Food class anti corrosion 304 stainless steel plate
304 Stainless steel is a common stainless steel material, the density of 7.93 g / cm³; also called 18 / 8 stainless steel, meaning contains more than 18% chromium and more than 8% nickel; high temperature resistance of 800℃, with high processing performance, high toughness characteristics, widely used in industrial and furniture decoration industry and food and medical industry. However, it should be noted that the food grade 304 stainless steel compared with the ordinary 304 stainless steel, its content index is more strict. For example: the international definition of 304 stainless steel is basically mainly containing chromium 18% -20% nickel 8% -10%, but the food grade 304 stainless steel is containing 18% chromium and nickel 8% chromium, allowing a certain range of fluctuations, and limit the content of various heavy metals. In other words, the 304 stainless steel is not necessarily a food grade 304 stainless steel
Among the common labeling methods in the market are 06Cr19Ni10, SUS304, among which 06Cr19Ni10 generally means national standard production, 304 generally means ASTM standard production, and SUS304 indicates daily standard production.
The 304 Is a universal stainless steel, which is widely used to make the equipment and machine parts requiring good comprehensive performance (corrosion resistance and molding performance). To maintain the inherent corrosion resistance of stainless steel, steel must contain over 18% chromium and over 8% nickel.304 Stainless Steel is a plate of stainless steel manufactured to American ASTM standards
physical property
Tensile strength b (MPa) 515-1035
Conditional yield strength of 0.2 (MPa) 205
Elongation rate: 5 (%) 40
Section shrinkage rate (%)?
Hardness: 201HBW; 92HRB; 210HV
Density (20℃, g / cm³): 7.93
Melting point (℃): 1398~1454
Specific heat capacity (0~100℃, KJ · kg-1K-1): 0.50
Thermal conductivity (W · m-1 · K-1): (100℃) 16.3, (500℃) 21.5
Line expansion coefficient (10-6 · K-1): (0~100℃) 17.2, (0~500℃) 18.4
Respetivity (20℃, 10-6 Ω·m2 / m): 0.73
Longitudinal elastic modulus (20℃, KN/mm2): 193
product standard
For 304 stainless steel, the Ni element in its component is very important, which directly determines the corrosion resistance of 304 stainless steel and its value.
The most important elements in the 304 are Ni and Cr, but they are not limited to them. Specific requirements are specified by the product standards. The industry commonly determines that as long as the Ni content is greater than 8%, and the Cr content is greater than 18%, it can be considered as 304 stainless steel. This is why the industry calls this kind of stainless steel 18 / 8 stainless steel. In fact, the relevant product standards have a very clear regulation for the 304, and these product standards for different shapes of stainless steel and some differences. Here are some common product standards and tests.
In order to determine whether a material is 304 stainless steel, it must meet the requirements of each element in the product standard, as long as there is a material that does not meet, it cannot be called 304 stainless steel.
1. ASTM A276 (Standard Specification for Stainless Steel Bars bar and Shapes profile)
304 C Mn P S Si Cr Ni
Requirement,% 0.08 2.00 0.045 0.030 1.00 18.020.0 8.0-11.0
2. ASTM A240 (Chromium and Chromium-Nickel Stainless Steel Plate sheet, Sheet sheet, and Strip strip for Pressure essels and for General Applications)
304 C Mn P S Si Cr Ni N
Requirement,% 0.07 2.00 0.045 0.030 0.75 17.519.5 8.010.5 0.10
3. JIS G4305 (cold-rolled cold-rolled stainless steel plate sheet, sheet sheet and strip strip)
SUS 304 C Mn P S Si Cr Ni
Requirement,% 0.08 2.00 0.045 0.030 1.00 18.020.0 8.0-10.5
4. JIS G4303 (Stainless steel bars stainless steel rod)
SUS 304 C Mn P S Si Cr Ni
Requirement,% 0.08 2.00 0.045 0.030 1.00 18.020.0 8.0-10.5
The above four criteria are just a few common criteria, in fact, ASTM and JIS have mentioned more than these 304 criteria. In fact, each standard of 304 requirements are not the same, so to determine whether a material is 304, the accurate expression should be said whether it meets the 304 requirements of a product standard. Material certificate should generally issue the following type of report:
Detailed standard specification comparison: until 2015-12-08
No. Standard / S30400 C Mn P S Si Cr Ni N Cu
1 ASTM A276/A276M-15 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
2 ASTM A959-11 0.07 2.00 0.045 0.030 1.00 17.5-19.5 8.0-11.0
3 ASTM A240/A240M-15a 0.07 2.00 0.045 0.030 0.75 17.5-19.5 8.0-10.5
4 ASTM A182/A182M-15 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0 0.10
5 ASTM A193/A193M-15 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
6 ASTM A269/A269M-15 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
7 ASTM A312/A312M-15a 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
8 ASTM A320/A320M-15a 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
9 ASTM A403/A403M-15 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
10 ASTM A493-09(2013) 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-10.5 0.10 1.00
11 ASTM A554-15a (MT-304) 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
12 JIS G4303:2012 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-10.5
13 JIS G4304:2012 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-10.5
14 JIS G4305:2012 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-10.5
15 GB/T 20878-2007 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
System description:
304 stainless steel is the most widely used chromium-nickel stainless steel, as a versatile steel, with good corrosion resistance, heat resistance, low temperature strength and mechanical characteristics; stamping, bending and other heat machining is good, no heat treatment hardening phenomenon (use temperature-196℃ ~800℃). Corrosion resistance in the atmosphere, if it is an industrial atmosphere or heavy pollution area, the need to timely clean to avoid corrosion. Suitable for the processing, storage, and transportation of food products. Good machining performance and weldability. Plate heat exchangers, bellows, household goods (class 1,2 tableware, cabinets, indoor pipelines, water heaters, boilers, bathtub), auto accessories (windshield wipers, mufflers, mold products), medical appliances, building materials, chemistry, food industry, agriculture, ship parts, etc. The content of strictly controlled 304 stainless steel, can also be known as food grade 304 stainless steel
Most use requirements are to maintain the original appearance of the building for a long time. When determining the type of stainless steel to be selected, the main consideration is the aesthetic standards required, the corrosive nature of the local atmosphere and the cleaning system to be adopted. However, other applications are increasingly only looking for structural integrity or impermeability. For example, the roofs and side walls of industrial buildings. In these applications, the construction cost of the owner may be more important than the aesthetic, and the surface is not very clean. Use of a 304 stainless steel in a dry indoor environment works quite well. But, in the countryside and in the city to maintain its appearance outside, it needs to be cleaned often. In heavily polluted industrial and coastal areas, surfaces can be very dirty and even rust.
