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
What determine the magnetic properties of materials?
A magnetic field with a certain level of its intensity (H) acts on bodies placed in it in such a way that it magnetizes them. In this case, the intensity of such magnetization, which is designated by the letter J, is directly proportional to the field strength. The formula by which the intensity of magnetization of a certain substance is calculated (J = ϞH) also takes into account the coefficient of proportionality Ϟ - the magnetic susceptibility of the substance.
Depending on the value of this coefficient, all materials can be included in one of three categories:
- paramagnetic materials – coefficient Ϟ is greater than zero;
- diamagnetic materials – Ϟ is equal to zero;
- ferromagnets are substances whose magnetic susceptibility is significant (substances, which, in particular, include iron, cobalt, nickel and cadmium, are capable of actively magnetizing, even when placed in weak magnetic fields).
Directions of action of magnetic moments of neighboring atoms in substances of different magnetic nature
The magnetic properties that stainless steel has are also associated with its internal structure, which can include austenite, ferrite and martensite, as well as combinations thereof. At the same time, the magnetic properties of stainless steel are influenced both by the phase components themselves and by the ratio in which they are found in the internal structure.
Stainless steels with good magnetic properties
Stainless steel, in which the following phase components predominate, has good magnetic properties:
- Martensite is a ferromagnet in its pure form.
- Ferrite - this phase component of the internal structure of stainless steel, depending on the heating temperature, can take two forms. This structural form becomes ferromagnetic if the steel is heated to a temperature below the Curie point. If the heating temperature of the stainless steel is above this point, then high-temperature delta ferrite, which is a pronounced paramagnet, begins to predominate in the alloy.
From all of the above, we can conclude that the stainless steel that is magnetic is one in which martensite predominates in its internal structure. Like regular carbon steels, these alloys react to magnets. By this feature they can be distinguished from non-magnetic ones.
The ability of stainless steel to magnetize does not affect its corrosion resistance
Stainless steels, in which ferrite or its mixture with martensite predominate, are most often also classified as ferromagnetic, but their properties may vary depending on the ratio of the phase components of their internal structure.
Stainless steel, the magnetic properties of which can change, are mainly chromium and chromium-nickel alloys, which may belong to one of the following groups. Martensitic
Steels with a martensitic internal structure, which, like conventional carbon steels, can be strengthened by quenching and tempering. Such stainless steel, in addition to general engineering enterprises, is actively used in everyday life (in particular, cutlery and cutting tools are made from it). The most common grades of such magnetic steels, products from which are produced with heat treatment and can be subjected to finishing grinding and polishing, include 20Х13, 30Х13, 40Х13.
Steel grade 30Х13 is less ductile than alloy 20Х13, despite its similar composition (click to enlarge)
This category also includes the 20Х17Н2 alloy, which is characterized by a high chromium content in its chemical composition, which significantly enhances its corrosion resistance. Why is this stainless steel popular? The fact is that, in addition to high resistance to corrosion, it is characterized by excellent workability using cold and hot stamping and cutting methods. In addition, products made from such material are well welded.
Ferritic
A common ferritic-type magnetic steel, which, due to the low carbon content in its chemical composition, is softer than martensitic alloys, is 08Х13, which is actively used in food production. Such stainless steel is used to make products and equipment intended for washing, sorting, grinding, sorting, and transporting food raw materials.
Mechanical properties of steel 08Х13
Martensitic-ferritic
A popular brand of magnetic stainless steel, the internal structure of which consists of martensite and free ferrite, is 12X13.
Corrosion resistance of steel grade 12Х13 (other name 1Х13)
Non-magnetic stainless steels
Stainless steels that are not magnetic include chromium-nickel and chromium-manganese-nickel. They are usually divided into several groups.
Austenitic
The most popular brand of such stainless steels, which occupy a leading place among non-magnetic steel alloys, is 08Х18Н10 (international analogue according to AISI 304 classification).
Steels of this type, which also include 08Х18Н10, 08Х18Н10Т, 12Х18Н10Т, 10Х17Н13М2Т, are actively used in the production of equipment for the food industry; kitchenware and cutlery; plumbing equipment; containers for food liquids; refrigeration equipment elements; containers for food products; medical supplies, etc.
Composition and application of austenitic steels
The great advantages of such stainless steel, which does not have magnetic properties, are its high corrosion resistance, demonstrated in many aggressive environments, and manufacturability.
