Residual elements

DRI retains the chemical purity of the iron ore from which it is produced, therefore it tends to be very low in residual elements such as copper, chrome, tin, nickel, and molybdenum. Typical ranges of DRI chemical compositions are shown in Table 2. 

The demand for DRI varies depending on local market conditions. In industrialized countries, DRI primarily is used as a supplement to scrap for controlling residual elements in electric arc furnace steelmaking. In regions where scrap is scarce, DRI is used as a replacement in production of all grades of steel. In 1993, Latin America produced 9.4 X 10 t (39.3%) of the world s DRI. Middle East/North Africa produced 6.1 X 10 t (25.6%), Asia/Oceania produced 4.4 X 10 t (18.4%), and CIS/Eastem Europe produced 1.7 x 10 t (7.1%). North America produced 1.2 x 10 t (5.0%) Africa, 0.9 x 10 t (3.8%) and Western Europe, 0.2 x 10 t (0.8%) (1). Nearly 79% of the DRI produced is consumed in steel mills adjacent to the DR plants called captive plants. Plants which are designed to sell and ship DRI on the open market are called merchant plants. 

HBI has been successfully melted in cupolas (hot or cold blast), induction furnaces (coreless or channel), and electric arc furnaces. It can be a valuable charge material for ductile and malleable irons as well as steel. It is of particular value in making ductile iron castings because of its very low residual element content. 

Low Phosphorus Pla.te a.nd Punchings. This scrap, a prompt iadustrial scrap consisting of punchings or stampiags, plate scrap, and bar croppiags, has uniform known chemical analysis, is clean, and has high furnace recovery (5aeld) when melted. Maximum allowable phosphoms and sulfur contents are 0.05% each. Other unwanted residual elements are also uniformly low. Size limitations are specified. 

Residual Elements. In addition to carbon, manganese, phosphoms, sulfur, and silicon which are always present, carbon steels may contain small amounts of hydrogen, oxygen, or nitrogen, introduced during the steelmaking process nickel, copper, molybdenum, chromium, and tin, which may be present in the scrap and aluminum, titanium, vanadium, or zirconium, which may have been introduced during deoxidation. 

The remainder is copper and residual elements. Values are nominal unless range is shown. To convert from GPa to psi, multiply by 1.45 X 10. ... 

The remainder is nickel and residual elements. Nominal unless range is shown. ... 

Analysis by atomic absorption showed other residual elements present in minute amounts in the extract Ti02, 7.0 ppb ASO2O3, 1.0 ppb PbO, 0.3 ppb and both C03O4 and CdO less than 0.1 ppb. 

MITIGATION - the amelioration of the residual elements of the potential problem. 

Traditional alloy design emphasizes surface and structural stability, but not the electrical conductivity of the scale formed during oxidation. In SOFC interconnect applications, the oxidation scale is part of the electrical circuit, so its conductivity is important. Thus, alloying practices used in the past may not be fully compatible with high-scale electrical conductivity. For example, Si, often a residual element in alloy substrates, leads to formation of a silica sublayer between scale and metal substrate. Immiscible with chromia and electrically insulating [112], the silica sublayer would increase electrical resistance, in particular if the subscale is continuous. 

Carbon residue, in diesel fuel, 22 424 Carbon selenides, 22 87 Carbon sources, for fermentation, 22 25 Carbon steels, 23 291-297 cold working, 23 295-296 heat treatment of, 23 296 hot working, 23 294-295 microstructure and grain size of, 23 293-294 properties of, 23 292—293 residual elements in, 23 296-297 wrought, 23 296... 

In all carbon steels, small quantities of certain residual elements unavoidably retained from raw materials are sometimes found but are not specified or required, such as copper, nickel, molybdenum, and chromium. These elements are considered as incidental and are not normally determined or reported. 

Dulski. T.R. Residual-Element Analysis Measuring the Minuscule. Advanced Materi/ds Processes, 20 (February 1992). 

Burned K and S at major level Cartridge case and primer cup Cu with a trace of Zn Discharge primer residue (elements listed in descending order) ... 

In practice, however, it seems that much of the Hg contained within soils and weathered rock is more or less firmly associated with solid phases. This can be shown to extend from simple sorption to structural incorporation within oxidate minerals. The manner of the association between Hg and organic matter has been discussed by Jonasson (1970). The question of adsorption is a rather grey area and, whilst it is clear that it plays a very significant role in soil experiments (e.g., Andersson, 1979), it seems that in mature soils the Hg is held rather more firmly. (This is apart from discrete mineral hosts deriving from sulphide oxidation.) It is possible that, as a simple adsorbent ages, the associated Hg may enter the structure, becoming a "residual" element effectively removed from the dynamic weathering cycle. 

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