Это просто Вьюи блог
Персональный блог REFRACTORY — Это просто Вьюи блог
Персональный блог REFRACTORY — Это просто Вьюи блог
Fireclay refractory brick is the most widely used refractory brick. Fireclay refractory bricks are inferior to silica and basic refractories in resistance to slag. Dense and more aluminous bricks resist slag the best.
Fireclay refractory bricks contain 18–45 percent of alumina (Al2O3) and 50-80 percent of silica (SiO2) with minor proportion of other minerals. They are made from refractory clays and kaolinite by the addition of fireclay or, sometimes, nonplastic clay rocks and quartz. Calcined clay or grog is added to the brick mix to reduce the firing shrinkage and to give greater stability in applications. Fireclay refractory brick is a kind of acid refractories.
Fireclay refractory brick is resistant to high temperatures, having fusion points higher than 1,600 °C (2,910 °F). The fireclays are graded into super duty, high-duty, medium-duty, low-duty, and also semi-silica, depending upon their capacity to withstand high temperature before melting. The low duty fireclay can withstand temperatures between 1515 and 1615 °C (PCE 19 to28), intermediate duty fireclay up to 1650 °C (PCE 30), high duty fireclay up to 1700 °C (PCE 32) and super duty beyond 1775 °C (PCE 35).
Refractoriness and plasticity are the two main properties needed in fireclay for its suitability in the manufacture of refractory bricks. A good fireclay should have a high fusion point (greater than 1580 deg C) and good plasticity.
Fireclay refractory brick has great features: low thermal conductivity, good thermal insulation, high resistance to thermal shock, abrasion and chemical attack, easy operation and installation, broad usage or applications and cheapness, etc.
Fireclay refractory manufacturing involves five processes: raw material processing, forming, drying, firing and final processing. The variety of clays and manufacturing techniques allows the production of numerous brick types appropriate to particular applications.
Fireclay refractory brick is extensively used in almost all places of heat generation, like boiler furnaces, glass melting furnaces, chimney linings, pottery kilns, blast furnaces, and reheating furnaces.
A fire brick is a block of ceramic material that can withstand high temperatures and is used to line furnaces, kilns, fireboxes, and fireplaces. For example, they use it to surround pipes, conduits, etc. in walls as fire breaks. There are two types of fire bricks: hard fire bricks and soft fire bricks.
Hard fire bricks are very dense, hard and durable but not great for insulating. While insulating firebricks can be easily cut with any kind of saw, hard fire bricks require special equipment, like a tile cutting saw, to cut. Design your kiln to take full advantage of available shapes, and when possible to minimize the amount of hard bricks you have to cut.
They are used for their structural qualities. Hard fire bricks are used on the inside of things like kilns because they absorb and conduct heat easily, which allows for the high temperatures needed in cooking and firing. They can be often used as the main building component of large kilns, chimneys, fireboxes and burner ports—anywhere around direct flame.
Soft fire bricks are soft and light in weight. They are made from a refractory clay body containing combustible materials. They can be easily cut by handheld hack saw or any other hand tool like chisel or even drill bit. This kind of firebrick has high porosity and excellent insulating properties. When fired, the materials burn out leaving a sponge like matrix of air pockets, which serve to provide insulating qualities to the brick. Soft firebricks absorb about half the energy as hard firebricks during a firing.
Soft fire bricks range from 2000°F to 3300°F and are used as the brick of choice for constructing electric kilns or as insulating liners in reduction kilns. Soft fire bricks are used on the outside of kilns because their very low thermal conductivity allows them to insulate and keep the heat inside the kiln. Soft fire bricks can also be used as a base for small scale soldering and precious metal clay firing with hand-held soldering irons and blowtorches. In this case, the soft fire brick protects the hard surface beneath it from damage.
Refractory is a type of material which is designed for use in high heat environments such as kilns and furnaces. The refractory materials can be categorized into many types. When choosing refractory materials, it is not only the problem of the best but also the right.
The primarily important requirement of refractory brick is that it can withstand very high temperatures without failing. It also needs to have low thermal conductivity, which is designed to make operating environments safer and more efficient. Furthermore, refractory brick can withstand impact from objects inside a high heat environment, and it can contain minor explosions which may occur during the heating process.
The most important factors to consider are the area of application and the operating environment. Selecting materials should always be based on properties and specifications suitable for the specific application and operating conditions.
First identify the area of application. Refractories can be used for a wide variety of different applications. Using refractory materials which are not right for the specific application can be dangerous. The refractory materials may fail, cracking, exploding, or developing other problems during use which could pose a threat to safety in addition to fouling a project.
If the refractory material is destined for heating or cooking, you may choose a normal refractory such as the fire brick. This not only heats up quickly, but also withstands many duty cycles of heating and cooling without breaking.
Some applications may require special refractory materials. Zircon is used when the material must withstand extremely high temperatures. Silicon carbide and carbon are two other refractory materials used in some very severe temperature conditions, but they cannot be used in contact with oxygen, as they will oxidize and burn.
Then consider the operating environment, the thermal environment and the chemical environment. Each application is going to require a different type of refractory based on the temperatures, likelihood of chemical corrosion and other issues that need to be taken into consideration. There are three general, acidic refractories, neutral refractories, and basic refractories. Be sure to select the corresponding chemical properties of refractories, otherwise chemical changes occur at high temperatures. Acid refractories are used in areas where slag and atmosphere are acidic. Neutral refractories are used in areas where slags and atmosphere are either acidic or basic. Basic refractories are used on areas where slags and atmosphere are basic.
Choosing the right refractory materials is not a simple thing. Besides of the application and operating environment, there are still many other factors to consider, such as the service life and costs.
Самые популярные посты