on the cmde anthraquinone. 

High purity 50% ferrosihcon containing <0.1% Al and C is used for production of stainless steel and corded wire for tires, where residual aluminum can cause harm fill alumina-type inclusions. These are also useflil in continuous cast heats, where control of aluminum is necessary. High purity grades of 50 and 75% ferrosihcon containing low levels of aluminum, calcium, and titanium are used for sihcon additions to grain-oriented electrical steels, where low residual aluminum content contributes to the attainment of desired electrical properties, eg, significant reduction of eddy currents. 

A good summary of the behavior of steels in high temperature steam is available (45). Calculated scale thickness for 10 years of exposure of ferritic steels in 593°C and 13.8 MPa (2000 psi) superheated steam is about 0.64 mm for 5 Cr—0.5 Mo steels, and 1 mm for 2.25 Cr—1 Mo steels. Steam pressure does not seem to have much influence. The steels form duplex layer scales of a uniform thickness. Scales on austenitic steels in the same test also form two layers but were irregular. Generally, the higher the alloy content, the thinner the oxide scale. Excessively thick oxide scale can exfoHate and be prone to under-the-scale concentration of corrodents and corrosion. ExfoHated scale can cause soHd particle erosion of the downstream equipment and clogging. Thick scale on boiler tubes impairs heat transfer and causes an increase in metal temperature. 

The durabihty and versatility of steel are shown by its wide range of mechanical and physical properties. By the proper choice of carbon content and alloying elements, and by suitable heat treatment, steel can be made so soft and ductile that it can be cold-drawn into complex shapes such as automobile bodies. Conversely, steel can be made extremely hard for wear resistance, or tough enough to withstand enormous loads and shock without deforming or breaking. In addition, some steels are made to resist heat and corrosion by the atmosphere and by a wide variety of chemicals. 

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