Austenitic-ferritic
Steels of this group, the most popular grades of which are 08Х22Н6Т, 08Х21Н6М2Т and 12Х21Н5Т, are distinguished by a high chromium content and a low nickel content. To give such a stainless steel the required characteristics (an optimal combination of high strength and good ductility, resistance to intergranular corrosion and stress-corrosion cracking), elements such as copper, molybdenum, titanium or niobium are introduced into its chemical composition.
https://www.youtube.com/watch?v=5mFIym1rAQM
Chemical composition of some industrial grades of austenitic-ferritic steels (click to enlarge)
In addition to the above, stainless steels that are not magnetic include alloys with an austenitic-martensitic and austenitic-carbide structure.
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.
Source: https://respect-kovka.com/kak-proverit-nerzhaveyku-v-domashnih-usloviyah/
How to identify stainless steel at home? — Handyman's Handbook
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.
How to choose a brick for a cellar?
Source: https://reminform.com/kak-opredelit-nerzhaveyuschuyu-stal-v-domashnih-usloviyah/
How to distinguish stainless steel from other metals?
We welcome everyone who, being a real owner, draws knowledge and experience from our site. This suggests that today for some reason you are interested in the question of how to distinguish aluminum from stainless steel. But really, it’s not that simple.
Features of aluminum
Why is aluminum so valuable? This is a pure metal classified as non-ferrous. It is lightweight, durable, has a good degree of deformation, and is resistant to aggressive environments and corrosion.
All of the listed advantages allow it to be used in a variety of areas from industry and construction (except for industries where high-strength structures are manufactured) to domestic use.
The demand for the valuable metal is great, so it is important to know how to accurately distinguish it from other similar metal alloys.
Aluminum or stainless steel: methods of determination
There are several ways to help you do simple research on your own at home. Find out how to distinguish aluminum from stainless steel - advice from forum members and experts.
- Using a magnet. Aluminum of any grade will not stick to a magnet. Stainless steel also has this property. But there is an exception to the rule. If it contains nickel in sufficient quantities, the tested products will have some attraction. If there is a lot of chromium or copper in a stainless metal, it will not have any effect on the magnet.
- Marking on stainless steel. Some stainless steel products have identification markings. This already gives a hint on how to distinguish aluminum from stainless steel. If there are markings, for example, “STAINLESS” and the like, this is not aluminum.
- Plain paper won't lie. The method is very simple. Experiment conditions: you need white, as thick paper as possible (printer paper will also work). Use a thick cloth to remove dirt from the edges of the products being tested. Move the cleaned areas one by one with some pressure across the sheet. There will be no traces left of the stainless steel. Aluminum will draw gray stripes.
- How to distinguish aluminum from stainless steel by the color of the metal? The surface of the object has a shiny, colorless hue that does not change over time - it is stainless steel. The matte surface of a product that has a grayish or whitish color is aluminum. It will not be polished with sandpaper to a high gloss finish. Check it out.
- Under mechanical load. Another simple way will help you understand how to distinguish aluminum from stainless steel. Hit the product against the surface of any hard metal in the dark. Aluminum will never spark, unlike stainless steel.
- Thermal conductivity, melting. Compare where the water heats up faster. Of course, in an aluminum container. This metal has much better thermal conductivity. But it is not used on the burner of a gas furnace; the melting point is 660 °C. Stainless steel cannot be melted in the usual way (melting index is above 1800 °C).
- Testing for copper sulfate. An option available to everyone. Copper sulfate, after exposure to aluminum, will leave cloudy stains and traces on it, but will not appear on stainless steel.
- Alkaline solutions. Any housewife knows that it is impossible to boil aluminum cookware in alkaline solutions. It will darken and lose its appearance. Conclusion: aluminum products are afraid of alkali, both sodium and potassium. The same cannot be said about stainless steel.
- Acid test. All acids, starting with the usual citric acid and ending with more aggressive ones, will leave marks when they get on the aluminum surface. You won’t see them on stainless steel; it doesn’t react with acids.
Duralumin – an alloy of aluminum with transition metals
The industry is not able to provide itself only with pure metal, and duralumin comes to the rescue here - various combinations of manganese, copper and magnesium in an alloy with aluminum.
In addition to all the above properties of its older brother, the transition metal has:
- high degree of strength;
- long service life;
- plasticity;
- high hardness.
It accumulates fatigue properties more slowly and is resistant to cracking.
Source: https://varimtutru.com/kak-otlichit-nerzhaveyku-ot-drugih-metallov/
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?
