Common professional knowledge related to stainless steel

1. Stainless steel hot rolled steel plate
Stainless steel hot-rolled steel plate is a stainless steel plate produced by hot rolling process. Those with a thickness of not more than 3mm are thin plates, and those with a thickness greater than 3mm are thick plates. Used in chemical, petroleum, machinery, shipbuilding and other industries to manufacture corrosion-resistant parts, containers and equipment. Its classification and grades are as follows:
1 . Austenitic steel
(1)1Cr17Mn6Ni15N; (2)1Cr18Mn8Ni5N; (3)1Cr18Ni9; (4)1Cr18Ni9Si3; (5)0Cr18Ni9;
(6)00Cr19Ni10; (7)0Cr19Ni9N; (8)0Cr19Ni10NbN; (9)00Cr18Ni10N; (10)1Cr18Ni12;
(11) 0Cr23Ni13; (12)0Cr25Ni20; (13) 0Cr17Ni12Mo2; (14) 00Cr17Ni14Mo2;
(15) 0Cr17Ni12Mo2N; (16) 00Cr17Ni13Mo2N; (17) 1Cr18Ni12Mo2Ti; (18) 0Cr18Ni12Mo2Ti;
(19) 1Cr18Ni12Mo3Ti; (20) 0Cr18Ni12Mo3Ti; (21) 0Cr18Ni12Mo2Cu2;
(22) 00Cr18Ni14Mo2Cu2; (23) 0Cr19Ni13Mo3; (24) 00Cr19Ni13Mo3; (25) 0Cr18Ni16Mo5;
(26) 1Cr18Ni9Ti; (27) 0Cr18Ni10Ti; (28) 0Cr18Ni11Nb; (29) 0Cr18Ni13Si4
2 . Austenitic-ferritic steel
(30) 0Cr26Ni5Mo2; (31) 00Cr18Ni5Mo3Si2;
3． ferritic steel
(32) 0Cr13Al; (33) 00Cr12; (34)1Cr15; (35)1Cr17; (36)1Cr17Mo; (37)00Cr17Mo;
(38)00Cr18Mo2; (39)00Cr30Mo2; (40)00Cr27Mo
4. martensitic steel
(41) 1Cr12; (42) 0Cr13; (43); 1Cr13; (44) 2Cr13; (45) 3Cr13; (46) 4Cr13;
(47) 3Cr16; (48) 7Cr17
5. precipitation hardened steel
(49) 0Cr17Ni7Al
2. Stainless steel cold rolled steel plate
Stainless steel cold-rolled steel plate is a stainless steel plate produced by cold rolling process. The thickness is not more than 3mm, which is thin plate, and the thickness is more than 3mm, which is thick plate. It is used to make corrosion-resistant parts, pipelines, containers, medical equipment, ship equipment, etc. in petroleum and chemical industries. Its classification and grades are as follows:
1 . Austenitic steel
In addition to the same as the hot rolled part (29 types), there are: (1) 2Cr13Mn9Ni4(2)1Cr17Ni7(3) 1Cr17Ni8
2 . Austenitic-ferritic steel
In addition to the same as the hot rolled part (2 types), there are: (1) 1Cr18Ni11Si4AlTi (2) 1Cr21Ni5Ti
3． ferritic steel
In addition to being the same as the hot rolled part (9 types), there are also: 00Cr17
4. martensitic steel
In addition to being the same as the hot rolled part (8 types), there are also 1Cr17Ni2
5. Precipitation hardened steel: same as hot rolled part
3. Introduction to ferrite, austenite and martensite
As we all know, solid metals and alloys are crystals, that is, the atoms inside them are arranged according to certain rules. There are generally three ways of arrangement: body-centered cubic lattice structure, face-centered cubic lattice structure and close-packed hexagonal lattice structure. . Metals are composed of polycrystals, and their polycrystalline structures are formed during the metal crystallization process. The iron that makes up the iron-carbon alloy has two lattice structures: α-iron with a body-centered cubic lattice structure below 910 ℃, and Υ-iron with a face-centered cubic lattice structure above 910 ℃. If carbon atoms are squeezed into the iron lattice without destroying the lattice structure of iron, such a substance is called a solid solution. The solid solution formed when carbon dissolves into α-iron is called ferrite. Its carbon-dissolving ability is extremely low, and its maximum solubility does not exceed 0.02%. The solid solution formed when carbon dissolves into Y-iron is called austenite, and its carbon-dissolving ability is high, up to 2%. Austenite is the high-temperature phase of iron-carbon alloys.
The austenite formed when steel is at high temperature becomes unstable supercooled austenite when it is supercooled below 727°C. If the cooling rate is super-cooled below 230°C, the carbon atoms in the austenite will no longer diffuse, and the austenite will directly transform into a carbon-containing supersaturated α solid solution, called martensite. . Due to the supersaturated carbon content, the strength and hardness of martensite increase, the plasticity decreases, and the brittleness increases.
