Why is the insulation layer of vacuum heat treatment furnace cylindrical?

First, the heat insulation layer of the vacuum heat treatment furnace is the place where the workpiece is heated. Its main function is to insulate and heat preservation and reduce the heat loss.
Second, in general, the insulating layer of vacuum furnace is made into cylinder shape as far as possible. From the perspective of heat transfer, the cylinder structure has good heat transfer effect and small heat loss. The internal dimension of the thermal insulation layer is the dimension of the furnace, which is mainly determined by the shape and size of the processed workpiece and the production division of the furnace.
Thirdly, the heating effect of the vacuum heat treatment furnace, the uniformity of furnace temperature and the convenience of maintenance and charging and discharging operation should be considered. Generally, the distance between the inner surface of the insulating layer of the vacuum heat treatment furnace and the heater is about 50 to 100 mm, and the distance between the heater and the workpiece, clamp or basket should be about 50 to 150 mm.
Fourth, according to the different materials and structural forms, the insulation layer of the vacuum heat treatment furnace can be roughly divided into five types: refractory lining, sandwich type insulation layer, all metal anti radiation screen, mixed felt insulation layer and graphite felt insulation layer.
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Hot air furnace direct type high purification hot air furnace working principle

It is to use fuel direct combustion, through high purification process to form hot air, and direct contact with the material heating drying or baking. This method USES about the same amount of fuel as steam or other indirect heaters
Reduce it by about half. Therefore, in the case that does not affect the quality of drying products, can use direct high purification hot air.
Fuel can be divided into:
Solid fuels, such as coal and coke.
Liquid fuel, such as diesel, heavy oil, alcohol - based fuel
Gaseous fuels, such as gas, natural gas, liquid gas.
The high temperature combustion gas obtained by the fuel after combustion reaction further contacts with the outside air, after mixing to a certain temperature directly into the drying chamber or baking room, and the drying material contact, heating, steaming
Hair moisture, thereby obtaining dry products. In order to utilize the heat of combustion reaction of these fuels, a fuel combustion device must be added. Such as: coal burner, oil burner, gas burner, etc.
This type of direct heating hot air furnace can not be used for breeding and other heating.
Indirect hot air furnace
It is mainly used for drying materials which are not allowed to be contaminated, or for drying heat sensitive materials with low temperature. Such as: milk powder, pharmaceutical, synthetic resin, fine chemical and so on. Such a heating device is
Steam, heat conduction oil, flue gas and so on as the carrier, through various forms of heat exchanger to heat the air.
The most essential problem of indirect hot air furnace is heat exchange. The larger the heat exchange area, the higher the heat conversion rate, the better the energy saving effect of hot air furnace, the longer the life of furnace and heat exchanger. Instead, heat is exchanged
The size of the area can also be identified from the flue gas temperature. The lower the smoke temperature, the higher the heat conversion rate, the larger the heat exchange area.
After the separation of fuel and heating source, it can be used for human heating.
Working principle can be divided into two kinds of heat storage and heat transfer
Regenerative type, according to the regenerative body inside the hot air furnace divided into ball type hot air furnace (referred to as ball furnace) and the use of lattice brick hot air furnace, according to the combustion mode can be divided into top combustion type, internal combustion type, external combustion type and so on. Such as
How to improve the wind temperature, is the direction of long-term research. Commonly used method is mixed burn high calorific value gas, or increase the heat transfer area of hot air furnace lattice brick, or change the material quality of lattice brick, density, or
Change the shape of the regenerator (such as the regenerator ball) and preheat the gas and combustion air by various means.
Advantages: high heat transfer temperature, high heat utilization.
Sun fule hot air furnace (3) disadvantages: large size, large floor area, hot air temperature is not stable, more switching mechanism, easy to problem, heat storage short life, high maintenance cost, high purchase cost.
Heat transfer type, the main use of the use of high temperature heat exchanger as the core component, this component can not use ceramic hot air furnace
Metal material heat exchanger, can only use heat resistant ceramic heat exchanger, gas gas in the combustion chamber full combustion, burning the hot air, after the heat exchanger, the heat to the fresh air, can make
The temperature of fresh air surpasses 1000 degrees.
Advantages: high heat transfer temperature, high heat utilization rate, small size, stable hot air temperature, no switching mechanism, long life, high maintenance cost, low purchase cost.
Disadvantages: heat transfer temperature is not as high as the heat storage, appeared late, not widely used.
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FRP cooling tower selection of circular counter flow

