Vacuum Melting Furnace (VIM)

 

Vacuum melting furnace

With the rapid development of modern industrial technology, people’s requirements for the use of mechanical parts are getting higher and higher, the more stringent the use of the environment on the metal material’s high temperature resistance, wear resistance, fatigue resistance and other properties put forward higher requirements.For some specific metals or alloys, either in preliminary research and development trials or at a later stage in mass production, the research or obtaining of high-performance metal alloys requires the support of metal melting equipment, surface heat treatment equipment, etc. Among the many special heating or melting methods, induction heating technology plays a vital role in the preparation of metal materials by melting or in the sintering of materials in certain processes, heat treatment, etc.

Vacuum induction melting furnace is a melting equipment that melts metal by induction heating under vacuum and then pours the liquid metal into a mold to obtain metal ingots. the material is to create metal bar-sticks, electrodes, flakes, wires, foils or bands depending on the user requirement.

Melting and casting in vacuum or controlled inert gas atmosphere is often required for the production of a variety of high-performance metal alloys and is essential for quality manufacturing of Ni-based super-alloys as well as Fe-, Co-, Cr-based and other special alloys.

The development of vacuum induction furnaces began around 1920 and were mainly used to smelt nickel-chrome alloys. It wasn’t until World War II that the advancement of vacuum technology was facilitated, allowing vacuum induction melting furnaces to really develop.. During this period, due to the demand for alloys, vacuum induction melting furnaces continued to move to larger capacity , from the first small capacity to very large to production capacity which can up to 10 tons.

In order to adapt to high volume production, in addition to the change of equipment capacity, the structure of the induction furnace has evolved from a cyclic vacuum melting furnace(single-chamber vacuum furnace) on a periodic basis to a continuous or semi-continuous vacuum induction melting(double-chamber vacuum furnace) with charging, mold preparation, melting and pouring operations.

Continuous operation in a non-stop furnace saves time for loading and cooling of ingots, and continuous production increases efficiency while increasing alloy production.Better meet the needs of actual production.

The diagram shows the basic form of a vacuum induction melting furnace, where the metal material is added to the melting crucible through a rotating turret and the vacuum pumping system removes the gas from the inside of the vessel to a suitable vacuum level,When melting, the turret is rotated at an angle, the other side of the arm is aligned with the crucible, and the temperature is measured by inserting the thermocouple downward into the metal melt.The smelted metal is driven by a tilting mechanism and poured into the mold to achieve the smelting of the metal.

The whole process is simple and convenient to operate, each melting requires one to two workers to complete, the melting process can realize real-time temperature monitoring, material composition adjustment, the final metal material more in line with the process requirements.

3.1 LABORATORY VACUUM MELTING FURNACE(1-10kg)

Laboratory vacuum furnace is not only applied to major university, scientific research institutes & material laboratory , but also can be used in production company’s research  department . The laboratory vacuum induction furnace is capable of melting metals under vacuum (or with protective gas) using the principle of medium frequency induction heating. Due to  its tight control of temperature and alloy composition, electromagnetic stirring and powerful high vacuum degassing capacity. It is ideally suited for use in metallurgical plants and related scientific research departments as a high vacuum degasser for nickel-based, iron-based, high-grade precision alloys, high purity metals and other materials. Effective equipment for melting and casting under the conditions.

1-3kg laboratory vacuum furnace: generally equipped with a direct link rotary vane vacuum pump, oil diffusion pump or molecular pump, with high vacuum, strong function, compact equipment and small footprint, etc.

5-10kg Vacuum melting furnace : generally equipped with three-stage pump, with a wide range of functions, such as the advantages of small castings, test rods and ingots can be melted.

