1, Tungsten- rhenium thermocouples metallurgical industry , powder metallurgy applications

metallurgy products usually in reducing atmosphere such as hydrogen production , the working temperature 1000 ~ 1800 ℃. Just using sintered corundum tube or pipe , materialized oxidation of tungsten rhenium thermocouple powder metallurgy plant in Xiangtan and other applications for many years.

2, Tungsten- rhenium thermocouples VN , manganese nitrogen, boron carbide and chromium -nitrogen alloy Si3N4 powder production application

currently about VN , nitrogen alloy chromium , manganese alloy production and nitrogen Si3N4 powder production process control, more mining materialized oxidation of tungsten rhenium thermocouples, 2003 in the amount of 500 above , access to users.

3, Tungsten- rhenium thermocouples nonferrous metallurgy application
application
in lead smelting process, in order to lead slag can be well separated , often using electric front bed of new technology, the sensor must be exposed to high temperatures , corrosive media. Testing environment is extremely harsh , resulting in a very short life platinum-rhodium thermocouple ( only two weeks or so ) , materialized oxidation of tungsten rhenium thermocouples can not only replace expensive platinum-rhodium thermocouple, but life is doubled.

4, Tungsten- rhenium thermocouples materialized oxidation of tungsten rhenium thermocouples application < / span>

in Chemical Plant pyrolysis furnace using tungsten- rhenium thermocouples replace platinum and rhodium even, at 1400 ℃ under a reducing atmosphere , the use of composite alumina tube to get good results.

5, Tungsten- rhenium thermocouples 1800 ℃ -2000 ℃ high temperature application

At temperatures above 1800 ℃ under the conditions currently only uses tungsten rhenium thermocouples. I am using the BN insulation, sintered tungsten tube , successfully used in 1800 ℃ -2000 ℃ vacuum furnace, there are many users.

6,Tungsten- rhenium thermocouples liquid steel temperature measurement application < span style = "font-size: 12px">

Under vacuum conditions , the use of metal-ceramic protective tube (Φ10 × 140 ~ 190) tungsten rhenium thermocouple batch temperature of molten steel in-line measurement , in order to meet the needs of a vacuum metallurgical production process .


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A tungsten rhenium thermocouples overview

Tungsten- rhenium thermocouples is high temperature thermocouples. It has the potential of a linear relationship between temperature , thermal stability , reliable, cheap, etc. . And display instrument for direct measurement of liquids , steam and gases such as temperature. It can partially substitute platinum-rhodium thermocouple as high metallurgical industry , high-temperature electronic thermoelectric systems and space vehicle structural engineering , ultra-high temperature nuclear reactors measurement tools .
Tungsten- rhenium thermocouples for temperature dependence of thermopower meet ZBN05003-88 indexing table , equivalent ASTME696-84 standards. In a vacuum , reducing , inert atmosphere , at 0 ~ 2300 ℃ range. The use of special protective tube tungsten rhenium even can at 1600 ℃ under oxidizing atmosphere, long-term use , its price is lower than the platinum- rhodium thermocouple .

Second, tungsten rhenium thermocouple temperature tolerance tungsten rhenium thermocouples

Temperature 1300 ~ 1700 ℃ Tolerance 0.5% | t |
0 ~ 2300 ℃ Tolerance 1% | t |

Third, temperature insulation resistance : tungsten rhenium thermocouples in the ambient air temperature of 20 ± 15 ℃, relative humidity less than 85% , the heat between the electrode and the outer protection tube insulation resistance should be greater than 100MΩ.m.

Forth , tungsten rhenium 3/ 25 tungsten rhenium thermocouple protection tube outer

( 1 ) silicon carbide tube (Sic) at 1600 ℃ oxidizing atmosphere using the following
( 2 ) molybdenum disilicide tube (Mosi2) at 1600 ℃ under air and some corrosive atmospheres ( supply agreement )
( 3 ) molybdenum tube (Mo) at 2300 C in vacuum using the following ( supply agreement )
( 4 ) tantalum tube (Ta) at 2300C using the following vacuum ( supply agreement )

Fifth , tungsten rhenium thermocouple indexing are: tungsten rhenium 3 - 25 tungsten rhenium , tungsten, rhenium 5 - tungsten- rhenium 26.


