Stainless steel kitchenware has the characteristics of stainless steel, acid resistance, high temperature resistance, wear resistance and austenite generally non-magnetic. Stainless steel is a common high-grade alloy steel in our daily life, such as stainless steel knives, stainless steel kitchen utensils and stainless steel building materials. At present, we mainly have the following methods to identify stainless steel:
Stainless steel monolithic products generally come from steel mills ordered or imported from abroad, as well as the backlog and backlog of processed products in society. Different sources of stainless steel have different identification methods.
1. Generally, it is only necessary to check the marks on the steel or packaging according to the quality certificate of the imported or steel mill.
The quality certificate is the supplier's confirmation and guarantee of the inspection results of this batch of products. Therefore, the quality certificate not only states the name, specification, number of delivered pieces, weight and delivery status of the materials, but also states all inspection results of the specified guaranteed items.
Similarly, in order to facilitate management, avoid confusion and prevent use accidents caused by confusion, manufacturers indicate signs such as brand number, batch number, status, specification, quantity and manufacturer's code on materials or packaging. The marks marked on it shall be consistent with the contents of the quality certificate. There are three commonly used marking methods: coloring (painting on the designated part of the material to indicate its brand) and printing (stamping or spray printing on the designated part of the material to indicate the brand, specification and heat number, etc. Materials, commonly used in thick steel plates or large and medium-sized steel beams), and listed (hanging signs indicate the brand, batch number, specification, quantity, etc. Bound or boxed material).
Signs of stainless steel kitchenware are generally printed and listed.
2. Social backlog and stainless steel backlog. According to the length of the backlog and the quality of storage, there are generally two situations:
First, the backlog is not long and it is well kept. The processing unit not only keeps the original or copy of the quality certificate, but also has a complete and clear mark on the steel or packaging. For the identification of this kind of stainless steel, it is also necessary to check the signs on the steel or packaging according to the quality certificate.
The other is that the backlog is long, the storage is not perfect, there is no quality certificate, and the signs on steel or packaging are not obvious or fall off. For the identification of this kind of stainless steel, it is mainly necessary to conduct in-depth investigation and study and consult the original documents of the processing unit. Generally speaking, invoices and other original documents are marked with steel numbers. If there is no record of steel grade, it is necessary to consult the local price information at that time to determine the steel grade at the price. This is an effective method to determine the steel grade, but it is often prone to arrogance. Therefore, it is necessary to master the identification method of physical objects.
Physical identification is a concrete method to determine whether a commodity (including whole material, scrap, waste, etc.) is stainless steel and what kind of stainless steel it belongs to with the help of simple instruments when the steel grade (No.) is unknown.
It should be pointed out that sensory identification can not distinguish specific steels (types), but can only basically distinguish three categories: chromium stainless steel, chromium-nickel stainless steel and chromium-manganese-nitrogen stainless steel. The identification methods are as follows:
(1) color recognition
The surface color of stainless steel after pickling is silvery white and smooth: the color of Cr-Ni stainless steel is silvery white and emerald; Chrome stainless steel is white and slightly gray; The color of Cr-Mn-N stainless steel is similar to that of Cr-Ni stainless steel. Surface colors of stainless steel without pickling: chrome nickel steel is brownish white, chrome steel is brownish black, and chrome manganese nitrogen is black (these three colors refer to the colors with heavy oxidation). Cold-rolled non-annealed Cr-Ni stainless steel with silvery white reflective surface.
(2) Identification with copper sulfate
Remove the oxide layer from the steel, drop a drop of water on it and wipe it with copper sulfate. If it does not change color after wiping, it is generally stainless steel; If it turns purple, high manganese steel is nonmagnetic, while ordinary steel or low alloy steel is magnetic.
For special steel grades, we still need to use the following three methods to identify them.
(3) identify with a magnet
Magnets can basically distinguish two kinds of stainless steel. Because chromium stainless steel can be attracted by magnets in any state; Chromium-nickel stainless steel is generally non-magnetic in annealed state, and some will be magnetic after cold working. But high manganese steel with high manganese content is nonmagnetic; The magnetic properties of Cr-Ni-N stainless steel are complicated: some are nonmagnetic, some are magnetic, some are nonmagnetic in the longitudinal direction and some are magnetic in the transverse direction. Therefore, although magnets can basically distinguish chromium stainless steel from chromium-nickel stainless steel, they cannot correctly distinguish some special steel grades, let alone specific steel grades.
(4) Identification by annealing method.
Cold-worked Cr-Ni stainless steel, if magnetic, can be burned into small pieces in fire, let it cool naturally or put into water (annealing). Generally speaking, after annealing, the magnetism will obviously weaken or disappear completely. However, some Cr-Ni stainless steels, such as Cr 18Ni 1Si4alti steel and Cr2 1Ni5Ti steel, contain more ferrite elements, and a considerable part of their internal structures are ferrite. Therefore, it is magnetic even in the hot working state.
