2.2.3 Relevant examples: For the relevant examples, I chose one in the United States, one in the United Kingdom, two in Japan, and two in South Korea. I chose Changchun No. 1 Automobile Factory in China.
(1) The general-purpose GM's DELPHI Saginaw Steering Systems heat treatment workshop is the fifth plant heat treatment workshop of Detroit GM. The main products are the transmission and steering components of the car, such as semi-axle, cross shaft, steering knuckle, ball pin, etc., with an annual output of 2.5 million sets. The production equipment is 10 large-scale continuous gas carburizing automatic lines of Holcroft Industrial Furnace Company of the United States, of which 6 are heated by natural gas and 4 are heated by radiant tubes. The workshop is connected to the cold processing workshop, and the entire workshop is operated by only 8 people.
(2) British Bodycote Metal Technology Group is a world-wide professional metal service company, which is divided into four departments: metal heat treatment, hot isostatic pressing, metal coating and material testing service center. In Birimngham, UK, the division and the Aldrige division are engaged in heat treatment services. The Birimngham Division was established in 1991 as a more modern professional factory. There is a continuous production line of 7 multi-purpose furnaces controlled by Ipsen in 1992. Each multi-purpose furnace has a loading capacity of 1000kg. It is automatically controlled by a computer. It is continuously processed day and night, and all automatic control except for loading and unloading parts. The group realized the importance of world-class equipment for its services and invested £4 million. The division has been accredited by ISO9002 and UK BS 5750-2. It has obtained production licenses for aerospace industry, communications, automotive, precision engineering in Europe, Japan and the United States. Its staff of 31 people, the per capita annual output value of 73,000 pounds (1 million yuan / person-year). The cost of the carburized parts is 0.5-0.8 pounds/kg (7-11 yuan/kg). There are also three flow particle furnaces in this division, which are purchased from Schwing Company of Germany. The furnace temperature can reach 700~1100 °C, which can be carbonitrided and quenched, and the degree of automation is high.
The Aldrige branch is an older factory with relatively old factory buildings and equipment, and its working environment and manufacturing level are similar to those in our country. The equipment is a few old mesh belt furnaces and atmosphere furnaces, still in production. In addition, four ion nitriding furnaces (Φ2 m) are used to process the gears. There is also an ion coater and a chemical vapor deposition TiN for cold stamping dies and tools. The latter are more modern equipment.
(3) Japan Tosei Heat Treatment Co., Ltd., located in the Kobe Factory in Osaka, Osaka, was established in 1943. It is subjected to atmospheric furnace carburizing, no oxidation quenching, vacuum and high frequency induction heat treatment. The former is the use of periodic furnaces and continuous furnaces for heat treatment of automotive parts and other mechanical parts. Vacuum heat treatment is mainly used for bearing parts. The workshop achieved a flexible production system. The production line consists of 6 multi-purpose furnaces, 5 tempering furnaces, 1 oil-cooling tank, 1 water-cooling tank, 1 washing tank, 1 degreasing tank, 1 set of material preparation table, 1 set of material tray, and 1 turntable. One, one unmanned trolley, one set of two columns of 18-bit four-layer main frame. The company's workshop passed ISO9002 certification in July 1997.
(4) Hyundai Motor's Ulsan Plant, a car factory that produces cars and light vehicles. In the transmission workshop, the shaft and the gear are produced. The heat treatment is only arranged as a process on the processing line, and the parts are placed on the heat treatment fixture on the cold processing line. The heat treatment has 9 single-row continuous carburizing automatic lines. One of them is manufactured by HOLCROFT, USA, and the other eight are manufactured by Dongyu Heat Treatment Industry Co., Ltd. These 8 sets of equipment are exquisite and are typical of the small and exquisite Japanese style. The carburizing atmosphere used is propane plus RX gas, the highest carburizing temperature is 900 ° C, and NH3 is introduced into the quenching zone at 850 ° C to form a carbonitrided structure on the surface of the workpiece to improve the mechanical properties, and then quenched into a salt of 140 ° C. The bath is designed to minimize distortion, improve gear surface accuracy, improve life and reduce noise. The nitrate treatment is a feature of modern plants. Only 9 people on the 9 automatic lines walked around the equipment import and export, carried out equipment inspection and filled in the management of the process record card.
