Production Process of Ladle Silica Refractory Mortar

The production of ladle silica refractory mortar is a refined and standardized system engineering, which requires strict control from raw material selection to finished product delivery to ensure that the product performance meets international standards and actual application needs. The specific production process is divided into three stages: pre-production preparation, core production operation and finished product inspection and control.

2.1 Pre-production Preparation: Lay a Solid Foundation

Pre-production preparation is the premise to ensure the quality of ladle silica refractory mortar, focusing on three aspects: raw material control, equipment commissioning and formula confirmation, to achieve "qualified raw materials, intact equipment and accurate formula".

2.1.1 Raw Material Selection and Pretreatment

The quality of raw materials directly determines the final performance of ladle silica refractory mortar. It is necessary to strictly screen core raw materials and auxiliary raw materials, and do a good job in pretreatment to eliminate unqualified raw materials from entering the production link.

1. Core raw materials: The core raw material is silica refractory powder, which is mainly made of high-purity silica sand or silica refractory clinker (SiO₂ content ≥ 96%), with a particle size of ≤ 1mm, and some even as fine as ≤ 0.5mm to ensure good fluidity and bonding performance of the mortar. The silica powder should be selected with stable chemical composition, low impurity content (Fe₂O₃ content ≤ 0.5%), and good thermal stability to avoid decomposition and deformation at high temperatures. In addition, an appropriate amount of high-purity quartz powder (particle size ≤ 3μm) can be added to optimize the particle gradation and improve the compactness and strength of the mortar.

2. Auxiliary raw materials: Auxiliary raw materials include binders, plasticizers, water reducers and anti-cracking agents, which need to be accurately matched with core raw materials. Binder: Ceramic bonded silica mortar mainly uses plastic clay (Al₂O₃ content 20% ~ 30%) as the binder, with an addition ratio of 5% ~ 12%, which plays a role in bonding and plasticizing, ensuring the initial strength and construction performance of the mortar; chemical bonded silica mortar can use sodium silicate or phosphate as the binder, with an addition ratio of 3% ~ 8%, which can achieve rapid hardening at room temperature. Plasticizer: Add an appropriate amount of cellulose ether (addition ratio 0.05% ~ 0.2%) to improve the plasticity and water retention of the mortar, making it easier to construct and avoid cracking caused by rapid water loss. Water reducer: Select high-efficiency polycarboxylate water reducer (addition ratio 0.1% ~ 0.8%) to reduce the amount of mixing water, improve the fluidity and compactness of the mortar, and avoid strength reduction caused by excessive water.

3. Raw material pretreatment: All raw materials must pass sampling inspection after entering the factory, verify the certificate of conformity and test report, and unqualified raw materials are strictly prohibited from entering the factory; Silica powder and quartz powder need to be dried to remove moisture (moisture content ≤ 0.3%) to prevent agglomeration and segregation during production; The granular raw materials need to be sieved to remove impurities, sundries and unqualified particle size particles to ensure that the particle gradation meets the formula requirements; The powder raw materials should be stored in a sealed manner to prevent moisture and agglomeration, and handled with care during transportation to avoid mixing with iron rust, sand and other impurities that affect product performance.

2.1.2 Equipment Commissioning and Site Preparation

1. Equipment commissioning: The main production equipment includes crushing equipment, sieving equipment, forced mixer, metering equipment and packaging equipment, which need to be fully commissioned in advance to ensure normal operation. The forced mixer should be thoroughly cleaned to remove residual old materials and sundries in the machine; when changing the raw material ratio or product model, the mixer, feeding hopper and weighing container should be fully cleaned to prevent cross-contamination of different raw materials. The metering equipment (electronic scale, batching scale) should be calibrated accurately, with an error controlled within ±1%, to ensure the accuracy of raw material ratio. The crushing and sieving equipment should check the integrity of blades and screens to ensure that the crushing particle size and sieving effect meet the standards. The packaging equipment should adjust the sealing performance of the seal to avoid moisture and leakage of finished products, and 1-2 key equipment should be prepared for standby to deal with sudden failures and avoid production interruption.

2. Site preparation: The production area should be dry, ventilated and clean, with rainproof and moisture-proof facilities to avoid moisture of raw materials and finished products; The raw material storage area should be stacked separately according to variety, particle size and specification, marked clearly, placed on a raised platform (distance from the ground ≥ 10cm), and far away from humid environment and water sources. The production area is divided into raw material area, pretreatment area, mixing area and finished product area to ensure smooth process and avoid cross-contamination. At the same time, do a good job in safety protection measures, equip with fire-fighting equipment and dust-proof equipment, and ensure the safety of operators.

