Installation of Ladle Silica Refractory Mortar

1. New ladle surface treatment: For new ladles, the inner surface of the shell should be cleaned first to remove rust, oil, dust and other impurities. After cleaning, apply a layer of release agent evenly on the inner surface (the release agent can be machine oil or special refractory release agent) to prevent the mortar from adhering to the shell and facilitate subsequent maintenance and replacement. The release agent should be applied thinly and evenly, and no accumulation should be allowed.

2. Old ladle surface treatment: For old ladles that need maintenance, first remove the damaged refractory bricks and residual old mortar. The removal should be thorough, and no loose old mortar or broken bricks should be left. The surface of the remaining old lining should be polished smooth, and cleaned with a brush to remove dust and debris. If there are cracks on the old lining, the cracks should be expanded into V-shaped grooves, cleaned, and then filled with new mortar to ensure the bonding between new and old mortar. It should be noted that the old ladle shell should be checked for deformation, and if deformation is found, it should be corrected first to avoid affecting the installation of refractory bricks and mortar.

2.4 Construction Environment Control

The construction environment has a great impact on the installation quality of ladle silica refractory mortar. It is necessary to control the temperature, humidity and wind speed of the construction environment to ensure the normal hydration reaction of the mortar and the bonding effect.

1. Temperature control: The optimal construction temperature is 15 ~ 25℃. When the temperature is lower than 5℃, the hydration reaction of the mortar will be slowed down, the setting time will be prolonged, and the bonding strength will be reduced; even freezing may occur, leading to cracking of the mortar after thawing. In winter construction, thermal insulation measures should be taken: use canvas or plastic film to set up a warm shed around the construction area, and use a heater to raise the environment temperature to above 5℃. It should be noted that the heater should not be directly directed at the mortar surface to avoid local overheating and cracking. When the temperature is higher than 35℃, the water in the mortar will evaporate rapidly, leading to cracking and peeling. In summer construction, take sunshade and cooling measures, and appropriately increase the frequency of moisturizing to avoid rapid water loss.

2. Humidity control: The construction environment humidity should be controlled at 40% ~ 70%. If the humidity is too high (more than 80%), the mortar will set slowly, and the surface is easy to get moldy, affecting the strength; if the humidity is too low (less than 30%), the water in the mortar will evaporate too fast, leading to insufficient hydration and reduced bonding strength. In humid environments, strengthen ventilation; in dry environments, appropriately increase the water-material ratio (but not exceed the maximum limit specified in the product manual) and do a good job in moisturizing.

3. Wind speed control: The construction area should avoid strong wind (wind speed exceeding 5m/s). Strong wind will accelerate the evaporation of water in the mortar, leading to surface cracking and affecting the bonding effect. If strong wind occurs, set up windshields around the construction area to reduce the impact of wind on the mortar.

3. Step-by-Step Installation Process of Ladle Silica Refractory Mortar (Core Section)

The installation process of ladle silica refractory mortar is divided into five key steps: mortar mixing, refractory brick masonry and mortar smearing, joint filling, surface finishing and post-installation curing. Each step must strictly follow the operation specifications to ensure the installation quality. The entire installation process should be continuous, and the interval between each step should not be too long to avoid the initial setting of the mortar affecting the bonding effect.

3.1 Mortar Mixing: Ensure Uniformity and Fluidity

Mortar mixing is the first step of installation, and the uniformity and fluidity of the mortar directly affect the bonding effect and construction performance. It is necessary to strictly follow the water-material ratio and mixing process to avoid uneven mixing or improper water addition.

1. Mixing ratio: According to the product manual of ladle silica refractory mortar, accurately measure the mortar and mixing water. The general water-material ratio is 6% ~ 8%, which can be adjusted according to the ambient temperature and humidity. For example, in dry and high-temperature environments, the water-material ratio can be appropriately increased by 0.5% ~ 1%; in humid and low-temperature environments, it can be appropriately reduced by 0.5% ~ 1%. It is strictly prohibited to add water arbitrarily to avoid reducing the strength and anti-erosion performance of the mortar.

