Thermocouple select for vacuum furnace

 Thermocouple select for vacuum furnace

Thermocouple temperature measurement at a specific vacuum: inexpensive metals, precious metals and refractory metal thermocouple characteristics, selection and application of tungsten-rhenium thermocouples detailed discussion of industrial classification, vacuum furnace for thermocouple configuration and installation, vacuum Profile factors furnace temperature accuracy, imports thermocouple localization studies, results showed: Domestic vacuum furnace for thermocouple can replace expensive imported thermocouple.

1. Introduction
Features common vacuum furnace, the temperature measured at a given degree of vacuum. As expected thermocouple accurate and reliable, long service life, we must better explore the factors that affect the accuracy of temperature measurement under vacuum: the vacuum, emissivity, thermal conductivity and thermocouple insertion depth. Therefore vacuum furnace for thermocouple choice is particularly important.

2, Thermocouple for vacuum furnace
2.1, thermocouple classification
International Organization for Standardization (ASTME344-08) thermocouple divided into three categories.
① standardized metal thermocouple; ② standardized precious metal thermocouples; ③ refractory metal thermocouples, a refractory metal thermocouple is defined as: Thermocouple unipolar material melting point higher than 1935 ℃, and thermocouple poles must be refractory metal or alloy.
2.2 Standardized metal thermocouple
Standardization inexpensive metal thermocouple, T, J, E, K and N type. When the vacuum furnace operating temperature below 1260 ℃, the choice of inexpensive metal sheathed thermocouple, K-type thermocouple temperature due to the poor stability, we recommend using the N-type sheathed thermocouples at 1300 ℃, can be a partial substitute for S-type thermocouple.
1) Ni-Cr-Si - Ni-Si-Mg thermocouple (N type) features
① high temperature anti-oxidation ability, good long-term stability;
② in the range of 250 ~ 500 ℃ good short-term stability of thermal cycles, and suppressing magnetic transition, no significant change in the thermal electromotive force;
③ in the range of 400 ~ 1300 ℃, the linearity of the N-type thermocouple thermoelectric properties better than K-type.
2) N-type thermocouple replace S-type thermocouple
Alternative S-type thermocouple with N-type thermocouple to measure the temperature of the heating element of the multi-purpose furnace (1180 ℃). Since 2008, five years,
Our company offers a total of 496 Ipsen N-type thermocouple replace S-type thermocouples, the total savings of 1.74 million yuan for the company. In 2012, for example, the company uses the N-type thermocouple 49, S-type thermocouples only four, indicating replaced with N-type thermocouple S thermocouple has exceeded 90 percent, the economic benefits is extremely significant.
3) The sheathed thermocouple selection
Rugged thermocouple and armored assembled into two categories. From saving metal materials, ease of use and reduce heat loss considerations, as far as possible sheathed thermocouple. Sheathed thermocouple material has the following main categories:
① armor materials in high-temperature region
In the temperature region of armor material is mainly 304,321 or 1Cr18Ni9Ti, while the high temperature area 310S, Inconel600, NiCr alloy. Experimental results show that: in 1000 ~ 1200 ℃ temperature range, with different casing materials, drift sizes, its rule is: NiCr <Inconel600 <310S drift ratio is 0.75:1:5.
② new high temperature sheathed thermocouple material Nicrobell
This alloy is added on the basis of Nicrosil chemical properties of magnesium and niobium, improved oxidation resistance and high-temperature strength of the alloy, with alloy Nicrobell new sheathed thermocouple. Fengdong AG for more than 1200 ℃ temperature zone, and achieved good results.
2.3, standardization precious metal thermocouples
Standardization precious metal thermocouple S, R and B type. In the range of 1260 ~ 1750 ℃, the choice of precious metal thermocouples.

Performance of vacuum sintering furnace is analysed and the structure

 Performance of vacuum sintering furnace is analysed and the structure

 May have you heard of vacuum sintering furnace, but you don't understand, in fact, sintering furnace is mainly used for ceramic powder, ceramic core and other zirconia ceramic sintering, sintered diamond saw blade, can also be used for copper, steel strip annealing heat treatment, etc. Next, a detailed analysis about the performance and structure of vacuum sintering furnace.
1, vacuum sintering furnace using wet glazed sintering bladder.
2, this is a kind of steel structure of the furnace, the 1050 grade aluminum silicate fiber as his main insulation material, thickness and high school in two temperature regions under 340 mm and 200 mm respectively, while the low temperature area, we adopt 100 k mineral wool felt, in addition we use 0.74 mm outside the furnace body in terms of appearance of color corrugated steel plate, the whole vacuum furnace is both beautiful and practical.
Circulating within three 8 units, whereas built-in screen, stainless steel fan can keep the mean temperature in the furnace (stainless steel fan screen blocking the role of the heat flow).
4, this furnace heater USES is corundum mullite tube, not only high temperature resistant, long service life, and low maintenance cost. In addition. Heater is to play the role of a keep the mean temperature in the furnace.
5, vacuum sintering furnace heating area can guarantee the products of 8 to 10 minutes of heating time, fully dissolve flat enamels, improve the quality of the products.
6, conveyor adopts flexible reliable and long life of high quality hanging chain, and the sintering and dry merged into a conveyor line, form a highly automated production.
7, vacuum sintering furnace roof hook is the high temperature heat resistant steel, safe and reliable
8, heater furnace is divided into 7-8 groups, each group can be individually climate-controlled, in order to further maintain mean temperature inside the furnace, the furnace can also be top and bottom temperature control respectively. In terms of temperature measurement, temperature furnace inner point up to 20, can fully control the furnace temperature.
9, product drying time in about 30 minutes, and the length and speed reached 60 m, about 25 s, make product fully dry.
10, vacuum sintering furnace structure, the special will waste heat recycling in the drying of the products, which can save a lot of electricity.

Vacuum sintering furnace working principle and structural function

Vacuum sintering furnace working principle and structural function

Vacuum sintering furnace is in a vacuum environment to be heated objects in protective sintering furnace, its heating mode is more, such as resistance heating, induction heating, microwave heating, etc. Vacuum induction furnace is heated objects to make use of induction heating protective sintering furnace, can be divided into the power frequency, medium frequency, high-frequency, such as type, can be ascribed to a subclass of vacuum sintering furnace. Vacuum induction furnace is under vacuum or protective atmosphere conditions, using the principle of intermediate frequency induction heating make hard alloy tool bit and all kinds of metal powder compacting sintering of complete sets of equipment, is for hard alloy, metal dysprosium, designed in the industrial production of ceramic materials.
For more than a, main structure and the composition structure under vertical and discharging. Its main composition is: the furnace body, vacuum system, water cooling system, pneumatic system, hydraulic system and front-rear institutions, base, workbench, induction heating device (tungsten heater and advanced thermal insulation material), into the electric device, medium frequency power supply and electric control system, etc.
Second, the main function after vacuum filling the hydrogen gas protection, control of furnace pressure and state of sintering atmosphere. Available optical fiber infrared radiation thermometer and armoured thermocouple temperature measurement (0 ~ 2500 ℃), and through the intelligent temperature control after comparing with the setup program, select the execution state feedback to intermediate frequency power supply, automatic control temperature and heat preservation program.
Tungsten, main principle and USES vacuum induction furnace is after vacuum filling hydrogen protection condition, by using the principle of intermediate frequency induction heating, the high temperature of tungsten crucible in the winding, by heat conduction to work on, suitable for scientific research, military units for hard metal such as tungsten, molybdenum and its alloy powder sintering molding.