The process design of lightweight and high strength castable for ladle insulation is as follows:
1. Selection of insulation materials
The traditional insulation layer is built with clay brick, which has complicated process, frequent maintenance, easy steel seepage, low service life and high cost. The technology of unshaped refractories is becoming more and more mature. The lightweight castable with high strength is widely used because of its low volume density, low thermal conductivity and high compressive strength. The castable aggregate is composed of drift beads, high alumina porous clinker and alumina hollow ball composite aggregate, which makes the castable have the properties of low volume density, low thermal conductivity, good thermal insulation, high refractoriness and high compressive strength, etc. With clay clinker powder and industrial aluminum oxide powder as powder, the mass fraction of Al2O3 in castable can reach 45% ~ 50%. Pure calcium aluminate cement as a binder, ensure not to reduce the mass fraction of Al2O3 under the previous problem, so that the casting molding has a higher strength. Adding appropriate amount of fused magnesia to maintain the volume stability of the products, reduce the cracking and peeling phenomenon in use, enhance the resistance to rapid cooling and rapid heat, so that the service life of the insulation layer is improved. The performance indexes of lightweight and high strength castable are shown in Table 1.
Table 1 Performance index of light and high strength castable
Performance index of light and high strength castable
2. Design of insulation layer thickness
The working layer thickness of ladle is 180mm, the minimum service thickness is 60mm, and the service life is not less than 25 times. Considering the insulation performance of the ladle and the service life of the working layer, the thickness of the insulation layer of the ladle wall is determined to be 80mm, and the thickness of the insulation layer at the bottom is determined to be 140mm.
3. Fabrication of tire mold
According to the designed size of the insulation layer and the size of the cladding to design the insulation layer mold. In order to facilitate the vibration of the castable, make the castable fill the whole insulation layer and facilitate demoulding, the mould is made into a split structure of upper and lower layers. The taper is the same as the cladding. The outer diameter of the lower die is 190mm smaller than the inner diameter of the cladding (the insulation layer is 10mm ~ 20mm), and the outer diameter of the upper die is 180mm smaller than the inner diameter of the cladding (the insulation layer is 10mm ~ 20mm). The welding of the mould steel plate should be smooth and smooth, and the inner support plate is provided to prevent the deformation of the mould. The welding hook on the support plate is easy to lift and transport.
4. Pouring construction of insulation layer
Of lightweight, high strength castable overall knot craft, its craft process in stages: each batch of castable in blender to fully mix, water content control in 10% ~ 15% (1) the package tie wall uniform coating a layer of the outer wall of the lower mold release agent after its release package and fixed good, mould and thermal barrier uniform clearance, and then blended castable injection mould and thermal barrier clearance, pay attention to not make the insulation peeling or involved in castable, reoccupy vibration rods will be castable even and dense; The bottom knot is finished. Put the upper mold in place and tie the knot in turn. (2) Natural drying for 24h to 48h, mold out, install the block brick and breathable brick mold, and then use the stirred castable to tie the insulation layer at the bottom. (3) Natural drying for 12h ~ 24h, mold out, and then natural curing for more than 72h, and finally baking.
5, the baking of the insulation layer
The moisture content of the insulation layer after casting is large, so it is necessary to discharge the moisture in the castable through baking to increase the strength of the insulation layer. In order to prevent the thermal insulation layer from bursting due to too fast heating rate, the baking is carried out in strict accordance with the heating rate and holding time stipulated by the process. The total baking time shall not be less than 15h. The baking shall be carried out according to the baking curve shown in Figure 1.