Well blocks, also called pocket blocks, are the masonry of refractory bricks at the bottom of steel ladle, which is used to fix nozzle bricks. Well bricks are square shape, so is also called square bricks. Their main function of well blocks is to fix nozzle, makes the detachment and installment of nozzle bricks easier. During steel casting, well blocks are used to hold the bottom end of stopper. when casting is finished, well blocks will ensure stopper slide to nozzle along the cambered surface to stop steel liquid main stream. By material composition, well blocks can be divided into clay pocket block, high alumina pocket block and unburned high alumina pocket block.
In modern metallurgical process, air blowing smelting technique is adopted, steel ladle purging plug pocket blocks are an important functional component for this step, steel ladle purging plug pocket blocks should have the following characteristics:
1. High temperature erosion resistance
Refinery steel ladle requires very strict standards on smelting temperature and time, the max. temperature can reach to more than 1750℃. During refinery process, molten slag alkalinity has great influence on refractory materials’ service life. Steel ladle refinery slag’s alkalinity varies between 0.6~0.4, so refractory material will suffer the erosion of acid slag and basic slag which have high permeability at high temperature, and has a quick damage speed.
2. High temperature abrasion resistance
All kinds of steel ladle refinery methods all adopt compulsory stirring, which will cause severe high temperature abrasion to pocket bricks.
3. Spalling resistance
Because of intermittent operation, temperature fluctuation is very large, which easily generate thermal spalling and structural spalling, working condition is very harsh. So currently used steel ladle purging plug pocket bricks’ performance such as high temperature erosion resistance and spalling resistance should be improved.
Steel ladle purging plug can be divided into built-in type integral purging plug and externally fitted purging plug combination type. To prolong purging plug’s service life, enhance it’s safety coefficient and ensure no steel leaking and permeation, no matter for externally fitted purging plug or built-in purging plug, pocket bricks play and important role and should be carefully chosen.
Pocket bricks are mainly used for continuous casting tundish and matched with nozzle bricks. Pocket bricks have high etching resistance, won’t distort or crack when coupled with zirconia metering nozzle.