Nichrome is one of seven groups of precision (with specified properties) alloys, whose production is regulated by GOST 10994-74. This group includes 16 grades of metals with high current resistance, of which ten are used for the production of heaters and six for sensors and resistors with constant resistance in a given temperature range.
According to the mentioned regulatory document, the definition of nichrome includes the following alloy characteristics:
- maximum operating heating temperature – up to 1,100, 1,150, 1,200, 1,220 and 1,400 °C;
- resistivity – from 0.99–1.07 to 1.37–1.47 units;
- the basic elements of the chemical composition are nickel and/or chromium with a mass fraction of 55–78 and 15–23%, respectively.
On the Internet you can often come across the question of how to determine nichrome at home.
Let us say right away that it is impossible to do this by the appearance of the metal. To identify nichrome wire, you need to know the basic properties of these alloys. First of all, these substances are non-magnetic. If the permanent magnet does not attract the wire, you may have nichrome. This reservation is due to the fact that it is not the only non-magnetic alloy. If a current is passed through a nichrome wire, it will quickly heat up to a characteristic red glow, releasing strong thermal radiation.
A more accurate answer, including determining the grade of the alloy, can only be obtained using laboratory equipment. For this reason, the full characteristics of nichrome products must be indicated in the accompanying documentation, including their labeling and purpose.
How much does nichrome cost in Belarus?
Ready-made spirals UD regular ( nichrome
) 0.5 Ohm (10 pcs.) 10 rub.
Ready-made UD conventional spirals ( nichrome
) 0.5 Ohm (10 pcs.) 9 rub.
Interesting materials:
How does the wireless buttonhole microphone work? How does a wireless lavalier microphone work? How does Liquidless Barometer work? How does a bio toilet work on a train? How does boiler heating work? How does a magnetic field sensor work? How does the shock sensor work? How does the GLONASS fuel level sensor work? How does a diffuser work? How does the display port work?
What is nichrome wire and where can I get it?
In our country there will never be a shortage of “folk craftsmen”. Russian people have always been distinguished by their intelligence and ingenuity. Therefore, one of the questions that worries many inventors is where they can get nichrome wire in the required quantity. This material is a special alloy containing a high concentration of chemical elements such as chromium and nickel. In addition to them, nichrome also includes other metals - manganese, silicon, iron and aluminum, which have their own advantages, and their combination in one alloy creates a metal that has remarkable quality characteristics.
Where can I get nichrome wire?
There are several options for how and where you can purchase a nichrome product.
Today, in almost every locality there is a help desk for goods and services. By contacting it, you can obtain information from the operator about which organization sells nichrome and its contact numbers. This information can also be found on the Internet. However, in this situation, the chances of purchasing a normal product are practically zero , because if anyone undertakes to deliver the material, it will only be one and a half to two meters. Organizations mainly specialize in wholesale sales. But it’s still worth clarifying.
If such a product is sold in another city, then you can use it. However, this option requires additional payment for shipping. You can purchase wire in specialized stores. These could be “Radio Components”, “Skillful Hands” and other similar pavilions. The sellers of such private stores, who sell various spare parts, know each other very well. Therefore, if such a “private trader” does not have nichrome wire in stock, he can tell you where to purchase it. By the way, you can find it in an ordinary hardware store. Spirals for electric stoves are made of nichrome.
Not a single locality can do without a bazaar where you can buy anything. The most important thing is to carefully go around the entire market and you can even ask the sellers. You may also come across such a product made of nichrome.
find an old device somewhere , for example, a laboratory rheostat. In itself it is of no value, but it has a small amount of nichrome wound on it.
Nichrome wire is a high-quality plastic product due to its remarkable technical characteristics. Buying or getting it in any other way, although difficult, is possible. You just need to take the initiative and try all the above methods.
Source: elektro.guru
Advice from professionals
Experts consider the first switch-on to be one of the most significant moments on which the performance of the system being installed depends. Its algorithm is presented below:
- First day. The temperature controller is set to 20°C.
- Next 3 days. The temperature increases by 2°C every day.
- Fifth day. The heated floor is ready for full use.