The corrosion resistance of stainless steel mainly comes from chromium. Experiments have proven that the corrosion resistance of steel will be greatly improved only when the chromium content exceeds 12%. Therefore, the chromium content in stainless steel is generally not less than 12%. Due to the increase in chromium content, it also has a great impact on the structure of steel. When the chromium content is high and the carbon content is small, chromium will balance the iron and carbon, and the Υ phase area in the picture will shrink or even disappear. This kind of stainless steel is iron It has a solid structure and does not undergo phase change when heated, so it is called ferritic stainless steel.
When the chromium content is low (but higher than 12%) and the carbon content is high, the alloy can easily form martensite when cooled from high temperature, so this type of steel is called martensitic stainless steel.
Nickel can expand the Υ phase zone and make the steel have an austenitic structure. If the nickel content is sufficient to make the steel have an austenitic structure at room temperature, the steel is called austenitic stainless steel.
4. Approximate comparison of commonly used stainless steel grades in my country and Japan

2 . The brand name is followed by NO. 1 means heat treatment, pickling or similar treatment after hot rolling; NO. 2 means heat treatment, pickling or corresponding treatment after cold rolling; NO. 2B means heat treatment, pickling or similar treatment after cold rolling, and finally cold rolling to obtain a suitable finish. Such as 304NO. 1 Stainless steel plate refers to hot-rolled stainless steel plate with grade 304. Another example is 321-2B, which represents the cold-rolled stainless steel plate with grade 321. The surface requires heat treatment, pickling or similar treatment after cold rolling, and finally cold rolling to obtain an appropriate smoothness.
5. Application of stainless steel in various fields
1 . In about 40 years from 1960 to 1999, the stainless steel production in Western countries soared from 2.15 million tons to 17.28 million tons, an increase of about 8 times, with an average annual growth rate of about 5. 5%. Stainless steel is mainly used in kitchens, home appliances, transportation, construction, and civil engineering fields. In terms of kitchen appliances, they mainly include washing sinks and electric and gas water heaters. Home appliances mainly include drums for fully automatic washing machines. From the viewpoint of environmental protection such as energy conservation and recycling, the demand for stainless steel is expected to further expand.
In the field of transportation, there are mainly exhaust systems for railway vehicles and automobiles. The stainless steel used in the exhaust system is about 20-30kg in each vehicle. The annual demand around the world is about 1 million tons. This is the largest application field of stainless steel.
In the field of construction, there has been a sharp increase in demand recently, such as the protective devices of Singapore MRT stations, which used about 5,000 tons of stainless steel exterior decorative materials. Another example is Japan. After 1980, the stainless steel used in the construction industry increased by about 4 times, and is mainly used as roofs, interior and exterior decoration of buildings, and structural materials. In the 1980s, type 304 unpainted materials were used as roofing materials in coastal areas of Japan. From rust prevention considerations, there was a gradual shift to the use of painted stainless steel. In the 1990s, ferritic stainless steel containing more than 20% high Cr with high corrosion resistance was developed and used as roofing materials, and various surface finishing technologies were developed for aesthetics.
In the civil engineering field, Japanese dam water absorption towers use stainless steel. In cold areas of Europe and America, salt needs to be spread to prevent highways and bridges from freezing, which accelerates the corrosion of steel bars, so stainless steel bars are used. In North America’s roads, stainless steel steel bars have been used in about 40 places in the past three years, each using 200-1,000 tons. In the future, stainless steel will make a difference in the market in this field.
2 . The key to expanding the application of stainless steel in the future is environmental protection, long life and the popularity of IT.
Regarding environmental protection, first of all, from the perspective of atmospheric environmental protection, the demand for heat-resistant and high-temperature corrosion-resistant stainless steel used in high-temperature garbage incineration equipment that suppresses the generation of dioxin, LNG power generation equipment, and high-efficiency power generation equipment using coal will expand. It is also estimated that the battery cases of fuel cell vehicles that will be put into practical use at the beginning of the 21st century will also use stainless steel. From the perspective of water quality and environmental protection, stainless steel with excellent corrosion resistance will also expand demand in water supply and drainage treatment equipment.
Regarding long life, the application of stainless steel is increasing in existing bridges, highways, tunnels and other facilities in Europe, and it is expected that this trend will spread throughout the world. Also, the lifespan of general residential buildings in Japan is particularly short at 20-30 years, making waste material disposal a major problem. With the recent emergence of buildings aiming to have a lifespan of 100 years, the demand for materials with excellent durability will grow. From the perspective of global environmental protection, while long life can reduce civil engineering and construction waste, it is necessary to explore how to reduce maintenance costs from the design stage where new concepts are introduced.
Regarding the popularization of IT, in the development and popularization process of IT, functional materials play a big role in equipment hardware, and the requirements for high-precision and high-functional materials are very high. For example, in mobile phone and microcomputer components, the high strength, elasticity and non-magnetic properties of stainless steel are flexibly used, which expands the application of stainless steel. Stainless steel with good cleanliness and durability plays an important role in manufacturing equipment for semiconductors and various substrates.
Stainless steel has a variety of excellent properties that other metals do not have. It is a material with excellent durability and recyclability. In the future, stainless steel will be widely used in various fields in response to the changes of the times.