What is the application of heat pipe air cooler, heat pipe heat exchanger in the process of carburizing and quenching medium temperature control?
The Heat pipe heat exchanger Replaces Water Cooling with Air Cooling for Cooling of Carburizing Quenching Oil This paper introduces the application example of heat tube air cooler cooling quench oil during continuous carburizing and quenching ；By actual test, quench oil tank temperature is 121 ℃, the heat tube air cooler air cooling refrigeration, back to the tank temperature is 79 ℃, air cooling temperature control is better than that of water quenching oil.
Heat treatment industry in the domestic research on heat treatment process, quenching medium cherished, and temperature and the cooling of quenching medium tend to be ignored, but because of inaccurate control of the temperature of the quenching medium, which finally impact on the microstructure and mechanical properties of the workpiece。Foreign developed countries invest a lot of manpower and money to study quenching medium temperature control, the degree of automation is higher, it is worth our reference. In this paper, the continuous carburizing and quenching of motor parts of quenching medium, the original used oil - cooling water heat exchanger, heat exchanger at the beginning of the surface is clean, the cooling effect is good, but after a period of time, due to reasons such as dirt on the surface of heat exchanger, the cooling capacity is greatly reduced, quenching oil temperature fluctuation is bigger, serious impact on the microstructure and mechanical properties of carburized parts。Also the biggest hidden danger is metal wall once somewhere corrosion leakage oil - water heat exchanger, leads to cold and hot fluid mixing, explosion danger, air cooler cooling quenching oil with water saving, power saving, easy operation, easy maintenance, long service life, safety, etc.
2. Carburizing and quenching process requirements.
（1）Carburizing and quenching equipment and workpiece.
VFE5/1（S）CN Multi-purpose box-type furnace；workpiece，20Cr camshaft (20CrMn gear shaft); The amount of each batch furnace charging ㎏, 800-1000kg
（2）carburizing and quenching process
Surface carbon content 1.003%, deep layer 1.8 ㎜, 1.6% carbon potential, continuous operation for 15 minutes from a number of artifacts。Carburizing temperature of 920 ℃, quenching temperature set 80 ℃, each batch of oil immersed in the oil temperature rose to 120 ℃, quenching oil required cooling back to the tank at 80 ℃ until the next batch of workpiece quenching.
3 The development of heat pipe heat exchanger.
（1）Principle of heat pipe
Heat tube is a kind of high heat conduction performance of the heat transfer element , he through of the evaporation and condensation in the vacuum tube to transmit heat, high thermal conductivity, good temperature resistance, heat and cold can be arbitrary change on both sides of the heat transfer area, heat transfer over a long distance, can control temperature and a series of advantages。Tube side heat absorption heat transfer fluid, and pass the heat tube working medium, medium after absorption of heat in the form of evaporation and boiling into steam, steam caused by the rise of differential pressure effect to the heat side, at the same time condense into liquid release of latent heat of vaporization heat to heat side fluid, condensing liquid relying on gravity to backflow to the heated side。
Because of the vacuum inside the heat tube, it is easy to evaporate and boil, and the heat tube starts quickly. The air cooler composed of heat tube has the advantages of high heat transfer efficiency, compact structure and small fluid resistance. The shell material is 20# cold drawn seamless steel tube,and the working quality is water - ethanol.
（2）Heat pipe heat exchanger
The tube bundle is composed of single tube heat tube, and the heating tube is inserted into the quench oil. Each sleeve is connected. The internal structure diagram of the heat tube air cooler is shown in diagram1.
High temperature quenching oil heating heat tube working medium by the phase change heat transfer for heat tube cooling, cold air transverse scouring heat tube cooling section of outside high-frequency resistance welding of spiral finned tube, heat dissipation area is large, the quenching oil heat diffusion into the air. Heat tube working medium repeatedly evaporation, condensation cycle, achieve the purpose of quenching oil cooling, heat tube air cooler, as shown in diagram 2
(3) performance characteristics of heat pipe heat exchanger
3.3.1 water saving, use air cooling, no cooling water consumption.
3.3.2 saving power, adopt the large air volume axial flow fan, the installed power is less than 1KV.
3.3.3 easy to maintain, because no longer use a lot of cooling water, avoid the original water cooling system to produce the scale and the freezing of the disease.
1. Heat pipe 2、clapboard 3、inlet tube 1、axial flow fan 2 fan connnection 3、 Heat exchanger body
4、 Quenching oil tube 5、spiral fin
3.3.4 Running safety, traditional oil - water cooler, cold fluid through the metal wall inside and outside in the heat exchange, once the metal wall corrosion leakage somewhere, will lead to the cold and hot fluid mixing, if high temperature quenching oil mixing water, produce water vapor will be in danger of explosion. And the heat tube air cooler, even if a heat tube fails, it does not affect other heat tube work, the air cooler still works normally.
3.3.5 Long life, because heat tube and cold and hot fluid heat exchange is only on the surface, by some processing on the outer surface of the heat tube, it can greatly improve the service life of the heat pipe heat exchanger
5. Economic benefit analysis.
(1) Reduce maintenance cost, save electricity and save water.
The case of carburizing with MKG multi-purpose furnace is presented, On average, the annual production of washing anode heat exchanger and air tower is 2.5 times. (including disassembly, cleaning and heat transfer, cleaning of water tower, water release, oil release, etc.), The labor cost and material cost of each treatment are 2800RMB. As for the indirect benefit loss of heat treatment workpiece waste is complicated and neglected. Maintenance cost: SW=0.28×2.5=7000RMB
save electricity, The output of the carburized parts per hour is 1000Kg. The original operating cost is 3.5kw. Pump power 4.5KW. Use air cooler to cancel the power 1.5kw of the secondary heat transfer pump, 1.1kw of the fan power, and the power consumption per hour: 3.5+4.5-(1.5+1.1)=5.4KW/h, The cost of saving electricity for the whole year (by 300 days) is. Sd=0.76×5.4×24×300=29.5thousand
The water cooling system is 0.36t per hour, and the annual water-saving amount is 0.36 * 24x300 =2592t.
Annual cost of water saving: SS=2.89 x 2592=7491 RMB, annual total cost saving: ST=SW+Sd+SS=0.7+2.95+0.75= 44,000RMB
Use the air cooler to invest 22thousand, the recovery period is: 2.2 to 4.4=0.5 years.