The material of the century is today called stainless steel, which is now widely used for kitchen utensils. The most popular brand of stainless steel for utensils is marked 18/10. According to the German DIN standard, this is X5CrNi18-10. According to the European standard EN it is 1.4301, according to GOST it is a grade of steel 12X18H10.
Stainless steel cookware, what is medical steel, the choice of cookware, its thermal conductivity, stainless steel cookware with double and triple bottom.
Such an alloy contains, in addition to iron, 0.12% carbon, 18% chromium, 10% nickel, and up to 1% other impurities. That’s where the numbers 18 and 10 come from, they indicate the content of chromium and nickel. According to the US AISI standard, these are grades 304 and 321. The density of steel is 7.8 g / cu. cm.
What is medical steel.
In advertising, steel labeled 18/10 is often called medical. One well-known company advertised itself to the point that its supposedly “medical steel” kills germs. Steel experts only laughed, but buyers believed until an examination was conducted, the results of which were published in print. Steel 18/10, like other brands of stainless steel, does not kill germs.
Just products from it are easy to wash, and on a clean surface, microbes have nowhere to breed. After all, solid stainless steel does not form scratches, as on aluminum or enameled dishes, where dirt would accumulate, providing a favorable environment for the reproduction of microbes. Stainless steel cookware is more hygienic, it is very resistant to acids and alkalis, including at high temperatures.
And medical steel 18/10 is called because, along with kitchen utensils, watch cases, door handles, surgical instruments and cuvettes are made of it. The only thing this dishware does not like is to have a strong pickle in it for a long time. Stains may appear. The instructions provided with steel dishes do not even recommend putting salt in cold water. Grains of salt settle to the bottom and walls of the dishes and do not immediately dissolve in cold water.
They manage to act on stainless steel, leaving ugly dark spots on it. True, this does not affect the functional properties of the dishes. But it is better to add salt to the hot water while stirring, so that the grains immediately dissolve. In addition, rainbow stains may form on the surface of stainless steel cookware, especially new ones, after use. It’s okay, they are easily removed with a 4.5% solution of a table bite or citric acid.
Stainless steel cookware selection.
Let’s see what a good stainless steel cookware should look like. How thick should its walls be? The standard GOST 27002-86 applies to such dishes. According to this GOST, the wall thickness of the stainless steel pan must be at least 0.5 mm. This is a necessary minimum so that the dishes can be considered quality. And from the point of view of the criterion “consumer properties / price”, wall thickness in the range of 0.6-0.8 mm is considered optimal.
There are products with a wall thickness of 1 mm or more, but this only increases the cost of the dishes, makes them too heavy and requires more energy when heated. But some foreign manufacturers are not burdened with the need to comply with standards, and in an effort to reduce the cost of their products, they make dishes from sheets of metal that are too thin. These pans are frankly cheap, you can’t cook properly in them.
Stainless steel cookware always has a polished surface. Good dishes shine like a mirror, and it is not only beautiful, but also functional. According to the laws of physics, shiny surfaces cool much more slowly than matte ones. Therefore, food in stainless steel cookware stays hot longer.
When choosing stainless steel cookware, you need to pay attention to the quality of polishing (in the technique this is called “surface cleanliness”). GOST 27002-86 allows on the inner surface of dishes up to three point surface defects associated with polishing.
Stainless steel cookware.
Cheap types of dishes from Asia are sold only in the markets. Warranty for such dishes is not given, and the service life is a maximum of 2-3 years. But this is not a sentence for all dishes made in Asian countries; there are many brands that meet the requirements of standards. For dishes that meet the requirements of GOST, the warranty period is at least two years, and the declared service life, as a rule, is at least 6 years. In fact, it lasts much longer.
Good stainless steel cookware is noticeably more expensive than enameled and even more so aluminum. It is much more durable dishes with fluoropolymer non-stick coating. In a good stainless steel with a tightly fitting lid, you can cook without oil and water, and traces of food are washed off as easily as from dishes with non-stick coating. By the way, some types of steel utensils, most often pans, successfully apply non-stick coatings.