2.1.3 Formula Confirmation and Optimization

According to the ladle use scenario (ladle wall, ladle bottom, ladle mouth) and performance requirements, confirm the production formula and optimize the raw material ratio to ensure that the product is suitable for actual use needs. For example, the ladle wall needs mortar with good thermal shock resistance and low shrinkage, which can adjust the plastic clay content to 8% and the quartz powder content to 5% to improve the bonding strength and thermal stability; the ladle mouth needs mortar with strong erosion resistance, which can appropriately increase the silica powder content and add an appropriate amount of anti-erosion admixture to enhance the resistance to steel slag erosion. After confirming the formula, small-batch trial production should be carried out to test the physical and chemical properties such as bonding strength, refractoriness and thermal shock resistance of the product, and mass production can be carried out only after passing the test.

2.2 Core Production Operations: Precise Control of Every Detail

The core production links of ladle silica refractory mortar include batching, mixing, forming (packaging), curing and drying. Each link must strictly follow the operation specifications and accurately control the parameters to ensure stable product quality.

2.2.1 Batching: Accurate Measurement to Avoid Ratio Deviation

Batching is the core link of production, which directly affects the consistency of product performance. It is necessary to accurately measure each raw material in strict accordance with the confirmed formula, and it is strictly prohibited to arbitrarily increase or decrease the amount of raw materials. Operators must receive professional training, be familiar with the formula requirements and the operation method of metering equipment. When batching, follow the principle of "first coarse then fine, first dry then wet": first weigh the coarse-grained silica powder, then the fine-grained quartz powder, and finally the binder, plasticizer, water reducer and other auxiliary raw materials. Before batching each batch, calibrate the metering equipment; after batching, check the amount of each raw material one by one and make records to ensure that the batching of each batch is accurate and consistent, and the error is within the allowable range. For micro-additives and ultra-fine powder, pre-mix them evenly in advance to avoid uneven dispersion caused by direct addition, which affects product performance.

2.2.2 Mixing: Uniform Stirring to Improve Compactness

The uniformity of mixing is the key to ensuring the uniform performance of ladle silica refractory mortar. A forced mixer must be used, and a gravity mixer is strictly prohibited (uneven mixing is likely to cause raw material segregation and agglomeration). The mixing process strictly follows the standard process of "first dry mixing then wet mixing", and the specific operation is as follows:

1. Dry mixing stage: Pour all the weighed dry materials (silica powder, quartz powder, binder, plasticizer, water reducer) into the forced mixer, start the mixing equipment, and dry mix for 2-3 minutes to ensure that the dry materials are evenly mixed, free of agglomeration and impurities, and the auxiliary raw materials are evenly dispersed in the core raw materials, laying a foundation for subsequent wet mixing. Before mixing each batch, check whether there are residual materials in the mixer to avoid polluting new materials; when changing the formula or raw material variety, thoroughly clean the mixer to ensure no residue.

2. Wet mixing stage: After dry mixing evenly, slowly add 80% of the preset water (the amount of water added must strictly follow the formula requirements, generally 6% ~ 8%, using pure drinking water with pH value 7 ~ 7.5), add water while stirring. After stirring for 1-2 minutes, add the remaining 20% of water as appropriate according to the consistency of the material, and continue wet mixing for more than 4 minutes. The total mixing time is not less than 6 minutes, until the material is uniform, the surface is pulpy, free of agglomeration, segregation and dry material particles, and the fluidity meets the production requirements (holding into a ball by hand, scattering when released). During wet mixing, avoid excessive water addition (which will reduce product strength and erosion resistance) or insufficient water addition (which will cause uneven mixing and difficult construction), and strictly follow the principle of "rather less than more", which can be fine-tuned according to the actual situation.

3. Mixing precautions: Arrange special personnel to observe the material state during mixing, and adjust the mixing time and water addition in time; the mixed material must complete the subsequent forming or packaging within the specified time (20 ~ 30 minutes), and the initial set and agglomerated material are strictly prohibited to be used and must be cleaned and discarded in time; after mixing each batch, clean the mixer to avoid residual materials agglomerating and affecting the production quality of the next batch.

2.2.3 Forming (Packaging): Standard Operation to Ensure Quality

Ladle silica refractory mortar is mainly supplied in bulk, and the forming link is mainly packaging. After uniform mixing, the material is directly sent to the packaging equipment and packaged with moisture-proof packaging bags. The packaging specification is adjusted according to customer needs (generally 25kg/bag, 50kg/bag). During packaging, ensure that the seal is tight to avoid moisture and leakage of the material. After packaging, mark the product name (ladle silica refractory mortar), specification, formula, production date, shelf life and manufacturer information on the packaging bag to facilitate subsequent storage, transportation and use. After packaging each batch, randomly sample to check the packaging tightness and material uniformity, and re-package or handle unqualified products.

For special-shaped ladle parts, the mortar can be made into prefabricated blocks by pouring into molds. The operation points are as follows: pour the mixed material into the preset mold (the mold is made of steel plate, and the surface is coated with release agent to facilitate demoulding), vibrate with a vibration table for 20 ~ 30 seconds until the surface of the material is pulpy, no bubbles emerge and no longer sink, ensuring dense forming without defects such as voids and honeycombs. After vibration, place the mold in a flat and ventilated area for initial curing to ensure stable forming of the prefabricated block and avoid deformation and cracking.

