How can you check stainless steel - Metals and their processing

How to identify stainless steel | Do it yourself

Stainless steel, or “sockeye”, as it is sometimes called, has qualities unique to this type of steel. It is possible to distinguish it from its “brothers” by subjecting it to some tests. This can be done by placing iron in a saline solution. You can resort to more difficult methods using physical calculations.

You will need

– magnet;
– table salt;
– water;
– needle file;
– emery;
– copper sulfate;
– a glass of water;
– spectrograph

Instructions

1. The most well-known method for identifying stainless steel is to evaluate how it interacts with a magnet. The composition of stainless steel allows it to “magnetize” only under the influence of Foucault currents. Under ordinary conditions, stainless steel is indifferent to the magnetic field.

2. Since, based on the name, “stainless steel” is stubborn to rust, you need to check it from this point of view. You need to make a concentrated solution of table salt in water. After this, place the steel product in it. The next day you can evaluate the result. A stainless steel product will not rust.

3. To check stainless steel for authenticity, you can use a needle file. This tool should be passed across the cut of the product several times. If yellowness appears on the ground surface, it means it is brass.

4. There is another test method. You need to remove a layer from the surface of the metal product using sandpaper. After this, apply copper sulfate to the “cleaned” surface. If the product is made of stainless steel, the color will not change. Any other metal will change color.

5. If a product, approximately made of stainless steel, has served for quite a long time, it is possible to determine whether it is sockeye salmon by appearance. Stainless steel is characterized by the absence of scaliness, i.e. peeling and breaks of the outer coating of the product. Products made from such material, as usual, retain their original presentable appearance for a long time.

6. In addition, traces of processing are visible on stainless steel products. In order to distinguish them, you will need a microscope. The more powerful its magnification, the more invisible the traces.

7. In order to finally make sure that a product is made of stainless steel, one should apply the knowledge of physical laws. One of them says: “a body placed in a glass pushes out water in accordance with what it was made of.

“You need to place a steel piece in the glass. After this, knowing how much the product itself weighs, calculate the mass of water poured out of the glass. After this, you need to compare the data with the tabular ones for stainless steel.

The result will be the result of the question about the material from which the product is made.

Tip 2: How to drill through stainless steel

In fact, the whole business has its secrets. Somewhere there are more of them, and somewhere smaller. So, sometimes without smart advice from knowledgeable people it is impossible to cope with any matter. Such difficult undertakings include attempts to drill through a layer of stainless steel. To say that this is unrealistically impossible, but without the skill of certain points you will hardly be able to do this the first or even the second time.

Tip 3: How to solder stainless steel

Stainless steel products are more difficult to solder than, say, copper. In order to achieve the desired result, you need to know several features of similar work.

Is stainless steel magnetic?

Among the main properties of a metal, the degree of magnetism is distinguished. Recently, there is simply a huge number of stainless steels, the performance characteristics of which can differ significantly. In many ways, the property under consideration depends on the chemical composition of the alloy. It is quite difficult to independently check the degree of magnetism, since it can vary depending on operating conditions.

Is stainless steel magnetic?

What determine the magnetic properties of materials?

To determine the magnetic properties of stainless steel and other alloys, a certain formula is used, which reflects the proportionality coefficient and magnetic susceptibility. Depending on the type of factor used, stainless steel falls into one of several groups:

When the coefficient is above zero, the material belongs to the group of paramagnets.
When using zero, stainless steel is diamagnetic.
Ferromagnets are characterized by good magnetic susceptibility. This group includes nickel, cadmium and iron.

Magnetic properties of stainless steel

Stainless steel becomes magnetic when exposed to a certain field. Such a reaction is associated with the structural features of the alloy, and to some extent, with the chemical composition. Some substances are characterized by reacting to the influence of a magnet.