2. Mixing process: Follow the principle of "first dry mixing then wet mixing". First, pour the measured ladle silica refractory mortar into the forced mixer, dry mix for 1 ~ 2 minutes to ensure that the powder is uniform and free of agglomeration. Then, slowly add the measured mixing water while stirring, and continue mixing for 4 ~ 5 minutes until the mortar is uniform, the surface is pulpy, free of dry powder particles and agglomeration, and the fluidity meets the construction requirements (holding into a ball by hand, scattering when released). The total mixing time should not be less than 5 minutes, and the maximum should not exceed 10 minutes to avoid the initial setting of the mortar.

3. Mixing precautions: The mixed mortar should be used up within 20 ~ 30 minutes (the specific time is adjusted according to the ambient temperature). If the mortar is found to be initially set, agglomerated or lose fluidity, it should be discarded and not reused. After each batch of mortar is mixed, clean the mixer thoroughly to avoid residual mortar agglomerating and affecting the next batch of mixing quality. Do not mix different types or batches of mortar to avoid chemical reactions and affect the performance.

3.2 Refractory Brick Masonry and Mortar Smearing: Ensure Tight Bonding

Refractory brick masonry and mortar smearing are the core links of installation, which require ensuring that the bricks are neatly arranged, the mortar is evenly smeared, and the bonding between bricks and mortar is tight. The masonry should follow the principle of "错缝砌筑, full mortar, and accurate size" to avoid gaps and voids.

1. Masonry sequence: The masonry of ladle silica refractory bricks should be carried out from the ladle bottom to the ladle wall, and then to the ladle mouth, layer by layer. For the ladle bottom, masonry should be carried out from the center to the surrounding area; for the ladle wall, masonry should be carried out from the lower part to the upper part, and the vertical joints should be staggered (staggering distance not less than 1/3 of the brick length) to improve the integrity and stability of the lining.

2. Mortar smearing: Before masonry, smear a layer of mixed mortar on the surface of the refractory brick (the thickness of the mortar layer is 2 ~ 3mm), and the smearing should be even, without missing smearing or accumulation. The mortar should be smeared to the edge of the brick, but not overflowing (to avoid cleaning after masonry). For the contact surface between the brick and the ladle shell (or old lining), the thickness of the mortar layer can be appropriately increased to 3 ~ 4mm to ensure tight bonding.

3. Brick masonry: After smearing the mortar, place the refractory brick in the designated position, adjust the position of the brick to ensure that it is flat and vertical, and the horizontal and vertical joints are uniform. Use a rubber hammer to gently tap the brick to make the mortar fully fill the gap between the bricks, and the brick is closely bonded with the mortar. Do not use a heavy hammer to tap, so as to avoid damage to the brick or uneven mortar layer. After each layer of bricks is masonry, check the flatness and verticality with a level ruler, and adjust in time if there is any deviation.

4. Key points for special parts: For the ladle mouth and other parts that are easily eroded, the masonry should be more dense, and the mortar layer can be appropriately thickened. For the corner parts, the bricks should be cut according to the size requirements, and the cut surface should be smooth. The mortar should be fully filled between the cut bricks to avoid gaps. It should be noted that the brick seam thickness of the silica brick masonry should be strictly controlled, and the average expansion joint should be reserved according to the standard (12mm/m) to adapt to the thermal expansion of the refractory material at high temperatures.

3.3 Joint Filling: Ensure Sealing and Integrity

Joint filling is an important step to ensure the sealing performance of the ladle lining. After the masonry of each layer of refractory bricks, the horizontal and vertical joints between the bricks should be filled with mortar in time to avoid gaps, which may lead to steel melt leakage or slag erosion.

1. Joint filling material: Use the same ladle silica refractory mortar as the smearing mortar, and the water-material ratio can be appropriately reduced by 0.5% ~ 1% to improve the compactness of the joint filling mortar.

