The construction of chimneys , industrial stoves, fireplaces and other stone structures operating under high temperatures occurs using special materials. The use of ordinary ceramic or silicate stone in such structures is unacceptable, since there is a possibility of its destruction. Specialists use refractory bricks, the laying of which occurs with the use of the same heat-resistant solutions. The heat resistance of the material is achieved through firing and the use of special components in the production of stone.
Specifications
Refractory brick characteristics are distinguished from ordinary artificial ceramic or silicate stone. White clay acts as an integral part of the material, and the properties and types of bricks depend on impurities. However, they all have one category - refractories, that is, the ability to maintain their original characteristics when exposed to high temperatures that exceed 1580 degrees.
They are mainly used in industry, therefore high demands are placed on the production of refractories. Since any failure to operate such materials is fraught with large losses, not only temporary, but also financial. The main thing is that they provide security. Refractory brick is a fire insulating material.
General characteristics of fire-resistant artificial stones:
- Low thermal conductivity - the ability to maintain heat inside thermal units.
- Heat resistance - maintaining the strength of a brick when exposed to temperatures above 1580 degrees.
- Thermal inertia is the ability of a refractory material to cool slowly and heat up quickly.
- Heat capacity - a characteristic that ensures the accumulation of heat by a brick for further return.
- Chemical resistance to hot gases, slag, metal.
- The constancy of the volume, that is, the characteristic of refractory stones, does not shrink or grow in the range from 0.5% to 1%.
Application
Refractory brick, whose characteristics are different from ordinary masonry materials, has found its application in the construction of thermal units. In the metallurgical industry, for the melting of iron, nickel, copper, a temperature above 1500 degrees is necessary, therefore, furnaces in such a production are laid exclusively out of dolomite, dinas, and chromomagnesite bricks. Dinas stone is used for arches and lining of furnaces working with acidic substances. It expands at a temperature, but the magnesite refractory shrinks, so the arch using the latter can collapse. That is, each type of this category of brick has different properties and uses.
In the nonmetallurgical industry, refractory stone is used for the laying of chemical production equipment, communal boiler rooms, and coke kilns; units of glassworks.
Kinds
Refractory bricks come in four designs. The carbon type is made from coal tar with the addition of coke / anthracite powder. Such material is heat-resistant and slag-resistant. Typically used in blast furnace designs. However, to protect it, another layer of chamotte products is laid out. Dinas (quartz) stone is made from quartz powder and milk of lime. The fire resistance of such a material is 1730 degrees, and bricks are used for laying equipment in contact with acidic environments.
Magnesite, chromite, chromium-magnesite brick is made of calcined minerals. There are also carborundum and graphite products. Refractoriness of such species is from 1500 to 2000 degrees.
The alumina species is a material popular in industry - fireclay refractory brick. It contains more than 30% aluminum oxide (alumina) and the obligatory presence of special clay that is resistant to temperatures. Refractoriness - up to 1400 degrees.
Chemical classification
Depending on the composition of the main components, artificial stones can be divided into 3 groups: neutral, basic and acidic.
The acidic group of stone materials includes dinas and quartz clay. They interact without damage to acidic environments.
The basic refractories made of dolomite, magnesite, chromomagnesite contact the alkaline medium without problems. They are used for laying thermal units that require a sharp change in temperature in their work.
The neutral group for chemical compatibility includes chamotte refractory brick , carbon and graphite stone material. They are resistant to both alkaline and acidic environments.
Product Dimensions
It is impossible to combine all types of refractory bricks under one universal size. Each type of product has its own GOST, according to the requirements of which building materials are manufactured and where its main parameters are determined. Plus, the dimensions of the refractory brick depend on the shape, which is not always rectangular. This is due to the complex design of the thermal unit, requiring arches, vaults.
For example, the sizes of rectangular single products begin with 230x65x65 mm and end with parameters of 345x150x75 mm. All sizes of rectangular, wedge-shaped, suspended and other refractory products can be found in GOST 8691-73.
