Steels, vanadium content

Carbon content is usually about 0.15% but may be higher in bolting steels and hot-work die steels. Molybdenum content is usually between 0.5 and 1.5% it increases creep—mpture strength and prevents temper embrittlement at the higher chromium contents. In the modified steels, siUcon is added to improve oxidation resistance, titanium and vanadium to stabilize the carbides to higher temperatures, and nickel to reduce notch sensitivity. Most of the chromium—molybdenum steels are used in the aimealed or in the normalized and tempered condition some of the modified grades have better properties in the quench and tempered condition. 

Ferrovanadium. The steel industry accounts for the majority of the world s consumption of vanadium as an additive to steel. It is added in the steelmaking process as a ferrovanadium alloy [12604-58-9] which is produced commercially by the reduction of vanadium ore, slag, or technical-grade oxide with carbon, ferrosiHcon, or aluminum. The product grades, which may contain 35—80 wt % vanadium, are classified according to their vanadium content. The consumer use and grade desired dictate the choice of reductant. 

Environmental studies [17] of urban airsheds in several areas of the country have shown that high levels of atmospheric vanadium oxide are associated with industrialized areas, especially those areas where fossil fuels are burned or where vanadate steel is being produced. In addition, vanadium has been shown to exhibit increased tissue levels in fish and other marine animals associated with oil rigs in the Santa Barbara basin of the United States [18]. Blotcky et al. [19] determined the vanadium content in shrimp, crab, and oyster from four ocean sites off and near Galveston Island, Texas. They found that the vanadium content was greater in marine biological samples taken in waters near industrialized areas as compared to samples taken in waters near the nonindustrialized sections. Speciation of the vanadium is very important since the two oxidation states, i.e., IV or V, have different nutritional and toxic properties [14]. Orvini et al. [20] applied a preirradiation speciation method to freshwaters from the Italian Ticino and Po rivers and found out that vanadium was present in various tetravalent cationic and pentavalent anionic as well as in natural complexed forms. 

Another frequent problem involves the comparison of two (or more) sets of results. Suppose that an analyst measures the vanadium content of a steel sample by two separate methods. With the first method the average value obtained is 1.04%, with an estimated error of 0.07%, and with the second method, the average value is... 

Vanadium pentoxide is the raw material for production of vanadium metal, and ferrovanadium is an alloy that is added to a steel melt to give the steel a specified vanadium content. In addition ash, ore, and slag containing 1900 tonnes of vanadium were imported to the USA in 2000. 

Pig iron (raw iron) is manufactured in a blast furnace. The vanadium content stays in the raw iron. During subsequent steel manufacture, oxygen is blown over or through the melt to oxidize and remove the carbon. At the same time vanadium is oxidized and the oxide goes to the slag. This slag can be used as raw material for the soda roasting process to extract vanadium. 

Contaminants of this type include various combinations of vanadium, sulfur, and sodium compounds. Fuel ash corrosion is most hkely to occur when residual fuel oil (Bunker C fuel) is burned. In particular, vanadium pentoxide vapor (VjOj) reacts with sodium sulfate (Na2S04> to form sodium vanadate (NajO.bVjOj). The latter compound reacts with steel, forming a molten slag that runs off and exposes fresh metal to attack. Corrosion increases sharply with increasing temperature and the vanadium content of the fuel oil. If the vanadium content exceeds 150 ppm, the maximum tube wall temperature should be limited to 650 °C. Between 20 and 150 ppm V, the maximum tube wall temperature can be between 650 and 845 °C, depending on the sulfur content and the sodium-vanadium ratio of the fuel oil. With 5 to 20 ppm V, the maximum tube wall temperature can exceed 845 °C. 

Ferrophos consists primarily of 50—60 wt % iron and 18—28 wt % phosphoms in proportions representing Fe2P plus smaller amounts of either FeP or Fe P. However, varying amounts of chromium (4—5 wt %) and vanadium (5—6 wt %) present in the ore are also included in the ferrophos, and are recovered in some cases. From 0—2 wt % of sdicon may also be present. Ferrophos is also sold for use in specialty steels that can accommodate the phosphoms content in thek formulation (see Steel). 

