Application of the hottest unshaped refractory in

The wind speed is usually 2 ~ 3m/s. The application of unshaped refractories on the permanent layer of refining ladle

the refining equipment of the first refining and rolling plant of Anyang steel includes ladle furnace (LF) and vacuum degassing device (VD). The refining means include arc heating, argon stirring, alkaline slag making in the ladle, vacuum degassing, etc. Strengthen the thermodynamic and dynamic conditions of steel slag reaction in the ladle, and carry out a series of treatments such as temperature rise, composition adjustment, deoxidation, desulfurization, degassing, inclusion removal and inclusion denaturation in a short time to obtain liquid steel with high purity and uniform composition. However, lf+vd refined liquid steel puts forward higher requirements for the performance of ladle refractories and masonry technology, Therefore, the material and masonry technology of the permanent layer of the ladle are very important to improve the overall life of the ladle

refining ladle structure

the 100t refining ladle structure of Anyang steel is that the inner side of the permanent layer of the ladle is in contact with the high-temperature working layer, and the outer side is close to the high aluminum injection felt (insulation layer) and the steel ladle wall. The thickness of the refractory material of the permanent layer is generally 70 ~ 110mm, and there is a temperature difference of 000 ~ 1650 ℃ on both sides during use, so the rigidity of the host is low

material selection and masonry process of permanent layer

Angang 100t refining ladle permanent layer refractory and masonry process have experienced three modes: high aluminum T-3 brick masonry, light castable mold overall knot and gravity castable mold knot free

1 process analysis of original refractories

the factory first used high alumina T-3 bricks to build the permanent layer of ladle, that is, lay one layer of high alumina bricks flat or side outside the thermal insulation layer (high alumina jet felt). Because of its cumbersome process, frequent maintenance, easy steel penetration in brick joints, low service life and high cost, it has been gradually replaced by amorphous refractories, and the overall knotting process of lightweight castable mold has been adopted. The process is carried out in stages: ① first install the brick mold, lay a layer of high aluminum blowing felt on the bottom and wall of the package close to the steel shell, and then knot the permanent layer of the bottom of the package with evenly stirred light castables; ② After the pouring material at the bottom of the package solidifies, put the knotting mold of the package wall into the package one by one and fix it (the gap between the mold and the surrounding area is required to be uniform), then inject the mixed light pouring material into the gap between the mold and the steel shell (do not peel off the high aluminum blowing felt or roll into the pouring material), and then use the vibrating rod to vibrate the pouring material evenly and compactly; ③ Let it stand for 8 ~ 12h, the mold will come out, and the working layer will be built after baking for 12h. This process has the advantages of simple process, convenient maintenance and low cost. It is widely used in domestic steel mills at this stage; The disadvantage is that there are still cumbersome processes such as formwork setting, vibration, demoulding and baking, and the masonry process and materials must be further optimized. Practice has found that if the permanent layer is baked together after the package is built, there will be cracks due to the inconsistent deformation of the permanent layer and the working layer during the drying process, resulting in "steel drilling"

2 analysis on the overall knotting process of new unshaped refractories

on the basis of application research, aiming at the problems existing in lightweight castables, the factory has summarized a set of overall knotting process of ladle permanent layer suitable for its production characteristics by referring to the experience of similar enterprises at home and abroad. There is no mold self flowing material knotting ladle permanent layer. The physical and chemical indexes of the selected self flowing castables are shown in Table 1. Table 1 Comparison of physical and chemical indexes between lightweight castables and new self flowing castables

materials and physical and chemical indexes lightweight castables self flowing castables w (Al2O3)/% 3092.0w (MgO)/% -6.0w (SiO2)/% 300.3 apparent porosity/%:110 ℃, 24h17.3 1500 ℃, 3h23.6 linear change rate/% (1500 ℃, 3H) 0 ~ -0.6 +1.54 bulk density (g · cm-3):110 ℃, 24h1.3 3.01 1500 ℃, 3h2.91 compressive strength/mpa:110 ℃, 24h37.1 1500 ℃, 3h3 54.0 adhesion strength/mpa (1200 ℃, 3H) 53.2 high temperature flexural strength/mpa (1400 ℃) ≥ 0.9 7.0 thermal conductivity/(w · M-1 · k-1) (700 ℃) 0.35