Stainless steels with good magnetic properties

The magnetic properties of stainless steel largely depend on the structure of the material. They manifest themselves most in the following cases:

Martensite is characterized by good magnetic properties and is ferrimagnetic in its pure form. This kind of stainless steel is extremely rare, since it is quite difficult to maintain a pure chemical composition. Like conventional carbon versions, this one can be improved by hardening or tempering. This metal is widely used not only in industry, but also in everyday life. The most widely used brands are: 20X13 and 40X13. They can be subjected to mechanical action, grinding or polishing, as well as various heat treatments. Features of the chemical composition include an increased concentration of chromium and carbon. 20Х17Н2 is another stainless steel, which is characterized by a high concentration of chromium. Due to this, the structure becomes more resistant to moisture and some aggressive agents. Despite the large number of alloying elements, spain is weldable and can be hot or cold forged.
Ferrite, depending on the degree of heating, can take two forms: ferromagnetic and paramagnetic. The chemical composition of such materials contains less carbon, making them softer and easier to process. This group includes stainless steel 08Х13, which is actively used in the food industry. In addition, this group includes AISI 430, which is used in food production plants.
Martensitic-ferritic alloys are characterized by very attractive performance properties. Alloy 12X13 has a similar structure. Like previous metals, this one can be subjected to mechanical and thermochemical processing.

Steel 20Х13Steel 40Х13

The above information indicates that the martensitic structure has the most pronounced magnetic properties.

When choosing an alloy, it should be taken into account that not all stainless steels are resistant to mechanical damage. Even minor impacts can damage the surface layer. Despite the fact that the chromium film can be restored upon contact with oxygen, new alloys have been produced that are characterized by increased mechanical stability.

Another classification of metals involves their division into the following groups:

Highly resistant to acids.
Heat-resistant version
Food grade stainless steel.

Heat resistant stainless steel

Material marking is carried out using alphanumeric designations. Each symbol is used to designate a specific chemical element, the number indicates the concentration. Other countries have their own specific standards for naming metal.

Non-magnetic stainless steels

There are quite a large number of metals that do not have magnetic properties. They contain nickel and manganese. The following groups of alloys are distinguished:

Austenites are the most widely used. This group includes 08Х18Н10 and 10Х17Н13М2Т. These metals are actively used in the manufacture of various products in the food industry, for example, cutlery and dishes. Increased corrosion properties are maintained in almost any operating environment.
Austenitic-ferritic stainless steels 08Х22Н6Т and 08Х21Н6М2Т are characterized by an increased concentration of chromium and some other alloying elements. To change the basic characteristics, other chemical elements are also included in the composition.

Steel 10Х17Н13М2ТSteel 08Х18Н10

Non-magnetic stainless steel is selected when the resulting product should not respond to the influence of a magnetic field.

The choice of stainless steel can be made not only taking into account the degree of magnetism, but also the following points:

Weldability. Some versions need to be preheated, others weld well even when cold.
Ductility is taken into account when choosing a material for cold and hot stamping. A sufficiently high ductility index determines that it is possible to stamp metal sheets in a cold state.
Corrosion resistance when exposed to high temperatures. Many metals lose their characteristics when exposed to strong heat, including corrosion resistance.
Price is also an important factor. Metals can have high performance characteristics, but due to their high cost, their use for the production of some products is impractical.
Degree of machinability. Often, workpieces are supplied for cutting on special equipment. Due to the high concentration of carbon, hardness increases and the surface treatment process becomes more complicated.
Heat resistance is also an important quality that is considered when choosing a material. With good heat resistance, the manufactured product does not lose its strength and hardness when exposed to high temperatures.

Some brands are subjected to heat treatment, which increases the strength and hardness of the surface.

When tempering is carried out, the structure becomes more plastic and resistant to variable loads.

As previously noted, it is possible to determine whether stainless steel is magnetic without the use of special equipment. Among the features of the procedure, we note the following points:

The test area should be polished to a high shine. Hand tools and special materials can be used for this.
A few drops of concentrated copper sulfate are applied to the cleaned area.
If the metal is stainless steel, then a red coating will appear on the surface.

Determination of magnetic properties using vitriol

This process allows you to determine which stainless steel is magnetic and which is not corrosion resistant. It is almost impossible to determine the characteristics of a food alloy on your own.

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Magnetic properties can also be checked using a regular magnet. However, it does not give an accurate result.

That is why it is recommended to purchase products from reputable manufacturers.

