Stainless steel door material has the characteristics of stainless steel, acid resistance, high temperature resistance, wear resistance and generally non-magnetic austenite. Stainless steel door material is a common advanced alloy steel.
Stainless steel door material has the characteristics of stainless steel, acid resistance, high temperature resistance, wear resistance and generally non-magnetic austenite. Stainless steel door material is a common advanced alloy steel.
Most of the stainless steel door materials we see everyday are nickel-chromium stainless steel with basically the same steel numbers of 302 and 304 and chromium stainless steel with 1-4 Cr13 (as ordinary people say, "stainless steel"). In our country, there are more than 100 varieties (steel grades) of stainless steel door materials, and the properties and values of different elements and contents in steel grades are also very different. Therefore, the identification of stainless steel door materials must be carefully studied, the steel mark must be clarified, and the comprehensive test and other methods can be used to correctly identify. At present, we mainly have the following methods to identify stainless steel materials:
the sources of stainless steel materials are usually orders from steel mills or imports from abroad, and the processing of goods overstocked by society. Different sources of stainless steel have different methods of identification.
1. To identify stainless steel ordered by imported or steel mills, you only need to check the steel or marks on packaging according to the quality certificate of imported or steel mills. The mark of stainless steel is generally used to print steel seals or spray prints on specific parts, or to tag outside the whole box and bundle of materials.
2. The society overstocked stainless steel. According to the length of the overstocking time and the quality of the storage, there are generally two situations: first, the overstocking time is not long, the storage is good, the original materials and signs are clear, just check the logo. The other is that the backlog time is long, the storage is not perfect, the original information is not wanted, and the logo is not clear. For the identification of this kind of stainless steel, we must master the identification method of the real object.
Physical identification is a specific method to determine whether stainless steel is stainless steel and what kind of stainless steel it belongs to with the help of simple appliances and senses according to the inherent physical and chemical properties of stainless steel.
It should be pointed out that sensory identification cannot distinguish specific steel (species) numbers, but can only basically distinguish chromium stainless steel, chromium nickel stainless steel and chromium manganese nitrogen stainless steel. The identification methods are as follows:
use copper sulfate to identify
remove the oxide layer on the steel, put a drop of water and wipe it with copper sulfate. If it does not change color after wiping, it is generally stainless steel; If it turns purplish red, the non-magnetic one is high manganese steel, magnetic ones are generally ordinary steel or low alloy steel.
Use magnet to identify
magnet can basically distinguish two types of stainless steel. Because chromium stainless steel can be attracted by magnet in any state; Chromium nickel stainless steel is generally non-magnetic in annealing state, and some will be magnetic after cold processing. However, high manganese steel with higher manganese content is non-magnetic; The magnetic condition of chromium-Nickel-nitrogen stainless steel is more complicated: some are non-magnetic, some are magnetic, some are non-magnetic in longitudinal plane and magnetic in transverse plane. 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.
Color identification
after pickling of stainless steel door materials, the surface color is silvery white and clean: Chrome-nickel stainless steel is silvery white and Jade; Chrome stainless steel is slightly gray and shiny; The color of chrome-manganese-nitrogen stainless steel is slightly light similar to that of chrome-nickel stainless steel. The surface color of stainless steel without pickling: Chrome nickel steel is Brown White, chrome steel is Brown black, Chrome Manganese Nitrogen is black (these three colors refer to the color with heavy oxidation). Cold rolled chromium-nickel stainless steel without annealing, the surface is silvery white and reflective.
For steel grades with special properties, we need to adopt the following three methods to identify them.
Chemical qualitative identification
chemical qualitative method is a method to identify whether the magnetic stainless steel door material contains nickel. The method is to dissolve small pieces of stainless steel in aqua regia, dilute the acid with clean water, add ammonia and then gently inject nickel reagent. If there is a red velvet substance floating on the liquid surface, it indicates that the stainless steel contains nickel; If there is no red velvet substance, it proves that there is no nickel in the stainless steel (but due to the low nickel content in the stainless steel, generally, it is only a few percent, and the content of nickel is not easy to reveal or determine. Generally, it can only be mastered after many experiments with standard samples).
Identification by annealing
for cold-processed chromium-nickel stainless steel, if it is magnetic, it is advisable to burn small pieces in the fire to allow them to cool naturally or put them into water (annealing). Generally speaking, after annealing, the magnetic properties will be significantly weakened or completely disappeared. However, some chromium-nickel stainless steels, such as Cr18Ni11Si4AlTi steel and Cr21Ni5Ti steel, contain more ferrite elements, and a considerable part of their internal structure is ferrite. Therefore, it is magnetic even in the hot working state.
Buffing patterns identification
buffing patterns identification is to grind stainless steel on grinder to see its spark. For example, if the spark is streamlined and there are more dense knots, it is high manganese steel or Manganese Nitrogen steel with higher manganese content; If there is no knots, it is chromium steel or chromium nickel stainless steel.
According to the above identification methods, using the sensor tube to identify stainless steel door materials not only needs several methods to conduct comprehensive tests, but also the test results can only determine certain types of stainless steel, it is impossible to determine which kinds of alloy elements and specific contents are contained in the steel. Therefore, the method of sensory identification is extremely imperfect at present. Some of them may be wrong and there are many physical phenomena. However, they only know what it is for, which needs further discussion.
The best way to correctly distinguish stainless steel door steel grades is to conduct in-depth investigation and research. Please ask relevant inspection units to conduct inspection and judgment. This is the fundamental method to correctly distinguish stainless steel door steel grades and quality.
