Factors affecting Lining Life of a Basic Oxygen Converter Sep20

Factors affecting Lining Life of a Basic Oxygen Converter...

Factors affecting Lining Life of a Basic Oxygen Converter The life, reliability and costs of lining in a basic oxygen converter are vital for the smooth operations of the steel melting shop utilizing basic oxygen process for steel production.  Higher lining life results into improved availability of the converter which in turn improves its productivity. Three important factors for achieving higher lining life of the basic oxygen converter (Fig 1) are (i) qualities of refractories and their laying pattern in the converter, (ii) operating practices followed, and (iii) monitoring of the lining wear and practices for the maintenance of the refractory lining. Development of improved refractory materials in combination with improved process control and better maintenance during campaigns make it possible to increase the lining life of the basic oxygen converter. Fig 1 Factors affecting lining life of the basic oxygen converter These days without exception, basic oxygen converters are lined with magnesia – carbon (MgO-C) refractories because of their superior properties than other types of converter lining materials. However zoned refractory lining practices are followed by using MgO-C refractories of different qualities in different areas of the converter. The causes of wear of refractories in the basic oxygen converter are either due to chemical reasons or due to the physical reasons. Chemical causes for the wear of the converter lining are mainly due to gaseous materials (oxidizing gases, reducing gases, and water vapour), liquid materials (slag. hot metal, and liquid steel melt), and solid materials (fluxes, and carbon disintegration).  Physical causes for the wear of the converter lining are excessive temperatures (poor dissipation, and hot spots), static mechanical stresses (spalling, and expansion), and dynamic mechanical stresses (abrasion, impact, and vibrations). The key wear mechanisms of the refractory lining of basic oxygen converter can...

Refractories for Basic Oxygen Furnace Aug28

Refractories for Basic Oxygen Furnace...

Refractories for Basic Oxygen Furnace  The main objective in the development of refractories for basic oxygen furnace (BOF) is to get a useful lining life of the wear lining so as to obtain maximum availability of the BOF. Longer lining life not only results in lower refractories cost but it also enables higher productivity through increased furnace availability. The following are the basic requirements from the refractories of BOF. Thermal spalling resistance Corrosion resistance Abrasion resistance Oxidation resistance Hot modulus of rupture BOF is lined normally with a permanent lining and above it there is a wear lining. Permanent lining thickness may vary from 100 mm to 120 mm and is made of chrome-magnesite permanent lining which is given on the full height of the BOF. The refractories available for use in wear linings of BOF range from tar or pitch bonded dolomite or magnesia (MgO), chrome magnesite, or magnesium chrome refractories to the advanced refractories that are made with resin bonds, metallics, graphites, and sintered and/or fused magnesia that can be with a purity of 99 %. Bricks are designed with a combination of critical physical properties to withstand the high temperatures and rapidly changing conditions/environment throughout the BOF heat cycle. A balance of different properties such as hot strength, oxidation resistance, and slag resistance is necessary from the BOF refractories for good performance. When BOF process of steelmaking was introduced in 1950s, converters were lined with tar dolomite bricks and stabilized burnt dolomite bricks. These refractories were then replaced by semi stabilized burnt dolomite bricks and tar bonded and fired bricks made of synthetic magnesia dolomite clinker. Chrome magnesite, or magnesium chrome refractories were used for lining of some BOFs.  High purity burnt magnesia bricks were also used in some of BOF...

Slag splashing technique in converter operation Mar24

Slag splashing technique in converter operation...

                     Slag splashing technique in converter operation  The erosion of refractory lining of a converter has a major contribution for the low lining life. Erosion occurs because of chemical erosion due to attack of slag and molten metal on the refractory of the converter at the high operating temperatures and because of thermal shocks as well as due to mechanical wear.  Slag splashing technique has been developed to counter this erosion and produce a freeze lining. Today slag splashing has become a powerful tool not only for increasing of the lining life of the converter but for increasing of the converter availability and maximizing of production besides reducing of the refractory and gunning costs. History Slag splashing technique was first developed in 1970 but was not put to large scale use. The Indiana Harbour plant of LTV steel was first to report success in 1992 with respect to improvement in the lining life by the use of this technique. Slowly this technique was used in the other steel melting shops of the world. Inland no. 4 BOF shop has reported a lining life of plus 60,000 heats. The process The slag splashing steps are as follows At the end of the previous heat the liquid steel is tapped in steel teeming ladle and molten slag remains in the converter. The converter operator visually inspects the slag condition to determine the quantity of slag conditioner to be added. The converter operator visually inspects the converter lining to determine if any specific area of the lining needs special attention. The molten slag is conditioned with respect to its temperature, FeO and MgO contents by the addition of a conditioner in required quantity. The converter is rocked for slag coating of the charge pad and tapping pad....

Role of MgO in prevention of lining corrosion in converters Mar06

Role of MgO in prevention of lining corrosion in converters...

        Role of MgO in prevention of lining corrosion in converters In the present day primary steelmaking processes, magnesia carbon bricks are the most commonly used refractory material for lining of the primary steel making furnace. The lining life differs from steel plant to steel plant because of refractory, operation and maintenance practices (Fig. 1). Fig 1 Effects of various refractory wear factors The effect of different parameters on the lining life is elaborated in Table 1 Table 1 Effects of different parameters on lining life Sl.No. Parameter Effect on life Severity of influence 1 Hot Metal Si Negative Medium Mn Positive Low Ti Negative Low 2 Slag Total Fe Content Negative High Basicity(CaO/SiO2) Positive Medium CaF2 Addition Negative Medium MgO content Positive High Al2O3 Content Negative Low Lime Addition Positive Medium 3 Blowing End point Temperature Negative High Blowing duration Negative Medium Production rate (Heats/day) Positive Medium Slag Volume Negative Low Atmosphere (CO/CO2) Positive Medium Delay in charging lime Negative Medium 4 Design of Converter Vessel volume Positive Low Cone angle Positive Low Multi hole blow lance Positive high The relationship of some of the parameters influencing the lining life of the converter is shown in Figure 2.   Fig 2 Relationship of the parameters affecting the lining life During the process of steel making, the main wear mechanisms are impact, corrosion, thermo-mechanical stresses and erosion. Though all the factors are important but corrosion due to dissolution of refractory material in the slag has a major effect on the lining life. During the process of steel making various oxides are produced which are fluxed with calcined lime to produce steel making slag. This slag is corrosive in nature and is in continuous touch with the surface of the converter lining. Due...