Ferrophosphoms is produced as a by-product in the electrothermal manufacture of elemental phosphoms, in which iron is present as an impurity in the phosphate rock raw material. The commercial product contains ca 23—29% P and is composed primarily of Fe2P [1310-43-6] and Fe P [12023-53-9] along with impurities such as Cr and V. Ferrophosphoms is used in metallurgical processes for the addition of phosphoms content. Low concentrations (up to - 0.1%) of phosphoms in wrought and cast iron and steel not only increases the strength, hardness, and wear resistance but also improves the flow properties. In large stmctural members and plates, it is desirable to use a type of steel that does not need to be quenched or tempered, and thus does not exhibit weld-hardening. This property is afforded by the incorporation of a small quantity of phosphoms in steel. Ferrophosphoms from western U.S. phosphoms production is used as a raw material for the recovery of vanadium (see Vanadiumand vanadiumalloys). 

Low-carbon, low-alloy steels are in widespread use for fabrication-welded and forged-pressure vessels. The carbon content of these steels is usually below 0.2%, and the alloying elements that do not exceed 12% are nickel, chromium, molybdenum, vanadium, boron and copper. The principal applications of these steels are given in Table 3.8. 

What is the % content of each isotope of vanadium in the unknown steel if the ratio of the areas of the two peaks is the same as that of the masses of the two isotopes ... 

Detection.—Apart from naturally occurring ores of vanadium, vanadium steels, and ferrovanadium, the commonest compounds of vanadium are those which contain the element in the pentavalent state, viz. the pentoxide and the various vanadates. The analytical reactions usually employed are, therefore, those which apply to vanadates. Most vanadium ores can be prepared for the application of these reactions by digesting with mineral acids or by alkaline fusion with the addition of an oxidising agent. When the silica content is high, preliminary treatment with hydrofluoric acid is recommended. Vanadium steels and bronzes, and ferrovanadium, are decomposed by the methods used for other steels the drillings are, for instance, dissolved in sulphuric acid and any insoluble carbides then taken up in nitric acid, or they are filtered off and submitted to an alkaline fusion. Compounds of lower valency are readily converted into vanadates by oxidation with bromine water, sodium peroxide, or potassium permanganate. 

Niobium in Tool Steels. In the matrix method of tool-steel development, the composition of the heat-treated matrix determines the steel s initial composition. Carbide volume-fraction requirements then are calculated, based upon historical data, and the carbon content is adjusted accordingly. This approach has been used to design new steels in which niobium is substituted for all or part of the vanadium present as carbides in the heat-treated material. Niobium provides dispersion hardening and grain refinement, and forms carbides that are as hard as vanadium, tungsten, and molybdenum carbides. 

The best results were obtained with compound 21 that exhibited high vapor pressure and low decomposition temperature (<523 K). Various CVD conditions were applied and gave in all cases shiny, dark-brown deposits.43 XRD and XPS analyses of the deposits indicated the presence of a vanadium carbonitride phase with little contamination from oxygen and free carbon. The films were less adherent on steel substrates than on silicon ones. The steel substrates seemed to suffer corrosion due to the presence of Cl-containing species. We had noticed the same feature in the case of Cl-containing precursors to vanadium carbide. Therefore, in order to increase the volatility of compound 23 and to reduce the Cl content of the molecule, we prepared compounds 24 and 25. Unfortunately, the yields obtained in their syntheses were much too low to permit TG and CVD experiments. 

Metal powder-coated, through-hardened materials - these materials have been found useful when an alloy does not provide adequate forged quality and for cast materials with specific casting problems. Very fine and very even carbide distribution throughout the entire component offers economically viable (in production terms) and effective wear resistance (temperable matrix with high carbide content). Preferred materials include vanadium-alloyed tool steels. 

High speed steels are highly alloyed tool steels which exhibit enhanced hardness and wear resistance at high temperatures. These steels have a high carbon content and varying amounts of chromium, molybdenum, tungsten and vanadium. 

---