Influence of construction at low temperature in winter on properties of refractory castable for heating furnace
The heating furnace is an important thermal equipment used in the rolling mill to heat the billet, and mainly includes pusher type, walking beam type, walking bottom type, ring heating furnace and other furnace types. At present, in the construction process of heating furnace, refractory castable has the advantages of short construction period, good insulation effect, and high overall strength, so it is widely used in various parts of the furnace lining. During construction in winter, it is generally required that the mixing water temperature be controlled at 15~35℃, and the curing temperature should be strictly controlled above 5℃. In particular, the winter temperature in northern areas is basically below zero. The ambient temperature of some construction sites is too low, resulting in poor fluidity of the refractory castable and prolonged solidification time. If insulation measures are not taken, the refractory castable will be frozen and suffer heavy losses. Seriously affect the construction quality and construction schedule. Therefore, during the construction of refractory castables in winter, effective insulation measures must be taken to increase the construction environment temperature to above 5°C to ensure that the refractory castables are not damaged by freezing and the construction process can proceed smoothly.
The refractory castable sample block production and maintenance test were carried out under the ambient temperature of 5℃, and it was learned that the low-temperature pouring construction has a relatively large impact on the refractory castable. Combined with the practice of construction site technical guidance, the following impacts are summarized:
(1) For construction at low temperature, it is difficult to mix refractory castables evenly, which affects the forming of the material after construction.
(2) Construction at low temperature, during the mixing and discharging process of refractory castables, the fluidity becomes smaller and voids are easily formed during pouring.
(3) Construction under low temperature, the strength of refractory castable will be lower, it is easier to form a loose state after freezing, and it is easy to fall off and fall off when removing the mold.
(4) During construction at low temperature, the free water in the refractory castable will spall off the castable lining due to icing volume expansion.