Quenched and Tempered Reinforcement bars Feb24

Quenched and Tempered Reinforcement bars...

        Quenched and Tempered Reinforcement bars  The Tempcore process for the manufacture of reinforcement bars has been developed in the seventies by Centre de Rechaerche Metallurgiques (CRM) Belgium in order to manufacture high yield strength weldable concrete reinforcement bars from mild steel billets. It is one of the most effective processes for the production of popularly known TMT (Thermo Mechanically Treated) reinforcement bars. Thermex from HSE Germany is the other process for the manufacture of Reinforcement bars.  Principle Both the processes are similar in nature and are based on heat treatment principle. These processes impart high strength to the bars using the technique of Thermo Mechanical Treatment as against Cold Twisting which is used for the manufacture of Torsteel reinforcement bars. Due to the heat treatment the micro structure of the bar consists of Tempered Martensite in the periphery and Ferrite Pearlite in the centre (Fig !). The strength to the bar is by Tempered Martensite layer while the ductility to the bar is incorporated by the Ferrite- Pearlite layer.   Fig. 1 Microstructure of Reinforcement Bars  The schematic diagram of the process on a Time-Temperature curve is given on Fig. 2.   Fig 2 Schematic Diagram on a Time – Temperature Curve  Process Heated steel billets are rolled in the rolling mill to the final size and shape of the reinforcement bar. At this stage the bar is processed by this process. The process is carried out in three successive stages as described below. The first stage begins as soon as the bar leaves the final mill stand. The bar is rapidly and energetically cooled (Quenched) with water through a short cooling installation, where it undergoes surface hardening (Martensite layer). At this stage the surface layer is converted into Martensite while the core remains Austenitic. The...

Iron ore pellets and Pelletizing processes Feb23

Iron ore pellets and Pelletizing processes...

               Iron ore pellets and Pelletizing processes Pelletizing is a process that involves mixing very finely ground particles of iron ore fines of size less than 200 mesh with additives like bentonite and then shaping them into oval/spherical lumps of 8-16 mm in diameter by a pelletizer and hardening the balls by firing with a fuel. It is the process of converting iron ore fines into “Uniformed Sized Iron Ore Pellets” that can be charged directly into a blast furnace or into a furnace used in the production of Direct Reduced Iron (DRI). The pellets are shown in Fig 1 Fig 1 Iron ore pellets The typical properties of the pellets is given in Table 1 Table 1 Properties of Pellets Chemical analysis(On dry basis) Unit Value Tolerance Fe % 65 Minimum FeO % 0.3 Maximum SiO2 + Al2O3 % 5 Maximum CaO % 0.03 ± 0.01 MgO % 0.06 ± 0.01 Basicity % 65 Maximum Phosphorus % 0.05 Maximum Physical properties       Bulk Density t/Cum 2.2 ± 0.2 Tumbler Index % 93 Minimum Abrasion Index % 3 Min ± 0.5 % Cold Crushing Strength (Avg) Kg/P 250 Minimum Size analysis   8 – 16 mm 94 Minimum -5 mm % 2 Maximum +16 mm % 4 Maximum Metallurgical properties   Porosity % 18 Minimum Reducibility % 62 Minimum\ Process technology There are four stages involved in the production of pellets. They are: Raw material preparation. Formation of green balls or pellets Induration of the pellets Cooling, storage and transport of pellets During the process for pelletization iron ore concentrate from iron ore beneficiation plant is dried and heated to about 120 deg C. The dried material is fed to the ball mill for grinding. Concentrate / ground iron ore of typical size...

Finex Process for Liquid Iron Production Feb20

Finex Process for Liquid Iron Production...