How to identify stainless steel at home - Metalworker's Guide
How to distinguish one steel grade from another if, for example, AISI 304 and AISI 303 sheets were stored together? A number of simple, inexpensive and non-damaging tests can help solve this problem. It should be noted right away that such tests have a number of serious limitations.
For example, such tests will not help determine which of two sheets of steel of the same grade has been heat treated and which has not. Additionally, there is no easy way to distinguish certain grades of steel from each other. For example, it is impossible to distinguish steel AISI 304 (08Х18Н10) from AISI 316L (03Х17Н14М3), or 304 (08Х18Н10) from 304L (03Х18Н11).
A molybdenum content test will help determine whether molybdenum is present in steel, but without additional information the grade of steel cannot be correctly determined. For example, AISI 316 (10Х17Н13М2) steel, based solely on the results of this test, can be defined as 316L (03Х17Н14М3), 2205 or 904L.
Often, only with the help of more complex tests, in which the metal is exposed to chemical reagents, strength or heat resistance is checked, can the grade of steel be reliably determined. If simple tests do not help, then a full spectral or chemical analysis in the laboratory cannot be avoided.
Reaction to magnet
This test will help determine that austenitic steels (for example, AISI 300 series) do not react to a magnet when approaching it. Other stainless steels, such as ferritic, martensitic and duplex, react to magnets. When performing this test, it should be remembered that some austenitic steels, for example, 304 (08Х18Н10), can be attracted by a magnet if they were produced by cold rolling.
Reaction to nitric acid
Helps differentiate carbon steel from stainless steel. First, you need to place a steel sample in a solution of nitric acid (from 20-50%) at room temperature, or drop the solution onto a clean steel surface. A reaction will begin on the surface of the carbon steel, releasing caustic brown vapor. This reaction does not occur with stainless steel. When working with nitric acid, you must be extremely careful, and you should not inhale the vapors released during the reaction.
Molybdenum content test
Helps determine whether steel contains molybdenum. Steel containing sufficiently molybdenum, for testing as follows: 316 (10x17n13M2), 316L (03x17N14M3), 444, 904L, 2205, all "super -duplicate" alloys (S32760, Zeron 100, S32750, 2507, S32550, S32520, UR52N+). The test can also determine molybdenum in other steels containing approximately 2% Mo.
When conducting a test, it is best to compare an unknown steel with a control sample, for example, AISI 304 (08Х18Н10) and AISI 316 (10Х17Н13М2) steels. For the test you will need an acid-based reagent (you can use either the American “Decapoli 304/316” or “Moly Drop 960”, or domestic analogues, although they are quite difficult to find).
First, it is necessary to prepare the surface of the test sample by cleaning it with sandpaper. Then drop the reagent onto the surface of the steel to be determined and onto the control sample. Dark yellow spots appearing after 2-4 minutes indicate the presence of molybdenum. When carrying out the test, do not forget that its reliability may be affected by the temperature of the samples.
For example, some steels containing about 0.5% molybdenum in impurities may react positively to the test at low temperatures. During the test, you should be careful when working with the reagent and follow the requirements for safe work with acids.
Sulfur content test
Sulfur is a harmful impurity that causes brittleness of steel during hot forming. This test helps determine the level of sulfur in steel. For this test, control samples of AISI CS1020, S1214, 304 or 303 steels will be needed, comparison with which will help in determining the degree of sulfur content. To carry out the test, it is necessary to clean the surface of the test sample using sandpaper, and control samples should be prepared in the same way.
Next, you should soak the photographic paper in a 3% sulfuric acid solution for 3 minutes, apply the photographic paper face to the surface of the test sample, hold for 5 seconds and compare the results of the tested steel and the control samples. A dark brown stain indicates high sulfur content. When testing, it should be taken into account that the reliability of the result is seriously influenced by the density and duration of contact of the paper with the surface.
GOST 30245 03 steel square pipes assortment
When performing this test, also remember to be careful when working with acid.
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How to distinguish aluminum from stainless steel
31.10.2017 16:13The 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.
How to distinguish stainless steel from other metals
How to distinguish one steel grade from another if, for example, AISI 304 and AISI 303 sheets were stored together? A number of simple, inexpensive and non-damaging tests can help solve this problem. It should be noted right away that such tests have a number of serious limitations.
For example, such tests will not help determine which of two sheets of steel of the same grade has been heat treated and which has not. Additionally, there is no easy way to distinguish certain grades of steel from each other. For example, it is impossible to distinguish steel AISI 304 (08Х18Н10) from AISI 316L (03Х17Н14М3), or 304 (08Х18Н10) from 304L (03Х18Н11).
