200 series stainless steel
Stainless steel is divided into five categories according to its metal structure: austenitic stainless steel, ferritic stainless steel, austenitic-ferritic (duplex) stainless steel, martensitic stainless steel and precipitation hardening stainless steel. There is a large amount of circulation in the market. The stainless steel used to make building components, decorative parts, vehicle structures, guardrails, household appliances components and shells, newsstands, telephone booths, dining utensils, medical appliances, etc. is mainly austenitic stainless steel. Coupled with a large number of industrial uses, the output (or consumption) of austenitic stainless steel accounts for approximately 75% to 80% of the total output (or consumption) of stainless steel.
According to its chemical composition, austenitic stainless steel is divided into two series: chromium-nickel series (300 series in the United States) austenitic stainless steel and chromium-manganese series (200 series in the United States) austenitic stainless steel.
Chromium-manganese (200 series) austenitic stainless steel is developed on the basis of chromium-nickel austenitic stainless steel, adding manganese and (or) nitrogen to the steel instead of the precious metal nickel element. Its austenitic element, In addition to manganese, there is nitrogen, and there is generally an appropriate amount of nickel (4% to 6%). Manganese in steel stabilizes austenite. Because nitrogen strongly forms and stabilizes austenite and has a good solid solution strengthening effect, which improves the strength of austenitic stainless steels, this series of stainless steels are suitable for heavy loads without high requirements for corrosion resistance. Used on equipment and components.
During World War II, the use of nickel as a strategic material was strictly controlled in various countries. In order to solve the dilemma of a serious shortage of nickel supply, the United States first developed 200 series stainless steel products with low nickel content as an emergency and supplement to 300 series products. Under certain historical conditions, the positive significance of the development and use of this product is self-evident.
However, as European and American countries continue to improve their understanding of this product, it has been found that its performance has great limitations. It has been used in a limited range. It is generally used in the field of structural support in a neutral and dry environment, such as lighting equipment and telecommunication poles. , Car frames and other general uses. Among the mature major producing and consuming countries of stainless steel, its production and consumption account for about 2% of the total amount of stainless steel.
According to the data, the names of the 200 series stainless steel grades produced by various countries and enterprises are different. Two grades of stainless steel, 201 and 202 (see the table below for specific chemical composition) originally developed by the United States. International standard ISO15510 and Chinese national standard both list grades with similar chemical composition.
In the 200 series stainless steel, sufficient manganese and nitrogen are used to replace nickel. The lower the nickel content, the higher the manganese and nitrogen required to form a 100% austenitic structure. Therefore, the 200 series stainless steel has austenitic structure. The non-magnetic properties of the steel. However, because the resistance to intergranular corrosion and pitting corrosion is significantly lower than that of the 300 series stainless steel, the scope of application has limitations.
① The biggest advantage of 200 series stainless steel is that it is cheaper than 300 series stainless steel.
②Under the premise of weak corrosion, ASTM202 stainless steel can almost completely replace 304 stainless steel;
③The utilization is relatively common, and it is widely used in building decoration, dining and kitchenware, sanitary equipment and appliances, household appliances, transportation, and equipment and parts of the industry.
① Compared with 304 and 200 series stainless steel, the corrosion resistance performance is worse;
②The workability of 200 series stainless steel is far inferior to that of 304 stainless steel;
③ Wastes are difficult to receive and take over. If it is not stated that they are 200 series wastes, they will become a high-risk waste steel mixed (hùn) raw material, causing the manganese content of the castings to far exceed the standard, and at the same time causing the steel mills to enter the furnace material composition is unstable;
④Remuneration status: The 200 series stainless steel is non-magnetic, and its appearance is similar to 304, which leads to the “offenders” in the sub-prime, fake “304” for sale, causing great loss to users.
Since 2001, 200 series stainless steels with steel grades J1 and J4 produced by a foreign factory have entered the Chinese market. Due to the high nickel price in recent years, the price of 300 series stainless steel is too high, and the output of the relatively cheap 200 series stainless steel has increased significantly. Since this product has the same non-magnetic properties as 300 series stainless steel products, it is easy to be confused with 300 series stainless steel. Therefore, a large number of 200 series stainless steel products counterfeiting 300 series stainless steel have appeared in the consumer field. In order to make huge profits, some domestic places have also taken the opportunity to follow suit. The production quality is more inferior, similar to 200 series stainless steel “ground steel” products. The domestic stainless steel market circulates in the brand of 201, J4, 202A, K-4, 200, 300 and other self-proclaimed “201” products. The domestic circulation continues to increase, accounting for nearly a quarter of the apparent consumption of my country’s stainless steel market. One or so.
