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Bearing occupation needs for heat disposal equipment
Source: Bearing network time: 2013-12-30
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.1) Sanitary heat treatment Wastewater, waste gas, waste salt, waste oil and electromagnetic radiation, which are produced by heat treatment, will pollute the environment. Dispose of environmental pollution problems of heat treatment; implement sanitary heat treatment (or green heat treatment) It is one of the directions for the development of heat treatment skills. This raises high demand for heat treatment atmosphere, quenching oil and cleaning equipment.
.2) Fine heat treatment Fine heat treatment is sufficient to ensure the stability of the optimized process; the quality of the finished product is very disproportionate. è›æ‚–(4) However, it suffers from engraving and squatting. Disposal must have outstanding furnace temperature uniformity, temperature control accuracy; and excellent cooling and stability of the quenching agent. The fine heat treatment of the finished bearing can take the whole road of quenching and induction hardening.
.3) Energy-saving heat treatment Select new insulation materials to improve the power utilization rate of heat treatment equipment, optimize the heat treatment process; improve the process output value; and fully utilize the equipment's talents. All bearing manufacturers are doing experiments in this area; for example Absolute use of waste heat and waste heat; some manufacturers have used the residual heat of casting to spheroidize the bearing parts, and use a process with low energy consumption and short cycle to replace the process with long cycle and high energy consumption. The lower bainite quenching process is inevitable. Within a certain range; a shorter bainite quenching process replaces the carburizing process with long cycle and high energy consumption.
.4) Less oxidizing heat treatment is heated by a controlled atmosphere heating instead of an oxidizing atmosphere to control the carbon potential and nitrogen potential in a controlled atmosphere; the function of the parts is improved after heat treatment; heat treatment disadvantages such as oxidation, decarburization and cracking Such as large reduction; reduction of finishing allowance after heat treatment; improved data utilization rate and machining power. Vacuum heating gas quenching, vacuum or low pressure carburizing, nitriding, nitrocarburizing and boronizing can be obvious Improve workpiece quality; reduce distortion; improve life expectancy.
Second, bearing heat disposal equipment 1. Annealing equipment During the current period, the annealing equipment in China is the coexistence of oxidation furnace and atmosphere-maintaining furnace; the oxidation furnace is more than the atmosphere furnace, the cycle furnace and the continuous furnace coexist; and the cycle furnace is more than the continuous furnace. The United States, Britain, Japan and other countries are as early as 20 Pusher-type and roller-bottom isothermal spheroidizing annealing furnaces have been fully implemented in the 1960s and 1970s; shortening the annealing cycle; saving power; and improving annealing quality. Following the development of bearing parts processing skills; and fine casting and fine expansion ( Cold rolling) process selection; the processing precision of the parts blank is getting higher and higher; thus, the need to maintain the atmosphere annealing. The bearing profession should be agile to promote the atmosphere spheroidizing annealing; to reduce the oxidative decarburization after annealing; Processing power; energy saving; reducing costs.
2. Conventional martensite quenching tooling equipment During the current period, China's bearing professional practice martensite quenching tooling equipment is uneven; from the protection medium can be divided into unprotected medium oxidation furnace, controlled atmosphere furnace and vacuum furnace. The furnace accounts for about 25% of the heat treatment of the bearing; the non-oxidizing furnace with medium protection accounts for about 50% of the heat treatment of the bearing; the controlled atmosphere furnace accounts for about 20% of the thermal treatment of the bearing; the vacuum furnace accounts for the thermal treatment of the bearing. About 5%. From the production cycle can be divided into cycle furnace and continuous furnace.
In recent decades, the first meeting of martensitic quenching tooling equipment has been carried out in the following aspects:
.1) The active production line is currently available; the active production line selected in China can be divided into: according to its layout (or the movement method of the workpiece in the furnace): there are muffle belt furnace, no muffle belt furnace, casting chain furnace, Roller bottom furnace, drum furnace mesh belt furnace and rotary hearth furnace series production line; feeding, pre-cleaning, atmosphere protection (or controlled atmosphere) heating, quenching, post-removal (sometimes also carried out secondary deep-cooled roller hearth furnace The second deep cold and tempering are all completed actively. The production line is highly automated and the handling precision is high; the quality of the workpiece after treatment is uniform; the whole heat treatment production line can be used as a part of the bearing production line. Different heat The disposal line is suitable for the thermal treatment of bearing parts of different types and sizes according to its layout characteristics; for example, the mesh belt furnace is suitable for small and medium-sized bearing rings, the rotary hearth furnace is suitable for small batch bearing rings, and the roller hearth furnace is equipped with active Lifting and quenching equipment; suitable for bearing parts with large wall thickness, drum furnace is suitable for rolling body and small ferrule.