Thermal conductivity of stainless steel cookware.
Thermal conductivity steel weaves in the tail of all metals that have ever been used for kitchen utensils. This means that the heat received from the stove will be transferred too slowly into the pan. And it will not have time to be evenly distributed throughout the bottom, because of this, foci of overheating will form, and the food will burn.
The thin steel bottom from high temperature begins to bend over time, the bottom contact is broken, and this is no longer a pan, but one chagrin. She can’t even stand stably, not to mention the very poor heat transfer. We tried to solve this problem, making the bottom of pots and pans made of stainless steel more massive.
But to avoid sudden changes in temperature and the formation of foci of overheating just does not work out, and the food continues to burn. In short, the ideal material for kitchen utensils does not exist. But in the 1990s, technology was mastered to make an interesting compromise.
Double and triple bottom stainless steel cookware.
Due to the low thermal conductivity, stainless steel cookware was not particularly successful. Finally we figured out how to solve this problem. It is necessary to mount an aluminum or copper disk with good thermal conductivity into the bottom of the steel utensil. In recent decades, the development of technology has solved this problem..
In the beginning, there appeared dishes with a welded (soldered) bottom aluminum disk. But since aluminum quickly loses its appearance and, in addition, stains the stove, a more advanced design with a lower stainless steel capsule appeared.
Now in stainless steel dishes the so-called puff bottom, “sandwich” or encapsulated bottom is widely used. This bottom is called thermal distribution. The food does not burn, and the dishes retain heat for a long time. A traditional sandwich is two stainless steel sheets between which a layer of copper or aluminum is laid. Sometimes the walls of dishes are also layered. This technology is called Tri-ply. In any case, food only comes in contact with hygienic stainless steel..
The location of the layers in the sandwich can be seen on the edge on the side of the bottom. But more often the heat-conducting layer is located in a stainless steel capsule, as it were, and it remains only to believe the manufacturer – what is inside. Conscientious manufacturers and sellers demonstrate their products in a cut form, and you can verify the presence of a heat distribution layer and evaluate the thickness of the aluminum or copper layer.
Thanks to the puff bottom, all the advantages of stainless steel have added the high thermal conductivity of other materials. In this collaboration of different metals they managed to combine their best properties (strength, good thermal conductivity, resistance to alkalis, acids and corrosion, hygiene, beautiful appearance) and hide the flaws. Aluminum is used many times more often than copper to improve the thermal conductivity of the bottom of stainless steel cookware. It is still cheaper.
There are three ways to make a “sandwich,” that is, a “sandwich” of steel with aluminum:
– Soldering. Heated aluminum disc is brazed to steel using silumin based solder.
– Diffusion welding. It is hit by a press heated almost to the melting point of aluminum, with a force of up to 800 tons.
– rolling. For example, for material like Tri-ply.
For the manufacture of the lower part of the capsule, steel of the same grade 18/10 as the pan itself, or grade 430 according to AISI standard, is usually used. Now a very interesting question about the thickness of the layers in this “sandwich”.
The thickness of the aluminum thermal distribution layer according to GOST 27002-86 must be at least three millimeters, and copper – at least 1.5 millimeters. The optimum from the point of view of the criterion “consumer qualities / price” is the thickness of the aluminum layer of 4-5 mm. It is possible to make this layer thicker, but not necessary. Large thickness only increases the cost and weight of the dishes.
The multilayer bottom is also called thermal storage. The heat accumulated by such a smart bottom can be effectively used. Reduce the power of hotplates in advance and turn them off even before cooking.
According to theory, in such a puff dish made of stainless steel it is really possible to cook a dish on a candle flame, as one large company promised in an advertising fuse. But the promise is not fulfilled. But in principle, this is possible if the parameters of the puff bottom are correctly calculated (find the optimal thickness of each layer). And, of course, depending on what the candle will be like.