Optimization After Ladle Expansion

The actual volume of ladle used in a company seriously affects the rhythm of converter production, and also restricts the capacity efficiency of 300t converter. The average furnace output of 300t converter at home and abroad should be greater than the nominal design capacity, while the company's average furnace output of 300t converter is less than 290t, which is an important bottleneck that has long been troubling the production efficiency. Therefore, the company is determined to carry out the ladle capacity increase research, to completely solve the various disadvantages caused by the ladle is too small, to realize the efficient and stable operation of production.

Ladle capacity increase and expansion modification

01 Tundish Capacity Increase Retrofit Requirements

In order to reduce the transformation cost, the company decided to maximize the use of the existing package shell, the bottom of the ladle, the bottom of the ladle support, tipping device for depreciation. The bottom of the ladle maintains the existing dimensions of the various departments, trunnion seat around the large support and ladle seat depreciation, excision and cylinder weld and heat-affected zone, respectively, both sides of the excision of 35mm. trunnion embedded in the length of the trunnion seat should be shortened, to maintain the inner trunnion fixed block and protruding parts of the original ladle wall, ladle tilting device unchanged for depreciation of the dimensions. The bottom of the bag first along the weld resection, resection of the bottom of the bag height of 90mm, the bag wall and the bottom of the bag welding position from the bottom of the bag inside flat to outside flat, transition welding, angle R20mm grinding smooth, the bottom of the bag from the transformation before the formation of a small step to the current and the bag wall is flush, the ladle can be guaranteed to be the same thickness after the permanent layer of masonry. The diameter of ladle body increased about 68mm after ladle capacity increase, so the steel plate of ladle body needs to be replaced, in order to ensure the strength, the thickness of steel plate was increased from original 40mm to 42mm. trunnion and trunnion seat part of ladle is the most critical part of ladle lifting.

The company's 37 existing ladle life of more than 8 years, trunnion lifting process has appeared to grind, for safety reasons, capacity expansion and transformation replacement trunnion. In order to ensure that the external dimensions of the ladle capacity increase remains unchanged, through the design institute review and approval of the waist hoop and tank seat new system, the inner dimensions of the shortened, but in order to ensure the strength of the increase in the thickness of the plate; ladle plus uncovering the lid hinge seat and the position of the upper mouth of the ladle and the horizontal distance is reduced by 35mm. the diameter of the lid and the ladle the same diameter, the hinged seat according to the diagram production construction.

02 Impact on other equipment

After the ladle capacity increase and remodeling, the increase of the ladle shell size has a certain impact on the related equipment. The company in the ladle capacity increase transformation fully considered the 480t overhead gantry hook, offline ladle baking, steel car, 480t over span car, LF furnace, RH furnace, CAS furnace, ladle capping system and casting machine rotary table and other key limitations, to ensure that the above main equipment will not be changed, and the other auxiliary equipment adjusted appropriately, so as to make the project has a good operability.

① Impact of expansion on gantry hooks

The center distance of gantry hook of 480t crane is 5600mm, after the diameter of ladle shell is increased, how to ensure the normal and safe lifting of ladle without replacing the gantry hook is a problem that must be solved. In order to ensure the stability of the gantry hook, after close calibration, both sides of the ladle bar plate in the direction of the width of the shortening of the thickness of the steel plate thickening, so as to ensure that the gantry hook spacing is unchanged. After the capacity increase of ladle, each ladle of molten steel increased from 290t to 320t, the weight of ladle shell is about 71t, the weight of refractory material is about 80t, the total weight is about 470t, and the load capacity of gantry truck is 480t, so the capacity increase has not exceeded the load of gantry truck.

②Effect of expansion on ladle pack tires

The diameter of the ladle body increases by about 68mm after the ladle capacity increase, so the original ladle tires used as the permanent layer of knotting need to be scrapped, and the diameter of the ladle tires increases accordingly and matches with the new capacity of the ladle, while other parts of the dimensions and structure remain unchanged.

