Hot Metal

Hot Metal Hot metal (HM) is the output of a blast furnace (BF). It is liquid iron which is produced by the reduction of descending ore burden (iron ore lump, sinter, and pellet) by the ascending reducing gases. HM gets collected in the hearth of the BF. From the hearth, the HM is tapped from the taphole of the BF after an interval of time. Normally in large BFs, HM tapping rates of 7 ton/min and liquid tapping velocities of 5 m/sec, in tap holes of 70 mm diameter and 3.5 m long, are typically encountered. The tapping rate of HM is strongly influenced by the taphole condition and taphole length. Generally the temperature of tapped HM varies in the range of 1420 deg C to 1480 deg C. The tapped HM is handled in the two stages namely (i) handling of the HM in the cast house i.e. from taphole to the hot metal ladles (open top or torpedo), and (ii) transport of HM ladles to the point of HM consumption. Presently most of the HM is consumed within integrated steel plants for steel making. The HM is transferred to the steel melting shop for making of steel. The HM which is not sent for steel making is cast into pig iron in pig casting machine for use in steel making later as cold charge or is sold to foundries or to mini steel plants having induction furnaces as merchant pig iron. HM can also be granulated by a process which is known as ‘Granshot’ process. Presently the Granshot plants for the production of GPI are working at six places namely (i) Uddeholm, Sweden, (ii) SSAB Lulea, Sweden, (iii) Voest Alpine, Donawitz, (iv) Saldanha steel, South Africa, (v) SSAB Oxelosund, Sweden, and (vi)...

Anthracite Coal

Anthracite Coal Anthracite coal derives its name from the Greek word ‘anthrakít?s’, literally meaning ‘coal-like’.  It is frequently being referred as hard coal and is one of the four types of coals. Other types of coals are lignite coal, sub- bituminous coal and bituminous coal. Since anthracite coal had been subjected to the intense pressure and heat, it is the most compressed and hardest coal available. Being a hard coal, it contains greater potential to produce heat energy than softer, geologically ‘newer’ coal. As per ISO 11760:2005, anthracite coal is defined as the coal, synonymous with high-rank coal, having a mean random vitrinite reflectance, equal to or greater than 2.0 % but less than 6.0 %, or, preferably, a mean maximum reflectance, , less than 8.0 % for geologically unaltered coal. Geology and mining of anthracite coal Anthracite coal was formed from bituminous coal when great pressures had developed in the folded rock. Transformation of the bituminous coal into anthracite is called ‘Anthracitization’. It was formed during the Carboniferous Age, when the dense green vegetation that thrived during the tropical climate of the time fossilized. It is the oldest and cleanest type of coal. It is the rarest and most mature coal. It is a hard, compact variety of coal. It has the highest ranking amongst all the four types of coals. It has undergone the most metamorphosis. It has the highest fixed carbon content and the least impurities. It has the highest energy density amongst all types of coal. The formation of anthracite coal is shown in Fig 1. Fig 1 Formation of anthracite coal Anthracite coal normally occurs in old geological formations which have spent the longest time underground. It is the rarest and most mature coal which accounts for only around 1 % of the world’s total coal reserves. The major reserves of the anthracite coal are...

Austenitic Manganese Steel...

Austenitic Manganese Steel The first austenitic manganese steel was developed in 1882 by Robert Abbott Hadfield. Hadfield had done a series of test with adding ferro-manganese containing 80 % manganese and 7 % carbon to decarbonised iron. Increasing manganese and carbon contents led to increasing brittleness up to 7.5 % manganese. At manganese contents above 10 % however, the steel became remarkably tough. The toughness increased by heating the steel to 1000 deg C followed by water quenching, a treatment that would render carbon steel very brittle. The alloy introduced commercially contained 1.2 % carbon (C) and 12 % manganese (Mn) in a ratio of 1:10. This composition is used even today, and the austenitic manganese steel is still known as Hadfield steel. The steel was unique since it exhibited high toughness, high ductility, high work hardening ability and excellent wear resistance. Because of these properties Hadfield’s austenitic manganese steel (AMS) gained rapid acceptance as a useful engineering material. Austenitic manganese steels have a proven high resistance to abrasive wear including blows and metal-to-metal wear, even though they have a low initial hardness. These steels are supposed to work harden under use and thus give a hard wear resistant surface, but it has been reported that these steels have a good wear resistance in components even without heavy mechanical deformation. Hadfield`s austenitic manganese steel is still used extensively, with minor modifications in composition and heat treatment, primarily in the fields of earthmoving, mining, quarrying, oil well drilling, steelmaking, railroading, dredging, lumbering, and in the manufacture of cement and clay products. Austenitic manganese steel is used in equipment for handling and processing earthen materials (such as rock crushers, grinding mills, dredge buckets, power shovel buckets and teeth, and pumps for handling gravel and rocks). Other...