Metal material cryogenic treatment technology (2) - cryogenic treatment equipment

3. Cryogenic treatment equipment

One of the key technologies involved in cryogenic treatment is how to obtain low temperature conveniently, quickly, inexpensively, reliably and controllably. Because the performance of the device directly affects the progress of the cryogenic treatment process. As with heat treatment, if the heat treatment process cannot be reasonably carried out, it is difficult to fully exploit the potential of the metal material, and it is difficult to achieve the purpose of improving the quality of the parts and prolonging the service life. The same is true for the cryogenic treatment process. In order to ensure that the cryogenic treatment technology has an expected effect on the treated material in practical applications, it is necessary to ensure that the cryogenic treatment process is reasonable. The smooth implementation of a reasonable cryogenic treatment process requires that the cryogenic equipment used meet the following requirements:

(1) High reliability and long service life;
(2) The temperature field is evenly distributed and the temperature rise and fall rate is controlled accurately;
(3) Less refrigerant consumption and cost savings;
(4) A wide range of machining workpieces.

At present, the cryogenic treatment equipment mainly has two forms, one is compressed air to cool, the minimum use temperature is -100 ° C, and the most commonly used cryogenic equipment is liquid nitrogen refrigeration, which is economical and convenient. The way of liquid nitrogen refrigeration can be roughly divided into the following two ways:

1. Liquid nitrogen immersion refrigeration: The workpiece is directly placed in a container filled with liquid nitrogen, the workpiece is quenched to liquid nitrogen temperature, and is kept at this temperature for a period of time, and finally rewarmed to complete the entire cryogenic treatment process. The pre-development of cryogenic treatment was carried out by liquid nitrogen immersion method for cryogenic treatment. Because this cryogenic treatment process is simple and convenient, it is widely used. However, the cooling rate of this method is relatively fast, resulting in excessive thermal stress, which is easy to cause tissue damage to the workpiece material, and the cooling rate of the workpiece material during the cooling process is uncontrollable, thereby affecting the adjustability of the process.

2. Using latent heat of vaporization of liquid nitrogen or low-temperature nitrogen cooling: The principle of using low-temperature nitrogen to achieve refrigeration is that low-temperature nitrogen is in direct contact with the material, and the temperature of the material is lowered by convective heat transfer, and the principle of utilizing the latent heat of vaporization of liquid nitrogen is liquid nitrogen. The temperature of the material is lowered by indirect means without direct contact with the material. In this way, refrigeration is divided into three types according to its heat transfer mode: (a) a system based on radiative heat transfer; (b) a system based on convective heat transfer; and (c) a combination of radiative heat transfer and convective heat transfer. system.

The cryogenic treatment equipment developed by the Institute of Physics and Chemistry of the Chinese Academy of Sciences uses the latest heating technology, temperature control technology and liquid nitrogen dispersion technology to make the process control temperature rise, constant temperature and temperature reduction uniform and stable. The cryostat has a minimum operating temperature of -196 °C, a maximum operating temperature of 200 °C, a temperature deviation of ±2 °C, and a rising and cooling rate of 1 to 10 °C/min, which can be adjusted not only automatically but also automatically. The cryogenic treatment device has the following characteristics:

1) The whole box is made of double-layer Stainless Steel; the stainless steel plate inside and outside the box is SUS304 stainless steel;
2) It can effectively block the cold and heat exchange inside and outside the box, and the heat preservation performance is good;
3) A sealing strip and a special door buckle are added between the box and the cover to ensure complete sealing and reliable locking;
4) Casters are installed at the bottom of the cabinet to facilitate the movement of the equipment;
5) Equipped with electrical interlock and alarm device to ensure safe use;
6) Flexible control mode: artificial intelligence control or computer remote control; computer control can realize central centralized control and remote control at the same time, complete real-time data acquisition, display, recording of cryostat temperature and calculate operation of artificial intelligence controller Control output, curve drawing, database saving, query and other functions, with dual functions of control and detection;
7) User-friendly computer operation interface, convenient for users;
8) The liquid nitrogen tank is connected to the cryogenic equipment by using a stainless steel vacuum insulated hose to reduce the liquid nitrogen loss to a minimum.

Introduction of different types of cryogenic equipment:

Fig.1 Appearance of horizontal program-controlled deep-cooling boxFig.2 Appearance of well-type program-controlled deep-cooling box Figure 3 Program-controlled deep-cooling box SLX-1000W Figure 4 Program-controlled deep-cooling box SLX-640

Effective size in the box: 1300×1014×1014 (mm3) Effective size in the box: 1000×800×800 (mm3)
Dimensions: 2220 × 2000 × 3800 (mm3) Dimensions: 2230 × 1200 × 3250 (mm3)

The two types of cryo-cooling boxes are equipped with cylinders, which cooperate with the chain to realize automatic opening and closing of the door.

Program-controlled cryostat SLX-32R

Figure 5 Program-controlled cryostat SLX-32R

This model-controlled cryostat uses a computer and touch screen control system for user convenience.

SLX-140W

The model-controlled deep-cooling box is a vertical double-opening door. The upper and lower boxes are separated by partitions in the box. They can be used when going up and down the box, or can be used in a single box, which is convenient for users to choose.

SLX-1500 large cold roll cryogenic treatment system

Figure 7 SLX-1500 large cold roll cryogenic treatment system

This model-controlled cryostat is a cryogenic equipment for large cold rolls. The two tanks of the cryogenic system can work simultaneously or separately. Convenient for customers.

Laboratory cryogenic treatment unit

Figure 8 Small cryogenic treatment unit for laboratory

4 Conclusion

Cryogenic treatment is a continuation of heat treatment of materials. The final performance of the material depends not only on the heat treatment process, but also on the process of deep cooling treatment and heat treatment and cryogenic treatment. With the development of modern industry, the requirements for the performance of materials are getting higher and higher. The major research trend of contemporary materials is mainly to greatly improve the performance of the existing traditional materials without changing the composition of existing materials, thereby effectively improving the utilization rate and recovery rate of resources and giving full play to the potential of materials. The material performance is improved while reducing costs and reducing environmental damage. Therefore, the research on cryogenic treatment of materials will become an important research direction for material science workers at home and abroad. One of the key technologies involved in cryogenic treatment is how to obtain low temperature conveniently, quickly, inexpensively, reliably and controllably. Therefore, future research on cryogenic treatment equipment and its industrial applications is of great significance.

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Metal material cryogenic treatment technology (1)

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