The circular counter flow FRP cooling tower is suitable for the circulating cooling water system with small and medium water volume and multiple water sources distributed, and the layout is very flexible and convenient.
1. Standard design conditions: dry bulb temperature 31.5 ℃, wet bulb temperature 28 ℃, atmospheric pressure 99400pa, inlet water temperature 42 ℃, outlet water temperature 32 ℃;
2. The selection of special packing for the laminated high-efficiency round tower makes the cooling tower compact in structure, small in floor area and flexible and convenient in layout;
3. Using the large diameter, large area, low speed and low dynamic pressure FRP fan blades of wing type hollow structure, the cooling tower has the characteristics of energy saving and low noise;
4. The super low noise cooling tower is equipped with high-efficiency noise reduction device at the air inlet and rain area, so that the effective noise reduction of the same level cooling tower can reach 5dB (a);
5. The application of a large number of high-strength FRP structural parts in this kind of cooling tower makes it have the obvious advantages of excellent corrosion resistance and long service life;
6. Small cooling tower adopts rotary water distribution system with simple structure and uniform water distribution, which further improves the thermal performance of cooling tower. Large cooling tower adopts fixed water distribution system to further improve the stability of tower body;
7. The rotating water distribution system is equipped with water baffle device, and the fixed water distribution system is equipped with water collector device, so that the floating water loss of the cooling tower is reduced to within 0.01%;
8. The circular tower structure endows it with good wind pressure resistance, which is especially suitable for use in coastal typhoon areas. The designed wind resistance capacity of this kind of cooling tower is 0.75kn/m2;
9. Small size, light weight, simple structure, easy installation and maintenance;
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The method of selecting filter media material for plate - frame filter press

1, suitable for the selection of plate frame filter filter media
The filter medium selected by the plate and frame press is generally the press cloth, but also the selection of cardboard or filter paper (cotton cake filter and plate and frame type oil filter) as the filter medium. The filter cloth suitable for filter press is divided by material, and the synthetic fiber is more. According to the structure, a kind of press cloth "calendered press cloth", which is suitable for press and filter, is mainly introduced in the following. When press cloth is calendered at high temperature, the holes in the yarns change from straight flared to inverted flared. When the unshaped filter cloth is filtered, the solid particles (fine particles) are easy to be trapped in the bell mouth to block the filtering channel, which cannot form good bridging pores and affect the filtering effect. Press cake and press cloth bond. Affects cake shedding and cloth washing. Press cloth after high temperature setting, smooth surface, stable aperture structure, not easy to deformation; The bell mouth forms a funnel, and the solid particles will not be stuck; It can form a good bridging filter layer. The filter precision is higher, the filter cake is easy to fall off, the press cloth is easy to clean, and the sealing between the filter plates is improved, the capillary leakage between the filter plates is reduced, more suitable for the operation of automatic filter press. Surface high temperature setting technology has good effect on treatment. Only the monofilament cloth can keep the treated structure stable without deformation, but the impact resistance and tensile strength of the monofilament cloth are far less than that of the compound silk cloth, which is very easy to be damaged. As a result, press cloth manufacturers produced a monofilament press cloth to overcome the weakness of monofilament press cloth. Use single wire filter cloth as the retaining layer and compound wire filter cloth as the supporting layer. The press cloth produced by this treatment technology can meet the requirements of the press press.
2. Selection principle and method of press cloth of plate and frame press
(1) the material of the press cloth should be selected according to the chemical and physical properties of the material. All press cloth suppliers provide as much technical information as possible.
(2) select the permeability of the press cloth according to the requirements of filtration accuracy (large interception particle size). The selection can be made by referring to the technical parameters such as large interception particle size provided by the filter cloth supplier. Although the press cloth plays a very important role in the initial filtration accuracy of the filter press, the higher the initial filtration accuracy is not the better, it is ok to consider that the filtration accuracy can reach a low requirement. Because the filter press in a period of time after the formation of the filter layer, the interception of the filter cloth is very small, really plays the role of fine filtration of the foot "filter layer", the formation of a good filter layer is the key to the use of the filter press technology.
(3) stripping performance of filter cake. When selecting the filter cloth, special attention should be paid to the stripping performance of the filter cake. Press cloth surface smooth flat, filter cake stripping quickly, short filtration operation time, high efficiency. It is not easy to strip the filter cake when it sticks to the press cloth, which will prolong the operation time of the filter press and reduce the working efficiency. If the press cloth needs to be replaced, the time will be longer. Now the general application of the wing press filter, press cloth replacement are more difficult. It is better to choose single silk press cloth than long compound silk and short fiber press cloth, and satin weave than plain weave press cloth.
(4) properties of press cloth. When choosing a press cloth, it is important to choose a good press cloth. The press cloth with good performance can be washed directly on the press press to reduce the number of cloth changes. After simple treatment (drying, washing, etc.), the filtration efficiency of the replacement press cloth is restored to more than 80%.
(5) material filtration experiment. The use of filter press is an experimental technology. It is very important to carry out filtration experiments on raw materials (without changing material properties and process conditions) after the preliminary selection of press cloth. Carry out sample experiment on material filtration. The filtration rate, interception effect, filter cake moisture content and cake unloading performance of the filter cloth were investigated.