(5) Identification of wear
Grinding identification is to grind stainless steel on a grinding machine and observe its sparks. If the spark is streamlined and has many dense knots, it is high manganese steel or manganese-nitrogen steel with high manganese content; If there is no knot, it is chrome steel or chrome-nickel stainless steel.
(6) Chemical qualitative identification method
Chemical qualitative method is an identification method to identify whether magnetic stainless steel contains nickel. The method is to dissolve a small piece of stainless steel in aqua regia, dilute the acid solution with clear water, add ammonia water for neutralization, and then gently inject nickel reagent. If there is a red flannelette floating on the liquid surface, it means that stainless steel contains nickel; If there is no red velvet substance, it is proved that stainless steel does not contain nickel (however, due to the low nickel content in stainless steel, which is generally only a few percent, it is difficult to reveal or determine how much nickel is contained, and it is generally necessary to conduct many experiments with standard samples to master it).
The above identification method shows that the identification of stainless steel by induction tube not only requires many comprehensive tests, but also the test results can only determine a certain stainless steel, but can not determine which alloy elements and specific content are contained in the steel. So at present, the methods of sensory evaluation are far from perfect, some of them may be wrong, and there are many physical phenomena, which need further discussion.
The best way to correctly distinguish stainless steel brands is to conduct in-depth investigation and study, and ask relevant testing units to conduct testing and judgment. This is the fundamental way to correctly distinguish the grade and quality of stainless steel.
How to choose stainless steel kitchen utensils?
A, choose manufacturers with production, operation and gas appliance inspection qualifications. Meidu Electric's products are all qualified and trustworthy!
B, shop around, don't listen to one side of the story, to prevent blind purchase, intermediate kickbacks and other phenomena that waste people and money.
C, manufacturers often have advantages over store products: price advantage, tailor-made advantage, service advantage (pre-sale, in-sale and after-sale), consulting service advantage and technical service advantage.
D, it is best to contact the manufacturer directly, or take necessary contact measures to prevent counterfeiting, covert crossing, borrowing and other phenomena, resulting in unnecessary economic consumption.
E, stainless steel kitchenware, it is best to ask the manufacturers who join the activity to make a plan, and then summarize the comprehensive plan, and summarize a relatively complete plan according to their own needs.
2. Simple identification of product quality:
1), internal structure of gas appliance products: in the production process of qualified products, internal structures are mixed, such as the fan is connected with the air duct instead of directly; The internal structure attaches importance to the durability, stability and safety of products. Another example is the seafood steamer. It can be seen from the back of the product whether there is a galvanized steam pipe connection. If not, use the stainless steel plate of the steamer itself as the steam flow tube. The pressure resistance of stainless steel plate is far less than that of galvanized steam pipe, which will be dangerous in use.
2) Feet and solder joints of counter products: There are 38mm and 5 1mm common feet in the market, but the prices are far apart. Some merchants do not declare the tripod diameter when making plans, which increases their extra profits. The welding of legs and rungs should be fully welded, otherwise it will fall off easily.
3) Smoke exhaust products: this link is the most easily tampered with place, and the price per square meter in the market is frequent. After all, buyers have no way to know how many square meters a smoke hood and a smoke pipe will use; It is best to ask for the plan according to the price per meter.
4) Material of steel: The easiest way to identify stainless steel used in kitchenware products is to use magnets.
5) Food processing products: we can learn from the evidence of mechanical and electrical products in China.
How about stainless steel kitchenware?
Improper use of stainless steel tableware will lead to the gradual accumulation of trace metal elements in stainless steel in human body, which will endanger human health when it reaches a certain limit. Therefore, when using stainless steel kitchenware and tableware, we must pay attention to the following points:
Stainless steel is made of Fe-Cr alloy and other trace elements. Compared with other metals, it has good metal properties and corrosion resistance, and the made utensils are beautiful and durable. Therefore, more and more are used to make kitchen utensils, and gradually enter most families.
However, if users lack relevant knowledge and use it improperly, trace metal elements in stainless steel will accumulate slowly in human body, which will endanger human health to a certain extent. Therefore, when using stainless steel kitchenware and tableware, we must pay attention to the following points:
1, salt, soy sauce, vegetable soup etc. It is not suitable for long-term storage, because these foods contain a lot of electrolytes. If stored for a long time, stainless steel will react electrochemically with these electrolytes like other metals, dissolving toxic metal elements.
2. Traditional Chinese medicine can't be decocted in stainless steel vessels, because traditional Chinese medicine contains many alkaloids, organic acids and other components, especially under heating conditions, it is difficult to avoid chemical reaction with it, which will invalidate the medicine and even generate some more toxic compounds.
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