Recently, the National Iron and Steel Research Institute conducted chemical composition inspection and pitting corrosion performance inspection of such products sampled on the market, and compared them with 409L, 439L, and 304 produced by large enterprises. The results show that the ingredients of the products sold on the domestic market under the name “201” do not meet the national or international 201 standards. The national and international standards stipulate the Cr content of 200 series stainless steel at 16%-18%, but these products The Cr content is less than 15%; the nickel content is specified in the national and international standards as 3.5% to 5.5%, and the nickel content of such products is less than 1%. In addition, the content of elements such as sulfur and copper is relatively high, and the content of elements such as manganese and phosphorus, which are especially harmful to the human body, is even higher. Through the pitting corrosion resistance test in neutral chloride (3.5% NaCl solution), the pitting corrosion resistance of these products is far lower than 304 and 439L.
Therefore, the stainless steel industry calls it a counterfeit 200 series.
In these 200 series stainless steels that do not meet the standard, due to the inability to add sufficient amounts of manganese and nitrogen, in order to form a 100% austenite structure (which can achieve non-magnetic), the amount of chromium added is artificially reduced. The product and the 300 series (chromium-nickel stainless steel) products are also “non-magnetic”, but it will inevitably lead to a decline in the corrosion resistance of stainless steel, that is, in order to obtain non-magnetic, the main characteristic of stainless steel-corrosion resistance is reduced.
Damage the interests of
The counterfeit and inferior 200 series and 300 series (chromium-nickel stainless steel) products are both “austenite” and are also “non-magnetic”, but the cost is very low. In order to obtain huge profits, some unscrupulous operators take advantage of consumers’ understanding of stainless steel materials. Misunderstandings, a large number of counterfeit 300 series products in the circulation operation, because the counterfeit and inferior 200 series stainless steel products have serious defects in the chemical composition design, corrosion resistance and other performances are not up to standard, so that the majority of consumers have suffered huge losses. Disturbed the normal market order.
According to market surveys in recent years, this type of product has been rusted within a short period of time after being put into use. It can be seen everywhere in a residential area in Zhuhai City, Guangdong, a hotel in Shanxi, and Shanghai Maglev Station. Severely corroded guardrails, water tanks, street light poles, telephone booths, etc. It has brought great harm to consumers, seriously damaged the interests of consumers, and seriously damaged the image of stainless steel products in the minds of consumers.
Scientific experiments have shown that once manganese enters the human body, it can cause varying degrees of damage to multiple systems such as nerves, immunity, endocrine, and reproduction. Such counterfeit and inferior 200-series stainless steel materials that are flooding the market have metal manganese content 4-5 times that of 300-series materials. What worries people even more is that these low-quality 200-series materials with high manganese content have been widely used in common people’s daily necessities, such as kitchenware, tableware, etc., which will pose a direct hazard to human health.
a waste of resource
As we all know, stainless steel has always been called a “green product” that is 100% recyclable and will not cause environmental pollution. It is not only an environmentally friendly product, but also a relatively value-preserving product.
Due to the high phosphorus content of counterfeit 200 series stainless steel, especially the 200 series stainless steel from a certain country, according to the test of an authoritative organization, the maximum phosphorus content reached 0.075% and 0.09%, which is 2-3 times the maximum phosphorus content of the Chinese standard. , And the phosphorus content in stainless steel is difficult to remove in scrap steel recycling (re-smelting), especially some small stainless steel steelmaking enterprises that use induction electric furnaces as melting furnaces. More than 80% of the raw materials come from stainless steel scrap. As the phosphorus content accumulates, the higher the phosphorus content, stainless steel will become a non-recyclable material, and the resulting waste of resources is huge, and the blow to the entire stainless steel industry is fatal.
The high copper content is also a factor that has a serious impact on the recycling of scrap steel. Copper is a harmful element to most stainless steel grades. Once it enters the recycling process, it will bring irreparable damage to the product quality of regular stainless steel manufacturers.
Nickel is a scarce resource on a global scale. my country’s nickel resources are even more lacking. The actual corrosion resistance of counterfeit 200 series stainless steels is much lower than 304, even lower than 409L without nickel, but it still consumes more than 1% of nickel resources. It is a great waste of precious metal resources that are in short supply globally.
①Spectroscopy: Use a high-voltage electrical excitation spectroscopy gun (the instrument is small in size and easy to carry) to perform spectroscopy to qualitatively distinguish the types of steel elements and their approximate levels.
②Chemical reagent: There is a special reagent called nickel qualitative solution, which is dropped on the surface of stainless steel, and it oxidizes instantly after energization to produce light white or light yellow, indicating that the stainless steel does not contain nickel; it produces light rose red and immediately fades to dark The yellow color indicates that the stainless steel contains about 1%-2% nickel; it produces a rose red color and does not fade, indicating that the stainless steel contains more than 4% nickel. The brighter the rose red color indicates the higher the nickel content.
