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Jun 4,
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1, strengths
In steel smelting, compared with electric arc furnace smelting, the use of crucible induction furnace has many advantages, such as:
(1) Although the induction furnace is also a high-power consumption device, the interference to the grid is much smaller than that of the EAF.
(2) In respect of the impact on the environment, the noise during the smelting process is small, and the emission of smoke, gas, dust and waste residue is relatively small;
(3) In terms of resource utilization, furnace-mounted materials (including various alloying elements added) have less burning loss and higher yields. The amount of slagging material is much smaller, and no electrodes are used;
(4) In the metallurgical function Because of the electromagnetic stirring effect, the composition of the molten steel is relatively uniform, the temperature of the molten steel is relatively uniform, the temperature control is also more convenient, and there is no problem of carbon addition due to the electrodes. Because there is no high temperature effect of the arc, there is no problem that the nitrogen is dissociated at high temperature and easily absorbed by molten steel;
(5) The investment in equipment is small, and the area occupied by the site is also relatively small;
(6) It is easier to automate operations.
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2, shortcomings
Due to these advantages, since the s, the application of crucible induction furnaces in the field of cast steel has developed rapidly. However, the crucible-type induction furnace also has its own shortcomings, which restricts its development. &#;How to avoid short? &#; is a task that must be faced by process technicians. To avoid shortcomings, you should have a good understanding of these shortcomings.
(1) Problems with refractory linings
The refractory lining is an important part of the crucible induction furnace, ensuring its normal operation, and is crucial to the equipment operation reliability, economic efficiency, safety and even the metallurgical quality of the cast steel products.
The energy used in the crucible induction furnace smelting is the magnetic flux generated by the induction coil, which is transmitted through the refractory lining to the metal in the furnace. As the thickness of the refractory lining increases, the leakage flux increases, and the output power, power factor, and electrical efficiency of the inductor are reduced. In order to minimize the compensation of reactive power by the balance capacitor and improve the electrical efficiency, it is necessary to minimize the thickness of the refractory lining as much as possible. Therefore, in the various furnaces for steelmaking, the thickness of the refractory lining of the induction furnace is much smaller than that of any furnace lining, but the operating conditions are much more demanding than those of other furnace linings.
1) The inner surface of the lining is in contact with the molten steel, the temperature is high, and the outer surface is connected to the water-cooled induction coil. The temperature gradient in the thin lining is very large.
2) The molten steel in the furnace is constantly stirred by electromagnetic action, which enhances the leaching of molten steel to the lining, and also enhances the erosion of suspended oxides on the lining, and the stirring effect also increases the possibility of molten steel absorbing gas. Big.
3) If the compaction of the lining is not enough, or the sintering is not good, there is molten steel penetrating into the crack of the lining during the furnace process. The infiltrated molten steel will not solidify in the crack due to the effect of induction heating, but will be in the crack. Continue to deepen until contact with the coil, causing a short circuit, or even cause a major safety accident.
Therefore, the properties of the lining refractories, the particle size grading, the construction of the lining, and the sintering of the lining must all be strictly required, and there should be no sloppyness.
(2) Problems in metallurgical function
The crucible type induction electric furnace melts the cast steel, and its metallurgical function is much worse than that of the electric arc furnace melting. Therefore, it can only be used for smelting steel grades with general metallurgical quality requirements in the early stage to manufacture small-sized steel castings. After the s, with the continuous improvement of equipment and refractories, it is possible to implement moderate oxidation boiling in the smelting process and to enhance its metallurgical function. The scope of application has gradually expanded to high-quality low-alloy steels, high-alloy steels, and even ultra-low Carbon stainless steel and various superalloys. However, the problem of induction furnace melting in the metallurgical function can not be ignored.
1) Induction furnace smelting. The slag is melted by the heat transferred from molten steel. The temperature of slag is lower than the temperature of the molten steel. It cannot be carried out through multiple metallurgical reactions between molten steel and slag as in the electric arc furnace smelting. Oxidation refining and diffusion deoxidation.
