Development of ZHT100 Type 1t Vacuum Consumable Arc Furnace

Vacuum ZHT100 Type 1t Vacuum Consumable Electric Arc Furnace Development Peng Changhu (Shaanxi Baoji Nonferrous Metals Processing Factory Design Institute, Baoji 721014, Shaanxi, China), This 1t vacuum consumable arc furnace designed and manufactured by us has been exported abroad. A successful test run and put into use a vacuum consumable EAF as a complex vacuum melting equipment, which is mainly used for melting ingots of refractory metals and certain rare metals. With the rapid development of the world economy, aviation, aerospace, In the petrochemical and nuclear industries, the use of rare metal products such as titanium and zirconium has become more and more widespread. As a result, there is more demand for the quality and production of rare metal products. Vacuum Consumed Arc Furnace is used as a melting rare metal ingot Equipment is also increasingly widely used. Abroad started to use self-consumed electric arc furnaces in the 1960s. Nowadays, this technology has developed rapidly. Its main new technologies include the use of an electrode automatic weighing system to continuously monitor the weight of the remaining electrodes during the smelting process. In this way, the arc is automatically controlled and the melting process is controlled by a computer. 3 The electrode is lifted and driven by hydraulic pressure, and the electrode can be adjusted in the XY direction. 4 The coaxial power supply structure is adopted. At present, the vacuum self-consumed electric arc furnace currently developed in China is mainly based on counterfeiting. Based on the advanced technology of similar equipments at home and abroad, we have designed and manufactured the ZHT100 type 1t vacuum consumable electric arc furnace. This electric arc furnace has some new features. 1 The new structure of differential speed-shifting, which drives the ball screw and the nut to realize the stepless speed change of the pole, adopts the new structure of coaxial power supply, auxiliary conductive and steel-copper composite as the conductive flange. 3 The hydraulic system adopts programmable controller to realize the sequential operation. 4 The lifting and lowering of the electrode rod is provided with manual and automatic double sets of controls to facilitate operation. 5 The computer detection system is adopted. The main operating parameters of the furnace can be displayed, recorded and printed. The cooling system sets up target flowmeters for each main waterway to monitor the flow of cooling water. In addition, there is a backwater overtemperature alarm for the electrode pole and the stern cooling waterway, and all the cooling water is recycled. 7 The overall structure adopts the structure of four-column primary and secondary work platforms. The electrode rods are lifted and rolled in the form of rollers and secondary guide columns. Currently, the furnace has passed various parameters of debugging in foreign countries to meet the design requirements and is now in use.

1 The main performance parameters of the device 1.1 Electrode rod diameter: Y smelting Decrease speed: 0~600mm/min Continuously adjustable 1.2 Melting power Total power: 1000kW Silicon controlled rectifier Melting current: 12kA Working voltage: 20 Empty voltage: 65V In part, a Z-12 1.3坩埚 size 1.4 consumable electrode size DC motor and a worm gear reducer are used to rotate the nut on the ball screw, and the lower transmission is placed on the active beam of the electrode rod assembly. In the above, the electrode rod is connected with the movable beam so that the difference between the screw nut and the ball screw on the ball screw realizes the difference 1Y 1876 mm 1.5 ingot size 1.6 vacuum degree 1.9 hydraulic system 1000 mm/min 1.10 cooling water, Compression Air System 2 Device Configuration The configuration of this device is shown in the figure below. It mainly consists of the following components: 1 Upper drive system and upper platform. 2 electrode rod assembly and lower transmission system. 3 furnace body and lower platform. 4 explosion-proof door 5 water jacket and mobile trolley 6 cooling water and air compression system 7 vacuum system and hydraulic system 8 power supply and electrical control system 9 optical system 1 water-cooled cable.

