Process for optimizing steel fabrication

Abstract

A process for optimizing steel fabrication. The process includes optimization of treatment in the ladle based on accurate determination of steel weight, slag carryover and furnace heel. The unification of the dip test process together with ladle profiling using information from the slag, side and bottom regions of the ladle results in the quantitative determination of key factors to optimize steel composition with minimum slag carryover in the absence of scales to determine required masses of metal charge and ladle weight as examples. Caprices of the process include significant improvements in ladle refractory and specification steel quality.

1 . A process of optimizing steel fabrication, comprising the steps of:
 providing a first carrier vessel for retaining liquid steel;   geometrically determining the volume of said carrier vessel;   determining, while tapping, a steel weight and slag weight for a given height of slag and steel in said carrier vessel;   profiling said carrier vessel using slag line, barrel and ladle bottom life information;   determining the height of steel in said carrier vessel;   determining slag carry-over weight and steel weight;   a refining stage including:
 de-oxidizing said steel and slag, alloying and refining the steel to bring chemical elements contained therein within predetermined limits; and 
 a casting stage including:
 discharging refined steel from said carrier vessel into an intermediate vessel for passage into a mould; 
 
   controlling discharge by timing the flow of steel; and   maintaining during discharge the level of steel in said mould, whereby liquid steel levels, flow control and casting are integrated for optimizing steel fabrication.   
     
     
         2 . The process as set forth in  claim 1 , wherein geometrically determining the volume of said first carrier vessel includes determining wear rate for each course of refractory bricks in said first carrier vessel. 
     
     
         3 . The process as set forth in  claim 2 , further including the step of dividing each course of said refractory bricks into a frustum of a cone. 
     
     
         4 . The process as set forth in  claim 3 , including determining the volume of each frustum. 
     
     
         5 . The process as set forth in  claim 1 , further including the step of generating a first carrier vessel profile algorithm, said first carrier vessel comprising a ladle. 
     
     
         6 . The process as set forth in  claim 5 , further including the step of calculating at least one of ladle volume, steel weight and slag weight for a given height of steel and slag. 
     
     
         7 . The process as set forth in  claim 5 , wherein said steel treatment in the ladle includes adding alloying agents to said steel in said ladle. 
     
     
         8 . The process as set forth in  claim 7 , wherein some of the said alloying agents are added in sequence. 
     
     
         9 . The process as set forth in  claim 8 , wherein said sequence comprises adding Aluminum, Manganese and Silicon alloys. 
     
     
         10 . The process as set forth in  claim 7 , wherein some of the said alloying agents are added simultaneously. 
     
     
         11 . The process as set forth in  claim 10 , further including the step of testing a sample of steel in the ladle to determine concentrations of dissolved elements. 
     
     
         12 . The process as set forth in  claim 11 , further including the step of adding the model-recommended amounts of at least Chromium, Nickel, Molybdenum, Vanadium, Niobium alloys based on requirements for product specifications. 
     
     
         13 . The process as set forth in  claim 7 , further including the step of adding Titanium and Boron alloys once said steel is fully de-oxidized. 
     
     
         14 . The process as set forth in  claim 1 , further including the step of adding a Calcium containing alloy. 
     
     
         15 . The process as set forth in  claim 1 , wherein said intermediate vessel is a tundish. 
     
     
         16 . The process as set forth in  claim 1 , further including the step of inverting steel from said mould into a solid slab. 
     
     
         17 . The process as set forth in  claim 5 , wherein a plurality of ladles are continuously cast. 
     
     
         18 . The process as set forth in  claim 17 , wherein discharge from said ladles is sequential. 
     
     
         19 . The process as set forth in  claim 15 , wherein said steel is discharged from said ladle to said tundish and subsequently to said mould. 
     
     
         20 . The process as set forth in  claim 18 , wherein discharge is controlled by gate means. 
     
     
         21 . A process for controlling and determining the amount of slag carryover in steel fabrication during tapping, comprising:
 providing an algorithm for the quantitative relationship between slag carryover and furnace heel;   determining required mass of tapped steel and level within a ladle for a mass of metallic charge and furnace heel from said algorithm;   providing level detection means for detecting the level of liquid steel within said ladle;   comparing determined level of steel within said level with a detected value; and   ceasing tapping when said detected value and determined value for said steel level in said ladle are equivalent, whereby slag carryover is minimized.   
     