A molybdenum content test will help determine whether molybdenum is present in steel, but without additional information the grade of steel cannot be correctly determined. For example, AISI 316 (10Х17Н13М2) steel, based solely on the results of this test, can be defined as 316L (03Х17Н14М3), 2205 or 904L.
Often, only with the help of more complex tests, in which the metal is exposed to chemical reagents, strength or heat resistance is checked, can the grade of steel be reliably determined. If simple tests do not help, then a full spectral or chemical analysis in the laboratory cannot be avoided.
What affects the price of stainless steel, how to determine stainless steel
Scrap of non-ferrous, rare earth metals,
battery, cable scrap.
Stainless steel or stainless steel is part of the group of alloy steels and may include impurities that are designed to improve its characteristics: hardness, resistance to aggressive environments, corrosion and high temperatures.
What can be scrapped?
Stainless steel scrap collection centers are ready to accept:
- pipes;
- sheets;
- shavings;
- dishes;
- cutlery;
- metal scraps;
- springs and other metal parts, and finished stainless steel products.
What affects the price of scrap?
The main evaluation criterion in the process of accepting stainless steel scrap is the percentage of nickel and chromium. The more nickel there is in a metal, the more expensive it is.
The price of scrap is also affected by:
- Appearance and condition of the metal. The presence of rust will reduce the initial cost of scrap. And loose rust is the first sign of low quality metal.
- Magnetic properties. Products that are not magnetic will cost more.
- Density and durability of paintwork. A strong paint layer complicates the metal cleaning procedure, therefore reducing the cost of scrap.
- Number of metal layers. Multilayer steel is less in demand, so its price will be lower.
How to quickly determine the quality of stainless steel
The cost of stainless steel directly depends on its quality. You can determine the quality of steel:
- on low-quality stainless steel, a drop of water leaves a yellowish stain;
- Salt will also help check the quality of the metal. On the surface of high-quality alloys, salt leaves no traces after drying;
- high quality metal produces a short, direct spark.
nickel in various metal objects
The percentage of nickel in stainless steel is classified:
- nickel 2-5% - may be contained in sanitary waste objects;
- nickel 10% - present in kitchen utensils;
- nickel 12% - found in plates, metal scraps, construction waste and other heat-resistant materials;
- nickel 30-85% - metal alloys (matte);
- nickel 95% - present in construction and plumbing rings, connectors, wire, powder, scrap and other high-alloy steel.
How to distinguish stainless steel from other metals
Taking into account the fact that stainless steel may or may not have this property, there is no need to focus on this indicator.
Therefore, in order to distinguish stainless steel from scrap of other metals, you need to clean a small area of the surface of the object being tested until the metal shines, then use a few drops of concentrated copper sulfate applied to the scrap.
Stainless steel under the influence of vitriol will become covered with a coating of red copper. It is almost impossible to determine whether a stainless steel belongs to the food category without special devices.
How to hand over stainless steel in Moscow
The procedure for accepting stainless steel in Moscow by MDM-Vtormetall is aimed at maintaining the interest of the donating party:
- collection points are located in different parts of the city;
- We provide pick-up service at any convenient time;
- We provide free consultations;
- We are considering the possibility of dismantling the facility ourselves.
Our scrap metal collection center tries to offer the most favorable prices for receiving stainless steel.
Use in medicine
This alloy, due to its high hygienic properties, rigidity, wear resistance and ease of cleaning from various contaminants, including bacteriological
Architectural and construction elements
Today, stainless steel, due to its hygienic properties, high strength and corrosion resistance, is used everywhere, including in architecture.
Bar equipment
In bars, like in any dining room, there is a kitchen where you can find a lot of different stainless steel equipment. But this article will talk about equipment for
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Source: http://www.mdm-vtormetall.ru/stati/interesnoe-o-nerzhavejke/podrobnosti-o-lome-nerzhaveyushhej-stali.html
How to distinguish stainless steel from aluminum
One of the most popular types of metal in production is aluminum. It is often used to make household products. To determine exactly what kind of metal you have, use these tips and perform a few simple tests.
- The easiest way is to use a magnet. Aluminum is paramagnetic and practically non-magnetic. Even a child can carry out a test using a magnet at home.
- Using a plain piece of paper. To carry out the test, you will need to remove dirt from the surface of the object being tested and run it with paper, pressing firmly on the product. If you have stainless steel in front of you, then there will be no traces left on the sheet, but with aluminum, gray stripes will appear.
