1. Overview of Ceramic Welding Repair Technology
Welding technologies such as electric welding, gas welding, engineering plastic welding, etc. are all technologies that use electric energy or thermal energy to melt the solder and the workpiece to be welded together. Ceramic welding repair technology is also a welding technology like electric welding and gas welding, but it is a special welding technology. It uses a mixture of powdery refractory materials and powdery metal combustibles as solder, and uses oxygen as a carrier to pass the solder through a welding gun. Transported to the repair area, a violent oxidation and exothermic reaction occurs between the metal and oxygen in the hot atmosphere of the area to be repaired in the kiln, melting the solder to produce a ceramic adhesive that is deposited into the repair area of the base refractory material until it reaches the required required thickness. It is a method of repairing refractory materials in industrial kilns. Since this technology utilizes the exothermic reaction of oxidation between metal and oxygen, it is different from the general hydrocarbon combustion mechanism. It uses metal powder as combustible material and oxygen as a combustion accelerant. The high temperature of the area to be repaired causes the metal powder to burn and cause a thermal reaction. In addition, in order to prevent flammable materials from deflagrating in the welding gun, a small amount of nitrogen is added.
2. Welding filler ingredients
Glass kiln is composed of a variety of refractory materials, such as silica bricks, AZS bricks, magnesia bricks, corundum bricks, refractory clay bricks, etc. According to the welding mechanism, the composition of the solder should be the same or similar to that of the base material. Therefore, when selecting glass furnace welding repair materials, welding repair materials should be selected that have the same or similar composition as the refractory matrix composition of the glass furnace welding repair part. Now some ceramic welding repair technology engineering companies have developed siliceous, zirconium, magnesium and high-aluminum welding repair materials that can be used to repair silica bricks, AZS bricks, magnesia bricks and corundum bricks. The following takes silicon solder filler as an example to analyze the composition of the solder. Siliceous welding patch material is also an unshaped refractory gunning material, which is composed of dense refractory aggregate and binder with certain particle gradation. The aggregate is high-purity SiO2 containing tridymite and cristobalite as the main components: as the main raw material, its content accounts for more than 85% of the total welding patch. In addition, the welding patch also contains the following ingredients: 6% Al2O3, 2% Fe2O3, 1%-2.5% CaO, 0.1% Na2O, 0.4%-1% K2O. The added binding agent uses common inorganic salts such as silicate, phosphate, polyphosphate, etc., and the content of solid metal powder (such as aluminum) is between 2% and 4%. The characteristics of this welding patch material are dense structure and strong earthquake resistance. The heat released after the violent oxidation reaction between metal powder and oxygen (the temperature reaches more than 2000°C) causes it to melt rapidly. It is firmly bonded with the silica brick (base material) to form an overall dense structure with stable volume, and will not damage the repair structure due to swelling and cracking due to the transformation of SiO2 crystal form.
3. Composition and technical advantages of ceramic welding repair equipment
The welding repair equipment mainly consists of a welding gun, a mixer, an operation control panel, a cooling water pressure pump, and a high-pressure rubber pipe. Auxiliary equipment includes: leveling machine, refractory cutting saw, small hydraulic station, cooling equipment, etc. Working conditions requirements: pure oxygen above 0.4MPa, nitrogen 0.02MPa, water pressure 1MPa.
The use of ceramic welding repair technology has the following advantages: ① Using a special spray gun, it can reach parts that cannot be reached by traditional hot repair, such as corners inside the kiln. ②The impact on production during maintenance is very small and can sometimes be ignored. ③The labor intensity and risk of maintenance personnel are greatly reduced. ④ Ceramic welding repair can be used to repair the weak parts of the kiln when problems first arise to eliminate safety hazards.
4. Welding repair operation and control of process parameters
Ceramic welding repair technology is a maintenance method that has emerged in China in recent years to repair kilns without stopping production in a hot state. It has been widely used abroad. Foreign engineering experts have developed a set of mature operating methods and processes during the operation. During the actual construction, they are operated by experienced engineering and technical personnel. The control of the operating process parameters is particularly precise, and the personnel also have a clear division of labor. Perform their duties. Depending on the welding repair part and the composition of the solder, the mixer feeds the material at a certain speed to ensure the quality of the weld. During this process, oxygen serves as both a combustion accelerant and a carrier for transporting the solder. Whether the pressure and flow rate are stable will directly affect the welding quality and efficiency. If the pressure is too high and the flow rate of the welding repair material is too fast and it is difficult to completely melt, slag and pores will be formed in the welding repair area, and the bonding strength with the base metal is not enough. The quality of welding repair is poor; if the pressure is too low, the flow rate of welding repair material is too slow, and although the quality of the welding repair area is guaranteed, the efficiency is low. When repairing siliceous drums, the pure oxygen pressure is generally stable at 0.4MPa and the nitrogen pressure is stable at 0.02MPa. In this state, the welding speed can reach 30-50Kg/h. certainly. The process parameters can be adjusted at any time according to the different welding repair parts and the composition of the welding repair material.
5. Welding repair effect
In July 2002, large or small molten holes (also called rat holes) appeared on the tops of furnaces #1 and #2 of an electronic glass company in Henan, seriously affecting the safety of the furnaces. The ceramic welding repair technology of a foreign company was used for repairs and was successful. The following two pictures are before and after welding repair on the right side of furnace #2. Comparing the two photos, it is obvious that the eroded molten holes and large-area eroded areas have been smoothed by spraying after welding repairs, so that the structural strength of the big pile is greatly improved. After ceramic welding repairs, the company’s furnace #1 has been running for 7 years and 8 months, and furnace #2 has been running for 8 years and 1 month. The furnace age has been extended by 1 to 2 years. Ceramic welding repairs became a key factor in extending the life of the pool furnace, bringing significant economic benefits to the company.
6. Conclusion
Ceramic welding repair is a very effective method for the middle and later maintenance of glass tank furnaces. It can also be applied to other industrial furnaces. In foreign countries, ceramic welding repair technology has been widely used in hot repair of glass kilns and coke ovens without interrupting production. For manufacturers, the benefits of extending the production cycle of the kiln are considerable, while the cost of ceramic welding repairs to extend the production cycle is negligible. This is why this technology has gained popularity in China in recent years. The reason for the rise.
