What Are the Different Types of Smelting Furnaces?

Melting furnace refers to equipment that melts metal ingots and some waste metals and adds necessary alloy components, and then slags and refining to smelt them into the required alloy.

1. Classification by heating energy

According to different heating energy sources, melting furnaces can be divided into the following two types:

(1) Fuel heating (including

The melting furnace should try to meet the following basic requirements:

The melting speed should be fast;

In order to ensure the quality of ingots of metal alloys and prolong the service life of the melting furnace as much as possible, all preparations for the melting furnace must be done in the actual production process, including furnace loading, oven, washing, cleaning, stirring, slag removal And refining operations.

1. Furnace loading

When smelting, the order and method of charging materials are related to the melting time, metal burnout, energy consumption, and also affect the quality of the melt and the service life of the furnace. The principles of loading furnaces are as follows:

(1) The order of furnace loading should be reasonable, and the melting speed of the materials should be considered according to the nature and status of the charging materials;

(2) Load small or thin scraps first, aluminum ingots and large pieces in the middle, and finally intermediate alloys;

(3) The intermediate alloy with low melting point and easily oxidized is installed in the lower layer, and the intermediate alloy with high melting point is installed on the top. The high temperature in the upper part of the furnace is conducive to full melting and diffusion, making the intermediate alloy uniformly distributed, and good for composition control;

(4) The charged material is evenly distributed in the molten pool, and the melting speed is consistent, to prevent overheating of the metal caused by partial weight;

(5) The furnace charge should be fed into the furnace as soon as possible, and multiple additions will increase the melt intake;

(6) When charging the electric furnace, pay attention to the safe distance between the highest point of the furnace material and the top heater to prevent electric shock and damage to heating facilities. If necessary, power off to operate.

2. Oven

For new or small or medium repaired furnaces, an oven is required before production and use in order to remove moisture from the furnace. Different furnace types use different oven systems. Pay attention to the following points in general ovens:

(1) Confirm whether the furnace door, chain and lifting operation system are intact;

(2) Check whether there are leaks in all parts of the natural gas pipeline, such as welding points, interfaces, valves, combustion air, and bleed valves. If there is a leak, handle it immediately. After processing, confirm again that there is no abnormality. Carry out ignition operations;

(3) Establish and fill in the file tracking record of the start-up furnace;

(4) Operate strictly in accordance with the curve established by the oven and the oven system;

(5) Pay attention to observe the temperature change of the furnace bottom, furnace cavity and side wall and compare it with the heating curve;

(6) It is forbidden to operate the fire for a short period of time to heat up and rapidly cool down.

3. Wash the furnace

The purpose of cleaning the furnace is to remove the metal and slag remaining in the molten pool outside the furnace, so as not to contaminate another alloy and ensure the chemical composition of the newly mixed gold. For newly-used furnaces (new, intermediate and overhaul), a large amount of non-metallic impurities are removed by washing the furnace. For furnaces that have been stopped for a long time, whether to perform cleaning is determined according to the cleanliness of the furnace and the grade of alloy to be produced. When the alloy elements of the previous furnace are impurities of the latter furnace, the furnace must be washed. The alloys with high impurities are converted into higher purity Furnace cleaning is required for alloys.

Furnace washing material principle: When producing high-purity or special alloy conversion, high-purity primary aluminum or aluminum ingot must be used. When a new furnace is opened or general alloy conversion, low-grade or first-grade waste can be used. After washing the furnace, the furnace charge must be completely dried. In order to ensure the effect of the washing, the stirring operation must be carried out in conjunction with the washing. Principles for the material used for furnace washing: When the purity of the commercial quotient or the speed of the special pot is fast, you must use pure original anchors or anchors. When converting furnaces or general alloys, low-grade or first-grade waste can be used. The furnace charge must be completely dried after the furnace, and the stirring operation must be coordinated when washing the furnace to ensure the effect of the furnace washing.

4. Clean the furnace

The furnace cleaning is the process of removing the residual slag in the furnace completely outside the furnace to reduce the chance of the melt being polluted by non-metallic inclusions and maintaining the original volume of the furnace. According to the specific conditions of the production process and equipment, different cleaning methods and cycles can be used. To clear the furnace:

(1) The furnace type of continuous production of ordinary raw aluminum liquid is cleaned once per shift, and thoroughly cleaned once every 5 to 15 times;

(2) When replacing the alloy variety, the furnace is generally cleaned thoroughly;

(3) When cleaning the furnace, in order to effectively remove the residue, the slag cleaner should be evenly sprayed into the furnace before the furnace is cleaned, and the temperature should be raised to about 800 ° C. Clean up thoroughly.