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Laser welding machine for water pump impeller application

Laser welding machine technology of water pump impeller makes up for the disadvantages of traditional resistance welding. The linear sealing rate of the front and rear cover plates and blades of the impeller is almost 100%. The smooth and accurate flow passage reduces the hydraulic loss of the flow passage to the minimum, ensures the efficient operation of the pump to the maximum extent, and reduces the operation cost of the customer.
The impeller is not only the disc with moving blades, but also the component of the rotor of the excited turbine. It also refers to the general name of the rotating blades on the wheel disc and equipment. It also refers to the general name of the rotating blades on the wheel disc and equipment.
The blade shape of centrifugal fan impeller includes single plate type, circular arc type and wing type. Wing type blades have outstanding aerodynamic characteristics, high power, good strength and high stiffness. Its disadvantage is that the manufacturing process is disordered, and when the gas with high dust concentration is transported, the blade is slightly worn. After the blade is worn through, impurities enter into the blade, causing the impeller to lose balance and oscillate. Compared with the airfoil blade, the power of other operating points is close to each other, except that the power near the highest power point is lower.
Water pump impeller automatic laser welding machine selected new ideas and skills, welding speed is very fast, welding accuracy is good, the beam form is good, can achieve new automatic welding positioning, the output power is several times higher than other laser welding. The laser welding machine adopts the active platform and rotating platform and the active lifting laser beam. With the help of the software of the laser welding machine, it can modify itself and the operation method is simple.
Impeller laser welding machine features:
It is driven by X, y, Z and D axes of the welder, satisfying the demand of large stroke;
High accuracy of positioning repetition;
Welding point, straight line, circle, ellipse and square plane arbitrary orbit;
High power laser power supply, satisfied with 24 hours mass production;
The four-axis linkage control system is specially designed for laser welding, with stable performance and easy to use.

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The water cooling device in the experimental furnace can prolong the service life

Water cooling device: the shell, cover, electric heating element, water-cooling electrode, middle vacuum insulation door and other components of the vacuum heat treatment furnace are all working under vacuum and heating conditions. In this extremely unfavorable condition, it is necessary to ensure that the structure of each component is not deformed or damaged, and the vacuum sealing ring is not overheated or burnt. Therefore, each component should be equipped with water-cooling device according to different conditions to ensure that the vacuum heat treatment furnace can operate normally and have sufficient service life.
Using low voltage and high current: when the vacuum degree is within the range of several torrs and one lxlo-1 Torr, the electrified conductor in the vacuum vessel will produce glow discharge under high voltage. In the vacuum heat treatment furnace, serious arc discharge will burn down the electric heating elements and heat insulation layer, causing major accidents and losses. Therefore, the working voltage of the electric heating elements of the vacuum heat treatment furnace is generally no more than 80-100 v. At the same time, effective measures should be taken in the structural design of electric heating elements, such as avoiding the parts with tips as far as possible, and the spacing between electrodes should not be too small to prevent the generation of glow discharge or arc discharge.

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Experimental rules for students majoring in heat treatment

1. Before the experiment, we must carefully read the experiment instruction and be familiar with the purpose, principle, method and requirements of the experiment.

2. After arriving at the laboratory, we must strictly abide by the system and discipline of the laboratory and all operating procedures.
3. During the experiment, we should pay attention and do the experiment well. We should pay attention to cultivate our scientific attitude of seeking truth from facts and record the experimental data truthfully.
4. We must respect the guidance of the instructor, pay attention to personal safety and take good care of the equipment. In case of accident, report to the instructor immediately.
5. Take good care of public property and do not use other equipment except the instruments used in this experiment.
6. After the experiment, the experimental site and equipment must be cleaned up and restored to the original state. After the test records are sent to the instructor for inspection and signature, they can leave the laboratory with the consent of the instructor.
7. Test objectives and requirements, carefully analyze the experimental data, complete the experimental report, and send it to the instructor for correction within the specified time.