Materials

Ni-base super-alloys
Fe-, Co-, Cr-base alloys
High alloy steels & Magnetic alloys
High purity Cu-, Al- and Mg-alloys
Precious metals and their alloy
Refractory metals and their alloys

Material Characteristics

High purity
Low O, N, and H concentrations
Precise chemical composition
Tight compositional tolerances
Excellent surface quality

Applications and Markets Served

Research and development
Pilot-scale production
Aviation industry
Power engineering
Electronics and chemical industry
Bio-medical engineering
Precious metal industry

3.11 3kg small vacuum melting furnace

Performance:

Furnace type: Horizontal type
Melting capacity: 3kg(Steel)
Melting temperature: 1800 c
Melting time: 10min
Limit vacuum: 6.6×10-4pa
Exhaust time of melting chamber: 30 min

The small 3 kg vacuum melting furnace consists of furnace body, furnace cover, vacuum system, medium frequency power supply, coil, rotating shaft power supply, observation mechanism, furnace body trolley, etc.

Furnace body:

The furnace body of the ZG-0.003 vacuum induction melting furnace adopts a horizontal double-layer water-cooling structure with cooling water in the middle. The furnace material is made of 304 stainless steel.

The inner wall of the furnace is polished and has smooth surface without sharp corners and sharp edges. As long as a simple mechanical cleaning method is used, the metal volatiles and dirt produced by gasification in the melting chamber can be removed. This will not only shorten the pumping time, but also obtain a good limit vacuum.
The baffle plate is installed at the front of the exhaust port of the furnace body to prevent metal splashing from entering the vacuum pipeline.

The furnace body is installed above the electric control cabinet. The bracket of electric cabinet requires sufficient strength and stability conditions, which will not cause tilt.

Feeding system:

In order to add various elements in the process of vacuum melting, a special five- grid feeder is installed on the furnace lid. It has a special sealing cover designed to vacuum seal the feeder. Before vacuuming the container, the element is pre-placed in the feeder. When the element is added, the handwheel rotates the feeder to mark the graduation, and the element falls from the opening to the hopper. Another handle flips the hopper. After the element is sent over the crucible, a control plate opens automatically, allowing the elements in the hopper to flow from the liquid surface near the molten metal, avoiding splashing, and then automatically reset by spring torsion. Through the above device, the task of adding alloy elements can be conveniently accomplished in vacuum according to the order of feeding required.

Induction coil:

The induction coil is made of rectangular copper tube, and the surface of the coil is sprayed to prevent vacuum discharge. There are 3 to 4 millimeters of gaps between turns and turns, and they are fixed through the insulation board around them.

The induction coil and the inlet and outlet electrodes are connected by nuts, and the disassembly is convenient. At the same time, ensure that the entry and exit electrodes have good sealing performance.

There is a crucible in the coil. There is a layer of glass cloth or asbestos cardboard between the crucible and the coil. One is to protect the coil, the other is to prevent the filler from leaking out, so as to avoid the short circuit caused by the coil touching the conductive crucible. On the other hand is to prevent the coil from being directly exposed to the heat radiation of the crucible.

The bottom of the coil is welded with three hook plates to support the refractory plate, and the refractory plate is used to support the crucible.

Rotating electrode:

The rotating electrode is a rotating sealing device, which is mainly used to introduce electric energy and pass through cooling water. The current is generated from the capacitor bank of intermediate frequency equipment, and the cable can load thousands of amps of strong current. The cable is connected to the joint outside the rotating electrode, and the copper electrode is put into the vacuum furnace body to bring the current and cooling water to the induction coil. When the electrode enters the vacuum furnace body, the vacuum rubber seal is adopted. A tilting handle is installed on the outside of the vacuum furnace, and tilting and resetting can be realized by rotating the tilting handle back and forth. The rotating electrode can rotate the coils, crucibles and smelting metals together.

Vacuum system:

The vacuum unit consists of a vacuum valve, a pipeline and a vacuum pump. A 200L diffusion pump and a Z-15 monoblock pump are used in the vacuum unit.

Water cooling system:

The water cooling system is composed of water cooling unit, pipeline and valve, etc. The water cooling system is mainly used for supplying cooling water to vacuum furnace, induction coil and molecular pump. The cooling capacity of the water cooling unit is 7.5kW, and the water supply flow is 1.5 tons / hour.

Electric contact pressure gauge is installed on the water cooling pipeline, and when the water supply is not enough or the pressure is insufficient, the alarm signal is sent out.