knotting process of self flowing castable of new unshaped refractory: ① install brick mold, and lay a layer of high aluminum blowing felt on the steel shell at the bottom of the package; ② Use a mixer to mix the self flowing castable to the self flowing state, and tie the permanent layer at the bottom of the bag; ③ After it solidifies, build the bottom working layer; ④ Lay a layer of high aluminum blowing felt on the wall clad steel shell; ⑤ The width between the masonry working layer and the high aluminum blowing felt is the knot thickness of the permanent layer (generally 70 ~ 110mm). When the cladding working layer is built to 3 ~ 5 layers (300 ~ 500mm high), inject the self flowing castable into the gap between the cladding working layer and the high aluminum blowing felt, which is mainly driven by the national policies and measures such as promoting economic structure adjustment, supporting scientific and technological progress, and paying attention to people's livelihood, insert it with a trowel, and repeat the above steps, Until the completion of ladle masonry; ⑥ According to the optimized ladle baking system, it can be used online after baking for 24h. This process inherits the advantages of its overall knotting permanent layer method. Its characteristics are: ① the permanent layer is built together with the working layer, which is closely combined. The deformation of the permanent layer refractory baked at the same time is decomposed, and there will be no cracks, and the molten steel cannot penetrate, which improves the safety factor of the ladle; ② The strength of the self flowing castable of the permanent layer is large, so the permanent layer is not easy to be poured out or damaged when unpacking and turning over, and the service life is extended; ③ The procedures of formwork setting and demoulding are cancelled, and the refractory materials do not need to vibrate during the masonry process, which avoids the vibration deformation of ladle bricks by vibrating rods, simplifies the process and reduces the labor intensity; ④ There is no process of baking the permanent layer separately. The ladle is baked for 24h with the optimized baking curve, which can ensure its baking effect. In practice, there is no problem of gas rise in molten steel due to the quality of ladle baking. Compared with the first two masonry processes, it saves time, labor and costs

effect comparison

see Table 2 for the comparison of different materials and masonry processes used in the permanent layer of the ladle. Table 2 Comparison of different materials and masonry processes used in the permanent layer of refining ladle

project high aluminum T-3 brick masonry light castable knot self flow castable no mold knot construction method masonry mold pouring no mold pouring masonry process is complex and simple refractory maintenance part repair part repair part repair part baking method bake separately after demoulding and bake together with the working layer, There is no need to bake refractory separately. Life/furnace 200 ~ 500 1000 ~ 1200 1500 tons of steel refractory cost/yuan 0.1750.106 0.088 allowable service temperature/℃ 1300 ~ 1400 1650 ~ 1700 1650 ~ 1700

the modes of refractory brick masonry (high alumina T-3 brick) and light castable mold knotting used by Angang 100t refining ladle have serious damage in the use of the permanent layer, and the use effect is not ideal: ① there are signs of steel seepage in the brick joints of the permanent layer of refractory brick masonry ladle, The unpacking process is very easy to be removed together with steel penetration, and the service life is short; After the ladle edge is transformed into a vertical pressing plate, it cannot play the role of pressing the permanent layer bricks of the ladle, and the permanent layer bricks are easy to be partially poured out during unpacking and turnover. ② Although the problems of easy damage, short service life and high cost caused by refractory brick masonry have been solved by using light-weight injection materials and the permanent layer of the ladle with the overall knot of the mold, many new problems have arisen: such as the large ladle, difficult demoulding, easy damage to the overall mold, and cumbersome installation and demoulding of the segmented mold; During the pouring process, a vibrating rod is required to vibrate the castable constantly to prevent defects such as pores; The permanent layer after demoulding needs to be baked or dried separately, otherwise the light castable with low strength is easy to cause the permanent layer to fall off in the next masonry step; The ladle is knotted from the permanent layer → baked in the permanent layer → masonry in the working layer → baked in the working layer → online. The service cycle is long, time-consuming and laborious, and the cost is high, reducing its use effect and promotion value

the permanent layer of the ladle is replaced by the integral masonry of self flowing castable, which overcomes the shortcomings of the first two processes, improves the comprehensive benefits, and has good application effects. The practical test results: the average life of the permanent layer of the ladle is increased from 260 heats to 1500 heats after the transformation; The overall average life of the ladle is increased from 59 times (9117.5min) to 75 times (11885min) after the transformation of the mechanical properties of the steel used in the steel structure; Basically put an end to the "steel threading" accident of ladle slag line; Labor intensity is significantly reduced; At present, the insulation effect, material strength and optimized baking curve of gravity castable can meet the requirements of production and use. However, the thickness of the permanent layer that is not easy to be damaged will gradually increase during use, so the actual thickness should be checked frequently to avoid the reduction of the ladle volume

according to the statistical results of ladle refractory consumption, the cost per ton of steel for permanent layer using high aluminum T-3 brick permanent layer is 0.175 yuan, that for permanent layer knotting with castable mold is 0.106 yuan, and that for ladle knotting without mold with self flowing castable is 0.088 yuan. Based on the annual steel output of 2million tons, the annual cost savings of refractory materials for the permanent layer of ladle is (0..088) yuan/t × 2.2 million T = 191400 yuan, plus 84000 yuan of mold manufacturing cost in one year, the annual benefit: (8.4+19.14) =275400 yuan, excluding the benefits brought by improving service life, reducing accidents and reducing labor intensity

conclusion

the selection of economical and appropriate permanent layer refractory and reasonable masonry technology has improved the service life of the permanent layer and the whole ladle, reduced the consumption of refractory materials, reduced the number of "ladle penetration" accidents, and achieved good use effect and economic benefits. (end)