- Another criterion for distinguishing stainless steel from aluminum is the color of the metal. If the surface is smooth and shiny, then this is stainless steel; aluminum has a matte surface without a characteristic shine.
- Thermal conductivity indicators. To install metal accessories, simply pour water into a container and bring to a boil. In aluminum cookware, water will boil much faster, since the thermal conductivity of this metal is much higher.
- Separately, we can distinguish chemical methods for determining stainless steel using various acids and alkalis. When treating aluminum with alkali, brown spots remain on the surface; stainless steel will not have any visible changes.
- Exposure to copper sulfate. You can find this reagent in any agricultural store. After application to the aluminum surface, cloudy stains will certainly remain. Vitriol has no effect on stainless steel.
Using these methods will allow you to determine at home with 100% accuracy where the product is made of aluminum and where it is made of stainless steel.
How to distinguish stainless steel from other types of steel
In appearance, all steel grades are almost identical, but at the same time they have different technical characteristics. This means that products made from different types of steel behave differently. To distinguish stainless steel from another grade of steel, you can use several methods:
- Use of nitric acid. This chemical liquid helps distinguish stainless steel from carbon steel. If you apply a few drops to the surface of the steel, a reaction will begin in which caustic steam will be released. This reaction is typical for carbon steel; no changes will occur with stainless steel.
- Check the reflection on the surface. Stainless steel has bluish-yellow tints on its surface.
- Marking. Steel products are always marked with the type and grade of material used. If the numbers are preceded by the letters “STAINLESS”, this means the use of alloy steel.
These simple tips will help you accurately determine the presence of stainless steel.
How to distinguish stainless steel from non-ferrous metals
It is difficult for an ignorant person to separate stainless steel from non-ferrous metals. This will require complex chemical actions and reagents. Still, you can use some expert advice:
- Take a small piece of the sample and drill a hole. In duralumin, the chips move away in a spiral and do not stick to the drill.
- Hydrogen peroxide and 20% sodium sulfide can be used. When these reagents are applied to a cut, the surface of non-ferrous metals will darken.
Distinctive characteristics of food grade stainless steel from technical grade
It must be said that the division of stainless steel into two types has a special character, since they differ in areas of use. The main difference between them is the surface treatment. For the food type, the surface is of particular importance, since the metal will come into contact with food products.
Distinctive features of food grade stainless steel are a smooth surface with a high level of processing. Food grade stainless steel is a highly alloyed metal that is resistant to corrosion and rust. The amount of additives affects the quality of product operation. The food grade is susceptible to the influence of an aggressive alkaline environment, so it adds more metal impurities. Based on the composition and markings, you can accurately determine what type of stainless steel it is.
Results
To determine the type of metal and the distinctive features of stainless steel, it is enough to know the basics of chemistry and some characteristics of metals. By conducting simple chemical experiments or using simple household methods for installing stainless steel products, you can easily determine what type of metal was used.
We also recommend reading:
What is the role of the ceiling cornice?
Water-air cooling, why is it good for aluminum?
Aluminum pipes: properties and applications
Source: https://aluminiypro.ru/kak-otlichit-nerzhavejku-ot-drugih-metallov
Is stainless steel magnetic: magnetic properties of stainless steel
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 identify stainless steel: methods and materials
Stainless steel is the name of a group of iron alloys that contain corrosion-resistant metals. Carbon, titanium, copper are used as additives, and the composition also includes from 12 to 25% chromium and nickel. Alloy steel alloys are not susceptible to corrosion and are resistant to moisture, aggressive environments, alkalis and acids.
Stainless steel is used to produce dishes, knives, elements of machine tools, cars and industrial equipment, especially in the chemical and oil industries. Such scrap is accepted at a high price, which depends on the composition. The most expensive alloys are those with a high nickel content (from 10%). To get maximum profit from scrap metal, it is important to know how to identify stainless steel?
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.
Types and grades of non-magnetic steels
If the origin of the product is known, the reaction with a magnet can roughly determine the type of stainless steel. The following brands are not magnetic:
- AISI 409 (analogue 08X13) - containers for cargo transportation, parts for the exhaust system of a car, etc. are made from this ferritic steel. (plasticity and lack of magnetic properties are due to the extremely low C content - less than 0.03%);
- AISI 304 (analogous to 8-12X18H10) - household items are made from it, as well as utensils and equipment for the food and pharmaceutical industries;
- 12Х21НБТ (ЭИ8П) – austenitic-ferritic steel for use in medium-aggressive environments, from which containers and equipment for the chemical and pharmaceutical industries are produced.