     
         22 . The process as set forth in  claim 21 , wherein the step of ceasing is augmented with alarm means. 
     
     
         23 . The process as set forth in  claim 21 , wherein said steel level detection is performed using level detection means. 
     
     
         24 . The process as set forth in  claim 21 , wherein said relationship between slag carryover and furnace heel is established. 
     
     
         25 . A process of quantitatively determining at least one of slag carryover, furnace heel, ladle freeboard and tapped steel for optimizing steel fabrication, comprising:
 measuring slag depth and ladle freeboard;   generating a ladle profile equation from measurements of said slag depth, ladle freeboard and historical data on refractory brick dimension changes with increasing lives of the slag line, barrel and bottom regions of the ladle;   determining volumes of steel and slag, slag depth and freeboard height for a given ladle;   determining the amount of slag carryover during tapping;   correlating slag carryover to furnace heel;   determining volume and mass of steel at various levels for a given ladle;   calculating required tapped mass of steel and freeboard height for a given ladle; and   comparing said freeboard height with a calculated value during tapping to determine when to end tapping.   
     
     
         26 . The process as set forth in  claim 25 , wherein slag weight is computed from added flux agents at tap and determined slag carryover after tapping is complete. 
     
     
         27 . The process as set forth in  claim 25 , wherein freeboard is compared using radar. 
     
     
         28 . The process as set forth in  claim 27 , wherein said radar determines the height of said freeboard and said height is compared with said calculated value to effect termination of tapping at equivalency of the values. 
     
     
         29 . The process as set forth in  claim 25 , wherein said method produces on specification of steel 100% of the time. 
     
     
         30 . The process as set forth in  claim 25 , wherein said quantitative determinations are made in the absence of scales for measuring mass. 
     
     
         31 . The process as set forth in  claim 25 , wherein the useful life of said ladle is extended by between 12% and 20%. 
     
     
         32 . The process as set forth in  claim 25 , in combination with a slag detection system. 
     
     
         33 . A process for optimizing the fabrication of steel, comprising:
 providing a computational model for estimating the weight of steel in a furnace used in the process;   providing said model with required furnace heel or tap weight, slag line life, ladle number and ladle life;   determining with said model required freeboard for said ladle;   communicating freeboard value to a freeboard detecting means;   tapping said steel;   measuring said freeboard during tapping with said freeboard detecting means;   comparing measured freeboard with said model required freeboard;   terminating tapping when compared values are equivalent; and   computing the weight of tapped steel, carryover and furnace heel, whereby said process quantitatively determines requisite values for the process for optimization.   
     
     
         34 . The process as set forth in  claim 33 , wherein weight determinations are obtained in the absence of scales. 
     
     
         35 . The process as set forth in  claim 33 , wherein said model comprises a profiling model for determining ladle geometry. 
     
     
         36 . The process as set forth in  claim 33 , wherein said model includes parameters from the slag line of said ladle, the barrel region and bottom region. 
     
     
         37 . The process as set forth in  claim 36 , wherein said parameters from said slag line at least include distance from the ladle rim to the first slag line brick, diameter of said ladle at said ladle rim, the diameter, D 0 , of said ladle at said first slag line brick at zero life, height of the slag line region and the height of each said brick. 
     
     
         38 . The process as set forth in  claim 36 , wherein said parameters from said barrel region at least include the diameter of said ladle at the interface of the last slag line brick and first barrel brick. 
     
     
         39 . The process as set forth in  claim 33 , wherein said parameters from said bottom region at least include specificity of the contour of the bottom of the barrel, height of said bottom and the diameter of the frustum formed. 
     