③The impact of capacity expansion on ladle related auxiliary equipments

The height of ladle is not increased, so there is no impact on ladle offline baking, LF furnace, RH furnace, CAS furnace, but the thickening of ladle will have an impact on ladle cover, ladle bracket of steel car and fork arm of ladle rotary table. In order to try not to change the size of the current equipment, equipment professionals through on-site mapping tests and finally reached a consensus: the new ladle mouth diameter of 4700mm, and ladle lid diameter is comparable to the ladle lid, in order to prevent the lid from falling into the ladle, the requirements of playing the permanent layer and laying refractory bricks and then installed after the lid. Increase the capacity of the ladle seat diameter to 4386mm, seat into the steel water car and ladle fork arm on both sides of the spacing from the original 35mm to the current 10mm or so, the spacing is reduced on the ladle smooth seat into the ladle rotary table has a certain impact, the decision to grind thinning steel water car seat ladle frame and the ladle fork arm wear-resistant belt 15mm, and at the same time require the producer to make the diameter of the ladle in accordance with the negative tolerance control.

03 Expansion ladle masonry requirements

Cladding wall permanent layer before knotting in the cladding wall masonry ceramic fiber board, using lightweight casting material knotting. Lightweight materials in accordance with the amount of water about 6% to 8% control, mix well, placed in the new ladle tire, according to the existing process requirements. The bottom of the bag is knotted with heavy material, the bottom of the bag and the water outlet seat brick is still using the existing masonry methods, that is, the first to install the upper and lower seat brick, and then the bottom of the brick masonry, the gap between the brick and the brick should be less than 2mm, so that the brick joints are staggered vertically and horizontally, the brick joints are full of mud, the bottom of the bag masonry to find the correct, firmly stuck. For the expansion and transformation of ladle shell, ladle wall working layer using 190mm lining brick, slag line parts using 210mm magnesium carbon bricks, the formal implementation of the ladle to restore the capacity of the production organization before the need to ensure that the use of more than 25 times, the repair of the ladle wall working layer of 180mm lining bricks, slag line parts using 210mm magnesium carbon bricks.

Ladle bottom blowing optimization

01 Optimization of breathable brick structure

The original slit-type permeable brick in the use and pouring process of high temperature steel, slag may be through the gap into the bottom blowing permeable brick, resulting in the airway is seepage of steel, slag blockage. Therefore, a new type of slit composite diffusion type permeable brick is designed and produced, as shown in Fig. 1.

The breathable brick mainly includes argon hard tube, brick core body, round table (slit block), diffusion block, and brick core seat block. The argon hard tube is welded together with the iron of the brick core body, the round table (slit block) is installed in the internal lower part of the brick core body, the diffusion block is installed in the upper part of the internal round table (slit block) of the brick core body, and the brick core seating brick is on the outermost side, which will be wrapped around the upper part of the argon hard tube and the brick core body. Figure 1 slit - diffuse composite gas permeable brick after the test to promote the use of this composite bottom blowing brick was found to meet the current normal use, and gas permeability from 99.72% to improve and stabilize at 99.85% or more, to ensure that the bottom blowing effect of the ladle.

02 Improve the material of permeable brick, improve the life of permeable brick

The original bottom-blown permeable brick is mainly composed of plate corundum, spinel and chromium oxide, and in the actual use process, it is found that its thermal shock stability and compressive strength are not high, and it may be deteriorated under the hot pressure of molten steel, which affects the life and blowing rate. Therefore, the introduction of aluminum-magnesium spinel and chrome corundum is considered, which can make the permeable bricks form microcracks under the bad condition of alternating hot and cold and buffer the thermal stresses due to the temperature change, so as to reduce their spalling and improve the thermal shock resistance. In addition, considering that the company's ladle is a 300t large-scale ladle, the effective height of the loaded steel reaches 4m, it is necessary to enhance the pressure-resistant strength of the bottom-blown breathable brick, so the content of alumina powder is adjusted appropriately. The improved material of breathable brick is mainly composed of about 80% corundum, alumina powder, 2.5% chromium oxide and magnesia-aluminum spinel, and another 3% binding agent.

Dephosphorization furnace steelmaking, if the ladle bottom blowing brick life in more than 15 furnaces, in order to ensure that the bottom blowing blowing rate, burned bottom blowing, put after the diversion of sand in the east and west sides of the bottom blowing brick grooves, each put 10kg diversion of sand. Observe the residual thickness of the breathable bricks after unpacking at any time, under the premise of safe use, so that the bottom blowing breathable bricks to get the maximum degree of utilization, improve its service life. Bottom blowing brick life ≥ 20 furnace or after observation of the bottom blowing brick erosion is serious, with special tools according to the size of different tipping machine to measure the erosion depth of the bottom blowing brick, when the erosion depth of ≥ 280mm must be dumped bag. The above measures will increase the average service life of ladle bottom blowing brick from 23 to 25 furnaces, and the average age of ladle mid-repair is also significantly improved.