Portable metal analyzer

In conclusion, we note that magnetic properties do not in any way reduce the corrosion resistance of the surface. That is why such alloys are characterized by a wide range of applications.

Source: https://stankiexpert.ru/spravochnik/materialovedenie/magnititsya-li-nerzhaveika.html

How to identify stainless steel at home

31.10.2017 16:13

The material in question presents ten ways to distinguish aluminum from stainless steel. Some of them are very easy to use at home, without having absolutely any tools, equipment or chemicals. This will allow you to quickly and accurately determine the value of a particular item (product) made of aluminum or stainless steel.

1. Magnet

Unfortunately, it is not always possible to reliably distinguish these two metals from each other using a magnet. The fact is that any brand of aluminum, one way or another, does not stick to the magnet. But not all stainless steel has the same property.

If the product under study is magnetic, then it is definitely not aluminum. The sample may refer to stainless steels that contain sufficient amounts of nickel. If copper or chromium predominates in stainless steel, then it will not react in any way to a magnet.

2. Marking

As a rule, some stainless steel products have appropriate markings that allow you to accurately identify the item being examined. In this case, everything is quite simple. Inscriptions like “STAINLESS” and other similar ones are a clear sign that this is definitely not aluminum.

3. Plain paper

One of the easiest ways to determine the difference between aluminum and stainless steel. For the experiment you will need a sheet of plain paper. It must be white paper. The one used for printer printing is suitable. The denser it is, the better for the business.

The essence of the experiment is as follows. First, you need to clean the edge of the product under study from dirt, grease, oils and other deposits. Next, you need to move this place along a sheet of white paper. The pressing force should be as strong as possible. It is very easy to draw conclusions. Stainless steel on a white sheet will not leave any marks, while aluminum will show thin stripes of gray color.

4. Metal color

Another criterion that more or less clearly distinguishes stainless steel from aluminum is the shade of the product in question. If we have stainless steel in front of us, then its surface, as a rule, has a shiny, colorless tint. However, over time this condition persists.

If we consider an aluminum product, then the color of its surface is usually matte (this metal is difficult to polish to a glossy shine), gray or whitish. After processing with sandpaper, the sanded area will quickly become covered with an oxide film and become dull.

5. Mechanical loads

This is also a fairly simple method that can be done at home. Its essence lies in the fact that the product under study must be hit against a solid metal object. To obtain a more accurate and visual result, this should be done in the dark.

If the product is made of stainless steel, then we will see quite pronounced sparking upon impact. It can be seen even in dim lighting. In the case of aluminum, there will be no sparking, even if you look very carefully in complete darkness.

6. Thermal conductivity and melting

In the case of various containers, metal can be determined by heating. So, in an aluminum pan, ordinary water is brought to a boil quite quickly. Under the same conditions (volume of water, heating) in a stainless steel container, this process takes much longer. This is due to the fact that the thermal conductivity of aluminum is many times better than that of steel.

The melting point of aluminum is about 660°C, while for stainless steel this indicator is beyond 1800°C. When using a conventional gas burner, which is used as camping equipment, it is quite easy to reach a temperature of 700°C. This means that it is also possible to melt a small aluminum object on such a fire. Stainless steel cannot be melted under normal conditions (without pressurization and oxygen supply).

7. Copper sulfate

An excellent and quite affordable option for determining aluminum or stainless steel is to expose the metal to a solution of copper sulfate. It is sold in agricultural stores at a low price. When processing this material, cloudy marks and stains will certainly remain on aluminum. Vitriol has no visible effect on stainless steel.

8. Lye

Alkaline solutions are also quite accessible today, and help to easily distinguish between these two metals. It can be sodium or potassium hydroxide. As in the case of vitriol, aluminum reacts to treatment with alkali, as a result of which brown spots remain. If the product being examined is made of stainless steel, we will not find any visually visible traces.

9. Acid

For a successful experiment, a solution of citric acid or lemon juice will be sufficient. A more pronounced result will be obtained when the metal is exposed to more aggressive acids. The essence of the definition is the same as with vitriol and alkali. External processing will leave stains on the aluminum surface. Stainless steel does not react with acids.