3 The working process of each part of the equipment moves to control the lowering speed of the electrode rod. In fact, we can control the descent speed of the electrode rod only by controlling the DC motor. Once the electrode rod needs to be quickly lowered, the AC machine stops. Once the electrode rod needs to rise quickly, the DC machine stops. The electrode rod assembly and the movable cross beam are suspended on the upper platform by a ball screw. The active cross beam is composed of four guide wheels and two guide columns on both sides of the movable cross beam to complete the guide of the movable cross beam. The upper part of the electrode rod is connected to one end of the flexible water-cooling cable by calculating the elevation position of the electrode, and the other end of the water-cooled cable is connected to the negative electrode of the conductive busbar. The lower part of the electrode rod is clamped by the pneumatic chuck and the auxiliary electrode. 1主传动 The auxiliary electrode is welded with the consumable electrode in a vacuum state before smelting, so that the consumable electrode is eventually clamped on the electrode rod, the electrode is lowered by melting down the consumable electrode 3. 1 main drive The upper part of the platform and the upper part of the platform are mainly suspended by the upper and lower transmission system, the electrode rod assembly and the four-way bearing on the upper platform, and the lMsh on the electrode rod assembly is provided with a cooling water jacket. The water jacket can meet three different specifications of the column. It is composed of upper and lower platforms. The input part is driven by a YD100L-4/2, 1430/2850r/min type two-speed AC motor directly connected to the ball screw through a worm gear reducer, so that the ball screw rotates. The ball screw passes through the radial thrust bearing. And push the 3.2-inch component and mobile trolley water-cooled copper crucible as the core of the vacuum melting, the metal is melted in the water-cooled crucible and melted, super refined and crystallized, thereby becoming the ingot of this equipment. The water-cooled bottomed crucible is used outside the crucible. In addition, an arc stabilizing coil is wound around the outer circumference of the inner water jacket so that the arc is stable during smelting and does not cause partial arc. At the same time, the molten pool is stirred by the magnetic field force generated by the coil, so that the grain refinement of the ingot is uniform. ,Increase the quality of the ingot 坩埚The cooling of the ingot is from the bottom up. For the different crucibles, three types of water conduits with the same diameter but different lengths are installed at the bottom of the crucible to suit different specifications of the crucible. A target flow meter and a thermocouple meter were installed to monitor the flow and temperature changes of the chilled return water. The components were connected to the mobile car. This car was used. The motor drives the crucible assembly and the moving trolley moves from the front of the furnace to the bottom of the furnace, and then uses the two hydraulic cylinders placed on the lower platform to lift or lower the crucible assembly and the moving trolley. 3.3 The round of the furnace and the lower platform mm (high) The cylinder structure has a dynamic seal on the furnace cover, two optical observation holes and one observation hole, and the whole furnace body is connected to the lower platform. The furnace body is a vacuum chamber containing a consumable electrode, and it passes through the dynamic seal and the electrode rod. Connected, and the following through the hydraulic cylinder connected to the crucible, the vacuum furnace in the middle of the furnace leaving the body of the device using a sandwich water jacket structure, its inner cylinder made of stainless steel, taking into account the strong current generated by the magnetic field The influence of smelting arc, so the positive current busbar smelting current connected to the upper part of the furnace, so that the current through the furnace and the electrode pole on the anode current parallel to each other, which constitutes the coaxiality of the current due to the furnace body The lower flange is to be connected with the flange of the copper gong. We use a steel-copper composite material for the lower flange of the furnace body. This way, on the one hand, the flange surface of the boring flange will not be scratched. On the other hand, high current can also be passed through. At the same time, two optical observation holes on the cover of the auxiliary conductive column are arranged around the lower flange of the furnace body. The optical observation system is mainly used to observe the change of the arc during the melting process in the optical system, and the observation hole is mainly used to observe the initial period of melting. In the case of arc starting, the platform supports the upper guide plate and the two guide posts of the electrode rod with four columns, and two hydraulic lifting cylinders are simultaneously fixed on the lower platform for lifting the crucible assembly.

3.4 Vacuum system The vacuum system is mainly used for degassing to prevent the metal from being oxidized during smelting. At the same time, the gas released from the electrodes during smelting is extracted together. The vacuum system of this equipment is also provided with a vacuum system for cold traps, dust removal and venting devices. Mainly consists of two K~600A oil diffusion pumps, two Z-1200A Roots pumps, three H-150 spool valves, and two 2X-30A rotary vane pumps. In actual operation, only one K-600A oil is used. Diffusion pump, a Z-1200A roots pump, two H-150 spool pumps and a 2X-30A rotary vane pump. The vacuum unit formed by these vacuum pumps can meet the work requirements, while the remaining one K- The 600A oil expands a set of 2X-30A rotary vane pumps as a spare set of vacuum units. It is connected in parallel with the aforementioned vacuum units and then connected to the furnace body. In normal operation, only one set of units is used and the other set is used as a backup. The operation of the vacuum system is divided into two types: manual and automatic. Vacuum system simulation tray and composite vacuum gauge are set on the vacuum console to monitor the vacuum degree of the equipment. The vacuum degree of the system is transmitted to the vacuum meter. The computer allows the computer to monitor, display and print out the vacuum of the system at any time. In addition, the vacuum valves used in the system adopt electromagnetic or pneumatic valves, which are convenient for automatic control.