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Standardization of tungsten rhenium thermocouples are tungsten rhenium 3 - tungsten- rhenium 25 (D -type ) and tungsten rhenium 5 - tungsten rhenium 26 (C -type ) of two types, corresponding indexing are: tungsten rhenium 3 - tungsten and tungsten- rhenium 25 rhenium 5 - tungsten rhenium 26.

Tungsten- rhenium thermocouple wire quality performance standards described :

1 , Delivery specifications for diameter 0.1 ~ 0.5mm, diameter tolerance of ± 0.01mm;

2 , Even silk smooth surface, no oxidation, no bending, no glitches, mezzanine and splitting , allowing a small scratches , dents and a few spots ;

3 , According to the provisions sampling sampling test, the positive wire ( low rhenium ) and negative wire ( high rhenium ) at 1200 ℃ uneven thermal emf when no more than 80 microvolts (t0 = 0 ℃, namesake electrode method );

4 , At 20 ~ 30 ℃ ambient temperature , thermocouple wire diameter 5 times its own diameter shaft 5 laps wound surface without cracks, dual wire bent without breaking ;

5 , The temperature thermoelectric properties verification point : 100 ℃ (± 1 ℃), 1000 ℃ (± 10 ℃), 1200 ℃ (± 10 ℃), 1400 ℃ (± 10 ℃), 1600 ℃ (± 10 ℃), 2000 ℃ (± 10 ℃), or in consultation with users selected test temperature points ;

6 , Each batch furnaces have passed the type test .


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1 , the level of tungsten rhenium alloy products , specifications, use , temperature range, tolerance :

Level Specification (φmm) Operating temperature range (℃) ; The tolerance
Special 0.1 1400-1800 ≤ ± 0.128% t
Ⅰ 0.1; 0.5 ; 1200-1800 ≤ ± ; 0.25% t
Ⅱ 0.1; 0.5 ; 1200-1800 ≤ ± 0.50 % t

2 , the use of tungsten- rhenium alloy products : tungsten added 3 %, 5 %, 25 % and 26% of rhenium, tungsten rhenium alloy formation . Tungsten- rhenium alloy has good electrical properties and ductility and workability , can be used in high temperature thermocouple wire and the cathode wire.

3 , tungsten rhenium alloy general description of products and precautions :

①. Was extremely tungsten rhenium 3 ; tungsten- rhenium 5 . Extremely negative tungsten rhenium 25 ; tungsten- rhenium 26.

②. Temperature point : the cold end is 0 ℃, the hot side temperature 100,1000,1200,1400,1600,2000 ℃; φ0.1mm wire with 1554 ℃ palladium wire point calibration, in the form of pure platinum wire test 1769 ℃ Calibration .

③. Uniformity: Even when the wire unipolar head and tail at 1200 ℃ uneven potential ≤ ± 40 microvolts.

④. Flexibility: thermocouple wire annealing stabilized after six laps wound itself can not break.


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Tungsten- rhenium thermocouples is 1931 by goedecke ( Ge virtues g ) first developed out at 60 to 70 years to develop the most successful refractory metal thermocouples. Tungsten- rhenium thermocouple is characterized by: a high melting point hot wire (3300 ℃), vapor pressure, easily oxidized ; in a non- oxidizing atmosphere, good chemical stability. Emf , high sensitivity , the most important is cheap.

1 , tungsten rhenium thermocouples classification . Included in the national standards of tungsten rhenium thermocouples , there are two :

a, tungsten rhenium 5 - 26 tungsten rhenium , its positive nominal composition of 95% tungsten , 5% rhenium , tungsten cathode a nominal composition of 74% , 26% rhenium . Indexing number of wre5-wre26, abbreviated : w-re5/26.

b, 3 tungsten rhenium - tungsten rhenium 25 , its positive nominal composition of 97% tungsten , 3% rhenium , tungsten anode nominal composition of 75% , 25% rhenium . Indexing number of wre3-wre25, abbreviated : w-re3/25.