2. Joint filling operation: Use a joint filling tool (such as a joint filling knife) to fill the mortar into the gaps between the bricks, and press it tightly to ensure that the mortar is fully filled in the gaps, without voids or air bubbles. The thickness of the joint filling should be consistent with the thickness of the mortar layer (2 ~ 5mm), and the surface of the joint filling should be flush with the surface of the bricks, without protrusion or depression. For the gaps larger than 5mm, the mortar can be mixed with an appropriate amount of fine silica powder to increase the compactness; for the gaps smaller than 2mm, it is not necessary to fill separately, but ensure that the mortar between the bricks is full.

3. Joint filling precautions: The joint filling should be carried out in time after the masonry of the bricks (within 10 ~ 15 minutes), so as to avoid the initial setting of the smearing mortar affecting the bonding between the joint filling mortar and the bricks. After joint filling, clean the surface of the bricks in time to remove the excess mortar, so as to keep the surface of the lining clean and smooth.

3.4 Surface Finishing: Improve Surface Flatness and Sealing

After the masonry and joint filling of the entire ladle lining are completed, the surface of the lining should be finished to improve the flatness and sealing performance, and avoid the surface unevenness affecting the use effect and service life.

1. Surface cleaning: Use a brush or scraper to remove the excess mortar and debris on the surface of the lining, and ensure that the surface of the lining is clean and smooth, without protrusions, depressions or residual mortar.

2. Surface smoothing: For the uneven surface, use a trowel to smooth it with a small amount of mortar. The smoothing should be light and uniform, and the thickness of the mortar layer should not exceed 2mm to avoid affecting the thickness of the lining and the bonding strength. For the ladle mouth and other key parts, the surface should be smoothed to be flush with the edge of the ladle to ensure the sealing performance when the ladle is used.

3. Defect treatment: Check the surface of the lining for defects such as cracks, voids and missing mortar. If cracks are found (width less than 1mm), they can be filled with mortar; if cracks are larger than 1mm or there are voids, the defective part should be chiseled out, and then re-masoned and joint filled. It is strictly prohibited to leave defects, which may lead to the erosion of steel melt and slag and damage the lining.

3.5 Post-installation Curing: Ensure the Strength and Stability of the Lining

Post-installation curing is the key to the ladle silica refractory mortar to obtain design strength and improve durability. Improper curing will lead to cracking, peeling and insufficient strength of the mortar, which will seriously affect the service life of the lining. The curing should follow the principle of "gradual moisturizing and slow curing", and strictly control the curing time and environment.

1. Initial curing: After the installation is completed, the ladle should be placed in a dry, ventilated and constant temperature environment (15 ~ 25℃) for initial curing. The initial curing time is 24 ~ 36 hours, during which the surface of the lining should be kept moist (but not waterlogged). It can be covered with plastic film or wet sacks to prevent rapid water loss and cracking. During the initial curing period, it is strictly prohibited to touch, collide or apply external force to the lining, so as to avoid damage to the mortar and bricks.

2. Moisturizing curing: After the initial curing, enter the moisturizing curing stage. The moisturizing curing time is not less than 7 days. During the curing period, spray water on the surface of the lining regularly (2 ~ 3 times a day) to keep the surface moist and ensure the sufficient hydration reaction of the mortar. The water used for spraying should be the same as the mixing water, clean and neutral. In winter construction, the moisturizing curing should be carried out in a warm shed to avoid freezing of the mortar; in summer construction, increase the spraying frequency to avoid rapid water loss.

3. Curing completion judgment: After the moisturizing curing is completed, check the strength of the mortar. The surface of the mortar should be hard, not easy to scratch, and there is no cracking or peeling. If the strength is insufficient, extend the curing time by 2 ~ 3 days until the strength meets the requirements. After the curing is completed, the ladle cannot be put into use immediately, and it needs to be baked according to the specified heating curve to remove the residual moisture in the mortar, which is an indispensable step before the formal use of the ladle.