③Color: The surface color of pickled stainless steel: 300 series stainless steel is silvery white and jade color; 400 series stainless steel is white and slightly gray, with weak luster; 200 series stainless steel is similar in color to 300 series stainless steel, but slightly lighter. The surface color of stainless steel that has not been pickled: 300 series stainless steel is brown-white; 400 series stainless steel is brown-black; 200 series stainless steel is black.
④ Sparks: Spark identification is to grind stainless steel on a grinder and observe the sparks. If the spark is streamlined and has more dense knots, it is 200 series stainless steel with higher manganese content; if there are no knots, it is 300 or 400 series stainless steel.
The above-mentioned methods are simple and easy to implement, but there are some errors, especially the third and fourth methods are judged entirely by visual experience, and the errors may be even greater. The most accurate method is of course the inspection report issued by a qualified inspection agency.
Due to the demand characteristics of the Chinese market, although the 200 series stainless steel has many disadvantages, it has the advantage of low cost. Especially in the case of the soaring nickel price, the 200 series still has a considerable market share. How to maximize the strengths and avoid weaknesses of 200 series stainless steel products, and seek advantages and avoid disadvantages, this is a problem to be paid attention to. We think we should pay attention to the following aspects:
1. The first is to standardize the market. It is necessary to formulate a unified grade standard, appropriately use some steel with a nickel content of about 4%, and strictly limit steel with a nickel content of only 1% and a low chromium content. Stainless steel manufacturing enterprises strengthen product identification and strengthen stainless steel brand management.
2. Secondly, it is necessary to increase publicity to let downstream users clearly understand the harm caused by too low nickel content.
3. The domestic stainless steel production department also needs to increase research and development efforts, continue to develop smelting technology, and use products with better performance to eliminate inferior products in the 200 series. For example, when the nitrogen content in steel reaches 1%, its corrosion resistance will be greatly improved.
4. Consumers should be correctly guided to understand ferritic stainless steel (400 series), and the application of ferritic stainless steel should be promoted. Ferritic stainless steel generally does not contain nickel, and the cost is much lower than austenitic steel (300 series). Some of its performance is more than 200 series nickel manganese stainless steel.
Recommendations for consumers
Reasonably select 200 series stainless steel that meets national and international standards, and carefully identify true and false 200 series stainless steel.
There are two sides to the existence of things, and the same is true for the existence of 200 series stainless steel. Our country needs a large amount of stainless steel in social construction. Reasonable use of 200 series stainless steel that meets national and international standards will reduce construction costs and meet the requirements of building a conservation-oriented society. Its strength and wear resistance are stronger than 300 series stainless steel, and its price is low. It is suitable for structural support fields in neutral and dry environments, such as lighting equipment, telecommunication poles, automobile frames and other general uses.
In addition, 200 series stainless steel is also suitable for construction steel such as steel bars and rivets.
In order to protect the interests of consumers, we should correctly identify and resolutely resist the production, sale and use of counterfeit and inferior 200 series stainless steel.
201 stainless steel
201 stainless steel has certain acid and alkali resistance, high density, no bubbles, no pinholes, etc. It is used to produce high-quality materials for various watch cases and watchband back covers. Mainly used to make decorative tubes, industrial tubes, and some shallow stretched products.
(C) Carbon: ≤0.15
(Si) Silicon: ≤1.00
(Mn) Manganese: 5.5～7.50
(Cr) Chromium: 16.0～18.0
(N) Nitrogen: ≤0.25
(P) Phosphorus: ≤0.060
(S) Sulfur: ≤0.030
(Ni) Nickel: 3.5-5.5
China mainly has the following 200 series steel grades: J1, J3, J4, 201, 202. Later, there appeared 200 grades of steel with lower nickel content control. As for 201C, it was an extension of 201 developed by individual steel plants in China at this later stage. The national standard grade of 201 is: the old grade 1Cr17Mn6Ni5N, and the new grade: 12Cr17Mn6Ni5N 201C continues to reduce the content of nickel and increase the content of manganese on the basis of 201.
Tensile strength: 520MPa
Yield strength: 275MPa
Elongation: 55 to 60%
Modulus of elasticity: 29,000,000 psi, equivalent to: 203000MPa
Hardness requirements (Rockwell hardness) HRB≤100.
Density: .280lbs/cubic inch (density 7.93g/cm3)
201 stainless steel tube density
|Grade||Density (*103 kg/m3)||Grade||Density (*103 kg/m3)|
202 stainless steel
202 stainless steel is a kind of 200 series stainless steel, the national standard model is 1Cr18Mn8Ni5N. 202 stainless steel is widely used in building decoration, municipal engineering, highway guardrails, hotel facilities, shopping malls, glass handrails, public facilities and other places.
The 200 series stainless steel is a low-nickel high-manganese stainless steel with a nickel content of about 8% and a manganese content of about 8%. It is a nickel-saving stainless steel.
|Brand||Heat Treatment||Yield Strength Mpa||Tensile Strength Mpa||Elastic Modulus psi||HBS||HRB||HV|
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