2 , the use of tungsten- rhenium thermocouples . Current measuring a temperature above 1600 ℃ , the use of non- contact method , however, the method of error is large , such as the contact law can accurately measure the real temperature . In the high-temperature thermocouples , precious metal thermocouples are expensive and the maximum temperature only in 1800 ℃ below, while tungsten rhenium thermocouple temperature limit is not only high, but good stability, therefore , tungsten rhenium thermocouples in metallurgy , building materials, aerospace , aviation and nuclear industries have been widely used . Rich resources of tungsten , tungsten- rhenium thermocouples cheap, can be partially substituted precious metal thermocouples , it is the high-temperature test promising field of temperature materials .

3, the use of temperature . Its maximum temperature can reach 2800 ℃, however , higher than 2300 ℃ , the data is scattered. Therefore , the use of temperature, preferably at about 2000 ℃ .

4 , the use of atmosphere. Easily oxidized tungsten- rhenium thermocouples , suitable for hydrogen in an inert or dry use , or dense protective tube isolated in order to use it with oxygen . Carbon-containing atmosphere can not be used ( as in the use of hydrocarbon-containing atmosphere , the temperature exceeds 1000 ℃ i.e. by corrosion) . Tungsten or tungsten- rhenium in a carbonaceous atmosphere is easy to form a stable carbide , that reduce the sensitivity and cause brittle fracture, in the case of the presence of hydrogen , is accelerated carbonation .

5 , tungsten rhenium thermocouples antioxidant . The issue has been a subject of concern to scholars at home and abroad , and is committed to study and solve . Our company adopts the international advanced making process , successfully developed a high temperature and pressure assembly type thermocouple w-re , the product temperature range of 0 ~ 1800 ℃, widely used in metallurgy , coking , chemical furnace , heat treatment, glass and other industries, it has a high accuracy , low price , stable performance, the work atmosphere free from restrictions , etc., instead of platinum and rhodium thermocouple is the ideal product. I produced the w-re thermocouple in Zhuzhou Cemented Carbide Works , Zigong Cemented Carbide factory and Shenyang Tech and other units, widely used, the performance reached the level of similar foreign products . Its technical indicators are as follows :

1 , sub-degree No. : w-re3/25, w-re5/26
2 , temperature range : 0 ~ 1800 ℃
3 , temperature measurement accuracy : <± 1% t; <± 0.5% t
4 , the time constant : ≥ 180 s
5 , insulation resistance :> 5mω
6 , Size : 300,500,750,1000,1100 (mm)

Tungsten- rhenium thermocouple temperature measurement of molten steel is designed for rapid measurement of molten steel , iron and other metals melt temperature was designed and manufactured , it has a volume of some  fast response , high accuracy and low price . Its technical indicators are as follows :

1, the maximum temperature temperature : 1800 ℃ .2, temperature measurement accuracy : ≤ 0.5% t.3, Insulation resistance : ≥ 30 mω.4, measuring the success rate : ≥ 98% .5, Response time: < ; 5 s.


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A Tungsten Rhenium Thermocouple Esther Fast Sex :

The melting point of tungsten- rhenium thermocouple wire in: 3120-3360 ℃, can be used up to 3000 ℃, it is the most high-temperature metal thermocouples. It has a high thermoelectric power , high sensitivity, insoluble in any separate acids, abundant raw materials in China , cheap, etc. .

Second, tungsten rhenium thermocouple fast product standards :

1, JB/T9496-99 tungsten- rhenium thermocouple wire .
2, JB/T9497-99 tungsten- rhenium thermocouple wire and indexing table ( equivalent to using U.S. ASTME696-84) standard .
3, JJG576-88 work with tungsten rhenium thermocouple test procedures .
4, JB/T5401-91 rapid measurement of the temperature of molten steel with tungsten rhenium thermocouple wire .
5, JB/T5402-91 rapid measurement of the temperature of molten steel with tungsten rhenium thermocouple wire , thermal EMF test methods .