Others:

There is an observation window on the furnace body to observe the smelting in the melting room. A rotating baffle is installed in front of the observation window to protect the quartz glass on the observation window from metal vapor pollution. The rotating baffle is closed at normal times. The baffle can only be turned through the handle when observing.

Vacuum degree measurement adopts 2 low 1 high number display compound vacuum gauge

 

3.2 Batch vacuum furnace(single-chamber VIM systems )

Single vacuum melting furnace share a melting and casting chamber. If you want to take out the ingot mould, you have to break the vacuum of the whole furnace, then refill, vacuum and smelt under atmospheric pressure, one cycle for each furnace, so it is also called cyclic furnace.It is mainly used for the melting and purification of stainless steel, high temperature alloys and magnetic materials, and for the production of alloy bars for precision casting and remelting electrodes. Periodic production.

Suitable for  following industries:

Aviation industry – turbine blades, vanes
Power Generators – turbine blades
Automotive Industry – turbo charger wheel impellers
Medical/Chemical/Electronic Industry
Modular furnaces concepts for different sizes and process requirements

3.21 125kg vacuum induction furnace

ZG-125L vacuum induction melting furnace is mainly used for melting, smelting and casting of various superalloys, iron-based, nickel-based alloys and some non-ferrous metals and their alloys under the protection of vacuum or inert gas using the principle of medium frequency induction heating.. The feeding bin is separated from the melting bin by a valve, so the feeding, temperature measurement and melting can be carried out without damaging the vacuum conditions.
The service temperature of zg-125l vacuum induction melting furnace generally depends on crucible material. When magnesium oxide is used as crucible material, the smelting temperature can reach up to 1800℃.When zirconia is used as crucible material, it can reach 1900℃, while when graphite crucible is used, it can reach 2500℃. Users can choose crucible material types according to their melting materials.
In a word, ZG-125L vacuum induction melting furnace is a kind of vacuum smelting equipment with the advantages of wide use, strong adaptability, high production efficiency, easy to use, homogeneous alloy composition, small occupied area and easy to use and maintain.

Equipment composition

ZG-125L vacuum induction furnace is composed of electric furnace body, medium frequency melting power supply, electric control system, vacuum system, power supply system, tilting mechanism, inductor, isolation valve, hydraulic system, pneumatic system, water cooling system, and working platform.

Electric Furnace Body:

The main body of electric furnace is composed of furnace body, furnace cover, charging and temperature measuring system. The melting chamber and the feeding bin are connected by ￠300 mm plug-in valve.

Furnace cover:

The furnace cover is a double-layer structure, with 316L stainless steel plate (plate thickness (≥ 10mm) in the inner layer & outer layer , water-cooled interlayer and integral forged flange of stainless steel in the outer layer. The furnace cover is provided with two observation holes and one temperature measuring, sampling and secondary charging hole. Additional flange/port on the top door to connect a pyrometer.

Observation hole:

The furnace cover is equipped with two observation holes, each of which is equipped with four quartz glass protective sheets to realize work conversion. The size of the observation holes is greater than or equal to 50mm. The observation holes are used to observe the process of temperature measurement, smelting and pouring.

Opening mechanism:

Hydraulic lifting spindle rotating structure is used to open the furnace cover. Hydraulic driving mode is used for lifting and manual mode is used for horizontal rotation. The connecting parts should be strengthened locally to avoid deformation after long-term use, and the design ensures the easy opening of the furnace cover.

Melting chamber:

The smelting chamber is a double-deck vertical drum structure, which is made of 316L stainless steel in the inner layer & the outer layer. The furnace body is equipped with vacuum measuring port, gas filling port, vacuum pumping port and electric inlet. The front furnace door can also be installed in front of the furnace body according to user’s requirements, and the ingot mould truck or manual forklift truck can be used for ingot mould entry and exit.

Feeding system:

The ZG-125L vacuum furnace is equipped with a main charging device. The volume of 10L can be operated electronically by adding strip, rod and block metal materials. An isolation valve is arranged between the charging chamber and the furnace body, and the charging can work under vacuum conditions.