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Thermocouples are temperature measuring sensors

As a temperature measuring sensor, thermocouple is used to directly measure or control the temperature of fluid, steam, gas medium and solid surface in the range of 0-1800 ℃ in various production processes. The armored thermocouple has many advantages such as bending, high pressure resistance, fast thermal response time and durability. Like the industrial assembled thermocouple, it is used as a sensor to measure temperature, usually in combination with display instrument, recording instrument and electronic regulator.
Working principle of thermocouple
The electric couple is welded together with two different components of conductors. When the temperature of both ends is different, there will be thermoelectric potential in the circuit. Therefore, the potential electric couple is a kind of temperature sensing element which measures the temperature by measuring the electric potential. It is a kind of converter, which can convert the temperature signal into the electric signal and then display it by the display instrument.
The basic principle of thermocouple temperature measurement is thermoelectric effect. It connects the head and tail of two different components of metal conductors into a closed circuit. If the temperature of the two contacts is not equal, thermoelectric EMF will be generated in the circuit to form thermal current, which is thermoelectric effect. Thermocouples are made by welding two different metal materials at one end. The welded end is called the measuring end, and the unwelded end is called the reference end. The reference end is usually constant at a certain temperature (such as 00C) when heating the measuring end, there is thermoelectric potential at the contact. For example, if the temperature of the reference end is constant, the magnitude and direction of the thermal potential are only related to the characteristics of the two metal materials and the temperature of the measuring end, but not to the fineness and length of the potential couple. When the temperature of the measuring end changes, the potential and potential will also change, and there is a fixed functional relationship between the temperature and the thermal potential, so the temperature can be measured by using this relationship.
Thermocouple electrode is a circuit formed by welding two ends of conductor with two different components. The direct temperature measuring end is called the working end, and the terminal end is called the cold end, also known as the reference end. When there is a temperature difference between the working end and the reference end, a thermal current will be generated in the circuit. When the display instrument is connected, the corresponding temperature value of the thermoelectric EMF generated by the thermocouple will be indicated on the instrument. The thermoelectric force of the thermocouple will increase with the temperature of the measuring end. The thermoelectric force is only related to the material of the thermocouple conductor and the temperature difference between the two ends, and has nothing to do with the length and diameter of the thermoelectric pole. The structure principle of the thermocouple is that it is made of conductor, high insulating magnesium oxide and outer stainless steel protective tube, which are pulled together for many times. Thermocouple products are mainly composed of junction box, terminal block and thermocouple, and equipped with various installation and fixing devices.

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Four parts of medium frequency electric furnace

Medium frequency electric furnace is a common equipment in the field of heat treatment. It is mainly composed of four parts. Here is an introduction to the function of each part:
1. Power supply and electrical part: the power equipment includes high-voltage or low-voltage switch cabinet, intermediate frequency power supply (intermediate frequency generator set or thyristor converter), power conversion switch, compensation capacitor and intermediate frequency control cabinet (power distribution console in front of the furnace), etc., and the electrical part of large intermediate frequency furnace also includes crucible leakage alarm system.
2. Furnace body: medium and small medium frequency furnaces are equipped with two furnace bodies. One for production and the other for standby. Furnace body includes furnace cover, inductor, crucible, furnace body support, etc.
3. Transmission device: the transmission device includes mechanical or hydraulic devices such as the movement of furnace cover and the tilting and resetting of furnace body.
4. Water cooling system: the water-cooling parts include: intermediate frequency power supply (generator set and SCR frequency converter, in which the cooling water for SCR frequency converter needs to be softened), inductor, capacitor, busbar, flexible cable, etc. In order to save water, circulating cooling is usually used. Cooling water circulation system includes water pump, cooling tower, water tank, etc.


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Experimental rules for students majoring in heat treatment

1. Before the experiment, we must carefully read the experiment instruction and be familiar with the purpose, principle, method and requirements of the experiment.

2. After arriving at the laboratory, we must strictly abide by the system and discipline of the laboratory and all operating procedures.

3. During the experiment, we should pay attention and do the experiment well. We should pay attention to cultivate our scientific attitude of seeking truth from facts and record the experimental data truthfully.

4. We must respect the guidance of the instructor, pay attention to personal safety and take good care of the equipment. In case of accident, report to the instructor immediately.

5. Take good care of public property and do not use other equipment except the instruments used in this experiment.

6. After the experiment, the experimental site and equipment must be cleaned up and restored to the original state. After the test records are sent to the instructor for inspection and signature, they can leave the laboratory with the consent of the
instructor.

7. Test objectives and requirements, carefully analyze the experimental data, complete the experimental report, and send it to the instructor for correction within the specified time.

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