Three , tungsten rhenium thermocouples product names and fast indexing :

1 , Name : Tungsten rhenium 3 - tungsten rhenium 25 ; tungsten rhenium 5 - tungsten rhenium 26.
2 , Sub-Degree No. : WRe3-WRe25 (D -type ); WRe5-WRe26 (C -type ).

Four , tungsten rhenium thermocouple products quickly grade , size, temperature range, tolerance :

Five , tungsten rhenium thermocouple wire insulation material :

1 , High purity alumina (AL2O3) can be used within at 1800 ℃ .
2 , Yttria (YO2) can be used within at 2000 ℃ .
3 , Beryllium oxide (BeO) at 2100 ℃ or less used, but toxic beryllium high temperature steam .
4 , Thorium oxide (ThO2) at 2300 ℃ or less to use, but has a weak anti- radioactive thorium .

Six , tungsten rhenium thermocouple wire outer protection tube :

1 , Tantalum tube (Ta) within a vacuum at 2480 ℃ use .
2 , A molybdenum tube (Mo) or less at 2300 ℃ vacuum and inert gas atmosphere of hydrogen used .

Molybdenum disilicide tube (Mosi2) or molybdenum silicide coating tube surface air at 1600 ℃ or less and some corrosive medium and long-term use .


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First,Fast Thermocouple Uses and Works

Fast thermocouple for measuring the temperature of molten steel and the temperature of the melt , the time consumption type thermocouple . Its working principle is based on the thermoelectric effect of the metal , a thermocouple temperature difference generated across the electric measurement of molten steel , and high temperature of molten metal .

Second, Product Specifications and Performance Comparison

Name Type indexing tolerance for temperature measurement time

Best Cap

Platinum and rhodium 30 - platinum and rhodium 6 KB-602P B ± 5 1500-1700 1750 4 ~ 6s
PtRh10 - Platinum KS-602P S ± 5 1400-1600 1650 4 ~ 6s
Platinum and rhodium 13 - Platinum KR-602P R ± 5 1400-1600 1650 4 ~ 6s
Tungsten- rhenium 3 - tungsten rhenium 25 KW-602P W ± 7 1500-1700 1800 4 ~ 6s

Third, the Structure

Fast thermocouple structure which is mainly composed of head temperature even large sheet of paper tube. There are positive and negative dual head thermocouple wire welded wire compensation , the compensation wire wear embedded in the bracket, bracket coat a small paper tube, thermocouple wire quartz support and protection. Outermost equipped with anti- slag cap, all components in concentrated load dump and refractory fillers bonded into a whole, and not removable , so for one-time use .


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Radiation shielding is a mass of absorbing material placed between yourself and the source of radiation to reduce the radiation to a level that is safer for humans.

The effectiveness of the material depends on the type of radiation itself, the properties of the material, and the shielding strength or thickness of that material.

Different types of radiation behave in different ways.

According to the NATO Handbook On The Medical Aspects Of NBC Defensive Operations, “Gamma or X radiation constitutes the principal casualty producing form of ionizing electromagnetic radiation associated with nuclear explosions“.

X-ray and gamma photons are essentially identical. The alpha particle however (another type of nuclear radiation from an explosion) while also highly dangerous but is hardly penetrable, and can be stopped by a single piece of paper for example (think of it as a heavy dust particle).

Gamma radiation travels at the speed of light. To protect yourself from gamma radiation resulting from a nuclear explosion, there are just three things to remember. Time, Distance, and Shielding. The first two are very common sensible. That is, get as far away as quickly as you can. Shielding though, requires knowing how much of what type of material is enough…

For radiation shielding, it’s mainly raw mass of material that makes blocking effective. The more shielding, the better. Shielding is measured by what fraction of gamma rays it blocks. If a certain thickness will block half of the incoming radiation, then adding the same thickness again will block half of what’s left (leaving only 1/4 or the original gamma ray intensity), and so on.