3.5 Water Cooling System The cooling system of this equipment consists of two cooling water tanks and a cooling pump station. A cooling water tank provides cooling water for the furnace body pole, water cooling cable, and the other provides cooling water for each vacuum pump and power supply. In the system, target flowmeters are installed on the backwater paths of the pole poles and water-cooled cables, respectively, to monitor whether there are water flows in the respective return waterways, and a thermocouple meter is also installed on the cooling water circuit that is most important for cooling.坩埚Cooling back to the water temperature, all the cooling water is recycled, thus saving water. 3.6 Hydraulic system The main function of the hydraulic system is to provide two hydraulic cylinders with a pressure tank for lifting and lowering components. Two hydraulic cylinders have synchronous lifting and pressure keeping functions. , Synchronous lift is mainly used to prevent tilting of the crucible assembly in the process of lifting. On the other hand, the pressure keeping function is for the seal between the lower flange and the crucible flange of the furnace body; on the other hand, it is to guarantee the flange and the furnace. The contact between the body flanges is good and easy to conduct, so there must be a certain pressing force between the two flanges. During the furnace smelting, the pressure value is kept within a certain range. If the pressure value is lower than the set value, the hydraulic system will automatically start the hydraulic pump. When the pressure reaches the set value, the hydraulic pump will automatically stop until the end of smelting. In order to prevent sudden power failure, an accumulator is also provided in the hydraulic system. When the power is suddenly cut off, the pressure oil in the accumulator will be filled with oil through the valve to prevent the flange flange and the bottom flange of the furnace body from being filled with oil. The entire hydraulic system was taken off using a programmable controller to achieve a sequential operation of 3.7 optical system for dismantling l units, 1200aA Luotong rH-150 spool valve pump and Wishing paint equipment for the electronic control system mainly consists of smelting power supply, each controlled bookmark4 in this equipment There are two observation holes on the furnace cover. Two optical reflectors are installed above the two observation holes. The image of the arc during smelting is reflected on the optical screen through a series of mirrors, and the optical fluorescence screen is placed in the operation room. On the operator's station, when the furnace is smelting, the smelting of the internal electrode can be observed in the operating room. This is safe and convenient. 3.8 Electronic control system and computer console, etc. The main power supply can be used. Silicon rectifying power supply, its working voltage is 20~40V, current is 12kA, the main power supply is placed in a single place, and the electrode pole, vacuum system stabilizer and computer console are placed in the operating room, and the operator can be in the melting room at any time Observe the current voltage, vacuum and other parameters, and the computer can display, record and print out the main parameters at any time. In addition, the arc voltage is used as the parameter for automatic control of the electrode rod lift. The melting begins to manually start the arc and waits for the arc and the weld pool. After normal, the switch is placed in the automatic position, and the elevation of the electrode rod is automatically adjusted according to the change of the arc voltage, so that the smelting process can be automated.

Problems in the process of debugging The furnace has experienced some problems after more than one month of debugging and initial smelting. These problems are proposed here for future reference when developing such furnaces.

4.1Because there is no self-locking between the ball screw and the nut, there is a phenomenon that the electrode rod is automatically lowered. This is mainly because the DC motor driving the electrode rod drives the electrode by rotating the nut through a worm gear reducer. The rod descends, and the worm in this reducer is a double-headed worm, so the reducer does not have self-locking suggestion. After adding a brake at the input end of the reducer or using a single-head worm with self-locking characteristics, the worm and worm reducer is constructed. And the speed of the worm should be less than or equal to 4.2. Because the water cooling cable moves up and down with the electrode rod and the movable beam in the smelting process, its flexibility has a direct impact on the quality of the electrode rod lift and the balance of the movable beam can meet the requirements of the smelting furnace. Under the premise of current demand, it is recommended to use a small number of water cooling cables with small diameter and flexibility. Since the hydraulic cylinders are used to synchronously lift and move the assembly and its moving trolleys, attention should be paid to balancing and guiding problems when the components are lifted synchronously. 4.4 Taking into account that the magnetic field generated by the auxiliary conductive column may affect the arc during melting, the auxiliary guide on the lower flange of the furnace body Column should be evenly distributed along the circumference of the flange.

4.5 Because the furnace adopts a four-column structure with an upper and lower platform, the strength and rigidity of the upper and lower platforms should be taken into account in the design, so that the deformation of the platform and the column is the minimum 4.6 The steel balls at the pneumatic head at the head of the electrode rod are used as much as possible. Many, large diameter steel balls to prevent thermal deformation on the clamping force.

5. Conclusions Through actual debugging and production, it is proved that the surface and internal quality of the ingot produced by the furnace are good, the parts of the equipment are running well, and some major parameter values ​​are better than the design values. Therefore, this structure has a 1t vacuum consumable arc. The furnace is worth promoting.

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