2) The arc furnace smelting, the molten pool is shallow basin type, the diameter of the slag line part is about 4 to 5 times the depth of the bath; the smelting type induction electric furnace smelting, the molten pool is cylindrical, the diameter of the molten pool is less than its depth, The ratio between the two is about 0.6&#;0.75. It can be seen that when the induction furnace is smelting, the molten steel-slag contact interface is much smaller than in the electric arc furnace smelting, and it is impossible to perform the smelting operation using the molten metal-slag metallurgical reaction at all.
Therefore, when the steelmaking company uses induction furnace smelting, the requirements for the charge must be very strict: all raw materials must be known for their chemical composition; the amount of furnace material must be determined by calculation; scrap and return material must be dry, no Sediment, no oil; The maximum size of the furnace material can not be greater than 1/2 of the size of the crucible.
We are frequently asked for the differences of vertical furnaces and
horizontal furnace and for a justification of the higher price of vertical
systems. Therefore we worked out the following table sheet. We hope that this
overview, this comparison sheet will help you to make a proper planning.
We compare in this sheet a horizontal furnace with a vertical furnace
for mass production (VF) and with our small vertical furnace
VF, which is a good alternative to horizontal systems for small companies
as well as for research institutes.
Comparison furnace properties Feature 3- or 4-Tube
Nowadays, mass production of semiconductor chips happens with silicon
wafers with 200mm or 300mm diameter. Vertical furnaces are used almost
exclusively. Only in older factories, which still use smaller wafer diameters,
horizontal furnaces are still common. For wafer diameters until 6" the
performance of such systems is in many cases still good enough to fulfil
the customer requests. However, the advantages of vertical systems are already
evident for this wafer size.
The result of this situation on the oven market was, that almost all
large furnace manufacturers stopped the further development of horizontal
furnaces. Development work is done today almost only for vertical systems.
Therefore vertical furnaces are superior to horizontal ones not only for
physical reasons, but also because they are the more modern production tool.
Their performance is much higher.
A main issue is furnace automation. Automation for horizontal furnaces
means mainly the installation of an elevator system for the loading of the
boat on the cantilever arm. The loading area is open to the clean room.
Vertical furnaces however are closed system with clean room class 1 inside. The
loading happens fully automatically from the cassette by advanced robot systems.
Other technical advantages of the vertical furnaces are the better
gas tight sealing of the furnace tube, as well as several options,
availabe only on vertical furnaces like improved temperature uniformity by
boat rotation or nitrogen load lock chamber.
For smaller enterprises, pilot lines, research institutes and universities
this development has the disadvantage that high performance is coupled to
high grade of automation and therefore to a high equipment price. For budget
reasons the only way out is quite often the purchasing of horizontal furnaces,
although the customers has to accept in this case the lower performance of such systems.
Since several years, the company of JTEKT Thermo Systems (previously Koyo Thermo Systems) can offer a
better solution. KTS developed a small vertical furnace named VF for
these customers. The VF is a full performance vertical furnace. The capacity of this
furnace has been kept small, because research customers require small capacity
in most cases. Therefore this system has been developed as a mini batch furnace
for 25 wafers (standard) or 50 wafers (option) capacity. The wafer loading
of the boat is done manually, which increases the flexibility of the furnace
a lot, while all other steps like the boat loading to the furnace and the
performance of the process recipes are handled fully automatically same as
on the mass production tools. The price of such a furnace finally is only
little bit higher compared to a horizontal furnace tube.
The required footprint of our small vertical furnace is by the way smaller
compared to the footprint of horizontal furnaces! We show you an example
of the layout of 12 tubes (5 tubes PECVD) in vertical VF design and in
horizontal type 208 design (3 tubes per stack).
JTEKT Thermo Systems manufactures numerous versions of vertical furnaces and horizontal furnaces with full automation or manual loading. Smaller versions for pilot and laboratory applications are available.
JTEKT Thermo Systems and Crystec will be pleased to engineer a cost effective system to satisfy your most demanding and exacting requirements.
The company is the world’s best Best Vacuum Sintering Furnace Price supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.