But to obtain the aesthetic effect in the outdoor environment, it is necessary to use nickel-containing stainless steel. Therefore, 304 stainless steel is widely used in curtain wall, side wall, roof and other architectural purposes, but in the severely eroded industrial or Marine atmosphere, it is best to use 316 stainless steel. Stainless steel sliding door, people have fully realized the advantages of using stainless steel in structural applications. Several design guidelines include the 304 and 316 stainless steel. This steel is included in the European Code because the 2205 "duplex phase" combines high atmospheric corrosion resistance with high tensile strength and elastic limit strength. Product shapes Actually, stainless steel is manufactured in full standard metal shapes and sizes, and there are many special shapes. The most commonly used products are made of sheet plate and strip steel, and also use medium-thickness plate to produce special products, for example, to produce hot-rolled structural steel and extruded structural steel. There are also round, elliptical, square, rectangular, and hexagonal welded pipes or seamless steel pipes and other forms of products, including profiles, bars, wires, and castings.
product standard
International stainless steel marking method
The American Iron and Steel Institute uses three digits to mark various standard-grade malleable stainless steel.among:
The ① austenitic stainless steel is marked with the 200 and 300 series number, for example, certain more ordinary austenitic stainless steel is marked with 201,304,316, and 310,
② ferrites and martensite-type stainless steel are indicated in the numbers of the 400 series.
③ iron body stainless steel is marked with 430 and 446, martensite stainless steel is marked with 410,420, and 440C,
The ④ duplex (austenitic-ferrite), stainless steel, precipitated and hardened stainless steel, and high alloys with less than 50% iron content are usually named by the patent name or trademark.
4). Standard classification and grading
4-1 Classification: ① national standard GB ② industry standard YB ③ local standard ④ enterprise standard Q / CB
4-2 Classification: ① Product standard ② Packaging Standard ③ method Standard ④ basic standard
4-3 Standard level (three levels): Y: International advanced level Level I: International general level H: domestic advanced level
4-4 National standard
GB1220-2007 Stainless Steel Bar (Grade I) GB4241-84 Stainless Steel Welding Plate Park (Grade H)
GB4356-2002 Stainless Steel Welding Plate Park (Grade I) GB1270-80 Stainless steel pipe (Grade I)
GB12771-2000 Stainless Steel welded pipe (Grade Y) GB3280-2007 Stainless Steel cold plate (Grade I)
GB4237-2007 Stainless Steel Hot Plate (Class I) GB4239-91 Stainless Steel Cold Belt (Class I)
etching method
Etching processing method, is in the stainless steel surface using screen printing acid-resistant steel protective film, and then with ferrous chloride liquid etching, to form an artistic pattern.
Spray color method
Color spray method is the injection of color particles after screen printing, forming the pear skin-like surface, forming an artistic pattern.
process engineering
The process of stainless steel products color spraying art processing process is: stainless steel products silk printing etching alkali processing wire printing oxidation coloring alkali processing finished products.
Stainless steel products etching art processing process is: stainless steel products silk printing etching alkali processing oxidation coloring finished products.
The chemical coloring method of stainless steel does not use pigments and dyes, but the stainless steel is soaked in the heated concentrated chromium sulfate solution for chemical coloring, which is characterized by good food resistance. The ink used in this processing method should have a very strong acid resistance, and generally use the UV sulfide ink with special properties suitable for the treatment process.
Stamping processing
Stainless steel products, especially stainless steel belt, many times the most original factory processing method is to use punch for stamping products. Stressing includes straight punching and stretching two ways, generally the hardness of less than 1 / 2 is the use of stretching and bending, the hardness is higher than 1 / 2 partial hard, are straight blunt.
Rusty cause
304 Stainless steel material rust phenomenon, may have the following reasons:
chloridion
Chlorine is widespread, such as salt / sweat / sea / sea / soil, etc. Stainless steel in the presence of chloride ions in the environment, corrosion is fast, even more than ordinary low carbon steel. So the use of stainless steel environment requirements, and need to often wipe, remove dust, keep clean and dry. There is an example in the United States: an enterprise with an oak container containing a chlorine ion solution, the container has been used for nearly 100 years, in the 1990s plan to replace, because the oak material is not modern enough, using stainless steel replacement 16 days after the container due to corrosion leakage.
solution treatment
Alloy elements do not dissolve into the matrix, resulting in a low alloy content of the matrix tissue and poor corrosion resistance.
intercrystalline corrosion