5.Slag picking and stirring

Purpose and function of stirring and slagging:

(1) In order to prevent overheating loss of the melt during the melting process, especially when the gas furnace is smelted, the furnace temperature rises quickly, and local overheating is easy to occur. Stirring can reduce the phenomenon of local overheating.

(2) When the charge is melted, necessary stirring should be performed to uniformly increase the temperature in the molten pool, and it is also conducive to rapid melting.

(3) When preparing alloys, stirring operations must be performed to ensure uniform distribution and dissolution of the alloy auxiliary materials and reduce segregation defects of chemical elements.

(4) Before sampling, after adjusting the chemical composition, stirring should be performed. The purpose is to make the alloy composition uniformly distributed and the melt temperature tend to be consistent. Some denser metal elements are easy to precipitate. In addition, the addition of metal elements cannot be uniform, resulting in local or regional unevenness in the melt, and incomplete stirring, which is likely to cause uneven melt exchange elements.

(5) Stirring is even more important when performing secondary ingredient adjustment. Before picking up the slag, the powdery solvent should be evenly sprinkled on the melt to effectively separate the slag from the metal, which is good for picking up slag, which can bring out less metal and reduce metal loss. The slag picking must be smooth to prevent the slag from being drawn into the melt. The slag picking must be thorough. The presence of scum will increase the gas content of the melt and pollute the metal.

Slag removal and stirring operations are two important processes in the smelting process. When the charge is fully melted in the melting furnace and the melt temperature reaches the melting temperature, stirring and slag scraping operations can be performed, and a large amount of scum on the surface of the melt is scraped out.

6. Refining

Refining is a process and operation process that removes gas, inclusions and harmful elements from the melt to obtain high-quality aluminum liquid, which is called refining, and can also be called purification. Refining methods are generally divided into: (1) in-furnace refining and on-line refining; (2) solvent refining and inert gas refining; and (3) solvent and inert gas refining. ^[3]

1. Before opening the furnace, check whether the electrical equipment, water cooling system, copper tube of the sensor are intact, otherwise it is forbidden to open the furnace.

2. Furnace melting loss should be repaired in time if it exceeds the regulations. Smelting is strictly prohibited in crucibles with excessive melting.

3. Special persons shall be responsible for power transmission and furnace opening. It is strictly forbidden to touch the sensors and cables after power transmission. Persons on duty are not allowed to leave the post without authorization. Pay attention to the external conditions of the sensor and the crucible.

4. When charging, check whether there is any flammable and explosive hazardous materials in the charge. If it should be removed in time, it is strictly forbidden to add cold and wet materials directly to the molten steel. After the molten liquid is filled to the top, it is strictly prohibited to add large materials. Just in case it gets covered.

5. It is strictly forbidden to mix iron filings and iron oxides when filling furnace and crucible. The crucible must be compact.

6. The pouring site and the pit in front of the furnace should be free of obstacles and water, so as to prevent molten steel from exploding on the ground.

7. The molten steel is not allowed to be too full. When pouring by hand, the two should cooperate with each other. They should walk stably, and no emergency stop is allowed. After pouring, the steel should be poured into the designated place.

8. The intermediate frequency generator room should be kept clean. It is strictly forbidden to bring flammable and explosive items and other sundries into the room. Smoking is prohibited in the room.

The main characteristics of the smelting furnace are: light equipment, fast heating speed, high efficiency; special power saving, electricity consumption under the same load is 60% less than that of the tube high frequency machine; it has a variety of protection functions such as overcurrent, overvoltage, overheating, and easy operation , Easy to install, suitable for all kinds of occasions that need to heat the metal. The characteristics of the melting furnace are as follows:

(1) Simple operation process and reliable melting operation

(2) Uniform metal composition and good material control

(3) Small size, light weight, high efficiency and low power consumption

(4) The temperature around the furnace is low, there is less smoke and dust, and the working environment is good

(5) The pulse transformer is encapsulated with glue, completely isolated from the outside, high withstand voltage and low failure.

(6) Large control cabinet structure, good ventilation and heat dissipation effect in the control cabinet.

(7) Fast melting and heating, easy control of furnace temperature and high production efficiency

(8) High furnace utilization rate and convenient replacement of varieties

(9) The furnace body can be dumped electrically, so it is easy to come out, especially suitable for casting.

(10) The control cabinet adopts full digital circuit control, with low failure rate and easy adjustment.

(11) The plug-in board on the control board uses gold-plated parts, which have firm contact and long service life.

(12) The connecting parts of the control board adopt pluggable plug-ins, and it is very convenient to replace the control board.

(13) With protection for over-current, over-pressure, water shortage, etc., with double closed-loop interception and interception.

(14) All power devices should have more than twice the demand to ensure the long-term stability of the equipment.