10. Density

The longest and most difficult way to distinguish the two metals in question is to determine their specific density. This is only applicable for small products, as well as for those that have a regular geometric shape. The bottom line is that you first need to calculate the volume of the sample under study, and then, using a simple formula, find out its specific gravity.

The result obtained is ultimately compared with fixed density values. For aluminum this figure is about 2.6 g/cm3, while stainless steel is almost three times denser - from 7.6 to 8.1 g/cm3.

Source: https://masakarton.com/kak-opredelit-nerzhaveyuschuyu-stal-v-domashnih-usloviyah/

Checking the quality of stainless steel

After manufacturing, any product undergoes mandatory quality testing. Rolled stainless steel is also no exception. For this purpose, there is a whole series of sequential measures where certain parameters of stainless steel are checked for compliance with the requirements for metal products. The work is carried out according to the instructions, which are at the disposal of the technical control department (QCD).

Stages of testing a stainless steel batch

Comprehensive testing of the characteristics of stainless steel, both visually and with the help of special laboratory tests, allows us to guarantee the quality of rolled products and metal products that are made from it:

First of all, the accompanying documentation is checked. Stainless steel is marked indicating the grade of steel from which it is made. The marking is placed along the edge if the stainless steel was made in sheets, or at the end if the steel is round (coil or strip).
During a superficial inspection, special attention is also paid to the absence of layers, burrs, marks and other defects in the material.
In addition, the rental must comply with the nomenclature specified in the accompanying documents and have a passport and quality certificate.
Depending on the type of rolled metal, it is checked for compliance with the shape. Sheet material is checked for unevenness and deflection, round material is checked for bending, ovality and spiral. The dimensions of stainless steel metal products are also checked - metal thickness, sheet dimensional accuracy, tape width and other parameters.

Next, the characteristics of the metal are checked and its compliance with the standards and requirements of GOSTs.

Testing in laboratory conditions

At the second stage of quality control, laboratory tests of stainless steel are carried out, which make it possible to determine the chemical composition of the material. Of particular importance when monitoring the quality of stainless rolled products is checking the percentage of carbon content, on which the strength and reliability of the metal depends.

For this purpose, a spectral analysis of its chemical composition is carried out. The fact is that exceeding the carbon norm in stainless steel leads to a breakdown of the dense structure of the steel. As a result, the material becomes fragile, and microcracks and defects appear on the surface.

During processing, the unsatisfactory condition of rolled metal is aggravated, which leads to premature destruction of the metal.

Depending on what metal products stainless steel is intended for, additional research is carried out. For example, for stainless steel, which is used in the production of metal products in the food industry, an additional check of the chemical composition is carried out. In such material the presence of impurities and additives that can cause harm to human health or life is unacceptable.

For rolled metal products intended for use in conditions of high humidity, tests are carried out to determine the metal's resistance to corrosion and aggressive environmental conditions.

Source: https://www.globus-stal.ru/articles/proverka-kachestva-nerzhaveyushchego-prokata/

How to test stainless steel at home

Considering the fact that stainless steel today is produced in a wide variety of brands, it is impossible to unequivocally answer the question of whether it is magnetic or not. The magnetic properties of stainless steels depend on the chemical composition and, accordingly, on the internal structure of the alloys.

A portable metal analyzer allows you to quickly determine the content of chemical elements and make a conclusion about the quality of stainless steel

How to Determine Whether Magnetic or Non-Magnetic Steel is Stainless

Considering all of the above, we can draw the following conclusion: even if steel has magnetic properties, this does not mean at all that it cannot be classified as a stainless-type alloy.

There is a fairly simple way to check whether magnetic steel is stainless steel.

In order to determine this, it is necessary to clean the surface area of the product being tested to a metallic shine, and then apply a few drops of concentrated copper sulfate to this area.

The fact that this is stainless steel is indicated by a coating of red copper that covers the cleaned area. This simple method allows you to very accurately determine whether magnetic steel is stainless. But it is almost impossible to check (and especially determine at home) whether stainless steel belongs to the food category.

If you decide to check whether magnetic steel is stainless or not, keep in mind that its properties, such as the ability to magnetize, do not in any way impair its corrosion resistance.