(5) The Yanyang Plant of Dongyu Heat Treatment Industry Co., Ltd. is a full-energy heat treatment production plant with 50 employees and a per capita annual labor income of 1.5 million yuan, which is very considerable. The factory is divided into three parts according to the process. The first part is the carburizing area. There are 12 sealed box type multi-purpose furnaces. The whole plate of the automobile and construction machinery parts are first cleaned on a double-station vacuum cleaner (instead of degreasing treatment). ), after entering the multi-purpose furnace for carburizing, the process is controlled by the computer, all the data is printed out, and the operator approves and fills in the checkpoint card. The 12 box furnaces are operated by one person. The second part is vacuum carburizing, nitriding, depositing TiN and infiltrating metal (vanadium). The equipment is a vacuum carburizing furnace, a cover type carburizing furnace and a metal infiltration type furnace. The products are tooling and high-demand parts. After the workpiece is processed, the metallographic phase, hardness, depth and deformation are strictly examined. The third part is the auxiliary process area before and after heat treatment, such as fixture, heat treatment, shot peening, straightening and cleaning of the loading box.
(6) The heat treatment workshop of the Changchun No.1 Automobile Plant chassis has self-manufactured a number of production lines based on the introduction and introduction of the double-row continuous carburizing and quenching line of Holcroft Company of the United States to meet the high-volume and high-quality production of gearbox and rear axle gears. To achieve the standard of heat treatment requirements of German golf cars, the uniformity of the layer is ±0.15mm, the carbon concentration of the gear surface fluctuates by ±0.05%C, the surface hardness uniformity is ±2HRC, and the process is adjusted by hot oil quenching. The press is quenched to control the deformation of the gear sleeve to a qualified range. The gear is subjected to combustion degreasing and pre-oxidation treatment in the sealed furnace before osmosis, which ensures uniformity of the carburized layer and also improves the problem of abnormal microstructure on the surface. The operating environment of the equipment is clean and energy-saving reaches the level of 356kwh/t energy consumption of the introduced furnace.
Here, I have listed both the advanced technology level and equipment status of foreign countries, and the situation of being listed in China's advanced enterprises is to let investment entrepreneurs benefit from it.
2.3. At present, the main heat treatment advanced technology and equipment
In the past 25 years, a large number of advanced new technologies for heat treatment have emerged. The main performances are as follows: (1) The heat treatment technology with little or no oxidation and less decarbonization in the protective atmosphere and control atmosphere is becoming more and more popular and perfect; (2) new technologies such as low pressure carburizing, controlled nitriding and surface modification are emerging; (3) Vacuum heat treatment and high-pressure gas quenching applications are expanding, clean production development greatly improves the environment; (4) energy-saving heat treatment and green heat treatment technology are developed; (5) heat treatment product quality and precise production are increasingly strict; (6) emphasis on sustainable development, environmental protection and governance; (7) computer Advances in application and control technology; (8) The level of automation of heat treatment operations continues to increase. The following is described by the process method or category.
2.3.1 Protective atmosphere and controlled atmosphere Heat treatment: Controlled atmosphere heat treatment is one of the main signs of advanced heat treatment production technology. The following 2.3.1.1 describes the status of advanced equipment and main control features, 2.3.1.2 to 2.3.1.5 indicate advanced process conditions.
2.3.1.1 Equipment and control characteristics: (1) At present, most of the heat treatment heating equipment adopts electric energy, which is convenient for operation and maintenance. However, from the perspective of energy utilization, the fuel furnace using primary heat source adopts advanced combustion technology and makes full use of waste heat, and the comprehensive thermal efficiency can be Up to 80%, Japan has a good application in this regard.
(2) Reduce furnace heat loss and furnace lining heat storage, make full use of waste heat to ensure furnace sealing.
