Application of the latest slag retaining technolog

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Application of the new slag retaining process in the Third Steelmaking Plant of Jigang

Abstract: the slag retaining process in the Third Steelmaking Plant of Jigang adopts a suspended slag retaining rod insertion device, which is advanced and reasonable in design and has good application effect. The thickness of ladle slag layer is about 10 ~ 30mm, the amount of slag per ton of steel is less than 2.7kg, and the alloy yield is increased by 5%. In order to improve the quality of molten steel, reduce consumption Stable production has created favorable conditions

key words: slag rod; Slag retaining process; Suspension slag stopper

adjust the speed valve appropriately according to the loading speed for loading

in recent years, with the needs of high-purity steel production, the matching metallurgical equipment and production process have also attracted great attention from the domestic industry. The slag retaining process of converter is an important part of the production process of high clean steel. Poor slag retaining effect will directly lead to high impurities in molten steel, large amount of phosphorus return, large amount of subsequent refining treatment and high consumption. Over the years, the domestic slag retaining process is relatively backward, resulting in low utilization rate of equipment, low degree of automation, high operation intensity and low success rate of slag retaining. The No.1 converter slag retaining process of Jinan Iron and Steel Group Corporation No.3 Steelmaking Plant (hereinafter referred to as Jinan Iron and steel No.3 Steelmaking Plant) has been demonstrated in detail during the design, and the suspended slag retaining rod insertion equipment has been adopted

1 structural type of suspended slag retaining rod insertion equipment

the equipment is installed above the converter rear platform. The mechanical part of the device is mainly composed of winch device, trolley transmission device, clamping mechanism, mobile trolley, floating idler, safety lock, heat shield and other parts. The structure is shown in Figure 1. The winch device is used to realize the rotation movement of the guide rail beam; The trolley transmission device is used to drive the mobile trolley and fix the floating idler and other parts; The clamping mechanism is used to realize the action of clamping and loosening the slag stopper rod; The mobile trolley is used to drive the clamping mechanism to move on the guide rail beam of the transmission device; The floating idler is used to improve the stress condition of the clamping mechanism and ensure the accurate positioning of the slag stopper

Figure 1 Schematic diagram of slag retaining mechanism

the main features of this set of equipment: (1) it is suspended and inserted behind the furnace, which does not occupy the site behind the furnace and does not affect other operations; (2) The travel of the mobile trolley, the rotation angle of the suspension main beam and the position of the suspension point are designed reasonably, and the equipment has compact structure and light weight; (3) Floating idlers improve the hit rate of slag stopper; (4) The cooling system extends the service life of vulnerable parts; (5) Equipped with rotating and linear ruler, it is convenient for manual adjustment and has a high hitting rate of pitching; (6) Safety lock and heat shield improve the operating environment; (7) The equipment has two control modes: linkage and manual, with high degree of automation, convenient and simple operation and low labor intensity

2 working principle

start the slag retaining equipment at the late stage of converter tapping (about 2/3 of tapping); The safety lock is loosened, the rotary hoist puts down the suspension main beam, the clamping mechanism clamps the slag stopper, and the cooling medium is opened; The rotary hoist works, and the hanging main beam inclines to a certain angle; The mobile trolley inserts the slag stopper into the tapping hole from the converter mouth; The clamping mechanism releases the slag stopper and exits the furnace. Taking advantage of the fact that the specific gravity of the slag stopper is between molten steel and molten slag, the slag stopper floats between the steel slag at the tap hole. When the tapping is near the end, the slag stopper immediately blocks the tapping port to prevent molten slag from flowing into the ladle. The key to the success of slag retaining lies in: first, the vanadium at the tap hole is scattered in nature when retaining slag, and the angle matches the position of the slag retaining rod on the clamping mechanism. The inner diameter of tapping hole in No. 3 steelmaking plant of Jigang is designed after unloading φ 160mm, the horizontal included angle is 10 °, and the tapping angle can be adjusted and positioned by the converter tilting angle display on the console. The position of the slag retaining rod should first be installed correctly and the clamping angle should be reasonable; Secondly, the adjustment of the rod dropping position of the clamping mechanism should be carried out from both horizontal and vertical aspects. After replacing the steel outlet sleeve every time, the position of the steel outlet will have a certain range of offset, and it is required to readjust the slag retaining stroke. First, adjust the converter positioning (rod feeding position) and the travel of the mobile trolley to determine the longitudinal position. The left and right movement of the side guide plate on the floating idler adjusts the horizontal position to realize the alignment of the slag stopper and the tapping port. The second is the reasonable design of slag stopper

the structure of slag retaining rod is shown in Figure 2. Its parameters are: slag stopper weight: 25kg; Specific gravity: 3.04 ~ 3.5g/cm3; Material: main component: Al2O3; Technical requirements: the slag retaining rod is dry and free of cracks. The material has high thermal stability and does not crack in the steel slag environment

Figure 2 slag retaining rod structure

3 on site usage

after the Third Steelmaking Plant of Jigang was put into operation, the slag retaining device has been tested under cold and heat load, and the performance of the equipment is stable. Before the furnace is 150 heats old, it has been put into operation for 146 heats to block slag, of which 140 heats have been put into operation, with a success rate of 95.9%. The successful heats of slag blocking have been 130 times, with a success rate of 92.6%

the reasons for the failure of slag retaining are: (1) at the initial stage of production, the slag is oxidized, the temperature is high, and the slag retaining rod is easy to crack; (2) The slag stopper is stored for a long time and becomes damp after absorbing water. From the number of heats with successful slag blocking, the slag amount of ladle is between 10 ~ 30mm, less than 350kg per furnace, and less than 2.7kg per ton of steel. The slag retaining is excellent, which effectively improves the quality of molten steel and the yield of alloy, and achieves the expected design effect

the design of the suspended slag retaining rod insertion equipment in the Third Steelmaking Plant of Jigang is advanced and reasonable. It has the advantages of high degree of automatic slag retaining, low operation labor intensity, good slag retaining effect and so on. The application of advanced slag retaining technology creates favorable conditions for improving steel quality, reducing energy consumption and stabilizing production. (end)

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