Stainless steel grades AISI 402–420, which contain from 11 to 14% chromium and less than 0.07% carbon, are not magnetic.
Magnetic stainless steel
AISI 430 steel (analogous to 08X17, which contains 15% chromium) has magnetic properties. It is used to produce wire mesh, pipes for transporting petroleum products, and elements of gas and oil refining process plants. Steel grade AISI 630 contains up to 5% nickel and chromium, as well as a large number of additives: copper, titanium, molybdenum. It is used in instrument making and metallurgy.
Stainless steel can be identified even if it is magnetic. To do this, place a sample of the material in 2% vinegar or another aggressive medium for 1–2 days. Corrosion-resistant alloys will pass this test without visible changes, but metals that are susceptible to corrosion will darken.
Copper sulfate will also help determine magnetic stainless steel at home. First clean the metal surface with sandpaper, and then apply a few drops of a concentrated substance (rusting alloys are covered with a red film).
Spark test
Testing metal for spark color is a common method of sorting scrap metal, which is used even by specialists. The grade of stainless steel can be determined by the following factors:
- the number of sparks and flashes, which is directly proportional to the volume of carbon in the alloy;
- the color of the sparks, which indicates the composition of the metal (the lighter it is, the higher the likelihood that this is low-carbon steel);
- the presence of shiny white sparks, which indicates a high titanium content in the composition.
To carry out the test, an angle grinder (grinder) is required. Start grinding the surface of the steel and observe the reaction. The color, length and shape of the sparks will help you accurately determine metal or stainless steel.
"Yellow flow" or "white fork"
There are many types of sparks: “fork”, “twig”, “arrow”, etc. You learn to distinguish them with experience, but even an untrained person will be able to distinguish a dense and short stream of flashes from the long and rare sparks characteristic of stainless steel. The presence of dark red sparks coming out from under the grinding wheel indicates a high content of nickel, tungsten carbide and cobalt.
If a medium-density stream appears during the grinding process, and the sparks are straw-yellow at the base and white at the end, you have stainless steel. A long stream of sparks, reaching 1.5 meters, indicates the presence of nitrogen in the composition. In this case, it is not difficult to determine the grade of stainless steel: nitrogen alloys are quite rare and there are only a few of them (Nitrobe 77, Sandvik™ 14C28N, Böhler N680, etc.).
What does the price depend on?
Low-carbon, corrosion-resistant alloys are used to produce a wide variety of products: blades, profiled sheets, roofing materials, medical supplies. Scrap stainless steel can be collected when dismantling an old fence, dismantling an old refrigerator, throwing away unnecessary kitchen utensils, etc. In this case, potential income will depend on the following factors:
- type of steel (austenitic, ferritic, martensitic, etc.);
- steel grade (AISI 304, AISI 630, 12Х21НБТ);
- type of rolled metal (sheet, section, pipe);
- sheet thickness;
- compound;
- quality.
You can determine the stainless steel brand and composition in a laboratory setting by contacting a reliable collection point. We have the necessary equipment to analyze the composition, assess the quality and test the radiation activity of non-ferrous scrap. But you can pre-evaluate scrap metal at home.
How to evaluate quality?
The quality of stainless steel depends on various factors - from the amount of additives to the joining method. In places where welds are formed, the anti-corrosion properties of the metal deteriorate significantly, which over time leads to the appearance of rust and gradual destruction of the material.
Painted profiled sheets will have to be cleaned of the coating and sanded, damaging the protective layer on the surface. Accordingly, the metal will become less resistant to moisture, its quality will deteriorate, and therefore the price of such scrap will be lower. You can preliminary evaluate the properties of steel using a salt solution.
It should not leave stains on the surface of high-alloy steel. And water will leave yellowish stains on low-quality stainless steel.
The most expensive types of stainless steel
The cost is affected by the amount of nickel in the alloy: in the cheapest types its content does not exceed 5%. The most expensive are high-alloy alloys containing nickel from 12%. The expensive scrap includes plumbing fittings and rings, wire and various electrical connectors (connectors, adapters, etc.). Matte (a by-product of non-ferrous metallurgy) with a nickel content of over 35% is also highly valued, although it is classified as slag.
But the most common steel grade is A2, containing approximately 10% nickel and 18% chromium. It is usually used to make household items. To find out the exact price, visit our collection point: to evaluate scrap, specialists must inspect the metal, assess the degree of contamination, composition and properties.
Source: https://blog.blizkolom.ru/kak-opredelit-nerzhavejku