     
         40 . The process as set forth in  claim 37 , further including the step of determining diameter change in said ladle from said first of said slag line to the last brick of said barrel region, where:
 for a newly re-bricked ladle with zero life, the diameter of the first course of bricks (top course of bricks for the slag line) is represented as D 0  and the diameter of the last course of bricks at the bottom of the ladle (last course of bricks for the barrel region) as D L , the difference in diameters can be expressed as
   Δ X=D   0   −D   L   (16)
 
   by designating H as the height of ladle from said first slag line brick course (zero point) to the last barrel region brick course and h i  as the vertical distance from the zero point to any point in the ladle below this, then the diameter of ladle at distance h i  equals   
       
         
           
             
               
                 
                   
                     
                       D 
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                         h 
                         i 
                       
                        
                       
                         
                           Δ 
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                            
                           X 
                         
                         H 
                       
                     
                   
                 
                 
                   
                     ( 
                     17 
                     ) 
                   
                 
               
             
           
         
       
     
     
         41 . The process as set forth in  claim 40 , further including the step of representing the established refractory wear rate for the position h i  by Y and said ladle life by n, where the diameter of said ladle is: 
       
         
           
             
               
                 
                   
                     
                       D 
                       0 
                     
                     - 
                     
                       
                         h 
                         i 
                       
                        
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           X 
                         
                         H 
                       
                     
                     + 
                     
                       2 
                        
                       Y 
                        
                       
                           
                       
                        
                       n 
                     
                   
                 
                 
                   
                     ( 
                     18 
                     ) 
                   
                 
               
             
           
         
       
     
     
         42 . The process as set forth in  claim 41 , further including the step of tabulating brick wear rate for each of said slag line, said barrel region and said bottom region for each brick course and a plurality of lives. 
     
     
         43 . The process as set forth in  claim 42 , optionally including the step of subtracting brick thickness from brick thickness at zero life for each region, course and life. 
     
     
         44 . The process as set forth in  claim 42 , optionally including the step of summing values obtained for each course for all lives and dividing by the number of values to determine wear rate in each course of each region. 
     
     
         45 . The process as set forth in  claim 33 , further including the step of determining trim quantities of Aluminum, Silicon and Manganese alloys for addition to tapped steel based on predetermined desired properties of finished steel. 
     
     
         46 . The process as set forth in  claim 45 , further including the step of de-oxidizing and alloying of said steel. 
     
     
         47 . The process as set forth in  claim 46 , further including the step of determining trim quantities of at least one of Nickel, Chromium, Niobium, Molybdenum, Vanadium based on said predetermined desired properties of finished steel. 
     
     
         48 . The process as set forth in  claim 47 , further including the step of analyzing the chemical composition of said steel for determining final trim quantities for said Nickel, Chromium, Niobium, Molybdenum, Vanadium. 
     
     
         49 . The process as set forth in  claim 48 , further including refining said steel to the point of complete de-oxidation and certain level of Sulfur. 
     
     
         50 . The process as set forth in  claim 49 , further including the step of determining a trim quantity for Titanium for said steel. 
     
     
         51 . The process as set forth in  claim 50 , including determining a trim quantity for Boron subsequent to the determination for Titanium. 
     
     
         52 . The process as set forth in  claim 51 , further including the step of determining the quantity of Calcium Silicide or Ferrocalcium trim for inclusion modification in said steel. 
     
     
         53 . The process as set forth in  claim 52 , further including the step of positioning said ladle for a continuous casting procedure and initiating flow of said steel into a steel mould. 
     
     
         54 . The process as set forth in  claim 53 , further including the step of determining flow rate of steel from said ladle to a tundish and subsequently to said mould. 
     
     
         55 . The process as set forth in  claim 54 , further including the step of determining the amount of steel remaining in said ladle. 
     
     
         56 . The process as set forth in  claim 54 , further including the step of monitoring slag level during casting. 
     
     
         57 . A process for optimizing the fabrication of steel, comprising:
 i) geometrically profiling a ladle used in said fabrication to determine weight of tapped steel, slag carryover and furnace heel;   ii) quantitatively determining the requisite alloy addition for predetermined steel product specifications; and   iii) controlling casting liquid steel with properties inherent from i) and ii), said steps i) through iii) being conducted in sequence and based on quantitative information derived from each precursory step, whereby said process quantitatively determines requisite values for the process for optimization.   
     
     
         58 . The process as set forth in  claim 57 , wherein said system further includes:
 providing said model with required furnace heel or tap weight, slag line life, ladle number and ladle life;   determining with said model required freeboard for said ladle;   communicating freeboard value to a freeboard detecting means;   tapping said steel;   measuring said freeboard during tapping with said freeboard detecting means;   comparing measured freeboard with said model required freeboard;   terminating tapping when compared values are equivalent; and   computing the quantity of tapped steel.