Carbon in steel

As a final example, the determination of carbon in steels and other metal alloys can be determined by heating the sample. The carbon is converted to CO2, which is collected in an appropriate absorbent trap, providing a direct measure of the amount of C in the original sample. 

Hydrogen at elevated temperatures can also attack the carbon in steel, forming methane bubbles that can link to form cracks. Alloying materials such as molybdenum and chromium combine with the carbon in steel to prevent decarburization by hydrogen (132). 

Iron, in the form of fine filings, will burn and ean be used to produee attraetive gold sparks, such as in the traditional wire sparkler. The small percentage (less than 1%) of carbon in steel ean eause an attraetive branching of the sparks due to earbon dioxide gas formation as the metal particles bum in air. 

Apparatus. For the colorimetric comparison use may be made of the ordinary arrangements for colorimetric determinations, although these are not indispensable. It is well to carry out the colour reactions in exactly similar tubes fitted with ground stoppers and having a capacity of 20-25 c.c. and a diameter of about 15 cm. (see Colorimetric Determination of Carbon in Steel, Vol. I, p. 170). 

The percentage of carbon in steel ranges from just above 0% to 2%. 

Pierce, T. B., P. F. Peck, and W. M. Henry Determination of Carbon in Steels by Measurement of the Prompt Gamma-Radiation Emitted During Proton Bombardment. Nature 204, 571 (1964). 

Formation of graphite (free carbon) in steel by the decay of iron carbide. (2,ASTM, Philadelphia, PA. 

The surface of a mild steel component is commonly hardened by packing the component in a carbonaceous material in a furnace at a high temperature for a predetermined time. Consider such a component with a uniform initial carbon concentration of 0.15 percent by mass, The component is now packed in a carbonaceous material and is placed in a high-temperature furnace. The diffusion coefficient of carbon in steel at the furnace temperature is given to be 4.8 X 10" m /s, and the equilibrium concentration of carbon in the iron at the interface is determined from equilibrium data to be 1.2 percent by mass. Determine how long the component should be kept in the furnace for the I mass concentration of carbon 0.5 mm below the surface to reach 1 percent i (Fig. 14-28). p... 

Discussion The steel component in this case must be held in the furnace for 1 h and 15 min to achieve the desired level of hardening. The diffusion coefficient of carbon in steel increases exponentially with temperature, and thus this process is commonly done at high temperatures to keep the diffusion time at a reasonable level. 

A steel part whose initial carbon content is 0.12 pet cent by mass is to be case-hardened in a furnace at 1150 K by exposing it to a carburizing gas. The diffusion coefficient of carbon in steel is strongly temperature dependent, and at the... 

Repeat Prob. 14—71 for a furnace temperature of 500 K at which the diffusion coefficient of carbon in steel is D,g = 2.IXlO mVs. 

Fifteen minutes were allowed for the fluorine activity to decay before plotting the decay curve of and Si . The curve was resolved and it was found that 100 cpm of N corresponded to 0.31 fig of carbon. Activity due to Si was used as a measure of beam strength in this experiment. Albert et al. (J), in a determination of carbon in steel by this method, separated the nitrogen formed by Kjeldahl distillation and liquid-counted the nitrogen in the distillate. They state that the sensitivity is improved by this method. 

On heating, constituents of the crystal within the strained zone of a line dislocation can be displaced relatively readily and the dislocations can thus migrate to surfaces where they are eliminated, or those with opposing Burgers vectors may cancel each other. Such reduction in dislocation concentration is termed annealing. Cold working (distortion or strain imposition) of a crystal increases its dislocation density. Impurities may retard the movement of dislocations through the crystal (e.g. carbon in steel). 

Use Quantitative absorption of carbon dioxide in the determination of carbon in steel and organic compounds by direct combustion and other analysis. 

They half knew many things, but no single question in any part of the paper was really well done, and no point was thoroughly understood. Many of them seemed to suspect subtle and hidden difficulties in the questions themselves, clear and simple answers to simple and specific questions were the exception. Even the better candidates were lacking in a sense of proportion, as when they required an electric furnace in order to show the presence of phosphorous in bones and a blast furnace for demonstrating that there is carbon in steel. 

In more practical terms, eqn. (14.9b) or (14.8) gives an upper limit to the composition fluctuation that a stress fluctuation can produce. To go to a more extreme case of contrast in mobility, consider carbon in steel l/N is effectively zero and the limit we seek is given by simply balancing a stress gradient against a composition gradient. Going back to eqn. (14.7a), we need... 

If the two components are highly contrasted in both concentration and mobility, as with carbon in steel, N is dominated by the less mobile component and X is dominated by the more mobile. As in the short-wave extreme case already discussed, the N term becomes insignificant in comparison with the diffusive terms. 

The properties of steel depend not only on its chemical composition but also on the heat treatment. At high temperatures, iron and carbon in steel combine to form iron carbide, FesC, called cementite ... 

Light element analysis by XRF is applied in very different scientific and industrial fields. Boron analysis with modern x-ray spectrometers is very important in the semiconductor, ceramic and glass industries or in geosciences. Determination of beryllium in bronze could be an interesting application for XRF analysis in the future. Modern wavelength-dispersive x-ray spectrometers achieve the analytical capability to analyze beryllium in bronze with a limit of detection (= LLD) lower than 0.1%, boron in glass with a LLD of 0.04% and carbon in steel or cement below 100 ppm. 

Figure 8.2. Effect of carbon in steels cold-rolled 50%, or subsequently annealed, on corrosion in deaerated 0.1A/ HCI, 25°C [1], (Reproduced with permission. Copyright 1964, The Electrochemical Society.)...

A limitation for XRF in a metallurgical application is the measurement of carbon in steel. The problem with carbon in this application is due to the small analyzed layer and the inhomogeneous distribution of carbon in steel. To ID the correct steel grade for low carbon steels, OES or combustion analysis is required. 

---