.2) Multi-purpose furnace can be carburized or carbonitrided under controlled atmosphere; it can be quenched under a controlled atmosphere; the process of non-oxidative quenching of finished workpieces. It is a cycle furnace; the first is suitable for small batches, Many types of bearing parts are heat treated.
.3) Induction heating quenching and tempering equipment induction heating has the advantages of fast heating speed, energy saving and small deformation; the workpiece after disposal has some functions that are not commonly used in heating. The current use of bearing heat treatment in China is mainly gathered in the slewing bearing And car wheel bearings; but not used on GCr15 steel.
.4) heating under vacuum condition of vacuum furnace can reduce or prevent oxidation of workpiece; cooperative high-pressure gas quenching can control the cooling and deformation of workpiece; prevent environmental pollution caused by oil quenching; complete hygienic heat treatment. Other; vacuum heat After disposing; the microscopic arrangement of the workpiece is more and more uniform; the outer surface and the core are arranged together; the hardness is uniform; it is beneficial to the improvement of bearing fatigue life. The vacuum furnace is mainly used in the heat treatment of special steel (heating temperature is above 1 000 °C) And some of the higher demanding GCr15 steel bearing parts quenching; in China's bearing heat treatment category is widely used. The development trend of vacuum furnace is ultra high pressure gas quenching instead of oil quenching; and the use of vacuum carburizing furnace to deal with new The use of steel in the bearing category.
.5) Quenching cooling medium and quenching medium can be divided into three categories: oil-based, water-based and gas quenching medium. Oil-based quenching medium is the most commonly used quenching medium. The usual quenching oil is used for N32 or N22 system loss. Oil; in order to improve its cooling function, anti-aging function, light function and high temperature function, etc., it is a series of refrigerants, scavengers, brighteners and antioxidants; it constitutes a series of fast oil, rapid glazing oil and high temperature grading isothermal oil. Quenching oil; quenching of bearing parts used for different scales and requirements; other; low volatility vacuum quenching oil. The disadvantage of oil-based quenching medium is that oil fumes in the quenching process constitute air pollution; Water pollution is formed during the process of cleaning up.
Water-based quenching medium is an aqueous solution composed of organic polymers, anti-corrosion agents and other additives. Different types of organic polymers can be modified to obtain different cooling characteristics; suitable for quenching cooling requirements of different bearing parts. During the cooling process; the organic matter adheres to the exterior of the part; the risk of quenching and cracking of the part can be reduced; and no fumes occur; the cleaning is convenient; no pollution; it is the development direction of the quenching medium.
Gas quenching is the use of inert gas as the medium (commonly used nitrogen); the compacted gas is sprayed onto the surface of the workpiece through specially painted nozzles; the quenching of the workpiece is completed. The pressure of the conditioning gas and the layout of the nozzle can control the cooling characteristics and deformation. Gas quenching is cleaner than water-based quenching; and the cost is lower; its key skill is the layout of the nozzle. China's gas quenching is still in the beginning of the bearing category; there is also a certain interval in the layout of the nozzle.
Quenching and cooling equipment is another major factor that affects the quenching effect of the workpiece in addition to the quenching medium. In China, the quenching and cooling equipment is equipped with fewer control parameters; usually only the oil temperature and oil circulation is controlled. Foreign countries apply multi-parameter control to the commonly used quenching oil tank. Such as oil temperature, oil cooling characteristics, oil circulation and mixing direction; and speed, workpiece oiling methods, etc.; in order to obtain the best quenching arrangement and function; together to minimize deformation. Bearing manufacturers are also testing multi-parameter control; in particular, the manipulation of the workpiece into the oil in the tapered bearing to deal with the change of viewpoint in the quenching process of the bearing parts.
Multi-station active quenching press has been used in China; but the degree of initiative cannot keep up with foreign countries.
.6) Removal of equipment removal is usually a necessary process after oil quenching. The cleaning equipment used in successive production lines usually ends with hot soap water soaking, water spray and hot air drying; and with oil and water separation equipment. Leading In the equipment; secondary cooling equipment (with refrigeration equipment; temperature between 5 ~ 10 °C); to reduce the content of retained austenite; improve the stability of the scale. The cleaning equipment is mainly selected by high-pressure cleaning liquid; this kind of cleaning is ineffective for non-through holes and small oil grooves; it often constitutes tempering oily fumes and pollution; sometimes it also constitutes a fire.