Temperature Measurement System:

ZG-125L vacuum furnace has a temperature measuring system. The temperature of molten pool can be measured in vacuum. Using electric temperature measurement operation, tungsten-rhenium thermocouple, the maximum use temperature can reach 1800℃, digital display.

Medium frequency smelting power supply:

Medium-frequency smelting power supply uses KGPS medium-frequency power supply, parallel resonance mode. The rated power of intermediate frequency is 160kW and the rated voltage of intermediate frequency is 375V. Using 2000-2500Hz frequency for smelting, the stirring effect is good to prevent alloy segregation.

Electrical Control System:

The control of ZG-125L vacuum induction melting furnace adopts PLC programmable controller. PLC programmable controller has high reliability and low failure rate. Temperature and vacuum are measured by a digital device adapted to the atmosphere in the furnace. The electric control operation of 125kg vacuum induction furnace is controlled by man-machine interface. The picture is intuitive and easy to operate.

Vacuum system:

The vacuum system consists of a main vacuum system and a sub-vacuum system. The main vacuum system is mainly used for vacuum extraction in smelting chamber, and the secondary vacuum system is mainly used for vacuum extraction by isolation valve.

Input System:

The input system of ZG-125L vacuum induction furnace is copper shaft. External protective jacket. The tilting shaft is assembled with stainless steel as its outer material. The rotating shaft adopts a composite structure for replacement after wear and tear. Six seals and three insulations are made here to ensure no leakage, no discharge, and easy maintenance.

Tipping mechanism:

The tilting mechanism of ZG-125L vacuum induction furnace and the tilting cylinder are installed outside the furnace chamber. Maintenance and repair are convenient, basically achieve long-term maintenance-free, sealed with four sealing structure to ensure long-term reliable work. The tilting furnace is controlled by manual hydraulic proportional valve, which can adjust the tilting speed of crucible with the moving angle of valve stem, and can satisfy the casting of various dies and steel grades.

Induction Coil:

ZG-125L induction coil is made of T2 copper. The support of coil is fixed, and the structure of stainless steel shell is adopted. The strength of coil is greatly improved. The coil surface is coated with high temperature insulating paint and covered with insulating tape. At the same time, it is suggested that users should coat the inner surface of the coil with plastic alumina coating to ensure the insulation strength under high temperature conditions.

Hydraulic system:

The tilting, cover lifting and charging lifting of ZG-125L vacuum induction furnace are all operated by hydraulic pressure. The key parts such as tilting furnace are equipped with hydraulic lock. Hydraulic tilting furnace adopts proportional speed regulating hydraulic valve with good handle, flexibility and reliability. Hydraulic station has water cooling system.

pneumatic system:

All vacuum valves are driven by compressed air. The pneumatic system consists of pipeline, joint, oil-water separator, air compressor, oil atomizer and pneumatic valve.

Water cooling system:

The ZG-125L water cooling system is divided into two forms, namely, open backwater and closed backwater.Open backwater is recommended if user conditions permit. The water cooling system is equipped with a water temperature patrol instrument for every return water, and an electric contact pressure gauge for the main water inlet. An alarm will be sent when the pressure on the main road and water temperature on any road exceeds the value.
Cooling flow: 50m3/h, cooling water pressure: 0.2-0.3mpa
Recommended total inlet and outlet diameters DN100.

3.3 Semi-continuous vacuum induction melting

Semi-continuous vacuum furnace means the  whole melting process is under vacuum conditions, using the principle of medium-frequency induction heating, the metal charge placed in the crucible is melted under the action of the induction coil to produce alternating magnetic field, the molten charge is poured into the ingot under vacuum through the inner door into the ingot chamber.After closing the inner door, vacuuming, refilling, remelting, and then carried out. At this point, the furnace door can be opened at a certain time to remove the ingots and so on. It is characterized by the separation of the functional chambers from each other, the vacuum atmosphere  in the melting chamber is not destroyed, and the casting process is completed by the closure of the valve.The process can continuously add the steel, the reciprocal closing and opening of the valve, so it is called semi-continuous (also called compact) vacuum induction melting process.