If the installed equipment does not heat, then first of all the owner of the premises needs to check whether the cable is broken using a multimeter
When measuring resistance using this device, it is important to consider that it should not deviate by more than 5% from the values declared by the manufacturer. If there are serious discrepancies, there is only one solution left - to find damage or a break, “armed” with a device for searching for hidden wiring in the walls. Having found the problem area, you can begin to repair it (it is better not to solder, but to use a coupling that provides the most reliable connection)
Having found the problem area, you can begin to repair it (it is better not to solder, but to use a coupling that provides the most reliable connection).
Another common cause of underfloor heating malfunction is the temperature regulator, or more precisely, loosening of the contacts of its terminal block. To repair the device, just remove its front cover and carefully tighten the screw connections.
In conclusion, it remains to add that experts do not advise saving on the cost of purchased products. A cheap cable can quickly become unusable, which is explained by its low service life. Considering this circumstance, it is better to buy high-quality products from the top ones with the best reviews. Having made such a choice, there is no doubt that warmth and comfort in your home will be ensured, and for a very long time.
To see the difference between a heating cable and a heating mat, see the following video.
Soldering Features
The features of nichrome soldering are as follows:
- Use of tin-lead materials POS 50 and POS 1 for solder.
- Careful preparation of flux.
- Proper processing of the working surface.
Before soldering, the working surface is cleaned with sandpaper and treated with cotton wool soaked in an alcohol solution of copper chloride. Next, apply flux and begin the process.
When tinning nichrome with copper leads, it is better to use 2-3 g of citric acid. This is enough to service one wire. To remove acid, the wire must be placed on rosin, dipped, and a soldering iron is used for further work.
ATTENTION TO THOSE WHO WANT TO REGISTER ON THE FORUM. Problem activating your account? Write to (ignel(gav)mail.ru, ICQ 50389649), indicating your nickname and the address from which you registered. Don’t forget to look at the forum rules
Ignorance of the rules does not exempt you from responsibility! Don't forget to look at the TB Section. Knowing the rules can save lives. Have questions about using the forum? Look for answers in the FAQ (FAQ). There is a lot of useful information there. Looking for interesting materials? Guide to master classes from our forum members
- Artisan »
- Our works »
- We make it ourselves (Moderator: AndyAB) »
- Topic: How to distinguish nichrome wire by eye?
Author Topic: How to distinguish nichrome wire by eye? (Read 31354 times)
0 Users and 1 Guest are viewing this topic.
Among precision alloys subject to large temperature changes, nichrome occupies a special place. Due to its high heat resistance, its use is more justified in the manufacture of heating devices and key components of furnace equipment. The working material in this case is nichrome wire of a certain grade. Each of them differs in the percentage of various alloying additives, which allows, based on design performance indicators, to make a choice in favor of one or another sample, depending on its main quality characteristics, the main of which is the resistance of the nichrome wire.
Heat capacity, linear expansion, density and thermal conductivity of nichrome
The table presents the following physical properties of nichrome: specific heat at 25°C, average coefficient of thermal linear expansion in the temperature range from 20 to 1000°C and density of nichrome at 25°C.
It should be noted that the considered grades of nichrome have similar values of physical properties. The density of nichrome is in the range of 8200...8660 kg/m 3 and increases with increasing nickel content in the alloy. The coefficient of thermal linear expansion of nichrome at 20...1000°C has the value (17...18)·10 -6 deg -1. The specific heat capacity of nichrome, depending on the brand, is 440...460 J/(kg deg).
Specific heat capacity, linear expansion and density of nichrome
| Nichrome brand | C, J/(kg deg) | α·10 6 , deg -1 | ρ, kg/m 3 |
| Nichrome (10%Cr + 90%Ni) | 460 | 18 | 8660 |
| Х15Н60 | 460 | 17 | 8200 |
| Х20Н80-Н | 440 | 18 | 8400 |
| Nikrothal 80 | 460 | 17,2 | 8300 |
The thermal conductivity of nichrome is similar in value to the thermal conductivity of stainless steel. The table shows data on the thermal conductivity of the considered alloys at various temperatures in the range from 0 to 600°C.
The thermal conductivity of nichrome increases when heated. With increasing nickel content in the alloy, its thermal conductivity coefficient increases. For example, an alloy containing 10% Cr and 90% Ni has the highest thermal conductivity of the alloys considered, equal to 17.4 W/(m deg) at 20°C.
Peculiarities
First of all, it should be noted that the high popularity of the heating cable is due to its impressive efficiency. It converts almost all electrical energy into heat, allowing you to minimize losses and achieve optimal consumption of available resources.