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Source: https://respect-kovka.com/kak-proverit-nerzhaveyku-v-domashnih-usloviyah/

How to test stainless steel at home? — Handyman's Handbook

This resource will help clear up any confusion about how to identify different types of metals! First, always have a magnet handy. It's better to have several magnets. Microwaves, speakers, hard drives, and other electronic devices all have a magnet in them that you can pull out. Another great way to identify metal is the spark test.

Using a magnet, you can identify and sort ferrous and non-ferrous metals.

Iron/steel

3 times heavier than aluminum
Rusting
Has magnetic properties
There's a lot of it
Durable

Aluminum

Light
Does not have magnetic properties
Does not throw sparks from the grinder
Does not rust

Copper

Mainly used in wiring and electronics
Large utensils are made from it
When copper is pure it has a beautiful pink color.
When tarnished, it is usually red or brown in color. (Also beautiful)
Oxidizes and turns green
Denser than iron, approximately 15%
The brighter the copper, the more valuable it is
Copper No. 1 pure copper, including pipes without solder joints
Copper No. 2 copper with soldered joints

Copper scrap: motors, transformers, chokes, some processors and so on.

Brass or bronze

Typically yellowish in color and worth about half the price of No. 1 copper
May be called brass or bronze, "copper alloy" to avoid confusion
Often found in the form of pipe valves, decorations
Maybe alloyed with nickel, in which case it is called "nickel silver" (see below)

Copper wire grades

There are many different ways to classify copper wire, but it all comes down to the percentage of copper content.

85% Wire: the diameter of a pencil. If you have this type of wire, you will get the best price for it
70% Wire: wires without any insulation
50% Wire: Extension cords and appliance cords with insulation removed
30% Wire: Thin wires in a bundle with insulation

How to determine lead

One and a half times denser than iron, feels heavy
It is atomic element 82 with the chemical symbol Pb, is very malleable, or soft, and can be cut with a pocket knife
Melts at low temperature
Used to make bullets and X-ray machines
Very toxic

How to identify 304 stainless steel

304 stainless steel is an alloy of iron with 18% chromium 8% nickel
Does not have magnetic properties
Use a spark test

How to identify 316 stainless steel

Does not have magnetic properties
It is an alloy of iron with 18% chromium and 10% nickel
Looks exactly the same as 304
When using a spark test, there will be fewer "forks" at the end of the flow
Use a portable spectrometer for accurate determination

How to identify 200 stainless steel

It is an alloy of iron with 17% chromium, 4% nickel and 7% manganese
Much more resistant to corrosion than 300 grade
Does not have magnetic properties
Harder to sell to scrap buyers, so 200 steel is hard to accumulate enough to find a buyer

How to identify 400 stainless steel

It is an alloy of iron with 11% chromium and ~1% manganese
Does not contain nickel and therefore has magnetic properties
Due to its magnetic properties, many buyers will not give a high price for it.

How to identify cupronickel

This is a copper/nickel alloy
Worth much more than copper 1
Some will cheat and try to buy this material at the price of copper or cheaper
In fact, nickel silver contains from 30% to 90% nickel, and it is 3 times more expensive than copper
Often used in counterfeit jewelry, silver plated cookware, ship parts, heat exchangers and condensers, musical instruments and more

You will have to go around many scrap buyers before they will give you a fair price for cupronickel.

Electric heating elements

Heating elements from electric stoves are usually made of nickel
Use a handheld spectrometer for accurate pricing

How to identify carbide (tungsten carbide)

Carbide is short for tungsten carbide.
It is heavy, 16 times heavier than water!
Two tablespoons of carbide weigh more than a kilogram!
Usually found in the form of tips of cutters, saws
Produces very short, dull, dark red sparks on spark test
Very durable

Source: https://reminform.com/kak-proverit-nerzhaveyku-v-domashnih-usloviyah/

How to test stainless steel at home? — Machine tools, welding, metalworking

A portable metal analyzer allows you to quickly determine the content of chemical elements and make a conclusion about the quality of stainless steel

How to check whether stainless steel is food grade or not

A portable metal analyzer allows you to quickly determine the content of chemical elements and make a conclusion about the quality of stainless steel

Is stainless steel magnetic or not? Grades and properties of stainless steel

March 27, 2019
Miscellaneous
Svetlana Pavlova

It is impossible to imagine the absence of anti-corrosion steel in modern life. The emergence of a stainless alloy made it possible to make great strides in many areas of the national economy. Only the addition of chromium to steel makes it resistant to corrosion. But when using it, consumers often have a question: is stainless steel magnetic or not? That's what we'll talk about in this article.