03 Optimization of the blowing device

After the ladle capping project is put into full operation, the temperature of the ladle lining can be up to 1300℃ or more, and the ordinary oxygen-burning pipe will be bent when it enters the ladle, which makes the blowing difficulty greatly increased. The inability of the ladle bottom blowing bricks to carry out effective blowing will cause the bottom blowing bricks to have insufficient air permeability, which will result in a significant increase in the number of abnormal furnaces of refining bottom blowing. In order to solve this problem, the blowing device has been improved. The device adopts the inner tube and outer tube connected through the retaining ring, gas pipe welded to the outer tube and the outer tube connected to the handle welded to the outer wall of the outer tube, the outer tube and the inner tube for the gas channel, to ensure that the cover ladle bottom blowing bricks fast blowing, while avoiding the use of oxyfuel tube blowing bottom blowing bricks due to excessive blowing and reduce the service life of bottom blowing bricks.

04 Optimization of bottom blowing process

In order to avoid the automatic bottom blowing pipeline leakage on the bottom blowing impact, the ladle automatic bottom blowing pipeline from the ladle mushroom head female end out of the ladle down into the bottom of the packet and hand-inserted pipe line connection is changed to the mushroom head out of the ladle up along the ladle wall through the ladle reinforcing bar holes and hand-inserted pipe in the hand-inserted pipe on the left side of the connection, when not using the automatic bottom blowing pipeline ladle or automatic bottom blowing pipeline bottom blowing mushroom head port leakage occurs when the valve of the automatic bottom blowing pipeline will be Close the automatic bottom blowing pipeline valve when the automatic bottom blowing pipeline is not used or when there is leakage at the mushroom head port of the automatic bottom blowing pipeline, and use the hand pipe to carry out bottom blowing operation. The bottom of the ladle blowing brick blowback pipeline leakage inspection method: the first argon pressure reducing valve off, will open the argon valve, observe the flow display, if the display shows the number of 50L/min or less that there is no leakage of the pipeline, if the number is greater than 50L/min, it is explained that the blowback pipeline and joints may be there is a leakage of gas, need to be inspected and dealt with in a timely manner. After the implementation of the above four measures to optimize the bottom blowing process, the blowing rate of the ladle has been significantly improved.

The annual average blowing rate of bottom blowing was increased from 99.84% to over 99.98%, the average service life of ladle bottom blowing bricks was increased from 23 furnaces to 25 furnaces, and the number of abnormal ladle discharges due to bottom blowing bricks was reduced by 5 sets per month. The technical and economic indicators have reached the level of advanced steel mills such as Baosteel, POSCO and Nippon Steel.

After the expansion ladle of the company is online and running, the steel bearing quality is increased from original 290t to current 310t, which directly lays the foundation for the stable and excellent production of the steelmaking department, and the annual capacity of one steelmaking converter is increased by 7%, about 630,000t, and the total annual production capacity is reached to 9.7 million tons, which is close to the level of the production of POSCO Gwangyang. Through the ladle expansion renovation effectively promoted the increase of steelmaking output, thus effectively reducing the impact of the single-furnace pre-furnace auxiliary time on the output, and at the same time, due to the increase of single-furnace output, tons of steel power costs, refractory costs and labor costs are reduced accordingly, which greatly reduces the cost of production of tons of steel. At the same time the ladle bottom slit composite diffuse gas permeable brick and the use of new coal oxygen gun and bottom blowing process improvement, so that the blowing rate from 99.84% and stabilized at 99.98% or more, while the bottom blowing brick life has been significantly improved, to reach the level of Baosteel, South Korea, POSCO, and Nippon Steel and other advanced steel mills.

Zinfon Refractory Technology Co.,Ltd

We are a refractory material supplier integrating R&D,production,construction,warehousing and commerce.

We are offering various magnesia and alumina refractories including both shaped and unshaped products, raw materials and related chemical products.

We are certified to ISO9001, ISO14001, ISO45001 and other national and local certifications as follows:

Send Inquiry Now