| Masteel's 2,500 cubic meters of 2#blast furnace was overhauled in May 2017,and the first generation furnace life was 13 years and 7 months.The major reasons for the overhaul of the blast furnace are that the water temperature difference between the stave near the iron gate breaches the warning line and the central cooling stave is damaged.This article investigates the copper staves from the 6th to the 9th floors of the furnace in the part of bosh to furnace body and the cast iron staves from the 10th to 13th floors of the furnace in the part of stack.The main reason for the damage of cooling stave was ascertained and reasonable measures were put forward.We took pictures of the whole cooled stave after stopping the furnace and recorded the damage.Then we photographed the disintegration of each of the 6-13 sections of stave walls and water pipes,and measured the amount of wear on the hot surface and the amount of bending deformation.The anatomical investigation was conducted on the 9-22#copper stave and the 11-37#cast iron stave to record the wall cracking and water pipe fouling.We performed metallographic microscopic analysis of cold and hot surface specimens.In addition,wall core samples were processed and the core samples were analyzed for their mechanical properties.At the same time,scale was collected for XRD analysis and XRF analysis.Finally,ICP composition analysis was conducted on the iron scraps at different positions from the hot side to the cold side of the cast iron stave.The conclusions of this article are as follows:?1?There were 27 burning damages in the 6th to 9th copper staves.Of these,26were burnt in the 9th stave,and 1 in the 8th stave was burned.59 water channels were broken.The average deformation of the 6th to 9th copper staves was 8.87mm,7.2mm,16mm,and 51.57mm,respectively.The maximum deformation was 76mm.The average wear was 1.4mm,7.72mm,9.46mm,and 14.16mm,respectively.The maximum amount of wear is up to 20mm.The damage to the copper stave is mainly concentrated on the 9th floor.10-13 layers of cast iron cooling stave A were damaged63 pieces,and the 13th layer A damaged most,reaching 23 pieces.The average hot surface wear of layers 10-13 were 127.25mm,122.35mm,125.28mm,and 136.12mm,respectively.The damage to the 13th stave is relatively serious.?2?Blast furnace temperature fluctuations,cooling channel wall fouling,the development of edge gas flow,and wall manufacturing defects are the main causes of cooling wall damage.Therefore,the stability of the furnace,the use of soft water closed circulation system,adjust the edge of gas flow and other measures can effectively inhibit the cooling wall damage process.?3?The thickness of the copper cooling stave of the 9th layer 22#is 0.4mm-0.75mm,and the scale composition is composed of CaO·P2O5,ZnO·P2O5,FeO?OH?,CaCO3,MgCO3,and Cu2SiS2.The seam of the seamless steel pipe and the copper sleeve obviously cracked,resulting in leakage of the cooling wall.When the water channel scale thickness is 0.5mm-1.0mm,the integrated heat transfer coefficient of the cooling wall is reduced by 61.93%-76.24%.After one generation of furnace service,the tensile strength,elongation and reduction of area of the copper stave wall were218.45 N/mm2,respectively,and the elongation was 30.00%.The reduction in area was44.44%.These performance meets service requirements.?4?The firebrick on the surface of the cast iron cooling stave of the 11th floor has been detached,and the maximum residual thickness of the cooling wall is 180mm.There are 4 obvious vertical cracks on the hot surface,and the crack spacing is consistent with the thickness of the ribs.There are two serious casting defects A and B in the upper part of the stave.The defect A is 125mm long,40mm wide,and 30mm high.The length of the defect B is more than 130mm,the widest point is 80mm,and the height is 40mm.The width of the gap between the main pipe and the stave body is0.05mm-0.1mm.The scale of the seamless steel pipe in the cast iron cooling stave is brown,the scale thickness of the hot surface pipe is 1.3-2.0 mm,the thickness of the cold surface scale is 0.7-1.3 mm,and the scale is composed of Fe3O4,CaO·P2O5,Fe2P2O7,and ZnCO3 phases.The integrated heat transfer coefficient of cast iron staves has been reduced by 38%-49%.The closer the milling material is to the hot surface,the lower the content of C and Si in the milling material.However,the closer to the hot surface,the closer K,Na,Zn and other elements in the milling material are to the hot surface.The samples near the cold surface are mainly distributed in the form of ferrite and lamella pearlite.The distribution of hot surface ferrite and cementite is less,the pearlite distribution is more,and the hot surface pearlite is obviously spheroidized.The mechanical properties of the cooling stave matrix decrease.The tensile strength of the specimen is 292.85MPa-307.87MPa,which is lower than the minimum requirement of ductile iron?450MPa?;the stretching rate is 0%,which is lower than the minimum specified value?10%?... |
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