 

3.31 50kg Semi-continuous vacuum induction melting furnace (three-chamber vacuum furnace)

The 50kg vacuum semi-continuous induction furnace is a modern equipment for melting metals under vacuum conditions using the principle of medium frequency induction heating. Due to its strict control of melting temperature and alloy composition, electromagnetic stirring and strong high vacuum degassing ability, it is widely used in metallurgical plants and related scientific research departments as a nickel-based, iron-based and other advanced precision alloys or high-purity metals for melting and casting under vacuum conditions or under a protective atmosphere. The most important feature is that it is possible to guarantee to a certain extent the temperature of the hot mould from the time it enters the ingot chamber to the time it is cast in the melting chamber. Designed to take less than 3 minutes from the time the hot mold enters the spindle chamber and closes the door to the completion of a pouring process.

Main technical indicators

Capacity (in steel): 50kg
Rated working temperature: 1800℃
Melting rate (at 1600°C): 150kg/h
Working vacuum: 6.6×10-1Pa
Ultimate vacuum: 5×10-3Pa
Pressure rise rate: 5 Pa/h
Ingot mold entry to casting time ≤3min
Medium frequency output power: 120kW
IF output voltage: ≤275V
IF output frequency; 2 to 2.5kHz
Cooling water flow: 20t/h
Cooling water pressure: 0.2～0.3MPa
Total equipment weight: 10t
Spindle chamber below 50pa, valve open

Main technical indicators

The 50kg semi-continuous vacuum induction melting furnace consists of furnace body, medium frequency power supply (IGBT120/2.5S), electrical control system, vacuum system, power inlet system, pouring mechanism, coil, isolation valve, hydraulic system, pneumatic system, water cooling system, in addition to a working platform, etc.

Electric furnace body

The electric furnace body is composed of the furnace body, lid, charging and temperature measurement system. The furnace body consists of a melting chamber, an ingot and mould chamber. Between the melting room and the charging silo with 250mm gate valve connection, between the melting room and the ingot and mould room with 500mm gate valve connection. The bottom of the furnace is equipped with an ingot mechanism. Able to fully meet the elevation of 700mm high 700mm mold.

Furnace cover

The furnace cover is a double water jacketed butterfly head with 304 inner layer and carbon steel outer layer. The furnace is equipped with a vacuum measuring port and a charging port. The furnace body and the furnace lid are linked together by a hydraulically operated column, and the furnace lid is hydraulically driven.

Smelting chamber

The smelting chamber is a two-layer vertical cylinder mechanism with an inner layer of 304 and an outer layer of carbon steel. The furnace body is equipped with vacuum measurement port, filling port, vacuum port, power inlet, ingot and other interfaces.

Spindle die chamber: (reserving housing heating connections and power connections)
The spindle chamber is double U-shaped shell structure with 304 stainless steel inner layer, carbon steel outer layer and water-cooled structure. The interior is equipped with a spindle tank that moves up and down. The spindle chamber is equipped with an air extraction port and a vacuum measuring port. The spindle room door opens and closes freely. The spindle chamber is flanged to the spindle lift mechanism for easy removal. There is a spindle carriage outside the door of the spindle room (user-supplied), which makes it easy and fast to pick up the spindle mold. (adjustable lifting speed range 12-∞ sec.)
The briquetting mechanism adopts hydraulic cylinder structure with stable lifting speed and limited position switch for both casting and briquetting height.
All inner surfaces of the lid, melting chamber and ingot chamber are polished and the smooth inner surface is conducive to increased vacuum and easy cleaning.

Feeding systems

The 50kg semi-continuous vacuum furnace has a main charging unit. The feeding device can be designed as robotic structure or hopper structure, the robotic mechanism can meet the secondary feeding of φ90±10mm bar material, the clamp can be replaced. The hopper mechanism allows for the addition of various lumpy strips of material. The dosing systems are all capable of operating under vacuum.

Temperature measurement systems

There is a temperature measurement system. The temperature of the melted metal is measured. Using electric temperature measurement operation, tungsten rhenium thermocouple, the maximum operating temperature can reach 1800 ℃, digital display. Infrared temperature measurement is also available.