If we single out situations for which underfloor heating is considered the best solution, then their list will look like this:
- use of cold coatings (optionally, ceramic tiles);
- high level of humidity in rooms (most often these are bathrooms);
- inability to connect to central heating (relevant for dressing rooms and hallways, as well as insulated loggias and balconies);
- the need to heat suburban real estate.
Another remarkable feature of floors equipped with a heating cable is the ability to install them under a variety of types of coverings. It’s enough just to get acquainted with the principle of operation and arrangement of such heating systems, as well as with their main varieties.
Types of products
The choice of any alloy that is characterized by high-quality technological and mechanical characteristics must be justified and regulated. Especially when it comes to high costs. Such a high-tech and expensive material is nichrome wire. GOST 8803-89, 12766.1-90, 12766.3-90, 12766.4-90 defines the requirements, features of marking and application. In accordance with the standards and depending on the type, the metal is presented for sale in the form of wire or strips, the choice of which depends on the diameter, cross-section, length, and features of use.
The corresponding rolled products are the starting material for the industrial production of zigzag tapes and wire spirals.
Decoding stamps
The properties and purpose of nichrome products are determined by their chemical composition. Let's look at the main ones.
- Х20Н73УМ-VI: chromium – 20%, nickel – 73%, aluminum – 3%, molybdenum – 1.5%, manganese – up to 0.3%, titanium – up to 0.05%, iron – 2%, carbon – up to 0.05%; melted using the vacuum induction method;
- ХН70У-Н: Cr – 27%, Ni – 70%, Al – 3%, Mn – up to 0.3%, Cs – up to 0.03%, Ba – up to 0.1%, Fe – up to 1.5% , C – up to 0.1%; designed for electric heating elements;
- ХН20УС: Cr – 20%, Ni – 20%, Al – 1%, Zn – up to 0.2%, Ca – up to 0.1%, Si – 2.5%, Fe – 50%, C – up to 0, 08% – for heaters of industrial furnaces.
Fechral heaters
Fechral heaters (FeCgAl)
“Fechral” (Fe-Cr-Al alloy) is a more advanced material than nichrome, widely used in resistance electric furnaces for all industries (mechanical engineering, foundries and heat treatment shops, ceramics and glass production, drying shops). Fechral heaters are used in electric furnaces up to temperatures of 1400 °C. They are an analogue of material A-1 from KANTHAL.
Advantages of fechral heaters compared to nichrome:
- the price is three times less, which ultimately leads to a reduction in the cost of the furnace;
- longer service life at the same operating temperature as nichrome (depending on operating conditions from two to four times);
- absence of scale, as a result of which the spirals do not need to be closed;
- longer service life in reducing atmospheres;
- higher specific surface power;
- lower density.
The combined effect of all the above factors leads to a significant reduction in the weight of the heater and, ultimately, to a reduction in its cost.
The plasticity of fechral increases with increasing temperature; at temperatures of 800-1000 °C, the alloys are easily deformed under their own weight, so heating elements must be installed on ceramic tubes. When heated to a temperature of 900-950 °C and above, rapid grain growth occurs, leading to irreversible embrittlement of the metal, so repairs of spirals are carried out with great care, without removing the spiral from the furnace.
At temperatures above 1000 °C, fechral can only work in contact with high-alumina refractory materials (with an aluminum oxide content of at least 50%). The performance of fechral is ensured by the protective film of Al2O3 formed on its surface, therefore, when working in non-oxidizing environments, this protective film must be periodically renewed by annealing in an oxidizing environment (in air).
Delivery form for fechral heaters:
- in the form of wire - fechral wire;
- in bays;
- in the form of spirals of various diameters, both on ceramic tubes and without ceramic tubes - fechral spiral;
- in the form of ready-made heating elements, equipped with current leads made of the same material, but of a larger diameter, with ceramic installation insulators and fastening fittings - fechral heaters.
ni-cr.ru
What is the value of nichrome wire?
Nichrome wire has the following valuable qualities:
- high heat resistance: nichrome is used in devices in which an element made of this metal can heat up to a very high temperature;
- not susceptible to corrosion;
- the strength and hardness of nichrome, mechanical stability, however, at the same time it is very elastic;
- high level of electrical resistivity and fairly low temperature coefficient;
- fairly light weight;
- remarkable resistance to a variety of aggressive substances.