Materials are commonly categorized by their ‘halving thickness’, which is the thickness of that material required to block half of the incoming gamma rays.

An overall shield is characterized by its total ‘protection factor’. For example, a shield that only lets 1/1,000 (the modern day ‘acceptable’ amount) of the gamma rays through, has a protection factor of 1000.

To achieve a protection factor of 1,000 the following chart of materials and thicknesses must be used. We’ve saved you the trouble and have factored the proper ‘halving thickness’ values of each material in order to achieve the protection factor of 1,000.

As a rule-of-thumb, for a protection factor of 1000, you want about 375 pounds of mass per square foot of area you’re shielding (this is not a linear function, but this approximation is accurate for protection factor 1,000).

It seems to me that the most practical and economical means to achieve this protection factor is to use the absorption properties of packed dirt. So long as you’re at least 3 feet underground, you’re good to go…

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Tungsten alloy(heavy alloy) is ideal for shielding against X rays and gamma radiation. The very high density of tungsten shielding (more than 60% denser than lead) allows a reduction in the physical size of shielding components, without compromising their rigidity or the effectiveness of the shielding characteristics.
 
Tungsten heavy alloy shielding is used in applications such as collimator, nuclear shielding, beamstop,  syringe shield, vial shield, isotope container, FDG container, multi leaf collimator etc.

Here are some main applications for nuclear medical radiation shielding:

Whilst X-rays provide information on the structure of the body, PET shows the chemical function of a particular organism. PET involves the injection of FDG (a glucose-based radionuclide) from a shielded syringe into the patient. As the FDG travels through the patient's body it emits gamma radiation which is detected by a gamma camera, from which the chemical activity within cells and organs can be seen. Any abnormal chemical activity may be a sign that tumors are present.

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Effective radiation shielding is imperative to safe operation of modern Medical Cyclotrons producinglarge activities of short-lived radioisotopes on a commercial basis. Like the containment shielding of Medical Linear Accelerators , the optimal shielding design of Medical Cyclotrons demands a careful balance between the radiological, economical and often the sociopolitical factors. One is required to optimize the cost of radiation protection and the cost of radiological health detriment . The cost of radiation protection depends explicitly on the nature of the ionising radiation field produced by the cyclotron, its operational condition, the cost of
shielding material, the level of dose reduction, the projected net revenue from the from the sale of the radioisotopes, and the depreciation rate of the cyclotron facility. The mathematical methods of accelerator shielding optimisation  within the guideline of ALARA  have been reported by various investigators.

The important radioisotopes produced by Medical Cyclotrons for present day diagnostic nuclear
medicine include 201Tl (T1/2= 73.06 h) and67Ga (T1/2= 78.26 h). These radioisotopes are generated by bombarding the thick copper substrates electroplated with enriched parent target materials with 30 MeV protons at ~ 400A beam current. The target bombardments result in the production of intense fields of high-energy neutrons and gamma rays. Therefore, in order to avoid the radio-activation of the cyclotron, the ancillaries and radiation exposure to cyclotron workers and members of the public, the high performance target irradiation stations of modern negative ion Medical Cyclotrons  are housed in separate target vaults made of high density concrete. Thus, the efficient shielding of the target vaults plays the most important role in the radiological safety of the commercial Medical Cyclotron facilities.

The conventional optimisation method for the functions of multiple variables, such as the cost benefit-
analysis of Medical Cyclotron shielding design is too complex and prone to serious pitfalls. Hence, a new
method based on the Genetic Algorithm (GA) was used to solve this problem. The GA is a mathematical technique that emulates the Darwinian Evolution paradigm, also known as the “Survival of the Fittest” strategy.

It is ideally suited to search for a global optimum in a large multi-dimensional solution space, havingdemonstrated strength compared to the classical analytical methods. This paper highlights the application of an interactive spreadsheet macro program for the optimised shielding thickness calculation of the target vault of a Medical Cyclotron. The present optimisation method is based on a Genetic Algorithm search engine and runs on a Pentium 300 MHz Personal Computer in the Windows 98 platform.

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