             Finex Process for Liquid Iron Production  For the production of liquid iron Finex process was developed jointly by Siemens VAI and the South Korean company POSCO. This process has been based on the direct use of iron ore fines and non coking coal.  Siemens VAI and POSCO are jointly developing this process since 1992. Initial Work The basic laboratory scale research had been done with a 15 tons/day bench scale unit from 1992 to 1996. The results of this unit were used for the test operations of a 150 tons/day pilot plant in 1999. The Finex demonstration plant of 0.6 million tons per annum was built in Pohang works of POSCO and started production in June 2003. This plant has three fluidized bed reactors. Since February 2004, the demonstrated plant steadily produced at a rate of more than 0.7 million tons per annum of hot metal. Commercial Operation Construction of the first commercial plant of capacity 1.5 Mpta started in August 2004 and was commissioned in May 2007. Within the first year of its commissioning the plant reached its stable operation and the stabilized parameters given in Table 1have been achieved. The process is based on direct reduction of iron ore in fluidized beds and then melting of this reduced iron. The commercial plant has used 4 nos. fluidized bed reactors for pre heating and pre-reduction of iron ore and a melter gasifier which is similar to melter gasifier used in the Corex process. Table 1:- Parameter Achieved in Commercial Plant Sl.No. Parameter Unit Value 1 Production rate Mtpa 1.5 2 Availability % 96.8 3 Coal rate Kg/tHM 710 4 PCI rate Kg/tHM 160 5 C in Hot Metal % 4.5 6 S in Hot Metal % 0.03 7 Si in Hot Metal...

Energy Optimizing Furnace Feb19

Energy Optimizing Furnace...

Energy Optimizing Furnace Energy optimizing furnace (EOF) is a primary steel making furnace. This process was developed by the mini steelworks pioneer Willy Korf along with his colleagues. This process is presently being operated in India at JSW SISCOL plant and at Hospet Steel plant of Mukand. The first unit went into production in1982. Process EOF is a melting/refining furnace for the production of liquid steel. It is having a scrap preheater.  The basic principle consists of working with combined submerged and atmosphere oxygen blown in an initial charge containing hot metal, preheated solid scrap and fluxes for slag formation. Scrap is preheated to around 850 deg C by the sensible heat in the off gas in one or two chambers located above the furnace roof. Blown submerged oxygen reacts with the carbon from hot metal and generates CO bubbles that travel through the liquid bath to the furnace atmosphere. Here CO is burnt to CO2 by the oxygen blown through atmospheric injectors and supersonic lances. The bubbling of CO generates a very strong stirring and increases greatly the bath surface. This allows transfer of a good amount of heat to the bath. The process also constitutes deslagging and formation of the secondary slag. The process has possibility of using high percentage of solid charge (even greater than 40 %). The process owes its thermal efficiency due to the following factors: i)             Chemical energy released due to the exothermic reactions between the injected oxygen and the various elements in the bath including added carbon. ii)           Chemical energy released from the gaseous oxidation reactions in the furnace atmosphere involving CO and H2 released from the bath. iii)          Sensible heat transferred by the hot gases from the furnace to the cold scrap charged into the pre...

ITmk 3 Process of making Iron Nuggets Feb17

ITmk 3 Process of making Iron Nuggets...

ITmk 3 Process of making Iron Nuggets  ITmk3 process is also known as Iron making Technologies mark 3 and is based on coal reduction technologies. IT mark 1 is the iron making process by blast furnace while the IT mark 2 is the iron making by direct reduction mostly by gas based reduction processes (Fig 1).       Fig 1 – Iron making Technologies  Development history  The laboratory testing of the process was carried out during 1996 to 1998. During the period 1999 to 2000 a small pilot plant of capacity 3,000 tons per year was constructed and operated at Kakogawa Works of Kobe Steel, Japan. In the years 2002 to 2004 a pilot demonstration plant of 25,000 tons per year was constructed and operated at Minnesota, USA. The construction of first commercial plant of capacity 500,000 tons per year started at Hoyt Lakes Minnesota in 2007 and the operation in this plant started in January 2010.   The Process This process has been developed by Kobe Steel and is environmental friendly. In this process, self reducing–fluxing dried green balls are reduced, carburized and smelted. The self reducing fluxing dried green balls are produced by agglomeration of iron ore fines, limestone as flux, bentonite as binder and boiler coal a reducing – carburizing agent. The process on Iron Carbon phase diagram is shown in Fig 2. Fig 2 – ITmk 3 process on Iron- Carbon phase Diagram           ITmk3 process produces high purity granular iron (Iron nuggets by using iron ore fines and non coking coal. The process is distinctive with reduction, carburizing melting and slag separation (Fig 3). The process occurs at lower temperatures (Around 1350 Deg C) and hence different from conventional iron making by blast furnace....