Marking
To answer the question of which to purchase refractory brick for the furnace, the price of which directly depends on the indicators of the material, it is necessary to know the basic marking of the product. Each block has a legend. The first letter indicates the name and type of product. So, if the marking is the letter "W", then this refractory belongs to the group of fireclay stones; “D” - dinas, “M” - mullite.
The second letter defines the maximum temperature of application of the material. Example for fireclay stones:
- SHA, SHAK - 1400 degrees.
- SB - 1350 degrees.
- SHUS, SHV - 1250 degrees.
- PB (semi-sour type) - 1350 degrees.
- PV - 1250 degrees.
The dimensions of the refractory brick are identified by the number preceded by the first two letters of the product brand. For example, the -5 refractory has parameters 23011465 mm, and -8 - 25012465. -22 characterizes the product in the shape of a wedge (trapezoid), the dimensions of this material are 230x114x65x55 mm. After the numbers in the marking, letters follow, which are the abbreviation of the manufacturer.
Cost
For the construction of fireplaces, barbecue, stoves, fire brick is used. The price of the material depends on the brand, size, design features and manufacturer. To compare prices for October 2015 in Ukraine and Russia, 4 types of the popular fireclay brick were chosen. When ordering a pallet, there are 350-360 pieces of brick. The price is for 1 pc.
- The rectangular shape of the product SHA-5 in Russia is estimated at 39.9 rubles.
- Similar to the previous refractory, SHA-8, characterized by slightly larger sizes, costs 47.9 rubles.
- SHA-22 (end wedge): the price in Russia is 49 rubles.
- SHA-45 (end wedge): the cost of the product in Russia is 41.2 rubles.
How to choose refractory bricks for the furnace?
In the construction of furnace devices, you can use red brick of normal firing, the standard dimensions of which are 250x120x65 mm. It should have clear edges, without chips, smooth edges and right angles. Otherwise, the masonry will be fragile. When breaking, the brick must have a homogeneous structure, that is, be inside without cracks, voids and interlayers.
Zheleznyak - a type of burnt brick can only be used for the construction of furnace foundations, since it is difficult to bind to the solution. Unburnt (scarlet) artificial stone, silicate, perforated and hollow bricks are not allowed to be used for laying furnaces and chimneys.
Refractory brick for the furnace, the price of which is several times higher than red ceramic stone, is necessary for lining thermal units. That is, to create a protective shell, a refractory is used, which surround the furnace. Due to this, the heat flow created inside does not destroy the main walls of the furnace.
Solutions
Refractory bricks for the furnace should be laid in the construction using a homogeneous solution that would firmly fasten the masonry and harden in a timely manner. For household stoves, a clay solution is used, which is prepared, depending on the clay content, with the addition of sand in the proportions 1: 1 or 1: 2. A prepared solution is considered to be suitable if the ball rolled from it does not crack along the contour when dried, and does not crumble when dropped onto the floor. If there is an excess of sand, then the ball falls apart, cracks gives the presence of a large proportion of clay in the solution.
When laying industrial equipment, the refractory brick is bonded to each other with the help of mortars - these are lime mortars intended for bonding refractory products.
For the laying of furnace foundations, it is recommended to prepare lime solutions in a ratio of 1: 2 - 1: 4. Cement mixtures are used to build the foundations of thermal aggregates that are affected by water, such as groundwater.
Masonry Category
During the construction and repair of thermal units, the laying of refractory bricks takes place according to the following requirements, which determine its category:
- The maximum thickness of the joints from 0.5 to 1 mm corresponds to a particularly thorough masonry of the 1st category.
- Joints 1-2 mm in size between bricks belong to 2 categories.
- Standard (ordinary) masonry is characterized by a thickness of joints up to 3 mm.
- The presence of a solution between bricks over 3 mm corresponds to a simple refractory masonry.
Classes, brands of refractories, masonry category - all this information should be spelled out in the working documentation. If there is none, then the thickness of the seams for different structural elements is determined based on special tables.