What is anti-corrosion steel?

Steel that does not become rusty during use is popularly called stainless steel. It is obtained from an alloy of iron with carbon and various alloying additives: nickel, chromium, niobium, titanium. Each of these components enhances or reduces certain properties of the alloy - magnetism, strength, hardness, ductility, corrosion. The main quality of stainless steel is corrosion resistance. It just depends on the chromium content in it.

The more of this metal in the alloy, the less susceptible it is to corrosion. Therefore, all steels that are resistant to rust contain at least 10.5% chromium. The uniqueness of this metal is that when it reacts with oxygen, it creates an oxide film on the surface of the product, which prevents the alloy from reacting with aggressive environments. Moreover, if the surface is damaged, the film forms again after the oxidation of chromium with oxygen.

Stainless steel classification

And yet, is stainless steel magnetic or not? Depending on the composition of chemical elements and internal structure, it can be magnetic or not, and is divided into the following types:

Ferritic - contain more than 20% chromium, are resistant to aggressive environments, are endowed with magnetic properties, are affordable, and are widely used.
Austenitic - do not corrode, contain large amounts of nickel and chromium, are flexible and durable. Easy to weld, belong to non-magnetic alloys.
Martensitic - anti-corrosion alloys can be exposed to high temperatures, do not emit harmful fumes, and have increased wear resistance and strength.
Combined - special stainless steels that combine the properties of all the above groups. Produced according to individual customer requests. The greatest demand is for austenitic-martensitic and austenitic-ferritic alloys.

It should be noted that the magnetic properties of steel do not affect its corrosion properties.

Magnetic properties of materials

All materials according to their magnetic properties are divided into:

Paramagnets - tin, platinum, aluminum - increase the external magnetic field due to the coincidence of molecular currents with it.
Diamagnets - copper, silver, zinc, their internal field weakens the external one.
Ferromagnets - iron, cobalt, nickel, in which magnetization is greatly enhanced even under weak influence of an external field.

Why is stainless steel magnetic? This happens when the external magnetic field is strengthened by the internal one. Moreover, the more intensely they increase each other, the magnetization will be stronger. In addition, the magnetic properties of stainless steel depend both on the ratio of alloy additives that make up its composition, and on the phase state of the steel.

How to identify a stainless steel product?

Many consumers often try to determine on their own what metal a particular household item is made of. Visually, ordinary steel cannot be distinguished from stainless steel, so it is customary to use a magnet to check.

There is an opinion that real anti-corrosion steel is not magnetic. Can stainless steel be magnetic or not? Anything can happen. Therefore, this method of verification does not give a reliable result.

Sometimes it happens that a product is attracted to a magnet, but serves for a long time without changing its qualities.

And vice versa, which does not react to it in any way, upon contact with water it becomes covered with rust. Corrosion resistance can be correctly determined by examining its chemical composition, which is impossible to do at home. To protect yourself from counterfeits, it is better to purchase household products in branded stores.

Stainless steel that is not magnetic

Very often, alloys with a high content of chromium, nickel and manganese are used to produce anti-corrosion steel. They are used to produce a large number of different equipment and products for use in various fields. Non-magnetic steels include:

Austenitic. They are used to make equipment for ships, refrigerators, the food industry, kitchen utensils and plumbing equipment.
Austenitic-ferritic. The main advantages of such alloys are strength and increased resistance to cracking.

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People most often in everyday life come across equipment and products made from these steels, so to the question “Is stainless steel magnetic or not?” and answer in the negative, although this is incorrect.

