The solutions to Vacuum induction furnace FAQ

The solutions to Vacuum induction furnace FAQ

 Vacuum induction furnace is an important device vacuum smelting. The key is used for smelting precision alloy, alloy steel, magnetic materials and high-temperature materials. Vacuum induction furnace, there are two: namely, intermittent and semi-continuous capacity of less than 150 kg of the furnace commonly intermittent, two capacities between 150-300 kg can be used, and capacity is more than 500 kg using a semi-continuous.
Staff at the time of using a vacuum induction furnace smelting, often encounter a variety of problems, today's vacuum furnace Ltd. Suzhou Joe on compiled some frequently asked questions, and also organize a number of methods to solve these problems, hope Consumers are able to have a little help, here together to understand under vacuum induction furnace FAQ What now.
1, vacuum induction furnace SPLASH
Vacuum induction furnace smelting such a problem at this time is mainly composed of two reasons: one is melting fast, the charge inside the exhaust gas is not sufficient, or that there is a problem in bridging the melting process, the lower part of the crucible of molten metal temperature is too high, chunks of cold material suddenly fall into the bath inside, this will cause splashing; the other reason is supplemented with the alloy material inside, a relatively high content of the gas, the added excessive speed, high temperature, had a chance to fully deflate it was melted into a liquid, and so are likely to cause splash. So for such a vacuum  furnace smelting problem how to solve it?
Solution: One way is to start from the preparation and loading of raw materials, on the choice of a suitable power supply system, careful operation in the melting time, avoid bridging situations, and supplemented with alloy material time, first bath down to a suitable temperature of molten steel, then slowly added to avoid splashing. Another approach is to take place after the splash, to the appropriate cooling, slow down the reaction, let boil slowly weaken. Have a big splash at the time, you can pass into the argon gas, reduce the degree of vacuum, increase the pressure inside the furnace, molten steel after pressing calm boiling, then continue evacuated.
2, vacuum induction furnace slag circle problems arise
Such problems arise when smelting is caused by two reasons: the crucible smelting long time, taking the process in constant spray of liquid steel, thereby forming a slag circle. Another reason is that the molten steel inside the gas content is relatively high, when rapidly evacuated slag formation lap.
Solution: There are three solutions, the first lap after the slag generated in the prepurge time, by increasing the load volume and front and rear tipping way to put out hot slag circle. Second, has left circle arc slag, can be treated by feeding baskets. Third, for large slag circle, as it has been the crucible of welding relatively solid, so it can be used to break the vacuum of the way, the direct use of fire to clear welding or welding.
3, vacuum induction furnace bridging problems arise
Bridging problems arise when smelting the following main reasons: charge too long; steel containing carbon monoxide in addition, when carbon monoxide board later joined, when the molten solder, which appears bridge; slag ring too large appears bridge.
Solution: There are three solutions: First, use a hammer hanging breaking open; second, tilting crucible with molten steel of the bridge parts hot start; third, to bridge serious, can be taken to break the vacuum processing.

How To Measure Vacuum Furnaces Temperature

How To Measure Vacuum Furnaces Temperature

Heating by direct radiation, the main heating mechanism in vacuum heat treatment furnace, tends to be a slower process than other heating mechanisms such as convection or conduction. As a result, there are times in the heat treating cycle, particularly during heat up, when the load will be at a lower temperature than the furnace hot zone. This is known as temperature lag. Hot zone temperature is controlled and measured through two (or more) thermocouples located close to the heating elements. One thermocouple, the control thermocouple, is connected to the thermal process controller which transmits signals to control the amount of power directed to the furnace elements.
The second thermocouple is known as the overtemperature thermocouple and is connected to the overtemperature safety controller. Both control and overtemperature thermocouples are also connected to the furnace datalogger to provide a permanent record of time and temperature data. These thermocouples ar platinum/rhodium combination known as Type S that retains accuracy under vacuum throughout a range between ambient temperature and 1480ºC (2700ºF). The location of these thermocouples within the hot zone is quite important in maintaining good temperature control and uniformity.
The recommended practice is to use at least three workload thermocouples. One should be buried deep inside the load. The second should be placed at a midpoint between the center and outside of the load. The third can be placed on the surface or outermost limit of the load. Normally, the center of the load will require the longest amount of time to heat to the processing temperature. By monitoring all three workload thermocouples via the datalogger, processing decisions can be made to ensure a sufficient soak of the entire load is achieved. VAC vacuum furnaces can also be programmed with a load guaranteed soak feature where signals from workload thermocouples to the thermal process controller ensure that the load automatically receives the full programmed time at temperature.
Workload thermocouples are usually attached directly to the load and connected to the vacuum furnace datalogger through extension cables. This makes it possible to record the exact time at temperature of the workload. Proper placement of these thermocouples will ensure the load receives the correct time at temperature by making adjustments for any temperature lag.
It's also popular for general heat treating applications. While these thermocouple types are not recommended for repeated use at high temperatures, they are less delicate and much cheaper than Type S and can be supplied in a flexible construction ideally suited for attachment to a variety of load configurations. The locations where workload thermocouples are placed in the load can have a significant effect on temperature indications.