Vacuum cleaning is the cleaning equipment that has been carried out in these years. The advantages of this type of cleaning equipment are: the cleaning effect is good; especially the removal effect of the messy parts is more obvious; the surface of the workpiece is bright after cleaning, safe and hygienic; the cleaning liquid is clear water No addition of environmentally harmful chlorides and petroleum solvents, high degree of automation; and the use of cleaning heating instead of low temperature tempering; saving tempering costs. These years; ultrasonic cleaning, eddy current removal in heat treatment well.
3. Bainite austempering is based on the characteristics of bearing processing; the equipment used has two main categories: active production line and cycle furnace.
.1) Bearings with a small number of active production lines and large batch sizes are suitable for active production; for example, the production of railway bearings is mostly based on active production lines. The active production line is mainly composed of an atmosphere heating furnace and an isothermal quenching tank; some equipment used for austempering during austempering According to the measures of transporting workpieces, they can be divided into three categories: rotary bottom type, push-type type and conveyor belt type. The rotary bottom type and push-plate type isothermal quenching equipment developed by Ai Xierlin Company are used to organize the bottom or push plate. In the isothermal salt bath; the workpiece enters and exits according to a certain beat; recalls the order of control; the action is controlled by the PLC program. The degree of initiative of this type of equipment is high;
.2) Periodic austempering equipment rolling mill bearings due to various types, batches, ⌒驮岢 ⌒驮岢 Ъ Ъ å—–æŽ å—–æŽ å—–æŽ å—–æŽ + + + + æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ æ·¬ ; ; ; ; ; ; ; ; ; ; ; ; ; Slot. This equipment has less capital; it has strong applicability; but it has high labor intensity; poor safety. Currently; when bainite austempering is vigorously promoted; bainite austempering instead of carburizing steel is used for less loaded rolling mill bearings The above has been successfully applied in China.
4. The atmosphere and control are followed by the improvement of the quality requirements of the workpiece after quenching; the (controllable) atmosphere heating is more and more popular; the heat treatment including annealing is selected by the guaranteed (or controllable) atmosphere heating. 1970s; The first choice is the endothermic atmosphere. The endothermic atmosphere is a mixture of the feed gas and the air. Under the effect of the catalyst, some reactions constitute a kind of ?(CO) 18%~23%, ?(H2)37%~42%, The atmosphere of the balance N2; this atmosphere is also used in the field of bearing heat treatment in China. The nitrogen-based propane atmosphere is the most widely used in the heat treatment quenching line of China's bearing category; the composition of the nitrogen-nitrogen atmosphere and the endothermic atmosphere The nitrogen-based atmosphere represented by nitrogen-methanol is used more in the mesh belt furnace. In the 1990s, the gas production method of directly introducing air and hydrocarbons into the furnace above 800 °C is presented; that is, the direct atmosphere It was discovered through research that this atmosphere rich in high CH4 composition; although its gas response does not reach a balance similar to that of an endothermic atmosphere, its carbon transport can still be controlled by the content of CO and H2 in the atmosphere. Use an oxygen probe to contact the CO2 analyzer The potential control can be completed. The primary advantage of the direct atmosphere is that it saves a lot of material gas consumption; according to statistics, this atmosphere is still used in the continuous atmosphere furnace in the periodic atmosphere furnace; Up to 70%. Today; more than 300 sets of atmosphere furnaces around the world use this atmosphere for carburizing, carbonitriding and atmosphere quenching and other heat treatment. The direct atmosphere is used in China's bearing category. Carburizing category.
In recent years, the practical application has indicated that the service life of the oxygen probe is not well determined; the difference between the carbon potential measured by the oxygen probe and the practical value is also unpredictable. Therefore, the controllable atmosphere sometimes fails due to the failure of the oxygen probe. Control; constitutes the disadvantages of decarburization and oxidation. In China, it is often used to regularly check the accuracy of its measurement; it is not conducive to the complete activation of the furnace; sometimes it will affect the normal production.
In view of the above reasons; a two-layer measurement system has been developed abroad; one with a standard oxygen probe for normal control of the carbon potential; and another independent measurement system for detecting the operation of the oxygen probe; that is, the two systems are separated from the measurement atmosphere. The carbon potential; when the results show a large error; will alarm. The second measurement system operating component can be a CO2 infrared analyzer; can also be a miniature oxygen probe (λ probe). So far; there are many atmosphere furnaces Installed this two-layer measurement system.
Looking at the whole; domestic bearing heat treatment skills and equipment are still far from the developed countries; especially in the annealing equipment, the spacing is larger. The bearing heat treatment skills and equipment are also more spaced than other occupations; the quality of the bearing is related to the production of China. The revival of the industry.
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