Anti-corrosion magnetic steels

Alloys that are resistant to rust but are strongly attracted to a magnet include:

Martensitic - the material has high strength, can be ground and polished well, is very resistant to corrosion, and can be easily processed by stamping, cutting and welding. In addition to the manufacture of industrial equipment, it is used for the manufacture of cutlery. Therefore, the question of whether stainless steel is magnetic or not can be answered positively.
Ferritic – the most popular grade of steel with magnetic properties is AISI 430, used for the production of food equipment.

Use of chromium-nickel steel

Anti-corrosion steel 12Х18Н10Т is an environmentally friendly and durable material.

The composition of the chromium-nickel alloy, in addition to the main component - iron, includes up to 19% chromium, which provides it with strong anti-corrosion properties, and 11% nickel, which transfers it to the class of austenites and imparts flexibility, strength and heat resistance.

Due to its characteristics, it is widely used. Many people are interested in whether steel grade 12Х18Н10Т is magnetic or not? It is non-magnetic, like all austenitic alloys, and is used in the following industries:

Chemical - aggressive acids: acetic, nitric, phosphoric are transported through pipes made of this grade of steel.
Food – dairy, meat, alcohol.
Mechanical engineering – production of parts in contact with acids and alkalis, production of welded equipment, exhaust system manifolds.
Petroleum - for the manufacture of pipes.

In addition, chromium-nickel alloys are used in the fuel and energy sector. Furnace fittings and heat exchangers are made from them.

Conclusion

Now you know which stainless steel is magnetic and which is not, and that these properties do not have any effect on the quality of the purchased product. At home, there is no way to check whether the dishes or plumbing equipment you purchased will rust or not. Everything will become clear during operation. To avoid making a mistake in your choice, make purchases at large retail outlets and from well-known manufacturers.

Source: https://truehunter.ru/458381a-nerjaveyka-magnititsya-ili-net-marki-i-svoystva-nerjaveyuschey-stali

Food grade stainless steels. Aspects of choice

The manufacture of containers or equipment that interacts with food products requires careful selection of materials. Storage, preparation, sanitary processing, and transportation of food are usually associated with conditions in which even stainless steel can corrode and negatively affect the quality of food. The so-called food grade stainless steel helps solve the problem.

Food grade stainless steel is a general name for grades of stainless steel that exhibit high corrosion resistance. There is no such concept in GOST standards, which is why food grade stainless steel often has to be chosen based on scattered information and reviews. What are food grade stainless steels and how to make the right choice?

Food grade stainless steel

Stainless steels are currently considered an almost indispensable material for creating food processing equipment.

The grades of stainless steel approved for contact with food products were determined mainly based on the experience of wine production, which is carried out using the most corrosive processes and technologies.

As a result, it turned out that when choosing a brand of food-grade stainless steel, one should take into account the duration of its contact with the food product. The longer the contact, the higher the corrosion resistance required.

Currently, stainless steel grades AISI 304, AISI 304L, AISI 430, AISI316, AISI 316L, AISI 316Ti, AISI 321 are widely used for the food industry. All of them are alloyed stainless steels.

If you need food grade stainless steel, the brand can be any from this list, but you should know that AISI 304, AISI 430, AISI 316 do not contain stabilizing titanium. This reduces their corrosion resistance and makes them sensitive to mechanical, thermal and chemical influences.

They can be used for short contact with food products under gentle operating conditions.

Features of stainless steel for the food industry

Food manufacturers most actively use stainless steel pipes. They must meet the requirements of the DIN 11850 standard, which determines the composition of the steel and the quality of the weld. Stainless steel pipes fully meet the increased requirements for hygiene and environmental friendliness of materials used in the production of equipment for the food industry and public catering. They are made from AISI 304 and AISI 316L steels, which exhibit the following properties:

high corrosion resistance along the entire length of the pipe and in areas of welded joints;
resistance to chemically aggressive environments;
wear resistance;
environmental safety and non-toxicity;
compliance with migration (dissolution) standards of heavy metals in the working environment;
maintaining smoothness parameters throughout the entire service life, which facilitates cleaning and maintenance of the equipment.