Medium frequency power supply

The IF power supply can use SCR IF power inverter line. The rated power of the medium frequency is 120kW and the rated voltage of the medium frequency is 375V. The output frequency of the medium frequency is 2500Hz. the choice of the medium frequency voltage is related to the coil structure.

Electrical control systems

ZG-0.050LB semi-continuous vacuum induction melting furnace is a multi-functional vacuum smelting equipment, the control is complex, so PLC programmable controller and touch screen chain control are used, PLC programmable controller has high reliability and very low failure rate.
The temperature and vacuum are measured using digital devices that can be adapted to the atmosphere in the furnace. At the same time, the furnace temperature signal, water temperature signal, etc. are input into the programmable controller, once the parameters are exceeded, an alarm signal or stop can be issued, thus ensuring the safety of the equipment.

Vacuum systems

The vacuum system consists of a main vacuum system and a secondary vacuum system.

Main vacuum system

The main vacuum system of the ZG-0.050LB semi-continuous vacuum induction furnace consists of an H150 slide valve pump, a ZJP-600 Roots pump, a KT-400 diffusion pump, vacuum valves and a filter dust collector to vacuum the melting chamber. The pumping speed of the mechanical pump is not less than 150 L/S (l/s) and that of the Roots pump is not less than 600 L/S (l/s). The vacuum valve used is pneumatic. Its construction is simple, reliable and effective in preventing dust from affecting the airtight seal. The vacuum system has a segmented detection setting and an electrical protection system with a water break protection device, which greatly improves operational safety.

Subvacuum systems

Auxiliary vacuum systems are mainly used for feeding, temperature measurement and vacuuming of alloy feeding silos and ingot chambers. It consists of an H-150 slide valve pump, ZJ-600 Roots pump, filter cleaner and pneumatic valve, and is used to maintain vacuum in the spindle chamber.
The vacuum system is equipped with a filter dust collector to reduce dust contamination of the pump oil.

Power feed system

ZG-0.050LB vacuum system vacuum induction furnace power inlet system is a small braid type power inlet structure, using 0.1 braided wire to form multiple power inlet system, the line voltage drop is generally not more than 5V, plus protective sleeve.

Pouring mechanism: (pouring speed – speed adjustable proportional valve – manual control) max. 5s
The ZG-0.050LB vacuum induction furnace has a tilting mechanism with a separate inlet and tilting design. The feed-in system only takes on the task of feeding electricity. The decanter torque is borne independently of the spindle. The assembled spindle is easy to install and the tilting cylinder is mounted outside the furnace. It is easy to repair and maintain, basically maintenance-free for a long time, with a 4-channel sealed structure to ensure long-term reliable operation. Manual hydraulic proportional valves are used for the decanter operation.

Induction coils

ZG-0.050LB vacuum induction furnace induction coil, structure is single-segment coil, independent suspension, flange connection, external spray insulation material, coated plastic Al2O3 features high strength, low deformation, long life, voltage class 250V.

Gate valves

The ZG-0.050LB has an gate valve between the melting chamber and the spindle mold chamber, pneumatically controlled, with a disintegrating action and one action to pull and push the valve disc back and forth. When the valve is closed, the gate valve is locked by a hydraulic lock after the valve plate is in place, and the valve is opened by locking first and then opening the valve to ensure the reliability of the work.

Hydraulic systems

The ZG-0.050LB vacuum induction furnace is hydraulically operated with gate valve, tilting furnace (electric option) and lid lift. The key parts such as the decanter is equipped with hydraulic lock, the gate valve is equipped with hydraulic lock to ensure reliability, the decanter has an automatic reset mechanism to ensure safe operation. The hydraulic tilting furnace adopts proportional speed-regulated hydraulic valve with good feel, flexible and reliable. The hydraulic station has a water cooling system to cool the oil.

Pneumatic systems

The vacuum valves of the ZG-0.050LB vacuum induction furnace are pneumatic, so they have a pneumatic system. It consists of piping, coupling, oil-water separator, air compressor, oil atomizer, solenoid valve, cylinder, etc. (air compressor users provide their own).