Vacuum hot pressing furnace structure description

Vacuum hot pressing furnace structure description                           

Structure Description
1, furnace body : sandwich structure with double water, the inner wall 304 stainless steel polished, high-quality carbon steel outer wall.
2, the furnace lid: the use of double head sandwich structure, the inner wall 304 stainless steel, the outer wall is made of high quality carbon copper welding.
3,the vacuum hot pressureing furnace bottom: the same head with double water sandwich structure, water-cooled stainless steel head, intake valve; adjustable height, displacement sensor and electrode devices. All the inner walls are polished 304 stainless steel.
4, the vacuum furnace rack: upper and lower beams welded together two thick cylindrical columns, the upper and lower walls of the head support are welded products, high strength, high quality finish and balance.
5, the pressure head: the upper and lower pressure head with high purity graphite blocks pressed into production, the pressures 35-70MPa indenter
6, vacuum systems: one set by a mechanical pump, pneumatic valves, air release valve, vacuum valve, vacuum gauge (± Pa) and other components.
7. Hydraulic system: electric input mode, the instrument can be set to automatically adjust the pressure, and can achieve regulation, dwell.
8, the temperature control system: Silicon temperature can be controlled, configured with PID function instrument digital form, with over-temperature audible alarm.
9, cooling system: from a variety of pipeline valves and other related equipment components, with pressure-voltage, water audible alarm and automatic shut-off function.

Vacuum furnace heat treatment of operational processes

               Vacuum furnace heat treatment of operational processes

1. workpieces in a vacuum hardening, you should use a vacuum quenching furnace oil, this oil has a lower saturation vapor pressure.
2. Vacuum furnace maintenance should charge under vacuum or nitrogen status, avoid breathing normally when not absorb moisture.
3. Domestic vacuum furnace pressure rise rate should not exceed 1.33Pa / h, certain standards for foreign companies 0.67Pa / h
4. Vacuum furnace should have fast-cooling device. Cooling water pressure should be greater than 0.2Mpa, traffic should be adjustable.
5. processing titanium, should not use nitrogen as the cooling gas, because titanium and nitrogen at high temperatures, to form titanium nitride gold.
6. The cooling gas: steel commonly used 99.995% purity nitrogen, high temperature alloys using 99.999% nitrogen or argon, titanium using 99.995% argon.
7. The vacuum heating to radiation main piece in the furnace should be kept spacing.
8. The heating process, the workpiece material and the furnace will deflate the vacuum decreased.
9. warming: After you insert the workpiece, usually before the first pre-heating heat pumping to 6.67Pa
10. The heating temperature vacuum annealing furnace, vacuum annealing, vacuum and vacuum aging solution treatment temperature is generally the same as conventional treatment and heating.

Rolling bearing steel heat treatment methods

                                    

Rolling bearing steel heat treatment methods

 Heat Treatment generally includes heating, heat preservation, cooling three processes, sometimes only two processes of heating and cooling. The process is convergence with each other and can not be interrupted.
Heating is an important step of heat treatment. There are many ways for rolling steel heat heating process, the first is the use of charcoal and coal as a heat source, and then the application of liquid and gaseous fuels. Application of electric heating is easy to control, and no environmental pollution. With these heat source may be directly heated, can also molten salt or rolling bearing steel, as well as the floating particles indirect heating.
When the rolling bearing steel is heated, the work piece is exposed to the air, often oxidation, decarbonization (ie, reduce the carbon content of the steel parts of the surface), which parts of the surface properties after heat treatment have a very negative impact. Thus the rolling bearing steel should normally be in a controlled atmosphere or protective atmosphere, molten salt and vacuum heating, paint or packaging methods can also be used to protect heating.
The heating temperature is one of the important parameters of the heat treatment process to select and control the heating temperature, the heat treatment is to ensure the quality of the main issues. The heating temperature to be treated with the purpose of rolling bearing steel material and heat treatment vary, but are generally heated to a temperature above the phase transition, in order to obtain tissue needed. Further change will take some time, so when the rolling bearing steel surface to reach the required heating temperature, must at this temperature for a certain time, so that the temperature inside and outside the same, so the micro structure of the transition is completed, this time called the incubation period. When using high energy-density heating and surface heat treatment, heating fast, generally no holding time or the holding time is very short, and the holding time of chemical treatment is often longer.
Also a lack of cooling heat treatment process step is not available, because the process of cooling methods differ, mainly for controlling the cooling rate. General annealing cooling slowest cooling faster normalizing, quenching cooling faster. But also because of different grades have different requirements, such as empty hard steel can be used as cooling rate normalizing hardened.
Rolling steel heat treatment process can be divided into the overall heat treatment, surface heat treatment, local heat treatment and chemical heat treatment. Depending on the heating medium, heating temperature and cooling methods, each category can be divided into a number of different heat treatment process. The same kind of rolling bearing steel with different heat treatment process, available in different organizations, so as to have different properties. Steel is the most widely used industrial rolling bearing steel, and the steel micro structure is also the most complex, and therefore a wide range of steel heat treatment process.
Overall heat treatment of the work piece as a whole is heated and then cooled at a rate appropriate to change the rolling bearing steel heat treatment process its overall mechanical properties. Roughly the overall heat treatment of steel annealing, normalizing, quenching and tempering four basic processes.