2.2.4 Curing and Drying: Scientific Maintenance to Improve Strength

Curing and drying are the key to ladle silica refractory mortar to obtain design strength and improve durability. Scientific curing and drying measures must be taken according to the forming method and ambient temperature to avoid cracking and insufficient strength caused by improper curing.

1. Curing: The packaged bulk mortar should be stored in a dry, ventilated, rainproof and moisture-proof warehouse for curing for not less than 7 days. During the curing period, avoid moisture and extrusion to prevent material agglomeration and deterioration; regularly check the material state during the curing period, and timely handle problems such as agglomeration and moisture, which are strictly prohibited to be used for subsequent construction or sales. For prefabricated blocks, curing is divided into initial curing and moisture retention curing: initial curing is carried out in a normal temperature (15 ~ 25℃) and ventilated environment for 24 ~ 36 hours to make the prefabricated blocks initially set and have a certain strength; after demoulding, enter the moisture retention curing stage, cover the surface of the prefabricated blocks with plastic film or wet sacks to keep the surface moist and avoid cracking caused by rapid water loss. The moisture retention curing time is not less than 7 days.

2. Drying: After curing, the prefabricated blocks and some bulk mortar with special requirements need to be dried to remove free water and crystal water in the material, so as to avoid thermal stress caused by rapid evaporation of water at high temperatures when the product is put into use, leading to cracking and peeling. Drying must follow the principle of "gradual heating and slow heating", and strictly control the heating rate:

- Low temperature stage (room temperature ~ 150℃): The heating rate is controlled at 10 ~ 15℃/h, and kept for 2 ~ 3 hours to focus on removing free water on the material surface;

- Medium temperature stage (150 ~ 350℃): The heating rate is controlled at 15 ~ 20℃/h, and kept for 3 ~ 4 hours to remove crystal water inside the material;

- High temperature stage (350 ~ 600℃): The heating rate is controlled at 20 ~ 25℃/h, and kept for 4 ~ 6 hours to make the material fully sintered and improve strength and thermal stability;

- Cooling stage: After drying, slowly cool down to room temperature (cooling rate controlled at 15 ~ 20℃/h) to avoid cracking caused by rapid cooling. After drying, check the surface of the prefabricated blocks for cracks and chipping, and reprocess or scrap unqualified products; the dried bulk mortar should be cooled to room temperature before packaging and storage to avoid moisture and agglomeration caused by high-temperature packaging.

2.3 Finished Product Inspection and Factory Control: Strict Check to Ensure Qualification

Finished product inspection is the last quality line before the delivery of ladle silica refractory mortar. Comprehensive inspection should be carried out batch by batch to ensure that the physical and chemical properties and appearance quality of the product meet international standards and customer needs, and unqualified products are strictly prohibited from leaving the factory.

2.3.1 Finished Product Inspection Items and Standards

1. Physical and chemical performance inspection: Random sampling is carried out for each batch (sampling ratio not less than 3%), and the inspection items include bonding strength, refractoriness, thermal shock resistance, acid corrosion resistance, moisture content, etc., and the specific standards comply with international standards such as ASTM C199 and ISO 10081. For example, the bonding strength (after drying at 110℃) is not less than 2.5MPa, the refractoriness is not less than 1650℃±50℃, the thermal shock resistance (water cooling cycle at 1100℃) is not less than 8 times, and the moisture content is not more than 0.3%, ensuring that the product can adapt to the high-temperature and strong erosion working environment of the ladle.

2. Appearance quality inspection: Check the bulk mortar for agglomeration, impurities and moisture, and check whether the packaging is tight and the marks are complete; check the prefabricated blocks for flat surface, no cracks, no chipping, no voids, the dimensional deviation is controlled within ±2mm, and the shape meets the design requirements to avoid affecting construction and use effect due to appearance defects.

2.3.2 Factory Control Requirements

1. Only after passing the inspection can the product certificate and test report be issued, clearly indicating the product name, specification, formula, production date, shelf life, test results and other information, which are delivered together with the product;

2. The finished products should be stacked separately according to variety and specification, far away from humid and high-temperature environment, placed on a raised platform to avoid extrusion and moisture. The shelf life is controlled at 6 months (under normal dry storage conditions). For products exceeding the shelf life, re-inspection is required, and they can be sold and used only after passing the inspection;

3. During transportation, take moisture-proof, anti-extrusion and anti-damage measures to avoid moisture, agglomeration and damage of the product; the transport vehicle should be clean and dry, and it is strictly prohibited to mix with other sundries to ensure stable product quality;

4. Establish production and inspection files, record in detail the purchase of raw materials, batching, mixing, curing, drying, inspection, delivery and other information of each batch, and keep them for at least 1 year to facilitate subsequent quality traceability and timely handling of quality problems.