bof

Slide 1: 

BERKAY ORS SADIK CESTEPE CAGDAS METIN GOKTURK BASIC OXYGEN FURNACE

INTRODUCTION : 

INTRODUCTION BOF is a steelmaking method in which pure oxygen is blown into a bath of molten blast-furnace iron and scrap The oxygen initiates a series of intensively exothermic (heat-releasing) reactions, including the oxidation of such impurities as carbon, silicon, phosphorus, and manganese

HISTORY of the BOF : 

HISTORY of the BOF Development of the BOF was initiated in Switzerland by Robert Durrer (fig 1) in the late 1940s. After experimenting with a 2.5-ton pilot unit, Durrer worked with engineers at the Voest Company at Linz, Austria, who set up a commercially operating 35-ton converter in 1952 A second unit began operation within a year at Donawitz, also in Austria. Consequently, the BOF was first known as the LD (Linz-Donawitz) process Fig 1: Robert Durrer Within 40 years, virtually all of the steel in Japan and more than half of the steel worldwide was produced by the BOF.

WORING PRINCIPLE of the BOF : 

WORING PRINCIPLE of the BOF Charging scrap Charging hot meal (tilted 25 to 30% of the heat weight for not splashing) Blowing Oxygen Sampling Tapping Slag off

WORING PRINCIPLE of the BOF : 

WORING PRINCIPLE of the BOF

RAW MATERIALS : 

RAW MATERIALS Hot Metal ? decreasing the melting time and increase the compositon level of steel. Scrap ? In autogenously BOS operation, scrap is by far the largest heat sink. At 20 - 25% of the charge it is one of the most important and costly components of the charge. Alloys ?Bulk alloys are charged from overhead bins into the ladle. The common alloys are ferromanganese (80%Mn, 6%C, balance Fe), silico-manganese (66%Mn, 16%Si, 2%C, balance Fe), and ferrosilicon (75% Si, balance Fe). Aluminum can be added as shapes and/or injected as rod. Sulfur, carbon, calcium, and special elements like boron and titanium are fed at the ladle furnace as powders sheathed in a mild steel casing about 1/2 inch in diameter.

RAW MATERIALS : 

RAW MATERIALS Fluxes ? Fluxes serve two important purposes. First they combine with SiO2 which is oxidized from the hot metal to form a "basic" slag that is fluid at steelmaking temperatures. This slag absorbs and retains sulfur and phosphorus from the hot metal. Lime (95+% CaO) and dolomite (58%CaO, 39% MgO) are the two primary fluxes. They are obtained by calcining the carbonate minerals, generally offsite in rotary kilns. Calcining CaCO3 and MgCO3 liberates CO2 leaving CaO or MgO. Coolants?Limestone, scrap, and sponge iron are all potential coolants that can be added to a heat that has been overblown and is excessively hot

USED REFRACTORY PROPERTIES : 

USED REFRACTORY PROPERTIES The basis for most refractory bricks for oxygen steelmaking vessels in the world today is magnesia, MgO, which can be obtained from minerals or seawater. For magnesia, the lower the boron oxide content, and the lower the impurity levels (but with a CaO/SiO2 ratio above 2 to avoid low melting point intergranular phases) causes the greater the hot strength of the brick. Carbon is added as pitch (tar) or graphite.

USED REFRACTORY PROPERTIES : 

USED REFRACTORY PROPERTIES The penetration of slag and metal between the refractory grains, mechanical erosion by liquid movement, and chemical attack by slags all contribute to loss of lining material. Over the years, there have been numerous operating developments designed to counteract this lining wear: Critical wear zones (impact and tap pads, turndown slag lines, and trunion areas) in furnaces have been zoned with bricks of the highest quality.

USED REFRACTORY PROPERTIES : 

USED REFRACTORY PROPERTIES "Slag splashing" whereby residual liquid slag remaining after the tap is splashed onto the lining with high pressure nitrogen blown through the oxygen lance. This seemingly simple practice has increased lining life beyond all expectations, from a few thousand to over 20,000 heats per campaign. Instruments are now available to measure lining contours in a short time period, to maximize gunning effectiveness using MgO slurries. Dolomite (40%MgO) is added to the flux addition to create slags with about 8% MgO, which is close to the MgO saturation level of the slag. Improved end-point control resulting in lower FeO levels and shorter oxygen-off to charge intervals have reduced refractory deterioration

CONCLUSION : 

CONCLUSION In the world, steel making processes are needed directly with the necessary of the steel products. However, today manufacturers are affected by crisis we hope that it will increase day by day. Therefore steelmaking will stay forever. Uncertainly steel producers and manufacturers need BOF process and its refractories.

Slide 13: 

Thank you for your attention!

REFERENCES : 

REFERENCES http://www.energytechpro.com/Demo-IC/MoreDetail/Iron_BF_BOF.htm http://www.substech.com/dokuwiki/doku.php?id=basic_oxygen_furnace_bof http://www.britannica.com/EBchecked/topic/54973/basic-oxygen-process http://en.wikipedia.org/wiki/Basic_oxygen_furnace http://www.steel.org/AM/Template.cfm?Section=Articles3&TEMPLATE=/CM/ContentDisplay.cfm&CONTENTID=12306 http://basicoxygenfurnace.blogspot.com/ Charles A. SCHACHT,” refractories handbook”, Marcel Dekker, New York,Basel