(3) The pre-vacuum sealing multi-purpose furnace can eliminate the fire curtain, save fuel, shorten the exhaust time in the furnace, recover the carbon potential quickly, and improve production efficiency. (4) The furnace temperature is uniform and the atmosphere uniformity is high, which determines the product quality. Generally, the uniformity of the layer is ≯0.1mm, the surface carbon concentration is 0.05%C, and the hardness uniformity is <1.5 HRC. This requires that the furnace temperature of the effective heating zone is uniformly in the range of 5 °C and the furnace gas is fully circulated uniformly. (5) Using oxygen probe and programmable controller (PLC) carbon controller, the carbon potential control accuracy can be in the range of 0.05% C. The carbon black pollution and atmospheric infiltration of the oxygen probe will cause errors in its instructions. The Supercarb direct atmosphere control system of Ipsen, Germany, adds regular cleaning measures for the oxygen probe, and uses a compensation electrode and special alloy electrode to overcome this drawback. . (6) The equipment is reliable, and the mechanical action, electrical components, instruments, sensors and accessories are correct and reliable. (7) The quality of the furnace materials and process materials is good. (8) With fault self-diagnosis system, computer screen display, universal use of touch mode self-diagnosis system. (9) Some use two sensors when controlling the atmosphere with an oxygen probe, and monitor with a second probe or an infrared CO2 analyzer.
2.3.1.2 Direct-type carburizing technology: Directly introducing hydrocarbons and air into the furnace to obtain a controllable atmosphere of carbon potential is currently an important way to solve the problem of gas source.
The previous endothermic and exothermic atmospheres have furnace devices outside the furnace, and various direct atmospheres are used to directly inject fuel gas into the furnace to form the main components required for CO and H2 and CH4, although These important components do not reach the thermodynamic equilibrium, but can be controlled. Even if there is a high amount of CH4 in the atmosphere, the carbon transport is still controlled by the CO reaction. The stable carbon activity in this unbalanced atmosphere can be determined by the well-known equilibrium atmosphere equation: ac=K(t)Pco/Po20. 5
Here, the CO content is not constant, and it changes with the carburizing temperature and time. Therefore, an infrared atmosphere analyzer is required to measure the CO value, and the oxygen probe, the CO analysis value, and the temperature sensor value are input into the computer, and mathematical processing is performed on the basis of the above formula. It can control the carbon potential in a direct non-equilibrium atmosphere. Note that in the correct determination of oxygen potential, in order to change the original CH4 content <1% of the requirements, because CH4 will be as high as 2% to 10% or more, then the oxygen probe should use a special alloy electrode and add compensation electrolyte.
The tested set of atmospheres includes a direct injection of gas and an oxidizing gas into the furnace to create a direct atmosphere. The fuel gas used is: natural gas, propane, acetone, isopropanol, and liquid media such as ethanol, butane, diesel and kerosene can also be used. The other component can be air or CO2 and H2O. The carbon potential of the atmosphere is controlled by the amount of air injected, and the reduction of air flow increases the carbon potential. This furnace can be heated by gas and has a strong circulation.
It can be seen from the actual measured CO content and CH4 content that as the furnace temperature decreases, the reaction of hydrocarbons with air/CO2 decreases, which leads to more unreacted CH4, which results in carburization below 850 °C. At the time, a direct atmosphere using natural gas and air is not suitable; propane + air, acetone + air and isopropanol + air can be used below 800 °C.
The industrial furnace with a direct atmosphere can be used for carburizing, carbonitriding and quenching of various workpieces. Introduced to the United Kingdom in the early 1990s, after continuous improvement and application, about 300 sets of gas carburizing furnaces were put into operation in 1998.
Main advantages of direct-type atmosphere application: (1) short control time of furnace; (2) rapid and sensitive change of carbon potential; (3) good carburization uniformity; (4) low cost of atmosphere generation; (5) high carbon transfer rate; (6) high production efficiency.
However, it is applied to continuous furnace because the furnace temperature should be limited to 800 °C. In this case, the CO content in the furnace will be very low, but CH3OH can be additionally injected to decompose and maintain the CO content. Of course, the CO content is used to control the injection amount.
Straight-type carburizing equipment is divided into periodic sealed box furnace and direct-type continuous carburizing production line. The former has single-chamber and double-chamber furnaces, the latter has conveyor belt type, tray type, mesh belt furnace type or shock heart furnace type. There are also flexible production lines with cleaning, quenching and tempering.
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