There are many different ways to identify stainless steel, common ways to identify stainless steel materials are the following.
First, according to the source of stainless steel to identify the stainless steel materials are the following methods.
1, to identify the imported or steel factory ordered stainless steel material, generally only according to the quality certificate provided by the import or steel factory, check the steel or packaging on the mark can be. The quality certificate is the supplier’s confirmation and guarantee of the test results of the batch of products. Therefore, the quality certificate must state not only the name, specification, number of delivered parts, weight and delivery status of the materials, but also the results of all the specified warranty items. Likewise, for ease of management, to avoid confusion and to prevent accidents of use due to confusion, the production plant marked the material or packaging with signs such as number, lot number, condition, specification, quantity and production plant code. It shall be marked in a manner consistent with the contents of the certificate of quality.
Commonly used signage methods are mainly the following three kinds: coloring (painted on the specified part of the material to indicate the color of its grade), printing (steel printing or spray printing on the specified part of the material to indicate the material’s grade, specification, tank number, etc., often used on thick steel plate or large and medium section steel), hanging (in bundles or boxes of material, hanging signs indicating the grade, lot number, specification, quantity, etc.). Signs made of stainless steel round steel are generally printed and hung.
2. Social overstock of stainless steel. According to the length of time and custody of the overstock backlog, there are generally two situations: one is the overstock backlog time is not long, custody and good, the processing unit not only keeps the original quality certificate or copy, but also the steel or packaging on the logo is complete and clear. For the identification of this stainless steel material, it is also sufficient to check the steel or the markings on the packaging according to the quality certificate. The other is a long backlog, imperfect storage, neither a certificate of quality nor a logo on the steel or packaging that is no longer visible or falling off. For the identification of this type of stainless steel, the main thing is to carry out an in-depth investigation and research, to the processing unit to check the original documents. Generally, invoices and other original documents are marked with steel numbers, etc. If the steel number is not recorded, it is also necessary to consult the local price information available at the time to determine the steel number by price. This is a more effective way to determine the steel number, but it is often easy to overstate the case. Therefore, it is necessary to master the method of identification of the object.
II. Methods for identifying stainless steel grades (numbers) based on stainless steel.
The three main categories of stainless steel, chromium stainless steel, chromium nickel stainless steel and chromium manganese nitrogen stainless steel, are distinguished as follows.
1、Color identification
The surface of the acid-washed stainless steel is silvery-white and smooth: chromium-nickel stainless steel is silvery-white with a jade color; chromium stainless steel is slightly grayish-white with a weak luster; chromium-manganese nitrogen stainless steel is similar to chromium-nickel stainless steel in color and slightly lighter. Surface color of stainless steel without acid wash: chromium-nickel steel is brownish-white, chromium steel is brownish-black, chromium-manganese nitrogen is black (these three colors refer to the more heavily oxidized color). Cold rolled unannealed chrome-nickel stainless steel with a silver-white reflective surface.
2、Insert stone identification
Magnet energy basically distinguishes between two types of stainless steel. Because chrome stainless steel can be attracted to magnets in any state; chrome-nickel stainless steel is generally non-magnetic when annealed, and some will be magnetic after cold processing. However, high manganese steel is non-magnetic; chromium-nickel-nitrogen stainless steel magnetic situation is more complex: some non-magnetic, some magnetic, some longitudinal non-magnetic and cross-sectional magnetic. Thus, while magnets can make a basic distinction between chromium stainless steel and chromium-nickel stainless steel, they cannot correctly distinguish between some steel grades of special properties, much less specific steel numbers.
3、Copper sulfate identification
Remove the oxide layer on the steel, put a drop of water, rub with copper sulfate, after rubbing, such as not discolored, generally stainless steel; such as purplish red, non-magnetic for high manganese steel, magnetic generally ordinary steel or low alloy steel. For special properties of steel, we also need to take the following three ways to identify. Grinding is the process of grinding stainless steel on a sander and watching it spark. If the spark is streamlined and has more dense knots, it is high manganese steel or manganese nitrogen steel with high manganese content; if no knots, it is chromium steel or chromium-nickel stainless steel.
4、Annealing method identification
Cold machined chrome-nickel stainless steel, if magnetic, can be burned red in a fire in small pieces and allowed to cool naturally or put into water (annealed), generally, after annealing the magnetism will be significantly weakened or disappear completely. However, some chromium-nickel stainless steels, such as Cr18Ni11Si4AlTi steel and Cr21Ni5Ti steel, have a significant portion of their intrinsic tissues as ferritic elements due to the high content of ferritic elements in the steel. Therefore, it is magnetic even in the heat-processed state.
5. Identification by chemical qualitative method
The chemical characterization method is to identify whether the magnetic stainless steel contains nickel in an identification method. The method is to dissolve small pieces of stainless steel in king water, wash down the acid with clean water, add ammonia to neutralize, and then gently inject nickel reagent. If there is a red fluffy substance floating on the liquid surface, it means that the stainless steel contains nickel; if there is no red fluffy substance, it means that there is no nickel in the stainless steel (but due to the low amount of nickel in stainless steel, generally only a few percent, the content of nickel is not easy to reveal or determine how much, generally have to use the standard sample experiment several times before mastering).
In summary: The above identification methods indicate that the identification of stainless steel with induction tube, not only with several methods of comprehensive testing, and its test results can only determine a certain type of stainless steel, can not determine which steel contains several alloy elements and specific content.
Third, the identification of specific materials of stainless steel, such as 202, 201, 304, 304L, 316, 316L, 310S and other materials of stainless steel round steel identification
Identify the specific material of stainless steel is mainly divided into qualitative detection, qualitative semi-quantitative detection, full quantitative detection of these three.
1, the general method of qualitative detection of stainless steel can be used for rapid determination of stainless steel liquid Ni qualitative, low Ni (200), Ni2 (201), Ni4 (202), Ni6 (301), Ni8 (304), Ni14 (309, 316L), Ni20 (310), Ni40, Ni60, Mo2 (316), stainless steel identification fluid, manganese steel and other stainless steel materials, that is, the stainless steel identification potion.
2、Full quantitative method, there are many testing institutions in the market, or the use of ICP plasma chromatography test, this method is very accurate and can issue an authoritative test report. But detection is costly ($100 for an element), has a long cycle time and requires disruption analysis.
3, qualitative and semi-quantitative methods: it is recommended to do spectral analysis, general steel factory will use spectrometer to do material analysis report. The error of the hand-held spectrometer is 0.1% for nickel, which is non-destructive and can basically meet the general material identification. The limitation of this method is that it cannot test for non-metals like C, Si, P, etc. However, it is perfectly capable of detecting samples of alloy material.
