Select the working environment and refractories of soaking furnace
In addition to the high temperature flame and slag erosion, the mouth, wall and bottom of the soaking furnace also bear the impact of steel ingot and fixture. In addition to the roasting of the furnace and mobile furnace covers, the furnace and mobile furnace covers are also affected by temperature changes and mechanical vibration. Therefore, the soaking furnace should be constructed with refractory materials with high fire resistance, high mechanical strength, good slag resistance and good thermal shock resistance. The furnace lid and wall are usually made of clay bricks; The lower part of the furnace wall is made of silicon brick with good mechanical properties. Magnesium bricks are generally used in the bottom of the furnace to resist the erosion of alkaline slag. When the slag is not melted, the bottom of the furnace can also be made of high aluminum bricks. Two layers of aluminum bricks should be transferred between the magnesium bricks at the bottom of the furnace and the silicon bricks on the furnace wall.
In recent years, due to the development and wide application of amorphous refractory materials, refractory castables or refractory plastics have been used to replace refractory brick masonry in many parts of soaking furnace, with good results. Clay refractory castable NL can be used for hand-to-hand stove covers and wall parts. Phosphate refractory castable can be used in the lower part of the furnace wall, and magnesium refractory castable can be used in the bottom of the furnace, or the five brands specified in GB10695-89 "alkali refractory castable" can be selected.
The working environment of soaking furnace lining is :(1) long-term high temperature; (2) ingot wear and charging machine clamp collision; The lid is often opened and closed, and the lining is affected by heat and cold.
In the past, soaking furnaces were mainly made of clay bricks, high aluminum bricks and silicon bricks. Due to slag erosion, the working layer of the bottom of the furnace and the foot of the furnace wall is generally made of magnesia-chrome brick and magnesia-chrome brick. At present, amorphous refractories or precast blocks are mainly used in soaking furnaces. The amorphous refractory is mainly made of high aluminum mullite castable containing stainless steel fiber. High strength lightweight castable is used in the inner lining of the furnace cover.
In soaking furnace, light insulation castable and refractory fiber products are its development trend. In terms of furnace wall castables, there are more and more aluminum-silicon castables with low cement and ultra-low cement A2O3 of 50%-75%.
It is worth noting that the application of fiber spray coating in heat treatment furnace is worth noting, which plays a good role in convenient construction, heat preservation and maintenance, and is a development direction.
The function of the soaking furnace is to uniformly heat the ingot to the high temperature furnace at the rolling temperature. There are many kinds of soaking stoves. The soaking furnace consists of a stove, a wall, a bottom and a heat exchanger. The following is an introduction to the furnace refractory.
First, the stove cover.
The average hot furnace temperature is generally 1200-1300℃, and the working face of the furnace cover is as high as 135-1450℃. When the furnace is opened, the temperature drops below 300℃, the temperature changes suddenly and frequently, and the mechanical vibration is large. Therefore, the refractory lining of the furnace cover is often cracked and peeled, and sometimes washed away.
Generally, the furnace cover is made of clay bricks with good heat-resistant layer, small change of heavy burning line, high compressive strength and heat-resistant shock high aluminum bricks. Or monolithic cast phosphate refractory castable.
Second, the furnace wall.
The heavy load on the side wall of the soaking furnace is large, and it is often subjected to hard and worn ingot and clamp, vibration of moving furnace cover, and also affected by sudden temperature change of loading material. Silicon bricks or high aluminum bricks generally use silicon bricks with high load softening temperature. Large precast block masonry or monolithic casting can also be made of refractory castable.
Third, the bottom of the furnace.
The low temperature at the bottom of the furnace is basically equal to the soaking temperature of the ingot, about 1200-1300℃. The bottom of the furnace works in an oxidizing atmosphere, and the oxidized iron sheet generated on the surface of the ingot falls off and accumulates in the bottom of the furnace, sometimes with a thickness of more than 100-150mm, causing serious chemical erosion to the bottom of the furnace. When the slag is dry discharged, the bottom structure of the furnace bottom is: adiabatic fiber felt (or red brick), light sticky brick (or high strength diatomaceous earth brick), clay brick, magnesium brick. A layer of burnt powder is laid on the magnesia brick. When liquid slagging is used, the upper layer of the furnace bottom is magnesium refractory castable, and the lower layer is clay refractory castable.