In food production, hot solutions of sulfamic acid or caustic soda are often used to clean equipment. In these conditions, it is better to choose AISI 316 stainless steel, which is more resistant to aggressive environments. For domestic conditions and public catering, where the metal does not interact with such solutions, you can use AISI 304 and cheaper AISI 430, AISI 410.

Below, for clarity, the types of stainless steels according to AISI used in food production, their compliance with other standards, including Russian, as well as the permissible applicability of stainless steel in various environments are presented.

Table 1. 1. Translations of international standards for designating the main steels used in food production.

Table 1. 2. (continued) Translations of international standards for designating the main steels used in food production

Table 2. Applicability of stainless steels according to AISI. Corrosion resistance of steels according to AISI in various applications

Price

If you need food-grade stainless steel, the price will be determined by the presence of expensive alloying components in the composition. The quality of surface treatment of the selected products is also important. Equipment for the food industry places higher demands on stainless steel, which is used in more aggressive conditions, and in case of corrosion can harm huge volumes of products. Cheap food grade stainless steel can be used in everyday life and public catering.

How to identify food grade stainless steel?

To determine the composition of food-grade stainless steel and its suitability for corrosion resistance parameters, you can use a guide to stainless steel grades. If you have a sample of stainless steel of an unknown brand, its suitability can be checked by placing it in a two percent vinegar solution or in a working environment for two to three days. Steel can be used if the sample does not darken.

The common belief that food grade stainless steel can be determined using a magnet is erroneous. Among the grades of food grade stainless steel, there are both magnetizable and non-magnetizable steels.

To make your choice, do not hesitate to consult with a specialist from the company where you are going to purchase stainless steel.

The better you understand the food production processes for which you need stainless steel, the better your chances of making the right choice.

Source: https://www.kp.ru/guide/pishchevaja-nerzhaveika.html

Metals and alloys that are often confused

The silver alloy of iron and chromium is suitable for the production of kitchen utensils, medical instruments, bearings, cutting elements, etc. But these items are also made from the following materials:

nickel-plated brass (a white copper alloy with a zinc content of more than 25%);
cupronickel (silver-white metal made from an alloy of copper and nickel);
white copper (an alloy containing at least 25% nickel).

Polished aluminum, nichrome, nickel silver and other alloys used for the production of cookware, knives, and jewelry can easily be confused with alloy steel. Despite their similar composition and high nickel content, they are easily distinguished at a scrap metal collection point and will not be accepted at the desired price. There are several ways to determine whether aluminum or stainless steel has fallen into your hands: chemical, mechanical, etc.

Analysis using a magnet

In the laboratories of large collection points, a spectrometer is installed - an optical device for spectroscopic research. It is equipped with an interferometer to evaluate the intensity of spectral lines and measure wavelengths. The received data is processed by a computer, giving an accurate conclusion about the composition of the alloy.

If you need to identify stainless steel at home, use improvised but relatively reliable means. One of them is a magnet: it is generally accepted that stainless steel is not magnetic. However, this diagnostic method is not accurate enough, because martensitic and ferritic alloys have magnetic properties.

Using a magnet, only austenitic and austenitic-ferritic alloys with a high content of chromium and nickel can be detected. They are used to produce dishes, plumbing and refrigeration equipment, containers for food liquids, etc. Contrary to popular belief, it is impossible to accurately determine stainless steel with a magnet, but you can roughly identify its type.

Defining food grade stainless steel

As stated above, a magnet helps to identify food grade stainless steel at home. Alloys with a low carbon content and a large amount of nickel in the composition do not react to contact with it. Stainless steel with a high carbon content (more than 0.9%) has magnetic properties and is prohibited for use in the food industry.

Also, to determine food grade stainless steel, various acids are used (citric, tartaric, acetic, etc.). Alloys for food applications contain more alloying additives, so their surface film is stronger and contains almost no iron.

For additional protection against corrosion, passivation is used - a method of treating the surface of a metal, as a result of which its activity is reduced and it does not enter into oxidative reactions.

Under the influence of these acids, stainless steel may become covered with a light patina, which indicates its non-food purpose.

Source: https://pechi-sibiri.ru/kak-proverit-nerzhavejku-v-domashnih-uslovijah/