I. Overview
The heated metal or workpiece typically achieves the desired structure and properties through different cooling rates. Therefore, cooling, like heating, is one of the main processes of heat treatment. Similarly, cooling equipment is also one of the main equipment for heat treatment production.
The quenching and cooling equipment can be divided into cooling equipment, cooling chamber, quenching tank, quenching machine, cold processing equipment, etc. according to the cooling speed and cooling property of the workpiece during the cooling process.
The function of the quenching and cooling equipment is mainly to ensure sufficient cooling capacity when quenching metal or workpiece, or to prevent rapid cooling of temper brittleness after tempering. According to the different metal or workpiece materials and process requirements, the quenching medium of quenching equipment is divided into two categories: oil and water. Oil is divided into fast oil, high speed oil, super high speed oil, etc. according to the cooling rate; water is divided into inorganic Solutions and organic solutions, such as brine, PAG, etc., are separately preheated, cooled, circulated, stirred, etc. by some attachments to maintain their required cooling capacity.
Second, the technical requirements of quenching and cooling equipment
1. Provides the cooling capacity suitable for the process requirements for quenching.
2. The cooling rate is uniform and suitable for the process requirements.
3. Environmental protection and economy.
4. Safe and fireproof.
Third, the structure of quenching cooling equipment
1. Tank:
The trough body is generally welded from 3 to 12 mm steel plate, and the steel is used as a reinforcing rib to improve its strength and rigidity.
The base is made of steel and is easy to install and transport, especially for large quenching tanks.
2. temperature control:
The quenching medium is used in a certain temperature range. When the temperature is lower than the lower limit, heating is required, and when the temperature is higher than the upper limit, cooling is required.
(1) Heating device: The preheating methods for quenching media mainly include the following:
·Fuel heating, steam heating, electric heating
(2) Cooling device:
There are two main types of methods for cooling quenching media:
1 Replace the cooling method of quenching medium:
When the workpiece is quenched, the quenching medium with lower temperature is continuously injected into the lower part of the quenching tank, and the heated medium is discharged from the overflow trough in the upper part of the quenching tank, flows into a large underground special quenching medium storage tank, or adopts a centralized cooling method. Reduce the temperature of the medium and recycle it.
2 does not replace the quenching cooling method:
· Take the method of cooling by the four walls of the quenching tank to cool down. The speed is too slow to be used continuously.
· Add a stirring device to strengthen the flow of the quenching medium. The structure is complex and the effect is not great.
· A pipe with small holes is installed in the quenching tank, and compressed air is introduced, and the generated small bubbles act to agitate when floating, and the quenching medium is cooled. The disadvantage of this method is that the medium is easy to age; the chance of contact between the workpiece and the air is increased, the workpiece is easily oxidized; and the bubble is mixed in the quenching medium to reduce the cooling capacity.
• A serpentine tube is placed in the quenching tank, and flowing water is introduced into the serpentine tube to cool the quenching medium. Auxiliary facilities such as cooling towers need to be configured.
• Place the quenching tank into a larger tank and pass the flowing water. Auxiliary facilities such as cooling towers need to be installed, and the temperature is not easy to control.
3. Smoke exhaust device:
When the quenching medium is oil or other water-based medium, a large amount of steam is generated in the production due to the hot workpiece being placed in the quenching medium, which inevitably causes environmental pollution, deteriorates working conditions, and affects the health of the operator. Therefore, it is necessary to install a smoke evacuation device on the quenching tank.
There are roughly the following types of suction hoods for smoke evacuation devices:
·Integral groove side suction cover.
· Grouped slot side suction cover.
· Slotted groove side suction cover.
·Blowing suction side side suction cover.
4. Fire extinguishing device:
When the quenching medium is oil, the hot workpiece, especially the large workpiece, will increase the local oil temperature quickly during the process of entering the oil, and it is easy to cause the oil tank to catch fire. Therefore, it is necessary to equip the quenching oil tank with a fire extinguishing device. Commonly used fire extinguishing methods are:
· Cover and seal the fire.
· Fire extinguisher to extinguish the fire.
· Nitrogen fire extinguishing.
Fourth, the design of large quenching and cooling equipment
1. Slot structure
Large quenching tanks are generally square or round, with a volume of several to several tens of cubic meters, and large quenching tanks of up to 100 cubic meters. The trough body is welded by 6-12mm steel plate and surrounded by angle steel or channel steel. When the quenching groove is deep, the height direction should also be strengthened with steel, so that it has sufficient strength and rigidity to prevent deformation during transportation and installation. The base should have a base made of channel steel for easy transport and installation.
2. Setting of the quenching medium inlet:
Since the quenching groove is large, especially when the depth is deep, in order to ensure the uniformity of the quenching medium in the height direction, a plurality of inlets are arranged in the height direction of the trough, each layer is composed of several small holes, and the small holes can be at an angle Therefore, the liquid in the tank can flow vertically or horizontally or form a turbulent flow while rising, but eddy current should be avoided.
The cooling device is an air cooler. This method of cooling the quenching medium is a cooling method that does not replace the quenching medium, eliminating the need for a huge liquid storage tank. At the same time, the air cooler is small in size, small in area, water-saving, power-saving, direct air-cooling, and does not require traditional facilities such as pools, cooling towers and plate heat exchangers, and is easy to install and use.
3. Heating and cooling of the quenching medium:
In order to create a larger production space, the heating and cooling device of the quenching medium should be kept away from the quenching tank as far as possible, using separate heating and cooling devices. In this way, the quenching groove becomes simple and easy to repair.
The commonly used heating device is an electric heating box, which is composed of a tubular electric heater and a box body. According to the volume of the quenching tank, the heating power can be selected from 18KW, 24Kw, 36Kw, and the like.
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